RESUMO
Acinetobacter baumannii is an emerging pathogen associated with nosocomial infections and multidrug resistance. Polymyxin B has been used to treat infections caused by multidrug-resistant (MDR) A. baumannii but an increase in polymyxin B resistance has been observed. We aimed to determine the diversity, antimicrobial susceptibility, presence of polymyxin B heteroresistance and adaptive resistance in 72 A. baumannii clinical isolates from two public hospitals in Rio de Janeiro. The isolates were identified by sequencing of rpoB gene. Determination of the genetic diversity of isolates was performed by pulsed-field gel electrophoresis and oxacillinases genes were detected by polymerase chain reaction. The polymyxin B heteroresistance was analyzed by population analysis profile and adaptive resistance was evaluated after serial daily passages of isolates in broth containing increasing polymyxin B concentrations. The results showed that 49% of the isolates were collected from respiratory system and 62% were MDR, while 35% were extensively drug resistant. Additionally, all the isolates carried blaOXA-23-like, blaOXA-51-like genes and ISAba1, while 1% had blaOXA-24-like gene. The association of ISAba1-blaOXA-23 was found in 96% of the isolates. Polymyxin B heteroresistance was found in 36% of the isolates and polymyxin B adaptive resistance was not found in the isolates. Our study demonstrated the high resistance to antimicrobials used in clinical practice and the spread of oxacillinases genes and insertion sequence (IS). We also reported the presence of heteroresistance to polymyxin B used as a last-resort therapy for MDR A. baumannii.
Assuntos
Infecções por Acinetobacter , Acinetobacter baumannii , Preparações Farmacêuticas , Acinetobacter baumannii/genética , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Brasil , Farmacorresistência Bacteriana Múltipla/genética , Humanos , Testes de Sensibilidade Microbiana , Polimixina B/farmacologia , beta-LactamasesRESUMO
Acinetobacter baumannii has been associated with antimicrobial resistance and ability to form biofilms. Furthermore, its adherence to host cells is an important factor to the colonization process. Therefore, this study intended to identify some virulence factors that can explain the success of A. baumannii in causing nosocomial infections. We studied 92 A. baumannii isolates collected from hospitals in Rio de Janeiro, Brazil. Isolates were identified and the susceptibility to antimicrobials was determined. Oxacilinase type ß-lactamase encoding genes were amplified by polymerase chain reaction, and genetic diversity was investigated by pulsed-field gel electrophoresis (PFGE). In addition, biofilm formation on polystyrene plates using crystal violet staining was quantified, and adherence to human cell lines was evaluated. Eighty-six isolates were multidrug-resistant, of which 93% were carbapenem-resistant. All isolates had the blaOXA-51 gene and 94% had the blaOXA-23 gene, other searched blaOXA genes were not detected. PFGE typing showed two predominant clones, and biofilm production was observed in 79% of isolates. A. baumannii isolates adhered better to HEp-2 cell compared with A-549 cell. Clones A, B, E, and F showed a significantly increased adherence to HEp-2 compared with adherence to A-549 cell. Our findings revealed that A. baumannii isolates had high frequencies of resistance to antimicrobial agents, ability to form biofilm, and capacity to adhere to HEp-2 cells.
Assuntos
Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/fisiologia , Aderência Bacteriana , Farmacorresistência Bacteriana Múltipla , Células Epiteliais/microbiologia , Células A549 , Infecções por Acinetobacter/microbiologia , Acinetobacter baumannii/enzimologia , Acinetobacter baumannii/genética , Antibacterianos/farmacologia , Biofilmes , Carbapenêmicos/farmacologia , Variação Genética , Humanos , Testes de Sensibilidade Microbiana , beta-Lactamases/genéticaRESUMO
Streptococcus dysgalactiae subsp. equisimilis (SDSE) isolates are the most common group C streptococci in humans and reports of invasive infections associated with SDSE have been increasing. Molecular epidemiology studies are an important strategy to trace the emergence and spread of possible well-fit bacterial pathogens of humans and animals. In this work, we analysed the antimicrobial and clonal profiles of 115 SDSE infection and colonization isolates of human and equine origin. PFGE revealed the spread of two main clusters: clone A (57.4%) and clone A (26.1%). Remarkably, two isolates from clone B obtained from human colonization cases displayed identical PFGE patterns to those of three equine infection isolates. In addition, multilocus sequence typing allocated these isolates to ST129 (CC31). All of the SDSE isolates were susceptible to penicillin, vancomycin, gentamicin, levofloxacin and chloramphenicol. Tetracycline and erythromycin resistance rates were 65.2 and 13.9% respectively. Nevertheless, none of the isolates displaying sporadic PFGE patterns showed erythromycin resistance. The majority of erythromycin-resistant isolates from clone A had inducible resistance to macrolides, lincosamines and streptogramins B (iMLSB phenotype), which is associated with the presence of the ermA gene, whereas the resistant isolates from clone B showed the M phenotype, associated with the mefA gene. In conclusion, the data indicated that the analysed collection of SDSE isolates displayed a clonal structure and that the isolates found in human colonization cases could also be involved in equine infections.