Prevalence of Rhodococcus equi from the nasal cavity of 1010 apparently healthy horses.

BACKGROUND: Rhodococcus equi is an important cause of foal pneumonia. While its isolation from different sources has been widely evaluated, there is a need to better understand the R. equi epidemiology from samples of the nasal cavity of healthy horses. OBJECTIVES: To determine the prevalence of R. equi from the nasal cavity of healthy horses, along with its virulence profile, antimicrobial susceptibility and environmental variables associated. STUDY DESIGN: Cross-sectional study. METHODS: Swabs from the nasal cavity of 1010 apparently healthy horses from 341 farms were submitted for bacteriological analyses. The identity and virulence profile of the R. equi isolates were assessed by multiplex PCR; antimicrobial susceptibility was determined by the disk-diffusion method. The occurrence of R. equi was calculated at the level of both animal and farm. The association of seven specific environmental factors with R. equi isolation was assessed using logistic regression and by a spatial scan statistical method to determine the presence of local clusters. RESULTS: Antimicrobial-sensitive R. equi was isolated from 10 (1%) of 1010 horses ranging between 3 and 29 years old. Ten farms (3%) had at least one positive horse. Only one R. equi isolate (10%) was classified as virulent. Red-Yellow Argisol (PVA/PV) soils were significantly associated with R. equi isolation (odds ratio (OR) 8.02; CI95% , 1.98-32.50, P = 0.01), and areas with well-drained soil were less likely to be test positive (OR 0.85; CI95% , 0.76-0.96, P = 0.03). MAIN LIMITATIONS: The use of culture-based method instead of PCR-based assay and the lack of soil sampling. CONCLUSIONS: Antimicrobial-sensitive R. equi may be considered a minor part of the normal bacterial flora in the nasal cavity of healthy and immunologically functional horses breeding on pasture. Further studies are warranted to determine if soils rich in iron and well-drained are, in fact, associated with the occurrence of R. equi.

The use of Ocimum americanum essential oil against the pathogens Aeromonas hydrophila and Gyrodactylus sp. in silver catfish (Rhamdia quelen).

UNLABELLED: The bactericidal activity (minimum inhibitory concentration (MIC)-test) of Ocimum americanum (inflorescences) essential oil (OAEO) against Aeromonas hydrophila was determined in this study. Also investigated was the potential of OAEO and the main compound found in the oil (linalool) at subinhibitory concentrations to be inhibitors of haemolysis caused by Aer. hydrophila in fish erythrocytes. An in vivo experiment was conducted to evaluate the survival of fish (Rhamdia quelen) experimentally infected with Aer. hydrophila and exposed to OAEO. A second experiment was conducted to evaluate the in vitro and in vivo activity of OAEO (mix from inflorescences and leaves) against the parasite Gyrodactylus sp. The OAEO showed weak in vitro activity against Aer. hydrophila (6400 µg ml(-1) ). Subinhibitory concentrations of OAEO (100 µg ml(-1) ) inhibited haemolysis (90%) caused by Aer. hydrophila in fish erythrocytes, however, linalool did not inhibit haemolysis activity. At the low concentrations (10 and 20 mg l(-1) ) added to the water, OAEO promoted the survival of fish experimentally infected with Aer. hydrophila. Lastly, the OAEO mix (50 mg l(-1) ) was effective against Gyrodactylus sp., significantly reducing (60%) the number of parasites in the fish. SIGNIFICANCE AND IMPACT OF THE STUDY: Phytochemicals, such as essential oils (EOs) are a great source of new molecules and have shown potential to be used in aquaculture systems. However, additional studies focused on the in vivo efficacy, mode of action and identification of the active compounds are needed. This study determined the potential of Ocimum americanum EO for use against two important fish pathogens, Aeromonas hydrophila and Gyrodactylus sp., as well as providing preliminary information about the role of the main EO compound (linalool) against Aer. hydrophila virulence.

Plant essential oils against Aeromonas hydrophila: in vitro activity and their use in experimentally infected fish.

AIMS: The aims of this study were to investigate the in vitro antibacterial activity of the essential oils (EOs) of Hesperozygis ringens (HREO), popularly known as 'espanta-pulga' and two different species of basil, Ocimum gratissimum (OGEO) and Ocimum americanum (OAEO), as well as, the potential of these products to be used in silver catfish (Rhamdia quelen) infected with Aeromonas hydrophila. METHODS AND RESULTS: OGEO and HREO showed better antibacterial activity in vitro. Subinhibitory concentrations of all EOs inhibited haemolysis caused by Aer. hydrophila in fish erythrocytes (100% reduction for OAEO at 100 µg ml(-1) and more than 90% for HREO and OGEO at 150 µg ml(-1) ). However, OAEO and HREO showed the best survival results (75 and 70% respectively) after their use as treatment (therapeutic baths-1 h daily/5 days) in silver catfish experimentally infected with Aer. hydrophila. A second in vivo assay using healthy fish was conducted to verify the potential of the EOs (preventive baths-1 h daily/5 days) to promote fish survival. Fish exposed to HREO and OAEO and their diluent (ethanol) showed significant lower haematocrit values and higher complement system activity compared to control. Plasma cortisol level was significantly higher in the groups exposed to both EOs. There was no significant difference in survival of silver catfish challenged with Aer. hydrophila after preventive baths with HREO, OAEO and control group. CONCLUSIONS: All tested EOs showed in vitro antibacterial properties against Aer. hydrophila and HREO and OAEO showed potential to be used in the treatment of infected fish. SIGNIFICANCE AND IMPACT OF THE STUDY: These products can be used in aquaculture as therapeutic and prophylactic agents against fish pathogens, with antimicrobial and/or immunostimulant properties.

Isolation of Prothoteca zopfii from a case of bovine mastitis in Brazil.

The isolation of Prothoteca zopfii, an algae lacking chlorophyll, from bovine mastitic milk, is described herein. The isolation was performed on 8% sheep blood agar, following incubation at 37 circC for 48 h. Based on biochemical tests, susceptibility to clotrimazole, and light and electron microscopic observation of cellular morphology the algae was identified as P. zopfii. The affected animal did not improve following treatment and had to be eliminated.