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Abstract Background Carbapenem-resistant Enterobacter cloacae complex (CREC) is a new emerging threat to global public health. The objective of the study was to investigate the clinical characteristics and molecular epidemiology of CREC infections in the medical center of northeast China. Methods Twenty-nine patients were infected/colonized with CREC during a ten-year period (2010–2019) by WHONET analysis. Antibiotic susceptibilities were tested with VITEK 2 and micro broth dilution method (for polymyxin B and tigecycline). Carbapenemase encoding genes, β-lactamase genes, and seven housekeeping genes for MLST were amplified and sequenced for 18 cryopreserved CREC isolates. Maximum likelihood phylogenetic tree was built with the concentrated sequences to show the relatedness between the 18 isolates. Results There was a rapid increase in CREC detection rate during the ten-year period, reaching 8.11% in 2018 and 6.48% in 2019. The resistance rate of CREC isolates to imipenem and meropenem were 100.0 and 77.8%, however, they showed high sensitivity to tigecycline, polymyxin B and amikacin. The 30-day crude mortality of CREC infection was 17.4%, indicating that it may be a low-virulence bacterium. Furthermore, molecular epidemiology revealed that ST93 was the predominant sequence type followed by ST171 and ST145, with NDM-1 and NDM-5 as the main carbapenemase-encoding genes. Moreover, E. hormaechei subsp. steigerwaltii and E. hormaechei subsp. oharae were the main species, which showed different resistance patterns. Conclusion Rising detection rate of CREC was observed in a tertiary hospital, which showed heterogeneity in drug resistance patterns, resistance genes, and MLST types. Effective infection prevention and control measures should be taken to reduce the spread of CREC.

Abstract Background Enterobacter cloacae complex (ECC) is one of the most common extended-spectrum β-lactamase and carbapenemase-producing pathogen that threatens millions of the elderly and vulnerable sick persons. The objective of this study was to perform the molecular characteristics of the carbapenem-resistant E. cloacae complex (CREC) emerged in Heilongjiang Province of China. Methods Six CREC strains were isolated from the patients with infectious diseases. The identities of ECC isolates were confirmed by sequencing the polymerase chain reaction (PCR) products of 16S rRNA gene. The characterization of the CREC isolates were analyzed by sequencing PCR products of the carbapenemase, ampC and fluoroquinolone resistance genes and performing multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and whole genome sequencing. Results All 6 isolates harbored multiple resistance genes. Of them, 5 carried metallo-β-lactamases and one was bla KPC-2-positive. The levofloxacin and ciprofloxacin-resistant strains had substitutions of gyrA83, gyrA87, and parC80 in the quinolone-resistance determining regions. The MLST analyses revealed that 6 isolates belonged to five sequence types (ST520, ST528, ST1119, ST1120, and ST93) while the PFGE patterns of the isolates fallen into four clusters. The strain ST1120 was found to carry two separated plasmids that encode bla NDM-1 and bla IMP-4. Conclusions Our study, for the first time, identified a CREC strain that co-produces bla NDM-1 and bla IMP-4 in the Northeast China. Our finding emphasizes an urgent need for more intensive surveillance and precaution measures to prevent the CERC spread.

Background: Carbapenem-resistant Enterobacter cloacae complex (CREC) is a new emerging threat to global public health. The objective of the study was to investigate the clinical characteristics and molecular epidemiology of CREC infections in the medical center of northeast China.Methods: Twenty-nine patients were infected/colonized with CREC during a ten-year period (2010-2019) by WHONET analysis. Antibiotic susceptibilities were tested with VITEK 2 and micro broth dilution method (for polymyxin B and tigecycline). Carbapenemase encoding genes, β-lactamase genes, and seven housekeeping genes for MLST were amplified and sequenced for 18 cryopreserved CREC isolates. Maximum likelihood phylogenetic tree was built with the concentrated sequences to show the relatedness between the 18 isolates.Results: There was a rapid increase in CREC detection rate during the ten-year period, reaching 8.11% in 2018 and 6.48% in 2019. The resistance rate of CREC isolates to imipenem and meropenem were 100.0 and 77.8%, however, they showed high sensitivity to tigecycline, polymyxin B and amikacin. The 30-day crude mortality of CREC infection was 17.4%, indicating that it may be a low-virulence bacterium. Furthermore, molecular epidemiology revealed that ST93 was the predominant sequence type followed by ST171 and ST145, with NDM-1 and NDM-5 as the main carbapenemase-encoding genes. Moreover, E. hormaechei subsp. steigerwaltii and E. hormaechei subsp. oharae were the main species, which showed different resistance patterns.Conclusion: Rising detection rate of CREC was observed in a tertiary hospital, which showed heterogeneity in drug resistance patterns, resistance genes, and MLST types. Effective infection prevention and control measures should be taken to reduce the spread of CREC. [ABSTRACT FROM AUTHOR]

