Identification and antimicrobial susceptibility profile of bacteria isolated from primary endodontic infections.

This study aimed to identify and characterize the antimicrobial susceptibility profile of bacteria found in primary endodontic infections in the teeth of patients treated at the Dental Clinic of the University of Ribeirão Preto, São Paulo, Brazil. From September to December 2019, samples were obtained from 21 patients with primary endodontic infections. The collections were carried out in triplicate using paper cones placed close to the total length of the root canal. Bacterial isolation was performed in Brain Heart Infusion agar, Blood agar, and other selective culture media cultured at 37°C for up to 48 h under aerobiosis and microaerophilic conditions. The bacterial species were identified using the Vitek 2 automated system. The disk diffusion method on agar Müeller-Hinton was used to assess antimicrobial susceptibility with the recommended antimicrobials for each identified bacterial species. A total of 49 antibiotics were evaluated. Fifteen of the 21 samples collected showed bacterial growth, and 17 bacterial isolates were found. There were 10 different bacterial species identified: Enterococcus faecalis (four isolates), Streptococcus mitis/oralis (three isolates), Streptococcus anginosus (three isolates) being the most common, followed by Staphylococcus epidermidis, Enterococcus faecium, Streptococcus constellatus, Streptococcus alactolyticus, Enterobacter cloacae, Klebsiella variicola, and Providencia rettgeri (one isolate of each species). The analysis demonstrated significant susceptibility to most of the tested antibiotics. However, some Enterococcus isolates resisted the antibiotic's erythromycin, ciprofloxacin, and tetracycline. A Staphylococcus epidermidis isolate was characterized as multidrug-resistant. Five Streptococcus isolates were non-susceptible to all antibiotics tested.

Molecular characterisation of multidrug-resistant Klebsiella pneumoniae belonging to CC258 isolated from outpatients with urinary tract infection in Brazil.

OBJECTIVES: This study characterised 48 Klebsiella pneumoniae isolates from outpatients with urinary tract infection in the micro-region of Ribeirão Preto, located in southeastern Brazil. METHODS: The isolates were identified by conventional biochemical and phenotypic tests and were confirmed as K. pneumoniae using a MALDI-TOF VITEK® MS system. Antimicrobial susceptibility testing was performed by the disk diffusion method as recommended by the Clinical and Laboratory Standards Institute (CLSI) using 38 different antibiotic discs. Fifteen ß-lactamase and ten virulence genes were investigated by PCR. Clonal relationships among the isolates were determined by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and multilocus sequence typing (MLST). RESULTS: Of the 48 isolates, 29 (60.4%) were classified as multidrug-resistant. A total of 46 ß-lactamase genes were found in 27 (56.3%) of the isolates, with blaKPC being the most prevalent distributed in 18 isolates (37.5%). Moreover, 73 virulence genes were found in 30 isolates (62.5%). ERIC-PCR results showed high genetic diversity among the isolates. Twelve different sequence types (STs) were found by MLST (ST14, ST17, ST101, ST200, ST334, ST433, ST437, ST442, ST449, ST502, ST1246 and ST2729), with ST2729 being described for the first time in this study. Seven STs were grouped in clonal complex 258 (CC258) frequently associated with various resistance and virulence genes. CONCLUSIONS: These results raise concern about epidemiological surveillance related to colonisation of patients discharged from hospitals in order to prevent both the occurrence and spread of resistant bacterial infections in the community.