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Carbapenemase-producing Enterobacterales (CPE) infection control practices are based on the paradigm that detected carriers in the hospital transmit to other patients who stay in the same ward. The role of plasmid-mediated transmission at population level remains largely unknown. In this retrospective cohort study over 4.7 years involving all multi-disciplinary public hospitals in Singapore, we analysed 779 patients who acquired CPE (1215 CPE isolates) detected by clinical or surveillance cultures. 42.0% met putative clonal transmission criteria, 44.8% met putative plasmid-mediated transmission criteria and 13.2% were unlinked. Only putative clonal transmissions associated with direct ward contact decreased in the second half of the study. Both putative clonal and plasmid-mediated transmission associated with indirect (no temporal overlap in patients' admission period) ward and hospital contact did not decrease during the study period. Indirect ward and hospital contact were identified as independent risk factors associated with clonal transmission. In conclusion, undetected CPE reservoirs continue to evade hospital infection prevention measures. New measures are needed to address plasmid-mediated transmission, which accounted for 50% of CPE dissemination. Carbapenemase-producing Enterobacterales cause healthcare-associated infections but modes of transmission are not well understood. Here, the authors find evidence of transmission without direct patient contact, indicating presence of undetected environmental reservoirs, whilst half of the transmission events are likely due to plasmid-mediated transmission. [ABSTRACT FROM AUTHOR]

Objectives: The increasing incidence of carbapenem-nonsusceptible Enterobacterales as major pathogens in healthcare associated infections (HAIs) is of paramount concern. To implement effective prevention strategies against carbapenem-nonsusceptible Enterobacterales (CnSE) HAIs, it is crucial to identify modifiable factors associated with these infections. We identified risk factors for CnSE-HAIs, and compared clinical outcomes of CnSE-HAI and carbapenem-sensitive Enterobacterales (CSE)-HAI patients. Methods: We conducted a multi-centre parallel matched case-control study in two 1700-bedded Singapore acute-care hospitals from 2014–2016. Patients with CnSE-HAIs and CSE-HAIs were compared to a common control group without HAIs (1:1:3 ratio), matched by time-at-risk and patient ward. Carbapenem nonsusceptible was defined as non-susceptibility to either meropenem or imipenem. Presence of healthcare associated infections were defined by the criteria provided by the European Centre for Disease Prevention and Control. Outcomes of CnSE-HAI and CSE-HAI patients were compared using multivariable logistic and cox regression; the models were adjusted for infection and treatment characteristics. Results: Eighty CnSE-HAI and 80 CSE-HAI patients were matched to 240 patients without HAIs. All CRE-HAIs patients had prior antibiotic exposure, with 44 (55.0%) with prior carbapenem exposure. The most common CnSE-HAIs were intra-abdominal infections (28.8%) and pneumonia (23.8%). The most common CnSE species was Klebsiella spp. (63.8%). In the risk factor analysis, presence of drainage devices [adjusted odds ratio (aOR), 2.19; 95% CI, 1.29 – 3.70] and prior carbapenem exposure (aOR,17.09; 95% CI, 3.06 – 95.43) independently predicted CnSE-HAIs. In the crude outcomes analysis, CnSE-HAI patients had higher all-cause in-hospital mortality and longer time to discharge compared to CSE-HAI patients. After adjusting for differences in receipt of antibiotics with reported susceptibility to the Enterobacterales, there was no significant difference in all-cause in-hospital mortality between the two groups (aOR, 1.76; 95% CI, 0.86–3.58). Time to discharge remained significantly longer in patients with CnSE-HAI (adjusted hazard ratio, 0.71; 95% CI, 0.51 – 0.98) after adjusting for disease severity, receipt of antibiotics with reported susceptibility and receipt of appropriate source control. Conclusion: Appropriate management of deep-seated Enterobacterales infections and reducing exposure to carbapenems may reduce risk of CnSE-HAIs in Singapore. Efforts to improve antimicrobial therapy in CnSE-HAI patients may improve patient outcomes. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) causes 20 million infections worldwide yearly, of which only about 3.3 million are symptomatic. In developed Asian countries, HEV strains detected in human sera and in food sources were genetically similar, suggesting that indigenous HEV infections may be largely food‐borne. To assess the burden of hepatitis E in Singapore, we performed a seroepidemiologic study of the infection. Additionally, we carried out HEV genotyping on archived, residual HEV IgM‐positive serum samples collected between 2014 and 2016 (n = 449), and on pig liver samples (n = 36) purchased from wet markets and supermarkets. Our study shows a rise in hepatitis E incidence (IgM) from 1.7 to 4.1 cases per 100,000 resident population from 2012 to 2016 and an increase in hepatitis E IgG positivity rate among residents from 14% in 2007 to 35% in 2016. Other findings also suggest the epidemiology of hepatitis E in Singapore has shifted, from it being mainly a disease imported from the Indian subcontinent, to one that is now increasingly prevalent in our resident population. Genotypes obtained from 143 human samples identified the majority to be genotype 3 (n = 121), 21 to be genotype 1 and one to be genotype 4. Further phylogenetic analyses suggest genotype 3a to be the cause of indigenous infections in residents, which showed genetic similarity to the genotype 3a strains detected in pig livers. This link between the strains in the majority of human samples and those in pig livers consumed by the public suggests a possible food‐borne route of HEV infection in Singapore. [ABSTRACT FROM AUTHOR]

Background: In 2015, Singapore had the first and only reported foodborne outbreak of invasive disease caused by the group B Streptococcus (GBS; Streptococcus agalactiae). Disease, predominantly septic arthritis and meningitis, was associated with sequence type (ST)283, acquired from eating raw farmed freshwater fish. Although GBS sepsis is well-described in neonates and older adults with co-morbidities, this outbreak affected non-pregnant and younger adults with fewer co-morbidities, suggesting greater virulence. Before 2015 ST283 had only been reported from twenty humans in Hong Kong and two in France, and from one fish in Thailand. We hypothesised that ST283 was causing region-wide infection in Southeast Asia. Methodology/Principal findings: We performed a literature review, whole genome sequencing on 145 GBS isolates collected from six Southeast Asian countries, and phylogenetic analysis on 7,468 GBS sequences including 227 variants of ST283 from humans and animals. Although almost absent outside Asia, ST283 was found in all invasive Asian collections analysed, from 1995 to 2017. It accounted for 29/38 (76%) human isolates in Lao PDR, 102/139 (73%) in Thailand, 4/13 (31%) in Vietnam, and 167/739 (23%) in Singapore. ST283 and its variants were found in 62/62 (100%) tilapia from 14 outbreak sites in Malaysia and Vietnam, in seven fish species in Singapore markets, and a diseased frog in China. Conclusions: GBS ST283 is widespread in Southeast Asia, where it accounts for a large proportion of bacteraemic GBS, and causes disease and economic loss in aquaculture. If human ST283 is fishborne, as in the Singapore outbreak, then GBS sepsis in Thailand and Lao PDR is predominantly a foodborne disease. However, whether transmission is from aquaculture to humans, or vice versa, or involves an unidentified reservoir remains unknown. Creation of cross-border collaborations in human and animal health are needed to complete the epidemiological picture. [ABSTRACT FROM AUTHOR]

