الفهرس 
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Abstract
Non diphtheriae Corynebacteria are usually commensals of the skin and mucous membranes. They differ from C. diphtheriae in biochemical reactions as well as in toxin production. Since, they are usually found as commensals on the skin, they are often considered as mere contaminants when isolated from clinical samples. However, there are increasing reports of these organisms being associated with various infections.
Many predisposing factors responsible for human infections with NDC spp. Including immunocompromized patients (malignancy), patients on medical device, patients receiving broad spectrum antimicrobial therapy and after invasive procedures. Some of the species like C. jeikeium and C. urealyticum can cause infections among immune-competent persons and are true pathogens.
Phenotypic identification of NDC remains routinely problematic in clinical diagnostic laboratories and most of the isolates remain identified only to the genus level. Accurate identification of the coryneform clinical isolates is important for treatment purposes because some of the species, like C. striatum, C. amycolatum, C. jeikeium and C. urealyticum, are highly resistant to antibiotics. Among the automated identification systems available recently API coryne strip and VITEK 2C ANC card. Another advanced method for identification of NDC is the use of matrix- associated laser- induced desorption ionization - time of flight Mass Spectroscopy (MALDI-TOF MS).
Emergence of antimicrobial resistance among various species of NDC demands their species level identification. But identification of NDC to species level by routine as well as reference laboratories is confounded even after consulting all the available identification schemes.
The present study was conducted during the period between December 2018 and December 2019 in Ain shams university hospitals. A total of 30 NDC spp. isolates were recovered from different clinical specimens submitted to the main Microbiology Laboratory, Ain Shams University Hospitals for routine culture and antimicrobial susceptibility testing.
Isolates of NDC spp. were identified phenotypically following the microbiology laboratory procedures (Gram stain, catalase and urease) and were subjected to further subspecies identification by MALDI-TOF and Vitek 2C ID cards and also their susceptibility to different antimicrobial agents was done by Disc diffusion method in accordance to the recommendations of the (EUCAST, 2018) to suggest recommendation for NDC treatment.
Regarding the type of samples, 36.7 % (11/30) were isolated from blood culture, 20% (6/30) were isolated from deep wound, 16.7 % (5/30) were isolated from sputum culture, 16.7 % (5/30) were isolated from urine culture, 6.7 % (2/30) were isolated from central line culture, and 3.3 % (1/30) was isolated from cerebrospinal fluid (CSF) culture.
The age of the patients included in the current study ranged from 55 to 85 years with mean of 46.7 years.
As for the departments, 63% (19/30) of isolates were collected from ICU patients, 10% (3/30) from oncology department patients, 7% (2/30) from geriatrics department patients, 7% (2/30) from haematology department patients, 7% (2/30) from pediatric department patients, 3% (1/30) from urology department patients, and 3% (1/30) from neurosurgery department patients.
Seventeen out of 30 isolates (17/30, 56.7 %) were collected from female patients and 13 (13/30, 43.3%) from male patients.
In the present study, the results of identification of 30 isolates of NDC spp. by Vitek-MS revealed that 25/30 (83.3%) were C. striatum, 3/30 (10%) were C. amycolatum, 1/30 (3.3%) was C. jeikeium, and 1/30 (3.3%) was C. afermentans .
Vitek 2C system by ANC cards revealed that 73.3 % (22/30) were C. striatum, 10% (3/30) were C. amycolatum, 3.3% (1/30) was C. jeikeium, 6.7% (2/30) were Turicella otitidis, and 6.7% (2/30) were unidentified.
A statistically excellant agreement (86.7%, 26/30) was observed between vitek MS and Vitek 2C system method regarding the identification results of the NDC spp.
As regards the antimicrobial susceptibility by Disc diffusion method, the tested isolates exhibited the highest resistance against pencillin (100 %). On the other hand Vancomycin and Linezolid showed promising results where 100 % of the isolates were susceptible