A Case of Methicillin-Resistant Staphylococcus aureus Small Colony Variants(SCVs) Isolated from Urine of a Patient with Persistent and Relapsing Bladder Stone / 대한임상미생물학회지

Methicillin-resistant Staphylococcus aureus colony variants (SCVs) are frequently auxotrophic for hemin, menadione, thiamine, and CO2 involved in biosynthesis of the electron transport chain element. This phenotype grows slowly, and forms very small, nonhemolytic colonies in routine culture, so it may be led to the misidentification of this organism. We isolated an organism with catalase-positive, gram-positive cocci in cluster from the urine of a 55-years-old woman with persistent and relapsing bladder stone, who had undergone the antibiotic treatment with cefotaxime, ceftizoxime, amikacin, and/or micronomicin, intermittently for three years. The possibility of SCVs should have been ruled out because this organism didn't grow on Mueller-Hinton agar (MHA) for the susceptibility test. It formed small colonies on blood agar plate overnight, and grew only on MHA with supplement of hemin, or with 5% CO2. This organism was coagulase-positive, DNase-positive, manitol-salt positive, and identified as S. aureus with VITEK GPI card. The susceptibility test could be performed after adding hemin(1mg/mL) into bacterial suspension and showed susceptibility against vancomycin, teicoplanin, and rifampin. Because these phenotypes can be misidentifide as other non-pathogenic organisms due to their atypical characteristics, we should consider SCVs in case of small, nonhemolytic colonies with catalase-positive, gram-positive cocci in cluster, showing no growth on MHA. In addition, infections caused by SCVs are recently recognized in relation to persistent and relapsing infection, so they could be isolated from the patients with long-term antibiotic therapy.

A Prospective Study on the lncidence of Ventilator-associated Pneumonia in Patients with Circuit Changes every 3 days Versus Weekly Changes / 병원감염관리

BACKGROUND: Ventilator associated pneumonia (VAP) is the most serious nosocomial infection of intensive care units. Several studies have investigated the relationship between the interval of ventilator circuit changes and the incidence of pneumonia in foreign countries, but there are no reports about it in Korea yet. So we performed this study to compare the clinical and cost impact between 3 days and 7 days interval in ventilator circuit changes. METHODS: Seoul National University Hospital is a 1,500-bed, university affiliated, tertiary and acute care hospital. All patients admitted to medical intensive care unit (MICU) and surgical intensive care unlt (SICU) between April 1, 1998 and October 31, 1998, requiring mechanical ventilation were included. Patients were divided into two groups of a-cay circuit changes and weekly changes. Daily surveillance was conducted using the criteria of VAP of the National Nosocomial Infection Surveillance System. Incidence of VAP and risk factors for VAP were evaluated. Standard microbiologic methods were used for the identification of clinical and environmental isolates. Statistical analysis was done by SAS Program (version 6.12), analysis of difference in variables was performed using chi-square test and t-test. Analysis of odds ratios was done with logistic regression analysis. RESULTS: VAP developed at a rate of 12.2 per 1,000 ventilator-days in the 3 days change group and 15.6 per 1,000 ventilator-days in the weekly change group (P=0.7240). The only statistically significant risk factor of VAP was duration of mechanical ventilation, The risk of VAP in patients with more than 7 days was 2.23 times higher than in patients with 7 days and below (OR; 2.2296). Estimated annual savings of nursing time by extending ventilator circuit change interval from 3 days to 7 days were 26,806 min 48 sec and estimated savings of cost by reduction of nursing times was calculated as 6,701,700 won. CONCLUSIONS: Weekly ventilator circuit changes in patients undergoing ventilation therapy in the ICU do not contribute to increased the rates of VAP and are cost-effective.

Detection of Shiga Toxin-Producing Escherichia coli by in Stitu hybridization and sequence Analysis of Stx2 / 대한임상미생물학회지