Objectives: Owing to gene transposition and plasmid conjugation, New Delhi metallo-β-lactamase (NDM) is typically identified among varied Enterobacteriaceae species and STs. We used WGS to characterize the chromosomal and plasmid molecular epidemiology of NDM transmission involving four institutions in Singapore.Methods: Thirty-three Enterobacteriaceae isolates (collection years 2010-14) were sequenced using short-read sequencing-by-synthesis and analysed. Long-read single molecule, real-time sequencing (SMRTS) was used to characterize genetically a novel plasmid pSg1-NDM carried on Klebsiella pneumoniae ST147.Results: In 20 (61%) isolates, blaNDM was located on the pNDM-ECS01 plasmid in the background of multiple bacterial STs, including eight K. pneumoniae STs and five Escherichia coli STs. In six (18%) isolates, a novel blaNDM-positive plasmid, pSg1-NDM, was found only in K. pneumoniae ST147. The pSg1-NDM-K. pneumoniae ST147 clone (Sg1-NDM) was fully sequenced using SMRTS. pSg1-NDM, a 90 103 bp IncR plasmid, carried genes responsible for resistance to six classes of antimicrobials. A large portion of pSg1-NDM had no significant homology to any known plasmids in GenBank. pSg1-NDM had no conjugative transfer region. Combined chromosomal-plasmid phylogenetic analysis revealed five clusters of clonal bacterial NDM-positive plasmid transmission, of which two were inter-institution clusters. The largest inter-institution cluster involved six K. pneumoniae ST147-pSg1-NDM isolates. Fifteen patients were involved in transmission clusters, of which four had ward contact, six had hospital contact and five had an unknown transmission link.Conclusions: A combined sequencing-by-synthesis and SMRTS approach can determine effectively the transmission clusters of blaNDM and genetically characterize novel plasmids. Plasmid molecular epidemiology is important to understanding NDM spread as blaNDM-positive plasmids can conjugate extensively across species and STs. [ABSTRACT FROM AUTHOR]

Background: Acinetobacter baumannii is an important nosocomial pathogen that has become increasingly resistant to multiple antibiotics. Genetic manipulation of MDR A. baumannii is useful especially for defining the contribution of each active efflux mechanism in multidrug resistance. Existing methods rely on the use of an antibiotic selection marker and are not suited for multiple gene deletions. Results: A tellurite-resistant (sacB+, xylE+) suicide vector, pMo130-TelR, was created for deleting the adeFGH and adeIJK operons in two clinical MDR A. baumannii, DB and R2 from Singapore. Using a two-step selection, plasmid insertion recombinants (first-crossover) were selected for tellurite resistance and the deletion mutants (secondcrossover) were then selected for loss of sacB. The DNA deletions were verified by PCR while loss of gene expression in the ΔadeFGH, ΔadeIJK and ΔadeFGHΔadeIJK deletion mutants was confirmed using qRT-PCR. The contribution of AdeFGH and AdeIJK pumps to MDR was defined by comparing antimicrobial susceptibilities of the isogenic mutants and the parental strains. The deletion of adeIJK produced no more than eight-fold increase in susceptibility to nalidixic acid, tetracycline, minocycline, tigecycline, clindamycin, trimethoprim and chloramphenicol, while the deletion of adeL-adeFGH operon alone had no impact on antimicrobial susceptibility. Dye accumulation assays using H33342 revealed increased dye retention in all deletion mutants, except for the R2ΔadeFGH mutant, where a decrease was observed. Increased accumulation of ethidium bromide was observed in the parental strains and all pump deletion mutants in the presence of efflux inhibitors. The efflux pump deletion mutants in this study revealed that only the AdeIJK, but not the AdeFGH RND pump, contributes to antimicrobial resistance and dye accumulation in MDR A. baumannii DB and R2. Conclusions: The marker-less gene deletion method using pMo130-TelR is applicable for creating single and multiple gene deletions in MDR A. baumannii. The adeFGH and adeIJK operons were successfully deleted separately and together using this method and the impact of each efflux pump on antimicrobial resistance could be defined clearly. [ABSTRACT FROM AUTHOR]

A new national antimicrobial resistance surveillance program in Singapore public hospitals that uses WHONET detected high levels of methicillin resistance among Staphylococcus aureus (35.3%), carbapenem resistance among Acinetobacter spp. (49.6%), and third-generation cephalosporin resistance among Klebsiella pneumoniae (35.9%) hospital isolates in 2006. Antimicrobial drug resistance is a major problem in Singapore. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the emergence of zoonotic streptococcus canis infections in Singapore.

• ERG11 mutations in Candida auris (C. auris) are clade-specific. • 42.9% of C. auris isolated in Singapore is multidrug-resistant. • The updated VITEKⓇ2 System has limited abilities for identifying C. auris. • Genomic data must be correlated with epidemiological information. Candida auris (C. auris) has globally emerged as a multidrug-resistant pathogen. While it is known that there are four geographic clades, little is known about its genomic epidemiology in the Southeast Asian region. Laboratory identification can be challenging but the VITEKⓇ2 system (version 8.01 software) has recently updated its database to include C. auris. This study aimed to investigate the genomic epidemiology of C. auris isolated in Singapore and the susceptibility profiles in relation to ERG11 and FKS1 mutations. Seven C. auris isolates from 2012–2018 were analysed using whole-genome sequencing, and antifungal susceptibility testing was performed. The performance of the updated VITEKⓇ2 system in identifying C. auris was also evaluated using these C. auris strains together with five closely related Candida species. Three clades were identified: South Asian (71.4%), South American (14.3%) and East Asian (14.3%). Local transmission was unlikely as there was no obviously identified cluster and most cases were likely to be imported at different time points following overseas hospitalisation exposure. Three isolates (42.9%) were multidrug-resistant. All South Asian strains were resistant to fluconazole and harboured ERG11 mutations, which were clade-specific. No FKS1 mutation was detected. The VITEKⓇ2 system was able to correctly identify most of the South Asian C. auris strains but misidentified the East Asian strain and gave a low discrimination result for the South American clade. This study showed that the introduction of C. auris into Singapore was possibly over multiple episodes and from different sources. The VITEKⓇ2 System version 8.01 software has limited abilities in identifying C.auris. [ABSTRACT FROM AUTHOR]