This observational study aimed to determine MRSA prevalence using strain‐specific real‐time PCR at the pig level, stratified by age groupings, within a pig enterprise. A total of 658 samples were collected from individual pigs (n = 618) and the piggery environment (n = 40), distributed amongst five different pig age groups. Presumptive MRSA isolates were confirmed by the presence of mecA, and MALDI‐TOF was performed for species verification. All isolates were tested against 18 different antimicrobials. MRSA was isolated from 75.2% (95% CI 71.8–78.6) of samples collected from pigs, and 71% of the MRSA isolates from this source were identified as community‐associated (CA)‐MRSA ST93, while the remainder were livestock‐associated (LA)‐MRSA ST398. Amongst environmental isolates, 80% (CI 64.3–95.7) were ST93 and the remainder ST398. All MRSA isolates from pigs and the environment were susceptible to ciprofloxacin, gentamicin, linezolid, mupirocin, rifampicin, sulfamethoxazole–trimethoprim, teicoplanin and vancomycin. Phenotypic rates of resistance were penicillin (100%), clindamycin (97.6%), erythromycin (96.3%), ceftiofur (93.7%), chloramphenicol (81.2%), tetracycline (63.1%) and amoxicillin–clavulanate (63.9%). A low prevalence of resistance (9.2%) was observed against neomycin and quinupristin–dalfopristin. The probability of MRSA carriage in dry sows (42.2%) was found to be significantly lower (p <.001) when compared to other age groups: farrowing sows (76.8%, RR1.82), weaners (97.8%, RR 2.32), growers (94.2%, RR 2.23) and finishers (98.3%, RR 2.33). Amongst different production age groups, a significant difference was also found in antimicrobial resistance for amoxicillin–clavulanate, neomycin, chloramphenicol and tetracycline. Using the RT‐PCR assay adopted in this study, filtering of highly prevalent ST93 and non‐ST93 isolates was performed at high throughput and low cost. In conclusion, this study found that weaner pigs presented a higher risk for CA‐MRSA and antimicrobial resistance compared to other age groups. These findings have major implications for how investigations of MRSA outbreaks should be approached under the One‐Health context. [ABSTRACT FROM AUTHOR]

Background: Enterobacter cloacae complex (ECC) is one of the most common extended-spectrum β-lactamase and carbapenemase-producing pathogen that threatens millions of the elderly and vulnerable sick persons. The objective of this study was to perform the molecular characteristics of the carbapenem-resistant E. cloacae complex (CREC) emerged in Heilongjiang Province of China.Methods: Six CREC strains were isolated from the patients with infectious diseases. The identities of ECC isolates were confirmed by sequencing the polymerase chain reaction (PCR) products of 16S rRNA gene. The characterization of the CREC isolates were analyzed by sequencing PCR products of the carbapenemase, ampC and fluoroquinolone resistance genes and performing multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and whole genome sequencing.Results: All 6 isolates harbored multiple resistance genes. Of them, 5 carried metallo-β-lactamases and one was blaKPC-2-positive. The levofloxacin and ciprofloxacin-resistant strains had substitutions of gyrA83, gyrA87, and parC80 in the quinolone-resistance determining regions. The MLST analyses revealed that 6 isolates belonged to five sequence types (ST520, ST528, ST1119, ST1120, and ST93) while the PFGE patterns of the isolates fallen into four clusters. The strain ST1120 was found to carry two separated plasmids that encode blaNDM-1 and blaIMP-4.Conclusions: Our study, for the first time, identified a CREC strain that co-produces blaNDM-1 and blaIMP-4 in the Northeast China. Our finding emphasizes an urgent need for more intensive surveillance and precaution measures to prevent the CERC spread. [ABSTRACT FROM AUTHOR]

