Highly Epidemic Strains of Methicillin-Resistant Staphylococcus aureus Not Distinguished by Capsule Formation, Protein A Content or Adherence to HEp-2 Cells

Abstract

During the 1990s, two strains of epidemic methicillin-resistant Staphylococcus aureus, designated 'phage types EMRSA-15 and EMRSA-16, have emerged as significant hospital pathogens. They have resisted standard methods of control and spread widely amongst in the UK, often becoming endemic, while the incidence of other epidemic types of MRSA has either declined or not changed. This suggests that EMRSA-15 and EMRSA-16 possess special properties that favour their dissemination and survival. In order to investigate this hypothesis, a study was undertaken that examined methicillin-sensitive and methicillinresistant strains of Staphylococcus aureus, including EMRSA types 1, 2, 3, 15 and 16, for capsule formation, the amount of bound protein A produced, and quantitative adherence to the human continuous epithelial cell line HEp-2. Although all these properties varied amongst the strains examined, there was no relationship between any of them and methicillin resistance or epidemic type, and, incidentally, no relationship between cell-wall bound protein A content and adherence.

Selective lethal photosensitization of methicillin-resistant Staphylococcus aureus using an IgG-tin (IV) chlorin e6 conjugate

“…Indeed, different strains of S. aureus, whether methicillin resistant or methicillin sensitive, can vary in the amount of protein A expressed and localized to the cell surface 31 and there is some evidence to suggest that EMRSA-16 has more surface-bound protein A than EMRSA-15, EMRSA-3 and EMRSA-1. 32 This would help to explain why free SnCe6 reduced the viable counts of EMRSA-16 and EMRSA-15 by 99.1%, whereas with IgG-SnCe6, EMRSA-16 was much more susceptible to killing than EMRSA-15, with 98.7% and 57.8% kills, respectively. If EMRSA-16 produces larger amounts of cell wall bound protein A than EMRSA-15, it would be expected that a greater amount of the conjugate would bind to EMRSA-16 than EMRSA-15.…”

Lack of correlation between X region spa polymorphism and virulence of methicillin resistant and methicillin sensitive Staphylococcus aureus strains.

“…However, after thorough verification of the results, it was revealed that patients from the first group had higher risk factors and after this correction the adjusted mortality was 7.1 % and 6.2 %, respectively (Melzer et al, 2003). In the analysis of the amount of protein A produced, ability to form capsules and the extent of adherence to the human epithelial cell line Hep-2, no differences were found between MRSA and MSSA (Aathithan et al, 2001). Protein A is thought to be a significant virulence factor as it shields bacteria from the immunological response of the host organism at the first stages of infection.…”

A major methicillin-resistant Staphylococcus aureus clone predominates in Malaysian hospitals

“…The predominance of type A and its subtypes in all the hospitals could be due to increased nosocomial transmission within and between the hospitals and/or may be attributable to a virulencerelated property of the particular strain that has yet to be determined. Aathithan et al [7] found no relationship between methicillin resistance or epidemic type with cell-wall bound protein A content and adherence in highly epidemic strains of MRSA in the UK. Moreover, Enright et al [8] observed that the most prevalent methicillin-sensitive S. aureus (MSSA) clone was very closely related to EMRSA-16, a widespread epidemic strain in the UK.…”