Absolute dependence on mecA gene as the defining standard in determining the resistance of S. aureus to methicillin became the subject of distrust by many researchers. The present study aimed to determine the frequency of mecA gene in methicillin resistant S. aureus (MRSA) isolates using polymerase chain reaction and to correlate its presence to conventional method. In this regard, two hundred S. aureus isolates were collected from patients with different diseases attending different hospitals in Shandi City, Sudan. Phenotypic Kirby-Bauer method confirmed the existence of methicillin resistant S. aureus in 61.5% of the subjected isolates with MICs ranging from 4 μg/mL to 256 μg/mL when using E-test. However, when amplifying a 310 bp fragment of the mecA gene by PCR, twelve out of the 123 MRSA isolates (9.8%) were mecA negative, whereas all the 77 methicillin sensitive S. aureus (MSSA) were mecA negative. In conclusion, this study drew attention to the credibility of the mecA gene and its usefulness in the detection of all MRSA strains without referring to the traditional methods. Hence, it is highly recommended to consider alternative mechanisms for β-lactam resistance that may compete with mecA gene in the emergence of MRSA phenomenon in the community.

The objective of the study was to determine the frequency of nocardiosis in HIV-positive and HIV-negative individuals clinically suspected of having tuberculosis (TB). The study population (n = 171) were those who attended chest hospitals in Khartoum State, Sudan, between January and March 2010. The patients suffered from pulmonary infections with positive acid-fast bacilli. Blood (n = 171) and sputum (n = 171) samples were collected simultaneously. Blood samples were tested serologically for the presence of antibodies using HIV/Intensified Combination Prevention (ICP) test and sputum were cultured onto Lowenstein Jensen slants according to standard methods. Isolates showing rapid growth characteristic of Nocardiae were subcultured and subsequently identified using glucose yeast extract agar medium. All candidates in the study population (n = 171) suffered from pulmonary infections, nocardiosis was diagnosed in 4% (n = 7), HIV-positive cases were 17 (9.9%). Five Nocardia species were isolated from HIV-negative patients whereas two were from HIV-positive patients. Nocardia spp. cause pulmonary infections (4.09%) in both immunocompetent (2.92%) as well as immunocompromised (1.17%) patients who attend chest clinics in Sudan.

It is concluded that whilst TST and IS6110 achieved 100% sensitivity based on the reference standard of culture, the latter was more specific. The TST is recommended for routine diagnosis and the use of PCR for particular cases, depending on the facilities and the urgency.