Plasmid Profile, Methicillin Resistance Determinants And Characterisation Of Staphylococcus Species Isolated From Clinical And Community Environments

ABSTRACT

Methicillin-resistant staphylococcus (MRS) infections are of global concern in healthcare

institutions and community settings with significant morbidity and mortality due to multidrug

resistance challenges. In Nigeria, most methicillin resistance detection was based on

phenotypic method with scanty reports on molecular characterisation of MRS. In this

study, molecular techniques were used to determine the presence of methicillin resistant

gene (mecA) with its associated resistance determinants (vanA and blaZ) and plasmid

profile of staphylococci isolated from clinical and community samples.

Staphylococcus species from clinical (55) and community (53) samples were isolated from

air, selected waste water drainages and human swabs (eye, semen, ear, high vagina swab,

throat, urethra, wound, nostril, skin) in the University of Ibadan and University College

Hospital. They were identified using standard microbiological procedures. The isolates

identity was confirmed to genus level using 16S-rRNA specific primers and identified to

species level by PCR-Restriction Fragment length Polymorphism supplemented with PCR

species-specific-primers. The isolates were phenotypically screened for resistance to

methicillin and other antibiotics by agar diffusion method. Multiplex PCR was used to

assess presence of mecA and the resistant determinants while Simplex PCR was used to

determine the origin of mecA isolates by detecting the presence of Panton-Valentine

Leukocidin (PVL). Plasmid profiles of clinical (35) and community (19) isolates with

multiple drug resistance were determined using standard procedures. Data was analysed

by descriptive statistics.

The organisms were identified as S. epidermidis (92.6 %), S. aureus (6.5 %) and S.

xylosus (0.9 %). Phenotypic resistance to methicillin was 72.7 and 62.3 % in clinical and

community isolates respectively. In the clinical isolates of S. epidermidis, 30.9, 32.7, 34.5,

iv

40.0, 41.8, 60.0, 76.4, and 89.1 % were resistant to Chloramphenicol, Vamcomycin,

Streptomycin, Erythromycin, Gentamycin, Tetracycline, Cotrimoxazole and Cloxacillin

respectively. Correspondingly, in community isolates of S. epidermidis, 28.3, 3.8, 32.1,

50.9, 26.4, 58.5, 90.6 and 92.5 % were resistant to these antibiotics. In the clinical isolates

of S. aureus, 3.6, 5.5, 5.5, 7.3, 7.3, 7.3, 9.1 and 9.1 % were resistant to Vamcomycin,

Erythromycin, Chloramphenicol, Streptomycin, Gentamycin, Tetracycline, Cotrimoxazole

and Cloxacillin respectively. In community isolates, 1.9 % S. aureus were resistant to

Cotrimoxazole, Chloramphenicol, Erythromycin, Gentamycin and Streptomycin while 3.8

% were resistant to Cloxacillin. Among clinical isolates of S. xylosus, 1.8 % was resistant

to all the antibiotics except Chloramphenicol and Streptomycin. All the strains lacked

vanA gene, while only clinical isolates (3.6 %) had mecA when its specific primers were

used and 5.5 % using its regulatory element specific primers in PCR. The blaZ gene was

found in 16.4 % of clinical and 1.8 % of community isolates. There was no PVL in the

isolates with mecA. Plasmid size of 23.13kb was found in 94.3 % of clinical and 84.2 % of

community isolates.

The detection of blaZ gene in community isolates showed that such resistance

determinants predominantly found in clinical isolates are also emerging in the community

isolates. Hence, setting up antibiotic surveillance system is necessary to minimize this

trend