RESUMO
Hafnia alvei is a Gram-negative facultatively anaerobic bacillus that constitutes part of the human gut flora. Until recently, H. alvei strains could be mistakenly identified by conventional methods, miniaturisation or automatic systems as members of the Serratia, Escherichia, Citrobacter, Yokenella, Obesumbacterium or Salmonella genera. Consequently, molecular techniques were required for their definitive identification in the clinical laboratory. In addition, a new Hafnia species, H. paralvei, has recently appeared, which undoubtedly includes many of the strains reported in the literature as H. alvei. Alrhough H. alvei isolation from human clinical specimens remains uncommon, the development of drug resistance due to this species is emerging and it is likely that this organism will gain increasing importance in the future. Moreover, although H. alvei shares some virulence mechanisms with other Gram-negative enteropathogens, little is known about the factors that contribute to its pathogenesis in humans. The present article reviews the current identification methods, antimicrobial resistance and virulence factors of this bacterium.
Assuntos
Infecções por Enterobacteriaceae , Hafnia alvei , Farmacorresistência Bacteriana , Infecções por Enterobacteriaceae/microbiologia , Hafnia alvei/classificação , Hafnia alvei/efeitos dos fármacos , Hafnia alvei/patogenicidade , Humanos , Fatores de VirulênciaRESUMO
Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4.
Assuntos
Astacoidea/parasitologia , Hafnia alvei/isolamento & purificação , Hafnia alvei/fisiologia , Truta/parasitologia , Animais , Bulgária , Genes Bacterianos/genética , Hafnia alvei/genética , Hafnia alvei/patogenicidade , RNA Ribossômico 16S/genéticaRESUMO
Attaching-effacing lesion-inducing Escherichia albertii and the related, but non-attaching-effacing organism, Hafnia alvei, are both implicated as enteric pathogens in humans. However, effects of these bacteria on epithelial cells are not well-characterized. Related enteropathogens, including enterohemorrhagic Escherichia coli O157:H7, decrease epithelial barrier function by disrupting intercellular tight junctions in polarized epithelia. Therefore, this study assessed epithelial barrier function and tight junction protein distribution in polarized epithelia following bacterial infections. Polarized epithelial (MDCK-I and T84) cells grown on filter supports were infected apically with E. coli O157:H7, E. albertii, and H. alvei for 16h at 37 degrees C. All strains decreased transepithelial electrical resistance and increased permeability to a dextran probe in a host cell-dependent manner. Immunofluorescence microscopy showed that both E. coli O157:H7 and E. albertii, but not H. alvei, caused a redistribution of the tight junction protein zona occludens-1. In contrast to E. coli O157:H7, E. albertii and H. alvei did not redistribute claudin-1. Western blotting of whole cell protein extracts demonstrated that each bacterium caused differential changes in tight junction protein expression, dependent on the host cell. These findings demonstrate that E. albertii and H. alvei are candidate enteric pathogens that have both strain-specific and host epithelial cell-dependent effects.
Assuntos
Infecções por Enterobacteriaceae/microbiologia , Escherichia/patogenicidade , Hafnia alvei/patogenicidade , Intestinos/microbiologia , Junções Íntimas/microbiologia , Animais , Aderência Bacteriana , Linhagem Celular , Permeabilidade da Membrana Celular , Claudina-1 , Cães , Infecções por Enterobacteriaceae/metabolismo , Células Epiteliais/metabolismo , Células Epiteliais/microbiologia , Escherichia/fisiologia , Escherichia coli O157/patogenicidade , Hafnia alvei/fisiologia , Humanos , Mucosa Intestinal/metabolismo , Proteínas de Membrana/metabolismo , Junções Íntimas/metabolismoRESUMO
AIMS: The aim of this study was to investigate the invasion and intracellular survival of different Hafnia alvei strains in HeLa cells. METHODS AND RESULTS: We performed different experiments on the bacterial invasion of different strains of H. alvei into the HeLa cell line using gentamicin protection assays and immunofluorescence. We also report the time course of cell internalization and the effects of inhibitors on the invasion of H. alvei. Levels of invasion varied depending on the conditions (strain, time and inoculum size) used. CONCLUSIONS: This study revealed that H. alvei strains were able to enter and persist in a human epithelial cell line. SIGNIFICANCE AND IMPACT OF THE STUDY: Our in vitro findings highlight the possibility that some H. alvei strains may exploit nonprofessional phagocytes or nonphagocytic cells to spread in vivo, which may be important for the persistence and establishment of an asymptomatic carrier state.
