Staphylococcal enterotoxins: molecular aspects and detection methods

Members of the Staphylococcus genus, especially Staphylococcus aureus, are the most common pathogens found in hospitals and in community-acquired infections. Some of their pathogenicity is associated with enzyme and toxin production. Until recently, S. aureus was the most studied species in the genus; however, in last few years, the rise of infections caused by coagulase-negative staphylococci has pointed out the need for further studies on virulence factors that have not yet been completely elucidated so as to better characterize the pathogenic potential of this group of microorganisms. Several staphylococcal species produce enterotoxins, a family of related proteins responsible for many diseases, such as the toxic-shock syndrome, septicemia and food poisoning. To this date, 23 different enterotoxin types have been identified besides toxic-shock syndrome toxin-1 (TSST-1), and they can be divided into five phylogenetic groups. The mechanism of action of these toxins includes superantigen activity and emetic properties, which can lead to biological effects of infection. Various methods can detect genes that encode enterotoxins and their production. Molecular methods are the most frequently used at present. This review article has the objective to describe aspects related to the classification, structure and regulation of enterotoxins and toxic-shock syndrome toxin-1 detection methods

Synergistic effects of Cinnamomum cassia L. essential oil in combination with polymyxin B against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens.

Multidrug resistance prompts the search for new sources of antibiotics with new targets at bacteria cell. To investigate the antibacterial activity of Cinnamomum cassia L. essential oil (CCeo) alone and in combination with antibiotics against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens. The antimicrobial susceptibility of the strains was determined by Vitek® 2 and confirmed by MALDI-TOF/TOF. The antibacterial activity of CCeo and its synergism with antibiotics was determined using agar disk diffusion, broth microdilution, time-kill, and checkboard methods. The integrity of the bacterial cell membrane in S. marcescens was monitored by protein leakage assay. CCeo exhibited inhibitory effects with MIC = 281.25 μg.mL-1. The association between CCeo and polymyxin B showed a decrease in terms of viable cell counts on survival curves over time after a 4 hour-treatment with a FIC index value of 0.006. Protein leakage was observed with increasing concentrations for CCeo and CCeo + polymyxin B treatments. CCeo showed antibacterial activity against the studied strains. When associated with polymyxin B, a synergistic effect was able to inhibit bacterial growth rapidly and consistently, making it a potential candidate for the development of an alternative treatment and drug delivery system for carbapenemase-producing strains

Genetic Diversity of Virulent Polymyxin-Resistant Klebsiella aerogenes Isolated from Intensive Care Units

This study evaluated the scope and genetic basis of polymyxin-resistant Klebsiella aerogenes in Brazil. Eight polymyxin-resistant and carbapenemase-producing K. aerogenes strains were isolated from patients admitted to the ICU of a tertiary hospital. Bacterial species were identified by automated systems and antimicrobial susceptibility profile was confirmed using broth microdilution. The strains displayed a multidrug resistant profile and were subjected to whole-genome sequencing. Bioinformatic analysis revealed a variety of antimicrobial resistance genes, including the blaKPC-2. No plasmid-mediated colistin resistance gene was identified. Nonetheless, nonsynonymous mutations in mgrB, pmrA, pmrB, and eptA were detected, justifying the colistin resistance phenotype. Virulence genes encoding yersiniabactin, colibactin, and aerobactin were also found, associated with ICEKp4 and ICEKp10, and might be related to the high mortality observed among the patients. In fact, this is the first time ICEKp is identified in K. aerogenes in Brazil. Phylogenetic analysis grouped the strains into two clonal groups, belonging to ST93 and ST16. In summary, the co-existence of antimicrobial resistance and virulence factors is deeply worrying, as it could lead to the emergence of untreatable invasive infections. All these factors reinforce the need for surveillance programs to monitor the evolution and dissemination of multidrug resistant and virulent strains among critically ill patients

High mortality rate associated with KPC-producing Enterobacter cloacae in a Brazilian hospital

We describe a clonal dissemination of KPC-producing Enterobacter cloacae in a Brazilian hospital. Patients diagnosed with theses isolates showed high mortality rate (41.8%) and were associated with previous use of antibiotics and urinary catheterization. Therefore, infection control measures and use of stricter antibiotic policies are required to control the spread of these organisms. (C) 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.Brazilian National Research Council (CNPq)Support Foundation for the Development of Education, Science and Technology in the State of Mato Grosso do Sul (FUNDECT grant)Coordenacao de Aperfeicoamento de Pessoal de Nivel SuperiorFUNDECTUFGD, Lab Pesquisa Ciencias Saude, Dourados, MS, BrazilUFGD, Hosp Univ Dourados, Dourados, MS, BrazilUniv Fed Sao Paulo UNIFESP, Dept Med, Lab ALERTA, Disciplina Infectol, Sao Paulo, BrazilFdn Osvaldo Cruz, Campo Grande, MS, BrazilUniv Fed Sao Paulo UNIFESP, Dept Med, Lab ALERTA, Disciplina Infectol, Sao Paulo, BrazilCNPq: 480949/2013-1FUNDECT: 0077/12FUNDECT: 0212/12Web of Scienc

A high mortality rate associated with multidrug-resistant Acinetobacter baumannii ST79 and ST25 carrying OXA-23 in a Brazilian intensive care unit.

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofblaOXA-23 and blaOXA-51 genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients