Phenotypic and molecular characteristics of methicillin-resistant Staphylococcus aureus isolates from Ekiti State, Nigeria

Figures & data

Table 1 Staphylococcus aureus isolates from clinical specimens in Ekiti State, Nigeria

Clinical specimens	Number of isolates	mecA genepositive (%) (MRSA)	mecA genenegative (%) (MSSA)
Blood culture	23	0 (0)	23 (100)
Urine	53	8 (15.1)	45 (84.9)
Sputum	18	0 (0)	18 (100)
Anterior nares	20	0 (0)	20 (100)
Pleural fluid	5	0 (0)	5 (100)
Endocervical swab	11	0 (0)	11 (100)
High vaginal swab	10	4 (40)	6 (60)
Semen	8	0 (0)	8 (100)
Wound swab	46	24 (52.2)	22 (47.8)
Ear swab	14	4 (28.6)	10 (71.4)
Total	208	40 (19.2)	168 (80.8)

Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; Mssa, methicillin-sensitive Staphylococcus aureus.

Table 2 Antibiotic susceptibility of Staphylococcus aureus isolates from clinical specimens in Ekiti State, Nigeria

Antibiotic	Susceptible number (%)	Intermediate number (%)	Resistant number (%)
Penicillin G	36 (17.3)	–	172 (82.7)
Cefoxitin	112 (53.8)	–	96 (46.2)
Methicillin	140 (67.3)	–	68 (32.7)
Oxacillin	124 (59.6)	–	84 (40.3)
Erythromycin	100 (48.1)	64 (30.7)	44 (21.2)
Gentamicin	176 (84.6)	8 (3.8)	24 (11.5)
Pefloxacin	124 (59.6)	48 (23.1)	36 (17.3)
Sparfloxacin	152 (73.1)	16 (7.7)	40 (19.2)
Tetracycline	64 (30.8)	8 (3.8)	136 (65.4)
Vancomycin	208 (100)	–	0 (0)

Table 3 Comparison of cefoxitin disk diffusion test and mecA gene detection

	ZD ≤ 21 mm (R)	ZD ≥ 22 mm (S)	Total
Cefoxitin ZD (mm)
+	40	0	40
mecA gene
−	36	132	168
Total	76	132	208

Notes: Sensitivity = 100%; specificity = 78.6%; PPV = 52.6%; NPV = 100%.

Abbreviations: ZD, zone diameter; R, resistant; S, sensitive; PPV, positive predictive value; NPV, negative predictive value.

Table 4 Comparison of oxacillin disk diffusion test and mecA gene detection

	ZD ≤ 10 mm (R)	ZD ≥ 13 mm (S)	Total
Oxacillin ZD (mm)
+	32	8	40
mecA gene
−	52	116	168
Total	84	124	208

Notes: Sensitivity = 80%; specificity = 69.1%; PPV = 38.1%; NPV = 93.5%.

Abbreviations: ZD, zone diameter; R, resistant; S, sensitive; PPV, positive predictive value; NPV, negative predictive value.

Table 5 Comparison of methicillin disk diffusion test and mecA gene detection

	ZD ≤ 9 mm (R)	ZD ≥ 14 mm (S)	Total
Methicillin ZD (mm)
+	28	12	40
mecA gene
−	40	128	168
Total	76	132	208

Notes: Sensitivity = 70%; specificity = 76.2%; PPV = 36.8%; NPV = 96.9%.

Abbreviations: ZD, zone diameter; R, resistant; S, sensitive; PPV, positive predictive value; NPV, negative predictive value.

Figure 1 Agarose gel electrophoresis of PCR products of representative isolates.

Notes: The mecA gene is indicated by the amplification of 533 base pair products. Lanes 6 and 9 are positive for mecA, as indicated by the 533 base pair PCR product. Lanes 1–5, 7, 8, 10–21, 24, and 25 were negative for mecA. Lane 22 was the MRSA-positive control (NCTC 119040), lane 23 was the negative control (water), and lane M was the molecular weight size marker.

Abbreviations: PCR, polymerase chain reaction; MRSA, methicillin-resistant Staphylococcus aureus; NCTC, National Center for Type Cultures; M, molecular weight.