Characterisation of PVL-positive Staphylococcus aureus isolates from Saxony and Brandenburg

Introduction: Panton-Valentine leukocidin (PVL) is a staphylococcal toxin associated with chronic/recurrent skin and soft tissue infections (SSTI) and necrotizing pneumonia. Thus, its detection warrants aggressive therapy and infection control measures. However, PVL detection is often a molecular method limiting its use.

Material and methods: In order to aid development of a lateral flow test for PVL, clinical isolates from SSTI were collected in 2020/21 at two laboratories in Dresden and at one in Frankfurt/Oder. After exclusion of duplicate and serial isolates, 83 isolates were eligible. These were characterized using DNA-microarrays that facilitated the detection of virulence and resistance markers as well as the assignment to clonal complexes and to epidemic/pandemic strains. They were also tested using an experimental lateral flow (LF) test for PVL.

Results: 39 isolates (47%) were PVL positive, and 30 isolates (36%) were mecA-positive. The MRSA rate among PVL-negatives was 20% (9 isolates), but among PVL-positives, it was as high as 54% (n=21). The most common PVL-positive MSSA lineages were CC152 (n=6), CC121 (n=4), CC5 and CC30 (each n=2). The most common PVL-MRSA strains were CC398-MRSA-VT (n=5), CC5-MRSA-IV "Sri Lanka Clone" (n=4), CC8-MRSA-[mec IV+Hg] "Latin American USA300" (n=4) and CC22-MRSA-IV (PVL+/tst+) (n=2). Other PVL-MRSA were CC1-MRSA-[V+fus+ccrAB1], CC8-MRSA-[IV+ACME] "USA300", CC30-MRSA-IV "WSPP Clone", CC88-MRSA-IV, CC152-MRSA-IV and -V, with one isolate each. LF results were in 81 cases concordant to genotyping, one false-positive and one false-negative were observed.

Discussion: Both the PVL rate as well as the MRSA rate among PVL-positives were higher than in a previous study a decade before. All PVL-MRSA strains detected as well as the most common methicillin-susceptible lineage (CC152) are known to locally predominate in other parts of the world, and thus all might be regarded as travel-associated. Therefore, patients with suspected PVL-associated disease should be asked for their travel histories, and, in case of hospitalization, they should be treated as MRSA cases until proven otherwise.