Background: In Australia, community-associated methicillin-resistant Staphylococcus aureus (MRSA) lineage sequence type (ST) 93 has rapidly risen to dominance since being described in the early 1990s. We examined 459 ST93 genome sequences from Australia, New Zealand, Samoa, and Europe to investigate the evolutionary history of ST93, its emergence in Australia and subsequent spread overseas.Results: Comparisons with other S. aureus genomes indicate that ST93 is an early diverging and recombinant lineage, comprising of segments from the ST59/ST121 lineage and from a divergent but currently unsampled Staphylococcal population. However, within extant ST93 strains limited genetic diversity was apparent with the most recent common ancestor dated to 1977 (95% highest posterior density 1973–1981). An epidemic ST93 population arose from a methicillin-susceptible progenitor in remote Northern Australia, which has a proportionally large Indigenous population, with documented overcrowded housing and a high burden of skin infection. Methicillin-resistance was acquired three times in these regions, with a clade harboring a staphylococcal cassette chromosome mec (SCCmec) IVa expanding and spreading to Australia’s east coast by 2000. We observed sporadic and non-sustained introductions of ST93-MRSA-IVa to the United Kingdom. In contrast, in New Zealand, ST93-MRSA-IVa was sustainably transmitted with clonal expansion within the Pacific Islander population, who experience similar disadvantages as Australian Indigenous populations.Conclusion: ST93 has a highly recombinant genome including portions derived from an early diverging S. aureus population. Our findings highlight the need to understand host population factors in the emergence and spread of antimicrobial resistant community pathogens.

Background: In Australia, community-associated methicillin-resistant Staphylococcus aureus (MRSA) lineage sequence type (ST) 93 has rapidly risen to dominance since being described in the early 1990s. We examined 459 ST93 genome sequences from Australia, New Zealand, Samoa, and Europe to investigate the evolutionary history of ST93, its emergence in Australia and subsequent spread overseas. Results: Comparisons with other S. aureus genomes indicate that ST93 is an early diverging and recombinant lineage, comprising of segments from the ST59/ST121 lineage and from a divergent but currently unsampled Staphylococcal population. However, within extant ST93 strains limited genetic diversity was apparent with the most recent common ancestor dated to 1977 (95% highest posterior density 1973–1981). An epidemic ST93 population arose from a methicillin-susceptible progenitor in remote Northern Australia, which has a proportionally large Indigenous population, with documented overcrowded housing and a high burden of skin infection. Methicillin-resistance was acquired three times in these regions, with a clade harboring a staphylococcal cassette chromosome mec (SCCmec) IVa expanding and spreading to Australia’s east coast by 2000. We observed sporadic and non-sustained introductions of ST93-MRSA-IVa to the United Kingdom. In contrast, in New Zealand, ST93-MRSA-IVa was sustainably transmitted with clonal expansion within the Pacific Islander population, who experience similar disadvantages as Australian Indigenous populations. Conclusion: ST93 has a highly recombinant genome including portions derived from an early diverging S. aureus population. Our findings highlight the need to understand host population factors in the emergence and spread of antimicrobial resistant community pathogens. [ABSTRACT FROM AUTHOR]

Background: The Central Australian Indigenous population has a high incidence of Staphylococcus aureus bacteremia (SAB) but little is known about the local molecular epidemiology.Methods: Prospective observational study of bacteremic and nasal colonizing S.aureus isolates between June 2006 to June 2010. All isolates underwent single nucleotide polymorphism (SNP) genotyping and testing for the presence of the Panton-Valentine Leucocidin (pvl) gene.Results: Invasive isolates (n = 97) were predominantly ST93 (26.6 %) and pvl positive (54.3 %), which was associated with skin and soft tissue infections (OR 4.35, 95 % CI 1.16, 16.31). Non-multiresistant MRSA accounted for 31.9 % of bacteremic samples and showed a trend to being healthcare associated (OR 2.16, 95 % CI 0.86, 5.40). Non-invasive isolates (n = 54) were rarely ST93 (1.9 %) or pvl positive (7.4 %).Conclusions: In Central Australia, ST93 was the dominant S.aureus clone, and was frequently pvl positive and associated with an aggressive clinical phenotype. Whether non-nasal carriage is more important with invasive clones or whether colonization occurs only transiently remains to be elucidated. [ABSTRACT FROM AUTHOR]

