Prevalence of Carbapenem-Resistant Enterobacteriaceae in Seoul, Korea

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) is increasing globally. However, a few studies have addressed their epidemiology in Seoul, Korea. In this study, we conducted one-year surveillance of CRE among 1,468 clinical isolates of Enterobacteriaceae at the hospital in Seoul with molecular characterization of carbapenemase genes. About 85% of CRE-positive samples were isolated from the elderly age group (above 60 years). The most common isolated organisms were Klebsiella pneumoniae (K. pneumoniae) (56.5%) and Escherichia coli (E.coli) (17.0%). We detected six different Carbapenemase-producing Enterobacteriaceae (CPE) of blaKPC, blaNDM, blaOXA, blaVIM, blaIMP, and blaGES alone or in combination with other bla genes. Typically, 853 (58.1%) isolates were tested positive for at least one CPE. KPC (K. pneumoniae carbapenemase)-2 was the most common CPE type (46.0%) followed by NDM (New Delhi metallo-β-lactamase)-1 (5.9%). KPC-2 was most commonly found in K. pneumoniae (494/676 isolates [73.1%]) and E.coli (107/676 isolates [15.8%]), whereas NDM-1 was commonly found in Enterobacter cloacae complex (20/86 isolates [23.3%]). Detailed information and molecular characteristics of CPE is essential to prevent the spread of these pathogens.

Comparison of Enterococcus faecium Bacteremic Isolates from Hematologic and Non-hematologic Patients: Differences in Antimicrobial Resistance and Molecular Characteristics

BACKGROUND: Enterococcus faecium, especially vancomycin-resistant E. faecium (VREfm), is a major concern for patients with hematologic diseases. Exposure to antibiotics including fluoroquinolone, which is used as a routine prophylaxis for patients with hematologic (MH) diseases, has been reported to be a risk factor for infection with vancomycin-resistant eneterocci. We compared the characteristics of E. faecium isolates according to their vancomycin susceptibility and patient group (MH vs non-MH patients). METHODS: A total of 120 E. faecium bacteremic isolates (84 from MH and 36 from non-MH patients) were collected consecutively, and their characteristics (susceptibility, multilocus sequence type [MLST], Tn1546 type, and the presence of virulence genes and plasmids) were determined. RESULTS: Among the vancomycin-susceptible E. faecium (VSEfm) isolates, resistance to ampicillin (97.6% vs 61.1%) and high-level gentamicin (71.4% vs 38.9%) was significantly higher in isolates from MH patients than in those from non-MH patients. Notably, hyl, esp, and pEF1071 were present only in isolates with ampicillin resistance. Among the VREfm isolates, ST230 (33.3%) and ST17 (26.2%) were predominant in MH patients, while ST17 (61.1%) was predominant in non-MH patients. Plasmid pLG1 was more prevalent in E. faecium isolates from MH patients than in those from non-MH patients, regardless of vancomycin resistance. Transposon analysis revealed five types across all VREfm isolates. CONCLUSIONS: The antimicrobial resistance profiles and molecular characteristics of E. faecium isolates differed according to the underlying diseases of patients within the same hospital. We hypothesize that the prophylactic use of fluoroquinolone might have an effect on these differences.

Prevalence and Antimicrobial Susceptibility of Genital Mycoplasmataceae in Korean Women: Correlation between Phenotypic Test and Resistance Genes / 대한임상미생물학회지

BACKGROUND: While 7.6% of cultured genital Mycoplasmataceae was identified as Ureaplasma urealyticum, most of them were Ureaplasma parvum (80.3%). This is the first study differentiating between these two species. We investigated the prevalence and antimicrobial resistance of genital Mycoplasmataceae in Korean women. METHODS: A total of 150 specimens submitted to the laboratory for culture of M. hominis and Ureaplasma spp. were included. Detection and antimicrobial susceptibility tests were performed with the Mycoplasma IST2 kit (bioMérieux, France). The identification of Ureaplasma spp. was performed by PCR, and mutations in drug resistance genes were investigated by PCR and sequencing. RESULTS: In total, 66 specimens (44.0%) were positive for genital Mycoplasmatacea: U. parvum, 53 (80.3%); U. urealyticum, 5 (7.6%); M. hominis, 2 (3.0%); mixed infection, 6 (9.1%). Susceptibilities of Ureaplasma spp. to erythromycin, azithromycin, clarithromycin, and doxycycline were 86.0%, 80.7%, 98.2%, and 94.7%, respectively. The susceptibility of Ureaplasma spp. to ofloxacin and ciprofloxacin was 47.4% and 17.5%, respectively. The S83L mutation was found in the ParC subunit of the ofloxacin-resistant (5/7, 71.4%) and the ciprofloxacin-resistant isolates (7/14, 50.0%). One M. hominis isolate showed resistance to erythromycin, azithromycin, and clarithromycin but susceptibility to josamycin, pristinamycin, fluoroquinolones, and tetracyclines. CONCLUSION: The prevalence of genital Mycoplasmataceae in Korean women was 44.0%; most of them were identified as U. parvum. As more than 10% of Ureaplasma spp. showed non-susceptibility to erythromycin and azithromycin (15.5%, 20.7%), a susceptibility test is needed prior to use of these antibiotics. Further study is needed about the clinical features of infections caused by U. urealyticum vs. U. parvum and their associated resistance mechanisms.