One of the most important resistance mechanisms in Gram-negative bacteria today is the production of enzymes causing resistance to cephalosporin and carbapenem antibiotics. The spread of extended-spectrum β-lactamases (ESBL)- and carbapenemase- producing Gram-negative bacteria is an emerging global public health problem. The aim of the present study was to (i) assess the prevalence of carbapenem-resistant bacteria (CRB) and ESBL-producing strains in sewage effluents from two major hospitals in Singapore, (ii) characterize the isolated strains and (iii) identify some of the ESBL and carbapenemase genes responsible for the resistance. CHROMagar ESBL and KPC plates were used to rapidly screen for ESBL-producing bacteria and those expressing reduced susceptibility to carbapenems, respectively. The abundance of ESBL-producers and CRB in hospital wastewater ranged between 10 3 and 10 6 CFU/mL. Out of the 66 isolates picked from ESBL and KPC plates, 95%, 82%, 82% and 76% were resistant to ceftriaxone, ceftazidime (3rd generation cephalosporin family), ertapenem and meropenem (carbapenem family), respectively. Among the resistant isolates, the most predominant taxa identified were Pseudomonas spp. (28.2%), Klebsiella spp. (28.2%), Enterobacter spp. (18.3%) and Citrobacter spp. (11.3%). PCR and sequencing analysis showed that the predominant β-lactamase genes were bla SHV (41.1%) followed by bla NDM-1 (35.6%), bla CTX (35.6%) and bla KPC (28.8%). The results of this study show a high prevalence of bacteria resistant to modern extended-spectrum cephalosporins and carbapenems and the presence of ESBL- and carbapenemase producers in hospital effluents. These findings support the need to improve management of hospital wastewater in order to minimize the spread of antimicrobial resistant microorganisms from this source. [ABSTRACT FROM AUTHOR]

Background: The emerging fungal pathogen Candida auris poses a serious threat to global public health due to its worldwide distribution, multidrug resistance, high transmissibility, propensity to cause outbreaks, and high mortality. We aimed to characterise three unusual C auris isolates detected in Singapore, and to determine whether they constitute a novel clade distinct from all previously known C auris clades (I-V)., Methods: In this genotypic and phenotypic study, we characterised three C auris clinical isolates, which were cultured from epidemiologically unlinked inpatients at a large tertiary hospital in Singapore. The index isolate was detected in April, 2023. We performed whole-genome sequencing (WGS) and obtained hybrid assemblies of these C auris isolates. The complete genomes were compared with representative genomes of all known C auris clades. To provide a global context, 3651 international WGS data from the National Center for Biotechnology Information (NCBI) database were included in a high-resolution single nucleotide polymorphism (SNP) analysis. Antifungal susceptibility testing was done and antifungal resistance genes, mating-type locus, and chromosomal rearrangements were characterised from the WGS data of the three investigated isolates. We further implemented Bayesian logistic regression models to classify isolates into known clades and simulate the automatic detection of isolates belonging to novel clades as their WGS data became available., Findings: The three investigated isolates were separated by at least 37 000 SNPs (range 37 000-236 900) from all existing C auris clades. These isolates had opposite mating-type allele and different chromosomal rearrangements when compared with their closest clade IV relatives. The isolates were susceptible to all tested antifungals. Therefore, we propose that these isolates represent a new clade of C auris, clade VI. Furthermore, an independent WGS dataset from Bangladesh, accessed via the NCBI Sequence Read Archive, was found to belong to this new clade. As a proof-of-concept, our Bayesian logistic regression model was able to flag these outlier genomes as a potential new clade., Interpretation: The discovery of a new C auris clade in Singapore and Bangladesh in the Indomalayan zone, showing a close relationship to clade IV members most commonly found in South America, highlights the unknown genetic diversity and origin of C auris, particularly in under-resourced regions. Active surveillance in clinical settings, along with effective sequencing strategies and downstream analysis, will be essential in the identification of novel strains, tracking of transmission, and containment of adverse clinical effects of C auris infections., Funding: Duke-NUS Academic Medical Center Nurturing Clinician Researcher Scheme, and the Genedant-GIS Innovation Program., Competing Interests: Declaration of interests BHT declares that he serves on the advisory boards for Pfizer (for respiratory syncytial virus vaccine) and MSD (for letermovir). ALT declares that she serves on the Chapter of Pathologists, Singapore. She also received an honorarium (to her institution) for a lecture delivered to the Singapore Association of Pharmaceutical Industries. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a global public health threat. In this study, we employed whole-genome sequencing (WGS) to determine the genomic epidemiology of a longitudinal collection of clinical CRKP isolates recovered from a large public acute care hospital in Singapore. Phylogenetic analyses, a characterization of resistance and virulence determinants, and plasmid profiling were performed for 575 unique CRKP isolates collected between 2009 and 2020. The phylogenetic analyses identified the presence of global high-risk clones among the CRKP population (clonal group [CG] 14/15, CG17/20, CG147, CG258, and sequence type [ST] 231), and these clones constituted 50% of the isolates. Carbapenemase production was common ( n  = 497, 86.4%), and KPC was the predominant carbapenemase ( n  = 235, 40.9%), followed by OXA-48-like ( n  = 128, 22.3%) and NDM ( n  = 93, 16.2%). Hypervirulence was detected in 59 (10.3%) isolates and was most common in the ST231 carbapenemase-producing isolates (21/59, 35.6%). Carbapenemase genes were associated with diverse plasmid replicons; however, there was an association of bla with ColKP3 plasmids. This study presents the complex and diverse epidemiology of the CRKP strains circulating in Singapore. Our study highlights the utility of WGS-based genomic surveillance in tracking the population dynamics of CRKP. OXA-181/232 In this study, we characterized carbapenem-resistant Klebsiella pneumoniae clinical isolates collected over a 12-year period in the largest public acute-care hospital in Singapore using whole-genome sequencing. The results of this study demonstrate significant genomic diversity with the presence of well-known epidemic, multidrug-resistant clones amid a diverse pool of nonepidemic lineages. Genomic surveillance involving comprehensive resistance, virulence, and plasmid gene content profiling provided critical information for antimicrobial resistance monitoring and highlighted future surveillance priorities, such as the emergence of ST231 K. pneumoniae strains bearing multidrug resistance, virulence elements, and the potential plasmid-mediated transmission of the IMPORTANCE In this study, we characterized carbapenem-resistant Klebsiella pneumoniae clinical isolates collected over a 12-year period in the largest public acute-care hospital in Singapore using whole-genome sequencing. The results of this study demonstrate significant genomic diversity with the presence of well-known epidemic, multidrug-resistant clones amid a diverse pool of nonepidemic lineages. Genomic surveillance involving comprehensive resistance, virulence, and plasmid gene content profiling provided critical information for antimicrobial resistance monitoring and highlighted future surveillance priorities, such as the emergence of ST231 K. pneumoniae strains bearing multidrug resistance, virulence elements, and the potential plasmid-mediated transmission of the bla OXA-48-like gene. The findings here also reinforce the necessity of unique infection control and prevention strategies that take the genomic diversity of local circulating strains into consideration.

