Eighty-two percent of 320 clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates from various infection sites collected throughout South Africa were separated into five major globally prevalent clusters by SmaI pulsed-field gel electrophoresis, spa, and SCCmec typing. Only one Panton-Valentine leukocidin-positive isolate was detected. This is the first detailed MRSA epidemiology study for the whole country.

Studies reporting on the population structure of Staphylococcus aureus in South Africa have focused only on methicillin-resistant S. aureus (MRSA). This study describes the population structure of S. aureus, including methicillin-susceptible S. aureus (MSSA) isolated from patients at Tygerberg Academic Hospital, Western Cape province. Pulsed-field gel electrophoresis (PFGE), detection of Panton-Valentine leukocidin (PVL), spa typing, multilocus sequence typing (MLST), agr typing and SCCmec typing were used to characterize strains. Of 367 non-repetitive S. aureus isolates collected over a period of 1 year, 56 (15.3%) were MRSA. Skin and soft tissue infections were the most frequent source (54.8%), followed by bone and joint (15.3%) and respiratory tract infections (7.7%). For strain typing, PFGE was the most discriminative method, and resulted in 31 pulsotypes (n = 345, 94.0%), as compared with 16 spa clonal complexes (CCs) (n = 344, 93.4%). Four MLST CCs were identified after eBURST of sequence types (STs) of selected isolates. One hundred and sixty isolates (MSSA, n = 155, 42.2%) were PVL-positive, and agr types I-IV and SCCmec types I-V were identified. Our S. aureus population consisted of genotypically diverse strains, with PVL being a common characteristic of MSSA. MSSA and MRSA isolates clustered in different clones. However, the dominant MRSA clone (ST612) also contained an MSSA isolate, and had a unique genotype. Common global epidemic MRSA clones, such as ST239-MRSA-III and ST36-MRSA-II, were identified. A local clone, ST612-MRSA-IV, was found to be the dominant MRSA clone.

Microbial pathogens have developed several mechanisms to modulate and interfere with host cell cycle progression. In this study, we analysed the effect of the human pathogen Neisseria meningitidis on cell cycle in a brain endothelial cell line as well as in primary brain endothelial cells. We found that N.  Meningitidis causes an accumulation of cells in the S phase early at 3 and at 24 h post-infection that was paralleled by a decrease of cells in G2/M phase. Importantly, the outer membrane proteins of the colony opacity-associated (Opa) protein family as well as the Opc protein proved to trigger the accumulation of cells in the S phase. A focused cell cycle reverse transcription quantitative polymerase chain reaction-based array and integrated network analysis revealed changes in the abundance of several cell cycle regulatory mRNAs, including the cell cycle inhibitors p21(WAF1/CIP1) and cyclin G2. These alterations were reflected in changes in protein expression levels and/or relocalization in N. meningitidis-infected cells. Moreover, an increase in p21(WAF1/CIP1) expression was found to be p53 independent. Genetic ablation of p21(WAF1/CIP1) and cyclin G2 abrogated N. meningitidis-induced S phase accumulation. Finally, by measuring the levels of the biomarker 8-hydroxydeoxyguanosine and phosphorylation of the histone variant H2AX, we provide evidence that N. meningitidis induces oxidative DNA damage in infected cells.

Microbial pathogens have developed several mechanisms to modulate and interfere with host cell cycle progression. In this study, we analyzed the effect of the human pathogen Neisseria meningitidis on the cell cycle of epithelial cells. Two pathogenic isolates, as well as two carrier isolates, were tested for their ability to adhere to and invade into the epithelial cell lines Detroit 562 and NP69 and to modulate the cell cycle. We found that all isolates adhered equally well to both Detroit 562 and NP69 cells, whereas the carrier isolates were significantly less invasive. Using propidium iodide staining and 5-ethynyl-2=-deoxyuridine pulse-labeling, we provide evidence that meningococcal infection arrested cells in the G 1 phase of the cell cycle at 24 h postinfection. In parallel, a significant decrease of cells in the S phase was observed. Interestingly, G 1 -phase arrest was only induced after infection with live bacteria but not with heat-killed bacteria. By Western blotting we demonstrate that bacterial infection resulted in a decreased protein level of the cell cycle regulator cyclin D1, whereas cyclin E expression levels were increased. Furthermore, N. meningitidis infection induced an accumulation of the cyclin-dependent kinase inhibitor (CKI) p21 WAF1/CIP1 that was accompanied by a redistribution of this CKI to the cell nucleus, as shown by immunofluorescence analysis. Moreover, the p27 CIP1 CKI was redistributed and showed punctate foci in infected cells. In summary, we present data that N. meningitidis can interfere with the processes of host cell cycle regulation.

