Development of a MALDI-TOF MS model for differentiating haemorrhagic septicaemia-causing strains of Pasteurella multocida from other capsular groups.

Pasteurella multocida capsular types A, D, and F cause disease in many animal hosts, including bovine respiratory disease in cattle, which is one of the most globally significant animal diseases. Additionally, P. multocida capsular types B and E cause haemorrhagic septicaemia, a devastating disease primarily of cattle, water buffalo, and bison that develops rapidly with high mortality. Haemorrhagic septicaemia mostly occurs in developing countries and has potential to emerge elsewhere in the world. The diagnosis of haemorrhagic septicaemia currently requires recognition of compatible gross or histologic lesions and serotyping or molecular characterization of strains. In this study, we performed genomic characterization of 84 P. multocida strains, which were then used to develop and validate a matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) biomarker-based method for differentiating non-haemorrhagic septicaemia strains of P. multocida from haemorrhagic septicaemia-causing strains. Haemorrhagic septicaemia strain types B:2,5, E:2,5, and B:3,4 were used to maximize diversity. Three automated classification models were generated and then used to develop an assisted model, which utilized two peaks (6419 and 7729 m/z) to accurately differentiate non-haemorrhagic septicaemia-causing strains from haemorrhagic septicaemia-causing strains of P. multocida. The assisted model performed with 98.2 % accuracy for non-haemorrhagic septicaemia strains, 100 % accuracy for classic B:2,5 and E:2,5 strains, and 84.4 % accuracy for combined haemorrhagic septicaemia-causing strains (B:2,5, E:2,5, and B:3,4) with an overall accuracy of 96.9 %. Our results suggest that MALDI-TOF MS may be used to routinely screen P. multocida isolated from diagnostic cases for initial identification of haemorrhagic septicaemia-causing strains, and to determine whether additional characterizations are warranted.

Wild lagomorphs as potential sources of Francisella tularensis in an urban zoo: a case study.

A 9-y-old captive male Pallas' cat (Otocolobus manul) had a 1-mo history of worsening lameness and was euthanized. The animal was submitted to the North Dakota State University-Veterinary Diagnostic Laboratory for autopsy with differential diagnoses of suspected degenerative joint disease or neoplasia. Autopsy revealed icteric tissues and pinpoint foci in the liver, spleen, and all lung lobes. PCR testing was positive for Francisella tularensis, the causative agent of tularemia. Additional cases of tularemia were later identified in wild eastern cottontail rabbits found dead at the same urban zoo. Tularemia has been reported in captive non-human primates and rodent populations with one case linked to wild lagomorph exposure, which was likely the route of exposure in our Pallas' cat case. Tularemia is an occupational risk for zoo staff and laboratorians. Pest management and disease surveillance of wild lagomorph populations in zoos are important preventive measures.

A One Health perspective on the use of genotypic methods for antimicrobial resistance prediction.

Antimicrobial resistance is a global One Health concern with critical implications for the health of humans, animals, and the environment. Phenotypic methods of bacterial culture and antimicrobial susceptibility testing remain the gold standards for the detection of antimicrobial resistance and appropriate patient care; however, genotypic-based methods, such as PCR, whole genome sequencing, and metagenomic sequencing, for detection of genes conferring antimicrobial resistance are increasingly available without inclusion of appropriate standards for quality or interpretation. Misleading test results may lead to inappropriate antimicrobial treatment and, in turn, poor patient outcomes and the potential for increased incidence of antimicrobial resistance. This article explores the current landscape of clinical and methodological aspects of antimicrobial susceptibility testing and genotypic antimicrobial resistance test methods. Additionally, it describes the limitations associated with employing genotypic-based test methods in the management of veterinary patients from a One Health perspective. The companion Currents in One Health by Maddock et al, AJVR, March 2024, addresses current and future needs for veterinary antimicrobial resistance research.

Current state and future directions for veterinary antimicrobial resistance research.

Antimicrobial resistance (AMR) is a critical One Health concern with implications for human, animal, plant, and environmental health. Antimicrobial susceptibility testing (AST), antimicrobial resistance testing (ART), and surveillance practices must be harmonized across One Health sectors to ensure consistent detection and reporting practices. Veterinary diagnostic laboratory stewardship, clinical outcomes studies, and training for current and future generations of veterinarians and laboratorians are necessary to minimize the spread of AMR and move veterinary medicine forward into an age of better antimicrobial use practices. The purpose of this article is to describe current knowledge gaps present in the literature surrounding ART, AST, and clinical or surveillance applications of these methods and to suggest areas where AMR research can fill these knowledge gaps. The related Currents in One Health by Maddock et al, JAVMA, March 2024, addresses current limitations to the use of genotypic ART methods in clinical veterinary practice.

ß-Lactam resistance in veterinary ß-hemolytic Streptococcus species: Are we experiencing a public health or test method crisis?

ß-Hemolytic Streptococcus (BHS) species are important pathogens with both human and veterinary significance. In human medicine, BHS are considered universally susceptible to ß-lactams while BHS of veterinary origin have been reported with up to 8% ß-lactam resistance. Recently, veterinary diagnostic laboratories were made aware of significant variability of test method performance for BHS among laboratories. This article explores potential sources of error in antimicrobial susceptibility test performance and result interpretation that may have contributed to the unusual rates of resistance to ß-lactams observed in this bacterial species. In addition, potential impacts to research, clinical practice, surveillance, and public health will be discussed.

In vitro efficacy of 0.2% and 0.4% sodium oxychlorosene against meticillin-resistant Staphylococcus pseudintermedius.

BACKGROUND: There is a need for alternative topical therapies as a consequence of the increased prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) skin infections in dogs. Sodium oxychlorosene has been used as a topical antibacterial agent in human medicine since 1955. OBJECTIVES: To determine whether 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>3-log reduction) on MRSP strains isolated from canine skin infections. METHODS AND MATERIALS: A genetically heterogeneous collection of MRSP isolates from dogs was assembled from laboratories across the United States. Time-kill assays were performed with 0.2% and 0.4% sodium oxychlorosene on a 0.5 McFarland standard [approximately 108 colony-forming units (cfu/ml)] suspension of each strain. The average bacterial counts (cfu/ml) of each MRSP strain then were determined at 5, 10, 20 and 60 s after exposure to sodium oxychlorosene; cfu/ml data were converted to log10 scale to calculate microbial reduction. RESULTS: The average bacterial counts following exposure to the 0.2% solution at 5, 10, 20 and 60 s were 6.94 × 104 , 5.63 × 103 , 2.96 × 102 and 1.48 × 102  cfu/ml, respectively. For the 0.4% solution, the average bacterial count at 5 s was 2.12 × 103  cfu/ml. No bacterial growth was observed for any MRSP strain by 10 s. The greatest reduction in cfu/ml occurred within 5 s following exposure to each solution 3.4-log and 4.9-log reduction for 0.2% and 0.4%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>99.9% reduction) against MRSP in vitro. Further in vivo studies are necessary to determine whether it is an appropriate alternative therapy for canine pyoderma.