A study on nosocomial pathogens in ICU with special reference to multiresistant Acinetobacter baumannii harbouring multiple plasmids

Abstract

Background & objectives: Antibiotic resistant bacterial nosocomial infections are a leading problem in intensive care units (ICU). Present investigation was undertaken to know antibiotic resistance in Acinetobacter baumannii and some other pathogens obtained from clinical samples from ICU causing nosocomial infections. Special emphasis was given on plasmid mediated transferable antibiotic resistance in Acinetobacter.

Methods: The clinical specimens obtained from ICU, were investigated to study distribution of nosocomial pathogens (272) and their antibiotic resistance profile. Acinetobacter isolates were identified by API2ONE system. Antimicrobial resistance was studied with minimum inhibitory concentration (MIC) by double dilution agar plate method. The plasmid profile of 26 antibiotic resistant isolates of Acinetobacter was studied. Curing of R-plasmids was determined in three antibiotic resistant plasmid containing A. baumannii isolates. Plasmid transfer was studied by transformation.

Results: Major infections found in ICU were due to Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pyogenes. The infection rate was maximum in urinary tract (44.4%) followed by wound infections (29.4%), pneumonia (10.7%) and bronchitis (7.4%). Acinetobacter isolates displayed high level of antibiotic resistance (up to 1024microg/ml) to most of antibiotics. More than 90 per cent isolates of Acinetobacter were resistant to a minimum of 23 antibiotics. Plasmid profile of Acinetobacter isolates showed presence of 1-4 plasmids. Ethidium bromide cured plasmids pUPI280, pUPI281, pUPI282 with curing efficiencies 20, 16 and 11 per cent respectively while acridine orange cured plasmids pUPI280, pUPI281 with curing efficiencies 7 and 18 per cent retrospectively. Transformation frequency of E. coli HB101 with pUPI281 was 4.3 x 10(4) transformants/microg plasmid DNA.

Interpretation & conclusions: A. baumannii was found to be associated with urinary tract infections, respiratory tract infections, septicaemia, bacteraemia, meningitis and wound infections. A. baumannii displayed higher resistance to more number of antibiotics than other nosocomial pathogens from ICU. Antibiotic sensitivity of A. baumannii cured isolates confirmed plasmid borne nature of antibiotic resistance markers. Transfer of antibiotic resistant plasmids from Acinetobacter to other nosocomial pathogens can create complications in the treatment of the patient. Therefore, it is very important to target Acinetobacter which is associated with nosocomial infections.