Salmonella Enteritidis is a major foodborne pathogen worldwide. In this study, a total of 276 S. enteritidis isolates, collected between 2016 and 2017 from human, food and farm/slaughterhouse samples, were studied to enhance the understanding of the epidemiology of human salmonellosis in Singapore. Results showed all 276 isolates belonged either to ST1925 (70.3%) or ST11 (29.7%), with ST11 being significantly more frequent in extra-intestinal isolates and chicken isolates. Food isolates, most of which were from poultry, showed the highest prevalence of resistance (33-37%) against beta-lactams or beta-lactams/beta-lactamase inhibitor combination (ampicillin, piperacillin and ampicillin/sulbactam). The analysis showed the detection of genes associated with resistance to aminoglycoside genes (99.6%), tetracycline (55.1%), and beta-lactams (14.9%) of all isolates. Nine types of plasmids were found in 266 isolates; the most common incompatibility group profiles were IncFIB(S)-IncFII(S)-IncX1 (72.2%) and IncFIB(S)-IncFII(S) (15.8%). Most plasmid harbouring isolates from chicken (63.6%, 14/22) and from human (73.8%, 175/237) shared the same plasmid profile (IncFIB(S)-IncFII(S)-IncX1). SNP analysis showed clustering of several isolates from poultry food products and human isolates, suggesting phylogenetic relatedness among these isolates. Lastly, this study provides important epidemiological insights on the application of phenotypic and next-generation sequencing (NGS) tools for improved food safety and public health surveillance and outbreak investigation of S. enteritidis .

Pseudomonas aeruginosa is a clinically important pathogen implicated in many hospital-acquired infections. Its propensity to acquire broad-spectrum resistance has earned the organism its status as a severe public health threat requiring urgent control measures. While whole-genome sequencing-based genomic surveillance provides a means to track antimicrobial resistance, its use in molecular epidemiological surveys of P. aeruginosa remains limited, especially in the Southeast Asian region. We sequenced the whole genomes of 222 carbapenem-non-susceptible P. aeruginosa (CNPA) isolates collected in 2006-2020 at the largest public acute care hospital in Singapore. Antimicrobial susceptibilities were determined using broth microdilution. Clonal relatedness, multi-locus sequence types, and antimicrobial resistance determinants (acquired and chromosomal) were determined. In this study, CNPA exhibited broad-spectrum resistance (87.8% multi-drug resistance), retaining susceptibility only to polymyxin B (95.0%) and amikacin (55.0%). Carbapenemases were detected in 51.4% of the isolates, where IMP and NDM metallo- β -lactamases were the most frequent. Carbapenem resistance was also likely associated with OprD alterations or efflux mechanisms (ArmZ/NalD mutations), which occurred in strains with or without carbapenemases. The population of CNPA in the hospital was diverse; the 222 isolates grouped into 68 sequence types (ST), which included various high-risk clones. We detected an emerging clone, the NDM-1-producing ST308, in addition to the global high-risk ST235 clone which was the predominant clone in our population. Our results thus provide a "snapshot" of the circulating lineages of CNPA locally and the prevailing genetic mechanisms contributing to carbapenem resistance. This database also serves as the baseline for future prospective surveillance studies.

Background: Klebsiella pneumoniae liver abscess (KLA) is emerging worldwide due to hypermucoviscous strains with a propensity for metastatic infection. Treatment includes drainage and prolonged intravenous antibiotics. We aimed to determine whether oral antibiotics were noninferior to continued intravenous antibiotics for KLA., Methods: This noninferiority, parallel group, randomized, clinical trial recruited hospitalized adults with liver abscess and K. pneumoniae isolated from blood or abscess fluid who had received ≤7 days of effective antibiotics at 3 sites in Singapore. Patients were randomized 1:1 to oral (ciprofloxacin) or intravenous (ceftriaxone) antibiotics for 28 days. If day 28 clinical response criteria were not met, further oral antibiotics were prescribed until clinical response was met. The primary endpoint was clinical cure assessed at week 12 and included a composite of absence of fever in the preceding week, C-reactive protein <20 mg/L, and reduction in abscess size. A noninferiority margin of 12% was used., Results: Between November 2013 and October 2017, 152 patients (mean age, 58.7 years; 25.7% women) were recruited, following a median 5 days of effective intravenous antibiotics. A total of 106 (69.7%) underwent abscess drainage; 71/74 (95.9%) randomized to oral antibiotics met the primary endpoint compared with 72/78 (92.3%) randomized to intravenous antibiotics (risk difference, 3.6%; 2-sided 95% confidence interval, -4.9% to 12.8%). Effects were consistent in the per-protocol population. Nonfatal serious adverse events occurred in 12/72 (16.7%) in the oral group and 13/77 (16.9%) in the intravenous group., Conclusions: Oral antibiotics were noninferior to intravenous antibiotics for the early treatment of KLA., Clinical Trials Registration: NCT01723150., (© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

The bla IMI gene is rarely detected outside the Enterobacter genus. Genomic characterization of 87 bla IMI -positive Enterobacter cloacae complex members revealed that the largest phylogenomic clade was made up of E. cloacae subsp. cloacae (71.3%), followed by the newly described species E. bugandensis (13.8%), E. sichuanensis (10.3%), and E. roggenkampii (4.6%). IMI-1 was the predominant carbapenemase variant (86/87, 98.9%). All the bla IMI genes were associated with chromosomally integrated Xer-dependent integrative mobile elements (IMEXs), with two new variants detected., (Copyright © 2020 American Society for Microbiology.)

The convergence of carbapenem-resistance and hypervirulence genes in Klebsiella pneumoniae has led to the emergence of highly drug-resistant superbugs capable of causing invasive disease. We analyzed 556 carbapenem-resistant K. pneumoniae isolates from patients in Singapore hospitals during 2010-2015 and discovered 18 isolates from 7 patients also harbored hypervirulence features. All isolates contained a closely related plasmid (pKPC2) harboring bla KPC-2 , a K. pneumoniae carbapenemase gene, and had a hypervirulent background of capsular serotypes K1, K2, and K20. In total, 5 of 7 first patient isolates were hypermucoviscous, and 6 were virulent in mice. The pKPC2 was highly transmissible and remarkably stable, maintained in bacteria within a patient with few changes for months in the absence of antimicrobial drug selection pressure. Intrapatient isolates were also able to acquire additional antimicrobial drug resistance genes when inside human bodies. Our results highlight the potential spread of carbapenem-resistant hypervirulent K. pneumoniae in Singapore.

