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

Park, Do Sim; Cho, Ji Hyun; Lee, Young Jin; Moon, Young Hoi

Abstract

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.