Epidemiological Study of Pseudomonas aeruginosa isolated in the Hospital: Colonial characteristics, Antibiotic resistance and PFGE patterns / 대한임상병리학회지

BACKGROUND: Pseudomonas aeruginosa is a major cause of nosocomial infections. During recent three years, the isolation rate was high in Wonkwang University Hospital, especially in intensive care unit(ICU) and wards of neurosurgery. We performed this study to investigate the isolation rate and mode of transmission of P. aeruginosa, and usefulness of antibiotic resistance, colonial characteristics and PFGE patterns in the epidemiologic survey. METHOD: From Aug. 1996 to Oct. 1998, 1,682 strains of P. aeruginosa were isolated. For the isolation of P. aeruginosa, environment and 18 nurses's hands were cultured. Antibiotic resistance were tested by NCCLS disk diffusion method for 298 selected strains. Among them 98 strains were evaluated for colonial characteristics(color and margin) on the blood agar and PFGE patterns restricted by Spe I, were evaluated. RESULTS: Overall isolation rate was 12% and was high in medical ICU (23%) and neurosurgical ICU(12%). The majority of specimens where P. aeruginosa was isolated were sputum 47%, urine 24% and wound 21% in decreasing order. The wards where isolation rate was high, had more resistant strains. Ninty eight strains could be classified into 39 different groups by PFGE patterns. But 29 strains belonged to five major patterns (P1-5) and were suspected as epidemic or cross-infected strains. Majority of these strains revealed resistant to two or more antibiotics and colonial phenotype of G2R, GIR(P1), G1I, G3I(P2), Wm(P3), G3I, G3R(P4) and G3I(P5) types. Forty four strains isolated from specimens(sputum, urine, wound, and stool) of 7 patients during hospitalization, revealed single or two PFGE patterns per patient. Conclusion: Transmission mode of P. aeruginosa was suspected to be patient's own GI-tract and cross contamination, especially via health care persons. Combined phenotypes of antibiotic resistance and colonial characteristics correlated well with PFGE patterns. So, in the early period of outbreak of P. aeruginosa, careful examination of colonial characteristics and antibiotic resistance patterns gave meaningful information.

Comparison of Stain Methods with PCR and Culture for the Detection of Mycobacterium Tuberculosis in the Sputum / 대한임상병리학회지

BACKGROUND: Currently, many laboratories have selected several different methods for the detection of M. tuberculosis in the sputum. To select efficient method for clinical laboratories among the various methods, we compared the results of several methods. METHODS: Total 72 sputums were examined by the six combinations of stain methods. The samples were constructed as follows on the result of direct smear ZN stain; negatives (26), traces (3), 1+(9), 2+(12), 3+(12) and 4+(10). The true positives were determined after close evaluation of the clinical, radiological and other laboratory findings. RESULTS: The sensitivities and specificities of each methods were as follows; direct smear ZN stain were 83.6% and 100%, direct smear Auramine stain were 90.9% and 100%, centrifugation ZN stain were 94.6% and 100%, centrifugation Auramine stain were 98.2% and 94.1%, cytocentrifugation ZN stain were 96.4% and 100%, cytocentrifugation Auramine stain were 100% and 64.7%, nested PCR were 80% and 94.1% and culture were 67.3% and 100% respectively. CONCLUSIONS: Concentration method by centrifugation is suitable for routine laboratory if enough centrifugal force were engaged. Auramine stain is more suitable staining method than ZN stain in direct smear but not in concentrated smear because it has the potency of false positivity. The PCR assay is thought to be not only a fast, sensitive method but also a specific method for the direct detection of M. tuberculosis in the sputum. The culture method using Ogawa media is specific but not sensitive.