Prevalence and antimicrobial susceptibility of Gram-negative bacilli in subgingival biofilm associated with periodontal diseases.

BACKGROUND: This cross-sectional study aimed to determine the prevalence and antimicrobial susceptibility of Gram-negative bacilli (GNB) isolated from subgingival biofilm of individuals with different periodontal conditions. METHODS: Subgingival biofilm was obtained from 362 individuals with periodontal health (PH) (n = 83), gingivitis (n = 74), and periodontitis (n = 205), cultivated in broth and selective media. Isolated strains were identified by mass spectrometry. Antimicrobial susceptibility was determined by the Clinical and Laboratory Standards Institute disk diffusion guidelines. Production of extended-spectrum beta-lactamase (ESBL) and carbapenemases were evaluated by double disk synergy test and spectrophotometric detection of imipenem hydrolysis, respectively. ESBL and carbapenemase encoding genes were surveyed by Polymerase chain reaction (PCR). Differences among groups were examined by Chi-square, Kruskal-Wallis or Mann-Whitney tests. RESULTS: GNB were isolated from 36.2% of all subgingival biofilm samples, with a significantly greater prevalence and species diversity (P < 0.001) in patients with periodontitis (45.9%) compared with individuals with PH (24.1%) and gingivitis (22.9%). Pseudomonas aeruginosa (27.5%), Enterobacter cloacae (16.8%), and Enterobacter asburiae (10.7%) were the most predominant species. Resistance/reduced sensitivity to at least 1 antimicrobial was detected in 60% of the strains, but only 4.6% were multidrug resistant. Serratia marcescens, E. cloacae, and Enterobacter kobei presented high rates of intrinsic resistance (>40%) to amoxicillin-clavulanate and first/second-generations of cephalosporins. One strain of Klebsiella pneumoniae isolated from periodontitis was resistant to imipenem, but no ESBL encoding genes or ESBL phenotype was detected. CONCLUSION: High prevalence and diversity of GNB, with low susceptibility to ß-lactams are observed in the subgingival microbiota associated with periodontitis.

Frequency and diversity of Stenotrophomonas spp. carrying blaKPC in recreational coastal waters.

Stenotrophomonas can survive in a wide range of environments and is considered an opportunistic pathogen. Because of its intrinsic resistance to beta-lactams, this genus is considered irrelevant in studies addressing the environmental spread of antimicrobial resistance genes of medical importance. Consequently, studies on environmental Stenotrophomonas carrying acquired carbapenemase-encoding genes are scarce, though not inexistent. Here, we investigated the frequency and diversity of Stenotrophomonas spp. carrying genes encoding carbapenemases of medical relevance in coastal waters with distinct pollution degrees over one year. Among 319 isolates recovered, 220 (68.9%) showed blaKPC. The frequency of blaKPC-positive Stenotrophomonas spp. was not correlated with thermotolerant counts in coastal waters evaluated. All isolates were susceptible to minocycline, levofloxacin, and trimethoprim-sulfamethoxazole. PFGE typing of 101 blaKPC-positive isolates revealed 55 pulsotypes with 5 subtypes, all of which carried the blaKPC-2 variant. Interspecies differentiation of pulsotypes' representatives revealed 55 isolates belonging to the S. maltophilia complex (91.7%) and 5 S. acidaminiphila (8.3%). The blaKPC-2 gene was more frequently harbored on transposable elements found in enterobacteria of clinical origin, especially Tn4401b. Even though beta-lactams are no therapeutic options to treat Stenotrophomonas infections, the occurrence of a highly relevant antimicrobial resistance determinant harbored on mobile genetic elements in a diverse collection of these ubiquitous microorganisms is noteworthy. Therefore, Stenotrophomonas may act as acceptor, stable reservoirs, and potential vectors of antimicrobial resistance in environmental settings, especially aquatic matrices, and should not be neglected.