The bad, the ugly and the demon: a tale of extensively drug-resistant, extended-spectrum-beta-lactamase- and metallo-beta-lactamase-producing superbugs associated with nosocomial pneumonia

ObjectiveTo determine the bacterial etiology of nosocomial pneumonia (NP) and to assess the current levels of antimicrobial resistance with special reference to the status of extended-spectrum-beta-lactamase (ESBL) and metallo-beta-lactamase (MBL)-producing bacterial strains in a university hospital of Nepal.MethodsA total of 60 specimens (sputum and endotracheal secretion) from patients diagnosed of NP were collected and processed following standard methodology. Combined disk and double disk synergy test method were used for the detection of ESBL. Ethylene-diamine-tetraacetic acid-based combined disk method was used for the detection of MBL-producing isolates.ResultsOut of total 60 specimens, 85% yielded significant mixed bacterial growth. Acinetobacter spp. was the most predominant isolate (30.43%) followed by Klebsiella spp. (28.98%), Pseudomonas aeruginosa (17.39%), Escherichia coli and Staphylococcus aureus (S. aureus) (8.69% for each). All Escherichia coli, Klebsiella spp. and S. aureus were multidrug resistant. Nearly 76% of Acinetobacter spp. were extensively drug resistant. MBL was seen in 25.3% of the Gram-negative isolates. Acinetobacter spp. was the most frequent MBL-producer (15.9%). ESBL was present in 41.3% of Gram-negative isolates. Tigecycline and polymyxin B followed by carbapenems, cefoperazone-sulbactam, piperacillin-tazobactam and amikacin were the most effective antibiotics for drug-resistant Gram-negative bacteria. All isolates of S. aureus were methicillin-resistant; however, they were susceptible to vancomycin, linezolid, quinupristin-dalfopristin and tigecycline.ConclusionsHigh prevalence of drug resistance among the isolates of NP has demanded cautious selection of antibiotics. Further studies should be done in our setting to find out genes responsible for drug resistance. Last but not least, we advocate for the development of new antibiotics.