Predominance and clonal spread of CTX-M-15 in cefotaxime-resistant Klebsiella pneumoniae in Korea and their association with plasmid-mediated quinolone resistance determinants.

INTRODUCTION: ß-lactams and fluoroquinolones are extensively used worldwide in the treatment of infections caused by Enterobacterales. In this study, we investigated the prevalence of extended-spectrum ß-lactamases (ESBL), their correlation with plasmid-mediated quinolone resistance determinants (PMQR) and clonal distribution among the cefotaxime-resistant K. pneumoniae isolates. METHODS: In Korea, a total of 429 K. pneumoniae collected in 2015 were studied. Antimicrobial susceptibility test for cefotaxime, ciprofloxacin and levofloxacin was performed by broth microdilution method. By PCR and/or sequencing, mutations in gyrA and parC genes, PMQR genes and ESBL were identified. Multilocus-sequence-type (MLST) was determined for isolates harboring CTX-M-15. RESULTS: Among the 149 K. pneumoniae showing cefotaxime MICs of >1 µg/ml, 142 (95.3%) isolates were ESBL-producers and CTX-M-15 was predominant (99 isolates). Among the 142 ESBL-producers, mutations in gyrA and parC were found in 112 (78.9%) and 93 isolates (65.5%), respectively. PMQR genes were detected in 141 isolates and the non-susceptibility rate to ciprofloxacin and levofloxacin was 95.1% (135/142) and 82.4% (117/142), respectively. The most frequently found PMQR combination was qnrB-aac(6')-Ib-cr-oqxAB, (58/142, 40.8%). By MLST, four major STs/CC: ST48, ST392, ST307 and CC15 accounted for 67% of the CTX-M-15 producers and the prevalence of qnrB was significantly higher in these four major STs/CC than other groups (P = 0.004). Of note, we found the additive effect of PMQR genes; the more PMQR genes, the higher ciprofloxacin MICs. CONCLUSIONS: CTX-M-15 was predominant among the cefotaxime-resistant K. pneumoniae and co-harboring CTX-M-15 and PMQR genes, especially qnrB, seems to contribute the spread of high risk clones.

A dual-responsive pH-sensor and its potential as a universal probe for assays of pH-changing enzymes.

We described a dual turn-on probe sensitive to both acidity and basicity, which could be designed by connecting a fluorophore to a quencher via metal-ligand interaction. Atto488-labeled nitrilotriacetic acid and polyhistidine peptide were used as the fluorophore and the quencher, respectively, and linked to each other by coordination with a cobalt(II) ion. After preparation of the probe, the pH-sensitive dual turn-on property of the probe has been successfully observed upon responding to both acidity and basicity of the solution. The probe has been employed as a signal reporter in assays of pH-changing enzymes such as penicillinase generating acidity and adenosine deaminase generating basicity. Furthermore, the practical utility of the probe was also demonstrated by utilizing the probe in the discrimination of ß-lactamase-producing bacteria.

Dominance of clonal complex 10 among the levofloxacin-resistant Streptococcus agalactiae isolated from bacteremic patients in a Korean hospital.

Streptococcus agalactiae has emerged as an important cause of invasive infection in adults. Forty-nine S. agalactiae isolates (41 from adults and 8 from neonates) were collected during a 4-year period (2010-2013) and analyzed by multilocus sequence typing (MLST). Antibiotic susceptibility to erythromycin, clindamycin and levofloxacin was determined and the determinants of resistance (ermA, ermB, ermC, mefA, lnuB) were detected by PCR and mutation in gyrA, gyrB, parC and parE gene was investigated by sequence analysis. They were resolved into 14 sequence types (STs) and belonged to five clonal complexes (CCs). The distribution of CC was significantly different according to the age group; CC1 (18/41) and CC10 (13/41) was the most common among the adult isolates but CC19 (5/8) was predominant among the neonatal isolates. The resistance rate to erythromycin, clindamycin was 18.4% and 24.5%, respectively. Among the 13 strains resistant to erythromycin and/or clindamycin, two isolates harbored ermA and 10 isolates harbored ermB. The levofloxacin resistance rate was very high (32.7%) and was significantly higher in CC10 (71.4%). All the levofloxacin-resistant isolates had identical gyrA substitution (Ser81Leu) but parC substitution was different according to the CCs. The additional mutation in parE (His221Tyr) was found only in CC19. Continuous monitoring of the fluoroquinolone resistance and genotypic distribution among S. agalactiae is needed.

