Spatiotemporal Analysis of Acid Adaptation-Mediated Vibrio cholerae Hyperinfectivity

Abstract

Acid adaptation has previously been shown to increase the infectivity of Vibrio cholerae in the infant mouse model. To better understand this phenomenon, we monitored the spatial distribution and temporal changes in the ratios of acid-adapted cells to unadapted V. cholerae cells in the small intestine, as well as the timing of virulence factor expression. We found that the competitive advantage afforded by acid adaptation does not become manifest until greater than 3 h postinfection; thus, acid adaptation does not increase V. cholerae passage through the gastric acid barrier. Additionally, acid-adapted and unadapted V. cholerae cells colonize the same sections of the small intestine and show similar kinetics of transcriptional induction of the virulence genes tcpA and ctxA. These studies suggest that the increased infectivity of acid-adapted V. cholerae is due to a more rapid onset of multiplication and/or to an increased multiplication rate within the infant mouse intestine.For oral route pathogens, such as Salmonella enterica serovar Typhimurium, Escherichia coli, and Vibrio cholerae, the ability to survive passage through the human gastric acid barrier is a crucial component of the bacterial life cycle. This ability is believed to be linked to an adaptive stress response to acid known as the acid tolerance response (ATR) (7, 9, 11). It is also possible that the ATR may enhance survival and growth within the intestinal tract after passage through the stomach. Analysis of V. cholerae has revealed a number of genes that play crucial roles in ATR (8-10). Additionally it was shown that ATR increases bacterial infectivity: specifically, acidadapted V. cholerae outcompeted unadapted V. cholerae by 1 order of magnitude after 24 h of coinfection in the infant mouse but did not outcompete the unadapted organism during in vitro growth (9). Mechanistically, this could be explained by increased survival during transit through the stomach, increased fitness within the small intestine, or a combination of the two. In this work, we investigate the nature of ATR-induced V. cholerae hyperinfectivity and observe a growth advantage of adapted versus unadapted V. cholerae cells at middle to late stages of a 24-h infection. In addition, we evaluate the primary sites of colonization of acid-adapted V. cholerae compared to those of unadapted cells and measure the effects of acid adaptation on the kinetics of transcriptional induction of two critical virulence factors, cholera toxin (CT) and toxincoregulated pilus (TCP).Gastric survival profile. To determine whether hyperinfectivity of acid-adapted V. cholerae was due to an increased ability to survive transit through the gastric barrier, we analyzed the temporal population dynamics during competition assays. In this assay, differentially marked acid-adapted and unadapted strains were coinfected into 5-day-old CD-1 infant mice as previously described (9). Briefly, overnight cultures of isogenic lacZ ϩ and lacZ mutant V. cholerae strains AC51 and AC168 (9) were subcultured to fresh Lu...

The LysR-type regulator LeuO regulates the acid tolerance response in Vibrio cholerae

“…In addition, pre-activation of the V. cholerae acid tolerance response has been shown to impart a competitive advantage for colonization of the infant mouse intestine relative to unadapted cells (Merrell & Camilli, 1999). Taken together these results suggest that the acid tolerance response may play a crucial role in both the initial infection with V. cholerae and the subsequent development of hyper-infectivity that has been observed in human and animal-shed V. cholerae (Alam et al, 2005;Angelichio et al, 2004;). …”

Staying Alive: Vibrio cholerae ’s Cycle of Environmental Survival, Transmission, and Dissemination

“…Interestingly, acid-adaptation does not appear to increase V. cholerae survival during passage through the infant mouse stomach (191). Instead, it has been proposed that acid-adapted cells have enhanced colonization because they begin multiplying earlier and/or have a faster multiplication rate compared to unadapted cells.…”

Intranasal Inoculation of Mice withYersinia pseudotuberculosisCauses a Lethal Lung Infection That Is Dependent onYersiniaOuter Proteins andPhoP

“…Data are reported as the number of CFU/g of organ for lung, liver, spleen, and trachea; number of CFU/ml of blood; and number of CFU/organ for the lymph nodes and nasopharynx as the small size of the organs and the association of lymph nodes with connective tissue made determination of weights inaccurate. Homogenization of tissues was accomplished using a variable-speed tissue tearor (Biospec Products Inc.) using established methods described previously (2,13,49). Samples were blended until the solution appeared homogeneous, which occurred after 10 to 45 s of homogenization, depending on the tissue.…”