Properties and antimicrobial susceptibility of Trueperella pyogenes isolated from bovine mastitis in China.

Trueperella (T.) pyogenes is an opportunistic pathogen that causes suppurative diseases in domestic animals. In this work, the properties, pathogenesis and phenotypic diversity of T. pyogenes isolates from bovine mastitis were studied. Both pyolysin (plo) and collagen-binding protein (cbp) virulence factor genes were detected by PCR in all T. pyogenes isolates (n = 50). Using the tissue culture plate method, 90% of T. pyogenes isolates were able to form biofilms. The minimum inhibitory concentrations (MICs) of 13 antimicrobials against T. pyogenes isolates were determined. High susceptibility was observed to rifampin (96%), ampicillin (94%), ciprofloxacin (94%), and penicillin (92%), while low susceptibility was found to trimethoprim-sulphamethoxazole (10%) and bacitracin (2%). The intracellular assay revealed that T. pyogenes isolates had different cytopathogenic effects on cells. The high percentage (28.6%) of T. pyogenes isolates suggests that this bacterium is an important contributor to mastitis. Moreover, the high occurrence of multidrug resistance, biofilm production, intracellular survival, and the temporal dynamics of T. pyogenes interactions are key factors for a better understanding of how immunity acts on infections with these bacteria and how they evade immune surveillance, thus highlighting the need for the prudent use of antimicrobial agents in veterinary medicine.

Ethno-veterinary control of bovine dermatophilosis and ticks in Zhombe, Njelele and Shamrock resettlement in Zimbabwe.

A structured questionnaire survey was conducted to determine the ethno-veterinary practices and other control methods used by smallholder farmers for the management of bovine dermatophilosis and ticks. A total of 153 farmers were interviewed from Njelele, Zhombe communal and Shamrock resettlement areas. Crop production contributed most to livelihoods (83.2 %) while livestock contributed 9.0 %. Over 90 % of the respondents had attended school up to primary level, with 11.4 % undergoing animal health and husbandry training. Treatment of livestock diseases was practised by 96 % of the farmers, and 49.7 % of these farmers used ethno-veterinary medicines. Across the study sites, dermatophilosis was controlled using the following plants: Cissus quadrangularis (59.7 %), Catunaregam spinosa (10.5 %), Pterocarpus angolensis (10.5 %), Kalanchoe lanceolata (5.3 %), Aloe chabaudii (3.5 %), Cassia abbreviata (1.8 %), Dichrostachys cinerea (1.8 %), Urginea sanguinea (1.8 %), Ximenia caffra (1.8 %) and a plant locally called umfanawembila (1.8 %). Carica papaya and two plants, locally called mugimbura and umdungudungu, were used for tick control, and these were reported once from Njelele communal. Other control methods, besides plants or conventional drugs, were used by 28 % of the farmers for the treatment of dermatophilosis and ticks. Some farmers (14.4 %) claimed that ethno-veterinary medicines performed better than conventional drugs. The study revealed that farmers used ethno-veterinary medical practices for the treatment of dermatophilosis but rarely for tick control.

Development of ELISA test for determination of the level of antibodies against Rhodococcus equi in equine serum and colostrum.

Rhodococcus equi infection occurs worldwide and is one of the major causes of losing foals in the first six months of life. The application of serological tests in the diagnostics of rhodococcosis is limited, however they play a crucial role in immunological studies. The objective of this study was to develop and standardize ELISA test for the determination of the level of antibodies against Rhodococcus equi in equine serum and colostrum.Bacterial cell lysate was used as antigen. The test was standardized on 175 sera obtained from adult horses kept on rhodococcosis-free and endemic farms. Positive and negative control sera were used. The test detected IgG antibodies mainly against VapA protein, which was confirmed by Western blot analysis. The test was easy to perform, did not require inactivation of sera and had low well-to-well variation. The shelf life of antigen-coated ELISA plates was 21 days.The test allowed to reveal significant increase of R. equi-specific antibodies in both serum and colostrum in response to the vaccination (p<0.001). Therefore it can be applied to the evaluation of efficacy of immunization. Moreover, no statistically significant difference in the baseline antibody level in adult horses from rhodococcosis-free and endemic farm was revealed (α=0.05).

In vitro potential of equine DEFA1 and eCATH1 as alternative antimicrobial drugs in rhodococcosis treatment.