Prevalence of acquired fosfomycin resistance among extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae clinical isolates in Korea and IS26-composite transposon surrounding fosA3.

OBJECTIVES: To investigate the prevalence of plasmid-mediated fosfomycin resistance determinants among extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae and their genetic environments. METHODS: A total of 347 non-duplicate ESBL-producing E. coli (165) and K. pneumoniae (182) were collected. The fosfomycin MICs were determined by the agar dilution method according to CLSI guidelines. PCR was used to detect the plasmid-encoded fosfomycin resistance genes (fosA, fosA3, fosB and fosC2). For isolates harbouring plasmid-encoded fosfomycin resistance genes, sequence types (STs) were determined. The transformation experiment was performed using E. coli TOPO10 (Invitrogen, USA) as a recipient strain. With the plasmids from the transformants, plasmid replicon typing was performed and the nucleotide sequences adjacent to fosA3 were determined. RESULTS: The susceptibility to fosfomycin was 92.9% in E. coli and 95.2% in K. pneumoniae. Of the 21 isolates non-susceptible to fosfomycin (8 E. coli and 13 K. pneumoniae), 7 (5 E. coli and 2 K. pneumoniae) isolates harboured fosA3 and all of them co-harboured bla(CTX-M-1group) or bla(CTX-M-9group). The STs of the isolates harbouring fosA3 were diverse (E. coli: ST1, ST1, ST533, ST2 and ST86; K. pneumoniae: ST11 and ST101). The plasmid replicon types of transformants co-harbouring bla(CTX-M-1group) and bla(CTX-M-9group) were IncF and IncN, respectively. By sequence analysis, we found the common feature that the fosA3 gene, connected to bla(CTX-M) via insertion sequences, was located between two IS26 elements oriented in the opposite direction, composing an IS26-composite transposon. CONCLUSIONS: An IS26-composite transposon appears to be the main vehicle for dissemination of fosA3 in E. coli and K. pneumoniae of diverse clones.

Distribution of mcr genes among carbapenem-resistant Enterobacterales clinical isolates: high prevalence of mcr-positive Enterobacter cloacae complex in Seoul, Republic of Korea.

Colistin is often used as a drug of last resort against infections caused by multi-drug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales (CRE). Recently, the acquisition of mobile colistin resistance (mcr) genes by CRE has become a cause for concern. This study investigated the prevalence of mcr genes in CRE isolates in Seoul, Republic of Korea. In total, 3675 CRE strains were collected from patients between 2018 and 2019, and initially screened for mcr genes using multiplex polymerase chain reaction assays. Upon the identification of mcr-harbouring strains, colistin susceptibility tests, identification of carbapenemase and ß-lactamase genes, and plasmid replicon typing were performed. Clonal analysis was conducted using pulsed-field gel electrophoresis. mcr genes were detected in 2.2% (80/3675) of CRE strains. There were three mcr-1 carriers, one mcr-4.3 carrier, one mcr-4.3/mcr-9 carrier, 58 mcr-9 carriers, one mcr-9/mcr-10 carrier and 16 mcr-10 carriers among various Enterobacterales species, of which 60 were Enterobacter cloacae complex (ECC) strains. The prevalence of mcr genes in ECC strains was 20.5%. Molecular detection confirmed that 21.3% and 13.8% of mcr-harbouring strains shared blaNDM-1 or blaKPC-2, respectively. In addition, an IncHI2 replicon was identified in 71.7% of mcr-9 strains. Comparative analysis revealed not only a notable diversity of mcr carriers, but also clonal spreading or nosocomial outbreaks of some ECC strains. These findings revealed a silent distribution of mcr genes in CRE strains with high genetic heterogeneity in Seoul, underscoring the urgent need for timely intervention to control and prevent mcr dissemination.

