Emergence and spread of a mupirocin-resistant variant of the European epidemic fusidic acid-resistant impetigo clone of Staphylococcus aureus, Belgium, 2013 to 2023.

BackgroundAntimicrobial resistance to mupirocin and fusidic acid, which are used for treatment of skin infections caused by Staphylococcus aureus, is of concern.AimTo investigate resistance to fusidic acid and mupirocin in meticillin-susceptible S. aureus (MSSA) from community-acquired skin and soft tissue infections (SSTIs) in Belgium.MethodsWe collected 2013-2023 data on fusidic acid and mupirocin resistance in SSTI-associated MSSA from two large Belgian laboratories. Resistant MSSA isolates sent to the Belgian Staphylococci Reference Centre were spa-typed and analysed for the presence of the eta and etb virulence genes and the mupA resistance gene. In addition, we whole genome sequenced MSSA isolates collected between October 2021 and September 2023.ResultsMupirocin resistance increased between 2013 and 2023 from 0.5-1.5% to 1.7-5.6%. Between 2018 and 2023, 91.4% (64/70) of mupirocin-resistant isolates were co-resistant to fusidic acid. By September 2023, between 8.9% (15/168) and 10.1% (11/109) of children isolates from the two laboratories were co-resistant. Of the 33 sequenced isolates, 29 were sequence type 121, clonal and more distantly related to the European epidemic fusidic acid-resistant impetigo clone (EEFIC) observed in Belgium in 2020. These isolates carried the mupA and fusB genes conferring resistance to mupirocin and fusidic acid, respectively, and the eta and etb virulence genes.ConclusionWe highlight the spread of a mupirocin-resistant EEFIC in children, with a seasonal trend for the third quarter of the year. This is of concern because this variant is resistant to the two main topical antibiotics used to treat impetigo in Belgium.

Exfoliative toxin serotype genes and antibiotic resistance of staphylococcus aureus isolated from children with staphylococcal scalded skin syndrome / 中华皮肤科杂志

Objective To investigate the exfoliative toxin serotype genes and antibiotic resistance of Staphylococcus aureus (SA) isolated from children with staphylococcal scalded skin syndrome (SSSS). Methods In total, 108 strains of SA were isolated from 36 patients with SSSS, 36 patients with impetigo and 36 patients with abscess. Multiplex PCR was used to detect the staphylococcal exfoliative toxin A, B and D genes, Kirby-Baner method to test the susceptibilities of SA strains to 20 antibiotics. Results All the 36 SA isolates from SSSS patients were ET-positive, and 2 (6%) produced ETA, 7 (19%) ETB, 27 (75%) both ETA and ETB; of the 36 isolates from patients with impetigo, 78% produced ET, and 14% produced ETA, 64% produced both ETA and ETB, while no single ETB-producing strain was found; ET was detected in only one (2.8%) SA isolate from abscess patients, which produced both ETA and ETB. ETD was detected in none of the SA isolates. There was a statistical difference in the distribution of ET serotype among the three diseases (χ2=89.4, P < 0.01) and the proportion of ET-producing strains in SSSS group was signifi-cantly higher than that in impetigo group (χ2=9.0, P < 0.01) and abscess group (χ2= 68.1, P < 0.01). All the SA isolates were highly resistant to penicilin, ampicillin, macrolides and clindamycin, but sensitive to other 15 common antibiotics such as cephalosporin. Two strains of MRSA were found in patients with abscess. Conclusion In Chongqing, ET-producing SA is the common pathogenic bacteria of SSSS and impetigo, and most of SA strains produce both ETA and ETB.

An inhibitor of Staphylococcus aureus exfoliative toxin

We describe here an inhibitor of Staphylococcus aureus exfoliative toxin. The toxin was extracted from an S. aureus strain isolated from a case of staphylococcus scalded skin syndrome. The activity of the toxin was compared in tryptic soy broth and brain heart infusion broth. Both supported growth of S. aureus but the culture filtrate of brain heart infusion broth lacked exfoliative toxin activity. Furthermore it appeared to contain a substance that neutralized the action of exfoliative toxin. This suggests the possibility of a treatment for staphylococcal scalded skin syndrome and bullous impetigo