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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 microorganisms. 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.Aims: 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). Settings and Design: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. Material and 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 inCitrobacter demonstrated its pathogenic potential. Its invasiveness and ability to disseminate can be studied by identifying these markers.

The ability of microbes to resist or neutralize the action of drugs that have been used against microbes is considered as antimicrobial resistance (AMR). AMR among different strains of Escherichia coli is considered as a major threat to public health. Drug-resistant in E. coli is found predominantly in the hospital sittings, in the community, and surrounding environment. It has adopted different defensive strategies to minimize the effects of drugs. Extended-spectrum β-lactamase (ESBL), fluoroquinolones, and carbapenemases have been considered as strong resistance strategies being present in most of resistant bacterial strains. Mobile genetic elements (MGEs) have the major contribution in the transfer of resistance genes in between or among bacterial cells. Plasmids are normally present in most of resistant strains, helping in the transfer of genetic material between bacterial cells. Transposons another MGEs, are being considered as one of the major sources of resistance transmission. Collectively, MGEs play an important role in facilitating in exchange, acquisition, and dissemination of resistance genes. Resistance in E. coli has been reported worldwide and there is variation in its resistance pattern. CTX-M ESBLs, carbapenems, colistin-resistant, and ST-131 E. coli resistant clones are considered the most dominant phenotypes. The aforesaid resistant variants are predominantly found in densely populated regions, Sub-Saharan Africa, China, and South Asian countries.

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