Metallo-β-lactamase mediated rapid increase in carbapenem resistance of Pseudomonas aeruginosa

Antibiotic-resistant Pseudomonas aeruginosa is a common nosocomial pathogen all over the world. We detected the presence of P. aeruginosa in 22% (53 out of 238) of the test samples collected from patients with infections including secondary wound infections, abscesses and urinary tract infections admitted to two academic hospitals in Bangladesh. Resistance to carbapenems (imipenem, and meropenem) was present among 30% (16 out of 53) of these clinical P. aeruginosa isolates, which is more than 2-fold higher compared to that of previous studies. Such a rapid increase in carbapenem resistance was mediated by metallo-β-lactamase (MBL). Expression of MBL was detected in 90% (14 out of 16) of these resistant isolates. Molecular analyses revealed that the carbapenem-resistant isolates carried at least one of the MBL variants, either bla- VIM or bla -NDM-1. All the bla- NDM-1 positives carried a 0.5 MDa plasmid. ERIC-PCR revealed the highly heterogeneous nature of the P. aeruginosa isolates indicating multiple sources of infection within the hospital. However, the majority of XDR isolates belonged to a single cluster of drug-resistant bacterial infections. These findings indicate that Metallo-β-lactamase (MBL) mediated resistance to carbapenem in P. aeruginosa poses a serious threat to the spread of infections among hospitalized patients.