The sul1 gene in Stenotrophomonas maltophilia with high-level resistance to trimethoprim/sulfamethoxazole

Emerging resistance to trimethoprim/sulfamethoxazole (SXT) poses a serious threat to the treatment of Stenotrophomonas maltophilia infections. We determined the prevalence and molecular characteristics of acquired SXT resistance in recent clinical S. maltophilia isolates obtained from Korea. A total of 252 clinical isolates of S. maltophilia were collected from 10 university hospitals in Korea between 2009 and 2010. Antimicrobial susceptibility was determined by using the CLSI agar dilution method. The sul1, sul2, and sul3 genes, integrons, insertion sequence common region (ISCR) elements, and dfrA genes were detected using PCR. The presence of the sul1 gene and integrons was confirmed through sequence analysis. Among the 32 SXT-resistant isolates, sul1 was detected in 23 isolates (72%), all of which demonstrated high-level resistance (≥64 mg/L) to SXT. The sul1 gene (varying in size and structure) was linked to class 1 integrons in 15 of the 23 isolates (65%) harboring this gene. None of the SXT-susceptible isolates or the SXT-resistant isolates with a minimum inhibitory concentration of 4 and 8 mg/L were positive for sul1. Moreover, the sul2, sul3, and dfrA genes or the ISCR elements were not detected. The sul1 gene may play an important role in the high-level SXT resistance observed in S. maltophilia.ope

Evaluation of the Xpert Clostridium difficile assay for the diagnosis of Clostridium difficile infection

Infection with Clostridium difficile is a growing concern because of the increasing prevalence and spread of nosocomial infections. Emergence of the hypervirulent 027/NAP1/BI strain is also notable. Existing diagnostic methods have low sensitivity or are time-consuming. Therefore, establishing a rapid and accurate microbiological diagnostic assay is needed. We evaluated the Xpert C. difficile assay (Xpert CD assay; Cepheid, USA) to detect toxigenic C. difficile. This assay is a real-time multiplex PCR assay that can be used to detect toxigenic C. difficile strains and differentiate the C. difficile presumptive 027/NAP1/BI strain. A total of 253 loose stool specimens were collected and toxigenic cultures, VIDAS C. difficile A & B assays (VIDAS CDAB assay; bioMérieux, France), and the Xpert CD assay were performed. In comparison to toxigenic cultures, the sensitivity, specificity, and positive and negative predictive values were 100%, 94.6%, 83.1%, and 100%, respectively, for the Xpert CD assay and 40.8%, 98.0%, 100%, and 88.9%, respectively, for VIDAS CDAB assay. Because of the low prevalence of the PCR ribotype 027 in Korea, the evaluation of the usefulness of the Xpert CD assay for screening for the 027 strain was limited. The Xpert CD assay provides great sensitivity in diagnosing toxigenic C. difficile infection. In addition, this method has excellent usability because it is simple and fast. KEYWORDS: Clostridium difficile, Enzyme immunoassay, Real-time PCRope

Nosocomial clustering of NDM-1-producing Klebsiella pneumoniae sequence type 340 strains in four patients at a South Korean tertiary care hospital

In November 2010, NDM-1-producing Klebsiella pneumoniae (NDMKP) was identified for the first time in South Korea from four patients with no history of traveling abroad who stayed for 21 to 205 days in a tertiary care hospital. All were sequence type (ST) 340 and had nearly identical XbaI pulsed-field gel electrophoresis (PFGE) patterns. The bla(NDM-1)-carrying plasmids were in the IncN group, with sizes ranging from 50 to 200 kb. These findings suggest that NDMKP had already been introduced into South Korea before this clustering was found. 22259206ope

First Outbreak of KPC-2-Producing Klebsiella pneumoniae Sequence Type 258 in a Hospital in South Korea

In this study, we report the first outbreak of KPC-2-producing Klebsiella pneumoniae isolates from three patients admitted to a neurosurgery department in a South Korean teaching hospital. Multilocus sequence typing showed that the isolates were identical to the previous KPC producers in South Korea and other countries, suggesting clonal spread.ope

