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Topic:Microbiology
Microbiology and horses explores the interactions between microorganisms and equine hosts, focusing on the role of bacteria, viruses, fungi, and other microbes in horse health and disease. This field examines the microbial flora present in various equine environments, including the gastrointestinal tract, skin, and respiratory system, and investigates how these microorganisms influence equine physiology and pathology. Research in this area includes studies on microbial infections that affect horses, the development of antimicrobial resistance, and the impact of probiotics and prebiotics on equine health. This page compiles peer-reviewed research studies and scholarly articles that investigate the diversity, dynamics, and implications of microbial communities in horses, as well as the strategies for managing microbial-related diseases.
Broad range 16S rRNA gene PCR compared to bacterial culture to confirm presumed synovial infection in horses. The objectives of the present study were to evaluate the accuracy of broad range 16S rRNA gene PCR compared to bacterial culture for the detection of synovial infection in horses. The study included 57 synovial fluid samples from horses with presumed synovial infection and a control group consisting of 31 synovial fluid samples originating from clinically normal horses and horses with aseptic synovial inflammation. All samples were analysed by 16S PCR with reverse line blot (RLB) hybridisation. Synovial fluid samples were cultured using conventional agar plate methods (APM) and/or blood cultur...
Effect of a silicone-containing dressing on exuberant granulation tissue formation and wound repair in horses. To determine the effect of a silicone dressing on the rate and quality of repair of limb wounds and compare microvascular occlusion and apoptosis in wounds treated with the silicone dressing and those treated with a conventional dressing in horses. Methods: 5 horses. Methods: Horses received two 6.25-cm2 wounds on each metacarpus. Ten wounds were treated with a silicone dressing; the other 10 were treated with a control dressing. Quality of repair and wound size were evaluated at each bandage change. Time to healing and the number of excisions of exuberant granulation tissue were recorded. Bio...
Regulated expression of the beta2-toxin gene (cpb2) in Clostridium perfringens type a isolates from horses with gastrointestinal diseases. Recent epidemiological studies suggested that cpb2-positive Clostridium perfringens isolates are associated with gastrointestinal (GI) diseases in horses. These putative relationships, indicated by PCR genotyping, were tested in the present study by further genotyping and phenotyping of 23 cpb2-positive C. perfringens isolates from horses with GI disease (referred to hereafter as horse GI disease isolates). Our beta2-toxin (CPB2) Western blot analyses demonstrated that all of the tested isolates were unable to produce detectable levels of CPB2. However, Southern blot and nucleotide sequencing ...
Establishment of cloned Anaplasma phagocytophilum and analysis of p44 gene conversion within an infected horse and infected SCID mice. Diverse p44 alleles at the p44 expression locus (p44Es) encoding surface-exposed major membrane proteins, P44s, of Anaplasma phagocytophilum were hypothesized to be garnered by recombination to enact antigenic variation. However, this hypothesis has not been proven so far, due to inability to clone this obligate intragranulocytic rickettsia. To define the p44E recombination, we developed a novel method to clone A. phagocytophilum. This isogenic cloned population containing a defined p44E was used to infect a naive horse and severe combined immunodeficiency (SCID) mice. During a 58-day infectio...
Fructooligosaccharide supplementation in the yearling horse: effects on fecal pH, microbial content, and volatile fatty acid concentrations. Short-chain fructooligosaccharides (FOS) were supplemented to the diets of nine quarter horses ranging in age from 489 to 539 d with initial BW averaging 400.6 +/- 21.2 kg. The objectives of this study were to determine the effects of dietary FOS on the fecal responses in terms of pH, the microbial population, and VFA concentrations. The horses were used in a 3 x 3 replicated Latin square design, fed according to NRC requirements, and their individual diets were supplemented with no FOS (CON), 8 g of FOS/d (LOW), or 24 g of FOS/d (HIGH) over three 10-d feeding periods. On the last 3 d of each ...
The genetic diversity of lactic acid producing bacteria in the equine gastrointestinal tract. Seventy-two lactic acid producing bacterial isolates (excluding streptococci) were cultured from the gastrointestinal tract of six horses. Two of the horses were orally dosed with raftilose to induce lactic acidosis and laminitis while the remaining four were maintained on a roughage diet. Near complete 16S rDNA was amplified by PCR from the genomic DNA of each isolate. Following RFLP analysis with the restriction enzymes MboI, HhaI and HinfI, the PCR products from the 18 isolates that produced L- and/or D-lactate were subsequently cloned and sequenced. DNA sequence analysis indicated that the...
