Identification and Antibiogram of Clinically Relevant Non-Diphtheriae <i>Corynebacterium</i> species

Abstract Background and Objectives With the increase in immunosuppressed patients and antimicrobial misuse, Non-diphtheriae Corynebacterium species (NDC spp.) have risen as opportunistic pathogens in hospitalized patients. The present study aimed at comparing Vitek 2C automated identification cards versus MALDI-TOF as the gold standard method for the identification of different NDC spp. and determining the antimicrobial susceptibility of NDC spp. by the disc diffusion method for proper management of patients. Materials and Methods The study included 30 NDC spp. isolates recovered from different samples and were subjected to identification by MALDI-TOF and Vitek 2C. The disc diffusion method was performed to determine the antimicrobial susceptibility of the following antibiotics: pencillin G, tetracycline, gentamicin, ciprofloxacin, vancomycin, and Linezolid. Results Our study showed that Corynebacterium striatum (C. striatum) was the most commonly isolated species (83.3%), followed by C. amycolatum (10%). 36.7% of the isolates were recovered from blood culture while 20 % were recovered from deep wounds. The age of the patients included in the current study ranged from 55 to 85 years with a mean of 46.7 years. 56.7 % of the isolates were collected from female patients and 43.3% from male patients. As Regard isolate identification by Vitek-2C ANC ID CARD compared to MALDI-TOF (matrix-associated laser-induced desorption ionization-time of flight) as the gold standard method, the agreement was 86.7%. Regarding the antimicrobial susceptibility by disc diffusion method, all the isolates showed increased resistance against pencillin (100%), ciprofloxacin (70%), gentamicin (93.3%), tetracycline (76.6%), and clindamycin (70%). On the other hand, vancomycin and linezolid showed promising results where 100 % of the isolates were susceptible. Conclusion We spotlight that NDC spp. should no longer be considered contaminant bacteria in cultures, particularly in immunosuppressed patients. Timely identification, proper clinical correlation, and appropriate therapeutic intervention can lead to favorable outcomes. The high resistance to multiple classes of antibiotics as compounds of the MLSB group, fluoroquinolones, tetracyclines, and β- lactams, thus potentially limiting effective empirical treatment. However, vancomycin and linezolid are still effective against 100 % of the isolates.