Comparative analyses of the faecal resistome against ß-lactam and quinolone antibiotics in humans and livestock using metagenomic sequencing.

To assess the prevalence and abundance of antibiotic resistance genes in human and livestock gut microbiomes, 87 humans (healthy individuals and patients with Clostridioides difficile infection (CDI)) and 108 livestock (swine, cattle, and chickens) were enrolled. Gut microbiomes and fluoroquinolone-resistant Escherichia coli isolates were sequenced, and mobile genetic elements adjacent to the ß-lactamase (bla) and transferable quinolone resistance (qnr) genes were compared using metagenomic contigs. Each group of humans and livestock exhibited distinctive microbiota and resistome compositions in the gut. Concerning the resistome of bla and qnr, the prevalence rates between chickens and patients with CDI were the most similar (R2 = 0.46); blaTEM, blaOXA, blaCTX-M, and qnrS were highly prevalent in both groups. According to genomic and phylogenetic analyses, blaCTX-M and blaOXA expressed lineage specificity to either humans or livestock, while qnrS and blaTEM displayed a shared lineage between humans and livestock. A qnrS1 mobilome comprising five genes, including two recombinases, a transposase, and a plasmid gene, is commonly found in human and chicken gut microbiomes. Humans and chickens showed the most similar gut resistomes to ß-lactams and quinolones. QnrS and blaTEM displayed especially strong co-occurrence between the guts of humans and livestock.

Rapid and specific detection of Trichophyton rubrum and Trichophyton mentagrophytes using a loop-mediated isothermal amplification assay.

Trichophyton rubrum and Trichophyton mentagrophytes are the main causative pathogens of onychomycosis. However, the sensitivity and specificity of conventional microscopic tests are insufficient for reliable diagnoses of onychomycosis. In this study, we developed loop-mediated isothermal amplification (LAMP) assays for the rapid and specific identification of the two major Trichophytons spp. We designed LAMP primers targeting the internal transcribed spacer 1 region of the T. rubrum and T. mentagrophytes. Through rigorous optimization of the reaction conditions, we defined a universal reaction condition for both LAMP assays.

Development of reverse-transcription loop-mediated isothermal amplification assays for point-of-care testing of human influenza virus subtypes H1N1 and H3N2.

Influenza A virus (IAV) is the most widespread pathogen causing human respiratory infections. Although polymerase chain reaction (PCR)-based methods are currently the mostcommonly used tools for IAV detection, PCR is not ideal for point-of-care testing. In thisstudy, we aimed to develop a more rapid and sensitive method than PCR-based tools todetect IAV using loop-mediated isothermal amplification (LAMP) technology. We designedreverse-transcriptional (RT)-LAMP primers targeting the hemagglutinin gene. RNAs fromreference H1N1 and H3N2 showed specific RT-LAMP signals with the designed primers.We optimized the reaction conditions and developed universal reaction conditions for bothLAMP assays. Under these conditions, the detection limit was 50 copies for both RT-LAMPassays. There was no non-specific signal to 19 non-IAV respiratory viruses, such as influenza B virus, coronaviruses, and respiratory syncytial viruses. Regarding the reaction time, apositive signal was detected within 25 min after starting the reaction. In conclusion, ourRT-LAMP assay has high sensitivity and specificity for the detection of the H1 and H3 subtypes, making it suitable for point-of-care IAV testing.

Genetic Relatedness of 5-Year Isolates of Clostridioides difficile Polymerase Chain Reaction Ribotype 017 Strains in a Hospital.

The objective of this study was to analyse the genetic relatedness of Clostridioides difficile polymerase chain reaction ribotype 017 (RT017) strains from patients with hospital-acquired C. difficile infection (HA-CDI) in a hospital with a high RT017 prevalence. From 2009 to 2013, 200 RT017 strains (26.8%) were collected from 745 HA-CDI patient isolates. They comprised 64 MLVA types, and 197 (98.5%) strains were genetically related to 5 clonal complexes (CCs). The largest cluster, CC-A, included 163 isolates of 40 MLVA types. CC-A accounted for 20% of RT017 strains in 2009 and sharply increased to 94.9% in 2010, 94% in 2011, 86.2% in 2012, and 73.5% in 2013. The other 4 CCs included 20 isolates with 7 MLVA types. The resistance rates of antimicrobials were as follows: clindamycin 100%, moxifloxacin 99%, rifaximin 88.5%, and vancomycin 1%. All isolates were susceptible to metronidazole and piperacillin/tazobactam. Comparing antibiotic resistance among CCs, the geometric mean of the minimum inhibitory concentrations of moxifloxacin, vancomycin, and piperacillin/tazobactam were significantly higher for CC-A isolates than for the other CCs. RT017 clones constantly evolved over the 5 years studied with regard to genetic relatedness. The levels of antibiotic resistance may contribute to the persistence of organisms in the institution.

