Typing of Pseudomonas aeruginosa isolated from respiratory tract of patients in intensive care units by pulsed-field gel electrophoresis

Abstract

The purpose of this study is to use pulsed-field gel electrophoresis (PFGE) to perform the molecular typing of P.aeruginosa isolates from various sources including colonized patients, sputum of lower respiratory tract infected patients and environment in the patients units. This technique was able to discriminate 135 isolates into 72 pulsotypes. The results obtained was used for the epidemiological evaluation of P.aeruginosa which demonstrated that there was no predominant pulsotype found in the Respiratory Care Unit (RCU), the Traumatic Intensive care Unit (TICU), and sputum of lower respiratory infected patients. The epidemiological data was also obtained from this study, it was shown that 12 out of 82 patients in the RCU (14.63%) had P.aeruginosa throat colonization and 3 out of 25 patients who had surgical wound from trachiostomy (12%) carried this organism in their wound. In the TICU 15 out of the 147 patients (10.20%) had P.aeruginosa in their throat and one out of 22 patients carried the organism in their surgical wound. In the RCU, 8 out of 12 patients (66.7%) were colonized with P.aeruginosa on the first day of admission and 4 out of 12 patients (33.3%) had acquired P.aeruginosa after admission. In the TICU, 7 out of 15 patients (46.7%) were colonized on admission. The remaining 8 out of 12 patients (53.3%) had acquired P.aeruginosa during their stay in this unit. Among the 20 RCU patients who used respirator, only one of them yielded P.aerugiosa in the water from the respirator while none of the 147 TICU patients who were on respirators had P.aeruginosa in such water. P.aeruginosa lower respiratory tract infection had developed in 008.3% of the colonized RCU patients while 20% of the colonized TICU patients had infection. P.aeruginosa from all the sinks in both the RCU and the TICU were isolated in the range of 1-6 times from the total 24 times of specimen collection. This indicated the low possibility that sinks could be the reservoir of this organism. From the study on the antimicrobial administration in both intensive care units, it was shown that the beta-lactams and the aminoglycosides were used most. There was no clearly evidence that these agents were associated with P.aeruginosa colonization. There were 30 different antimicrobial susceptibility patterns (antibiograms) from all isolates with no correlation to the pulsotypes obtained. The results from this study showed that (1) none of the patients harbored the strain similar to the environmental strain, which suggested that colonization with P.aeruginosa originated from endogenous rather than exogenous sources. (2) no common pulsotypes was obtained from all the patients in the different unit and even in the same unit which indicated that there was no epidemic or outbreak of P.aeruginosa infection occurred during the 7 month of study.