THE INTERNATIONAL ARABIC JOURNAL OF ANTIMICROBIAL AGENTS

Background: Staphylococcus aureus is a major cause of nosocomial and community-acquired infections. Despite the predominance of two capsular polysaccharides, types 5 and 8, on the surface of clinical isolates, molecular and epidemiological variations have been reported among various geographical areas in addition to various clinical outcomes of S. aureus increasing the challenge for preventive and control measurements against staphylococcal infections and diseases. Materials and Methods: A total of 315 S. aureus isolates of various clinical conditions comprised both hospital and community-acquired infections between 2009 and 2011 in Amman and Gaza were studied. All S. aureus clinical isolates included in the present study have been investigated by PCR method to determine the distribution and diversity of capsule polysaccharide expression. Results: Most of the clinical isolates (90%) expressedeither capsular polysaccharide genotypes CP5 (37%) andCP8 (53%), whereas 10% were nontypeable by PCR. Significant predominance of CP8 genotype was reported in clinical isolates of S. aureus from infections in comparison to those which are commonly colonising various normal body sites. THE INTERNATIONAL ARABIC JOURNAL OF ANTIMICROBIAL AGENTS 2014 Vol. 4 No. 2:4 doi: 10.3823/750 This article is available from: www.iajaa. org 2 Received 18 July 2014; accepted 22 August 2014 Introduction Staphylococcus aureus continues to be a major pathogen causing a wide spectrum of infections with high morbidity and mortality (1). Moreover, increased concern on this pathogen emerged from its resistance against virtually all antimicrobial agents available in hospitals and communities (2). The adaptation of S. aureus to the environment has been marked by the acquisition of methicillin-resistant S. aureus (MRSA) and the emergence of multidrug resistance, making the new strategies to manage staphylococcal infections of major importance in clinical practice.Our understanding of virulence and epidemiological behaviour of this species has been greatly enhanced by sequencing of the genomes of several S. aureus strains. For example, the identification of new non-protein coding RNA genes and the presence of mutations within several metabolic genes have been shown to be involved in phenotypic switching and antibiotic resistance of S. aureus(3,4) . S. aureus is equipped with various virulence factors, including surface-associated adhesins, cytotoxins, superantigens, exoenzymes, and capsularpolysaccharides, which contribute to the pathogenesis of staphylococcal infections (5). The capsular polysaccharide is a cell wall bacterial component that protects bacterium from phagocytosis and enhances microbial virulence (6). Approximately 90% of S. aureus isolates produce one of 11 capsular polysaccharides nevertheless, only two types,type 5 and type 8, are clinically relevant since they are predominant among clinical infection isolates of various geographic origins (7-9). The importance and relevance of these capsule types and their role in septic shock were confirmed by the development of a conjugate vaccine, StaphVAX study (10). In addition, the formation of biofilms in S. aureus is enhanced by augmenting adhesiveness due to both intercellular polysaccharide adhesion and capsular polysaccharides (11). The emergence of resistance to antibiotics through the formation of permeability barrier to antimicrobial agents has been reported in S. aureus and other bacteria(12,13). For example, it has been shown that vancomycin-intermediate resistant S. aureus (VISA) strains produce a distinctly thickened cell wall (14). Few studies were carried out to investigate the potential role of S.aureus polysaccharide capsule as a permeability barrier to several antimicrobial agents(15-16). Generally, although the production of thick capsules in certain serotypes of S.aureus showed a permeability barrier potential to common biocides and affected the susceptibility of S.aureus to some antibiotics, the results are still controversial. Due to the lack of epidemiological and clinical Conclusion: Correlation between capsule genotypes and pathogenic behaviour of S. aureus could be established. Further studies on the molecular levels are required to determine the role and mechanisms of capsular expression in the variability of pathogenic potential of S. aureus.