Brenda C. Love

Streptococcal Infection in Dogs A Retrospective Study of 393 Cases

Streptococcus spp are opportunistic pathogens that normally reside in the upper respiratory, intestinal, lower urinary, and genital tracts but can cause localized infection or septicemia in dogs of all ages. A retrospective study of streptococcal infection in 393 dogs was conducted to identify the species of Streptococcus isolated, determine demographics of affected dogs, and characterize the disease processes associated with infection. The major streptococcal species isolated were S canis (88 cases, 22.4%), S dysgalactiae ssp equisimilis (13, 3.3%), and S equi ssp zooepidemicus (4, 1.0%). Sex was not a risk factor (P > .30). Fetuses and neonates were more likely to have streptococcal infection than were other age groups (P < .001). Streptococcal septicemia was considered an important cause of abortion and neonatal death and was isolated from all samples submitted for aerobic culture from dogs in that age group. There was a seasonal trend, with dogs more likely to have streptococcal infection in summer months. In dogs for which a disease process was identified, streptococcal infection was associated with dermatitis (29 dogs), pneumonia (24 dogs), adult septicemia (13 dogs), and fetal/neonatal septicemia leading to abortion or neonatal death (16 dogs). Identification of other clinically significant bacterial, viral, fungal, and parasitic organisms was common (267 of 393 dogs, 68%), especially in dogs with dermatitis or pneumonia. Infection with Streptococcus spp should be considered in the differential diagnosis in cases of abortion, septicemia, dermatitis, and pneumonia in dogs. Clinical significance of isolation of streptococcal organisms should be interpreted in context of clinical signs and pathologic findings.

A Retrospective Study of Mortality in Pennsylvania Captive White-Tailed Deer (Odocoileus Virginianus): 2000–2003

The postmortem records of 160 white-tailed deer (Odocoileus virginianus) submitted for necropsy examination from 59 separate Pennsylvania captive deer farms over a 3.5-year period were reviewed to determine the primary cause of death of each animal. The most common causes of death were bronchopneumonia (39 cases), enterocolitis (30 cases), malnutrition (13 cases), and trauma (11 cases). Other causes of mortality included severe gastrointestinal parasitism (6 cases), cellulitis with septicemia (5 cases), degenerative myopathy (4 cases), ruminal acidosis (4 cases), and nephritis (4 cases). The cause of death was undetermined in 13 of the 160 animals. Arcanobacterium pyogenes (19 cases), Fusobacterium necrophorum (10 cases), Escherichia coli (7 cases), and Mannheimia haemolytica (4 cases) were the most commonly isolated bacteria from the pneumonic lungs. Bacterial agents associated with enterocolitis included Clostridium perfringens (15 cases), E. coli (12 cases), and Mycobacterium avium subsp. paratuberculosis (2 cases). The majority (52.2%) of the death loss in white-tailed deer of known ages occurred in animals 1 year of age or less, with 46.2% of the bronchopneumonia cases and 50.0% of the enterocolitis cases occurring during this time period. Cases of degenerative myopathy, myocardial degeneration, hepatic necrosis, meningoencephalitis, peritonitis, and urolithiasis considered severe enough to be the primary cause of death appeared early in life, affecting deer 6 months of age or less in all cases. In conclusion, bronchopneumonia, enterocolitis, malnutrition, and trauma were considered the most common causes of death in confined white-tailed deer in this study.

Comparison of Five Culture Methods for Salmonella Isolation from Swine Fecal Samples of Known Infection Status

The current study was conducted to evaluate 5 bacteriologic culture methods (methods 1, 2, 3, 4, and 5) for recovery of Salmonella enterica from swine feces, both for sensitivity of detection (ability to recover Salmonella from a positive sample) and for specificity (not to inadvertently identify an organism as a Salmonella species in a negative sample). Fifty-six negative samples and 46 positive samples were processed using each of the 5 methods, which differed primarily in the combinations of enrichment media used. All negative samples were negative for Salmonella when cultured by all 5 methods (100% specificity). Two of the methods (methods 1 and 4) resulted in the recovery of significantly less (P < 0.05) Salmonella when compared with the remaining 3 methods (methods 2, 3, and 5). No one method was successful in recovering Salmonella from all positive samples, although recovery with method 2 was statistically similar to the total number of positive samples analyzed (42 vs. 46 Salmonella-positive samples, P > 0.05). This study shows that culture methods differ significantly in their performance regarding the isolation of Salmonella from swine fecal samples.

