Screening of a high bioflocculant‐producing bacterial strain from an intensive fish pond and comparison of the bioflocculation effects with Rhodococcus erythropolis

A high bioflocculant‐producing bacterial strain BX‐13 isolated from an intensive fish pond by multiple subcultures and measured through primary screening and rescreening using kaolin. The strain BX‐13 was identified to belong to the same branch as Bacillus subtilis by morphological, physiological and biochemical, 16S rDNA gene sequencing, Blast homology search and multiple sequence alignments. The bioflocculation potential of BX‐13 and Rhodococcus erythropolis was compared, using water from the intensive pond where BX‐13 was isolated. The results showed the number of colonies in the BX‐13 treatment was higher than that of the R. erythropolis treatment from day 10 to the end of the experiment (p < 0.05). The numbers of both BX‐13 and R. erythropolis in the water body peaked on day 15, with 2.23 × 10⁷ cfu/L and 9.90 × 10⁶ cfu/L respectively. The bioflocculation volume (BFV) in water increased and then stabilized in both BX‐13 and R. erythropolis treatments. The BFV in BX‐13 peaked on day 25 (52.13 ml/L) and R. erythropolis peaked on day 30 (22.63 ml/L). At the end of the experiment, the BFV of the BX‐13 treatment was higher than the R. erythropolis treatment (p < 0.05). In conclusion, B. subtilis BX‐13 has a very strong flocculation effect, and merits further research into its application for water quality regulation in aquaculture systems.     

Multiple extra-pulmonary disorders associated with Rhodococcus equi infection in a 2-month-old foal

A 2-month-old Thoroughbred filly was referred to Hagyard Equine Medical Institute for further evaluation of acute pyrexia and a suspected intra-abdominal abscess based on abdominal ultrasonography performed in the field. Initial examination revealed bilateral uveitis, polysynovitis, a large internal abdominal abscess and pneumonia. A transtracheal wash confirmed the presence of a multi-sensitive strain of Rhodococcus equi. Anaemia and thrombocytopenia were noted during hospitalisation. Results of a Coombs test were consistent with an immune-mediated haemolytic process. Recurrent pyrexia, abdominal discomfort and severe respiratory distress unresponsive to intensive medical support motivated euthanasia followed by necropsy after 30 days of treatment. Overall, six extra-pulmonary disorders were simultaneously diagnosed despite the lack of pulmonary pyogranulomas.     

Influence of litter size and breed on variation in length of gestation in the dog

Summary

The variation in the length of gestation, the period from mating until parturition, was studied in 77 dogs of different breeds; the time for mating was determined by measuring peripheral blood progesterone levels. The mean length of gestation was 62.1 ± 0.2 (S.E.M.) days, with a variation of 11 days. The number of pups appeared to influence the length of gestation. Length of gestation was negatively correlated (r = ‐0.96, P < 0.001, n = 44) with litter size in litters with 7 or fewer pups. The intra‐breed variation in length of gestation in the five breeds represented by five or more bitches was 3 ‐ 6 days. The mean gestation of Alsatians (60.1 ± 0.5, n = 9) was shorter (P < 0.005) than that of the other breeds combined (62.3 ± 0.3, n = 68). The primiparous/multiparous status of the bitch did not influence the length of gestation.     

用红球菌生产类胡萝卜素的研究

从土壤中分离到一株黄色色素产生菌,经鉴定该菌为红球菌属（Rhodococcus)的一个种, 所产色素为类胡萝卜素。研究了pH、接种量、发酵周期、不同培养基、C源、N源种类等因素对该菌类胡萝卜素生成量的影响。结果表明,采用大米水解糖培养基、pH6.3、接种量为8%时色素产率最高。在最适条件下细胞生物量可达13.6 g/L,色素量为1.5 g/L。     

SONOGRAPHIC CHARACTERISTICS OF INTRAABDOMINAL ABSCESSATION AND LYMPHADENOPATHY ATTRIBUTABLE TO RHODOCOCCUS EQUI INFECTIONS IN FOALS

