Analysis of the survival of H. pylori within a laboratory-based aquatic model system using molecular and classical techniques.
Despite the significance of Helicobacter pylori infection for man, its transmission is not clearly known. The human stomach is considered the reservoir of this pathogen, and one of the accepted routes is fecal-oral, in which water acts as a vector. However, although H. pylori epidemiology associates its transmission with water, only molecular and not cultural analysis detects the bacteria in water. This study was carried out to understand these data through studying the survival of H. pylori in a laboratory water model using cultural, morphological, and molecular methods. A mineral water system spiked with H. pylori and stored at 7 +/- 1 degrees C in the dark was analyzed by different methods over a period of 3 weeks. The total number of cells observed by DAPI staining and their DNA content remained constant over this study period. In contrast, cells could no longer be cultured after 5 days. Cell viability, which was determined via the LIVE/DEAD BacLight kit, decreased up to day 14, and at day 21 all cell membranes were damaged. In addition, a gradual conversion from spiral to coccal morphology occurred from day 3 onward. However, polymerase chain reaction (PCR) technique detected H. pylori DNA at day 21 and 3 months later. A study of the cell morphology of a young colony demonstrated the coexistence of bacilli and cocci. The results of this study show that H. pylori survives in water but loses its culturability and bacillar morphology rapidly, although it remains viable for longer periods and its DNA is still detectable much later. Thus, interpreting H. pylori's behavior in water differs according to the type of analysis. Consequently, we suggest that the presence of H. pylori infective cells is overestimated by PCR, whereas, in contrast, culture techniques underestimate it. Nevertheless, H. pylori should be considered a waterborne pathogen during its viable period, independently of its shape and culturability, as its presence in water may be risky for human health.
Queralt
Núria
N
Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.
Araujo
Rosa
R
D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis* / Q000302:isolation & purification; D016480:Helicobacter pylori / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification* / Q000648:ultrastructure; D006801:Humans; D007753:Laboratories; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning; D008900:Mineral Waters / Q000382:microbiology*; D016133:Polymerase Chain Reaction
D003470:Culture Media; D004269:DNA, Bacterial; D008900:Mineral Waters