In vitro resistance pattern of Citrobacter infections: A retrospective study

Background: Citrobacter infections are associated with a high mortality rate of about 33-48% if infected patients develop bacteremia. This is partly due to high prevalence of intrinsic resistance, extended spectrum beta lactamases and inducible chromosomal Amp C beta lactamases in Citrobacter spp. thus limiting the therapeutic options. We undertook this study to throw light on the current scenario of infection with this organism. Materials and methods: This retrospective study was conducted over a period of 1 year in Microbiology laboratory of a tertiary care teaching hospital in Eastern part of India. From various samples, 146 clinically significant Citrobacter spp. identified by standard biochemical tests and susceptibility testing performed by Kirby Bauer’s disc diffusion method were included in this study. Results: Majority of patients age ranged of 41-50 year. The highest number (70/146, 47.9%) of Citrobacter spp. was isolated from pus and wound swabs followed by urine (46/146, 31.5%) and out of these, 51.4% strains were of Citrobacter koseri whereas 48.6% were of Citrobacter fruendii. Of Citrobacter isolates 36.6% were ESBL producers. They showed 54.1%, 37.9%, 47.1%, 39.8% and 58.5% resistance to imipenem, netilmycin, piperacillin tazobactam, minocycline and levofloxacin respectively. We also found 9.6% and 28.4% strains of Citrobacter spp. being resistant to colistin and tigecycline respectively. Conclusion: Citrobacter spp. showed high degree of resistance to carbapenem and there were colistin resistance strains as well. This study reiterates the emerging resistance in these supposedly low virulence microbes which may pose future challenge in infection control activities.