Distribution of MBL and serine-β-lactamase-producing pathogens in ventilator-associated pneumonia: insights into MDR and XDR strains

Zeb  Hussain; Asma  Naim; Ambreen  Fatima; Asad  Karim; Fakhur  Uddin; Surraya  Shams

doi:10.18502/ijm.v17i5.19885

Zeb Hussain Department of Microbiology, University of Karachi, Karachi, Pakistan
Asma Naim Department of Microbiology, University of Karachi, Karachi, Pakistan
Ambreen Fatima Department of Pathology, Dow International Medical College, Dow University of Health Sciences, Karachi, Pakistan
Asad Karim Department of Molecular Medicine, Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
Fakhur Uddin Department of Molecular Medicine, Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
Surraya Shams Department of Clinical Laboratory Sciences, Dow Institute of Medical Technology, Dow University of Health Sciences, Karachi, Pakistan

DOI: https://doi.org/10.18502/ijm.v17i5.19885

Keywords: Ventilator-associated pneumonia; Carbapenems; Raoultella terrigena; Elizabethkingia meningoseptica; Drug resistance; Bacterial

Abstract

Background and Objectives: Ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Gram-negative bac- teria is a serious ICU challenge. This study determined the prevalence, antimicrobial susceptibility profiles, and phenotypic carbapenemase resistance mechanisms of Gram-negative isolates from VAP patients in two tertiary hospitals in Karachi, Pakistan.

Materials and Methods: We included 104 consecutive cases of VAP (July 2021–January 2023). A total of 67 carbapen- em-resistant Gram-negative isolates were identified and tested. Antibiotic susceptibility was assessed by disk diffusion and broth micro dilution, according to CLSI and EUCAST guidelines. Modified and enhanced carbapenem inactivation methods (mCIM/eCIM) were used to distinguish metallo-β-lactamase (MBL) and serine carbapenemase production.

Results:The mean age was 44.6 ± 18.3 years; 52.2% were male. Early-onset VAP accounted for 37.3% and late-onset for62.7%. The most frequent pathogens were Acinetobacter baumannii (49.3%, 33/67) and Klebsiella pneumoniae (20.9%,14/67). Notably, 67% of isolates produced MBLs, and 33% produced serine carbapenemases (phenotypically). The preva-lence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan drug-resistant (PDR) phenotypes was 42.6%,31.3%, and 19.4%, respectively.

Conclusion: VAP in our ICUs was dominated by A. baumannii and K. pneumoniae with high levels of MBL-mediated resis- tance. These findings highlight the urgent need for surveillance, stewardship, and new therapeutic options.