Emerging Carbapenem-Resistant Pseudomonas aeruginosa Isolates Carrying blaIMP Among Burn Patients in Isfahan, Iran

Abstract

BackgroundMetallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is a significant pathogen in burn patients.ObjectivesThe aim of this study was to determine the prevalence of carbapenem-resistant P. aeruginosa isolates, including those resistant to imipenemase (IMP), in a burn unit in Isfahan, Iran.Patients and MethodsOne hundred and fifty P. aeruginosa isolates from burn patients were tested for antibiotic susceptibility by the disc diffusion method in accordance with CLSI guidelines. Production of MBL was identified with the EDTA disk method. DNA was purified from the MBL-positive isolates, and detection of the blaIMP gene was performed with PCR.ResultsFifty-seven out of 150 (38%) isolates were multi-drug resistant (MDR), and 93 (62%) were extensively-drug resistant (XDR). Among all isolates, the resistance rate to ciprofloxacin, tobramycin, imipenem, meropenem, amikacin, ceftazidime, and cefepime was higher than 90%, while the resistance rates to piperacillin/tazobactam and aztreonam were 70.7% and 86%, respectively. Colistin and polymyxin B remained the most effective studied antibiotics. All of the imipenem-resistant P. aeruginosa isolates were MBL-positive, and 107 out of 144 (74.3%) of the MBL isolates were positive for the blaIMP gene.ConclusionsThe results of this study show that the rate of P. aeruginosa-caused burn wound infections was very high, and many of the isolates were resistant to three or more classes of antimicrobials. Such extensive resistance to antimicrobial classes is important because few treatment options remain for patients with burn wound infections. blaIMP-producing P. aeruginosa isolates are a rising threat in burn-care units, and should be controlled by conducting infection-control assessments.

Pseudomonas Aeruginosa in Burn Infections and Its Antimicrobial Resistance

“…1, The study by Radan M et al and Naqvi et al showed 89% and 81.8% resistance to ticarcillin-clavulanic acid which are less than that of our findings. 3,6 In our study, we found that the isolates showed maximum resistance to cefoperazone sulbactam (96.77%) followed by cefepime (93.54%) and ceftazidime (90.32%). In the study by Bhatt et al 77% showed resistant to ceftazidime and 65% showed resistance to cefepime.…”

“…A similar pattern of resistance shown in the Radan M et al all the isolates show 96% resistant to imipenem and meropenem. 3 But less drug resistance is seen in the study done by Rostami S et al, 14 among all isolated P.aeruginosa, 78.5%, 46.7%, and 15% were imipenem, meropenem, and doripenem resistant, respectively. 13 Similarly it was found that 61% isolates were resistant to imipenem and 54% were resistant to meropenem by Bhatt P et al 1 Aztreonam a potent monocyclic ß-lactam with good in vitro activity against P.aeruginosa.…”

“…Similar studies done by Shilba et al shows 43.33% resistance and in the study of Radan et al shows high resistance i.e 86%. 3,9 A combination of upregulated efflux, loss of OprD and impermeability to aminoglycosides compromises every drug class except lipopeptides. Lipopeptides (polymyxin B and colistin) are the last alternative available antimicrobial for multidrug resistant P.aeruginosa.…”

“…Similar results were seen with the studies done by Bhatt P et al and Radan et al But as per the guidelines from clinical and laboratory standards institute (CLSI), the only approved method is broth dilution. 1,3 Disk diffusion and gradient diffusion methods should not be used for the result analysis. So further studies should be done to assess the MIC level of lipopeptides and interpret the resistance pattern among isolates.…”

“…Multi drug resistant (MDR) strains are responsible for rising in wound infections, sepsis, and associated deaths worldwide. 3 Being ubiquitous P.aeruginosa has been found in the contaminated floor, bed rails, and sinks and also from the hands of healthcare workers, which can act as a source of infection in the burn units. Besides transmission through fomites and vectors, these MDR bacteria can be carried into the hospital from the community by the patients as normal flora and can be an important source of infection for the same individual.…”