Annual Report on the External Quality Assessment Scheme for Clinical Microbiology in Korea (2015)

Annual proficiency surveys were conducted in March, June, and September in 2015 by the Clinical Microbiology Subcommittee of the Korean Association of External Quality Assessment Service. The program covers the sections of bacteriology, advanced bacteriology and mycology, mycobacteriology, and parasitology. Each trial was composed of three sets of different combinations of five bacteria and yeasts. These sets were distributed among laboratories for Gram staining, culture, identification, and antimicrobial susceptibility tests. Five slides with fixed sputum smears were provided as part of each trial for acid-fast bacilli detection. The survey material distribution was section-based. Two survey materials were provided in each trial, while five specimens for mycobacterial culture and identification, five specimens for anti-tuberculosis susceptibility testing and two Mycobacterium tuberculosis strains for rapid detection of rifampin and isoniazid resistance were distributed in the March and June trials. Five virtual microscopy files for stool parasite examination were availed by registered participants in the June trial. Out of the 334 enrolled laboratories, 328 (98.2%), 328 (98.2%), and 329 (98.5%) submitted responses in trials I, II, and III, respectively. Identification of bacteria, namely, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Vibrio fluvialis by more than 95% of participants was acceptable. Surveillance cultures for vancomycin-resistant enterococci and carbapenem-resistant Enterobacteriaceae were determined accurately by 75.8%–85.3% and 93.1% of the respondents, respectively. Species-level identification of Candida krusei, Candida lusitanae, and Candida guilliermondii was still low at 79.8%, 55.7%, and 42.7%, respectively. Disk diffusion method revealed an unacceptably high false-positive rate of resistance to glycopeptides in E. faecalis and to trimethoprim-sulfamethoxazole in S. pneumoniae. Advanced bacteriology trials revealed unsatisfactory results for species-level identification of moulds. Mycobacterial culture, identification and susceptibility testing, and molecular detection of rifampin and isoniazid resistance were performed exceedingly well by participants. Hymenolepsis diminuta could not be identified by participants, with a correct answer rate of only 46.5% and ‘no parasite seen’ answer rate of only 31.8% for negative specimens. Species-level identification of Candida and moulds was challenging for clinical microbiology laboratories. Disk diffusion method was found to be problematic in testing the susceptibility of microorganisms to glycopeptides and trimethoprim-sulfamethoxazole. Improvement is required in result interpretation of negative specimens in parasitology.

Prevalence of Imipenem-Resistant Pseudomonas aeruginosa Isolates and Mechanisms of Resistance / 대한임상미생물학회지

BACKGROUND: Spread of imipenem-resistant Pseudomonas aeruginosa isolates is an important clinical threat. The aim of this study is to survey the prevalence of carbapenem-resistant P.aeruginosa isolates in a university hospital, Busan, Korea, and to determine the mechanisms of the resistance. METHODS: P.aeruginosa isolates from the patients in Kosin University Gospel Hospital were collected during the period of June through September, 2004. Antimicrobial susceptibilities were tested by the disk diffusion method, and production of carbapenemase and metallo-beta-lactamase was determined by the modified Hodge and EDTA-disk synergy tests, respectively. MICs were determined by the agar dilution method, and pIs of beta-lactamases were determined by the isoelectric focusing. Genotypes of carbapenemases were determined by direct sequencing of amplified products. RESULTS: A total of 77 clinical isolates of P.aeruginosa were collected. Twenty-two (55.0%) and 15 (37.5%) isolates showed positive results in the modified Hodge and EDTA-disk synergy tests, re-spectively. Searches for bla OXA-23 and bla IMP-1 genes showed positive results in 15 and 12 isolates, respectively. MIC ranges of imipenem and meropenem to OXA-23-producing isolates were 8-16 microgram/mL and 2-32 microgram/mL, respectively, and those to IMP-1-producing isolates were 2-> or =256 microgram/mL and 2-128 microgram/mL, respectively. CONCLUSION: Production of OXA-23 or IMP-1 is the most prevalent mechanism of imipenem-resistance in P.aeruginosa isolates in a university hospital, Busan, Korea. Periodical surveys are necessary to monitor the spreading of imipenem-resistant isolates and emerging new mechanisms of imipenem-resistance.