Effect of transport enrichment medium, transport time, and growth medium on the detection of Campylobacter fetus subsp. venerealis.

The combination of medium and growth conditions, including transport enrichment medium (TEM), transport time, TEM incubation time, and growth medium, that best support Campylobacter fetus subsp. venerealis while inhibiting contaminants was studied. The 3 TEMs evaluated, Weybridge, Cary-Blair, and 0.85% saline solution, were inoculated with preputial smegma spiked with C. fetus subsp. venerealis and held in the laboratory for 4 or 24 hours before inoculation onto growth medium. The effect of overnight incubation at 37 C of the TEM was also evaluated. Median scores of C. fetus subsp. venerealis growth and microbial contaminant inhibition were compared within TEM, transport time, overnight incubation, and growth medium groups using the Mann–Whitney U-test and the Kruskal–Wallis test. The proportion of samples with any growth or contamination within each group was also compared using the chi-square test. Results suggest that the growth of C. fetus subsp. venerealis was influenced by 3 of the 4 criteria evaluated. Weybridge TEM more effectively maintained the organism than did either Cary–Blair or 0.85% saline solution (P < 0.001). Transport time of 4 hours rather than 24 hours (P < 0.001) and avoiding overnight incubation of TEM at 37 C (P < 0.001) were associated with improved growth. Significant differences were not identified among growth media; however, Skirrow Campylobacter agar appeared to yield slightly better growth than did either blood agar or Greenbriar Plus agar. Contaminant growth was also influenced by 3 of the 4 variables. Weybridge TEM inhibited contaminant growth more effectively than did either Cary–Blair or 0.85% saline solution (P < 0.001). Transport time was not associated with contaminant growth. Eliminating overnight incubation of TEM reduced contamination (P < 0.01). Skirrow agar was preferred to both blood agar and Greenbriar Plus agar for suppression of contaminants on solid medium (P < 0.001). These results suggest that the detection of C. fetus subsp. venerealis is enhanced when preputial smegma samples arrive at the diagnostic laboratory within 4 hours after inoculation into Weybridge TEM and are transferred to Skirrow agar the same day they arrive in the laboratory.

Genetic and Phenotypic Characterization of the blaCMY Gene from Escherichia coli and Salmonella enterica Isolated from Food-Producing Animals, Humans, the Environment, and Retail Meat

The bla(CMY-2) family of the ampC beta-lactamase genes confer broad-spectrum resistance to beta-lactam antimicrobials, including ceftriaxone and ceftiofur, as well as to beta-lactamase inhibitors, such as clavulanic acid. Organisms with the bla(CMY-2) phenotype have been recovered from the environment and from retail meat products, posing a potential public health risk. The objectives of this study were to sequence the bla(CMY-2) gene from Escherichia coli and Salmonella enterica from multiple sources that had a reduced susceptibility to ceftriaxone and to determine the effect of observed mutations in the bla(CMY-2) gene on the antimicrobial resistance phenotype (spectrum and minimum inhibitory concentration/susceptibility patterns) of the isolates. The bla(CMY-2) genes from 52 bacterial isolates were sequenced for this study. Sixty-two percent (32/52) were E. coli and 38% (20/52) were S. enterica. Of the 32 E. coli isolates, 30 were found to carry a beta-lactamase gene that was 100% homologous to bla(CMY-2). One of the E. coli isolates was found to contain a gene that was 90% homologous to bla(CMY-2). This isolate also had lower minimum inhibitory concentrations to tetracyclines, streptomycin, and the sulfonamide antimicrobials than are commonly expected for isolates containing the bla(CMY-2). Of the 20 genes obtained from Salmonella isolates, 8 (40%) were found to be homologous to bla(CMY-2), with no altered susceptibility phenotypes observed.

