An Increase in the Clinical Isolation of Acquired AmpC beta-Lactamase-Producing Klebsiella pneumoniae in Korea from 2007 to 2010

We investigated the occurrence and genetic basis of AmpC beta-lactamase (AmpC)-mediated antibiotic resistance, by examining Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis isolates at a university hospital, from 2007 to 2010. The ampC genes were detected by multiplex AmpC PCR, and AmpC-positive strains were subjected to DNA sequencing. Extended-spectrum beta-lactamase (ESBL) production was assessed using the ESBL disk test based on the utilization of boronic acid. Carbapenem-resistant isolates were further investigated by the modified Hodge test, a carbapenemase inhibition test and SDS-PAGE experiments. AmpC expression was detected in 1.6% of E. coli (39 DHA-1, 45 CMY-2, and 1 CMY-1) isolates, 7.2% of K. pneumoniae (39 DHA-1, 45 CMY-2, and 1 CMY-1) isolates, and 2.5% of P. mirabilis (8 CMY-2 and 1 CMY-1) isolates. Of the 198 acquired AmpC producers, 58 isolates (29.3%) also produced an ESBL enzyme. Among the acquired AmpC-producing K. pneumoniae isolates, the minimum inhibitory concentration (MIC) MIC50/MIC90 values for cefoxitin, cefotaxime, cefepime, imipenem, and meropenem were >32/>32, 16/>32, 1/16, 0.25/0.5, and or =2 microg/mL for 2 K. pneumoniae isolates, both of which carried the blaDHA-1 gene with a loss of OmpK36 expression, but were negative for carbapenemase production. The acquisition of AmpC-mediated resistance in K. pneumoniae isolates increased, as did the proportion of AmpC and ESBL co-producers among the hospital isolates. The accurate identification of isolates producing AmpCs and ESBLs may aid in infection control and will assist physicians in selecting an appropriate antibiotic regimen.

Modified CHROMagar Acinetobacter Medium for Direct Detection of Multidrug-Resistant Acinetobacter Strains in Nasal and Rectal Swab Samples

This study aimed to investigate whether CHROMagar Acinetobacter medium (CHROMagar, France) in combination with an antimicrobial supplement (modified CHROMagar Acinetobacter; CHROMagar, France) can be used for detecting and isolating multidrug-resistant Acinetobacter species (MRA) in nasal and rectal surveillance cultures. Nasal and rectal swab samples were collected from patients in an intensive care unit at a teaching hospital. The samples were used to inoculate modified CHROMagar Acinetobacter plates, which were examined after 24 and 48 hr of incubation at 37degrees C. Their susceptibility against the antimicrobial agents meropenem, imipenem, ciprofloxacin, and amikacin was analyzed using the Etest (bioMerieux, France). A total of 406 paired samples (406 nasal swabs and 406 rectal swabs) were obtained from 226 patients, and 120 samples (28 nasal and 28 rectal cultures, 47 nasal cultures only, and 17 rectal cultures only) yielded MRA. Seventy-five MRA isolates (18.5%) were recovered from the 406 nasal samples, and 45 MRA isolates (11.1%) were recovered from the 406 rectal samples. Of the 120 MRA isolates, 3 (2.5%) were detected only after 48 hr of incubation. The use of modified CHROMagar Acinetobacter together with nasal and rectal swabs and 1-day incubation is an effective surveillance tool for detecting MRA colonization.

Modified CHROMagar Acinetobacter Medium for Direct Detection of Multidrug-Resistant Acinetobacter Strains in Nasal and Rectal Swab Samples