Dissemination of an international high-risk clone of Escherichia coli ST410 co-producing NDM-5 and OXA-181 carbapenemases in Seoul, Republic of Korea.

The rapid increase in carbapenemase-producing Enterobacterales is a global health concern. During 2017-2020, a total of 44 Escherichia coli isolates co-harbouring blaNDM-5 and blaOXA-181 were collected from patients at 17 hospitals in Seoul and characterized based on antimicrobial susceptibility, resistance genes and plasmid replicons detected using polymerase chain reaction (PCR). Clonal relatedness was estimated using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). All isolates had an identical multidrug resistance profile, including resistance to carbapenems, cephalosporins, ciprofloxacin, tetracycline, and trimethoprim/sulfamethoxazole, and susceptibility to amikacin, colistin, and tigecycline. Resistance genes (blaCTX-M-15, blaCMY-2, blaTEM-1B, blaOXA-1, aac(6')-Ib-cr, and qnrS) and plasmid replicons (IncFIA, IncFIB, and IncX3) was observed in almost all isolates. All isolates belonged to ST410 and were genetically similar (>88% similarity), with some PFGE types shared among isolates from different hospitals. Analysis of the whole genome revealed that the isolates clustered together with other strains of the international high-risk clone ST410 B4/H24RxC from other countries. These findings underline the ongoing spread of the high-risk clone of NDM-5- and OXA-181-producing E. coli ST410 B4/H24RxC among hospitals in Seoul. Continuous monitoring and implementation of infection control measures are crucial to track and prevent further spread of these resistant strains.

Identification of an extensively drug-resistant Escherichia coli clinical strain harboring mcr-1 and blaNDM-1 in Korea.

The development of colistin resistance in carbapenem-resistant strains poses a serious public health problem. In this study, we collected 249 carbapenem-resistant Escherichia coli isolates from patients in Seoul in 2018, and screened all isolates for colistin resistance and for the presence of mobile colistin resistance (mcr) genes. Colistin-resistant strains were further analyzed using multilocus sequence typing, antimicrobial susceptibility testing, detection of antibiotic resistance determinants, plasmid transconjugation, and whole-genome sequencing. Three of the 249 carbapenem-resistant isolates were resistant to colistin, and mcr-1 was detected in one isolate (SECR18-0888), which belonged to sequence type 156 and was resistant to all antibiotics tested except tigecycline. The mcr-1.1 gene was located on an ~62 kb self-transferable IncI2 plasmid along with the blaCTX-M-55 gene, and the blaNDM-1, blaTEM, qepA1, and rmtB genes were additionally detected in SECR18-0888. As an extensively drug-resistant E. coli strain producing MCR-1 and NDM-1 was identified in Korea for the first time, continued monitoring of colistin resistance in carbapenem-resistant Enterobacteriaceae should be reinforced.

Comparative Evaluation of Seegene Allplex Gastrointestinal, Luminex xTAG Gastrointestinal Pathogen Panel, and BD MAX Enteric Assays for Detection of Gastrointestinal Pathogens in Clinical Stool Specimens.

