Investigation of multidrug-resistant bacteria in dogs enrolled at animal-assisted therapy in a trauma and surgical emergency hospital

To the Editor—Animal-assisted activities, such as informal visitations and interactions through dog-assisted therapy (DAT), can promote well-being and improve the health of patients in hospitals. ¹ However, despite the significant benefits that DAT can provide, animals can harbor and transmit potential hazardous microorganisms, such as fungi, parasites, and multidrug-resistant (MDR) bacteria. ²

Few studies have investigated the risk of MDR bacteria in dogs involved in hospital DAT. Recently, some studies have shown the presence of opportunistic pathogens associated with nosocomial infections, which can be carried by dogs and transmitted to humans, including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp, extended-spectrum β-lactamase–producing Escherichia coli, and methicillin-resistant staphylococci. ^3,4 Moreover, Walther et al ⁵ point out that clinical outbreaks associated with these microorganisms are reported in the veterinary context, which can be related to the MDR transmission between animal to humans.

Due to the possibility of the MDR bacteria colonization in dogs enrolled at DAT that keep in contact with hospitalized individuals, we sought to detect the presence of MDR bacterial strains in nasal and rectal swab from dogs enrolled at DAT before and after patient visitation.

This transversal study approved by the institutional review board (animal ethics committee). It was conducted at Hospital Universitário Cajuru (HUC), an acute-care university hospital with 207 beds located in Curitiba, state of Paraná, in Southern Brazil. HUC is a referral center for trauma and surgical emergency, and in the first semester of 2020, 46% of the healthcare-associated infections were caused by MDR bacteria, with a density between 1.5 and 9.6 cases per 1,000 patient days.

Since 2014, the HUC has promoted DAT, in which dogs have visited hospitalized patients in the ward once each week. All dogs are housed in a veterinary clinic, receiving daily care, and assisted by a veterinarian. Before the visits, the dogs were cleaned with ethanol (70%). During the visit period, patients and professionals were instructed to sanitize their hands with 70% ethanol before and after contact with the animals, and all the visits were supervised by a veterinarian. After the visit, dogs were again cleaned with 70% ethanol. During 2018, 10 dogs were enrolled in DAT, and before entering the hospital and after the period of visitation, nasal and rectal swabs were collected by direct sterile swabbing (Stuart Agar Gel Medium, Copan-Transystem, Copan, Brescia, Italy) and were stored for microbiological analysis.

The samples were immediately subjected to microbiological analysis, in which the swabs were streaked in specific media and incubated at 37°C for 24 hours for MDR screening. The swabs were inoculated as follows: nasal swabs were screened for methicillin-resistant Staphylococcus aureus (MRSA), in which the swabs were streaked onto mannitol agar (Laborclin, Pinhais, Brazil). The characteristic yellow colonies identified in the agar plate were tested for coagulase and cefoxitin.

Rectal swabs were sampled to detect the presence of ESBL, Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), and vancomycin-resistant enterococci (VRE). To screen for resistant enterococci, suspected colonies were inoculated onto bile esculin agar supplemented with vancomycin. To screen for gram-negative bacilli, the swabs were streaked onto specific chromogenic agar for ESBL (which also selects KPC and NDM; Laborclin, Pinhais, Brazil). Suspicious colonies were subjected to phenotypic testing with antibiotic-impregnated discs with amoxicillin/clavulanate, cefepime, ceftriaxone, aztreonam, and ceftazidime (Laborclin, Pinhais, Brazil). A meropenem-impregnated disc (Laborclin, Pinhais, Brazil) for carbapenem resistance was also evaluated.

All samples from 10 dogs showed bacterial growth on mannitol, bile esculin, and chromogenic agar. However, none of the isolated colonies showed resistance profile for the tested antibiotics according to the 2018 CLSI standards. ⁶ This is the first study of this conducted in a Brazilian hospital. Despite the absence of MDR bacteria in our samples, this type of surveillance should be expanded, and all dogs enrolled in a DAT should be tested to avoid bacterial and resistance-gene dissemination, and to ensure the safety of the animals and patients.