Molecular Characteristics and Antimicrobial Susceptibility Profile of Pseudomonas aeruginosa isolated from patients attending Healthcare Facilities in Mthatha, South Africa

Abstract

Background Pseudomonas aeruginosa is a common pathogen causing healthcare-associated infections most especially in critically ill and immunocompromised patients. This pathogen poses a public health threat due to its innate resistance to many antimicrobial agents and its ability to acquire new resistance mechanisms under pressure. Infections with Extended spectrum β-lactamases (ESBL)-producing isolates result into outbreaks that lead to serious antibiotic management concerns with higher mortality and morbidity and significant economic causatives. In this study, we evaluated the antimicrobial resistance patterns and characterized genetically the ESBLs and Metallo- β-lactamases (MBL) produced by this pathogen. Methods Isolates of P. aeruginosa cultured from patients who attended Nelson Mandela Academic Hospital and other clinics in the four district municipalities of the Eastern Cape between August 2017 and May 2019 were identified; and their antibiotic resistance patterns were tested against amikacin, aztreonam, cefepime, ceftazidime, ciprofloxacin, doripenem, gentamicin, imipenem, levofloxacin, meropenem, piperacillin, piperacillin/tazobactam and tobramycin using the bioMérieux VITEK® 2 and confirmed by Beckman autoSCAN-4 System. Real-time PCR was done using Roche Light Cycler 2.0 to detect the presence of ESBLs; blaSHV, blaTEM and blaCTX-M genes; and MBLs; blaIMP, blaVIM. Results High antibiotic resistance in decreasing order was observed in piperacillin (64.2%), aztreonam (57.8%), cefepime (51.5%), ceftazidime (51.0%), piperacillin/tazobactam (50.5%), and imipenem (46.6%). A total of 75 (36.8%) multidrug resistant (MDR) isolates were observed of the total pool of isolates. The blaTEM, blaSHV and blaCTX-M was detected in 79.3%, 69.5% and 31.7% isolates (n=82), respectively. The blaIMP was detected in 1.25% while no blaVIM was detected in any of the isolates tested. Conclusions The study showed a high rate of MDR P. aeruginosa in our setting. The vast majority of these resistant isolates carried blaTEM and blaSHV genes. Continuous monitoring of antimicrobial resistance and strict compliance towards infection prevention and control practices are the best defence against spread of MDR P. aeruginosa.