Antimicrobial stewardship in small animal veterinary practice: from theory to practice.

Despite the increasing recognition of the critical role for antimicrobial stewardship in preventing the spread of multidrug-resistant bacteria, examples of effective antimicrobial stewardship programs are rare in small animal veterinary practice. This article highlights the basic requirements for establishing stewardship programs at the clinic level. The authors provide suggestions and approaches to overcome constraints and to move from theoretic concepts toward implementation of effective antimicrobial stewardship programs in small animal clinics.

Assessment of attenuated Salmonella vaccine strains in controlling experimental Salmonella Typhimurium infection in chickens.

Salmonella hold considerable promise as vaccine delivery vectors for heterologous antigens in chickens. Such vaccines have the potential additional benefit of also controlling Salmonella infection in immunized birds. As a way of selecting attenuated strains with optimal immunogenic potential as antigen delivery vectors, this study screened 20 novel Salmonella Typhimurium vaccine strains, differing in mutations associated with delayed antigen synthesis and delayed attenuation, for their efficacy in controlling colonization by virulent Salmonella Typhimurium, as well as for their persistence in the intestine and the spleen. Marked differences were observed between strains in these characteristics, which provide the basis for selection for further study as vaccine vectors.

La bactérie Salmonella est considérée comme un vecteur vaccinal prometteur pour la livraison d'antigènes hétérologues chez les poulets. De tels vaccins ont le potentiel bénéfique supplémentaire de limiter les infections par Salmonella chez les oiseaux immunisés. Comme moyen de sélectionner les souches atténuées avec le potentiel immunogène optimal comme vecteur de livraison d'antigènes, la présente étude a examiné 20 souches vaccinales nouvelles de Salmonella Typhimurium, qui différaient en mutation associées avec une synthèse antigénique retardée et une atténuation retardée, pour leur efficacité à limiter la colonisation par du Salmonella Typhimurium virulent, ainsi que pour leur persistance dans l'intestin et la rate. Des différences marquées furent observées entre les souches pour ces caractéristiques, fournissant ainsi des éléments de sélection pour des études ultérieures comme vecteurs vaccinal.(Traduit par Docteur Serge Messier).

Development of a live, attenuated, potential vaccine strain of R. equi expressing vapA and the virR operon, and virulence assessment in the mouse.

Pneumonia caused by Rhodococcus equi remains a significant problem in foals. The objective of this study was to develop a safe and efficacious attenuated strain of R. equi for eventual use in oral immunization of foals. The approach involved expression of vapA in a live, virulence plasmid-negative, strain of R. equi (strain 103-). PCR-amplified fragments of the vapA gene, with and without the upstream genes virR, orf5, vapH, orf7 and orf8 (orf4-8), were cloned into a shuttle vector pNBV1. These plasmids, named pAW48A and pAWVapA respectively, were electroporated into strain 103-. The presence of the recombinant vectors in the attenuated strain (103-) and the integrity of the inserted genes were confirmed, and both constructs expressed VapA. The virulence of the two strains was compared to that of wild type R. equi 103+ and negative controls by their intravenous inoculation into mice, followed by examination of liver clearance 4 days later. Mice inoculated with R. equi 103-, 103-/pAWVapA and 103-/pNBV1 completely cleared infection, whereas strain 103-/pAW48A persisted in 47% of mice.

Assessment of 2 Salmonella enterica serovar Typhimurium-based vaccines against necrotic enteritis in reducing colonization of chickens by Salmonella serovars of different serogroups.

