Population structure analyses of Staphylococcus aureus at Tygerberg Hospital, South Africa, reveals a diverse population, a high prevalence of Panton–Valentine leukocidin genes, and unique local methicillin-resistant S. aureus clones

Abstract

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.

New epidemiology of Staphylococcus aureus infection in Africa

“…This is in stark contrast to Europe, where the prevalence of PVL‐positive isolates is low (0.9–1.4%) . Studies from Gabon and South Africa further support the association of PVL with abscesses and skin and soft tissue infection . The reasons for the high prevalence of PVL are unknown, but might be related to the host (i.e.…”

“…Distribution of methicillin‐resistant S taphylococcus aureus ( MRSA ) clones in Africa. The three major MRSA multilocus sequence types ( ST s) of each study were identified . Of these, the five most widely distributed clones in A frica are shown.…”

Molecular Characterization of Staphylococcus aureus Isolated from Bovine Mastitis and Close Human Contacts in South African Dairy Herds: Genetic Diversity and Inter-Species Host Transmission

“…The majority of the bovine isolates collected from this site were ST352; no other S. aureus ST8 isolates were detected. Staphylococcus aureus ST8 has been reported extensively from human carriage and clinical specimens (Sakwinska et al, 2009; Oosthuysen et al, 2014). This lineage also comprises a number of significant MRSA clones (Monecke et al, 2011).…”

Typification Methods and Molecular Epidemiology of Staphylococcus aureus with Methicillin Resistance

“…Interestingly, SCCmec type IV was found in twice as many MRSA clones as other SCCmec types, suggesting that most clones arise by acquisition of SCCmec type IV by S. aureus [90]. This is probably a result of the smaller size of SCCmec type IV compared with other SCCmec types, which may facilitate transfer of the cassette among staphylococcal species [98]. Furthermore, it has been shown that MRSA strains that belong to the major CCs (1,5,8,22,30,45) are easier to transform with mecA-expressing plasmids tan are strains belonging to minor CCs.…”

“…This spread from Europe to the USA [54]. In Africa the presence of the following clones: sequence type (ST) 5-MRSA-I, ST239-MRSA-III, ST612-MRSA-IV, ST36-MRSA-II and ST22-MRSA-IV have been reported [97,98]. ST239 is also common in mainland Asia, South America and parts of Eastern Europe [54].…”