Rhodococcus equi, the causal agent of rhodococcosis, is a severe pathogen of foals but also of immunodeficient humans, causing bronchopneumonia. The pathogen is often found together with Klebsiella pneumoniae or Streptococcus zooepidemicus in foals. Of great concern is the fact that some R. equi strains are already resistant to commonly used antibiotics. In the present study, we evaluated the in vitro potential of two equine antimicrobial peptides (AMPs), eCATH1 and DEFA1, as new drugs against R. equi and its associated pathogens. The peptides led to growth inhibition and death of R. equi and S. zooepidemicus at low micromolar concentrations. Moreover, eCATH1 was able to inhibit growth of K. pneumoniae. Both peptides caused rapid disruption of the R. equi membrane, leading to cell lysis. Interestingly, eCATH1 had a synergic effect together with rifampin. Furthermore, eCATH1 was not cytotoxic against mammalian cells at bacteriolytic concentrations and maintained its high killing activity even at physiological salt concentrations. Our data suggest that equine AMPs, especially eCATH1, may be promising candidates for alternative drugs to control R. equi in mono- and coinfections.

Diagnosis, treatment, control, and prevention of infections caused by Rhodococcus equi in foals.

Rhodococcus equi, a gram-positive facultative intracellular pathogen, is one of the most common causes of pneumonia in foals. Although R. equi can be cultured from the environment of virtually all horse farms, the clinical disease in foals is endemic at some farms, sporadic at others, and unrecognized at many. On farms where the disease is endemic, costs associated with morbidity and mortality attributable to R. equi may be very high. The purpose of this consensus statement is to provide recommendations regarding the diagnosis, treatment, control, and prevention of infections caused by R. equi in foals.

Sensitivity to antibiotics of Arcanobacterium pyogenes and Escherichia coli from the uteri of cows with metritis/endometritis.

The aim of the study was to determine the in vitro sensitivity of 161 Arcanobacterium pyogenes strains and 99 Escherichia coli strains isolated from the uteri of 312 cows with metritis/endometritis. Animals with pathological discharges were clinically diagnosed per rectum and per vaginum, and then swabs from the lumen of the uterus were aseptically collected. Bacteriological examination of swabs was according to commonly accepted procedures with the additional use of API tests. Sensitivity to antibiotics was tested by the disk diffusion method and performed in Mueller-Hinton agar. Arc. pyogenes strains were the most sensitive to amoxicillin/clavulanic acid (Amc) (97.3%), bacitracin (96.7%), ceftiofur (95.8%) and cephapirin (77.5%). E. coli strains were the most sensitive to norfloxacin (98.1%), marbofloxacin (95.8%), gentamycin (88%), Amc (80.7%) and ceftiofur (73.1%). Arc. pyogenes and E. coli were most resistant to oxytetracycline (63.7% and 31%, respectively).

Determination of the prevalence of antimicrobial resistance to macrolide antimicrobials or rifampin in Rhodococcus equi isolates and treatment outcome in foals infected with antimicrobial-resistant isolates of R equi.

OBJECTIVE: To determine the prevalence of antimicrobial resistance to macrolide antimicrobials or rifampin in Rhodococcus equi isolates and to describe treatment outcome in foals infected with antimicrobial-resistant isolates of R equi. DESIGN: Cross-sectional study. SAMPLE POPULATION: 38 isolates classified as resistant to macrolide antimicrobials or rifampin received from 9 veterinary diagnostic laboratories between January 1997 and December 2008. PROCEDURES: For each isolate, the minimum inhibitory concentration of macrolide antimicrobials (ie, azithromycin, erythromycin, and clarithromycin) and rifampin was determined by use of a concentration-gradient test. Prevalence of R equi isolates from Florida and Texas resistant to macrolide antimicrobials or rifampin was determined. Outcome of antimicrobial treatment in foals infected with antimicrobial-resistant isolates of R equi was determined. RESULTS: Only 24 of 38 (63.2%) isolates were resistant to >or= 1 antimicrobial. Two isolates were resistant only to rifampin, whereas 22 isolates were resistant to azithromycin, erythromycin, clarithromycin, and rifampin. The overall prevalence of antimicrobial-resistant isolates in submissions received from Florida and Texas was 3.7% (12/328). The survival proportion of foals infected with resistant R equi isolates (2/8 [25.0%]) was significantly less, compared with the survival proportion in foals that received the same antimicrobial treatment from which antimicrobial-susceptible isolates were cultured (55/79 [69.6%]). Odds of nonsurvival for foals infected with resistant R equi isolates were 6.9 (95% confidence interval, 1.3 to 37) times the odds for foals infected with susceptible isolates. CONCLUSIONS AND CLINICAL RELEVANCE: Interpretation of the results emphasized the importance of microbiological culture and antimicrobial susceptibility testing in foals with pneumonia caused by R equi.

