Influence of the age and sex of human hosts on the distribution of Escherichia coli ECOR groups and virulence traits

Abstract

Escherichia coli were isolated from the faeces of 266 individuals living in the Canberra region of Australia. The isolates were characterized for their ECOR group membership (A, B1, B2 or D) and for the presence of 29 virulence-associated traits. Overall, 19?5 % of the strains were members of group A, 12?4 % B1, 45?1 % B2 and 22?9 % D. The frequency with which strains belonging to the four ECOR groups were observed varied with the age and sex of the hosts from which they were isolated. In males, the probability of isolating A or D strains increased with host age, whilst the probability of detecting a group B2 strain declined. In females, the probability of recovering A or B2 strains increased with increasing host age and there was a concomitant decline in the likelihood of isolating B1 or D strains. Of the 29 virulence-associated traits examined, 24 were detected in more than one strain. The likelihood of detecting most traits varied with a strain's ECOR membership, with the exception of afa/draBC, astA, cvaC, eaeA, iss and iutA, for which there was no statistically significant evidence of an association with ECOR group. The frequency with which fimH, iha, eaeA, iroN, hlyD, iss, ompT and K1 were detected in a strain depended on the age or sex of the host from which the strain was isolated. In group B2 strains many of the virulence traits were non-randomly associated, with some co-occurring in a strain less often than expected by chance, whilst others were co-associated. In 17 cases, the extent to which two virulence traits were co-associated was found to depend on host sex and age. The results of this study suggest that the morphological, physiological and dietary differences that occur among human individuals of different sex or age may influence the distribution of E. coli genotypes.

Phylogenetic Grouping of Dominant Fecal Escherichia coli Isolates from Healthy Males and Females in Al-Kut/Wasit Province/Iraq

“…Similar results were obtained by others [25,26] who found that sex and age factors had no effect on distribution of phylogroups. Whereas Gordon et al [27] found that in males the probability of isolating A or D strains increased with host age, whilst the probability of detecting a group B2 strain declined, while in females the probability of recovering A or B2 strains increased with increasing host age and there was a concomitant decline in the likelihood of isolating B1 or D strains. The reason for these differences may lie in that Gordon et al [27] had used fecal isolates from patients suffering from gastroenteritis, whereas, our isolates were from healthy volunteers who were not aware of any symptoms at the time of sampling.…”

“…Whereas Gordon et al [27] found that in males the probability of isolating A or D strains increased with host age, whilst the probability of detecting a group B2 strain declined, while in females the probability of recovering A or B2 strains increased with increasing host age and there was a concomitant decline in the likelihood of isolating B1 or D strains. The reason for these differences may lie in that Gordon et al [27] had used fecal isolates from patients suffering from gastroenteritis, whereas, our isolates were from healthy volunteers who were not aware of any symptoms at the time of sampling. Also these researchers' study included a wider age range (0-80 years), while our study included only young ages (18- Table 3: Phylogenetic distribution of virulence genes among fecal E. coli isolates from healthy males and females.…”

Effect of diet and gut dynamics on the establishment and persistence of Escherichia coli

“…The relative abundances of the main phylogroups of E. coli have been shown to vary with body mass and diet in mammals (Gordon & Cowling, 2003, Escobar-Páramo et al, 2006, with host age and sex in humans (Gordon et al, 2005), and with geographical locality in humans (Tenaillon et al, 2010).…”

“…Strains of the various phylogroups differ in their phenotypic and genotypic characteristics, in their ecological niches, as well as in their propensity to cause disease (Tenaillon et al, 2010). Strains of the various phylogroups are non-randomly distributed with respect to host species in non-human mammals (Gordon & Cowling, 2003;Carlos et al, 2010), and within humans are nonrandomly distributed with respect to host locality (Tenaillon et al, 2010) and the age and sex of the host (Gordon et al, 2005).…”

Evolution of colicin BM plasmids: the loss of the colicin B activity gene

“…The strains used in this study were from two existing E. coli collections. The first collection consists of 685 isolates from Australian reptiles, birds and mammals (Gordon & Cowling, 2003), and the second consists of 619 clinical and faecal isolates taken from humans living in Australia (Gordon et al, 2005). All isolates had been previously assayed for a mitomycin C-inducible colicin phenotype, as described by Gordon et al (1998), and PCR-screened for 11 colicins (B, M, Ia, Ib, E1, E2, E6, E7, K, A, D) and seven microcins (M, L, V, C7, H47, B17, J25) .…”