Abstract: Panton–Valentine leukocidin (PVL)-positive community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) isolates are widespread in many countries, with varying distribution and epidemiology. The aim of this study was to characterise 10 PVL-positive MRSA isolates collected during February 2010 to January 2011 from skin and soft-tissue infections in the North Italian Province of Bolzano. Accessory gene regulator (agr) typing, staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) gene typing, multilocus sequence typing, toxin gene profiling, polymerase chain reaction for type I arginine catabolic mobile element (ACME) and antimicrobial resistance typing were applied to the isolates. Eight different CA-MRSA clones were identified, including ST30-IVc, ST772-V, ST80-IVc, ST5-IVc, ST88-IVa, ST93-IVa, ST8-IVc and the type I ACME-positive ST8-IVa. The high heterogeneity of PVL-positive MRSA probably reflects the introduction of different clones by international travellers or immigrants. [Copyright &y& Elsevier]

High-resolution melting analysis is an inherently robust, easy and inexpensive approach to the examination of genomic regions containing single-nucleotide polymorphisms and hypervariable loci. Staphylococcus aureus sequence type (ST) 93 is a singleton, Panton–Valentine leukocidin-positive clone unique to Australia. A high-resolution melting-based method for the identification of ST93 was developed, and a similar approach was used to reveal diversity within the spa locus of this lineage. Statistical and graphical methods that account for instrumental and operator-dependent variation in high-resolution melting curves were developed, to allow greater confidence and reproducibility in deciding whether another curve is truly different from the baseline curve of an amplicon with known sequence. The data support a very early acquisition, or multiple independent acquisitions, of SCC mec by ST93 methicillin-susceptible S. aureus (MSSA), and the coexistence of MSSA and methicillin-resistant S. aureus versions of the same lineage within northern Australia. [ABSTRACT FROM AUTHOR]

Background: The emergence of carbapenem-resistant Enterobacteriaceae (CRE) has become a significant problem for global public health. Currently, treatments program is minimal. This study aimed to evaluate the molecular mechanisms of carbapenem-resistant Enterobacter cloacae complex isolates (CREC) infections. Methods: Resistance genes were detected using PCR with specific primers. Multilocus sequence typing (MLST) was also performed. Furthermore, we evaluated the effects of polymyxin B (PMB) and tigecycline (TGC) antibiotics (Abs) alone and in combination with meropenem (MEM), amikacin (AMK), and levofloxacin (LEV) against CREC isolates. The results were then compared with in vitro synergy testing results obtained from time-kill assays (TKAs), and the microdilution checkerboard method., Results: The synergistic efficiency of PMB + TGC was also evaluated. Abs use clinically achievable concentrations to determine the antibacterial effects of the Ab. Similar sequence type (ST) classifications had a comparably resistant phenotype; PMB-based combination therapy is better than TGC-based combination therapy., Conclusions: we found that the combination of PMB + AMK is promising for the treatment of AMK-sensitive CREC. The high-risk ST93 carrying the bla KPC-2 gene should be monitored., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare., (2019 Annals of Translational Medicine. All rights reserved.)

Background: In Australia, community-associated methicillin-resistant Staphylococcus aureus (MRSA) lineage sequence type (ST) 93 has rapidly risen to dominance since being described in the early 1990s. We examined 459 ST93 genome sequences from Australia, New Zealand, Samoa, and Europe to investigate the evolutionary history of ST93, its emergence in Australia and subsequent spread overseas. Results: Comparisons with other S. aureus genomes indicate that ST93 is an early diverging and recombinant lineage, comprising of segments from the ST59/ST121 lineage and from a divergent but currently unsampled Staphylococcal population. However, within extant ST93 strains limited genetic diversity was apparent with the most recent common ancestor dated to 1977 (95% highest posterior density 1973-1981). An epidemic ST93 population arose from a methicillin-susceptible progenitor in remote Northern Australia, which has a proportionally large Indigenous population, with documented overcrowded housing and a high burden of skin infection. Methicillin-resistance was acquired three times in these regions, with a clade harboring a staphylococcal cassette chromosome mec (SCC mec ) IVa expanding and spreading to Australia's east coast by 2000. We observed sporadic and non-sustained introductions of ST93-MRSA-IVa to the United Kingdom. In contrast, in New Zealand, ST93-MRSA-IVa was sustainably transmitted with clonal expansion within the Pacific Islander population, who experience similar disadvantages as Australian Indigenous populations. Conclusion: ST93 has a highly recombinant genome including portions derived from an early diverging S. aureus population. Our findings highlight the need to understand host population factors in the emergence and spread of antimicrobial resistant community pathogens.