Date Published: August 02, 2017
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Alicia D. Yeap, Kate Woods, David A. B. Dance, Bruno Pichon, Sayaphet Rattanavong, Viengmon Davong, Rattanaphone Phetsouvanh, Paul N. Newton, Nandini Shetty, Angela M. Kearns.
This is the first report of the molecular epidemiology of Staphylococcus aureus from skin and soft tissue infections (SSTI) in Laos. We selected a random sample of 96 S. aureus SSTI isolates received by the Microbiology Laboratory, Mahosot Hospital, Vientiane, between July 2012 and June 2014, including representation from seven referral hospitals. Isolates underwent susceptibility testing by Clinical and Laboratory Standards Institute methods, spa typing and DNA microarray analysis, with whole genome sequencing for rare lineages. Median patient age was 19.5 years (interquartile range 2–48.5 years); 52% (50) were female. Forty-three spa types, representing 17 lineages, were identified. Fifty-eight percent (56) of all isolates encoded Panton-Valentine leukocidin (PVL), representing six lineages: half of these patients had abscesses and three had positive blood cultures. The dominant lineage was CC121 (39; 41%); all but one isolate encoded PVL and 49% (19) were from children under five. Staphyococcus argenteus was identified in six (6%) patients; mostly adults > 50 years and with diabetes. Six isolates (6%) belonged to rare lineage ST2885; two possibly indicate cross-infection in a neonatal unit. One isolate from a previously undescribed lineage, ST1541, was identified. Antibiotic resistance was uncommon except for penicillin (93; 97%) and tetracycline (48; 50%). Seven (7%) isolates were methicillin-resistant S. aureus (MRSA), belonging to ST239-MRSA-III, CC59-MRSA-V(T) Taiwan Clone, ST2250-MRSA-IV, ST2885-MRSA-V and CC398-MRSA-V. Globally widespread CC5 and CC30 were absent. There are parallels in S. aureus molecular epidemiology between Laos and neighboring countries and these data highlight the prominence of PVL and suggest infiltration of MRSA clones of epidemic potential from surrounding countries.
Staphylococcus aureus is a leading cause of bacteremia in the Lao People’s Democratic Republic (Lao PDR; Laos), particularly in infants.1 The presence of skin infection and the local practice of warming mothers with their newborns on a “hot bed” (a bed under which hot coals are placed) for the first few weeks postpartum have been associated with S. aureus bacteremia in neonates.2
This is the first comprehensive report of the molecular epidemiology of S. aureus SSTIs from Laos. Of note are the prominence of PVL-positive CC121 and other PVL-producing strains, the relatively low prevalence of MRSA, the presence of S. argenteus and the identification of two novel lineages. The globally widespread clones CC30 and CC5 were notably absent from this series despite their frequent presence in human carriage in Cambodia and worldwide.9