In vitro antimicrobial activity of gallium maltolate against virulent Rhodococcus equi.

The objective of this study was to determine the in vitro antimicrobial activity of gallium maltolate (GaM) against Rhodococcus equi. A total of 98 virulent bacterial isolates from equine clinical cases were examined, of which 19 isolates were known to be resistant to macrolides and rifampin. Isolates were cultured with various concentrations of GaM and minimal inhibitory concentration (MIC) values were determined after 24 and 48 h. Both the MIC(50) and the MIC(90) after 24h of growth were 558 ng/mL (8 µM) and after 48 h of growth were 2230 ng/mL (32 µM). There were no apparent differences between MICs of macrolide-resistant and macrolide-susceptible isolates.

The treatment of bovine dermatophilosis and its effect on some haematological and blood chemical parameters.

In this study, the authors evaluated parenteral treatment of zebu cattle, with naturally and experimentally induced bovine dermatophilosis, in western Sudan, using four different antibiotic treatments. In terms of recovery rate, weight gain, avoiding relapse and preventing death, gentamycin was found to be the most effective treatment, followed by a combination of penicillin and streptomycin and, finally, long-acting oxytetracycline. However, enrofloxacin was not successful. A significant improvement in the red blood cell count was noticed among cattle treated with penicillin-streptomycin (p = 0.021) and gentamycin (p = 0.029). All treated cattle, except those treated with enrofloxacin, showed a significant improvement in mean corpuscular haemoglobin concentration (p = 0.021); mean corpuscular volume (p = 0.021), and white blood cell count (p < 0.021). Significant improvements were observed among treated cattle in their total levels of protein, calcium (p = 0.021) and cholesterol (p < 0.05), when compared to untreated cattle infected with Dermatophilus congolensis. This study recommends gentamycin as a drug of choice for the parenteral treatment of dermatophilosis. Treatment was not only effective in early, mild cases but also useful among moderately and heavily affected cattle. According to the observations of the authors, when no intervention took place, the condition of moderately and heavily affected cattle deteriorated and/or resulted in death.

Chemoprophylactic effects of azithromycin against Rhodococcus equi-induced pneumonia among foals at equine breeding farms with endemic infections.

OBJECTIVE: To determine the effect of azithromycin chemoprophylaxis on the cumulative incidence of pneumonia caused by Rhodococcus equi, age at onset of pneumonia, and minimum inhibitory concentration (MIC) of azithromycin for R equi isolates cultured from fecal and clinical samples. DESIGN: Controlled, randomized clinical trial. ANIMALS: 338 foals born and raised at 10 equine breeding farms; each farm had a history of endemic R equi infections. PROCEDURES: Group 1 foals were control foals, and group 2 foals were treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 48 h) during the first 2 weeks after birth. Foals were monitored for development of pneumonia attributable to R equi infection and for adverse effects of azithromycin. Isolates of R equi were tested for susceptibility to azithromycin. RESULTS: The proportion of R equi-affected foals was significantly higher for control foals (20.8%) than for azithromycin-treated foals (5.3%). Adverse effects of azithromycin treatment were not detected, and there were no significant differences between groups for the MICs of azithromycin for R equi isolates cultured from fecal or clinical samples. CONCLUSIONS AND CLINICAL RELEVANCE: Azithromycin chemoprophylaxis effectively reduced the cumulative incidence of pneumonia attributable to R equi among foals at breeding farms with endemic R equi infections. There was no evidence of resistance to azithromycin. Nonetheless, caution must be used because it is possible that resistance could develop with widespread use of azithromycin as a preventative treatment. Further investigation is needed before azithromycin chemoprophylaxis can be recommended for control of R equi infections.

[Diagnosis and therapy of Rhodococcus equi infection in the horse]. / De diagnostiek en therapeutische mogelijkheden van een Rhodococcus equi infectie bij het paard.

Infection with Rhodococcus equi is an important cause of pneumonia in foals, but other organ systems may also be affected. The intracellular presence of R. equi and the formation of granulomatous and suppurative inflammatory tissue mean that prolonged treatment is needed. The pharmacological properties of the combination of erythromycin and rifampicin have improved the survival of foals infected with R. equi; however, erythromycin can cause adverse reactions in foals and mares, which has prompted the search for alternative therapies. The combination of azithromycin or clarithromycin with rifampicin seems to be a promising alternative. However these combinations are expensive and adverse effects remain to be determined, especially in the dams of treated foals. Thus correct diagnosis and appropriate use of drugs are essential for the treatment of R. equi infection in foals.