Comparison of antemortem antimicrobial treatment regimens to antimicrobial susceptibility patterns of postmortem lung isolates from feedlot cattle with bronchopneumonia

A retrospective study was performed to compare the treatment regimens in feedlot cattle that died with bovine respiratory disease (BRD) to the antimicrobial susceptibility patterns of the microorganisms isolated from lungs. Forty-three cattle submitted by the Willard Sparks Beef Research Center (WSBRC) to the Oklahoma Animal Disease Diagnostic Laboratory for postmortem examination during 2007 had bronchopneumonia (acute = 16, subacute = 5, or chronic = 22). Lungs from cattle were cultured aerobically (40 cattle) and for Mycoplasma spp. (34 cattle). Susceptibility panels were performed. At least 1 BRD pathogen (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Mycoplasma bovis, or Arcanobacterium pyogenes) was isolated from 39 cattle, and 77% (30/39) had multiple organisms recovered. Mycoplasmal infections were common (25/34) and a major component of mixed infections (24/25). The majority (60%) of the M. haemolytica, P. multocida, and H. somni isolates were resistant to tetracycline. Most of the H. somni isolates (67%) were susceptible to tilmicosin (Ti), enrofloxacin (En), ceftiofur (Ce), and florfenicol, despite extensive treatment with Ti, En, and Ce (75% of isolates were from cattle that received each antimicrobial once). Most of the M. haemolytica (65%) and P. multocida (79%) isolates were susceptible to En and Ce, despite antemortem treatment of cattle with these antimicrobials. Hence, the current study reports a discrepancy between the antemortem treatment of clinical BRD and the susceptibility patterns of the bacteria isolated from lungs postmortem. Based on these findings, factors other than antimicrobial resistance are playing a role in the death of feedlot cattle with BRD.

Parasite age-intensity relationships in red-spotted newts: Does immune memory influence salamander disease dynamics?

Acquired immune memory in vertebrates influences transmission and persistence of infections, with consequences for parasite dynamics at both the individual and population levels. The potential impact of acquired immunity is of particular interest for salamanders, whose acquired immune systems are thought to be less effective than those of frogs and other tetrapods. One way to examine the importance of acquired immunity to parasite dynamics at the population level is by examining the relationship between host age and parasite infection intensity. Acquired immunity reduces infection rates in older animals, causing decreased parasite intensity in older age classes and leading to curvilinear age-intensity relationships for persistent parasites and convex age-intensity relationships for transient parasites. We used age-intensity relationships to look for the signature of acquired immunity for 12 parasite taxa of red-spotted newts (Notophthalmus viridescens), using data from a 2-year parasitological survey of six newt populations. We estimated ages from snout-vent length (SVL) based on the relationship between SVL and skeletochronologically-derived ages in a subset of newts. We found evidence of acquired immunity to two parasite taxa, bacterial pathogens and the protist Amphibiocystidium viridescens, whose convex age-intensity relationships could not be easily explained by alternative mechanisms. Our results suggest that the acquired immune response of newts is sufficient to influence the dynamics of at least some parasites.

