RESUMEN
Quorum-sensing systems regulate expression of several virulence factors in Pseudomonas aeruginosa. This study investigated the relation between expression of the las quorum-sensing system and expression of mexY and ampC in 35 clinical isolates of P. aeruginosa. Antibiotic susceptibility was determined by the disc diffusion method according to the Clinical and Laboratory Standards Institute [CLSI] guidelines. Expression of genes including lasl, lasR, mexY, ampC and ampR was assessed by real time RT-PCR. Twenty eight isolates with elevated expression of mexY and ampC [compared to P. aeruginosa PAO1] were resistance to ceftazidime, imipenem, ciprofloxacin and amikacin. Also these isolates demonstrated increased expression of lasl and lasR. The remaining seven isolates showed intermediate resistance to ciprofloxacin and amikacin. These seven isolates with elevated ampR expression -demonstrated decreased expression of mex Y, ampC, lasl and lasR. In contrast to previous study, current study demonstrated that the expression pattern of ampC was identical to the lasl expression pattern among clinical isolates. Furthermore according to previous study we expected that AmpR positively regulated ampC expression but in our study, some of the isolates with elevated ampR expression showed decreased ampC expression. The expression pattern of lasR and mexYwas identical in all of the isolates. It seems there was a direct or indirect relation between expression of lasR and mexY expression in P. aeruginosa
RESUMEN
Pseudomonas aeruginosa is one of the most important opportunistic pathogens responsible for various types of infections. Children suffer significant morbidity and mortality due to nosocomial infections. The aim of this study was to investigate the presence of Class-1 integron, bla[BEL], bla[PER], bla[kpc], bla[VIM],bla[IMP] and bla[OXA] A-group-1 genes among P. aeruginosa isolates at Children's Medical Center Hospital in Iran and to determine phenotypic evidence of ESBL and MBL production. Antibiotic susceptibility tests were analyzed for 72 P. aeruginosa clinical isolates. Isolates were identified by using biochemical tests and confirmed by PCR assay for oprL gene. ESBL and MBL producer isolates were identified by phenotypic tests [double disc synergy tests]. Detection of beta-lactamase genes and class-1 integron were performed by PCR method. All of the isolates were susceptible to ceftazidime / clavulanate, me-ropenem, imipenem and ciprofloxacin. About 83.3% and 16.7% of isolates were resistant to ceftazidime and amikacin respectively. Approximately, 83.3% of isolates were considered as potential ESBL producers. None of the clinical isolates showed above P-lactamase genes. It seems that, the reason is the absence of class-1 integron in all of isolates. About 16.7% of strains were identified as multidrug resistant. Fortunately, all of the isolates were susceptible to meropenem and imipenem which are effective against ESBL producing strains. The absences of class-1 integron decreases the probability of acquired beta-lactamase especially MBL. Thus, absolute susceptibility to carba-penems and ciprofloxacin among P. aeruginosa isolates in pediatric hospital has important implications for empirical antimicrobial therapy. It seems that these properties help to decrease mortality of nosocomial infections within children