Positive associations matter: Microbial relationships drive tick microbiome composition.

Untangling how factors such as environment, host, associations among bacterial species and dispersal predict microbial composition is a fundamental challenge. In this study, we use complementary machine-learning approaches to quantify the relative role of these factors in shaping microbiome variation of the blacklegged tick Ixodes scapularis. I. scapularis is the most important vector for Borrelia burgdorferi (the causative agent for Lyme disease) in the U.S. as well as a range of other important zoonotic pathogens. Yet the relative role of the interactions between pathogens and symbionts compared to other ecological forces is unknown. We found that positive associations between microbes where the occurrence of one microbe increases the probability of observing another, including between both pathogens and symbionts, was by far the most important factor shaping the tick microbiome. Microclimate and host factors played an important role for a subset of the tick microbiome including Borrelia (Borreliella) and Ralstonia, but for the majority of microbes, environmental and host variables were poor predictors at a regional scale. This study provides new hypotheses on how pathogens and symbionts might interact within tick species, as well as valuable predictions for how some taxa may respond to changing climate.

The impact of urine collection method on canine urinary microbiota detection: a cross-sectional study.

BACKGROUND: The urinary tract harbors unique microbial communities that play important roles in urogenital health and disease. Dogs naturally suffer from several of the same urological disorders as humans (e.g., urinary tract infections, neoplasia, urolithiasis) and represent a valuable translational model for studying the role of urinary microbiota in various disease states. Urine collection technique represents a critical component of urinary microbiota research study design. However, the impact of collection method on the characterization of the canine urinary microbiota remains unknown. Therefore, the objective of this study was to determine whether urine collection technique alters the microbial populations detected in canine urine samples. Urine was collected from asymptomatic dogs by both cystocentesis and midstream voiding. Microbial DNA was isolated from each sample and submitted for amplicon sequencing of the V4 region of the bacterial 16 S rRNA gene, followed by analyses to compare microbial diversity and composition between urine collection techniques. RESULTS: Samples collected via midstream voiding exhibited significantly higher sequence read counts (P = .036) and observed richness (P = .0024) than cystocentesis urine. Bray Curtis and Unweighted UniFrac measures of beta diversity showed distinct differences in microbial composition by collection method (P = .0050, R2 = 0.06 and P = .010, R2 = 0.07, respectively). Seven taxa were identified as differentially abundant between groups. Pasteurellaceae, Haemophilus, Friedmanniella, two variants of Streptococcus, and Fusobacterium were over-represented in voided urine, while a greater abundance of Burkholderia-Caballeronia-Paraburkholderia characterized cystocentesis samples. Analyses were performed at five thresholds for minimum sequence depth and using three data normalization strategies to validate results; patterns of alpha and beta diversity remained consistent regardless of minimum read count requirements or normalization method. CONCLUSION: Microbial composition differs in canine urine samples collected via cystocentesis as compared to those collected via midstream voiding. Future researchers should select a single urine collection method based on the biological question of interest when designing canine urinary microbiota studies. Additionally, the authors suggest caution when interpreting results across studies that did not utilize identical urine collection methods.

Characterization of the urogenital microbiome in Miniature Schnauzers with and without calcium oxalate urolithiasis.

BACKGROUND: Calcium oxalate (CaOx) uroliths are common in dogs. Humans with CaOx urolithiasis exhibit alterations of the urinary and urogenital microbiomes that might mediate urolith formation. Detection of urogenital microbes associated with CaOx in dogs could inform disease pathophysiology. OBJECTIVE: To identify compositional differences in the urogenital microbiome of Miniature Schnauzers with and without CaOx uroliths. ANIMALS: Nineteen midstream, voided urine samples from Miniature Schnauzers with (n = 9) and without (n = 10) a history of CaOx urolithiasis. METHODS: Analytical cross-sectional study. Microbial DNA was extracted from previously frozen urine samples and sequenced for the bacterial 16S rRNA V3-V4 hypervariable regions. Diversity and composition of microbial populations were compared between urolith formers and controls. RESULTS: Alpha and beta diversity measures were similar between groups. Five individual bacterial taxa differed in abundance (indicator values >0.5 and P < .05): Acinetobacter, 2 Geobacillus variants, and Hydrogenophaga were overrepresented in the urine of urolith formers, and Sphingopyxis was overrepresented in controls. Two distinct subtypes of urine microbial composition were observed based on beta diversity measures, independent of urolith status, and other clinical variables. CONCLUSIONS AND CLINICAL IMPORTANCE: Although we did not detect a difference in the overall urogenital microbial composition between groups, observed differences in individual bacterial taxa might be clinically relevant. For example, Acinetobacter was overrepresented in urolith formers and is associated with CaOx urolithiasis in humans. Two unique clusters of the microbiome were identified, independent of urolith status, which may represent distinct urotypes present in Miniature Schnauzers.