High fecal carriage of blaCTX-M, blaCMY-2, and plasmid-mediated quinolone resistance genes among healthy Korean people in a metagenomic analysis.

To characterize the carriage of antibiotic resistance genes (ARGs) in the gut microbiome of healthy individuals. Fecal carriage of ARGs was investigated in 61 healthy individuals aged 30 to 59 years through whole metagenome sequencing of the gut microbiome and a targeted metagenomic approach. The number of ARGs in the gut microbiome was counted and normalized per million predicted genes (GPM). In the Korean population, the resistome ranged from 49.7 to 292.5 GPM (median 89.7). Based on the abundance of ARGs, the subjects were categorised into high (> 120 GPM), middle (60‒120 GPM), and low (< 60 GPM) ARG groups. Individuals in the high ARG group tended to visit hospitals more often (P = 0.065), particularly for upper respiratory tract infections (P = 0.066), and carried more blaCTX-M (P = 0.008). The targeted metagenome approach for bla and plasmid-mediated quinolone resistance (PMQR) genes revealed a high fecal carriage rate; 23% or 13.1% of the subjects carried blaCTX-M or blaCMY-2, respectively. Regarding PMQR genes, 59% of the subjects carried PMQR, and 83% of them harboured 2‒4 PMQR genes (qnrB 44.3%, qnrS 47.5% etc.). The presence of blaCTX-M correlated with ARG abundance in the gut resistome, whereas PMQR genes were irrelevant to other ARGs (P = 0.176). Fecal carriage of blaCTX-M and PMQR genes was broad and multiplexed among healthy individuals.

Quantitative characterization of Clostridioides difficile population in the gut microbiome of patients with C. difficile infection and their association with clinical factors.

Objective was to analyse bacterial composition and abundance of Clostridioides difficile in gut microbiome of patients with C. difficile infection (CDI) in association with clinical characteristics. Whole metagenome sequencing of gut microbiome of 26 CDI patients was performed, and the relative abundance of C. difficile and its toxin genes was measured. Clinical characteristics of the patients were obtained through medical records. A strong correlation between the abundance of C. difficile and tcdB genes in CDI patients was found. The relative abundance of C. difficile in the gut microbiome ranged from undetectable to 2.8% (median 0.089). Patients with fever exhibited low abundance of C. difficile in their gut, and patients with fewer C. difficile organisms required long-term anti-CDI treatment. Abundance of Bifidobacterium and Bacteroides negatively correlated with that of C. difficile at the genus level. CDI patients were clustered using the bacterial composition of the gut: one with high population of Enterococcus (cluster 1, n = 12) and another of Bacteroides or Lactobacillus (cluster 2, n = 14). Cluster1 showed significantly lower bacterial diversity and clinical cure at the end of treatment. Additionally, patients with CDI exhibited increased ARGs; notably, blaTEM, blaSHV and blaCTX-M were enriched. C. difficile existed in variable proportion of the gut microbiome in CDI patients. CDI patients with Enterococcus-rich microbiome in the gut had lower bacterial diversity and poorer clinical cure.

Molecular Epidemiology of Ciprofloxacin-Resistant Escherichia coli Isolated from Community-Acquired Urinary Tract Infections in Korea.

