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

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.

Species distribution and physiological characterization of Acinetobacter genospecies from healthy human skin of tribal population in India.

BACKGROUND: Various reports on distribution of Acinetobacter spp. from healthy human skin restricted to urban population. However, no such data is available from healthy human skin of tribal population not exposed to modern antibiotics during their life time. PURPOSE: Isolation, biotyping, distribution and physiological characterisation of Acinetobacter spp. from healthy human skin of tribal population. METHODS: Tribal population of Toranmal area of Satpuda Ranges, Maharashtra, India were sampled for ten body sites. Tentative Acinetobacter isolates were confirmed to the genus level by chromosomal DNA transformation assay and to species level using Bouvet and Grimont system. Novel physiological characteristics like pH, temperature and salt tolerance were studied. All strains were screened for production of various enzymes. RESULTS: One hundred and eighteen strains were isolated, which belonged to nine Acinetobacter genospecies. A. haemolyticus was most abundant followed by A. calcoaceticus and A. genospecies 1-3. Higher percentage of Acinetobacter was recovered from skin of nose, Pawara tribe and female volunteers. They showed wide variation in temperature, salt and pH tolerance. Most of the strains could produce enzymes viz, lipase, esterase, urease and amylase. CONCLUSIONS: Acinetobacter spp. belonging to nine genospecies were obtained in the present study. Physiological characteristics including high salt, temperature and acidic pH tolerance were helpful to differentiate between the commensal and pathogenic species of Acinetobacter genus.

Distribution and in vitro antimicrobial susceptibility of Acinetobacter species on the skin of healthy humans.

BACKGROUND: Acinetobacter spp. are ubiquitous in the environment and have emerged as important nosocomial pathogens. The distribution of Acinetobacter spp. In some temperate European countries has been reported. However, similar data from a tropical country such as India are not available. METHODS: Six body sites (antecubital fossa, axilla, forehead with hairline, neck, outer surface of nose and toe webs) from men and women volunteers were sampled with saline-soaked cotton swabs enriched in Baumann's enrichment medium. The isolates were identified to the genus level by chromosomal DNA transformation assay and to the species level by a 16-test biochemical system. The minimum inhibitory concentration for 39 antibiotics was determined by the two-fold agar dilution method. RESULTS: Seven genospecies of Acinetobacter were found at 6 body sites on healthy human skin. Acinetobacter lwoffii was the most dominant comprising 40% of the total number of isolates, followed by A. junii (35%) and A. haemolyticus (16.5%). The antecubital fossa had the highest colonization frequency (48.5%). The overall positivity rate of samples was higher from women (26.3%) compared to men volunteers (25%). Only two Acinetobacter genospecies 1-3 isolates were isolated while no A. radioresistens were isolated. Susceptibility testing revealed no major differences among the 7 Acinetobacter spp. tested. Fluoroquinolones were the most active, while low-to-intermediate resistance was exhibited towards beta-lactams and aminoglycosides. Acinetobacter spp. isolated from the skin showed susceptibility to commonly used antibiotics. CONCLUSION: Seven Acinetobacter genospecies were isolated from 6 different body sites from the skin of healthy human volunteers. Acinetobacter lwoffii was the dominant isolate. The rate of skin carriage was higher in men than in women and the maximally colonized site was the antecubital fossa. All the genospecies displayed susceptibility to most of the commonly used antimicrobials.