Evaluation of various sample sources for the cytologic diagnosis of Cytauxzoon felis.

BACKGROUND: Cytauxzoon felis is a life-threatening protozoan disease of cats. Identification of schizont-laden macrophages is a point-of-care diagnostic test for acute cytauxzoonosis. HYPOTHESIS/OBJECTIVES: The primary objective determined cytologic agreement between sample types to diagnose acute cytauxzoonosis. The secondary objective evaluated novices' ability to identify cytauxzoon organisms in blood films and tissue aspirates. ANIMALS: Thirty-eight cats with suspected acute cytauxzoonosis and 5 controls examined postmortem. METHODS: Cases were prospectively submitted and collected. Blood film, lymph node, and splenic aspirates were blindly reviewed for sample quality, presence of schizont-laden macrophages, and agreement between sample types. A subset of cases and controls were evaluated by 12 blinded novice observers to determine sensitivity and specificity for identifying organisms in various sample types. RESULTS: Acute cytauxzoonosis diagnosis was made on at least 1 sample type in 28/38 cats. Schizont-laden macrophages were seen on 33% (10/30) of blood films, 56% (19/34) lymph node aspirates, 77% (26/34) splenic aspirates. Schizont-laden macrophages were more likely seen on splenic than lymph node aspirates (McNemar's, P = .03) or blood film (McNemar's, P = <.001). Novice observers were more likely to agree with experts when identifying schizont-laden macrophages in splenic aspirates (sensitivity = 77.1%, specificity = 94.4%) versus lymph node aspirates (sensitivity = 52.8%, specificity = 96.4%) or blood films (sensitivity = 41.7%, specificity = 96.9%). CONCLUSIONS AND CLINICAL IMPORTANCE: Schizont-laden macrophages are most frequently identified in spleen, even by novice observers. If the diagnosis of acute cytauxzoonosis cannot be confirmed via blood film, then splenic, followed by peripheral lymph node aspirates can be considered.

BASELINE PHYSIOLOGIC AND HEMATOLOGIC HEALTH IN WILD-CAUGHT MUSKRATS (ONDATRA ZIBETHICUS) FROM A NEAR-PRISTINE ECOSYSTEM IN NORTHERN MINNESOTA.

Muskrat (Ondatra zibethicus) populations show long-term and widespread declines across North America, necessitating research into potential mechanistic explanations, including population health. Previous research established reference hematology values, a proxy of individual health, of muskrats occurring in highly modified ecosystems. However, our knowledge of hematology metrics in muskrat populations occurring in more natural ecosystems is limited. We measured several hematological parameters of wild-caught muskrats (n = 73) in the Greater Voyageurs Ecosystem in northern Minnesota in 2018-2019 to establish baseline muskrat health in a relatively intact, near-pristine ecosystem. Additionally, we measured rectal temperature and heart and respiratory rates and collected whole blood for complete blood cell count assessment. We established baseline physiologic and hematologic reference ranges for the population and describe variations between total white blood cells, nucleated cell differentials, and basic erythron and platelet estimates and demonstrate methods of estimation to be poor proxies for more standardized counting methods. Our results establish a baseline to compare muskrat health assessments for populations affected by landscape change or in decline.

Monitoring of large B-cell lymphoma and T-zone lymphoma in a dog via flow cytometry.