BACKGROUND: Escherichia coli is the predominant causative pathogen for community-acquired urinary tract infections (UTIs), and the increase in fluoroquinolone-resistant E. coli is of great concern in Korea. The objectives of this study were to investigate the genotypic characteristics and molecular epidemiology of ciprofloxacin-resistant (CIP-R) E. coli isolated from community-acquired UTIs in Korea. MATERIALS AND METHODS: E. coli samples isolated from the blood or urine were collected from patients with community-acquired acute pyelonephritis aged 15 years and more who were admitted to 12 Korean hospitals from 1st April 2010 to 29th February 2012. Phylogenetic typing, multilocus sequence typing, and molecular characterization of ß-lactamase and plasmid-mediated quinolone resistance determinants were performed for CIP-R E. coli isolates. RESULTS: A total of 569 E. coli isolates were collected, and 122 (21.4%) isolates were CIP-R isolates. The most prevalent sequence type (ST) was ST131 (28.7%, 35/122), followed by ST393 (14.7%, 18/122), ST1193 (13.1%, 16/122), ST38 (9.0%, 11/122), and ST405 (8.2%, 10/122). The antimicrobial resistance rates of ST131 to cefepime (22.9%, 8/35), ST38 to gentamicin (100%, 11/11), and ST405 to cefotaxime (66.7%, 6/9) were significantly higher than the resistance rates of all other STs combined. Notably, 40% (4/10) of ST405 clones produced extended-spectrum ß-lactamases and were co-resistant to trimethoprim/sulfamethoxazole. aac(6')-1b-cr (20%, 7/35) and CTX-M-14 (40%, 4/10) were more frequently observed in ST131 and ST405 compared with other clones, respectively. CONCLUSIONS: Among the CIP-R uropathogenic E. coli isolates in this study, ST131, ST38, and ST405 were specifically associated with antimicrobial resistance.

Ribotype variability of Clostridioides difficile strains in patients with hospital-acquired C. difficile infections, community-acquired C. difficile infections, and colonization with toxigenic and non-toxigenic strains of C. difficile.

There have been few available data that presented a direct comparison between polymerase chain reaction ribotype (RT) distribution of Clostridioides difficile strains from C. difficile infection (CDI) and colonization. To understand the epidemiology of CDI in a hospital setting, we compared RTs of C. difficile strains from hospital-acquired CDI (HA-CDI) and toxigenic colonization and from community-acquired CDI (CA-CDI) and non-toxigenic colonization using the stool samples submitted for C. difficile cultures at an institution during 2009, 2012, and 2014. Overall, 721 C. difficile strains were identified from 607 patients. Among them, 450 (62.4%) were HA-CDI, 20 (2.8%) were CA-CDI, 126 (17.5%) were toxigenic colonization, and 125 (17.3%) were non-toxigenic colonization. RT018, RT017, RT002, RT015, and RT001 isolates were the most prevalent RTs in HA-CDI, and they comprised 74.9% of the total HA-CDI isolates but accounted for 60.4% of isolates from toxigenic colonization. In total, 32 strain compromising 18 RTs from HA-CDI (7.1%) were not seen among the toxigenic colonization group, and 3 RTs with 5 strains from toxigenic colonization were not seen among the HA-CDI group. The distribution of RTs was the most diverse in CA-CDI and the least diverse in HA-CDI. Although 5 RT strains, which were prevalent in HA-CDI, comprised 40% of CA-CDI, 5 isolates (25%) revealed unknown RTs, which were uncommon in HA-CDI or toxigenic colonization. In 12 patients with both episodes of CDI and toxigenic colonization, 8 had 2 isolates with different RTs and 4 had isolates with identical RTs. In conclusion, although RT017 and RT018 were the most common in HA-CDI and toxigenic colonization, C. difficile strains from toxigenic colonization were more diverse than those from HA-CDI.

Change in antimicrobial susceptibility and PCR ribotypes of Clostridioides difficile in a hospital over 5 years: Correlation analysis with antimicrobial consumption.

