Abstract
Objectives: Citrobacter spp. especially Citrobacter freundii, is frequently causing nosocomial infections, and increasingly becoming multi-drug resistant (MDR). In this study, we aimed to determine the genetic diversity and relationships of Citrobacter spp. from diarrheal patients and food sources, their antimicrobial resistance profiles and in vitro virulence properties.Methods: Sixty two Citrobacter isolates, including 13 C. freundii, 41 C. youngae and eight C. braakii isolates, were obtained from human diarrheal patients and food sources. Multilocus Sequence Typing (MLST) of seven housekeeping genes and antimicrobial susceptibility testing using the broth microdilution method according to CLSI recommendations were carried out. Adhesion and cytotoxicity to HEp-2 cells were performed. PCR and sequencing were used to identify blaCTX−M, blaSHV, blaTEM and qnr genes.Results: The 62 isolates were divided into 53 sequence types (STs) with all STs being novel, displaying high genetic diversity. ST39 was a predominant ST shared by 5 C. youngae strains isolated from four foods and a diarrheal patient. All isolates were resistant to cefoxitin, and sensitive to imipenem, meropenem and amikacin. The majority of Citrobacter isolates (61.3%) were MDR of three or more antibiotics out of the 22 antibiotics tested. Two C. freundii isolates each carried the blaTEM−1 gene and a variant of qnrB77. Three Citrobacter isolates each carried qnrS1 and aac(6')-Ib-cr genes. Seven isolates that showed strong cytotoxicity to HEp-2 cells were MDR.Conclusions: Citrobacter spp. from human and food sources are diverse with variation in virulence properties and antibiotic resistance profiles. Food may be an important source of Citrobacter species in transmission to humans. C. freundii and C. youngae are potential foodborne pathogens.
Highlights
Citrobacter spp. are commensal inhabitants of the intestinal tract of humans and other animals
We identified one cytotoxic and aggregative C. freundii strain and found strains causing diarrheal infections in humans belonged to four sequence types (STs) (Bai et al, 2012)
The 41 C. youngae isolates were divided into 32 STs, 13 C. freundii isolates into 12 STs and eight C
Summary
Citrobacter spp. are commensal inhabitants of the intestinal tract of humans and other animals. They have been recovered from water, sewage, and soil (Nada et al, 2004; Bae et al, 2010). Citrobacter spp. are opportunistic pathogens of humans and have been associated with a range of infections including urinary tract infections (UTIs), gastroenteritis, wound infections, pneumonia, brain abscesses, septicaemia, meningitis, and endocarditis, in particular in neonates and immunocompromised hosts (Doran, 1999). Some C. freundii isolates have acquired virulence traits and caused food poisoning or diarrhea in humans (Bai et al, 2012). C. braakii has been isolated from raw ground beef samples and pork products (Basra et al, 2015; Kwak et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
