Methicillin-Resistant Staphylococcus aureus from Diabetic Foot Infections in a Tunisian Hospital with the First Detection of MSSA CC398-t571

Abstract

This study sought to analyze the antimicrobial resistant phenotypes and genotypes as well as the virulence content of S. aureus isolates recovered from patients with diabetic foot infections (DFIs) in a Tunisian hospital. Eighty-three clinical samples of 64 patients were analyzed, and bacterial isolates were identified by MALDI-TOF. The antimicrobial resistance phenotypes were determined by the Kirby–Bauer disk diffusion susceptibility test. Resistance and virulence genes, agr profile, spa and SCCmec types were determined by PCR and sequencing. S. aureus was detected in 14 of the 64 patients (21.9%), and 15 S. aureus isolates were recovered. Six out of the fifteen S. aureus isolates were methicillin-resistant (MRSA, mecA-positive) (40%). The isolates harbored the following resistance genes (number of isolates): blaZ (12), erm(B) (2), erm(A) (1), msrA (2), tet(M) (2), tet(K) (3), tet(L) (1), aac(6′)-aph(2′′) (2), ant(4′′) (1) and fexA (1). The lukS/F-PV and tst genes were detected in three isolates. Twelve different spa-types were identified and assigned to seven clonal complexes with the predominance of agr-type III. Furthermore, the SCCmec types III, IV and V were found among the MRSA isolates. Moreover, one MSSA CC398-t571-agr-III isolate was found; it was susceptible to all antimicrobial agents and lacked luk-S/F-PV, tst, eta and etb genes. This is the first report on the prevalence and molecular characterization of S. aureus from DFIs and also the first detection of the MSSA-CC398-t571 clone in human infections in Tunisia. Our findings indicated a high prevalence S. aureus in DFIs with genetic diversity among the MSSA and MRSA isolates.

A Systematic Review of the Microbial Landscape of Diabetic Foot Ulcers in Uganda

“…While the distribution of gram-negative bacteria varies across the continent, Staphylococcus aureus remains the dominant gram-positive isolate as is the case across the globe, emphasizing its role in skin and soft tissue infections. 22–24 …”

“…While the distribution of gramnegative bacteria varies across the continent, Staphylococcus aureus remains the dominant gram-positive isolate as is the case across the globe, emphasizing its role in skin and soft tissue infections. [22][23][24] Another likely explanation for the observed variation in bacterial species isolated across countries and regions of Africa could be the sample specimen used for microbiological assessment which is wound swabs in the case of Uganda. In practice, wound care providers have often adopted wound biopsies (tissue), swabs, curettage, and wound aspirate as principal samples.…”

Staphylococcus aureus Adaptation to the Skin in Health and Persistent/Recurrent Infections

“…The putative advantages of certain S. aureus clones for surviving and persisting in the very particular niche of the DFU have been evaluated by several groups. In all the studies, the S. aureus population colonizing or infecting the DFU was highly diverse, as determined by molecular typing methods [67,71,72,107,108]. However, certain clones were predominant in some geographical regions.…”

“…A recent study conducted with patients from a Tunisian hospital, comprising individuals from different areas in Africa, showed the presence of linages CC5, CC8, CC1, and CC15 among MRSA and lineages CC1, CC12, CC22, and CC398 among MSSA. The strains belonging to CC1 were all spa type t127, a genotype associated with severe infections in the United States and Germany [107]. The molecular characterization of S. aureus isolates from patients with DFU monomicrobial infection in France showed that 18 CCs and 11 ST were found, but 38% of the isolates from patients with diabetic foot osteomyelitis (DFOM) belonged to the MSSA CC398 lineage, whereas 16% of the isolates from patients presenting only skin and soft tissue infection (SSTI) were CC45.…”

“…The presence of CC398 significantly correlated with the severity of the ulcer [110]. The MSSA CC398 is also highly isolated in China and is currently spreading around the world with heterogeneous prevalence and a significant impact on severe infections such as bloodstream infections, endocarditis, and bone joint infections [107,111]. Regarding colonizing lineages, CC5 and CC8 have been described as significantly associated with uninfected DFU, which were able to heal and had a favorable outcome [112].…”