title: Aetiological agents of ventilator-associated pneumonia and its resistance pattern - a threat for treatment.
abstract: BACKGROUND
  Ventilator-associated pneumonia (VAP) is a common type of nosocomial pneumonia encountered in intensive care units. There are several aetiological agents which make treatment challenging. Improper antibiotic treatment of ventilated patients may lead to the emergence of multidrug resistant (MDR) pathogens.
  
  
  METHODS
  A prospective study was performed over a period of 20 months. Our study had two arms: the first, 'Incidence and risk factors of VAP in a tertiary care hospital' was the subject of an earlier publication; we therefore present the second investigative arm in this work. The aetiological agents of patients on mechanical ventilation (MV) were identified by standard bacteriological method. The susceptibility pattern was evaluated by Kirby-Bauer disc diffusion method. Extended spectrum beta lactamase (ESBL) testing was performed by combination disc method, and metallo-beta lactamase (MBL) testing was performed by EDTA disk synergy test (EDS).
  
  
  RESULTS
  Late-onset VAP was associated with Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli, while early-onset VAP was commonly caused by members of Enterobacteriaceae, Candida albicans and Staphylococcus aureus. 72.2 per cent of VAP patients had monomicrobial and 27.8 per cent had polymicrobial infection. Out of the 24 isolates obtained from patients with VAP, seven (29.2 per cent) were MDR pathogens. ESBL and MBL production was detected in 40 per cent and 20 per cent of Klebsiella pneumoniae isolated in our study. Around 50 per cent of isolates associated with late-onset VAP were MDR, while 22.2 per cent isolates obtained from patients with earlyonset VAP were MDR.
  
  
  CONCLUSIONS
  VAP is a nosocomial pneumonia that is common among ventilated patients. The aetiological agents vary from common organisms to MDR pathogens that are difficult to treat. A proper knowledge of MDR pathogens and early isolation followed by prevention of prolonged antibiotic therapy can reduce the mortality of late onset VAP.
authors.affiliation: Departments of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India.
authors.forename: Mv Pravin
authors.initials: MP
authors.lastname: Charles
authors.forename: Joshy M
authors.initials: JM
authors.lastname: Easow
authors.forename: Noyal M
authors.initials: NM
authors.lastname: Joseph
authors.forename: M
authors.initials: M
authors.lastname: Ravishankar
authors.forename: Shailesh
authors.initials: S
authors.lastname: Kumar
authors.forename: Umadevi
authors.initials: U
authors.lastname: Sivaraman
keywords: Ventilator associated pneumonia; aetiology; drug resistance