Non-typhoidal salmonellosis is a leading cause of foodborne zoonosis. To better understand the epidemiology of human salmonellosis, this study aimed to determine the prevalence, antimicrobial resistance and sequence types of Salmonella in retail food and wild birds (proximity to humans) in Singapore. We analyzed 21,428 cooked and ready-to-eat food and 1,510 residual faecal samples of wild birds collected during 2010-2015. Thirty-two Salmonella isolates from food and wild birds were subjected to disc diffusion and multi-locus sequence typing (MLST). Salmonella was isolated from 0.08% (17/21,428) of food and 0.99% (15/1510) of wild birds. None of the isolates from wild birds ( n = 15) exhibited phenotypic resistance, while the isolates from food (47.1%, 8/17) showed a high prevalence of phenotypic resistance to, at least, one antimicrobial. These findings suggested that the avian Salmonell a isolates had been subjected to less antimicrobial selection pressure than those from food samples. MLST revealed specific sequence types found in both food and wild birds. The study can guide future studies with whole-genome analysis on a larger number of isolates from various sectors for public health measures., Competing Interests: The authors declare no conflict of interest.

Increasing resistance to polymyxin, a last-line antibiotic, is a growing public health concern worldwide. The primary objective of this study was to identify predictors for the isolation of polymyxin-resistant (PR) carbapenem-resistant Enterobacteriaceae (CRE) among hospitalized patients. The secondary objective was to describe the clinical outcomes of patients with PR-CRE infections. A retrospective case-control study including patients admitted to Singapore General Hospital between June 2012 and June 2016 was conducted. Cases were defined as patients who had clinical cultures from which a PR-CRE was isolated. Controls were randomly selected from patients with polymyxin-susceptible (PS) CRE admitted during the same period, and frequency-matched to site of isolation. We included 37 PR cases and 111 PS controls. Polymyxin resistance was detected predominantly in Enterobacter spp. (54.1%) and Klebsiella pneumoniae (43.2%). Multilocus sequence typing showed little clonal relatedness among the isolates. mcr-1 was detected in two PR-CRE isolates. Multivariable analyses showed that PR-CRE isolation was associated with prior polymyxins (adjusted odds ratio (OR), 21.31; 95% confidence interval (CI), 3.04-150.96) and carbapenem exposures (OR 3.74; CI 1.13-12.44), when adjusted for time at risk and bacteria species. In PR-CRE patients with infections, the 30-day all-cause in-hospital mortality was 50.0% as compared to 38.1% in patients with PS-CRE (P = 0.346). Prior polymyxin and carbapenem exposures were independent risk factors for isolation of PR-CRE. Outcomes of PR-CRE and PS-CRE infections were similar in this study., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Bacteria encoding the New Delhi metallo-β-lactamase gene (blaNDM-1) are regarded as superbugs for their resistance to multiple antibiotics. Plasmids encoding blaNDM-1 have been observed to be spreading among gram-negative bacteria around the world. Previous studies have demonstrated that multiple modifications of blaNDM-1-harboring plasmids might contribute to the spread of the gene. In this study, we analyzed blaNDM-1-encoding plasmids from two Klebsiella pneumoniae isolates, DU7433 and DU1301, found to be unrelated by pulsed field gel electrophoresis and multilocus sequencing typing (DU7433: ST14 and DU1301: ST11), and compared them with previously published plasmids. Although strains DU1301, DU7433, and previously published strain DU43320 carried unrelated plasmids, their transconjugants exhibited similar antimicrobial resistance profiles. Transconjugants lacked the resistance to aztreonam, ciprofloxacin, gentamicin, tetracycline, and trimethoprim/sulfamethoxazole when compared with the corresponding clinical isolates. Plasmids pTR1 from DU1301 and pTR2 from DU7433 had completely different plasmid backbones except a short conserved region of blaNDM-1 and ble flanked with truncated or nontruncated ISAba125 and trpF. The presence of this common region among known blaNDM-1-carrying plasmids implies that the dissemination of blaNDM-1 may be facilitated by mobilization of this conserved immediate region among different plasmids. Control measures should be strictly enforced whenever increasing incidences of epidemiological unrelated strains were identified.

Background: In the past decade, several countries have seen gradual replacement of endemic multi-resistant healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) with clones that are more susceptible to antibiotic treatment. One example is Singapore, where MRSA ST239, the dominant clone since molecular profiling of MRSA began in the mid-1980s, has been replaced by ST22 isolates belonging to EMRSA-15, a recently emerged pandemic lineage originating from Europe., Results: We investigated the population structure of MRSA in Singaporean hospitals spanning three decades, using whole genome sequencing. Applying Bayesian phylogenetic methods we report that prior to the introduction of ST22, the ST239 MRSA population in Singapore originated from multiple introductions from the surrounding region; it was frequently transferred within the healthcare system resulting in a heterogeneous hospital population. Following the introduction of ST22 around the beginning of the millennium, this clone spread rapidly through Singaporean hospitals, supplanting the endemic ST239 population. Coalescent analysis revealed that although the genetic diversity of ST239 initially decreased as ST22 became more dominant, from 2007 onwards the genetic diversity of ST239 began to increase once more, which was not associated with the emergence of a sub-clone of ST239. Comparative genomic analysis of the accessory genome of the extant ST239 population identified that the Arginine Catabolic Mobile Element arose multiple times, thereby introducing genes associated with enhanced skin colonization into this population., Conclusions: Our results clearly demonstrate that, alongside clinical practice and antibiotic usage, competition between clones also has an important role in driving the evolution of nosocomial pathogen populations.

Aims: To characterise carbapenemase-producing Enterobacteriaceae (CRE) isolated in Singapore., Methods: Carbapenemase genes and their flanking regions were amplified and sequenced by PCR. Isolates were typed by pulsed-field gel electrophoresis and multi-locus sequence typing. Plasmids bearing carbapenemase genes were sized by S1 nuclease digestion, Southern blotting, and DNA hybridisation with appropriate probes. Transfer of these plasmids was attempted by conjugation and transformation. Successfully transferred plasmids were characterised by polymerase chain reaction (PCR) replicon typing and restriction digestion., Results: Isolates of Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae and Citrobacter species carried a variety of carbapenemase genes including blaIMP-1, blaIMP-4, blaNDM-1, blaNDM-7, blaOXA-181, blaOXA-48 and blaKPC-2. Apart from K. pneumoniae with blaOXA-181, and some K. pneumoniae with blaNDM-1, the other isolates were not clonal. However there appears to be some spread of plasmids with blaIMP-1, blaNDM-1,blaKPC-2, and blaOXA-48., Conclusions: The number of isolates of CRE has increased in Singapore, especially since 2010. There is a diversity of carbapenemase types that reflects the geographical proximity of other countries with CRE.