Genotypes of Metallo-beta-Lactamases Produced by Imipenem-Resistant Acinetobacter spp. Isolates from Clinical Specimens / 감염

BACKGROUND: Carbapenem-resistant Acinetobacter spp. are being isolated with increasing frequency from clinical sources. This study was designed to determine the resistance mechanism to carbapenems of Acinetobacter spp. isolates from patients of a tertiary care hospital in Busan, Korea. METHODS: Nonduplicated clinical isolates of Acinetobacter spp. resistant to carbapenems were collected during the period of 2000-2001 in Kosin Medical Center, Busan, Korea. Antimicrobial susceptibilities were tested by disk diffusion method. Carbapenem-resistant Acinetobacter spp. isolates were examined for metallo-beta-lactamase-production by modified Hodge and EDTA-disk synergy tests. For the detection of blaIMP-1 and blaVIM-2 genes, polymerase chain reactions (PCR) were performed, and the DNA sequences of amplified products were determined by using dideoxy- chain termination method. RESULTS: Among 21 clinical isolates of Acinetobacter spp. intermediate or resistant to carbapenems, 17 isolates showed positive reactions in modified Hodge and EDTA-disk synergy tests. Nine isolates showed positive reaction in PCR for the detection of blaIMP-1 genes, and 8 isolates showed positive reaction in PCR for the detection of blaVIM-2 genes. Sequencing of amplified products showed that they were blaIMP-1 or blaVIM-2 genes. CONCLUSION: Acinetobacter spp. isolates with carbapenem-resistance are not uncommon in Kosin Medical Center, and most of the carbapenem-resistant isolates acquired resistance by production of IMP-1 or VIM-2 metallo-beta-lactamases. The spread of metallo-beta-lactamase genes could compromise the future usefulness of carbapenem for the treatment of gram-negative bacilli infections.

A Case of Vibrio parahaemolyticus Septicemia in a Patient with Liver Cirrhosis / 대한임상미생물학회지

V. parahaemolyticus was isolated from blood culture of a 34-year old female patient with HCV viral hepatitis and liver cirrhosis. V. parahaemolyticus is one of the frequent causative agents of gastrointestinal infection, but rarely causes septicemia. This case is thought to be the 3rd report of V. parahaemolyticus septicemia in Korea.

Prevalence of Extended-spectrum beta-lactamase-producing Enterobacteriaceae and Evaluation of Methods for Detection / 대한임상미생물학회지

BACKGROUND: Increased isolation of extended-spectrum beta-lactamase (ESBL)-producing Entero bacteriaceae resistant to third generation cephalosporins and aztreonam has been noted recently. This study was to determine the prevalence of resistance to these drugs and ESBL in Enterobacteriaceae and to evaluate the methods for de tection. METHODS: During the period of October, 1997 and March, 1998, a total of 731 clinical isolates of Enterobacteriaceae were collected from patients of the Kosin Medical Center, Pusan, Korea. Antimicrobial susceptibility test by disk diffusion method and double disk synergy test were performed. MICs of beta-lactams were determined by agar dilution method. And ESBL genotypes were determined by polymerase chain reaction. RESULTS: About 10% of Escherichia coli isolates and 20% of Klebsiella pneumoniae isolates were intermediate or resistant to the third generation cephalosporins or aztreonam. Sensitivities of cefotaxime, ceftazidime, ceftriaxone and cefpodoxime disks for the detection of ESBL- producing strains of E. coli and K. pneumoniae by NCCLS standards were 100%, respectively, but that of aztreonam disk was 97%. Positive predictive value of the ceftazidime disk was higher than those of other disks. Twenty strains of E. coli, 20 K pneumoniae, 19 Enterobacter spp., six Citrobacter freundii, and eight Serratia marcescens showed positive results in double disk synergy test. The transconjugant strain of K. pneumoniae K20482 had blaSHV, and remains of transconjugants of ESBL-producing K. pneumoniae, Enterobacter spp. and S. marcescens had blaTEM. CONCLUSIONS: In this study, many strains of Enterobacteriaceae isolated in Korea were resistant to third generation cephalosporins and aztreonam. Some of the strains of Enterobacter spp. and S. marcescens as well as E. coli and K. pneumoniae produced ESBL, and majority of these strains had blaTEM. In the detection of ESBL-producing strains of E. coli and K. pneumoniae by NCCLS standards, all of the antimicrobial agent disks tested were useful, but ceftazidime disk was most effective because of its highest positive predictive value.

