RESUMEN
BACKGROUND AND OBJECTIVES: Pseudomonas aeruginosa possesses a variety of virulence factors that may contribute to its pathogenicity. The aim of this study was to evaluate oprI, oprL and toxA genes for PCR identification of clinical P. aeruginosa. In order to find out any relation between special virulence factors and special manifestation of P. aeruginosa infections, we detected virulence factors among these isolates by PCR. Ribotyping was used to evaluate the clonal relationship between strains with the same genetic patterns of the genes studied. MATERIALS AND METHODS: In this study, 268 isolates of P. aeruginosa were recovered from burn, wound and pulmonary tract infections. The prevalence of oprI, oprL, toxA, lasB, exoS and nan1 genes was determined by PCR. One hundred and four isolates were selected randomly to investigate clonal diversity of the isolates with ribotyping using SmaI. RESULTS AND CONCLUSIONS: All P. aeruginosa isolates in this study carried oprI, oprL and lasB genes. Difference between exoS prevalence in isolates from pulmonary tract and burn isolates was statistically significant. Prevalence of nan1 and toxA gene was significantly higher in pulmonary tract and burn isolates, respectively. Ribotyping showed that most of the isolates (87%) belonged to clone A and B. Detection of oprI, oprL and toxA genes by PCR is recommended for molecular identification of P. aeruginosa. Determination of different virulence genes of P. aeruginosa isolates suggests that they are associated with different levels of intrinsic virulence and pathogenicity. Ribotyping showed that strains with the same genetic patterns of the genes do not necessarily have similar ribotype patterns.
RESUMEN
BACKGROUND & OBJECTIVE: Pseudomonas aeruginosa is a common cause of nosocomial infections and exhibits innate resistance to a wide range of antibiotics. This study was undertaken to determine the resistance patterns of P. aeruginosa isolates recovered from patients at two hospitals in Tehran, to investigate the presence of plasmids and to genetically characterize them by pulsed field gel electrophoresis (PFGE). METHODS: The susceptibility of 104 isolates of P. aeruginosa to 13 different antibiotics was determined by agar disk diffusion method. The alkaline lysis method was used for plasmid extraction. PFGE technique was optimized for DNA fingerprinting of isolates. RESULTS: The isolates showed resistance to 13 different antibiotics ceftizoxime (99%), lomefloxacin (94.3%), ceftazidime (59.6%), ticarcillin (50%), ceftriaxone (44.3%), cefoperazone (37.5%), tobramycin (34.6%), piperacillin and gentamicin (33.7%), carbenicillin (25%), amikacin (22%), ciprofloxacin (15.4%) and imipenem (2.9%). Plasmids were detected in 31 isolates (29.8%) that produced 15 different patterns. In total, 84 DNA banding patterns were detected by PFGE. The dominant PFGE type, Pattern A with 14 isolates was found at both hospitals. The remaining isolates were grouped in B, C, D and PF1-PF80. The majority of isolates with the identical plasmid profiles and resistance patterns produced closely related DNA fingerprints by PFGE. INTERPRETATION & CONCLUSION: Isolates in pattern A were distributed widely at both hospitals and the environment. Absence of plasmids in majority of isolates indicated low typeability and discriminatory power of this technique.