Incidence, Molecular Characterization And Sensitivity To Buchholzia Coriacea Leaf Extract Of Methicillin Resistant Staphylococcus Aureus Nasal Isolates From Tertiary Institution Students In D

ABSTRACT

This study investigated the incidence, molecular characters and sensitivity to Buchholzia

coriacea leaf extract, of methicillin-resistant Staphylococcus aureus (MRSA) nasal isolates

from tertiary institution students in Delta State. Nasal swabs were collected with sterile swab

sticks from nine hundred (900) apparently healthy students in the study areas and cultured on

mannitol salt agar. The bacterial isolates (S. aureus) were Gram-stained, and the Gram positive

isolates subjected to catalase test. The catalase - positive isolates were subjected to coagulase

test and the coagulate positive isolates further subjected to DNase test for confirmation. The

MRSAs were detected using oxacillin antibiotic disk (1 μg). Antimicrobial susceptibility profile

of the MRSA isolates was determined according to the Clinical Laboratory Standard Institute

(CLSI) Guidelines. The Kirby-Bauer method was employed to determine the susceptibility of

the MRSA isolates to vancomycin. The minimum inhibitory concentrations (MICs) and

minimum bactericidal concentrations (MBCs) of some antibiotics and the extracts were

evaluated using agar dilution method. Tests were carried out to determine the presence of

penicillin binding protein2a (PBP2a). The MRSA isolates were screened to determine their

biofilm producing ability. Reverse Passive Latex Agglutination test was carried out to detect the

presence of enterotoxins among the MRSA isolates. The methanoic and aqueous leaf extracts of

Buchholzia coriacea leaf were prepared from standard protocols. Phytochemical constituents of

extract and antimicrobial screening against the MRSAs were carried out according to standard

methods. Molecular characterization of MRSA isolates was carried out to determine the

presence of the mecA genes among the isolates. Statistical analysis was done using analysis of

variance (ANOVA). Out of the nine hundred nasal samples collected from three different study

locations and screened, a total of 600 (66.7%) were positive for S. aureus, based on morphology

and biochemical tests. The incidence of S. aureus colonization among female and male

individuals was 313(34.7%) and 287 (31.9%), respectively. There was no significant difference

(p>0.05) in the females (52.2%) and males (47.8%). The antibiotic resistance pattern of the

MRSA isolates was: amoxicillin > streptomycin > amoxicillin/clavulanic acid > erythromycin

> chloramphenicol > co-trimoxazole > ofloxacin > ciprofloxacin > gentamicin. All the MRSA

isolates had the capacity to form biofilms and produce enterotoxins, especially enterotoxin B as

only one isolate produced enterotoxin C. The presence of Penicillin Binding Protein 2a was

detected in the isolates tested in this study. The leaf extracts of B. coriacea contain the

following: terpenes, alkaloids phenols, steroids, cardiac glycosides, anthraquinone and was

found to possess antibacterial activity. Of the twenty (20) isolates of MRSA subjected to

molecular characterization, only one had mecA gene. The results showed that there is presence

of methicillin resistant S. aureus (MRSA) among healthy tertiary school students in Delta State

of Nigeria, which are capable of producing biofilms associated with bacteria resistance. It was

also observed that most of the MRSA isolates are multi-drug resistant which signifies antibiotic

therapy failure in this area. It is also obvious from the results that there is the possibility of

MRSA to possess penicillin binding protein 2a without mecA gene.