Evaluation of a real-time quantitative polymerase chain reaction assay for detection and quantitation of virulent Rhodococcus equi. To evaluate a real-time quantitative polymerase chain reaction (QPCR) assay in the detection and quantitation of virulent Rhodococcus equi. Methods: 1 virulent, 2 intermediately virulent, and 2 avirulent strains of R. equi and 16 isolates of bacteria genetically related to R. equi. Methods: The QPCR assay was evaluated for detection and quantitation of the virulence-associated gene (vapA) of R. equi in pure culture and in samples of tracheobronchial fluid, which were inoculated with known numbers of virulent R. equi. Results were compared with those derived via quantitative microbial culture a...
Changes in bacterial and fungal ocular flora of clinically normal horses following experimental application of topical antimicrobial or antimicrobial-corticosteroid ophthalmic preparations. To determine effects of topical antimicrobial and antimicrobial-corticosteroid preparations on the ocular flora of horses. animals: 40 horses. Methods: One eye was treated 3 times daily for 2 weeks with one of the following ointments: (1) neomycin-bacitracin-polymyxin B, (2) 0.6% prednisolone-0.3% gentamicin, (3) neomycin-polymyxin B-0.05% dexamethasone, or (4) treated (artificial tears) control. Contralateral eyes of treated control eyes served as untreated control eyes. Corneal and conjunctival specimens for bacterial and fungal cultures were collected prior to initiation of treatment, after...
Host distributions of uncultivated fecal Bacteroidales bacteria reveal genetic markers for fecal source identification. The purpose of this study was to examine host distribution patterns among fecal bacteria in the order Bacteroidales, with the goal of using endemic sequences as markers for fecal source identification in aquatic environments. We analyzed Bacteroidales 16S rRNA gene sequences from the feces of eight hosts: human, bovine, pig, horse, dog, cat, gull, and elk. Recovered sequences did not match database sequences, indicating high levels of uncultivated diversity. The analysis revealed both endemic and cosmopolitan distributions among the eight hosts. Ruminant, pig, and horse sequences tended to for...
Bacterial isolates and antimicrobial susceptibilities in equine bacterial ulcerative keratitis (1993–2004). Bacterial ulcerative keratitis is a common and often vision-threatening problem in horses. Emerging bacterial resistance to commonly used topical antibiotics has been demonstrated. Previous antibiotic use may alter the antimicrobial susceptibility of bacterial isolates. Objective: To document aerobic bacterial isolates and associated bacterial susceptibilities from horses with ulcerative keratitis treated at the University of Tennessee between January 1993 and May 2004 and determine whether prior antibiotic therapy affected antimicrobial susceptibility of the isolates. Methods: Medical records...
Fungal isolation and identification in 21 cases of guttural pouch mycosis in horses (1998-2002). This aetiological study of guttural pouch mycosis (GPM) in the horse was based on the retrospective study of 21 horses brought into the National Veterinary School of Lyon (France) between 1998 and 2002. Biopsies were taken from the lesions caused by GPM during endoscopic examination. In 87% of the cases, direct examination gave positive results, whereas 43% of the cultures were found to be negative. The main fungi observed were Aspergillus fumigatus (in three cases), A. versicolor (in two cases, together with other fungi), and A. nidulans and A. niger (one case each). In six cases, the Aspergi...
Ribotyping of Burkholderia mallei isolates. In this study, the subspecies differentiation of 25 isolates of Burkholderia mallei was attempted based on their ribotype polymorphisms. The isolates were from human and equine infections that occurred at various times around the world. DNA samples from each isolate were digested separately with PstI and EcoRI enzymes and probed with an Escherichia coli-derived 18-mer rDNA sequence to identify diagnostic fragments. Seventeen distinct ribotypes were identified from the combined data obtained with the two restriction enzymes. The results demonstrate the general utility of ribotyping for the subs...
Microbiologic and pathologic findings in an epidemic of equine pericarditis. During the spring and summer of 2001 and in association with the mare reproductive loss syndrome, 22 terminal and 12 clinical cases of equine pericarditis were diagnosed in central Kentucky. Actinobacillus species were the principal isolates from 8 of 10 nontreated, terminally affected and 3 of 10 clinically affected horses. Enterococcus faecalis and Streptococcus zooepidemicus were cultured from the remaining 2 nontreated terminal cases. No viruses were isolated in tissue culture. Nucleic acid of equine herpesvirus-2 was detected in pericardial and tracheal wash fluids of 3 and 1 individuals,...
Histology and ultrastructure of the equine lingual tonsil. I. Crypt epithelium and associated structures. The microstructural and ultrastructural features of the equine lingual tonsil were studied in five young horses. Located at the root of the tongue it presented an irregular surface with rounded elevations, numerous folds and crypts. Stratified squamous non-keratinized epithelium lining its outer surface was modified by heavy infiltration of lymphoid cells to form reticular epithelium within the crypt. The latter implies a role in initiating and maintaining immune responses to incoming infectious agents and antigens. Lamellated structures resembling Hassall's corpuscle were observed towards the...