Disseminated protothecosis diagnosed by evaluation of CSF in a dog

A 5-year-old female spayed Shetland Sheepdog Mix dog was evaluated for a history of recent seizure activity, progressive hind limb ataxia, polyuria, and polydipsia and no history of gastrointestinal signs. Physical examination findings included conscious proprioceptive deficits, ataxia, and anterior uveitis along with a hypermature cataract in the right eye. Results of a CBC, serum biochemical profile, urinalysis, and computed tomography scan of the brain were unremarkable. Cerebrospinal fluid (CSF) analysis revealed marked eosinophilic pleocytosis and rare organisms consistent with Prototheca spp within neutrophils and macrophages. On postmortem histologic examination, mononuclear inflammation and numerous intralesional algal organisms, similar to those seen on the cytologic preparation of CSF, were found in the brain, eyes, kidneys, and heart. Abnormalities were not detected on gross and histologic examination of the gastrointestinal tract. Cultures of CSF and subdural/olfactory bulb, but not intestinal tract, yielded growth of Prototheca spp, and PCR analysis and DNA sequencing confirmed the organism as Prototheca zopfii genotype 2. We have reported a rare case of disseminated protothecosis that was diagnosed by evaluation of CSF in a dog presented with neurologic signs and no overt enteric disease. Protothecosis should be considered as a rare cause of seizures, even in the absence of obvious enteric signs, and should be included in the differential diagnosis of eosinophilic pleocytosis.

Mortality in Pennsylvania captive elk (Cervus elaphus): 1998-2006.

The necropsy records of 65 elk ranging from 1 day to 13 1/2 years of age were reviewed to determine the primary cause of death of each animal. The animal carcasses were submitted from 22 separate Pennsylvania elk farms over an approximately 8-year period. The most common causes of mortality in animals in which the cause of death was determined were gastrointestinal parasitism (21 cases), pneumonia (7 cases), enterocolitis (5 cases), malnutrition (5 cases), and rumenitis/acidosis (5 cases). The cause of death was undetermined in 4 of the 65 elk. Nematode organisms (20 cases) were the primary parasites identified in cases of mortality owing to gastrointestinal parasitism. Arcanobacterium pyogenes (3 cases), Escherichia coli (3 cases), and Streptococcus sp. (2 cases) were the most commonly isolated bacteria from the lung in the cases of pneumonia. Fungal organisms, consistent with Aspergillus sp. were present histologically within the pulmonary lesions in 5 cases. Bacterial agents associated with enterocolitis included Clostridium perfringens (2 cases), E. coli (1 case), Salmonella Newport (1 case) and Salmonella Thompson (1 case). The majority (56.3%) of the death loss in elk of known ages occurred in animals 1 year of age or less, with 71.4% of the gastrointestinal parasitism, 60.0% of the malnutrition, 60.0% of the enterocolitis, and 57.1% of the pneumonia cases occurring in animals within this age range. In conclusion, gastrointestinal parasitism, pneumonia, malnutrition, enterocolitis and rumenitis acidosis were considered the most common causes of death in captive elk in this study.

Candida peritonitis in dogs: report of 5 cases.

Candida peritonitis is reported in people and is associated with significant morbidity and mortality compared with sterile or bacterial peritonitis. Recognized predisposing risk factors include peritoneal dialysis, hollow viscous organ perforation, abdominal surgery, inflamed intestinal mucosa, antimicrobial administration, and immunosuppression. In this report, we describe 5 cases of dogs with peritonitis complicated by Candida spp; 3 dogs with C albicans, one dog with C albicans and C glabrata, and one dog with C glabrata only. The 3 dogs with C albicans peritonitis presented with duodenal perforation due to NSAID therapy, intestinal resection and anastomosis following postspay-surgery dehiscence, and intestinal foreign body removal. The 2 dogs with C glabrata peritonitis had undergone cholecystectomy due to gall bladder rupture and dehiscence of intestinal biopsy removal sites following exploratory laparatomy. In all cases, initial diagnosis of fungal peritonitis was made via cytologic examination of peritoneal effusions, which revealed marked pyogranulomatous inflammation with numerous 3-8 μm oval, deeply basophilic yeast organisms with thin clear capsules noted within phagocytes and extracellularly. In addition, germ tube formation, hyphae, and pseudohyphae were rarely seen in some of the cases with pure C albicans. Identity of the organisms was determined by culture in all cases and confirmed by PCR in 3 cases. Candida spp. are commensals normally inhabiting the alimentary, the upper respiratory, and the lower urogenital tracts of mammals. They are opportunistic pathogens that can invade and colonize tissue when a patient is immune-compromised or there is disruption of the mucosal barrier. Candida peritonitis should be considered in patients with peritoneal contamination with gastrointestinal or biliary contents.