Whole genome sequencing and pan-genome analysis of Staphylococcus/Mammaliicoccus spp. isolated from diabetic foot ulcers and contralateral healthy skin of Algerian patients

Background Diabetic foot infections (DFIs) are the most common complications of diabetic foot ulcers (DFUs), and a significant cause of lower extremity amputation.

In this study we used whole genome sequencing to characterize the clonal composition, virulence and resistance genetic determinants of 58 Staphylococcus/Mammaliicoccus spp. isolates from contralateral healthy skin and DFU from 44 hospitalized patients.

Results S. aureus (n = 32) and S. epidermidis (n = 10) isolates were recovered from both DFUs and healthy skin, whereas, S. haemolyticus (n = 8), M. sciuri (n = 1), S. hominis (n = 1) and S. simulans (n = 3) were recovered exclusively from healthy skin.

In contrast, S. caprae (n = 2) and S. saprophyticus (n = 1) were recovered only from DFUs.

Among S. aureus isolates, MRSA were present with high prevalence (27/32, 84.4%), 18 of which (66.7%) were from DFUs and 9 (33.3%) from healthy skin.

In contrast, the coagulase-negative Staphylococcus (CoNS)/ Mammaliicoccus isolates (n = 26), in particular S. epidermidis and S. haemolyticus were more prevalent in healthy skin, (10/26, 38.5%) and (8/26, 30.8%), respectively.

MLST, spa and SCC mec typing classified the 32 S. aureus isolates into 6 STs, ST672, ST80, ST241, ST1, ST97, ST291 and 4 unknown STs (STNF); 8 spa types, t044, t037, t3841, t1247, t127, t639, t937 and t9432 and 2 SCC mec types, type IV and type III(A).

Among CoNS, the S. epidermidis isolates belonged to ST54, ST35 and ST640.

S. haemolyticus belonged to ST3, ST25, ST29, ST1 and ST56.

The sole M. sciuri isolate was found to carry an SCC mec type III(A).

A wide range of virulence genes and antimicrobial resistance genes were found among our isolates, with varying distribution between species or STs.

The pan-genome analysis revealed a highly clonal population of Staphylococcus isolates, particularly among S. aureus isolates.

Interestingly, the majority of S. aureus isolates including MRSA, recovered from the healthy skin and DFUs of the same patient belonged to the same clone and exhibited similar virulence/resistance genotype.

Conclusions Our study provides clinically relevant information on the population profile, virulence and antibiotic resistance of Staphylococcus/Mammaliicoccus spp. in DFIs, which could serve as a basis for further studies on these as well as other groups of pathogens associated with DFIs.