Antimicrobial Resistance and Distribution Of mecA Gene among Clinical and Carriage Coagulase Negative Staphylococci Isolates

Abstract

Background; In most laboratories, Coagulase Negative Staphylococci (CoNS) are treated as contaminants and therefore follow ups with regards to species detection and antimicrobial susceptibilities are not done. There is a growing incidence of antimicrobial resistant CoNS across the globe making infections difficult to treat. Data on these resistant pathogens are limited in Africa in general and Ghana in particular. It is therefore important to characterize CoNS with respect to their antimicrobial susceptibilities to guide treatment decisions, locally and at national levels. Aim; This research was undertaken to determine the antimicrobial resistant patterns and the distribution of mecA gene in a collection of CoNS isolated from clinical and carriage specimens. Methodology; Forty CoNS recovered from clinical (mainly from blood, urine, skin and soft tissue infections), and carriage (nasal isolates from asymptomatic hospital staff and inpatients) sources in a previous study conducted between the periods of October 2010 to June 2012 were included in this project. Identification of bacteria species was performed by Gram staining, catalase testing, coagulase testing, and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry (MALDI-TOF- MS). Antimicrobial susceptibility testing was done in a disk diffusion assay using 12 antimicrobial agents and interpreted according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guideline. Detection of mecA gene was done in a Polymerase Chain Reaction using published primers. Results; CoNS from clinical specimens were Staphylococcus haemolyticus (n=11;27.5%), Staphylococcus saprophyticus (n=6; 15%), Staphylococcus sciuri (n=5;12.5%), Staphylococcus hominis (n=3; 7%), Staphylococcus xylosus (n=2; 5%) and Staphylococcus kloosii (n=1; 2.5%). Those from carriage sources were Staphylococcus epidermidis (n=11;27.5%)and Staphylococcus cohnii (n=1; 2.5%). Isolates were frequently resistant to penicillin (100%), cefoxitin (53.6%), fusidic acid (48.7%), norfloxacin (46%), gentamicin (46%), clindamycin (44%) and erythromycin (44%). Multi drug resistance was detected among 62.5% of the isolates. mecA gene was detected in 40% of the CoNS; majority (62.5%) of which were found in isolates from clinical infections. Conclusion; To conclude, the prevalence in the number of CoNS species identified using the MALDITOF/MS (the first of its kind in Ghana) was moderate but there was a high level of resistance detected among the CoNS to commonly used antimicrobial agents coupled with a significant occurance of the mecA gene among isolates. This calls for regular surveillance of these resistant pathogens to guide treatment decisions locally and at national levels.