Date Published: December , 2017
Publisher: Makerere Medical School
Author(s): Ephraim Ehidiamen Ibadin, Idahosa Onaiwu Enabulele, Fowora Muinah.
The staphylococci have increasingly been associated with infections worldwide and anti-microbial resistance has made these versatile pathogens more recalcitrant in the hospital setting.
This study sought to investigate the occurrence and distribution of Staphylococcus species as well as determine the prevalence of methicillin resistant Staphylococcus aureus (MRSA) and methicillin resistant coagulase negative staphylococci (MRCoNS) among clinical samples from University of Benin Teaching Hospital (UBTH) in Benin City.
Ninety one (91) clinical isolates comprising S. aureus and Coagulase Negative staphylococci (CoNS) were recovered from routine clinical specimens and anti-microbial susceptibility tests were carried out. Polymerase Chain Reaction (PCR) was thereafter carried out on these isolates to detect mecA gene.
Staphylococcus species had its highest prevalence from infected wounds of patients (28.8%) while urine samples showed the least (5.4%). The highest level of resistance was to ceftazidime (S. aureus – 68%, CoNS – 75.6%) while the least resistance was observed for meropenem (S. aureus- 26%, CoNS- 46.3%). Using phenotypic method (with 1µg oxacillin antibiotic disc), the distribution of MRSA and MRCoNS was 44.0% and 46.3% respectively. PCR analysis showed that 38.0% of S. aureus and 41.5% of the CoNS had mecA gene respectively; wound swabs showed the highest prevalence with 30.5% of staphylococcal isolates being mecA gene positive. There was also no significant association between the Staphylococcal isolates and their isolation rate, isolation site and mecA gene distribution (p > 0.05).
This study draws attention on the increase in the prevalence of mecA gene (39.6%) and an increase in multidrug resistant staphylococci when compared to previous studies in our country; it recommends laboratory guidance and periodic review to stem the tide of resistance.
Staphylococcus aureus is a non-motile, aerobic or facultative anaerobic Gram positive coccus that inhabits the nasal membranes and skin of warm blooded animals and man, in whom it could cause a range of infections from mild, such as skin infections and food poisoning, to life threatening, such as pneumonia, sepsis, osteomyelitis and infectious endocarditis1. The CoNS are part of the normal flora of human skin2, these organisms have relatively low virulence but are increasingly recognized as agents of clinically significant infection of the bloodstream and other sites3. Risk factors for CoNS infection include foreign bodies (such as indwelling prosthetic devices or intravascular catheters) and immune compromise3.
Statistical analysis was by the Chi (X2) square test using INSTAT® software. A p value of < 0.05 was deemed statistically significant. A total of 91 clinical isolates of Staphylococcus species (S. aureus - 50 (54.9%), CoNS - 41 (45.1%)) were recovered from clinical samples during the period of study. Although the isolation rate of Staphylococcus species was higher from males (52.7%), gender was however not a risk factor for Staphylococcal infection (X2 = 0.2637, P > 0.05). There was no significant association in the occurrence of Staphylococci and the isolation sites (X2 = 0.5481, P> 0.05).
In this study, 28.8% of Staphylococci isolated were from wound swabs. In a study which had Staphylococcal isolates recovered from eight hospitals which cut across South-Western, North-central and North-Eastern Nigeria, more than 80% of the total number of S. aureus isolates recovered was from infected wounds13. It has been observed that the skin of 80–90% of people is colonized with S. epidermidis and that most CoNS infections are acquired from patients own flora26. The CoNS have also shown a higher frequency of isolation from wound swabs when compared to other samples18. In Nigeria, CoNS is one of the common causes of infections of open fractures in wounds and delay in wound debridement has been reported to be a major predisposing factor to wound infection28. Similarly, S. aureus is found on the skin, axilla, anterior nares and groins as normal flora27. It is therefore not hard to imagine that it would be implicated in wound infection as there is a breach in the structural integrity of the skin.
Summarily, this study notes a rising percentage in the distribution of mecA gene among the Staphylococci recovered from clinical samples in Benin when compared with previous studies in our country, it reports increasing level of multidrug resistant staphylococci with high MAR index, it reiterates the continued practice of indiscriminate use of antibiotics and emphasizes laboratory guidance before institution of anti-microbial therapy. Efforts should also be made to enact regulations on antibiotic usage. Periodic review of susceptibility pattern, molecular epidemiological surveys and surveillance is equally imperative. These when implemented promises to stem the tide of anti-mi crobial resistance.