Detection of Leptospira kirschneri in a short-beaked common dolphin (Delphinus delphis delphis) stranded off the coast of southern California, USA.

BACKGROUND: Pathogenic Leptospira species are globally important zoonotic pathogens capable of infecting a wide range of host species. In marine mammals, reports of Leptospira have predominantly been in pinnipeds, with isolated reports of infections in cetaceans. CASE PRESENTATION: On 28 June 2021, a 150.5 cm long female, short-beaked common dolphin (Delphinus delphis delphis) stranded alive on the coast of southern California and subsequently died. Gross necropsy revealed multifocal cortical pallor within the reniculi of the kidney, and lymphoplasmacytic tubulointerstitial nephritis was observed histologically. Immunohistochemistry confirmed Leptospira infection, and PCR followed by lfb1 gene amplicon sequencing suggested that the infecting organism was L.kirschneri. Leptospira DNA capture and enrichment allowed for whole-genome sequencing to be conducted. Phylogenetic analyses confirmed the causative agent was a previously undescribed, divergent lineage of L.kirschneri. CONCLUSIONS: We report the first detection of pathogenic Leptospira in a short-beaked common dolphin, and the first detection in any cetacean in the northeastern Pacific Ocean. Renal lesions were consistent with leptospirosis in other host species, including marine mammals, and were the most significant lesions detected overall, suggesting leptospirosis as the likely cause of death. We identified the cause of the infection as L.kirschneri, a species detected only once before in a marine mammal - a northern elephant seal (Mirounga angustirostris) of the northeastern Pacific. These findings raise questions about the mechanism of transmission, given the obligate marine lifestyle of cetaceans (in contrast to pinnipeds, which spend time on land) and the commonly accepted view that Leptospira are quickly killed by salt water. They also raise important questions regarding the source of infection, and whether it arose from transmission among marine mammals or from terrestrial-to-marine spillover. Moving forward, surveillance and sampling must be expanded to better understand the extent to which Leptospira infections occur in the marine ecosystem and possible epidemiological linkages between and among marine and terrestrial host species. Generating Leptospira genomes from different host species will yield crucial information about possible transmission links, and our study highlights the power of new techniques such as DNA enrichment to illuminate the complex ecology of this important zoonotic pathogen.

Genomics accurately predicts antimicrobial resistance in Staphylococcus pseudintermedius collected as part of Vet-LIRN resistance monitoring.

Whole-genome sequencing (WGS) has changed our understanding of bacterial pathogens, aiding outbreak investigations and advancing our knowledge of their genetic features. However, there has been limited use of genomics to understand antimicrobial resistance of veterinary pathogens, which would help identify emerging resistance mechanisms and track their spread. The objectives of this study were to evaluate the correlation between resistance genotypes and phenotypes for Staphylococcus pseudintermedius, a major pathogen of companion animals, by comparing broth microdilution antimicrobial susceptibility testing and WGS. From 2017-2019, we conducted antimicrobial susceptibility testing and WGS on S. pseudintermedius isolates collected from dogs in the United States as a part of the Veterinary Laboratory Investigation and Response Network (Vet-LIRN) antimicrobial resistance monitoring program. Across thirteen antimicrobials in nine classes, resistance genotypes correlated with clinical resistance phenotypes 98.4 % of the time among a collection of 592 isolates. Our findings represent isolates from diverse lineages based on phylogenetic analyses, and these strong correlations are comparable to those from studies of several human pathogens such as Staphylococcus aureus and Salmonella enterica. We uncovered some important findings, including that 32.3 % of isolates had the mecA gene, which correlated with oxacillin resistance 97.0 % of the time. We also identified a novel rpoB mutation likely encoding rifampin resistance. These results show the value in using WGS to assess antimicrobial resistance in veterinary pathogens and to reveal putative new mechanisms of resistance.

Identification of Pythium insidiosum complex by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

PURPOSE: Pythiosis is an infection of humans and other animals caused by the fungal-like pathogen Pythium insidiosum. This pathogen causes life-threatening infection in the infected hosts. Culture, histopathology, serology and molecular tools are used to diagnose its infections. Successful management of pythiosis is directly linked to an early diagnosis. Thus, a rapid identification of putative cultures developing submerged sparsely septate hyphae is of extreme importance. However, few laboratories are familiar with the culture identification of this unique pathogen and its differential diagnosis with similar filamentous fungi. METHODOLOGY: We have evaluated the use of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) on 53 isolates of P. insidiosum collected from cases of human and animal pythiosis in the USA and around the world. To assess the specificity of the approach, 18 pathogenic and saprotrophic filamentous fungal and fungal-like microbes were also tested. RESULTS: MALDI-TOF in-house spectra correctly identified the 53 P. insidiosum isolates (score range 1.93-2.51). MALDI-TOF based identification within P. insidiosum isolates showed protein spectra variation between geographical diverse isolates. A mass spectrometry approach was able to discriminate P. insidiosum from the 18 filamentous fungal and fungal-like microbes in this study, including four Pythium spp. and Phytopythium litorale plant pathogenic species. CONCLUSION: The data showed MALDI-TOF could be used for the accurate and rapid culture identification of P. insidiosum in the clinical laboratory.

First report of emerging zoonotic pathogen Wohlfahrtiimonas chitiniclastica in the United States.

Wohlfahrtiimonas chitiniclastica is an emerging human pathogen that has been identified as the cause of septicemia in humans in Europe and South America. Here we report the first case of a unique disease manifestation of Wohlfahrtiimonas chitiniclastica-induced bacterial septicemia secondary to wound myiasis in a deer in Michigan in the United States.