Simple method for immunofluorescent identification of mycoplasma colonies

The effect of antimicrobial treatment and preventive strategies on bovine respiratory disease and genetic relatedness and antimicrobial resistance of Mycoplasma bovis isolates in a western Canadian feedlot

Feedlot calves (n = 3784) were systematically randomized and allocated in a 2 × 2 factorial study to receive metaphylactic oxytetracycline (OTC) on arrival or no antimicrobial, as well as florfenicol once subcutaneously or twice intramuscularly (48 h apart) if diagnosed with bovine respiratory disease (BRD). Calves of different treatment groups were comingled and followed from placement to re-implantation (~100 days). Animals receiving OTC had a reduced risk of BRD, an increased risk of arthritis, and no significant differences in average daily gain, BRD relapse, overall mortality, or BRD mortality. There were no significant differences between treatment protocols. Deep nasal swabs (n = 233) taken at arrival (n = 122), treatment (n = 77), and swabs from lungs and joints at postmortem (n = 34) were cultured for Mycoplasma bovis from 61 animals ill or dying of chronic pneumonia and arthritis and from 61 healthy calves. There was significant variation in diversity among isolates (n = 51) between study years and different cattle. Metaphylaxis or antimicrobial treatment did not affect the diversity of isolates. Except for tilmicosin, isolates were largely susceptible to tested antimicrobials.

Dual infection with Mycoplasma synoviae and a tenosynovitis-inducing reovirus in chickens

One group of embryonated chicken eggs was inoculated with sterile myco-plasma broth and another with a broth culture of Mycoplasma synoviae. Each group was subdivided into two and the chicks were hatched in four isolation pens. At 1 day of age one uninfected and one M. synoviae infected group were inoculated with a reovirus known to cause tenosynovitis. Birds were closely observed, and some were killed for sampling as chicks (1-5 weeks) and the remainder as adults (25-30 weeks). Clinical signs related to both organisms were seen in the dual-infected chicks and were more pronounced than in either of the corresponding single infections. There were significant weight differences between the infected and control chicks, except in single M. synoviae infection, and the mean weight of the birds with mixed infection was less than those with either single infection. Gross and histological lesions were observed in the hocks and livers of chicks in each infected group although with a higher incidence and severity in the dual-infection. Microscopic lesions were seen in the hearts of some birds in all three groups. Leg lesions associated with the reovirus infection persisted to maturity and another observation in mature, virus-infected birds was impaired egg production and fertility. M. synoviae was reisolated consistently from tracheas of single and dual-infected birds of all ages and reovirus from the tendons of inoculated birds for 4 weeks. Antibodies to both agents persisted throughout the period of the experiment.

Antibody response in calves experimentally or naturally exposed to Mycoplasma bovoculi

An antiglobulin-ELISA has been developed to detect antibody activity to Mycoplasma bovoculi in sera, nasal fluids and lacrimal fluids of field and experimentally exposed calves. Low IgG activity with no IgM or IgA was detected in sera of experimental calves. In nasal and lacrimal fluids, IgA appeared as early as the first week following exposure to M. bovoculi and predominated in both of these fluids throughout the 9 wk observation period. Sera from field-exposed animals showed high IgG and IgM activities. The metabolic-inhibition (MI) test was applied to detect growth inhibition of M. bovoculi in those fluids. This property was found only in sera of exposed animals and thus could be used to test for M. bovoculi infection. The ELISA test and the MI test were considered reliable tests for the detection of antibodies to M. bovoculi infection. The implications of finding no growth-inhibiting activity in nasal and lacrimal fluids concurrent with a high IgA activity are discussed.

Use of arginine aminopeptidase activity in characterization of arginine-utilizing mycoplasmas

The aminopeptidase activity of arginine-utilizing mycoplasmas was investigated with 20 aminoacyl beta-naphthylamide substrates. High levels of arginyl-beta-naphthylamide hydrolysis were demonstrated in 6 of 11 species when extracts of concentrated washed organisms were used. Relatively low arginine aminopeptidase activity was demonstrated with similar extracts from 22 species not utilizing arginine. The high level of arginine aminopeptidase activity could also be demonstrated with unwashed, unconcentrated samples of the same 6 species and also with Mycoplasma arthritidis. The procedure for preparing the extract of M. arthritidis appeared to remove the arginine aminopeptidase activity which was demonstrated to be present in the untreated culture. Fluorogenic and chromogenic tests were developed whereby this distinctive arginine aminopeptidase activity could be demonstrated within 4 h with the use of small volumes of broth culture (10 microliter) or single colonies, thus providing a rapid test for early characterization of some Mycoplasma species.

Rapid biochemical tests for characterization of the Mycoplasmatales

Methods are described for the rapid detection of beta-D-glucosidase and phosphatase in mycoplasma cultures using fluorogenic 4-methylumbelliferone substrates. These methods were applied to a selection of mycoplasma cultures and were compared with the conventionally used tests for these enzymes. Results were similar by both methods, but the fluorogenic tests could be read after 1 h, whereas the conventional tests took several days.