This study assessed the protective efficacy of oral vaccination with 2 experimental attenuated Salmonella Typhimurium-vectored vaccines for necrotic enteritis in protecting chickens against intestinal colonization by common serovars of Salmonella belonging to the 4 major serogroups affecting chickens. Birds were vaccinated orally with 1 × 108 colony-forming units (CFU) of 1 of the vaccine strains χ9241 and χ9352, which express a plasmid-encoded partial recombinant hypothetical protein gene (tHP) of Clostridium perfringens, at days 1 and 7 of age, and then were challenged at 14 d of age with 106 CFU of Salmonella serovars Anatum, Enteritidis, Heidelberg, Kentucky, or Typhimurium (representative serovars of serogroups B, C, D, and E). Birds were necropsied at 4 wk of age, and samples were collected to determine reduction in tissue and intestinal colonization. The chickens vaccinated with χ9241-tHP showed reduced colonization by Salmonella Enteritidis (serogroup D) and by Salmonella Heidelberg and Salmonella Typhimurium (serogroup B) compared with the control birds. No reduction in colonization was observed in the chickens vaccinated with χ9352-tHP. There was an association between the efficacy of these vaccine strains in protecting against necrotic enteritis, assessed on an earlier occasion, and their efficacy in protecting against Salmonella colonization. Thus, the choice of an attenuated Salmonella Typhimurium vaccine vector for delivery of heterologous antigens to chickens should be based partly on the vaccine's value in protecting against colonization by serovars within serogroups B and D. Such vectors would have the additional benefit of reducing colonization of important Salmonella serovars.

Assessment of laboratory and biosafety practices associated with bacterial culture in veterinary clinics.

OBJECTIVE: To investigate bacterial culture practices in veterinary clinics, with an emphasis on laboratory biosafety and on quality of laboratory practices. DESIGN: Survey-based prospective study. SAMPLE POPULATION: 166 veterinarians. PROCEDURES: Veterinarians were recruited through the Veterinary Information Network (an Internet-based network restricted to veterinary personnel). All Network-registered veterinarians were eligible to participate. A standardized questionnaire regarding bacterial culture practices in veterinary clinics was completed electronically by study participants. RESULTS: 720 veterinarians completed the survey; 166 (23%) indicated that bacterial culture was performed in his or her clinic. Clinic practices ranged from preliminary aerobic bacterial culture only with submission of isolates to a diagnostic laboratory for further testing (93/160 [58%]) to bacterial culture, identification, and antimicrobial susceptibility testing (19/160 [12%]). Most commonly, urine samples were cultured (151/162 [93%] clinics). Several problematic practices were identified regarding quality and quality control, including inadequate facilities, equipment, supervision, interpretation of data, and culture methods. Biosafety infractions were also common, including inadequate laboratory location, lack of biosafety protocols, and dangerous disposal practices. Ninety-four percent of respondents stated that continuing education regarding culture practices and laboratory safety would be useful. CONCLUSIONS AND CLINICAL RELEVANCE: Data confirmed that bacterial culture was commonly performed in clinics, but that major deficiencies in laboratory methods were widespread. These could result in negative effects on testing quality and increased risk of laboratory-acquired infections among clinic personnel. Veterinary practices in which bacterial cultures are performed must ensure that adequate equipment, facilities, personnel, and training are provided to enable accurate and safe sample testing.

Mutation and virulence assessment of chromosomal genes of Rhodococcus equi 103.

Rhodococcus equi can cause severe or fatal pneumonia in foals as well as in immunocompromised animals and humans. Its ability to persist in macrophages is fundamental to how it causes disease, but the basis of this is poorly understood. To examine further the general application of a recently developed system of targeted gene mutation and to assess the importance of different genes in resistance to innate immune defenses, we disrupted the genes encoding high-temperature requirement A (htrA), nitrate reductase (narG), peptidase D (pepD), phosphoribosylaminoimidazole-succinocarboxamide synthase (purC), and superoxide dismutase (sodC) in strain 103 of R. equi using a double-crossover homologous recombination approach. Virulence testing by clearance after intravenous injection in mice showed that the htrA and narG mutants were fully attenuated, the purC and sodC mutants were unchanged, and the pepD mutant was slightly attenuated. Complementation with the pREM shuttle plasmid restored the virulence of the htrA and pepD mutants but not that of the narG mutant. A single-crossover mutation approach was simpler and faster than the double-crossover homologous recombination technique and was used to obtain mutations in 6 other genes potentially involved in virulence (clpB, fadD8, fbpB, glnA1, regX3, and sigF). These mutants were not attenuated in the mouse clearance assay. We were not able to obtain mutants for genesfurA, galE, and sigE using the single-crossover mutation approach. In summary, the targeted-mutation system had general applicability but was not always completely successful, perhaps because some genes are essential under the growth conditions used or because the success of mutation depends on the target genes.