The sonographic characteristics of intraabdominal abscesses in 11 foals and intraabdominal lymphadenitis in five foals with Rhodococcus equi infections are presented. Intraabdominal abscesses were usually present in the ventral abdomen adjacent to the ventral body wall, well‐marginated, and contained a mixed or complex echo pattern. Lymphadenitis appeared as singular or multiple clusters of lymph nodes of mixed echogenicity adjacent to any portion of the gastrointestinal tract or body wall. Sonographic findings were supported by necropsy examinations, but sonographic measurements consistently underestimated the size of abscess.     

Rhodococcus equi occipital bone osteomyelitis,septic arthritis and meningitis in a neurological foal

This case report describes a 3‐month‐old female Thoroughbred foal that presented following the acute onset of apparent respiratory distress, abnormal head carriage and severe neurological deficits referable to the brainstem or cranial cervical spinal cord. Ultrasonography revealed an abscessing pneumonia. Radiographs did not show evidence of bony pathology at the atlanto‐occipital region, an area consistent with the observed neurological deficits. With magnetic resonance imaging, atlantal and occipital osteomyelitis, atlanto‐occipital septic arthritis, and atlanto‐axial synovitis were diagnosed. Brainstem meningitis and extradural compression were also revealed. Culture of the right occipitoatlantal joint and cerebrospinal fluid yielded a pure culture of Rhodococcus equi. These findings and multifocal R. equi abscessation were confirmed at necropsy.     

Rhodococcus equi (Prescottella equi) vaccines; the future of vaccine development

For decades researchers have been targeting prevention of Rhodococcus equi (Rhodococcus hoagui/Prescottella equi) by vaccination and the horse breeding industry has supported the ongoing efforts by researchers to develop a safe and cost effective vaccine to prevent disease in foals. Traditional vaccines including live, killed and attenuated (physical and chemical) vaccines have proved to be ineffective and more modern molecular‐based vaccines including the DNA plasmid, genetically attenuated and subunit vaccines have provided inadequate protection of foals. Newer, bacterial vector vaccines have recently shown promise for R. equi in the mouse model. This article describes the findings of key research in R. equi vaccine development and looks at alternative methods that may potentially be utilised.     

Efficacy of Gamithromycin for the Treatment of Foals with Mild to Moderate Bronchopneumonia

Background

Gamithromycin is active in vitro against the bacterial agents most commonly associated with bronchopneumonia in older foals. However, the clinical efficacy and safety of this drug have not been investigated.

Hypothesis

Gamithromycin is effective for the treatment of bronchopneumonia in foals.

Animals

One hundred and twenty‐one foals on a farm endemic for infections caused by Rhodococcus equi.

Methods

In a controlled, randomized, and double blinded clinical trial, foals with ultrasonographic evidence of pulmonary abscesses (abscess score 8.0–20 cm) were randomly allocated in 3 treatment groups: (1) gamithromycin IM q7 days (n = 40); (2) azithromycin with rifampin, PO q24h (n = 40); or (3) no antimicrobial treatment (controls; n = 41). Physical examination and thoracic ultrasonography were performed by individuals unaware of treatment group assignment. Foals that worsened were removed from the study.

Results

The proportion of foals that recovered without the need to be removed from the study was significantly higher for foals treated with gamithromycin (38 of 40) or azithromycin with rifampin (39 of 40) than for controls (32 of 41). Treatment with gamithromycin or with azithromycin‐rifampin resulted in a significantly faster decrease in the clinical score and abscess score compared to the controls. Adverse reactions characterized by colic (n = 18) and hind limb lameness (n = 14) were observed only in foals treated with gamithromycin.

Conclusion and Clinical Importance

Gamithromycin was noninferior to azithromycin with rifampin for the treatment of bronchopneumonia in the study population but had a higher frequency of adverse reactions.