Structural and functional features of modified heat-stable toxins produced by enteropathogenic Klebsiella cells

The Citizen Phage Library: Rapid Isolation of Phages for the Treatment of Antibiotic Resistant Infections in the UK

Antimicrobial resistance poses one of the greatest threats to global health and there is an urgent need for new therapeutic options. Phages are viruses that infect and kill bacteria and phage therapy could provide a valuable tool for the treatment of multidrug-resistant infections. In this study, water samples collected by citizen scientists as part of the Citizen Phage Library (CPL) project, and wastewater samples from the Environment Agency yielded phages with activity against clinical strains Klebsiella pneumoniae BPRG1484 and Enterobacter cloacae BPRG1482. A total of 169 and 163 phages were found for K. pneumoniae and E. cloacae, respectively, within four days of receiving the strains. A third strain (Escherichia coli BPRG1486) demonstrated cross-reactivity with 42 E. coli phages already held in the CPL collection. Seed lots were prepared for four K. pneumoniae phages and a cocktail combining these phages was found to reduce melanisation in a Galleria mellonella infection model. The resources and protocols utilised by the Citizen Phage Library enabled the rapid isolation and characterisation of phages targeted against multiple strains. In the future, within a clearly defined regulatory framework, phage therapy could be made available on a named-patient basis within the UK.

Non-Digestible Oligosaccharides and Short Chain Fatty Acids as Therapeutic Targets against Enterotoxin-Producing Bacteria and Their Toxins

Enterotoxin-producing bacteria (EPB) have developed multiple mechanisms to disrupt gut homeostasis, and provoke various pathologies. A major part of bacterial cytotoxicity is attributed to the secretion of virulence factors, including enterotoxins. Depending on their structure and mode of action, enterotoxins intrude the intestinal epithelium causing long-term consequences such as hemorrhagic colitis. Multiple non-digestible oligosaccharides (NDOs), and short chain fatty acids (SCFA), as their metabolites produced by the gut microbiota, interact with enteropathogens and their toxins, which may result in the inhibition of the bacterial pathogenicity. NDOs characterized by diverse structural characteristics, block the pathogenicity of EPB either directly, by inhibiting bacterial adherence and growth, or biofilm formation or indirectly, by promoting gut microbiota. Apart from these abilities, NDOs and SCFA can interact with enterotoxins and reduce their cytotoxicity. These anti-virulent effects mostly rely on their ability to mimic the structure of toxin receptors and thus inhibiting toxin adherence to host cells. This review focuses on the strategies of EPB and related enterotoxins to impair host cell immunity, discusses the anti-pathogenic properties of NDOs and SCFA on EPB functions and provides insight into the potential use of NDOs and SCFA as effective agents to fight against enterotoxins.

Estudo etiológico da diarréia em crianças hospitalizadas no Instituto Materno Infantil Prof. Fernando Figueira, IMIP, em Recife, Pernambuco

OBJETIVOS: identificar enteropatógenos nas fezes de crianças hospitalizadas com diarréia. MÉTODOS: estudo de série de casos, com a participação de 36 crianças entre zero a 60 meses, com diarréia, hospitalizadas no Instituto Materno Infantil Prof. Fernando Figueira, IMIP, no período entre janeiro e maio de 2005. Foram coletadas as variáveis sócio-demográficas, características das mães e do episódio diarréico. A pesquisa etiologica utilizou coprocultura e testes sorológicos. RESULTADOS: a maioria das crianças (80,5%) tinha menos de 12 meses. As famílias tinham precárias condições socioeconômicas e 83,4% tinha renda per capita inferior a meio salário mínimo/mês. Quanto aos microorganismos recuperados nas culturas de fezes, a E. coli enteropatogênica clássica (EPEC) apareceu em 8,4% dos casos, não havendo crescimento de Salmonella sp. ou Shiguella sp. e a Klebsiella sp. ESBL + foi isolada em 33,3% dos pacientes. As Klebsiellas apresentaram um alto perfil de resistência no antibiograma, compatível com as cepas hospitalares catalogadas na instituição. CONCLUSÕES: o estudo apresentou uma baixa taxa de recuperação de bactérias enteropatogênicas mas revelou uma prevalência de Klebsiella multirresistente, o que tem importantes implicações no risco de infecção hospitalar e persistência do episódio diarréico.

Microbial diversity and prevalence of virulent pathogens in biofilms developed in a water reclamation system

Bacterial biofilm is a common phenomenon in both natural and engineered systems which often becomes a source of contamination and microbially influenced corrosion. It is thought that formation of biofilm in the monoculture of several bacterial species is regulated by acylhomoserine lactone (AHL) quorum-sensing signals. In this study, we investigated the microbial diversity and existence of AHL-producing and AHL-degrading bacterial species in the biofilm samples from a water reclamation system located in a tropical environment. 16S ribosomal DNA sequencing analysis indicated the presence of at least 11 bacterial species, including the frequently encountered bacterial pathogens Pseudomonas aeruginosa and Klebsiella pneumoniae, and several rare pathogens. We showed that only two groups of isolates, belonging to P. aeruginosa and Enterobacter agglomerans, produced AHL signals. We also found that three bacterial isolates, i.e., Agrobacterium tumefaciens XJ01, Bacillus cereus XJ08, and Ralstonia sp. XJ12, expressed AHL degradation enzymes. Furthermore, we showed that P. aeruginosa isolate HL43 was virulent against animal model Caenorhabditis elegans and released 2-6-fold more pyocyanin cytotoxin than P. aeruginosa strains PA01 and PA14, the two commonly used laboratory strains. These data indicate the complexity and importance of biofilm research in water reclamation.