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) was found in several serotypes of E coli including 0157 serotype. Sorbitol-MacConkey agar: may be useful for the detection of E. coli 0157, but is not helpful for the detection of sorbitol-fermenting STEC other than 0157. Moreover, some strains of E. colt 0157 can ferment sorbitol. In this study, in situ hybridization using DNA probe of shiga toxin was used for the isolation of STEC from the PCR-positive stool and -Sequenbe analysis of a part of shiga toxin gene was performed. METHODS: The stool was incubated in LB broth overnight and DNA was extracted from the culture fluid. Multiplex PCR was performed with primers for stxl and stx2 genes. Specimen showed PCR-positive was incubated on MacConkey agar and colonies were blotted with nitrocellulose membrane. Digoxigenin-labelled DNA probe for shiga toxin was made by PCR and the positive colonies were detected with anti-digoxigenin-alkaline phosphatase conjugate and nitroblue tetrazolium. Agglutination test with antisera was performed for the serotying and VTEC-RPLA kit was used for the toxin production. Sequence analysis of PCR products was performed with automatic sequence analyser. RESULTS: An stxl-negative, but stx2-positive PCR was observed in a three-year-old girl, who visited Kumi Hospital on July 19, 1999 complaining of vomiting and diarrhea. The positive colonies were isolated by in situ hybridization using stx2-specific DNA probe. The titers of stxl and stx2 by VTEC-RPLA test were negative and 1:64, respectively. Agglutination for the serotyping was not observed with all of the 0 antisera. 160-nucleotide sequence of stx2 of this isolate was identical with bacteriophage 933W (GenBank X07865), except for the change (T-C) of 957th nucleotide and amino acid sequence was identical each other. CONCLUSIONS: For the sensitive detection of STEC from the stool of patients with diarrhea, multiplex PCR is recommended with stxl- and stx2-specific primers. And in situ hybridization should be performed in PCR-positive specimen for the isolation of STEC. This method may be helpful for the detection of STEC as the causative microorganisms in food-borne outbreak.

Detection of Shiga Toxin-Producing Escherichia coli by in Stitu hybridization and sequence Analysis of Stx2 / 대한임상미생물학회지

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) was found in several serotypes of E coli including 0157 serotype. Sorbitol-MacConkey agar: may be useful for the detection of E. coli 0157, but is not helpful for the detection of sorbitol-fermenting STEC other than 0157. Moreover, some strains of E. colt 0157 can ferment sorbitol. In this study, in situ hybridization using DNA probe of shiga toxin was used for the isolation of STEC from the PCR-positive stool and -Sequenbe analysis of a part of shiga toxin gene was performed. METHODS: The stool was incubated in LB broth overnight and DNA was extracted from the culture fluid. Multiplex PCR was performed with primers for stxl and stx2 genes. Specimen showed PCR-positive was incubated on MacConkey agar and colonies were blotted with nitrocellulose membrane. Digoxigenin-labelled DNA probe for shiga toxin was made by PCR and the positive colonies were detected with anti-digoxigenin-alkaline phosphatase conjugate and nitroblue tetrazolium. Agglutination test with antisera was performed for the serotying and VTEC-RPLA kit was used for the toxin production. Sequence analysis of PCR products was performed with automatic sequence analyser. RESULTS: An stxl-negative, but stx2-positive PCR was observed in a three-year-old girl, who visited Kumi Hospital on July 19, 1999 complaining of vomiting and diarrhea. The positive colonies were isolated by in situ hybridization using stx2-specific DNA probe. The titers of stxl and stx2 by VTEC-RPLA test were negative and 1:64, respectively. Agglutination for the serotyping was not observed with all of the 0 antisera. 160-nucleotide sequence of stx2 of this isolate was identical with bacteriophage 933W (GenBank X07865), except for the change (T-C) of 957th nucleotide and amino acid sequence was identical each other. CONCLUSIONS: For the sensitive detection of STEC from the stool of patients with diarrhea, multiplex PCR is recommended with stxl- and stx2-specific primers. And in situ hybridization should be performed in PCR-positive specimen for the isolation of STEC. This method may be helpful for the detection of STEC as the causative microorganisms in food-borne outbreak.

Bactericidal Effect of Disinfectant Tego-51(R) / 병원감염관리

BACKGROUND: Disinfection is essential for the prevention of hospital infoction. Tego-51, one of the amphoteric surfactants based on the dodecyl-di( aminoethyl)-glycine, has been considered as an effctive disinfectant having a broad specturn of antimicrobial activity. We evaluated the disinfective activity of Tego-51 against several clinical isolates of bacteria and yeasts including Helicobacter pyiori. METHODS: Twenty three strains of vacteria including H. pylori, and a strain of yeast were exposed to the various concentrations (0.05%, 0.01%, 0.005%) of Tego-51 for the various periods (0.5, 1, 2, 4, 8, 16min). After the exposure to Tego-51 disinfectant, 0.01 mL of mixture of microorfanisms and Tego-51 was inoculated into brain-heart infusion broth, into Sabouraud dextrose agar. or Wilkins-Chalgren agar with 10% sheep blood, and incubated at 37 degrees C for 48 hours or in the Campy Pouch microaerophilic system. RESULTS: Most strains were killed within 30 seconds after an exposure to 0.01% of Tego-51, but Proteus mirabilis was eradicated after two minutes of exposure. At the concentration of 0.005 % concentration. P. mirabilis and Bacillus subtilis were killed after eight minutes od exposure. H. pylori was killed with 0.005% Tego-51within 30 seconds. Conslusions: This study showed that Tego-51disinfectant was effective for the disinfection of commonly isolated bacteria and yeast from hospital. It may be recommended that Tego-51 should be used at concentration greater than 0.1% for the effective disinfection of skin, instruments and hospital floors.