Virulence Characters of some Methicillin Resistant Staphylococcus aureus Isolates

Background: The multidrug resistance of Methicillin Resistant Staphylococcus aureus (MRSA) has become increasingly a major problem and responsible for most of the hospital acquired infections seen in local hospitals in Egypt. This emphasizes the importance of rapid detection of MRSA and investigating their virulence determinants that may be used as a target for certain anti-infectious agents that could help in the control measures in our hospitals. The aim of this study was to investigate some virulence determinants in MRSA isolates.

Materials and findings: A total number of 164 bacterial isolates were recovered from different clinical specimens obtained from Ain Shams University Hospital patients (El Demerdash). Of these, 99 isolates (60.4 %) were recovered from pus, 35 isolates (21.3 %) from sputum, 18 (11 %) isolates from nasal swabs, 11 (6.7 %) isolates from blood and one isolate (0.6 %) was recovered from prostatic exudates. A total of 59 isolates were identified as S. aureus using microscopical examination, culture characteristics and biochemical reactions. Screening for methicillin resistance was done by agar disc diffusion method using cefoxitin discs. Out of the 59 S. aureus isolates, 48 ones were MRSA. Thereafter, all MRSA isolates were investigated for protease, lipase, hemolysin as well as biofilm formation. Results showed that all MRSA isolates possess protease activities while most of them did not show hemolysin or lipase activities. On the other hand, all MRSA isolates showed capability to form biofilm. The statistical analysis showed  that there was a significant increase in  mean biofilm formation among highly resistant isolates compared to those of moderate and low resistant ones (P<0.01).

Conclusion: The presence of some virulence factors in MRSA could increase their potential threats especially that most of them have multidrug resistance, rendering it difficult to treat. Further studies have to be conducted in the future targeting these virulence determinants as an additional approach that might aid in the prevention and control of such resistant organism seen in our hospitals.

Author(s): Mona Hesham El gayar, Mohammad Mabrouk Aboulwafa, Khaled Mohammad Aboshanab, Nadia Abdel haleem Hassouna

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