Starvation Survival and Viable but Nonculturable States in Aeromonas hydrophila

Abstract

The behavior of Aeromonas hydrophila stored at 4 degrees C and 25 degrees C in nutrient-poor filtered sterilized distilled water was investigated. At 4 degrees C, the A. hydrophila population declined below the detection level (0.1 cell mL(-1)) after 7 weeks, whereas the number of cells with intact membrane as determined by the LIVE/DEAD method decreased only by 1 log unit. Although, this response is reminiscent of the so-called VBNC state, the cells could not be resuscitated by an upshift to 25 degrees C. A mixture of rods with normal size and elongated cells was observed in this state. At 25 degrees C, viable cells and cells with intact membrane declined only by 0.8 log unit over the 10-week storage period, and thus A. hydrophila entered the classical starvation survival state. During this state, a mixture of rods and cocci was observed. Prestarvation at 25 degrees C for 24 h and especially 49 days delayed significantly the rate of entry into the VBNC state. However, stationary phase cells were not significantly more tolerant than exponential phase cells. No significant improvements in recovery yield were obtained on LB agar plates amended with catalase or sodium pyruvate. During cold incubation, high variability in responses was observed. Intermittent cryptic regrowth might be responsible for this variability in responses.

Behavior of an Aeromonas hydrophila aroA Live Vaccine in Water Microcosms

“…Because licensing regulations require assessing the risks associated with the release of genetically modified microorganisms, the persistence and behavior of mutant strains in natural environments need to be carefully studied. Several studies concerning the survival of A. hydrophila strains in aquatic environments, such as distilled water (44), mineral water (18,45,47), tap water (43), and seawater (40), have been published. Microcosms are often used in these studies, most of them applied to assess the health impact of the presence of motile Aeromonas species in drinking water, because the production of a wide range of virulence factors is a common feature of virulent strains (10,13,53,54,64).…”

“…Under adverse conditions, such as those present in some natural aquatic environments, A. hydrophila strains are able to enter a viable but nonculturable (VBNC) or an active nonculturable (ANC) state (40,44,75), from which they may be resuscitated under permissive conditions (40,75). A VBNC or an ANC state allows microorganisms long-term permanence in the environment and makes their isolation for diagnostic procedures difficult (9,31).…”

The effects of temperature, water activity and pH on the growth of Aeromonas hydrophila and on its subsequent survival in microcosm water

“…The results obtained show that the survival of the bacteria varies considerably depending on species (Brandi et al 1999), water-type (Kersters et al 1996;Brandi et al 1999;Croci et al . 2002;Mary et al 2001), temperature at incubation (Mary et al 2002) and interaction with other micro-organisms (Warburton et al 1994;Mary et al 2001;Messi et al 2002). Nevertheless, there are no reports concerning the effect of previous growth on the behaviour of this bacterium in water.…”

Inactivation Kinetics ofVibrio parahaemolyticuson Sand Shrimp(Metapenaeus ensis)by Cinnamaldehyde at 4°C

“…To support the hypothesis that the VBNC state is regulated by a genetic mechanism, an effective approach would be to isolate mutants that fail to enter the VBNC state; nevertheless, no such mutants have been identified [46]. The preservation procedure known to inhibit V. parahaemolyticus from entering VBNC state, the so-called starvation-induced maintenance of culturability 6 Journal of Food Quality (SIMC) effect [47], which has been demonstrated in several bacteria [48][49][50] has been investigated. Thirteen proteins, including the peroxiredoxin AhpC, were enhanced in the induction period or downregulated in prestarved cultures which inhibited the entry of exponential phase cells into the VBNC state.…”