A 12-y-old, castrated male Pomeranian dog was presented because of mandibular lymph node (LN) enlargement. Physical examination and a complete blood count revealed generalized lymphadenopathy and moderate lymphocytosis. Fine-needle aspirate cytology revealed expansion of medium lymphocytes in the right mandibular LN and expansion of large lymphocytes in the left popliteal LN. Flow cytometry identified 2 aberrant lymphocyte populations in both LNs, namely a CD5+CD45- T-cell population, and a large CD21+ B-cell population. Flow cytometry of the peripheral blood revealed an identical population of aberrant CD45- T cells. The patient was diagnosed with concurrent T-zone lymphoma and leukemia, and B-cell lymphoma. Multi-agent chemotherapy was instituted, and serial clinical and flow cytometric analysis revealed complete remission of the neoplastic B cells, but persistence of the neoplastic T cells and persistent lymphadenopathy. This case affirms the diagnostic value of flow cytometry and reveals a unique limitation of the RECIST criteria.

Characterization of the urinary microbiome in healthy dogs.

The urinary bladder in healthy dogs has dogmatically been considered free of bacteria. This study used culture independent techniques to characterize the healthy canine urinary microbiota. Urine samples collected by antepubic cystocentesis from dogs without urinary infection were used for DNA extraction. Genital tract and rectal samples were collected simultaneously from the same dogs. The V4 hypervariable region of the 16S rRNA bacterial gene was amplified and compared against Greengenes database for OTU assignment and relative abundance for urine, genital, and rectal samples. After excluding 4 dogs with cultivable bacteria, samples from 10 male (M; 1 intact) and 10 female (F) spayed dogs remained. All samples provided adequate genetic material for analysis. Four taxa (Pseudomonas sp., Acinetobacter sp., Sphingobium sp. and Bradyrhizobiaceae) dominated the urinary microbiota in all dogs of both sexes. These taxa were also detected in the genital swabs of both sexes, while the rectal microbiota differed substantially from the other sample sites. Principal component (PC) analysis of PC1 through PC3 showed overlap of urinary and genital microbiota and a clear separation of rectal swabs from the other sample sites along PC1, which explained 44.94% variation. Surprisingly, the urinary microbiota (mean # OTU 92.6 F, 90.2 M) was significantly richer than the genital (67.8 F, 66.6 M) or rectal microbiota (68.3 F, 71.2 M) (p < 0.0001), with no difference between sexes at any sample site. The canine urinary bladder is not a sterile environment and possesses its own unique and diverse microbiota compared to the rectal and genital microbiota. There was no difference between the sexes at any microbiota sample site (urine, genital, and rectal). The predominant bacterial genus for either sex in the urine and genital tracts was Pseudomonas sp.

Evaluation of Fecal Microbiota Transfer as Treatment for Postweaning Diarrhea in Research-Colony Puppies.

Frequently just prior to or at weaning (approximate age, 6 to 8 wk), puppies in research settings often develop diarrheal disease, which may be due, in part, to an immature and unstable intestinal microbiota that is permissive to opportunistic pathogens. The overall objective of this study was to assess whether fecal microbiota transfer (FMT) increased the transmission of a stable maternal microbiota to pups and decreased the incidence of postweaning diarrhea. Puppies were designated by litter as treated (FMT) or sham-treated. The FMT group received fecal inoculum orally for 5 consecutive days during weaning (at 6 to 8 wk of age). Diarrhea was evaluated according to a published scoring system for 11 d during the weaning period. Fresh feces were collected from dams and puppies at 3 d before weaning and 3, 10, and 24 d after weaning for analysis of the fecal microbiota by using 16S rRNA amplicon sequencing. The composition of fecal inoculum refrigerated at 3 to 5 °C was stable for at least 5 d. No diarrhea was reported in either group during the study period, making comparison of treated and control groups problematic. However, 16S rRNA gene analysis revealed microbial variability across time in both groups. Therefore, although the fecal microbiota of neither group of puppies mirrored the dam at any of the designated time points, the data provided fundamental and novel information regarding the dynamic maturation process of the fecal microbiota of puppies after weaning.