Clostridioides difficile infection (CDI) is a major concern in hospital settings. Antimicrobial resistance is a key contributing factor in CDI outbreaks. This study analysed the antimicrobial susceptibility and PCR ribotypes (RTs) of 745 C. difficile isolates collected at a single institution over 5 years. Seventeen known RTs were identified in 643 isolates (86.3%), of which RTs 018, 017, 015, 001 and 002 were the most prevalent. Reduced susceptibility to metronidazole (MTZ) and vancomycin (VAN) was rare (2.0% and 0.7%, respectively). Resistance to rifaximin (RFX), moxifloxacin (MXF) and clindamycin (CLI) was high in multiple RTs (29.3%, 67.0% and 69.4% of total isolates, respectively). Antimicrobial susceptibility varied among RTs. Whilst non-susceptibility to VAN, RFX, MXF, CLI and piperacillin/tazobactam (TZP) mostly occurred in commonly identified RTs, MTZ resistance was observed in diverse RTs. Correlation analysis between the MICs of the six antimicrobials for annual isolates and antimicrobial consumption in the hospital by year showed variable degrees of correlation; significant positive correlation for TZP (P = 0.037), significant negative correlation for VAN (P < 0.001) and no significant correlation for the other antimicrobials. MIC creep of TZP occurred during the study period with the appearance of 19 isolates with TZP intermediate-resistance mostly in 2013 (89.5%; 17/19), and three RTs containing TZP-intermediate-resistant isolates, including RT015 (n = 4), RT002 (n = 12) and RT112 (n = 1), increased over time (P = 0.010). These findings suggest an association of antibiotic consumption and resistant C. difficile strains and question TZP use for limiting CDI in hospitals.

Prevalence, genetic relatedness and antibiotic resistance of hospital-acquired clostridium difficile PCR ribotype 018 strains.

Clostridium difficile infection (CDI) is a major healthcare-associated infection. The aim of this study was to investigate the genetic relatedness of the endemic C. difficile PCR ribotype 018 strains in an institution and changes to their characteristics during a five-year period. A total of 207 isolates from inpatients at Hanyang University Hospital from 2009 to 2013 were analysed using multilocus variable-number tandem-repeat analysis (MLVA). Minimum inhibitory concentrations (MICs) of several antibiotics were determined. In total, 204 (98.6%) were genetically related, with a summed tandem-repeat distance (STRD) ≤ 10. Minimum-spanning-tree analysis identified 78 MLVA types, categorized into six clonal complexes (CCs). The largest cluster, CC-I, included 51 MLVA types from 148 isolates (71.5%) and the second largest cluster, CC-II, included 10 MLVA types from 36 isolates (17.4%). Resistance rates for antibiotics were: clindamycin (CLI), 97.6%; moxifloxacin (MXF), 98.6%; vancomycin (VAN), 1.4%; and rifaximin (RFX), 8.2%. All isolates were susceptible to piperacillin/tazobactam (TZP) and metronidazole (MTZ). Comparing the MICs of antibiotics for the isolates each year from 2009 to 2013, MICs of antibiotics that promote CDI, such as CLI, MXF, TZP and RFX, increased over the five-year period (P-value by Kruskal-Wallis test: < 0.0001, <0.0001, <0.0001, and <0.0001 respectively); however, MICs of VAN or MTZ, antibiotics for treatment of CDI, did not increase or decreased over the same time period (P-value by Kruskal-Wallis test: 0.166, <0.0001). C. difficile RT018 isolates in a tertiary hospital over a five-year period presented a close clonal relationship. MICs of antibiotics promoting CDI increased with this clonal expansion.

Usefulness of Blood Cultures and Radiologic Imaging Studies in the Management of Patients with Community-Acquired Acute Pyelonephritis.

BACKGROUND: The objective of this study was to examine the usefulness of blood cultures and radiologic imaging studies for developing therapeutic strategies in community-acquired acute pyelonephritis (CA-APN) patients. MATERIALS AND METHODS: We prospectively collected the clinical data of CA-APN patients who visited 11 hospitals from March 2010 to February 2011. RESULTS: Positive urine and blood cultures were obtained in 69.3% (568/820) and 42.7% (277/648), respectively, of a total of 827 CA-APN patients. Blood culture identified the urinary pathogen in 60 of 645 (9.3%) patients for whom both urine and blood cultures were performed; the organisms isolated from urine were inconsistent with those from blood in 11 and only blood cultures were positive in 49 patients. Final clinical failure was more common in the bacteremic patients than the non-bacteremic ones (8.0% vs. 2.7%, P = 0.003), as was hospital mortality (3.6% vs. 0.3%, P = 0.003). Likewise, durations of hospitalization and fever were significantly longer. Bacteremia was independent risk factor for mortality (OR 9.290, 1.145-75.392, P = 0.037). With regard to radiologic studies, the detection rate of APN was 84.4% (445/527) by abdominal computed tomography and 40% (72/180) by abdominal ultrasonography. Eighty-one of 683 patients (11.9%) were found to have renal abscess, perinephric abscess, urolithiasis, hydronephorosis/hydroureter or emphysematous cystitis, which could potentially impact on clinical management. Patients with Pitt score ≥ 1, flank pain or azotemia were significantly more likely to have such structural abnormalities. CONCLUSION: Blood cultures are clinically useful for diagnosis of CA-APN, and bacteremia is predictive factor for hospital mortality. Early radiologic imaging studies should be considered for CA-APN patients with Pitt scores ≥1, flank pain or azotemia.

