Antimicrobial Susceptibility and ESBL Prevalence of Clinical Pathogenic Pseudomonas Species

Abstract

The current study was conducted from 2010 to 2014 in Khyber Teaching Hospital, Peshawar, Pakistan to determine the Susceptibility of Pseudomonas spp. to different chemotherapeutic agents and prevalence of extended spectrum β-lactamase. The samples were taken from three main tertiary care hospitals of Peshawar, Pakistan. During the study period, 3450 specimens including pus, urine, blood and burns etc. were collected and subjected to culture and sensitivity as per standard protocols. Samples were isolated and identified on the basis of standard biochemical techniques. Antimicrobial susceptibility was determined by modified Kirby-Bauer method and Minimum Inhibitory Concentrations were followed per the guidelines set by CLSI. The ratio of male to female under the study was 1:1.4. The most productive antimicrobial agent was class carbapenem (imipenem and meronem) against Pseudomonas spp. among the β-lactam agents whose susceptibility was 282 (84.43%) and 304 (91.02%) respectively. The resistance rate was highest for Tetracycline followed by Penicillin and the isolates were co-resistant to macrolides and flouroquinolones and a moderate activity was demonstrated to the Cephalosporins. A total of 232 isolates were recovered from hospitalized and 102 from OPD patients. Statistically significant values were obtained for 17 out of 20 antibiotics, as there is a remarkable variation in susceptibility pattern of OPD and Hospitalized isolates. In class carbapenems: imipenem and meronem showed 81.47%; 91.18% and 88.79%; 96.08% activity rate for indoor and outdoor strains respectively. Only tetracycline had a diminished rate for both in and out door (5.17% and 21.57%) isolates respectively. In-patient isolates showed higher rates of resistance to most tested antibiotics, compared with outpatient isolates. Overall, there was a moderate decrease in susceptibility rate of Pseudomonas spp. to the antibiotic analyzed over the last five years of the study. The MIC50 & 90 (μg/ml) of imipenem against Pseudomonas spp. was <1 and < 4, respectively. While results obtained by agar dilution method demonstrated the lowest MICs values with meropenem for Pseudomonas spp. MICs observed for carbapenems as compared to the other antimicrobials tested were higher. xix Initial screening and phenotypic confirmatory test for ESBL detection was carried out according to the CLSI protocols. Production of ESBLs was observed in 148 (44.32%) of the isolates and the remaining 186 (55.80%) were non-ESBL producers. Statistically, a significant difference was found in susceptibility of the Pseudomonas spp. to carpenems, quinolones and β-lactam/β-lacatamase inhibitors, among the ESBL producers. The resistance conferred by ESBL’s producing pseudomonas spp. to cephalosporin’s (CEC, CAZ, CRO and CFP) was 14.2%, 20.3%, 14.3% and 22.3% respectively, contrary to the non–ESBL’s, where they were comparably sensitive to 3rd and 4th generation cephalosporins. Treatment with third generation cephalosporin (ceftriaxone) is the only risk factor being associated with ESBL infections. β-lactamases of these strains analyzed genotypically by PCR with a series of primers specific for tem, shv and ctx-M genes. 100 samples were selected for PCR to detect tem, shv and ctx-M genes among the ESBL positive Pseudomonas spp. strains. A high proportion of isolates were confirmed for ctx-M gene which encodes a total of 48 strains followed by tem 38 and then 14 of them were shv genes.