Phenotypic mutants of the intracellular actinomycete Rhodococcus equi created by in vivo Himar1 transposon mutagenesis.

Rhodococcus equi is a facultative intracellular opportunistic pathogen of immunocompromised people and a major cause of pneumonia in young horses. An effective live attenuated vaccine would be extremely useful in the prevention of R. equi disease in horses. Toward that end, we have developed an efficient transposon mutagenesis system that makes use of a Himar1 minitransposon delivered by a conditionally replicating plasmid for construction of R. equi mutants. We show that Himar1 transposition in R. equi is random and needs no apparent consensus sequence beyond the required TA dinucleotide. The diversity of the transposon library was demonstrated by the ease with which we were able to screen for auxotrophs and mutants with pigmentation and capsular phenotypes. One of the pigmentation mutants contained an insertion in a gene encoding phytoene desaturase, an enzyme of carotenoid biosynthesis, the pathway necessary for production of the characteristic salmon color of R. equi. We identified an auxotrophic mutant with a transposon insertion in the gene encoding a putative dual-functioning GTP cyclohydrolase II-3,4-dihydroxy-2-butanone-4-phosphate synthase, an enzyme essential for riboflavin biosynthesis. This mutant cannot grow in minimal medium in the absence of riboflavin supplementation. Experimental murine infection studies showed that, in contrast to wild-type R. equi, the riboflavin-requiring mutant is attenuated because it is unable to replicate in vivo. The mutagenesis methodology we have developed will allow the characterization of R. equi virulence mechanisms and the creation of other attenuated strains with vaccine potential.

Unidentified coryneform bacterial strain from cases of polyarthritis in chickens: phenotype and fatty acid profile.

We report isolation of a strain of fermentative coryneform bacteria from an outbreak of polyarthritis in chickens. This strain could not be assigned to any recognized bacterial taxon because its peculiar phenotype is not yet reported. The strain possessed phenotypic characteristics and fatty acid profile similar to Erysipelothrix but, on the other hand, exhibited temperature-dependent motility like Listeria. We found no evidence of either Mycoplasma synoviae or Chlamydia infection. Details of the phenotype and fatty acid profile of the isolate and measures undertaken to contain the outbreak have been described.

Effect of sucrose thermal oligosaccharide caramel, dietary vitamin-mineral level, and brooding temperature on growth and intestinal bacterial populations of broiler chickens.

Two experiments were conducted to determine the effect of sucrose thermal oligosaccharide caramel (STOC) and dietary vitamin-mineral (V/M) level on growth performance and intestinal microflora of broiler chickens. In Experiment 1, Peterson x Arbor Acres male broilers (n = 384) were randomly allocated into four groups that were fed either the control diet or diets containing the antibiotic virginiamycin (11 mg/kg), 3.7% STOC or 7.5% STOC for 4 wk at brooding temperatures of 32 to 29.7 C. Weight gains for broilers in Experiment 1 were greater (P < 0.001) for birds fed STOC diets, with weight gains of 763, 822, 1,124, and 1,080 g for birds on the control, antibiotic, 3.7% STOC, and 7.5% STOC diets, respectively. Feed intake and feed conversion by birds fed STOC diets were also significantly improved. Cecal bifidobacterial numbers were increased (P < 0.03) over the control diet with numbers being 5.98, 6.99, 7.47, and 7.39 log10 cfu/g cecal DM, respectively. In Experiment 2, Peterson x Hubbard male broilers (n = 384) were used in a 2 x 2 x 2 factorial arrangement with two levels of V/M premix (0.5 or 1% of the diet), two levels of STOC (0 or 3.5% of the diet), and two brooding temperatures, normal (32 to 23.6 C) or high (32 to 29.7 C) for 4 wk. Feeding the STOC diet improved (P < 0.05) weight gain, feed intake, and feed conversion of broilers. The effect of STOC on animal performance was less evident when broilers were fed twice the NRC recommended levels of V/M. Feeding the STOC diets resulted in a significantly greater increase in weight gain at high brooding temperatures than at normal brooding temperatures. There was also a reduction (P < 0.05) in numbers of total aerobes and coliforms in the ceca of birds fed diets containing STOC. Feeding STOC has potential to improve growth performance of broiler chickens.