Background: Klebsiella pneumoniae is the major cause of liver abscesses in several Asian countries. Differences in the type of circulating Klebsiella strains and/or the genetic make up of the host seem to be plausible explanations for this., Methods: Two recent K. pneumoniae strains isolated from patients with liver abscess, one from Missouri in the US, and a second one from Singapore, were fully characterized by molecular typing, association of virulent genes, neutrophil phagocytosis, susceptibility to serum killing, and lethality in mice., Results: Both strains had mucoid colony morphology and were similar in multilocus sequence type (ST-163), drug-susceptibility profile, resistance to phagocytosis and susceptibility to serum killing. Although ST-163 is a single nucleotide variant (SNV) to the major ST-23, which is specific to serotype K1 K. pneumoniae that causes liver abscess in Taiwan, these two isolates differ in capsular serotype. One was serotype K1 and the other K29. Since a serotype K35 with ST163 was reported previously to cause peritonitis, serotype K29 with SNV to ST-23 was not impossible. Pulsed field gel electrophoresis by XbaI digestion showed different restriction patterns. The virulence-associated genes rmpA and aerobactin were only present in the serotype K1 isolate from Singapore and not in the serotype K29 isolate from Missouri. The serotype K1 isolate was also more virulent to mice., Conclusion: The reasons underlying the high prevalence of ST-23 or its SNV in K. pueumonaie liver abscesses is worth further investigation., (Copyright © 2011. Published by Elsevier B.V.)

Introduction: Vancomycin-resistant enterococci (VRE) have emerged as one of the major nosocomial antimicrobial-resistant pathogens globally. In this article, we describe the epidemiology of VRE in Singaporean public hospitals in the 5 years following the major local VRE outbreak in 2005., Materials and Methods: A passive laboratory surveillance programme identified non-duplicate VRE isolates from 7 hospitals from 2006 to 2010. Descriptive statistics and time-series analysis was performed on all clinical VRE isolates for each individual hospital as well as for the combined dataset., Results: There were a total of 418 VRE isolates over 5 years, of which 102 isolates (24.4%) were from clinical cultures. Between 0.4% and 0.7% of all clinical enterococcal isolates were resistant to vancomycin. The overall incidence-density of VRE did not change over time in Singapore despite 2 separate outbreaks in tertiary hospitals in 2009 and 2010. Incidence-density of clinical VRE cases fell in 2 secondary hospitals, while another 2 hospitals experienced no significant VRE infections after 2008., Conclusion: The prevalence of VRE clinical isolates remains low in Singaporean public sector hospitals. However, the presence of at least 2 outbreaks in separate hospitals over the past 5 years indicates the need for continued vigilance in order to prevent any further increase in VRE prevalence locally.

Background: Spread of the bla(NDM-1) gene that encodes the New Delhi metallo-β-lactamase (NDM-1) in Enterobacteriaceae is a major global health problem. Plasmids carrying bla(NDM-1) from two different multi-drug resistant Klebsiella pneumonia isolates collected in Singapore were completely sequenced and compared to known plasmids carrying bla(NDM-1)., Methodology/principal Findings: The two plasmids, pTR3 and pTR4, were transferred to Escherichia coli recipient strain J53 and completely sequenced by a shotgun approach using 3-kb paired-end libraries on 454. Although the K. pneumoniae strains were unrelated by molecular typing using PFGE and MLST, complete sequencing revealed that pTR3 and pTR4 are identical. The plasmid sequence is similar to the E. coli NDM-1-encoding plasmid p271A, which was isolated in Australia from a patient returning from Bangladesh. The immediate regions of the bla(NDM-1) gene in pTR3/4 are identical to that of p271A, but the backbone of our plasmid is much more similar to another IncN2 plasmid reported recently, pJIE137, which contained an additional 5.2-kb CUP (conserved upstream repeat) regulon region in comparison to p271A. A 257-bp element bounded by imperfect 39-bp inverted repeats (IR) and an incomplete version of this element flanking the 3.6-kb NDM-1-encoding region were identified in these plasmids and are likely to be the vestiges of an unknown IS., Conclusions: Although the hosts are not epidemiologically linked, we found that the plasmids bearing the bla(NDM-1) gene are identical. Comparative analyses of the conserved NDM-1-encoding region among different plasmids from K. pneumoniae and E. coli suggested that the transposable elements and the two unknown IR-associated elements flanking the NDM-1-encoding region might have aided the spreading of this worrisome resistance determinant.

Serotype K1 Klebsiella pneumoniae with multilocus sequence type 23 (ST23) has been strongly associated with liver abscess in Taiwan. Few data regarding the strain types and virulence of this serotype from other Asian countries are available. Serotype K1 K. pneumoniae strains isolated from liver abscess and stool samples from subjects hospitalized in Hong Kong, Singapore, and Taiwan hospitals were examined. Forty-seven serotype K1 isolates were identified: 26 from liver abscess samples and 21 from stool samples. MLST revealed 7 sequence types: 85.1% (40 of 47 isolates) belonged to ST23, 1 isolate belonged to ST163 (a single-locus variant of ST23), and 2 isolates were ST249 (a 3-locus variant of ST23). New STs, namely, ST367, ST425, and ST426, were allocated to 3 of 4 isolates from stool samples. The virulence of these strains was determined by neutrophil phagocytosis and mouse infection models. Except for two ST23 isolates, all Klebsiella pneumoniae isolates were resistant to phagocytosis. Resistance to serum killing varied in isolates of ST23, while all non-ST23 strains were susceptible to serum killing except one with ST249 from a liver abscess. All hypervirulent isolates with a 50% lethal dose of <10(2) CFU were from ST23, were resistant to phagocytosis and serum killing, and also carried both virulence-associated genes, rmpA and aerobactin. Multilocus sequence typing genotype 23 was the most prevalent sequence type among serotype K1 K. pneumoniae isolates from both liver abscess and stool samples in the Asia Pacific region. Serotype K1 K. pneumoniae isolates with capsule expression leading to phagocytic resistance and with the aerobactin gene were associated with hypervirulence.

We report what we believe to be the first six cases of daptomycin-non-susceptible Staphylococcus aureus infections from Singapore. These strains were rapidly isolated after bacteraemic patients were switched to daptomycin following initial prolonged unsuccessful therapy with vancomycin, despite confirmation of daptomycin susceptibility just prior to initiating daptomycin therapy. The majority of post-vancomycin therapy strains exhibited marked thickening of their cell walls on electron microscopic examination. In patients with persistent S. aureus bacteraemia, therapeutic failure with daptomycin may occur if used as salvage therapy following vancomycin failure, notwithstanding initial susceptibility testing results.