This study aimed to investigate whether CHROMagar Acinetobacter medium (CHROMagar, France) in combination with an antimicrobial supplement (modified CHROMagar Acinetobacter; CHROMagar, France) can be used for detecting and isolating multidrug-resistant Acinetobacter species (MRA) in nasal and rectal surveillance cultures. Nasal and rectal swab samples were collected from patients in an intensive care unit at a teaching hospital. The samples were used to inoculate modified CHROMagar Acinetobacter plates, which were examined after 24 and 48 hr of incubation at 37degrees C. Their susceptibility against the antimicrobial agents meropenem, imipenem, ciprofloxacin, and amikacin was analyzed using the Etest (bioMerieux, France). A total of 406 paired samples (406 nasal swabs and 406 rectal swabs) were obtained from 226 patients, and 120 samples (28 nasal and 28 rectal cultures, 47 nasal cultures only, and 17 rectal cultures only) yielded MRA. Seventy-five MRA isolates (18.5%) were recovered from the 406 nasal samples, and 45 MRA isolates (11.1%) were recovered from the 406 rectal samples. Of the 120 MRA isolates, 3 (2.5%) were detected only after 48 hr of incubation. The use of modified CHROMagar Acinetobacter together with nasal and rectal swabs and 1-day incubation is an effective surveillance tool for detecting MRA colonization.

Evaluation of the Vitek 2 AST-N055 Card for the Susceptibility Testing of Acinetobacter baumannii Isolates to Amikacin / 대한임상미생물학회지

We collected 76 clinical isolates of Acinetobacter baumannii (amikacin MIC by Vitek 2 AST-N055 card: or =64microgram/ mL, 2 isolates) from a university hospital and evaluated the Vitek 2 AST-N055 card vs the broth microdilution as a reference method for testing susceptibility to amikacin. Vitek 2 AST-N055 card yielded very major errors in 15 isolates (19.7%) and minor errors in 26 isolates (34.2%). Of the 15 isolates shown very major errors, 14 had Vitek 2 MICs ranging from 8 to 16microgram/mL. The results of our study suggest strongly that it is unreliable to test the amikacin susceptibility by Vitek 2 AST-N055 card of A. baumannii with the Vitek 2 MICs ranging from 8 to 16microgram/mL. In those cases, another susceptibility test, such as broth microdilution (BMD), should be performed to confirm the results.

The Level of Medical Technologists' Perception of and Compliance with Hospital Infection Control Guidelines / 병원감염관리

BACKGROUND: The propose of this study was to identify the level of medical technologists' perception of and compliance with hospital infection control guidelines. METHODS: A questionnaire survey was conducted for 65 medical technologists working at three university hospitals in Seoul and Kyunggi areas. The questionnaire was composed of 34 questions on the general characteristics (14 items) of individual responders and about infection control guidelines (20 items). Their response was marked on the basis of 5 points for each question. RESULTS: The mean scores of the perception of and compliance with the infection control guidelines were 4.62+/-0.34 and 3.85+/-0.42, respectively. The female technologists scored significantly higher than did the male counterparts in the participation level of the infection control guidelines (P<0.05). The medical technologists who had participated in an infection control educational program were more likely than those who had not to show a higher compliance level on the infection control guidelines (P<0.05). CONCLUSION: The study demonstrated that the development of infection control educational programs for medical technologists and a supportive policy of the hospital administration should contribute to the prevention of nosocomial infections.

Evaluation of Vitek and Disk Diffusion Susceptibility Testing of Enterobacteriaceae against Piperacillin-Tazobactam and Methicillin-Resistant Staphylococcus aureus against Trimethoprim-Sulfamethoxazole / 대한임상미생물학회지

BACKGROUND: The aim of this study was to evaluate the Vitek system and the disk diffusion method for susceptibility testing of Enterobacteriaceaeagainst piperacillin-tazobactam (TZP) and methicillin-resistant Staphylococcus aureus (MRSA) against trimethoprim-sulfamethoxazole (SXT)using the broth microdilution method as the reference. METHODS: Using the Vitek system and the disk diffusion method, we tested 96 isolates of Enterobacteriaceae (48 Escherichia coli, 26 Klebsiella pneumoniae, 8 Serratia marcescens, 6 Enterobacter cloacae, 2 E. aerogenes, 2 K. oxytoca, 2 Citrobacter freundii, 2 Pantoea agglomerans) and 61 isolates of MRSA for susceptibity against TZP and SXT, respectively; the broth microdilution of National Committee for Clinical Laboratory Standards was used as the reference method. RESULTS: In the susceptibility testing of Enterobacteriaceae against TZP, Vitek system yielded 10 (10%) minor errors, and the disk diffusion method one (1%) very major and 13 (14%) minor errors. For the MRSA against SXT, the rate of categorical agreement between the reference method and the Vitek or the disk diffusion method was both 100%. The rates of agreement between the reference method and the Vitek system in term of MICs (within +/-1 dilution) were 93% and 98% in the susceptibility testing of Enterobacteriaceae against TZP and MRSA against SXT, respectively. CONCLUSION: Both Vitek system and disk diffusion method showed an acceptable level of accuracy for the susceptibility test of Enterobacteriaceaeagainst TZP and MRSA against SXT.

