Antimicrobial resistance in bacteria causing ventilator-associated pneumonia in a tertiary care hospital: one year prospective study

Neelima Ranjan, K. P. Ranjan, Uma Chaudhary, Dhruva Chaudhry


Background: Ventilator-associated pneumonia (VAP) is the most common infection diagnosed in intensive care units (ICUs). The causative organisms of VAP vary among different populations and are increasingly associated with resistance against various antimicrobial agents. Objective of current study was to determine the bacteriological etiology of VAP, antimicrobial susceptibility pattern of the isolates and detect the presence of extended-spectrum b-lactamases (ESBL), metallo β-lactamases (MBL) and AmpC b-lactamases in multidrug resistant isolates causing VAP in the medical ICU.

Methods: A prospective study was carried out over a year to know the various etiological agents of VAP and their drug susceptibility patterns. ESBL, MBL and AmpC b-lactamases were detected in various isolates by combination disk method, imipenem-EDTA combined disk method and AmpC disk method respectively.

Results: The majority of bacterial isolates causing VAP were found to be gram negative bacilli. Acinetobacter spp accounted for 34.28% of VAP cases followed by Pseudomonas aeruginosa which was responsible for 25.71% cases. Other gram negative bacilli isolated were Klebsiella pneumoniae, Citrobacter freundii, Enterobacter spp, and Escherichia coli. Out of the total 70 isolates, 67 (95.7%) were multidrug resistant and not even a single isolate was sensitive to all the drugs tested.

Conclusions: Most of the pathogens causing VAP in our institute were multidrug resistant and in many isolates this resistance was due to production of ESBL, MBL, and AmpC β-latamases. Polymixin-B and colistin were found to be highly effective against multidrug resistant Acinetobacter spp and P. aeruginosa.



Ventilator-associated pneumonia, Intensive care unit, ESBL, MBL, AmpC b-lactamases

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