Susceptibility of Escherichia coli from community-acquired urinary tract infection to fosfomycin, nitrofurantoin, and temocillin in Korea.

With increase of multi-drug resistant Escherichia coli in community-acquired urinary tract infections (CA-UTI), other treatment option with a therapeutic efficacy and a low antibiotic selective pressure is necessary. In this study, we evaluated in vitro susceptibility of E. coli isolates from CA-UTI to fosfomycin (FM), nitrofurantoin (NI), temocillin (TMO) as well as trimethoprim-sulfamethoxazole (SMX), ciprofloxacin (CIP) and cefepime (FEP). The minimal inhibitory concentrations were determined by E-test or agar dilution method according to the Clinical and Laboratory Standards Institute guidelines, using 346 E. coli collected in 12 Korean hospitals from March 2010 to February 2011. FM, NI and TMO showed an excellent susceptibility profile; FM 100% (346/346), TMO 96.8% (335/346), and NI 99.4% (344/346). Conversely, resistance rates of CIP and SMX were 22% (76/346) and 29.2% (101/349), respectively. FEP still retained an activity of 98.5%. In Korea, NI and TMO in addition to FM are a good therapeutic option for uncomplicated CA-UTI, especially for lower UTI.

FoxO1 is a negative regulator of FSHß gene expression in basal and GnRH-stimulated conditions in female.

The importance of forkhead box class O (FoxO) proteins in reproductive endocrinology has been confirmed by age-dependent infertility in females in a FoxO3a-knockout mouse model. In this study, FoxO1 was detected in gonadotropes in the anterior pituitary. Overexpression of FoxO1 in primary pituitary cells decreased FSHß gene expression in both basal and GnRH-stimulated conditions, and this result was replicated by the human FSHß promoter activity. Although direct binding of FoxO1 to FoxO-binding element (FBE) (at -124 to -119 bp of the human FSHß promoter) was not detected in an electrophoretic mobility shift assay, a DNA pull-down assay and transfection study using the mutant FBE reporter vector revealed that FBE is necessary in FSHß suppression by FoxO1, suggestive of other cofactor requirements. GnRH stimulated the phosphoinositide 3-kinase pathway, which induced posttranslational modification of FoxO1 and retained it in the cytoplasm. We also confirmed this result in primary cell cultures; most of the FoxO1 was detected in the cytoplasm when treated with GnRH but in the nucleus when the phosphoinositide 3-kinase pathway was inhibited. These findings suggest that FoxO1 is regulated by the GnRH signaling pathway and functions as a negative regulator of FSHß gene expression.

Clinical and Microbiologic Characteristics of Clostridium difficile Infection Caused by Binary Toxin Producing Strain in Korea.