Adjustment of Modified Carbapenem Inactivation Method Conditions for Rapid Detection of Carbapenemase-Producing Acinetobacter baumannii

Background: The existing modified carbapenem inactivation methods (mCIMs) recommended by the CLSI for detecting carbapenemase production have not been applicable for Acinetobacter baumannii. We evaluated the influence of matrices used in mCIMs and CIMTris on the stability of the disks for detecting carbapenemase producers and suggested optimal mCIM conditions for detecting carbapenemase-producing A. baumannii. Methods: Seventy-three A. baumannii isolates characterized for antimicrobial susceptibility and carbapenemase encoding genes were tested for carbapenemase production using mCIM and CIMTris. The influence of the matrices (Tryptic soy broth [TSB] and Tris-HCl) used in these methods on the stability of the meropenem (MEM) disk was also evaluated. The mCIM conditions were adjusted to enhance screening sensitivity and specificity for detecting carbapenemase-producing A. baumannii. Results: The matrices had an impact on the stability of the MEM disk after the incubation period (two or four hrs). TSB nutrient broth is an appropriate matrix for mCIM compared with Tris-HCl pH 7.6, which leads to the loss of MEM activity in CIMTris. The sensitivity and the specificity of the optimal mCIM were both 100%. Conclusions: We established optimal mCIM conditions for simple, accurate, and reproducible detection of carbapenemase-producing A. baumannii.ope

Molecular and Phenotypic Characteristics of 16S rRNA Methylase-producing Gram-negative Bacilli

BACKGROUND: Recently a novel plasmid-mediated resistant mechanism that conferred high-level resistance to aminoglycoside via methylation of 16S rRNA was reported. The aims of this study were to determine the prevalence of the 16S rRNA methylase genes and to characterize the coresistance to other antibiotics in Gram-negative bacilli. METHODS: Consecutive non-duplicate Gram-negative bacilli were isolated from clinical specimens at a Korean secondary- and tertiary-care hospital from July 2006 to June 2007. The antimicrobial susceptibility was tested by the CLSI agar dilution method,and PCR was performed to detect the 16S rRNA methylase genes in the arbekacin-resistant isolates. RESULTS: In Gram-negative bacilli, the proportions of 16S rRNA methylase gene-positive isolates were 5% (75/1,471) in the secondary-carehospital and 4% (48/1,251) in the tertiary-care hospital, and the positive rates by species were 1% Escherichiae coli 16% (10/1,062), Klebsiella pneumoniae 16% (75/460), K. oxytoca 2% (1/44), Citrobacter spp. 9% (7/82), Enterobacter spp. 2% (4/181), Serratia marcescens 6% (6/100), Proteus miriabilis 4% (2/57), Achromobacter xylosoxidans 20% (1/5), Pseudomonas aeruginosa < 1% (1/505), Acinetobacter spp. 10% (11/112), and Stenotrophomonas maltophilia 2% (1/66), respectively. Among 16S rRNA methylase-positive isolates from secondary- and tertiary-care hospitals, 93% (70/75) and 90% (43/48), respectively, were armA positive, and others, except one rmtA positive isolate, were positive for the rmtB gene, according to PCR results. The rates of ESBL-positive and cefoxitin-resistant K. pneumoniae were 59% and 92%,s respectively. In addition, 91% of 16S rRNA methylase-producing K. pneumoniae were positive for qnrB. There were no MBL producers among 16S rRNA methylase-producing Pseudomonas and Acinetobacter species. CONCLUSION: The novel aminoglycoside-resistant mechanisms involving16S rRNA methylase were prevalent and widely distributed among Gram-negative bacilli in Korea, and other resistance mechanisms were commonly associated with 16S rRNA methylase-mediated resistance in Koreaope

