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This study investigated 248 extended-spectrum β-lactamase-producing Escherichia coli isolates from 2012 to 2013 for hybrid blaCTX-M genes. blaCTX-M genes were detected in 228 isolates of which 14 isolates were hybrid blaCTX-M positive (6 blaCTX-M-123, 6 blaCTX-M-64, and 2 blaCTX-M-132). The 14 hybrid blaCTX-M-carrying isolates (8 from chickens, 2 each from pigs and cattle, 1 each from dog and rodent) were genetically diverse. All but 2 hybrid blaCTX-M were carried on IncI1 (5 blaCTX-M-123) and IncI2 (6 blaCTX-M-64 and one blaCTX-M-132) plasmids. Our IncI1 and IncI2 plasmids had pHNAH4-1-like and pHN1122-1-like restriction fragment length polymorphism patterns, respectively. Genetic relatedness of the plasmids to pHNAH4-1 and pHN1122-1 were confirmed by complete sequencing of 3 plasmids, pCTXM123_C0996, pCTXM64_C0967, and pCTXM132_P0421. Plasmids closely related to pHNAH4-1 and pHN1122-1 and carrying different blaCTX-M alleles have been reported from multiple geographic areas in China previously. The findings highlighted the wide dissemination of hybrid blaCTX-M variants in different parts of China., (Copyright © 2015 Elsevier Inc. All rights reserved.)

This study assessed pneumococcal carriage in the early periods after routine use of 13-valent pneumococcal conjugate vaccine (PCV13) in Hong Kong. Nasopharyngeal swabs were obtained from 1110 children (<5 years) admitted with acute illness during September 2010-August 2013. Pneumococcal carriage rate was 13.5% in unvaccinated children, 14.1% in children who had ≥1 PCV dose and 15.3% in children who had ≥3 PCV doses. Nonv-PCV13 serotypes comprised 56.4% of all isolates. The most common serogroup/types were 15 (15A, 5.1%; 15B, 10.3%; 15C, 9.6%; 15F, 0.6%), 19F (17.9%), 6A (7.1%) and 6C (7.1%). Carriage of serogroup 15 was more common among vaccinated children (4.1% versus 0.6%, P = 0.033). Molecular typing revealed that expansion of several clones (clonal complex, CC63, CC199, CC1262, CC3397) was responsible for the increase in serogroup 15. Almost all CC63 and CC3397 isolates were nonsusceptible to both penicillin and erythromycin. The finding highlights the emergence of serogroup 15 following PCV13 use., (Copyright © 2015 Elsevier Inc. All rights reserved.)

We collected nasal, axilla, and groin swabs from 252 adult patients from 2 nephrology centers in Hong Kong. Staphylococcus lugdunensis carriage was detected in 51.6% patients (groin, 39.3%; axilla, 19.8%; nose, 17.9%). The carriage rates of methicillin-sensitive S. lugdunensis and methicillin-resistant S. lugdunensis (MRSL) were 46.0% and 8.3%, respectively. Independent risk factors for S. lugdunensis carriage included male sex (odds ratio [OR], 4.4), hemodialysis (OR, 2.2), and aged 18-50years (OR, 2.4). The isolates belonged to 10 pulsotype clusters (n=129) and 8 singletons (n=8). All MRSL and most gentamicin- and tetracycline-resistant strains were found in a predominating sequence type 3 clone, designated HKU1, which accounted for 51.8% of all colonizing S. lugdunensis strains. The 21 MRSL isolates had SCCmec type V (n=18), type IV (n=2), and type I (n=1). The finding highlights the potential for dissemination of multidrug resistance through successful S. lugdunensis clones., (Copyright © 2015 Elsevier Inc. All rights reserved.)

This study assessed the temporal changes in the molecular epidemiology of bacteremic Escherichia coli isolates producing CTX-M-14 in Hong Kong. Blood isolates from 1996 to 1998 (period 1, n = 50) and 2007 to 2008 (period 2, n = 117) were investigated by molecular methods. CTX-M-type ESBL was carried by 98.2% (164/167) of the isolates. In both periods, the CTX-M-9 group and CTX-M-14 allele were the predominant ESBL type. The major clones were found to change from ST68 and ST405 in period 1 to ST131, ST69, and ST12 in period 2. Among 65 CTX-M-14-producing plasmids investigated further, 54 had the FII replicon. Replicon sequence typing and plasmid polymerase chain reaction-restriction fragment length polymorphism showed that 79.6% (43/54) of the FII plasmid subset was similar to the completely sequenced plasmid, pHK01 (human urine, Hong Kong, 2004). These pHK01-like plasmids were found to have spread to the major clones (ST68, ST405, and ST131) and multiple singleton isolates of all 4 phylogenetic groups., (Copyright © 2012 Elsevier Inc. All rights reserved.)

This study assessed the changes in serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolates in children before and after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Hong Kong. Nasopharyngeal specimens were collected from 1978 and 2211 children (ages, 2 to 6 years) attending day care centers or kindergartens in period 1 (1999-2000) and period 2 (2009-2010), respectively. Carriage of PCV7 serotypes decreased from 12.8% to 8.6% (P < 0.01). The relative contribution of PCV7 serotypes 14 and 18C had decreased, whereas that for non-PCV7 serotypes 19A, 6A, 6C, 23A, and 15B had increased. In period 2, PCV7 penetration rate (at least 1 dose) for children aged 2, 3, 4, and 5 years was 43%, 35.7%, 26.7%, and 20.4%, respectively. In multivariate analysis, PCV7 use was the only independent variable associated with fewer PCV7 serotype carriages (odds ratio 0.5; P = 0.001). In period 2, high rates of dual penicillin/erythromycin nonsusceptibility were found in serotypes 6B (77.3%), 14 (100%), 19F (100%), 23F (78%), 19A (75%), 6A (87.8%), 6C (59.3%), and 23A (78.9%)., (Copyright © 2011 Elsevier Inc. All rights reserved.)