Utility of CHROMagar Orientation Medium for Urine Cultures / 임상검사와정도관리

BACKGROUND: Urine cultures are among the most numerous of culture types for microbiology studies. In this study, we evaluated the utility of CHROMagar Orientation (CO; Becton Dickinson, Cockeysville, MD, USA), a new chromogenic medium, for the detection, enumeration, and presumptive identification of urinary tract pathogens. METHODS: The 438 clinical urine samples sent for routine culture were plated onto CO and Bi-plate (blood/MacConkey agar). We compared the detection and enumeration of potential pathogens, and the agreement between presumptive identification directly from CO and the confirmative identification, which was performed using conventional biochemical tests and Vitek system. RESULTS: The detection rate of urinary tract pathogens on all two media, CO and Bi-plate were nearly identical. The enumeration of colony counts was consistent on the two media for 102 of the 108 (94%) microorganisms. Colony color and morphology on CO accurately differentiated Escherichia coli and Enterococcus spp. The overall agreement of presumptive identification on CO was 91 of the 108 (84%). CONCLUSION: The CO enabled accurate detection, count determination, and presumptive identification of common urinary pathogens, both in pure and mixed cultures.

Detection and Occurrence of Extended-Spectrum beta-Lactamase-Producing Citrobacter freundii, Enterobacter spp., Proteus spp., and Serratia marcescens Isolates / 임상검사와정도관리

BACKGROUND: The occurrence of extended-spectrum beta-lactamases (ESBLs) in enterobacteria that possess inducible Bush group 1 chromosomal beta-lactamases is being increasingly reported worldwide. The current National Committee for Clinical Laboratory Standards documents do not indicate the tests that should be used for the detection of ESBLs in Enterobacteriaceae except Klebsiella spp. and Escherichia coli. We determined the occurrence and detection of ESBL-producing Enterobacteriaceae isolates. METHODS: One hundred fifty-six consecutive, non-repeated isolates of Citrobacter freundii, Enterobacter spp., Proteus spp., and Serratia marcescens were collected. These isolates were performed broth microdilution antimicrobial susceptibility test, Vitek ESBL detection test, and double disk synergy (DDS) test. All the DDS-positive strains were tested PCR amplification of the blaTEM and blaSHV alleles. RESULTS: S. marcescens (27.3%) was the most frequently isolated ESBL producers followed by E. cloacae (23.8%), E. aerogenes (18.2%), C. freundii (13.3%), and P. mirabilis (8.3%). Among the total of 30 isolates that were considered ESBL producers, the Vitek ESBL detection test was positive for 26 (86.7%) strains. The genotypes of ESBLs were predominently SHV type (10 isolates) followed by others (8 isolates), SHV and TEM (7 isolates), and TEM type (5 isolates). CONCLUSIONS: Our findings indicate that 19.2% of all Enterobacteriaceae except E. coli and Klebsiella spp. tested produced ESBLs. The Vitek ESBL detection test seems to be a useful test to identify ESBL-producing strains of C. freundii, Enterobacter spp., Proteus spp., and S. marcescens isolates.

A Case of Hafnia alvei Peritonitis with Septicemia / 대한임상미생물학회지

Hafnia alvei is gram-negative bacilli that is rarely isolated from human specimens and is rarely considered to be pathogenic. It has been associated with gastroenteritis, pneumonia, meningitis, bacteremia, and nosocomial wound infections. But, no case of extraintestinal H. alvei infection was documented in Korea to our knowledge. A 50-year-old man with hepatocellular carcinoma was admitted to our hospital via emergecy department because of abdominal pain. The peritoneal fluid and 3 consecutive blood cutures yielded H. alvei. The organism was susceptible to all antimicrobial agents tested, except cefazolin. Despite treatment with intravenous cefotaxime, the patient was expired after 4 days due to septicemia.