A Case of Leclercia adecarboxylata Isolated from Dialysate in a Patient with Continuous Ambulatory Peritoneal Dialysis / 대한임상미생물학회지

A 60-year-old male with continuous ambulatory peritoneal dialysis was admitted because of abdominal discomfort and turbid dialysate. He had a history of chronic renal failure due to diabetic nephropathy. His WBC count of perpheral blood was 8,500/mm3 (neutrophil 92%), and that of dialysate was 1,400/mm3 (polymorphonuclear leukocyte 69%, lymphocyte 31%). Pure growth of Leclercia adecarboxylata was isolated from dialysate. The L. adecarboxylata isolate was susceptible to ampicillin, ampicillin/sulbactam, cephalothin, cefoperazone, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, tobramycin, amikacin, tetracycline, trimethoprim- sulfamethoxazole and ciprofloxacin. Cephalothin & amikacin were added into dialysate, and his clinical symptoms and turbidity of dialysate were resolved. L. adecarboxylata has been rarely isolated from clinical specimens. To our knowledge, this is the first report of L. adecarboxylata isolated from clinical specimen in Korea. On review of the world literature, we found only 7 cases of L. adecarboxylata infections. This microorganism has been isolated from lower extremity wounds and sputum as part of a mixed flora in 3 cases and 1 case, respectively, but it was the only microorganism isolated from cultures of blood in 3 cases. These 3 patients with bacteremia due to L. adecarboxylata had severe underlying diseases, and clinical symptoms were developed after invasive procedures. All of the L. adecarboxylata isolates from clinical specimens were susceptible to antimicrobial agents tested, and the responses to antibiotic therapy were excellent. It is difficult to identify this organism because its biochemical reactions are similar to those of Escherichia coli, therefore careful identification is required. And additional studies are necessary to determine the pathogenic potential and route of infection of this organism.

Intestinal Colonization of Vancomycin-Resistant Enterococci / 병원감염관리

BACKGROUND: In the United States, the Centers for Disease Control and Prevention recorded a 20-fold increase in the incidence of vancomycin-resistant enterococci (VRE) associated with nosocomial infections between 1989 and 1991. Although VRE has been reported in Korea since 1992, infections caused by these organisms are still extremely rare in Pusan, Korea. Therefore, a point prevalence culture survey was carried out to investigate the prevalence of intestinal colonization with VRE among patients admitted to Kosin Medical Center, which can predict the appearance of clinical infections with VRE. METHODS: Between July 1997 and August 1997, stool specimens were obtained from 303 patients. Specimens were placed in bile esculin azide broth containing vancomycin (64 microgram/mL) and aatreonam (60 microgram/mL). Cultures were done for 48 hours at 37degrees C, and turbid solutions were subcultured on blood agar. Minimal inhibitory concentrations (MIC) of vancomycin and teicoplanin to Enterococcus isolates were determined by Etest on Mueller-Hinton agar. For amplification of the vanA, vanB, and vanC genes, polymerase chain reactions were performed. RESULTS: VRE isolates were isolated from 6 of the patients (2%). Four of them were identified as E. faecium, and 1 was identified as E. avium, and 1 was identified as Enterococcus spp. All of them were highly resistant to vancomycin (MICs >256 microgram/mL), and they were also resistant to teicoplanin (MICs 32-->256 microgram/mL). All of 6 VRE strains carried vanA gene. CONCLUSION: The colonization of VRE was not infrequent among the patients of a university hospital in Pusan, Korea. Moreover, a large proportion of the colonizing VRE was revealed Enterococcus faecium with vanA gene, which implies quite a possibility of a sudden rising of infections by this organism in the near future. So we propose that the vancomycin susceptibility test should be done for every enterococcal isolate from clinical specimens and the intestinal colonization rate of VRE should be closely monitored at regular intervals for the purpose of surveillance 50 that proper establishment of plans for the prevention of this troublesome pathogen's spread can be promptly made.