BACKGROUND: Binary toxin-producing Clostridium difficile infections (CDI) are known to be more severe and to cause higher case fatality rates than those by binary toxin-negative isolates. There has been few data of binary toxin-producing CDI in Korea. Objective of the study is to characterize clinical and microbiological trait of CDI cause by binary-toxin producing isolates in Korea. MATERIALS AND METHODS: From September 2008 through January 2010, clinical characteristics, medication history and treatment outcome of all the CDI patients were collected prospectively. Toxin characterization, PCR ribotyping and antibiotic susceptibility were performed with the stool isolates of C. difficile. RESULTS: During the period, CDI caused by 11binary toxin-producing isolates and 105 toxin A & toxin B-positive binary toxin-negative isolates were identified. Comparing the disease severity and clinical findings between two groups, leukocytosis and mucoid stool were more frequently observed in patients with binary toxin-positive isolates (OR: 5.2, 95% CI: 1.1 to 25.4, P = 0.043; OR: 7.6, 95% CI: 1.6 to 35.6, P = 0.010, respectively), but clinical outcome of 2 groups did not show any difference. For the risk factors for acquisition of binary toxin-positive isolates, previous use of glycopeptides was the significant risk factor (OR: 6.2, 95% CI: 1.4 to 28.6, P = 0.019), but use of probiotics worked as an inhibitory factor (OR: 0.1, 95% CI: 0.0 to 0.8; P = 0.026). PCR ribotypes of binary toxinproducing C. difficile showed variable patterns: ribotype 130, 4 isolates; 027, 3 isolates; 267 and 122, 1 each isolate and unidentified C1, 2 isolates. All 11 binary toxin-positive isolates were highly susceptible to clindamycin, moxifloxacin, metronidazole, vancomycin and piperacillin-tazobactam, however, 1 of 11 of the isolates was resistant to rifaximin. CONCLUSIONS: Binary toxin-producing C. difficile infection was not common in Korea and those isolates showed diverse PCR ribotypes with high susceptibility to antimicrobial agents. Glycopeptide use was a risk factor for CDI by those isolates.

Clinical and microbiologic characteristics of tcdA-negative variant Clostridium difficile infections.

BACKGROUND: The tcdA-negative variant (A-B+) of Clostridium difficile is prevalent in East Asian countries. However, the risk factors and clinical characteristics of A-B+C. difficile infections (CDI) are not clearly documented. The objective of this study was to investigate these characteristics. METHODS: From September 2008 through January 2010, the clinical characteristics, medication history and treatment outcomes of CDI patients were recorded prospectively. Toxin characterization and antibiotic susceptibility tests were performed on stool isolates of C. difficile. RESULTS: During the study period, we identified 22 cases of CDI caused by tcdA-negative tcdB-positive (A-B+) strains and 105 cases caused by tcdA-positive tcdB-positive (A+B+) strains. There was no significant difference in disease severity or clinical characteristics between the two groups. Previous use of clindamycin and young age were identified as significant risk factors for the acquisition of A-B+ CDI (OR = 4.738, 95% CI 1.48-15.157, p = 0.009 and OR = 0.966, 95% CI 0.935-0.998, p = 0.038, respectively) in logistic regression.Rates of resistance to clindamycin were 100% and 69.6% in the A-B+ and A+B+ isolates, respectively (p = 0.006), and the ermB gene was identified in 17 of 21 A-B+ isolates (81%). Resistance to moxifloxacin was also more frequent in the A-B+ than in the A+B+ isolates (95.2% vs. 63.7%, p = 0.004). CONCLUSIONS: The clinical course of A-B+ CDI is not different from that of A+B+ CDI. Clindamycin use is a significant risk factor for the acquisition of tcdA-negative variant strains.

Epidemiology and clinical characteristics of Clostridium difficile infection in a Korean tertiary hospital.

In order to investigate the incidence, clinical and microbiologic characteristics of Clostridium difficile infection (CDI) in Korea, a prospective observational study was performed. From September 2008 through January 2010, all patients whose stool was tested for toxin assay A&B and/or C. difficile culture were studied for clinical characteristics. Toxin types of the isolates from stool were tested. The mean incidence of CDI per 100,000 patient-days was 71.6 by month (range, 52.5-114.0), and the ratio of CDI to antibiotic-associated diarrhea was 0.23. Among 200 CDI patients, 37.5% (75/200) was severe CDI based on severity score. Clinical outcome of 189 CDI was as followed; 25.9% (49/189) improved without treatment, 84.3% (118/140) achieved clinical cure and attributed mortality was 0.7% (1/140) with the treatment. Recurrence rate was 21.4% (30/140) and cure without recurrence was 66.4% (93/140). The most common type of toxin was toxin A-positive/toxin B-positive strain (77.5%), toxin A-negative/toxin B-positive strains or binary toxin-producing strains comprised 15.4% or 7.1%, respectively. In conclusion, the incidence of CDI in Korea is a little higher than other reports during the non-epidemic setting. We expect that the change of epidemiology and clinical severity in CDI can be evaluated based on these results.

