Coexistence of AmpC and Extended-Spectrum β-lactamases in Metallo-β-Lactamase Producing Pseudomonas aeruginosa Burn Isolates in Tehran

Abstract

Background: Multi-drug resistant Pseudomonas aeruginosa causes serious complications in burn patients. One of the most important mechanisms of resistance to β-lactam antibiotics is hydrolysis of antibiotics by various β-lactamases. In recent years, Carbapenems have been widely used for treatment of P. aeruginosa infections. However, the organisms have become resistant to Carbapenems mostly by producing metallo β-lactamases. Objectives: The aim of this study was to determine antibiotic susceptibility, production of extended spectrum and AmpC β-lactamases in metallo β-lactamase producing P. aeruginosa burn isolates. Materials and Methods: Antibiotic susceptibility of 135 P. aeruginosa burn isolates was determined by disc diffusion. Metallo β-lactamase production was screened by the double disc synergy test. Metallo β-lactamase producing bacteria were then tested for extended spectrum β-lactamase production by the combined disc diffusion method. AmpC production was carried out using AmpC disc test. Results: There was 99% resistance to Carbenicillin, and Ticarcillin, 98% to Cotrimoxazole, 96% to Ciprofloxacin, and Aztreonam, 95% to Imipenem, and Meropenem, 94% to Pperacillin, 93% to Tobramycin, 92% to Cefepime, 90% to Amikacin, 89% to Ceftazidime, and 87% to Piperacillin-tazobactam. Among the 128 Imipenem resistant isolates, 32 (25%) were capable of producing metallo β-lactamases of which, 4 (12.5%) produced extended spectrum and 26 (81%) produced AmpC β-lactamases. Four isolates (12.5%) produced all 3 types. Conclusions: This study showed that multiple β-lactamases can be produced in burn isolates. This suggests that use of Cephalosporins and Carbapenems should be restricted in burn isolates to minimize the development and spread of these multidrug resistant pathogens.

Molecular Detection of blaVEB-1 Beta-Lactamase Encoding Gene Among Extended Spectrum B-Lactamase Positive Wound Isolates of Pseudomonas aeruginosa

“…However, resistance to the inhibitor indicates the possible presence of AmpC or other consistent enzymes (18). Several previous studies that aimed to detect ESBLs have demonstrated a high level of resistance among P. aeruginosa isolates to antibiotics (19). In this study, more than half of the wound ESBL positive isolates could amplify bla VEB-1 (47%).…”

Prevalence of Extended-Spectrum and Metallo β-Lactamase Production in AmpC β-Lactamase Producing Pseudomonas Aeruginosa Isolates From Burns

“…Fifty one non-duplicate P. aeruginosa isolates were randomly selected from a collection of burn isolates provided by Shahid Motahari Hospital in 2011. The antibiotic susceptibility patterns and MBL production were previously determined using disc diffusion and the double disc synergy tests, respectively ( 12 ). The isolates were maintained in brain heart infusion broth (Oxoid, UK) containing 10% dimethyl sulfoxide and stored at -20ºC until use.…”

Prevalence of blaIMP and blaVIM gene carriage in metallo-β–lactamase-producing burn isolates of Pseudomonas aeruginosa in Tehran

“…The antibiotic susceptibility and MBL production of the isolates were determined by disk diffusion and the double disk synergy test (DDS), as previously reported in the literature (10). The organisms were stored at -20 °C in a brain heart infusion broth (Oxoid, UK) containing 10% dimethyl sulfoxide until use.…”