South Afr J Epidemiol Infect Original Research: Characterisation of Staphylococcus aureus bacteraemia at Tygerberg hospitalTo elucidate the local epidemiology of Staphylococcus aureus bacteraemia, we characterised blood culture isolates using molecular methods and prospectively collected clinical data to determine the occurrence of community-acquired, methicillinresistant S. aureus (MRSA). Consecutive S. aureus blood culture isolates were collected over a one-year period from patients who were admitted to Tygerberg Academic Hospital in the Western Cape. A multiplex polymerase chain reaction (PCR) was used for the detection of spa, mecA and lukS/F-PV genes. Strain typing was performed using spa typing. Multiplex PCR for staphylococcal cassette chromosome mec (SCCmec) typing was also performed, as well as multilocus sequence typing (MLST) on selected isolates. Cases were categorised by clinical data as either hospital-acquired, healthcare-associated or community-acquired. One hundred and thirteen S. aureus isolates (30% MRSA) were collected from 104 cases of bacteraemia. According to clinical data, all community-acquired infections, 54% of hospital-acquired cases and the majority of healthcare-associated cases were due to methicillin-sensitive S. aureus (MSSA). Furthermore, all Panton-Valentine leukocidin (PVL)-positive isolates (15.9% of all S. aureus) were MSSA. MRSA strains were isolated from hospital-acquired cases (with a minority of healthcare-associated cases) and clustered mainly in spa-CC701 and CC012. SCCmec type IV was predominant. MLST clones included ST239-MRSA-III, ST36-MRSA-II and ST612-MRSA-IV. The predominant source for S. aureus bacteraemia was catheter-related infection (39%). Community-acquired S. aureus infections in our setting remain sensitive to methicillin and current treatment guidelines suffice. The majority of hospital-acquired and healthcare-associated infections were catheter-related. Prevention and treatment should be targeted accordingly.Peer reviewed.

Data concerning the virulence and pathogenesis of South African strains of Staphylococcus aureus are limited. We investigated host–pathogen interactions of randomly selected clinical S. aureus isolates representing various clones. We characterized the ability of isolates to adhere to fibronectin, fibrinogen, collagens IV and VI, to invade host cells and to induce cell death in vitro. We analysed the possible association of these results with characteristics such as methicillin resistance, Panton–Valentine leucocidin (PVL) positivity and clonality. The S. aureus isolates displayed diversity in their abilities to adhere to various human ligands. All isolates were highly invasive except for ST121. PVL-negative isolates were significantly more invasive than the PVL-positive isolates (p 0.004). Isolates of CC5, CC30 and CC121 were non-cytotoxic, whereas isolates of CC22, CC8, CC15, CC45 and CC88 were very cytotoxic. No statistical association was identified between cell death and methicillin resistance, bacterial PVL status, clonality or patient HIV status. The vast majority of isolates were invasive and induced significant cell death. PVL-negative isolates were more invasive than PVL-positive isolates, while methicillin-resistant isolates were not found to be more invasive or cytotoxic than methicillin-susceptible isolates.

USA100 strains are significant contributors to the overall burden of health care-associated methicillin-resistant Staphylococcus aureus (MRSA) infections. Strain 209 is a representative MRSA isolate that serves as a model organism for agr type II studies and USA100 virulence assessments. We present a draft genome sequence of this strain.

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