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Distribution of MBL and serine-β-lactamase-producing pathogens in ventilator-associated pneumonia: insights into MDR
Zeb Hussain1,2, Asma Naim1, Ambreen Fatima3
1Department of Microbiology, University of Karachi, Karachi, Pakistan.
Background And Objectives:
Ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Gram-negative bacteria 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 carbapenem-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 for 62.7%. 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 prevalence 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 resistance. These findings highlight the urgent need for surveillance, stewardship, and new therapeutic options.
Insights
Ventilator-associated pneumonia (VAP) is a significant ICU threat due to carbapenem-resistant Gram-negative bacteria. This study found Acinetobacter baumannii and Klebsiella pneumoniae as dominant pathogens, highlighting urgent needs for surveillance and new treatments.
Area of Science:
- Infectious Diseases
- Microbiology
- Critical Care Medicine
Background:
- Ventilator-associated pneumonia (VAP) poses a significant challenge in intensive care units (ICUs), particularly when caused by carbapenem-resistant Gram-negative bacteria.
- Carbapenem resistance in Gram-negative pathogens complicates treatment options and increases patient morbidity and mortality.
Purpose of the Study:
- To determine the prevalence of carbapenem-resistant Gram-negative bacteria in VAP patients.
- To analyze the antimicrobial susceptibility profiles of these resistant isolates.
- To identify the phenotypic carbapenemase resistance mechanisms prevalent in these isolates.
Main Methods:
- A prospective study included 104 VAP cases between July 2021 and January 2023.
- Sixty-seven carbapenem-resistant Gram-negative isolates were identified and subjected to antibiotic susceptibility testing using disk diffusion and broth micro dilution.
- Modified and enhanced carbapenem inactivation methods (mCIM/eCIM) were employed to detect metallo-β-lactamase (MBL) and serine carbapenemase production.
Main Results:
- The most common VAP pathogens were *Acinetobacter baumannii* (49.3%) and *Klebsiella pneumoniae* (20.9%).
- Phenotypic analysis revealed that 67% of isolates produced MBLs, and 33% produced serine carbapenemases.
- High prevalence rates of multidrug-resistant (MDR) (42.6%), extensively drug-resistant (XDR) (31.3%), and pan drug-resistant (PDR) (19.4%) phenotypes were observed.
Conclusions:
- VAP in the studied ICUs is predominantly caused by *A. baumannii* and *K. pneumoniae* exhibiting high levels of MBL-mediated resistance.
- The findings underscore the critical need for enhanced surveillance programs, antimicrobial stewardship initiatives, and the development of novel therapeutic strategies to combat these resistant infections.
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