A study was conducted to determine the prevalence of the 2 newly described types, 6C and 6D, among pneumococcal isolates collected in Hong Kong before availability of the 7-valent pneumococcal conjugate vaccine. A total of 154 serogroup 6 isolates obtained from nasopharynx (n = 106), blood (n = 22), respiratory (n = 24), and cerebrospinal fluid (CSF) (n = 2) during 1995 to 2001 were analyzed by polymerase chain reaction typing. Five nasopharyngeal and 2 sputum isolates were found to belong to 6C and 6D, respectively. The isolates were genetically diverse, but one 6C and two 6D isolates exhibited some clonal relationship. Phylogenetic analysis of the wchA-wciN(β)-wciO nucleotide sequences showed that the Hong Kong 6C/6D isolates had 2 allelic profiles, which were more closely related to 6C/6D isolates from Fijian and Korea than were those from Brazil and the United States. However, all of the wciP gene sequences for both Hong Kong and non-Hong Kong isolates clustered together: 6C isolates with the wciP-9 allele and 6D isolates with the wciP-5 allele. In conclusion, the prevalence of the 2 newly described serotypes was low before the era of the pneumococcal conjugate vaccine. Nonetheless, results from the molecular studies indicated that the evolution of the capsular genes have involved complex pathways., (Copyright © 2010 Elsevier Inc. All rights reserved.)

A prospective multicenter study was conducted to assess the epidemiology of antimicrobial resistance among uropathogens causing uncomplicated cystitis. Adult women with clinical diagnosis of uncomplicated cystitis were enrolled from 54 participating centers distributed all over Hong Kong during 2006 to 2008. A positive urine culture was found in 59.5% (352/592) patients. The patients had mean age of 44.9 years, and most (89.2%) were otherwise healthy. The most prevalent causative organism was Escherichia coli (77%), followed by other Enterobacteriaceae (14.2%), staphylococci (5.1%), and other Gram-positive bacteria (3.7%). The resistance rates of E. coli to co-trimoxazole and ciprofloxacin were 29.5% and 12.9%, respectively, and 14 isolates (5.2%) were confirmed as extended-spectrum beta-lactamase (ESBL) producers. Of the ESBL producers, molecular studies showed CTX-M-14, CTX-M-24, or CTX-M-9. Nitrofurantoin and fosfomycin were active against >90% of the isolates, regardless of resistance phenotypes for other drugs. Pulsed-field gel electrophoresis of representative isolates showed that the antibiotic-resistant strains were genetically diverse. Patients with history of recent antibiotic use were significantly more likely to have infection by E. coli with co-trimoxazole resistance (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.4-5.7; P = 0.003) and ciprofloxacin resistance (OR, 2.5; 95% CI, 1.1-5.8; P = 0.03). Knowledge of the resistance data and risk factors could inform better use of antibiotics for empiric therapy for acute uncomplicated cystitis.

This study assessed the susceptibility trend of methicillin-resistant Staphylococcus aureus (MRSA) in 5 Hong Kong hospitals from 1995 to 2005. Representative blood isolates were characterized to correlate the changes in resistance phenotypes with the clonal nature of MRSA. The prevalence of multisusceptible (MS) MRSA, defined by sensitivity to gentamicin, co-trimoxazole, and fusidic acid, was found to increase dramatically from <2% in 1995 to 1997 to 4.5% to 5.8% in 1998 to 1999 and remained at around 10% thereafter. Isolation of MS-MRSA was significantly associated with older age, convalescent care, and blood culture source. Molecular typing showed that the increasing isolation of MS-MRSA was associated with the spread of ST45/Staphylococcus cassette chromosome mec (SCCmec) IV or V with spa t1768, t1857, or t1081. Other features of the ST45 strains are as follows: agr4, capsular type 8, and Panton-Valentine leukocidin (PVL) negative. Two other epidemic clones, EMRSA-16 (ST36/SCCmec II) and CC398 (ST1277/SCCmec V), were detected as sporadic isolates for the first time in Hong Kong.

This territory-wide study evaluated the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in residential care homes for elderly (RCHEs) in Hong Kong. MRSA colonization was assessed by taking swab culture from anterior nares and active skin lesions. Of 487 RCHEs surveyed, 80 MRSA strains were recovered from 1563 residents, giving a prevalence of 5.1%. Twenty-four isolates had SCCmec II, 2 had SCCmec III, 17 had SCCmec IV, 36 had SCCmec V, and 1 had a composite SCCmec type. Pulsed-field gel electrophoresis typing clustered 75 isolates into 7 clones (HKU10 to 50, HKU80, and HKU90). Two predominant types, HKU30 and HKU50, which together account for 75% of all MRSA strains, were found in 13 and 15 of the 18 geographic districts in Hong Kong, respectively. The main features for HKU50 strains were spa t1081/ST45-IV or V, capsular type 8, agrIV, and hla, seg, sei positive. On the other hand, HKU30 strains had spa t002/ST5-II, capsular type 5, agrII, and were hla, seg, sei positive. HKU30 strains were often multidrug resistant (MDR, involving ciprofloxacin, erythromycin, gentamicin, and tetracycline). In contrast, HKU50 strains exhibit both multidrug resistance (MDR) (involving ciprofloxacin, erythromycin, and tetracycline, but not gentamicin) and non-MDR patterns.