Original article / research
Demonstration of Virulence Factors in Streptococcus Pneumoniae Isolates from a Tertiary Hospital in South India
Dr. Jayashree Veerasamy,
Assistant Professor, Department of Microbiology,
Shri Sathya Sai Medical College and Research Institute, Ammapettai, Kanchipuram District,
Kanchipuram-603108, Tamil Nadu, India.
Introduction: Streptococcus pneumoniae (pneumococci) colonizes the nasopharynx and 94 different serotypes have been characterized on the basis of the capsular polysaccharides. Nasopharyngeal colonization is documented to be present in children more than that is seen in adults. Pneumococci cause wide range of infections with marked morbidity among children, elderly and immuno-compromised patients. The pathogenesis may be attributed to the virulence factors such as pneumolysin and autolysin.
Aim: The aim of this study was to demonstrate virulence genes, pneumolysin (ply) and autolysin (lytA) in pneumococci isolated from clinical samples and nasopharyngeal carriers by Polymerase Chain Reaction (PCR).
Materials and Methods: Total 15,473 clinical samples of sputum, broncho-alveolar lavage, tracheal aspirate, cerebro-spinal fluid, blood, ascitic fluid, throat swab, eye discharge, ear swab and pleural fluid from infected patients, including nasopharyngeal carriers screened for pneumococci in 600 healthy school children were included in the study. Blood and CSF isolates were categorized as invasive and those isolates obtained from other clinical sites as non-invasive, respectively. Standard methods for characterisation of Streptococcus pneumoniae such as Gram stain, Optochin sensitivity, bile solubility, and inulin fermentation was done, with confirmation by automated Vitek 2. Streptococcus pneumoniae isolated from positive samples were subjected to molecular detection of virulence genes lytA and ply coding for autolysin and pneumolysin respectively.
Results: In all 121 Streptococcus pneumoniae positive isolates were isolated from clinical specimens including carriers with isolation rate of 0.81%. Seventy four pneumococci isolates were randomly selected which were representative of invasive, non-invasive and carrier isolates. They were screened by PCR for lytA and ply genes using appropriate primers. All isolates tested were positive for autolysin (lytA) and 97.2% including the 15 invasive isolates were positive for pneumolysin (ply).
Conclusion: This study concludes that detection of virulence genes for pneumococci in clinical samples confirms the patho-physiologic consequences of pneumococcal infections.
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