Phenotyping and genotyping of pseudomonas aeruginosa urine isolates in Zagazig University Hospitals

ABSTRACT

Pseudomonas aeruginosa [P. aeruginosa] is an important nosocomial pathogen. therefore sensitive typing techniques are required for its control. Seventy six isolates of P.aeruginosa were recovered from midstream urine specimens obtained from the different Departments in the Zagazig University Hospitals [ZUHs]. Five isolates were polymorphic while the remaining 71 isolates were unimorphic. Different morphotypes of the same isolates were studied separately. In addition, 10 environmental isolates were obtained from the wards of the Urology Department. All isolates and their morphological variants were characterized by morphotyping on primary isolation, biochemical reactions using API 20 NE system, serotyping, antimicrobial susceptibility typing and genotyping using enterobacterial repetitive intergenic consensuspolymerase chain ration [ERIC-PCR] and random amplification of polymorphic DNA [ RAPD] using API2H primer. The unimorphic clinical and environmental isolates belonged to morphotype 1 [56.3% and 60%, respectively], morphotype 2 [22.5 % and 30%, respectively] and morphotype 4 [19.7% and 10%. respectively]. For the clinical and environmental isolates, including morphological variants, 14.1% and 30%, respectively showed atypical biochemical reactions. All were esculin positive. Forty seven percent of the clinical isolates and variants were serologically typable and none of the environmental isolates was typable. Among the typable clinical isolates and variants, serotypes 4 [17.1%] and 6 [7.9%] were the commonest. All isolates could be grouped under 14 antimicrobial susceptibility types. ERIC-PCR yielded 31 typing patterns. Twenty one patterns comprised the clinical isolates and their morphological variants, and 10 patterns comprised the environmental isolates. RAPD by API2H primer yielded 13 types for both clinical and environmental isolates. We concluded that ERIC-PCR was the most discriminatory of all the phenotypic and molecular methods used in this study for typing P.aeruginosa. On the other hand, RAPD using API2H primer seems to be useful for further subtype isolates of the same ERIC pattern. Furthermore. P.aeruginosa isolates of the same genotype can be discriminated by using phenotypic methods like serotyping and antimicrobial susceptibility typing. Interestingly, the majority of morphological variants obtained on primary culture from the same midstream urine samples may represent different strains rather than phenotypic plasticity of the same strain. Therefore, antibiograms should be performed separately for such colonial variants. Moreover, in our study, the environmental isolates of P. aeruginosa played a little role, if any, in the spread of P. aeruginosa nosocomial urinary tract infection