CONTEXT.­: Infectious gastroenteritis is caused by various pathogens, including bacteria, viruses, and parasites. OBJECTIVE.­: To compare the performance of Seegene Allplex Gastrointestinal (24 targets: 13 bacteria, 5 viruses, and 6 parasites in 4 panels), Luminex xTAG Gastrointestinal Pathogen Panel (15 targets: 9 bacteria, 3 viruses, and 3 parasites), and BD MAX Enteric panel (5 bacteria and 3 parasites). We estimated the agreement among 3 molecular assays. DESIGN.­: A total of 858 stool samples (554 bacterial/parasite and 304 viral pathogens) were included. A consensus positive/negative was defined as concordant results from at least 2 tests. To evaluate the agreement among the assays, κ value was calculated. RESULTS.­: The overall positive percentage agreements of Seegene, Luminex, and BD MAX were 94% (258 of 275), 92% (254 of 275), and 78% (46 of 59), respectfully. For Salmonella, Luminex showed low negative percentage agreement because of frequent false positives (n = 31) showing low median fluorescent intensity. For viruses, positive/negative percentage agreements of Seegene and Luminex were 99%/96% and 93%/99%, respectively. Compared with routine microbiology testing, Seegene, Luminex, and BD MAX additionally identified 39, 40, and 12 pathogens, respectively. Sixty-one cases (16 cases with Seegene, 51 cases with Luminex, and 1 case with BD MAX) showed positive results for multiple pathogens, but only 3 were consensus positive. CONCLUSIONS.­: These multiplex molecular assays appear to be promising tools for the detection and identification of multiple gastrointestinal pathogens simultaneously. However, careful interpretation of positive results for multiple pathogens is required.

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 mechanisms of decreased susceptibility to carbapenems in Klebsiella pneumoniae isolates.

In this study, we examined the prevalence of and mechanisms of decreased susceptibility to either imipenem or meropenem in Klebsiella pneumoniae isolates. A total of 230 clinical isolates of K. pneumoniae were collected from 13 clinical laboratories from a nationwide distribution. The MICs of imipenem and meropenem were determined by the agar dilution method. To characterize the isolates with decreased susceptibility to carbapenems (MICs of >2 microg/mL), we performed polymerase chain reaction amplification of a variety of beta-lactamase genes, isoelectric focusing, and outer membrane profile analysis using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry. Three isolates (BD6, BD8, and KN16) exhibited decreased susceptibility to carbapenems with imipenem MICs of 1, 4, and 8 microg/mL and meropenem MICs of 4, 8, and 4, respectively. Isolate BD6 produced bla(TEM-1), bla(SHV-12), and bla(OXA-17); isolate BD8 produced bla(GES-3), bla(SHV-12), and bla(OXA-17); and isolate KN16 produced bla(TEM-11), bla(SHV-12), and bla(DHA-1). In all the 3 isolates, OmpK35 porin was not expressed, and in 1 isolate (KN16), OmpK36 was not expressed either. The prevalence of decreased susceptibility to carbapenems was low (1.3%), and none of them showed overt resistance to carbapenems. Decreased susceptibility to carbapenems can occur in K. pneumoniae when bla(GES-3), bla(TEM-11), bla(SHV-12), bla(OXA-17), and/or bla(DHA-1) are produced in combination with porin loss. In addition, to our knowledge, this is the 1st report of bla(OXA-17) in Enterobacteriaceae.

Evaluation of Phoenix Automated Microbiology System for detecting extended-spectrum beta-lactamases among chromosomal AmpC-producing Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, and Serratia marcescens.

