Incrimination of a Single PFGE Type of Acinetobacter baumanii in The Etiology of Ventilator Associated Pneumonia in the Neonatal Intensive Care Unit of Alexandria University Hospital

Background:

Acinetobacter baumanii, a hospital pathogen marred by its MDR and its ability to persist on environmental surfaces, emerged as the most common pathogen incriminated in the etiology of ventilator associated pneumonia in the Neonatal Intensive Care Unit of Alexandria University Hospital.

Objective: To investigate the genetic relatedness of isolates of A.baumannii incriminated in the etiology of VAP in the NICU of AUH

Methods:

All neonates receiving mechanical ventilation from October 2008 to February 2009 were enrolled in the present study. Microbiological investigations included: 1) Samples to identify potential sources of bacterial colonization of the aero-digestive tract: the hands of healthcare personal (HCP),   the inspiratory and expiratory condensate of ventilation circuits, and suction tubes.  2) Samples to monitor aero-digestive colonization: Swabs from oral cavity and gastric aspirate. Collection of samples was initiated within the first 48 hours of mechanical ventilation and repeated every 72 hours until the onset of VAP or cessation of ventilation. 3) Non-bronchoscopic bronchoalveolar lavage (mini-BAL) samples were collected once the CDC clinical criteria of VAP were fulfilled. Microbiological investigation was carried out based on conventional microbiological methods. Antibiotic sensitivity tests were carried out and interpreted by CLSI standards. Acinetobacter isolates were typed using pulse field gel electrophoreisis (PFGE).

Results: Out of 42 clinically diagnosed VAP cases 24 (57%) were microbiologically confirmed. A.baumanii was incriminated in the etiology of 12 cases (50%). Prior to the clinical diagnosis of VAP, A.baumanii was isolated from 11 out of the 12 cases: suction tube (4 cases), expiratory condensate (3), oral cavity (6), gastric juice (3). It was not isolated from hands of HCP or inspiratory condensate and it was not isolated from any sample collected from the enrolled neonates who did not develop VAP. All Acinetobacter isolates were resistant to more than three classes of antibiotics with considerable variability in their MDR phenotypes and two isolates were pan resistant. However PFGE typing indicated that all isolates belonged to a single PFGE type.

Conclusions:

The persistence of a single PFGE type of A.baumanii throughout the study period dictates the need for instituting strict compliance with environmental decontamination and infection control measures to confront the imminent threat of untreatable infections caused by A.baumannii. Antibiotic sensitivity patterns are poor predictors of genetic relatedness of isolates. The results of this study also highlight the role of aerodigestive colonization in the pathogenesis of VAP the monitoring of which may support early prediction and intervention to improve the clinical outcome of the ventilated neonates.