Rates of Fecal Transmission of Extended-Spectrum beta-Lactamase-Producing and Carbapenem-Resistant Enterobacteriaceae Among Patients in Intensive Care Units in Korea

BACKGROUND: We investigated the rates of fecal transmission of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) and carbapenem-resistant Enterobacteriaceae (CRE) among patients admitted to intensive care units (ICUs). METHODS: From June to August 2012, rectal cultures were acquired from all patients at ICU admission. For patients not carrying ESBL-E or CRE at admission, follow-up cultures were performed to detect acquisition. A chromogenic assay was used to screen for ESBL-E and CRE. Bacterial species identification and antibiotic susceptibility tests were performed using the Vitek 2 system (bioMerieux, France). ESBL genotypes were determined by PCR, and clonal relatedness of the isolates was assessed by pulsed-field gel electrophoresis. RESULTS: Out of 347 ICU admissions, 98 patients were found to be carriers of ESBL-E (28.2%, 98/347). Follow-up cultures were acquired from 91 of the patients who tested negative for ESBL-E at admission; the acquisition rate in this group was 12.1% (11/91), although none was a nosocomial transmission. For CRE, the prevalence of fecal carriage was 0.3% (1/347), and the acquisition rate was 2.9% (4/140). None of the CRE isolates were carbapenemase-producers. CONCLUSIONS: The high prevalence of ESBL-E carriage on admission (28.2%), coupled with rare nosocomial transmission and the very low carriage rate of CRE (0.3%), challenge the routine use of active surveillance in non-epidemic settings. Nevertheless, passive surveillance measures, such as rapid and accurate screening of clinical specimens, will be critical for controlling the spread of CRE.

Performance Assessment of Advansure(TM) MDR-TB Genoblot Assay Kit for Anti-tuberculosis Drug Susceptibility Test

BACKGROUND: Because of the long time required for conventional drug susceptibility test (DST) for rifampin and isoniazid, development of rapid DSTs is necessary. Recently, the AdvanSure(TM) MDR-TB GenoBlot Assay kit (LG Life Science, Korea), using reverse hybridization line blot assay, was developed. We compared this kit with Genotype(R) MTBDRplus (HAIN Lifescience, Germany) and conventional DST. METHODS: Of the DNAs preserved after performing DST by using Genotype(R), we selected 144 samples having conventional DST results. The experiments with both the kits were performed according to the manufacturers' instructions. For the samples for which discrepant results were obtained, sequencing was performed if the DNA was available. Conventional DST was performed at the Korean Institute of Tuberculosis by using the absolute concentration method. RESULTS: For rifampin, the findings obtained using both the kits were the same with concordance rates of 98.6% (142/144) compared to conventional DST. Of the 2 discrepant findings, one was very major error and the other was major error. For isoniazid, compared to conventional DST, concordance rates of AdvanSure(TM) and Genotype(R) were 95.8%(138/144) and 95.1%(137/144) respectively. Of the 6 discrepant findings between conventional method and Advansure(TM), 5 were very major error and one was major error. All the 7 discrepant findings between conventional method and Genotype(R) were very major error. CONCLUSIONS: The findings obtained using AdvanSure(TM) showed high concordance with those obtained using Genotype(R) and conventional DST. This kit has a higher rate of detection of isoniazid resistance because it includes probes for an additional target (ahpC).

Aminoglycoside Susceptibility Profiles of Enterobacter cloacae Isolates Harboring the aac(6')-Ib Gene / 대한진단검사의학회지

The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.