Phenotypic and genotypic detection of antibiotic resistance among metallo-beta-lactamases producing Klebsiella pneumoniae strains isolated from patients in Intensive Care Units in Shiraz, Iran

Abstract

Klebsiella pneumoniae is the opportunistic pathogen which is responsible for infections in the hospital intensive care units (ICUs). Increase in the rate of carbapenemase-producing Enterobacteriaceae, is a major concern. The aims of this study were to identify metallo-beta-lactamases (MBL)-producing K. pneumoniae isolates and detect their antibiotic susceptibility pattern. Antibacterial susceptibility testing was performed for 8 antibiotics, using disk diffusion method according to CLSI guidelines. Isolates showing resistance to at least one of the carbapenem antibiotics were then evaluated for production of metallo-beta-lactamase enzymes, using combination disk method. The presence of the blaIMP, blaVIM, and blaSPM genes was assessed by PCR. Out of 150 examined isolates, 24 isolates (16%) were resistant to imipenem and 18 (12%) to meropenem. All of these isolates were resistant to more than three different classes of antibiotics. Of the 24 K. pneumoniae isolates that were resistant to carbapenem, just 3 (12.5%) were positive MBLs. Twenty-one (14%) of 150 isolates had positive results for IMP, 2 (1.3%) for VIM, while none of the isolates were positive for SPM metallo-beta-lactamase gene. MBLs have expanded worldwide and MBL-producing isolates which make the treat of infections associated with high mortality rates difficult; therefore, this study focused on the implementation of infection control practices against enhanced antibiotic resistance.