A fractal analysis of pathogen detection by biosensors. A fractal analysis is presented for the detection of pathogens such as Franscisela tularensis, Yersinia pestis (the bacterium that causes plague), Bacillus anthracis, Venezuelan equine encephalitis (VEE) virus, Vavcinia virus, and Escherichia coli using a cellular analysis and notification of antigens risks and yields (CANARY) biosensor [T.H. Rider, M.S. Petrovic, F.E. Nargi, J.D Harper, E.D. Schwoebel, R.H. Mathews, D.J. Blanchard, L.T Bortolin, A.M. Young, J. Chen, M.A. Hollis, A cell-based sensor for rapid identification of pathogens, Science 301 (2003, 11 July) 213-215, T.H. Rider, M.S. Pe...
Multiplex polymerase chain reaction for identification and differentiation of Streptococcus equi subsp. zooepidemicus and Streptococcus equi subsp. equi. The closely related streptococcal species Streptococcus equi subsp. zooepidemicus and S. equi subsp. equi were identified by polymerase chain reaction using oligonucleotide primers designed according to species-specific parts of the superoxide dismutase A encoding gene sodA. A further differentiation of both subspecies could be performed by amplification of the genes seeH and seeI encoding the exotoxins SeeH and SeeI, respectively, which could be detected for S. equi subsp. equi but not for S. equi subsp. zooepidemicus. A further simplification of the identification and differentiation of both...
A cross-sectional study of epizootic lymphangitis in cart-mules in western Ethiopia. A cross-sectional study was conducted to determine the prevalence of epizootic lymphangitis (EL) in 309 cart-mules (cart-pulling mules) in Bako and Ejaji towns, Western Ethiopia using clinical and microbiological examinations, between November 2002 and April 2003. The overall prevalence was 21% (CI=16.6-26%). The clinical, histological and mycological characteristics of EL in a cart-mule were similar with those in a horse. There was significant (chi2=133.5, P=0.001) association between tick infestation and EL lesions in study cart-mules. Amblyoma coherence and Boophilus genera were the ticks c...
Identification of a novel collagen-like protein, SclC, in Streptococcus equi using signal sequence phage display. Strangles is a serious disease in horses caused by Streptococcus equi subspecies equi. In this study, genes encoding putative extracellular proteins in this subspecies have been identified using signal sequence phage display. Among these, one showed similarities to the SclB protein, a member of the collagen-like proteins of Streptococcus pyogenes. The novel gene denoted sclC encodes a protein, SclC, of 302 amino acids, containing typical features found in cell wall-anchored proteins in Gram-positive bacteria. Based on similarities to the S. pyogenes collagen-like proteins the mature SclC prote...
The effect of mutation on Rhodococcus equi virulence plasmid gene expression and mouse virulence. An 81 kb virulence plasmid containing a pathogenicity island (PI) plays a crucial role in the pathogenesis of Rhodococcus equi pneumonia in foals but its specific function in virulence and regulation of plasmid-encoded virulence genes is unclear. Using a LacZ selection marker developed for R. equi in this study, in combination with an apramycin resistance gene, an efficient two-stage homologous recombination targeted gene mutation procedure was used to mutate three virulence plasmid genes, a LysR regulatory gene homologue (ORF4), a ResD-like two-component response regulator homologue (ORF8), a...
Vibrio metschnikovii, a rare cause of wound infection. We report the first case of a postoperative wound infection caused by Vibrio metschnikovii on the lower right leg of a patient after saphenectomy. Compared to the healing of an uninfected site, that of the right leg was delayed, and a cure was achieved by intensified wound care. Several swabs taken from the infected site grew a gram-negative rod in pure culture that was identified as V. metschnikovii by the VITEK 2 system. The source of the infection was not detected; however, the absence of putative risk factors (exposure to water or shellfish or an episode of diarrhea), the profession of the...
Eye infections due to Listeria monocytogenes in three cows and one horse. A retrospective study was conducted to determine case histories, microbiological characteristics, and molecular subtypes associated with Listeria monocytogenes infections of the eye in large animals. For selected cases, environmental L. monocytogenes contamination patterns on case farms were also evaluated to probe for potential sources and spread of listerial eye infections. Records of 170 L. monocytogenes isolates from animal infections were reviewed to determine the fraction of isolates associated with eye infections (conjunctivitis, keratitis, and uveitis) of animals and to gather informat...
Evaluation of arthrocentesis site bacterial flora before and after 4 methods of preparation in horses with and without evidence of skin contamination. To evaluate the effectiveness of four methods of povidone-iodine preparation on skin bacterial flora of arthrocentesis sites, in horses, with and without evidence of skin contamination. Methods: Prospective randomized study. Methods: Twenty-four adult horses. Methods: Horses were assigned to either the clean or contaminated group based on housing environment and visual evidence of contamination. Using a moist sterile swab, microbial culture samples were obtained from the skin over the distal interphalangeal joints immediately before and after preparation. Each site was aseptically prepared wit...