Assuntos
Células Epiteliais/microbiologia , Hafnia alvei/patogenicidade , Aderência Bacteriana/efeitos dos fármacos , Aderência Bacteriana/fisiologia , Linhagem Celular , Citocalasina D/farmacologia , Imunofluorescência , Gentamicinas , Hafnia alvei/efeitos dos fármacos , Humanos , Inibidores da Síntese de Ácido Nucleico/farmacologiaRESUMO
The genus Hafnia, a member of the family Enterobacteriaceae, consists of gram-negative bacteria that are occasionally implicated in both intestinal and extraintestinal infections in humans. Despite the fact that the genus currently contains only a single species (H. alvei), more extensive phylogenetic depth (two or more species) is apparent based upon DNA relatedness and 16S rRNA gene sequencing studies. Hafnia causes a variety of systemic infections, including septicemia and pneumonia; however, its role as a gastrointestinal pathogen is controversial. Many of the data supporting a role for hafniae as enteric pathogens were incorrectly attributed to this genus rather than to the actual pathogen, Escherichia albertii. There are numerous gaps in our understanding of this genus, including ecologic habitats and population genetics, disease-producing role in animals, phenetic and genetic methods useful in distinguishing genomospecies within the H. alvei complex, and bona fide pathogenicity factors.
Assuntos
Infecções por Enterobacteriaceae/epidemiologia , Gastroenterite/epidemiologia , Hafnia , Animais , Criança , Infecções por Enterobacteriaceae/microbiologia , Infecções por Enterobacteriaceae/fisiopatologia , Microbiologia Ambiental , Gastroenterite/microbiologia , Gastroenterite/fisiopatologia , Hafnia/classificação , Hafnia/genética , Hafnia/isolamento & purificação , Hafnia/patogenicidade , Hafnia alvei/genética , Hafnia alvei/isolamento & purificação , Hafnia alvei/patogenicidade , HumanosRESUMO
Virulence factors (eae gene, haemolytic capacity, fimbriae, resistance to the bactericidal effect of serum, siderophore production) and pathogenicity for gilthead seabream, Sparus aurata L., were analysed for 23 Hafnia alvei strains. None of the strains used in LD50 studies were lethal for seabream at doses as high as >10(8) cfu mL(-1). In chronic challenge studies differences in severity of the inflammatory response were observed between strains. On the basis of correlation of the inflammatory response to different strains of H. alvei in seabream with those virulence factors studied, it was only possible to establish a positive correlation between pathogenicity and resistance to the bactericidal effect of fish serum. Gilthead seabream is thus a species with considerable resistance to experimental infection with H. alvei. The bacterium does, however, have the capacity to remain viable in seabream for up to 3 months, without any clinical signs. Hafnia alvei is a well-recognized human and animal pathogen. Thus, as the pathogen can coexist with aquaculture operations, cultured gilthead seabream could represent a risk to human health as a carrier in some circumstances.
Assuntos
Infecções por Enterobacteriaceae/veterinária , Fímbrias Bacterianas/metabolismo , Doenças dos Peixes/microbiologia , Hafnia alvei/patogenicidade , Dourada , Fatores de Virulência/metabolismo , Adesinas Bacterianas/genética , Animais , Aquicultura , Infecções por Enterobacteriaceae/metabolismo , Eritrócitos/metabolismo , Doenças dos Peixes/metabolismo , Cobaias , Hafnia alvei/genética , Hemólise/fisiologia , Hidroxibenzoatos , Imuno-Histoquímica/veterinária , Dose Letal Mediana , Sideróforos/biossíntese , Especificidade da EspécieRESUMO
A bacterium originally described as Hafnia alvei induces diarrhea in rabbits and causes epithelial damage similar to the attachment and effacement associated with enteropathogenic Escherichia coli. Subsequent studies identified similar H. alvei-like strains that are positive for an intimin gene (eae) probe and, based on DNA relatedness, are classified as a distinct Escherichia species, Escherichia albertii. We determined sequences for multiple housekeeping genes in five E. albertii strains and compared these sequences to those of strains representing the major groups of pathogenic E. coli and Shigella. A comparison of 2,484 codon positions in 14 genes revealed that E. albertii strains differ, on average, at approximately 7.4% of the nucleotide sites from pathogenic E. coli strains and at 15.7% from Salmonella enterica serotype Typhimurium. Interestingly, E. albertii strains were found to be closely related to strains of Shigella boydii serotype 13 (Shigella B13), a distant relative of E. coli representing a divergent lineage in the genus Escherichia. Analysis of homologues of intimin (eae) revealed that the central conserved domains are similar in E. albertii and Shigella B13 and distinct from those of eae variants found in pathogenic E. coli. Sequence analysis of the cytolethal distending toxin gene cluster (cdt) also disclosed three allelic groups corresponding to E. albertii, Shigella B13, and a nontypeable isolate serologically related to S. boydii serotype 7. Based on the synonymous substitution rate, the E. albertii-Shigella B13 lineage is estimated to have split from an E. coli-like ancestor approximately 28 million years ago and formed a distinct evolutionary branch of enteric pathogens that has radiated into groups with distinct virulence properties.
