Association between antibiogram and molecular detection of meca or mecc gene from methicillin-resistant coagulase negative staphylococcal species in two government hospitals in Kuantan, Malaysi

Abstract

In the last two decades, the emergence of nosocomial infections caused by CoNS has led clinicians and researchers to reconsider the role of CoNS and methicillin-resistant CoNS (MR-CoNS) as important agents of nosocomial infections. Because their natural habitat is skin, they may contaminate clinical samples causing suspicion as to whether an isolate is causing true infection or is a mere contaminant. The present study was conducted on clinical isolates of MR-CoNS obtained from inpatients in Tengku Ampuan Afzan Hospital (HTAA) and International Islamic University Malaysia Medical Center (IIUM-MC) to determine their antimicrobial resistance profile and the presence of mecA or mecA homologue (mecC gene). The isolates were cultured from clinical samples of blood, tissues, and swabs. A total of 40 isolates (33 blood, 4 tissues, and 3 swabs) of MR-CoNS were collected through venepuncture, biopsy, and swabbing techniques respectively, and processed by conventional cultural and biochemical methods, antimicrobial susceptibility tests, and finally confirmation to the species level was done by using conventional PCR assay for known four common clinical species. Of all 40 isolates, Staphylococcus haemolyticus was the most commonly found species (13/40, 32.5%), followed by S. hominis (12/40, 30%). S. epidermidis and S. saprophyticus were not identified in the samples. MR-CoNS isolated from blood included S. haemolyticus (12/40, 30%) and S. hominis (12/40, 30%), while 10 (40%) were unidentified. For swabs, only 1 (2.5%) isolate was identified as S. haemolyticus, and 1 (2.5%) was unidentified. For tissues, none of the 4 (10%) isolates tested positive for any of the 4 MR-CoNS. Methicillin- and vancomycin-resistance profile of the isolates was performed by E-test and broth micro-dilution methods. Of the 40 isolates, 38 were identified to be methicillin-resistant (MIC  0.5 µg/mL). The remaining 2 isolates were considered as susceptible to methicillin (MIC ≤ 0.25). All 40 isolates were found to be susceptible to vancomycin, with MIC ranging from 1-4 µg/mL. All 40 isolates were also tested for phenotypic antimicrobial susceptibility profile using the Kirby and Bauer disc diffusion method. Resistance rates to linezolid, erythromycin, ciprofloxacin, and ceftaroline were found to be 100%. Resistance rates to trimethoprim-sulfamethoxazole, teicoplanin, and clindamycin were found to be 82.5%, 92.5%, and 97.5% respectively. Thus, all the isolates revealed multi-drug resistance profiles to more than three antimicrobials, the highest being resistance to 9 antibiotics. All tested isolates showed multi-drug resistance profile to more than 3 antimicrobials except one isolate from swab. Detection of the mecA (or mecC) gene was performed by conventional PCR assay. Only mecA was identified in the 38 MR-CoNS isolates (95%). The other 2 isolates (5%) that were identified to be methicillin-sensitive by the E-test, also tested negative for the presence of the mecC gene, thus confirmed to be non-methicillin resistant. The high percentage of multi-drug resistance among these MR-CoNS isolates points toward the need for periodic antibiogram surveillance as they are identified to cause difficult to treat infections.