Characteristics of plasmid-mediated quinolone resistance genes in extended-spectrum cephalosporin-resistant isolates of Klebsiella pneumoniae and Escherichia coli in Korea.

BACKGROUND: Quinolone resistance is frequently associated with extended-spectrum cephalosporin resistance in Enterobacteriaceae. METHODS: The characteristics of plasmid-mediated quinolone resistance (PMQR) genes [qnr genes, aac(6')-Ib-cr and qepA] in clinical isolates of Klebsiella pneumoniae and Escherichia coli resistant to extended-spectrum cephalosporin were studied. RESULTS: 5 and 4 of 95 E. coli isolates but 46 (86/187) and 6% (12/187) of K. pneumoniae had qnr and aac(6')-Ib-cr, respectively, and 8 K. pneumoniae contained both genes.qepA was not identified. qnrB, especially qnrB4, was the predominant qnr subtype in K. pneumoniae [94 (88 qnrB of 94 qnr) and 88% (77 qnrB4 of 88 qnrB), respectively], and presence of qnrB4 was closely related with DHA-1 beta-lactamase (99%). However, K. pneumoniae isolates with qnrB4 and bla(DHA-1) were clonally diverse. beta-Lactamases produced by PMQR-containing isolates were variable: CMY-1, CTX-M-14, CTX-M-15, DHA-1, OXA type, SHV-2a, and SHV-12. CONCLUSION: PMQR genes are widely distributed among clinical isolates of K. pneumoniae, and qnrB4 associated with bla(DHA-1) was the most common PMQR gene in Korea.

Risk factors and clinical features of infections caused by plasmid-mediated AmpC beta-lactamase-producing Enterobacteriaceae.

A case-control study was performed with the objective of analysing risk factors and clinical features of infections caused by plasmid-mediated AmpC beta-lactamase (plasmid AmpC)-producing Enterobacteriaceae. All patients infected with plasmid AmpC-producing Enterobacteriaceae in two tertiary care hospitals from December 2006 to August 2007 were included. Plasmid AmpC enzymes were characterised by isoelectric focusing, enzyme inhibition assay and enzyme-specific polymerase chain reaction. A total of 30 patients (20 with Klebsiella pneumoniae and 10 with Escherichia coli) were recruited prospectively. CMY-2 and DHA-1 were the most common plasmid AmpC in E. coli and K. pneumoniae, respectively. An independent risk factor for infection with plasmid AmpC-producing Enterobacteriaceae was the use of an oxyimino-cephalosporin within 1 month of plasmid AmpC infection [adjusted odds ratio (aOR), 10.8, 95% confidence interval (CI), 1.6-75.4; P=0.016], with the use of a urinary catheter showing borderline significance (aOR, 6, 95% CI 0.93-38.4; P=0.06). An independent risk factor for treatment failure at 72 h was infection due to plasmid AmpC-producing Enterobacteriaceae (aOR, 9.78, 95% CI 1.34-71.17; P=0.02). These results suggest that infections caused by plasmid AmpC-producing isolates significantly increase treatment failure at 72 h and that prior use of an oxyimino-cephalosporin is a risk factor for infections caused by plasmid AmpC-producing Enterobacteriaceae.

Association of QnrB determinants and production of extended-spectrum beta-lactamases or plasmid-mediated AmpC beta-lactamases in clinical isolates of Klebsiella pneumoniae.

Clinical isolates of Escherichia coli and Klebsiella pneumoniae producing extended-spectrum beta-lactamases or plasmid-mediated AmpC beta-lactamases were screened for qnrA and qnrB genes. QnrB was present in 54 of 54 DHA-1-producing K. pneumoniae isolates and 10 of 45 SHV-12-producing ones, suggesting that the distribution of plasmids conferring resistance to extended-spectrum cephalosporins and quinolones in clinical isolates of K. pneumoniae is widespread.

A nosocomial outbreak of Escherichia coli producing CTX-M-15 and OXA-30 beta-lactamase.

During a survey of the prevalent subtypes of extended-spectrum beta -lactamases in a university hospital in Korea, a nosocomial outbreak of Escherichia coli producing CTX-M-15 and OXA-30 beta -lactamases was detected. The outbreak comprised various infections, including bloodstream infections and colonization, and persisted for several months in various areas of the hospital.