Enterobacterales
animals is low and therefore transmission to, and carriage in dogs and cats is likely to be very uncommon. 26,27
Enterobacterales is an order of gram-negative bacterial rods comprising seven recognised families, including the family Enterobacteriaceae. 21 Enterobacteriaceae includes the genera Escherichia, Klebsiella, and Salmonella, with many species normal inhabitants of the gastrointestinal tract of mammals. These organisms may however cause opportunistic infections in susceptible patients or when spread to locations outside the gastrointestinal tract. Some Enterobacteriaceae (e.g. Salmonella sp., Shigella sp.) are primary enteric pathogens. Extended-spectrum beta-lactamase producing Enterobacterales (ESBL-E) • By virtue of their location, commensal gastrointestinal organisms are exposed to selection pressure from orally administered antimicrobials and are a potential source of resistance genes. A growing concern in veterinary and human medicine are organisms producing extended-spectrum beta- lactamases (ESBLs), enzymes which hydrolyse and render inactive third generation cephalosporins. As ESBL resistance is carried on a plasmid, this can be easily transferable to other species of Enterobacterales. Presence on plasmids allows for the accumulation of other resistance factors. Hence ESBL resistance is frequently associated with co-resistance to other classes of antimicrobials, including fluoroquinolones and aminoglycosides. • In humans the most common species carrying ESBL enzymes are E. coli, Klebsiella pneumoniae and Enterobacter cloacae. Presence of ESBL enzymes in Salmonella species is also a concern as this has considerable zoonotic potential. • ESBL-E are a very uncommon cause of disease in dogs and cats in Australia. 22 • Eating raw meat and recent antimicrobial treatment has been reported overseas as a risk factor for carriage of ESBL-E in dogs, 23,24 and a study of commercially available raw food diets for dogs in Sweden found E. coli in all tested samples (n=39), with ESBL isolated from 23%. 25 Owing to differences in antimicrobial prescribing and animal husbandry in Australia compared to other regions, the prevalence of ESBL-E in Australian production
Carbapenemase-producing Enterobacterales (CPE) • Carbapenems are beta-lactam antimicrobials frequently used as a last-line treatment for severe infections in human medicine. Consequently, they are classified as highly important antimicrobials. Carbapenemase-producing Enterobacterales (CPE) are of increasing concern worldwide as the presence of these enzymes may render the organism virtually untreatable with currently available antibiotics. Because of concern for spread, CPE incidence in human infection in Australia is reportable. • CPE have not been reported in dogs in Australia, and there is a single report of carbapenem resistant Salmonella enterica isolated from a systemically unwell cat and three cohabitating cats in the same facility. 28 The off-label use of carbapenems in dogs and cats is uncommon in Australia, with a review of over 4 million consultations, including almost 600,000 antimicrobial prescribing events failing to identify the use of this class of antimicrobial. 2 Despite this, CPE may develop in the absence of carbapenem use through co-selection of carbapenem-resistance associated with the use of other antimicrobials. • Human CPE infections are mostly associated with prolonged hospitalisation and underlying diseases. Infections with enzymes such as KPC can result in up to 50% mortality. Enzymes such as NDM and OXA-48 have become increasingly prevalent, especially in parts of South and East Asia. All patients who have been recently hospitalised overseas are screened on admission in Australia, in order to avoid transmission and potential outbreaks. • Occurrence in Australia is still relatively uncommon, with less than 1% prevalence in surveillance studies of blood-stream infections, 29 but some enzymes such as IMP-4 are locally endemic and have been found in environmental sources such as hospital drains and waste-water and in cats and wild birds in Australia. 28,30
ACAZAP RECOMMENDATIONS
• Good hand hygiene is essential following contact with animals, animal food or treats, food bowls, animal bedding and animal faeces. • Currently there is no known role of dogs and cats in transmission of CPE in Australia, however the possibility for human-to-animal transmission exists.
• Although the risk of ESBL-E in raw meat in Australia is very low, due to the risk of transmission of other potential pathogens (e.g. Campylobacter, Salmonella), it is recommended to avoid feeding raw meat diets to dogs and cats, or if fed, consider the potential for zoonotic infection through contact with the diet or the faeces of animals which have consumed the diet.
CONTENTS
12 Companion Animal Zoonoses Guidelines
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