Antimicrobial resistance and virulence of subgingival staphylococci isolated from periodontal health and diseases

Abstract

The dysbiotic biofilm of periodontitis may function as a reservoir for opportunistic human pathogens of clinical relevance. This study explored the virulence and antimicrobial susceptibility of staphylococci isolated from the subgingival biofilm of individuals with different periodontal conditions. Subgingival biofilm was obtained from 142 individuals with periodontal health, 101 with gingivitis and 302 with periodontitis, and cultivated on selective media. Isolated strains were identified by mass spectrometry. Antimicrobial susceptibility was determined by disk diffusion. The mecA and virulence genes were surveyed by PCR. Differences among groups regarding species, virulence and antimicrobial resistance were examined by Chi-square, Kruskal-Wallis or Mann-Whitney tests. The overall prevalence of subgingival staphylococci was 46%, especially in severe periodontitis (> 60%; p < 0.01). S. epidermidis (59%) and S. aureus (22%) were the predominant species across groups. S. condimenti, S. hominis, S. simulans and S. xylosus were identified only in periodontitis. High rates of resistance/reduced sensitivity were found for penicillin (60%), amoxicillin (55%) and azithromycin (37%), but multidrug resistance was observed in 12% of the isolates. Over 70% of the mecA + strains in periodontitis were isolated from severe disease. Higher detection rates of fnB + isolates were observed in periodontitis compared to health and gingivitis, whereas luxF/luxS-pvl + strains were associated with sites with deep pockets and attachment loss (p < 0.05). Penicillin-resistant staphylococci is highly prevalent in the subgingival biofilm regardless of the periodontal status. Strains carrying virulence genes related to tissue adhesion/invasion, inflammation and cytotoxicity support the pathogenic potential of these opportunists in the periodontal microenvironment.

Figure 1

Prevalence of staphylococci species isolated from subgingival biofilm. (A) Observed and expected frequencies of staphylococci among individuals with distinct periodontal conditions. (B) Frequency of Staphylococcus species identified across clinical groups. (C) Increased prevalence of staphylococci in periodontitis patients with more severe disease^,. Significant differences were observed by Chi-square and Fisher’s exact tests (*p < 0.001, **p < 0.01).

Figure 2

Antimicrobial susceptibility of oral staphylococci. Frequency distribution of staphylococci species with resistance and/or low susceptibility to antimicrobials across subgingival biofilm samples from individuals with periodontal health and diseases. Sepi (S. epidermidis), Scap (S. capiti), Sco (S. cohnii), Shaemo (S. haemolyticus), Sho (S. hominis), Ssap (S. saprophyticus), Swar (S. warneri), Ssci (S. sciuri), Sau (S. aureus), Staphy (Staphylococcus sp.).