title: Evaluation of the virulence markers in the clinical isolates of citrobacter species: the first report from India.
abstract: BACKGROUND
  Citrobacter, a gram negative bacillus, is emerging as one of the major pathogens in hospital settings, with a potential to cause serious infections. Virulence markers are the factors which enhance the survival ability of the micro-organisms. Among the gram negative bacilli, these have been extensively studied in Escherichia coli. To the best of our knowledge as per internet search, we report that this study has been done for the first time in India on Citrobacter.
  
  
  OBJECTIVE
  An investigation was done to determine the ability of Citrobacter in producing virulence markers like the ability to survive the serum bactericidal activity, the resistance to the intracellular killing in the Polymorphonuclear Leucocytes (PMNLs) and the Cell Surface Hydrophobicity (CSH).
  
  
  METHODS
  This prospective study was conducted in the Department of Microbiology of a tertiary care hospital in Aligarh, India, for a period of one year and six months.
  
  
  METHODS
  A total of 105 clinical isolates and 20 control isolates from healthy subjects were identified as having Citrobacter spp. by using standard biochemical tests and they were studied for the presence of virulence markers like the ability to survive the serum bactericidal activity, the resistance to the intracellular killing in the Polymorphonuclear Leucocytes (PMNLs) and the cell surface hydrophobicity. The statistical analysis which was used: The standard deviations and the p-values were calculated for comparison.
  
  
  RESULTS
  Out of the 105 clinical isolates of Citrobacter which were studied, 86.6% isolates were resistant to 100% serum after 180 minutes of incubation and intracellular killing in PMNL was demonstrated in 17% strains. The Salt Aggregation Test (SAT) for the cell surface hydrophobicity was positive in 17.1% strains at different concentrations of ammonium sulphate. The presence of more than one virulence marker was present in 71.4% of the clinical isolates while in the control isolates.
  
  
  CONCLUSIONS
  The presence of the virulence markers in Citrobacter demonstrated its pathogenic potential. Its invasiveness and ability to disseminate can be studied by identifying these markers.
authors.affiliation: Senior Resident, Department of Microbiology, Dr Baba Saheb Ambedkar Hospital , Rohini, Delhi-85, India .
authors.forename: Ritu
authors.initials: R
authors.lastname: Nayar
authors.forename: Indu
authors.initials: I
authors.lastname: Shukla
authors.forename: S Manazir
authors.initials: SM
authors.lastname: Ali
keywords: Cell surface hydrophobicity; Citrobacter; Intracellular PMNL killing; Serum resistance
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