We evaluated the BD Phoenix Extended-Spectrum beta-Lactamase (ESBL) detection test among chromosomal AmpC-producing Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, and Serratia marcescens. The study was conducted on 72 non-repetitive ESBL producers (33 E. cloacae, 13 E. aerogenes, 14 C. freundii, and 12 S. marcescens) and 77 ESBL non-producers (33 E. cloacae, 9 E. aerogenes, 6 C. freundii, and 29 S. marcescens). The organisms were selected as suspected ESBL-producers based on the double disk synergy test and confirmed by PCR amplification of blaTEM-1, blaSHV-1, blaCTX-M-1, blaCTX-M-2, and blaCTX-M-9. The Phoenix ESBL test, using a 5-well confirmatory test and the BDXpert system, was evaluated. Of the 72 isolates identified as ESBL-producers based on the DDST, 46 isolates harbored CTX-M-type enzymes, 21 harbored TEM type enzymes, and 31 harbored SHV enzymes. The Phoenix system identified ESBL only in 15 isolates. Of the 77 ESBL non-producers, ths Phoenix system identified ESBL in 4 isolates, 3 of which were confirmed to be ESBL-producers. In this study, the Phoenix system was highly specific (76/77, 98.7%), and it identified 3 additional ESBL-producers that were not detected by DDST. However, the Phoenix system's sensitivity was very low (15/72, 20.8%). Considering the increasing prevalence of ESBL production among AmpC-producers, the BD Phoenix system could not be considered a reliable stand-alone ESBL detection method for the strains tested in our study.

A fluorogenic substrate of beta-lactamases and its potential as a probe to detect the bacteria resistant to the third-generation oxyimino-cephalosporins.

We devised and synthesized a fluorogenic substrate of ß-lactamases as a probe to detect the activity of the enzymes. Fluorescence of the probe emitted upon treatment of a ß-lactamase and increased proportionally to the concentration of the enzyme, demonstrating its sensing property for the activity of the enzyme. We also showed that the probe could be utilized to assay the enzyme and to determine kinetic parameters of the enzyme. Moreover, the probe was able to detect resistance to the third-generation oxyimino-cephalosporin-derived antibiotics such as cefotaxime and ceftazidime. In particular, the probe could identify the ceftazidime-resistance in bacteria that was not detectable using conventional pH-sensing materials, indicating the practical utility of the probe.

Prevalence and characteristics of Escherichia coli sequence type 131 and its H30 and H30Rx subclones: a multicenter study from Korea.

We investigated the prevalence and characteristics of Escherichia coli sequence type 131 (ST131) and its subclones among 268 E. coli isolates. The isolates were collected from 21 Korean hospitals without use of selection criteria and were screened for ST131 status by PCR. ST131 isolates were characterized for extended-spectrum ß-lactamase variants, fluoroquinolone resistance genes, plasmid addiction systems, and replicon types. The collection's 57 identified ST131 isolates (21% of 268) were distributed disproportionately by clonal subset, as follows: 21 (37%) H30Rx, 27 (47%) H30 non-Rx, and 8 (14%) non-H30. Most (93%) ST131 isolates were ciprofloxacin resistant, and all H30 isolates had the same 5 nonsynonymous mutations in gyrA, parC, and parE. Twenty (95%) of H30Rx isolates harbored CTX-M-15, whereas only 14 (52%) of H30 non-Rx isolates harbored CTX-M-14 or CTX-M-27. Most (97%) ST131 isolates harbored IncF plasmids, but vagCD was confined exclusively to H30Rx. Our findings suggest that the distinctive characteristics of H30Rx isolates could have contributed to this subclone's recent epidemiologic success.

Genotypes of Ciprofloxacin-Resistant Klebsiella pneumoniae in Korea and Their Characteristics According to the Genetic Lineages.

