Unusually high prevalence of panton-valentine leukocidin genes among methicillin-sensitive Staphylococcus aureus strains carried in the Indonesian population

Abstract

Few data on the molecular characteristics and epidemiology of Staphylococcus aureus from Indonesia are available. The purpose of the present study was to define S. aureus reservoirs in both the Indonesian community and hospital using a collection of 329 nasal carriage isolates obtained during a survey of 3,995 healthy individuals and patients from Java, Indonesia. Only one strain (0.3%) was identified as methicillin-resistant S. aureus by mecA gene PCR. The Panton-Valentine leukocidin (PVL) genes were detected in 35 methicillin-sensitive S. aureus strains (10.6%). Molecular typing by pulsed-field gel electrophoresis of the 329 isolates showed extensive genetic diversity among both PVL-positive and PVL-negative strains. In Surabaya, Indonesia, however, a cluster was identified that was strongly associated with the presence of the PVL locus (P < 0.0001). As determined by high-throughput amplified fragment length polymorphism, PVL-positive strains occurred throughout all major AFLP clusters (I to IV). Multilocus sequence typing of a subset of isolates showed that most PVL-positive strains belonged to sequence type (ST) 188, while most PVL-negative isolates belonged to ST45. The high prevalence of PVL-positive S. aureus strains in certain regions of Indonesia is of concern since these strains may cause severe infections in the community and in hospitals.

FIG. 1.

Dendrogram based on PFGE SmaI restriction pattern analysis of 329 nares-colonizing S. aureus isolates. Similarity analysis was performed with the Dice coefficient and clustering by the UPGMA method. The scale on the top shows percentages of similarity. Further information about the strains is shown on the right side of the figure in two columns. In the first column (CITY), isolates from Surabaya are indicated by a dash, whereas isolates from Semarang are left blank. In the second column (PVL), only PVL-positive strains are marked by a dash. The single MRSA isolate is indicated by an arrow. Clusters are designated A to C, and subclusters within cluster B are designated B1 to B6. The rectangle highlights the 14 PVL-positive strains in subcluster B3.

FIG. 2.

Two-dimensional clustering of 81 carriage strains from Indonesia and 829 carriage strains from The Netherlands (20). The dendrogram on the y axis represents the phylogenetic clustering of the 910 strains. The dendrogram on the x axis shows the clustering of the AFLP markers. AFLP marker fragments are shown in red and green; red represents marker presence and green indicates absence. The blue horizontal bars at the right side of the figure indicate the position of the Indonesian isolates; the small red bars represent PVL-positive strains from both Indonesia and The Netherlands. The black-and-white bar at the far right of the figure represents the three main clusters (I, II, and III) and two minor clusters (IVa and IVb), as defined before (20).