Nine imipenem-resistant Pseudomonas aeruginosa isolates were found to contain a variety of metallo-beta-lactamase genes, including bla(IMP-1), bla(IMP-7), bla(VIM-2), bla(VIM-6), and the novel bla(IMP-26). Multilocus sequence typing showed a diversity of sequence types. Comparison with isolates from an earlier study showed that the epidemic clones from 2000 have not become established.

A surveillance study was performed in four Singapore public hospitals from 2006 to 2008 to determine the correlation between antibiotic prescription and Gram-negative bacterial antimicrobial resistance. Targeted organisms included ceftriaxone- and ciprofloxacin-resistant Escherichia coli and Klebsiella pneumoniae, as well as imipenem-resistant Pseudomonas aeruginosa and Acinetobacter spp. Antibiotic prescription data were collated in the WHO anatomical therapeutic chemical (ATC)/defined daily dose (DDD) format, while antibiotic resistance was expressed as incidence density adjusted for total inpatient-days every quarter. Individual trends were determined by linear regression, while possible associations between antibiotic prescription and resistance were evaluated via cross-correlation analysis. Results over 3 years indicated significantly rising incidence densities of ceftriaxone- and ciprofloxacin-resistant E. coli and imipenem-resistant Acinetobacter spp. (blood isolates only). Antimicrobial-resistant Klebsiella pneumoniae rates declined. The prescription rates of piperacillin-tazobactam, ertapenem, meropenem, ciprofloxacin, and levofloxacin increased significantly, while imipenem and moxifloxacin prescription decreased. Cross-correlation analysis demonstrated possible associations between prescription of fluoroquinolones and ciprofloxacin-resistant E. coli (R(2) = 0.46), fluoroquinolones and ceftriaxone-resistant E. coli (R(2) = 0.47), and carbapenems and imipenem-resistant Acinetobacter spp. (R(2) = 0.48), all at zero time lag. Changes in meropenem prescription were associated with a similar trend in imipenem-resistant Acinetobacter blood isolates after a 3-month time lag. No correlation was found between cephalosporin use and resistance. In conclusion, our data demonstrated correlation between prescription of and Gram-negative bacterial resistance to several, but not all, key antimicrobial agents in Singapore hospitals. In areas where Gram-negative bacterial resistance is endemic and prescription of broad-spectrum antimicrobial agents is high, factors other than antimicrobial usage may be equally important in maintaining high resistance rates.

Introduction: At the time of the study, 3 plasmid-borne qnr determinants (qnrA, qnrB and qnrS) and 1 plasmid-borne aminoglycoside-modifying enzyme determinant that confers quinolone resistance (aac(6')-Ib-cr) had been described in the literature., Materials and Methods: We studied the prevalence of the 3 qnr determinants in a total of 117 nalidixic acid-resistant urinary isolates of Klebsiella pneumoniae (61 isolates) and Escherichia coli (56 isolates) using multiplex polymerase chain reaction (PCR). Further, a subset of the original strains (comprising 14 E. coli and 38 K. pneumoniae) showing reduced susceptibility to the aminoglycosides underwent PCR for aac(6')-Ib, followed by restriction digestion with BtsCI to detect the variant aac(6')-Ib-cr., Results: Twenty-eight of 61 (45.9%) Klebsiella isolates were found to possess at least 1 qnr determinant. Only 1/56 (1.8%) E. coli isolates were found to possess a qnr determinant. Two of the Klebsiella isolates possessed 2 qnr determinants each (qnrB and qnrS). The predominant determinant was qnrB (19 isolates). There were 11 isolates harbouring qnrS, and only 1 with qnrA. 1/14 (7.1%) E. coli and 35/38 K. pneumoniae (92.1%) were found to possess aac(6')-Ib-cr. There was pairwise association between each of qnr, aac(6')-Ib-cr and the presence of an extended-spectrum beta-lactamase., Conclusions: A high prevalence of plasmid-mediated quinolone resistance determinants [i.e., qnrS, qnrB and aac(6')-Ib-cr] was found in quinolone-resistant K. pneumoniae isolated in a large hospital in Singapore.

Streptococcus pneumoniae isolates causing invasive disease at a large tertiary institute in Singapore from 2000 to 2007 were serotyped, with 84 (43.8 %) and 159 (82.8 %) isolates belonging to serotypes covered by the pneumococcal heptavalent conjugate and polysaccharide vaccines, respectively. All non-meningitis isolates were susceptible to penicillin, and the attributable mortality was 21.4 %. Patients who fulfilled the US Advisory Committee on Immunization Practices criteria for vaccination with the pneumococcal polysaccharide vaccine comprised 74.0 % of the study cohort and had a significantly higher mortality risk.

In the past 3 decades, classical extended-spectrum beta-lactamases (ESBLs) have probably been the main contributors to gram-negative antimicrobial resistance in Singapore. These appear to be being replaced by the newer CTX-M ESBLs. Metallo-beta-lactamases are found in Pseudomonas aeruginosa but do not seem to have spread widely in Acinetobacter spp. and Enterobacteriaceae. Carbapenem-hydrolysing oxacillinases are prevalent in multidrug-resistant Acinetobacter spp. More insidious developments include the emergence of plasmid AmpC beta-lactamases and multifactorial quinolone resistance in Enterobacteriaceae.

Introduction: Antibiotic resistance in gram-negative bacilli is an area of increasing importance. This prospective study was performed to survey antibiotic resistance in Escherichia coli (E. coli), Klebsiella spp., Pseudomonas aeruginosa and Acinetobacter spp. over a 1-year period., Materials and Methods: Non-duplicate isolates of E. coli, Klebsiella spp., P. aeruginosa and Acinetobacter spp. were collected from participating Singapore hospitals during defined collection periods in 2006 and 2007. Confirmatory identification and antibiotic susceptibility testing were performed at Changi General Hospital. Minimum inhibitory concentrations (MIC) to a defined panel of antibiotics were determined using microbroth dilution methods. The presence of extended-spectrum beta lactamases and AmpC beta-lactamases in Enterobacteriaceae was determined by phenotypic methods, and susceptibility results were defined using current breakpoints from the Clinical Laboratory Standards Institute (CLSI)., Results: Seven hundred and forty-six gram-negative bacilli were received for testing. Resistance to extended-spectrum cephalosporins was present in a third of Enterobacteriaceae isolates, and extended-spectrum beta-lactamases (ESBL) carriage was present in 19.6% and 30.1% of E. coli and Klebsiella pneumoniae, respectively. AmpC enzymes were also detected in 8.5% and 5.6% of E. coli and K. pneumoniae isolates respectively. All Enterobacteriaceae were susceptible to imipenem and meropenem. The most active antibiotics against P. aeruginosa were amikacin, meropenem and piperacillin-tazobactam. A third of P. aeruginosa showed reduced susceptibility to polymyxin B. Carbapenem resistance was significantly higher in Acinetobacter baumannii (70.5%) than in other Acinetobacter species (25.0%). The most active antibiotic against A. baumannii was polymyxin B., Conclusion: Antibiotic resistance is prevalent in gram-negative bacilli isolated from Singapore hospitals. The MIC testing surveillance programme complemented susceptibility data from wider laboratory-based surveillance, and has revealed emerging mechanisms of antibiotic resistance.

