The environment as a reservoir for non-culturable but infectious, antibiotic-resistant bacteria: a new risk for human health?

Abstract number: 1133_145

Lleo M., Pruzzo C., Signoretto C., Canepari P.

Human pathogens are frequently transmitted from person-to-person, directly or via vectors/vehicles, thus perpetuating their parasitic cycle. However, they are also released into the environment, for example with faeces, where they encounter adverse conditions (oligotrophy, direct sunlight, extreme temperatures and salinity) which prevent cell division. Under stressing conditions, human pathogens and components of the normal microflora do not necessarily die but might persist even for long periods of time (several months) in that they are capable of activating a survival strategy known as the viable but nonculturable (VBNC) state. When in this phase, bacteria lose their ability to form colonies on culture media but are still viable and capable of metabolic activity and gene expression and show a specific protein profile and cell wall modifications. Moreover, VBNC cells, which are capable of maintaining their pathogenic potential (adhesion to animal tissues, toxin synthesis), may be able to resume division on returning to favourable environmental conditions such as those encountered in the human gut after ingestion of contaminated water or foods. A significant amount of data on VBNC bacterial forms derives also from our studies conducted on a waterborne pathogen such as Vibrio cholerae whose role as a seawater reservoir involved in cholera epidemics has been definitively demonstrated. Recently, using a vancomycin resistant Enterococcus faecalis model, we have demonstrated that bacteria are capable of maintaining and expressing antibiotic resistance during the VBNC state and after resuming their divisional capability when permissive conditions are restored. On the basis of their characteristics, VBNC cells could therefore represent a potential risk for human health in that (i) they might constitute a reservoir of infectious and antibiotic-resistant bacterial forms involved in disease transmission and persistence, and (ii) they are undetectable with the standard culture methods. For this reason, for reliable evaluation of the microbiological quality of the environment is now mandatory to re-design the currently used procedures in order also to detect nonculturable bacteria.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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