Isolation of shiga toxin-producing Escherichia coli from a South American camelid (Lama guanicoe) with diarrhea

Diarrheagenic Escherichia coli isolates from neonatal alpacas mainly display F17 fimbriae adhesion gene

Neonatal domestic South American Camelid llamas and alpacas suffer from an enteric disease complex characterized by abdominal distention, lethargy, dehydration, and eventual fatal septicemia. Analysis of rectal swabs from neonatal alpacas suffering clinical diarrheas has constantly isolated Escherichia coli, mainly the EPEC and EHEC pathotypes. The present communication reports the results of molecular analysis of 226 E. coli strains from neonatal alpaca rectal swabs. The isolates were initially tested by multiple PCR, to identify E. coli virulence genes eae, bfp, Lt, Stx1, Stx2, sta, stab, and lt genes and a similar test to detect F4, F5, F6, F17, and F41fimbriae adhesin genes. Forty-two of the 226 (18.5%) isolates tested positive for at least one pathogenic gene, 25 of the 42 were classified as EPEC (3 positives for only eae and 22 for both eae and bfp) and the remaining 17 were classified as EHEC. Twenty-four (57%) of the 42 isolates tested positive to F17 adhesin while one was positive for both F6 and F17.

Recent Updates on Outbreaks of Shiga Toxin-Producing Escherichia coli and Its Potential Reservoirs

Following infection with certain strains of Shiga toxin-producing Escherichia coli (STEC), particularly enterohemorrhagic ones, patients are at elevated risk for developing life-threatening extraintestinal complications, such as acute renal failure. Hence, these bacteria represent a public health concern in both developed and developing countries. Shiga toxins (Stxs) expressed by STEC are highly cytotoxic class II ribosome-inactivating proteins and primary virulence factors responsible for major clinical signs of Stx-mediated pathogenesis, including bloody diarrhea, hemolytic uremic syndrome (HUS), and neurological complications. Ruminant animals are thought to serve as critical environmental reservoirs of Stx-producing Escherichia coli (STEC), but other emerging or arising reservoirs of the toxin-producing bacteria have been overlooked. In particular, a number of new animal species from wildlife and aquaculture industries have recently been identified as unexpected reservoir or spillover hosts of STEC. Here, we summarize recent findings about reservoirs of STEC and review outbreaks of these bacteria both within and outside the United States. A better understanding of environmental transmission to humans will facilitate the development of novel strategies for preventing zoonotic STEC infection.

Animal Reservoirs of Shiga Toxin-Producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) strains have been detected in a wide diversity of mammals, birds, fish, and several insects. Carriage by most animals is asymptomatic, thus allowing for dissemination of the bacterium in the environment without detection. Replication of the organism may occur in the gastrointestinal tract of some animals, notably ruminants. Carriage may also be passive or transient, without significant amplification of bacterial numbers while in the animal host. Animals may be classified as reservoir species, spillover hosts, or dead-end hosts. This classification is based on the animal's ability to (i) transmit STEC to other animal species and (ii) maintain STEC infection in the absence of continuous exposure. Animal reservoirs are able to maintain STEC infections in the absence of continuous STEC exposure and transmit infection to other species. Spillover hosts, although capable of transmitting STEC to other animals, are unable to maintain infection in the absence of repeated exposure. The large diversity of reservoir and spillover host species and the survival of the organism in environmental niches result in complex pathways of transmission that are difficult to interrupt.

Molecular serotyping of Escherichia coli O26:H11

Serotyping is the foundation of pathogenic Escherichia coli diagnostics; however, few laboratories have this capacity. We developed a molecular serotyping protocol that targets, genetically, the same somatic and flagellar antigens of E. coli O26:H11 used in traditional serotyping. It correctly serotypes strains untypeable by traditional methods, affording primary laboratories serotyping capabilities.