We investigated the molecular genotypes of ciprofloxacin-resistant Klebsiella pneumoniae and their characteristics according to the genetic lineages. For 160 K. pneumoniae collected in 2013, ciprofloxacin minimum inhibitory concentrations (MICs) were determined by agar dilution method. The genotypes of ciprofloxacin-resistant K. pneumoniae isolates were determined by multilocus sequence typing (MLST) and wzi gene typing. The presence of plasmid-mediated resistance determinants [qnrA, qnrB, qnrS, aac(6')-Ib-cr, blaCTX-M, and blaSHV] was investigated. The gyrA and parC genes were sequenced. Fifty-seven isolates showed ciprofloxacin resistance. By MLST, four major sequence types (STs) or clonal complexes (CCs), that is, ST307, CC11, CC147, and ST15, were found and the two most prevalent STs were ST307 (14/57, 24.6%) and ST11 (12/57, 21.1%). By wzi gene sequencing, 46 of the 57 isolates could be differentiated. All the ST307 isolates had an identical wzi sequence and harbored qnrB. The majority of them harbored aac(6')-Ib-cr (85.7%) and CTX-M-15 (92.9%). In contrast, 12 ST11 isolates were divided into five sublineages by wzi sequence and qnrB, qnrS, and aac(6')-Ib-cr were carried by nine, seven, and three isolates, respectively. They harbored SHV-type extended-spectrum ß-lactamase more frequently than CTX-M-15 (nine and four isolates, respectively). The prevalence of CTX-M-15, qnrB1, and aac(6')-Ib-cr was significantly higher in ST307 than in ST11 (p=0.003, p=0.000, and p=0.002, respectively). Both clones had identical amino acid substitution in gyrA (S83I) and parC (S80I). K. pneumoniae ST307 and ST11 were the two most common clones, and the ST307 isolates were highly homogeneous, suggesting their recent emergence.

Rapid detection of Gram-negative bacteria and their drug resistance genes from positive blood cultures using an automated microarray assay.

We evaluated the performance of the Verigene Gram-negative blood culture (BC-GN) assay (CE-IVD version) for identification of Gram-negative (GN) bacteria and detection of resistance genes. A total of 163 GN organisms (72 characterized strains and 91 clinical isolates from 86 patients) were tested; among the clinical isolates, 86 (94.5%) isolates were included in the BC-GN panel. For identification, the agreement was 98.6% (146/148, 95% confidence interval [CI], 92.1-100) and 70% (7/10, 95% CI, 53.5-100) for monomicrobial and polymicrobial cultures, respectively. Of the 48 resistance genes harbored by 43 characterized strains, all were correctly detected. Of the 19 clinical isolates harboring resistance genes, 1 CTX-M-producing Escherichia coli isolated in polymicrobial culture was not detected. Overall, BC-GN assay provides acceptable accuracy for rapid identification of Gram-negative bacteria and detection of resistance genes, compared with routine laboratory methods despite that it has limitations in the number of genus/species and resistance gene included in the panel and it shows lower sensitivity in polymicrobial cultures.

Clonal spread of catalase-negative ST5/SCCmec II Staphylococcus aureus carrying the staphylococcal enterotoxin A (sea), staphylococcal enterotoxin b (seb), and toxic shock toxin (tst) virulence genes.

17 catalase-negative methicillin-resistant Staphylococcus aureus (MRSA) isolates were recovered from respiratory specimens of patients at a 700-bed hospital in Korea. The goal of this study was to determine the molecular characteristics of catalase-negative MRSA strains in Korea for the first time. Characteristics that we explored included kat A gene mutation sequence, sequence type, staphylococcal cassette chromosome (SCC) mec subtype classification, and toxin gene profiles. All 17 isolates showed similar pulsed field gel electrophoresis (PFGE) pattern. Four mutations were identified in the kat A gene of a representative catalase-negative MRSA strain: A602G causing a histidine 201 to arginine change, A695T causing a glutamic acid 232 to valine change, T778A causing a tryptophan 260 to arginine change, and G1438A causing a glycine 480 to serine change. Previous studies suggest that the A695T and T778A mutations may have strong effects on the catalase activity of catalase-negative MRSA. The sequence type (ST) and SCCmec type of this isolate were ST 5 and SCCmec type II, respectively. All 17 isolates harbored toxic shock toxin (tst), staphylococcal enterotoxin A (sea), and staphylococcal enterotoxin B (seb) virulence genes. The mortality rate of the present study was 11.8%, suggesting that the clinical relevance of catalase-negative MRSA requires further study in the future.

Rates of fecal transmission of extended-spectrum ß-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 ß-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 (bioMérieux, 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.