METHODS: A total of 53 P. aeruginosa clinical strains were isolated from different patients in Sultanah Aminah Hospital (Johor Bahru, Malaysia) in 2015. Antimicrobial susceptibility testing was performed, and minimum inhibitory concentrations (MICs) of imipenem and meropenem were determined by Etest. Carbapenem-resistant strains were screened for MBL production by the imipenem-ethylene diamine tetra-acetic acid (IMP-EDTA) double-disk synergy test, MBL imipenem/imipenem-inhibitor (IP/IPI) Etest and PCR. Multilocus sequence typing (MLST) analysis was performed for genotyping of the isolates.
RESULTS: Among the 53 clinical strains, 3 (5.7%) were identified as MBL-producers. Multidrug resistance was observed in all three strains, and two were resistant to all of the antimicrobials tested. Sequencing analysis confirmed that the three strains harboured carbapenemase genes (blaIMP-1, blaVIM-2 and blaNDM-1 in one isolate each). These multidrug-resistant strains were identified as sequence type 235 (ST235) and ST308.
CONCLUSIONS: The blaIMP-1 and blaNDM-1 genes have not previously been reported in Malaysian P. aeruginosa isolates. The emergence of imipenemase 1 (IMP-1)- and New Delhi metallo-β-lactamase 1 (NDM-1)-producing P. aeruginosa in Malaysia maybe travel-associated.
Methods: 219 P. aeruginosa isolates were studied: (a) 105 clinical isolates from 1977 to 1985 (n = 52) and 2015 (n = 53), and (b) 114 environmental isolates from different fresh water sources. All isolates were subjected to ERIC-PCR typing, antimicrobial susceptibility testing and virulence factor genes screening.
Results: Clinical and environmental isolates of P. aeruginosa were genetically heterogenous, with only four clinical isolates showing 100% identical ERIC-PCR patterns to seven environmental isolates. Most of the clinical and environmental isolates were sensitive to almost all of the antipseudomonal drugs, except for ticarcillin/clavulanic acid. Increased resistant isolates was seen in 2015 compared to that of the archived isolates; four MDR strains were detected and all were retrieved in 2015. All clinical isolates retrieved from 1977 to 1985 were susceptible to ceftazidime and ciprofloxacin; but in comparison, the clinical isolates recovered in 2015 exhibited 9.4% resistance to ceftazidime and 5.7% to ciprofloxacin; a rise in resistance to imipenem (3.8% to 7.5%), piperacillin (9.6% to 11.3%) and amikacin (1.9% to 5.7%) and a slight drop in resistance rates to piperacillin/tazobactam (7.7% to 7.5%), ticarcillin/clavulanic acid (19.2% to 18.9%), meropenem (15.4% to 7.5%), doripenem (11.5% to 7.5%), gentamicin (7.7% to 7.5%) and netilmicin (7.7% to 7.5%). Environmental isolates were resistant to piperacillin/tazobactam (1.8%), ciprofloxacin (1.8%), piperacillin (4.4%) and carbapenems (doripenem 11.4%, meropenem 8.8% and imipenem 2.6%). Both clinical and environmental isolates showed high prevalence of virulence factor genes, but none were detected in 10 (9.5%) clinical and 18 (15.8%) environmental isolates. The exoT gene was not detected in any of the clinical isolates. Resistance to carbapenems (meropenem, doripenem and imipenem), β-lactamase inhibitors (ticarcillin/clavulanic acid and piperacillin/tazobactam), piperacillin, ceftazidime and ciprofloxacin was observed in some of the isolates without virulence factor genes. Five virulence-negative isolates were susceptible to all of the antimicrobials. Only one MDR strain harbored none of the virulence factor genes.
Conclusion: Over a period of 30 years, a rise in antipseudomonal drug resistance particularly to ceftazidime and ciprofloxacin was observed in two hospitals in Malaysia. The occurrence of resistant environmental isolates from densely populated areas is relevant and gives rise to collective anxiety to the community at large.