Development of an in vivo Himar1 transposon mutagenesis system for use in Streptococcus equi subsp. equi. Streptococcus equi subsp. equi is the causative agent of the equine disease strangles. In this study we describe the development of an in vivo Himar1 transposon system for the random mutagenesis of S. equi and, potentially, other Gram-positive bacteria. We demonstrate efficient and random transposition of a modified mini-transposon onto the chromosome by Southern blot analysis and insertion site sequencing. Non-haemolytic mutants were isolated at a frequency of 0.2%, and acapsular mutants at a frequency of 0.04%. Taken together, these data demonstrate that in vivo Himar1 mutagenesis can be use...
Association between Key-Gaskell syndrome and infection by Clostridium botulinum type C/D. There is growing evidence that equine dysautonomia is a toxicoinfection with Clostridium botulinum type C. The possibility that feline dysautonomia has the same aetiology was investigated by attempting to detect botulinum type C neurotoxin in the food, faeces and the contents of the ileum of affected cats, and by serology. The toxin was detected directly in four of eight affected cats and after enrichment in seven of them, and in their dried food. No toxin was detected in healthy control cats or in their tinned food. Recent exposure to the organism was assessed by the detection of immunoglobul...
Equine abortion and premature birth associated with Cellulosimicrobium cellulans infection. During the 2002 and 2003 foaling seasons, Cellulosimicrobium (Cellumonas) cellulans (formerly Oerskovia xanthineolytica) was the principal microorganism isolated from fetal tissues or placentas from cases of equine abortion, premature birth, and term pregnancies. Significant pathologic findings included chronic placentitis and pyogranulomatous pneumonia. In addition, microscopic and macroscopic alterations in the allantochorion from 4 of 7 cases of placentitis were similar to those caused by Crossiella equi and other nocardioform bacteria. This report confirms a causative role of C. cellulans ...
The pathogenic equine streptococci. Streptococci pathogenic for the horse include S. equi (S. equi subsp. equi), S. zooepidemicus (S. equi subsp. zooepidemicus), S. dysgalactiae subsp. equisimilis and S. pneumoniae capsule Type III. S. equi is a clonal descendent or biovar of an ancestral S. zooepidemicus strain with which it shares greater than 98% DNA homology and therefore expresses many of the same proteins and virulence factors. Rapid progress has been made in identification of virulence factors and proteins uniquely expressed by S. equi. Most of these are expressed either on the bacterial surface or are secreted. Notable e...
Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma. To quantify the adhesion of Staphylococcus aureus to 4 equine bone surfaces passivated in a balanced polyionic solution (Plasmalyte) or hyperimmune equine plasma (Polymune plasma). Methods: In vitro comparative study. Methods: Third metacarpal bone (MC3) surface explants from 9 equine cadavers. Methods: Approximately 1 cm(2) sections of periosteum were removed from MC3 and stapled to sterile stainless steel screens. Three bone surface explants were cut using a surgical saw to present 1 cm(2) surfaces of subperiosteal bone, cut cortical bone, or endosteum. Duplicate explants of each surface wer...
The apparent digestibility of phytate phosphorus and the influence of supplemental phytase in horses. Availability of phytate-bound P as influenced by supplemental phytase was studied in eight horses consuming four diets in a 4 x 4 Latin square design experiment. The treatments were a control (containing a low P level, 18.4 g/d) and three high-P diets. These diets contained P as monocalcium phosphate (MCP; 43.7 g/d), myoinositol hexakisphosphate in the form of wheat and rice bran (MIHP; 41.8 g/d), or MIHP with microbial phytase (MIHPP; 42.5 g/d). The proportions of phytate-bound P were 3, 1, 55, and 56% for the control, MCP, MIHP, and MIHPP, respectively. The MIHPP diet was supplemented with 3...
Assessment of electrical charge on airborne microorganisms by a new bioaerosol sampling method. Bioaerosol sampling is necessary to monitor and control human exposure to harmful airborne microorganisms. An important parameter affecting the collection of airborne microorganisms is the electrical charge on the microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on airborne microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and po...
Screening of the equine intestinal microflora for potential probiotic organisms. Probiotics have not been demonstrated to provide any beneficial health effects in horses, possibly because of improper selection of probiotic organisms. This study was designed to identify lactic acid bacteria of equine origin with predetermined beneficial properties which might make them useful as therapeutic probiotics. Objective: A small percentage of lactic acid bacteria that are native to the intestinal tract of horses possess properties that may be useful in the treatment and/or prevention of gastrointestinal disease in horses. Methods: Faecal samples were collected from healthy mature h...