A new national antimicrobial resistance surveillance program in Singapore public hospitals that uses WHONET detected high levels of methicillin resistance among Staphylococcus aureus (35.3%), carbapenem resistance among Acinetobacter spp. (49.6%), and third-generation cephalosporin resistance among Klebsiella pneumoniae (35.9%) hospital isolates in 2006. Antimicrobial drug resistance is a major problem in Singapore.

Meticillin-resistant Staphylococcus aureus (MRSA) was unexpectedly isolated from a pig used for streptozotocin-induced diabetes research. To investigate the possible source of the MRSA isolate, nasal swabs were obtained from the animal herd, and from animal holding rooms, and veterinary and research staff involved in the handling of the animals. Overall, four MRSA isolates were cultured from three pigs and from a clinician/scientist. Two were ST22-MRSA-IV, a human strain type associated with epidemic spread. The other two were ST398-MRSA-V, a strain type associated with pigs. Thus, care should be taken to prevent cross-transmission of MRSA.

Aims: We undertook this study to define the incidence of toxigenic Clostridium difficile in our hospital and to characterise the isolates., Methods: All unformed stool was tested for the presence of Toxin A (TcdA) and Toxin B (TcdB), and cultured for C. difficile. Culture filtrates were also tested for TcdA and TcdB. Detection of tcdA and tcdB genes was carried out for A(-)B(+) strains by polymerase chain reaction (PCR).The minimum inhibitory concentrations (MICs) of metronidazole, vancomycin and clindamycin for all isolates were tested using the Etest. PCR ribotyping was carried out on all isolates., Results: The incidence of Clostridium difficile associated disease (CDAD) was 3.2 cases per 1000 admissions or discharges and 53.8 cases per 100 000 patient days. Most cases occurred in renal and haematology patients. CDAD was more common in patients aged over 50 years and of male gender. The Indian population was under-represented. Fourteen (11.8%) isolates were A(-)B(+). All strains were susceptible to metronidazole but one strain showed intermediate resistance to vancomycin. Only 12.8% of the isolates were susceptible to clindamycin. Thirty-five isolates had PCR ribotype A, of which 29 (83%) had a clindamycin MIC >256 mg/L. Thirty-three had PCR ribotype B, of which only one (3%) had a clindamycin MIC >256 mg/L. The 14 A(-)B(+) strains were all PCR ribotype C, and had a range of MICs for clindamycin from 2 to >256 mg/L., Conclusions: The incidence of CDAD in our hospital is relatively low. Isolates remain susceptible to metronidazole and vancomycin.

Introduction: Until recently, vancomycin-resistant enterococcus (VRE) infection or colonisation was a rare occurrence in Singapore. The first major VRE outbreak involving a 1500-bed tertiary care institution in March 2005 presented major challenges in infection control and came at high costs. This study evaluates the predictors of VRE carriage based on patients' clinical and demographic profiles., Materials and Methods: Study patients were selected from the hospital inpatient census population during the VRE outbreak (aged 16 years or more). Clinical information from 84 cases and 377 controls were analysed., Results: Significant predictors of VRE carriage included: age>65 years Odds ratio (OR), 1.98; 95% CI (confidence interval), 1.14 to 3.43); female gender (OR, 2.15; 95% CI, 1.27 to 3.65); history of diabetes mellitus (OR, 1.94; 95% CI, 1.14 to 3.30), and staying in a crowded communal ward (OR, 2.75; 95% CI, 1.60 to 4.74). Each additional day of recent hospital stay also posed increased risk (OR, 1.03; 95% CI, 1.01 to 1.04)., Conclusion: Elderly diabetic females with prolonged hospitalisation in crowded communal wards formed the profile that significantly predicted VRE carriage in this major hospital-wide outbreak of VRE in Singapore. It is imperative that active VRE surveillance and appropriate infection control measures be maintained in these wards to prevent future VRE outbreaks.

Objective: To compare the incidence of carbapenemase genes in Acinetobacter baumannii between two time periods., Methods: We studied 114 isolates of imipenem-resistant A. baumannii collected over two 5 month periods (in 1996 and 2001). Isolates showing carbapenemase activity by plate bioassay were screened for carbapenemase genes using PCR. Chromosomal DNA from strains carrying carbapenemase genes was subjected to PFGE after digestion with ApaI., Results: The incidence of imipenem-resistant A. baumannii in our hospital rose from 1.1 per 1000 admissions in 1996 to 2.3 per 1000 admissions in 2001. However, the number of carbapenemase-producing A. baumannii rose only slightly in 2001 (0.8 per 1000 admissions) compared to 1996 (0.5 per 1000 admissions). Of 44 isolates with carbapenemase activity, 4 isolates carried bla(IMP-4), 5 carried bla(OXA-58), and 40 carried bla(OXA-23). In addition, most isolates carried a bla(OXA-51)-type beta-lactamase gene. All strains with bla(IMP-4), also carried bla(OXA-58) and bla(PSE-1), but not bla(OXA-51)-type beta-lactamase genes. PCR analysis repeated on seven recent isolates of susceptible A. baumannii showed only the presence of bla(OXA-51)-type beta-lactamase genes. A total of five novel bla(OXA-51)-type beta-lactamase genes (bla(OXA-88),-91,-93,-94, and -95) and one new bla(OXA-58)-type beta-lactamase gene (bla(OXA-96)) were found., Conclusions: The incidence of carbapenemase genes did not vary significantly between the two study periods. There is a wide diversity of OXA genes in A. baumannii in Singapore. The most common carbapenemase gene found in our study was bla(OXA-23).

The aim of this study was to determine the extent of EMRSA-15 spread in hospitals in Singapore. Molecular analysis of 197 non-duplicate meticillin-resistant Staphylococcus aureus (MRSA) isolates collected from five acute care public hospitals in Singapore in May 2005 revealed that 66 (33.5%) were EMRSA-15 while 121 (61.4%) belonged to the endemic multidrug-resistant ST239 clone. Median and mode vancomycin MIC for both major clones of health-care-associated MRSA were relatively high at 2.0 microg ml-1. Subsequent laboratory surveillance data collected from the first half of 2006 confirmed increasing numbers of the EMRSA-15 clone--ranging from 25.0 to 66.1% of all MRSA isolated in local hospitals--replacing the ST239 clone island-wide.