The First Study of Investigation of Clinical Isolates of Alcaligenes Xylosoxidans and Alcaligenes Faecalis by Phenotypic and Genetic Methods in Iran

Background and Objective: Alcaligenes sp. is a non-fermentative Gram-negative bacillus, which causes nosocomial infections, including urinary tract infections, pneumonia, sepsis, and may be confused with Pseudomonas aeruginosa. Alcaligenes infections usually are not well identified and due to possible errors and similarities with Pseudomonas, their diagnosis with phenotypic tests is not sufficient. In this case, molecular methods seem to be more effective. We aimed to investigate the real presence of clinical isolates of  Alcaligenes xylosoxidans and  Alcaligenes faecalis by phenotypical, and genetic methods and their antibiotic susceptibility. Materials and Methods: From September 2019 to March 2020, we analyzed 36 clinical isolates from a Sina hospital in Hamadan, Iran, which have been identified as Alcaligenes in the hospital's microbiology lab, by routine phenotypicall methods. Using the PCR method and tracking AX and 77F-r genes, we identified A. xylosoxidans and A. faecalis respectively; the antibiotic resistance of each isolate was determined by the disc diffusion method. Results: Of 36 samples of phenotypically identified Alcaligenes, only 13 (36.11%) were confirmed as A. xylosoxidans and 3 (8.33%)  as A. faecalis by PCR test. Among A. xylosoxidans isolates, the highest susceptibility(92.3%) was against cephalosporin and the highest resistance (76.92%) was against ciprofloxacin. Among A. faecalis isolates, the most susceptibility (100%) was against ceftazidime, piperacillin/tazobactam, imipenem, meropenem, and cefepime, and the most resistance (66.66%) was against gentamicin and ceftriaxone. Conclusion: Regarding the importance of accurate diagnosis of Alcaligenes in combating nosocomial infections, it seems with phenotypic and biochemical tests, there is a possibility of error in their diagnosis; so using the PCR method, each species can be determined more accurately.