Assuntos
Escherichia/classificação , Escherichia/genética , Shigella boydii/genética , Adesinas Bacterianas/genética , Sequência de Aminoácidos , Animais , Toxinas Bacterianas/genética , Toxinas Bacterianas/toxicidade , Linhagem Celular , DNA Bacteriano/química , DNA Bacteriano/isolamento & purificação , Diarreia/microbiologia , Infecções por Enterobacteriaceae/microbiologia , Escherichia/isolamento & purificação , Escherichia/patogenicidade , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Evolução Molecular , Hafnia alvei/classificação , Hafnia alvei/genética , Hafnia alvei/patogenicidade , Humanos , Dados de Sequência Molecular , Filogenia , Coelhos , Salmonella typhimurium/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência , VirulênciaRESUMO
The data obtained in the clinical and laboratory study of 72 hospitalized patients with acute enteric infection are presented. The observed outbreak was caused by H. alvei producing heat-stable enterotoxin. The role of this etiological agent is also confirmed by simultaneous occurrence of the disease after using the same foodstuff, a short incubation period, the severity of the course of the disease with pronounced symptoms of neurotoxicosis, a high detection rate of H. alvei in material taken from patients at the acute period of the disease, rapid disappearance of this agent in the period of convalescence and a pronounced rise in the titer of specific antibodies to H. alvei in the dynamics of the disease. At the same time in the feces of 8 patients rotavirus antigen was detected, which, in combination with residual catarrhal phenomena, hyperemia and granularity of the pharynx, yellow stool, was indicative of the simultaneous circulation of rotavirus among these patients.
Assuntos
Infecções por Enterobacteriaceae/complicações , Infecções por Enterobacteriaceae/microbiologia , Gastroenterite/microbiologia , Hafnia alvei/patogenicidade , Infecções por Rotavirus/complicações , Infecções por Rotavirus/microbiologia , Rotavirus/patogenicidade , Doença Aguda , Adolescente , Adulto , Anticorpos/sangue , Antígenos/sangue , Convalescença , Surtos de Doenças , Fezes/microbiologia , Hafnia alvei/isolamento & purificação , Humanos , Masculino , Síndromes Neurotóxicas/microbiologia , Rotavirus/isolamento & purificação , Índice de Gravidade de DoençaRESUMO
INTRODUCTION: Hafnia alvei is a commensal organism of the digestive tract. It is best known as an agent of pediatric gastro-enteritis. In adults, this organism may exceptionally be responsible for extra-intestinal infections. In such cases, infections occur mainly in unusually susceptible patients, due to an underlying condition. CASE REPORT: A 69 year-old man who had recently undergone surgery for a gastric stromal tumor was admitted to hospital because of H. alvei bacteremia accompanied by liver and right iliac muscle abscesses. The course was favourable with a 60 day treatment of fluoroquinolone. COMMENTARY: H. alvei is usually considered as moderately or non pathogenic for humans. However, recent descriptions of severe community or nosocomial infections due to H. alvei have challenged this belief. The actual role of H. alvei in human disease remains to be defined.
Assuntos
Abscesso/microbiologia , Infecções por Enterobacteriaceae/complicações , Hafnia alvei/patogenicidade , Hepatopatias/microbiologia , Doenças Musculares/microbiologia , Complicações Pós-Operatórias , Abscesso/tratamento farmacológico , Abscesso/patologia , Idoso , Anti-Infecciosos/uso terapêutico , Infecção Hospitalar , Infecções por Enterobacteriaceae/tratamento farmacológico , Infecções por Enterobacteriaceae/patologia , Fluoroquinolonas , Humanos , Hepatopatias/tratamento farmacológico , Hepatopatias/patologia , Masculino , Doenças Musculares/tratamento farmacológico , Doenças Musculares/patologia , Resultado do TratamentoRESUMO
Extra-intestinal Hafnia alvei isolates are rarely considered to be pathogenic. To investigate whether such strains are able to produce virulence factors, a total of 70 clinical H. alvei isolates was compared with clinical extra-intestinal isolates of other members of the enterobacterial tribe Klebsiellae (Kiebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens). Whereas mannose-sensitive haemagglutination (MSHA) was less common in H. alvei (59%) than in K. pneumoniae (86%) and E. cloacae (89%) isolates, the incidences of mannose-resistant haemagglutination indicative of type 3 pili (MR/K-HA) and of serum resistance properties were not lower. All H. alvei strains secreted siderophores but, unlike the other enterobacterial species examined, the siderophore type was neither enterobactin nor aerobactin. Although the low pathogenicity of H. alvei isolates could not be attributed to any of the factors investigated, the mean number of factors expressed by each H. alvei isolate was significantly lower than that expressed by K. pneumoniae and E. cloacae isolates but did not differ significantly from that of S. marcescens. Based on these findings, the low pathogenicity of H. alvei appears to be due to its low frequency of expression of virulence factors as compared with clinically significant species such as K. pneumoniae and E. cloacae.