Antimicrobial Resistance of Neisseria gonorrhoeae Isolated in Korea

Neisseria gonorrhoeae is the causative agent of gonorrhea, one of the most important sexually transmitted diseases. The incidence of gonorrhea is still prevalent and about 50,000 new cases have been reported annually during the late 2000s in Korea. The antimicrobial resistance of N. gonorrhoeae is very prevalent and most isolates are multi-drug resistant to penicillin G, tetracycline, and fluoroquinolones. The incidence of penicillinase-producing N. gonorrhoeae (PPNG) decreased significantly, but high-level tetracycline-resistant N. gonorrhoeae (TRNG) increased recently. The minimum inhibitory concentrations (MICs) of ceftriaxone were within the susceptible range for all isolates, but MIC creep has been apparent and one cefixime-nonsusceptible isolate (0.5 µg/ml) was found. Spectinomycin-resistant isolates remain rare, but caution should be required when dealing with gonococcal pharyngitis.ope

국내 분리 Bacteroides fragilis군의 8년간 내성률 변화(1997-2004)

BACKGROUND: Bacteroides fragilis group organisms are the most frequently isolated anaerobes in human infections. Increasing resistance to various antimicrobial agents is a significant problem in choosing appropriate antimicrobial agents to treat anaerobic infections. Periodic monitoring of the regional resistance trends of B. fragilis group isolates is needed. METHODS: A total of 466 nonduplicate clinical isolates of B. fragilis group organisms (276 B. fragilis, 106 Bacteroides thetaiotaomicron, and 84 other B. fragilis group organisms) were collected during the 8-yr period from 1997 to 2004 in a Korean university hospital. Minimum inhibitory concentrations to various antimicrobial agents were determined by the CLSI agar dilution method. RESULTS: Eight isolates were resistant to imipenem. Additionally, the resistance rates to cefotetan were decreased in B. thetaiotaomicron, while those for clindamycin were significantly increased compared to the rates found in previous studies. Depending on species, resistance rates were 1-4% for imipenem, 1-6% for piperacillin-tazobactam, 4-11% for cefoxitin, 33-49% for piperacillin, 14-60% for cefotetan, and 51-76% for clindamycin. No isolates were resistant to chloramphenicol or metronidazole. CONCLUSIONS: Piperacillin-tazobactam, cefoxitin, imipenem, chloramphenicol, and metronidazole are still active against B. fragilis group isolates, while clindamycin no longer has a value as an empirical therapeutic agent in Korea. Furthermore, this study identified the first imipenem-resistant B. fragilis group isolates in Koreaope

Complete genome sequence of the podoviral bacteriophage YMC/09/02/B1251 ABA BP, which causes the lysis of an OXA-23-producing carbapenem-resistant Acinetobacter baumannii isolate from a septic patient

The emergence of carbapenem-resistant Acinetobacter baumannii, responsible for causing nosocomial infections, has been becoming a significant global health issue. In this article, we report the complete genome sequence of bacteriophage B-B1251 (YMC/09/02/B1251 ABA BP), which causes lysis of a carbapenem-resistant A. baumannii strain. The bacteriophage belongs to the family Podoviridae and has a double-stranded circular DNA genome with a length of 45,364 bp and a 39.05% G+C content. Genome analysis showed that it had no similarity to other previously reported bacteriophages capable of infecting A. baumannii.ope

Simultaneous Isolation of Vibrio vulnificus and Vibrio parahaemolyticus in Blood from a Liver Cirrhosis Patient: Importance of Detection and Identification of Both Species

A 56-year-old woman with underlying liver cirrhosis was hospitalized with chief complaints of fever, which developed after eating raw fish on the previous day. On physical examination, she showed hypotension. Vibrio vulnificus and Vibrio parahaemolyticus strains were simultaneously isolated from blood cultures, and the patient recovered after treatment with antibiotics including cefotaxime. To our knowledge, simultaneous isolation of both V vulnificus and V parahaemolyticus from the blood has never been documented before in Korea or any other countries. When blood cultures from a patient with underlying disease such as liver disease show growth of gram-negative bacilli in the summer months, microbiologists in Korea, where Vibrio infection is prevalent, should be aware of the possi￢bility that V. vulnificus and other Vibrio spp. can be isolated simultaneously. An accurate identifica￢tion of all isolates is important, because antimicrobial susceptibility patterns. severity and prognosis of the infection are different significantly depending on species.ope