The strain-specific dynamics ofEscherichia coliO157:H7 faecal shedding in cattle post inoculation

Abstract

This study reports analysis of faecal shedding dynamics in cattle for three Escherichia coli O157:H7 (ECO157) strains (S1, S2 and S3) of different genotype and ecological history, using experimental inoculation data. The three strains were compared for their shedding frequency and level of ECO157 in faeces. A multistate Markov chain model was used to compare shedding patterns of S1 and S2. Strains S1 and S2 were detected seven to eight times more often and at 104 larger levels than strain S3. Strains S1 and S2 had similar frequencies and levels of shedding. However, the total time spent in the shedding state during colonization was on average four times longer for S1 (15 days) compared to S2 (4 days). These results indicate that an ECO157 strain effect on the frequency, level, pattern and the duration of faecal shedding may need to be considered in control of ECO157 in the cattle reservoir.

Phenotypic and Genotypic Characterization of Escherichia coli Isolated from Untreated Surface Waters

“…Therefore, the presence of E. coli alonemay no longer represent recent fecal contamination and instead, may indicate the persistence of some strains in the environment. Future studies using longitudinal monitoring [29, 30] and microbial source tracking [31-33] might help shed more light on the persistence and origin, respectively, of E. coli at the sites surveyed in our study. Nevertheless, E. coli in surface waters is a public health concern, and our data showed that the isolates from different surface water sources possess different phenotypic and genotypic traits (Tables 3 , 4 , and 6 ; Fig.…”

Transmission ofEscherichia coliO157:H7 in cattle is influenced by the level of environmental contamination

“…by bacteriological culture of RAMS: the steers were considered infectious if they were shedding at least one of the three inoculated strains. The three inoculated strains were FRIK47, FRIK1641 and FRIK2533, which have been described in previous studies [ 22 , 24 ]. Briefly, the three strains have different genotypes [ 27 ] (e.g.…”

“…The length of 30 days was chosen based on the expectation that the duration of ECO157 infection will not exceed 30 days [ 30 ]. Shedding of ECO157 in cattle is intermittent in nature [ 22 ], and so we adopted a frequency of sampling every other day, which was considered frequent enough to capture the intermittent shedding behaviour and was logistically feasible.…”

“…The infection status for each steer on each of the 15 sampling days was determined under the following assumptions that reflected the intermittent shedding pattern of ECO157 by the infected animals as reported in Gautam et al . [ 22 ]: (i) an animal testing positive was considered infectious ( I ), (ii) an animal testing negative could be classified either as latent ( L ) or susceptible ( S ) depending on the timing and the number of consecutive samples that were test-negative. If an animal was negative on ⩽4 consecutive samplings (i.e.…”

“…However, there are two major problems with the transmission rates reported in these two studies: (i) they did not consider how the level of environmental contamination with the bacterium may influence transmission, which is important given that ECO157 is spread by the faecal–oral route and (ii) they did not consider the possibility of a difference in transmission among strains of ECO157. A recent, experimental inoculation study has highlighted the strain-specific differences in the probability of colonization post-inoculation and in the faecal shedding pattern of colonized cattle [ 22 ]. Given that different strains of ECO157 have different host colonization abilities and shedding patterns in cattle, it is likely that transmission dynamics and the transmission rate will also vary between strains of ECO157.…”