Viable but non-culturable forms of potentially pathogenic bacteria in water

McKay, A.M.

doi:10.1111/j.1472-765x.1992.tb00667.x

Cited by 104 publications

(49 citation statements)

References 41 publications

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“…The ultrastructural changes in the bacteria may also be related to a physiological change in the bacteria to a so-called viable but non-culturable form. 14 It is interesting that the changes in morphology of EHEC-O157 3 days after feeding coincided with the drastic decrease in the number of the bacteria in the alimentary canal. Our data clearly show that EHEC-O157 was actively FIGURE 4.…”

Section: Discussionmentioning

confidence: 99%

Houseflies: not simple mechanical vectors of enterohemorrhagic Escherichia coli O157:H7.

Kobayashi¹,

Sasaki²,

Saito³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

180

117

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Abstract. An epidemic of enterohemorrhagic colitis caused by Escherichia coli O157:H7 (EHEC-O157) occurred in a nursery school in a rural area of Japan in September 1996. The EHEC-O157 were isolated both from patients and houseflies collected at the school. The flies were suspected to be mechanical vectors of the pathogen. Feeding experiments of EHEC-O157 to houseflies showed that the ingested bacteria were harbored in the intestine of flies and continued to be excreted at least for 3 days after feeding. Scanning electron microscopy showed that a large number of EHEC-O157 adhered to the surface of the housefly mouthparts and actively proliferated in the minute spaces of the labellum. Food masses containing EHEC-O157 in the fly intestine were completely surrounded by a peritrophic membrane during digestion and discharged rapidly. The persistence of bacteria in the intestine and feces is mainly a result of proliferation in the mouthparts and accumulation in the crop. Our results strongly suggest that houseflies are not simple mechanical vectors of EHEC. The epidemiologic potential of houseflies to disseminate EHEC-O157 may be greater than initially suspected.The housefly (Musca domestica vicina) and flies in general are considered to be mechanical vectors of many kinds of pathogens such as bacteria, 1,2 protozoa, 3 viruses, 4 and helminth eggs. 5,6 In recent outbreaks of enterohemorrhagic colitis in nursery schools in Japan, the epidemiologic survey isolated enterohemorrhagic Escherichia coli O157:H7 (EHEC-O157) from both houseflies collected in the school and from patients. The DNA patterns and the type of verotoxin were identical in EHEC-O157 isolated from both flies and patients. 7,8 This result strongly indicated that houseflies in nursery schools disseminated EHEC-O157 to foods, drinks, plates, and utensils, although direct evidence of the transmission has not been clarified. The infective dose for EHEC-O157 is considered to be very low, similar to that of Shigella flexneri or S. dysenteriae. 9,10 There are many qualitative reports of microbial flora in flies, but there are no reports of the number of bacteria that are harbored in the intestine or crop or how long the potential for dissemination of bacteria persists. We investigated the vector potential of houseflies for EHEC-O157 by feeding the flies with bacteria and monitoring them for several days after feeding. We also used scanning electron microscopy to determine whether EHEC-O157 adhered to the surface of housefly mouthparts and transmission electron microscopy to determine whether bacteria proliferated and persisted in the alimentary canal of flies. MATERIALS AND METHODS Experimental feeding of EHEC-O157 to houseflies.Houseflies maintained in our insectary were used. Two strains of EHEC-O157 (verotoxin 1-or verotoxin 1Ϫ and 2Ϫproducing strains) were grown in trypticase soy broth (Becton Dickinson, Cockeysville, MD). The concentration of bacteria was approximately 10 9 colony-forming units (CFU)/ml. Adult (6-8-day old), female flies were allowed to fe...

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Section: Discussionmentioning

confidence: 99%

Houseflies: not simple mechanical vectors of enterohemorrhagic Escherichia coli O157:H7.

Kobayashi¹,

Sasaki²,

Saito³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

180

117

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“…retaining basal metabolic activities) yet unable to grow in artificial media in the laboratory (Barer et al, 1993;Oliver, 2005Oliver, , 2010. This state is believed to be a survival strategy of enteric bacteria that are released into the environment and suffer prolonged exposure to environmental stressors such as suboptimal temperature; U. V. irradiation; nutrient deprivation and biological interactions (McKay, 1992;Barer & Harwood, 1999). Xu et al (1982) were the first to address the VBNC phenomenon in enteric bacteria when they examined the survival of Vibrio cholerae and Escherichia coli in estuarine and marine water microcosms.…”

Section: Survival In Naturementioning

confidence: 99%

Salmonellae in the Environment

Abulreesh¹

2012

Salmonella - Distribution, Adaptation, Control Measures and Molecular Technologies

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“…Others regard this state as a survival strategy, in response to adverse environmental conditions and consider that VBNC response can represent a genetically programmed physiological adaptation [39]. In addition, VBNC cells have been shown to be able to retain virulence [16,30]. All these experiments have led us to consider the VBNC state in pathogenic bacteria as a potential threat to public health.…”

Section: Introductionmentioning

confidence: 99%

Avirulent Viable But Non Culturable cells ofListeria monocytogenesneed the presence of an embryo to be recovered in egg yolk and regain virulence after recovery

et al. 2007

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-The aim of this study was to assess the efficiency of the embryonated egg model to recover Viable But Non Culturable (VBNC) cells of Listeria monocytogenes. L. monocytogenes cells were incubated in filtered sterilised distilled water. The VBNC state was obtained after a 25 to 47 days incubation period (concentration of culturable cells less than 1 cfu/mL). Fifteen days after the VBNC state was reached, non culturability was checked in various media. One milliliter of each VBNC suspension that contained 10 4 metabolically active cells (i.e. Direct Viable Count + cells) was inoculated into the vitellus fluid of embryonated and non-embryonated eggs. Culturable cells were detected in a large proportion of the embryonated eggs (18/32), but not in the non-embryonated eggs (1/32). The recovery rate was higher after culture of the vitellus fluid plus embryo (18/32) than after culture of the vitellus fluid alone (6/32). The results indicate that the embryo likely plays a prominent part in the recovery process. The virulence of recovered cells was assessed by the ability to form plaques in HT-29 cell monolayers and by the ability to colonise mouse spleens. Although the cells were classified as avirulent when in the VBNC state, the virulence was recovered after resuscitation.VBNC / virulence / embryonated eggs / Listeria monocytogenes

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Viable but non-culturable forms of potentially pathogenic bacteria in water

Cited by 104 publications

References 41 publications

Houseflies: not simple mechanical vectors of enterohemorrhagic Escherichia coli O157:H7.

Houseflies: not simple mechanical vectors of enterohemorrhagic Escherichia coli O157:H7.

Salmonellae in the Environment

Avirulent Viable But Non Culturable cells ofListeria monocytogenesneed the presence of an embryo to be recovered in egg yolk and regain virulence after recovery

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