Experimental mastitis caused by Mycoplasma bovigenitalium and M. canadense in the ewe

Twelve strains of M. bovigenitalium and two of three strains of M. canadense caused an infection resulting in a pathogenic effect when experimentally inoculated into the ovine mammary gland. Differences in the pathogenesis were quantified by the duration of continuous mycoplasma excretion and the duration of high milk cell levels, but variation in the susceptability of the experimental animals prevented the establishment of firm conclusions on the relative virulence of the strains. Seven M. bovigenitalium and two M. canadense strains were eventually eliminated naturally from the infected glands, but four M. bovigenitalium strain infections ultimately became sub-clinical with intermittent mycoplasma excretion and low milk cell levels.     

Studies of bovine mycoplasma mastitis. 1. Review of literature on the occurrence of bovine mastitis with Mycoplasma involvement]

The clinical pattern as well as the pathologico-anatomic or histological changes due to mycoplasma mastitis are neither specific nor pathognomic. Mastitis pathogens so far described included M. bovis, M. bovigenitalium, A. laidlawii, A. axanthum, M. alkalescens, M. canadense, M. dispar, M. bovirhinis, strains of Group 7 according to Leach, strain ST 6, and ureaplasma strains. In the GDR, enzootic mastitis has been confined to A. laidlawii and A. axanthum.     

Studies of bovine Mycoplasma mastitis. 4. Serological classification of Mycoplasma strains isolated from 3 stocks

Thirty-two isolates from altered milk samples taken from cows with mastitis of two herds were serologically tested by the WHT against rabbit hyperimmune sera of 16 reference and type strains. The strains tested were associated and grouped in the following way: 16 M. bovis, nine A. laidlawii, and seven A. axanthum. The classification of on M. bovis strain was confirmed by SHT. Five isolates from another stock, with biochemical properties related to the family of mycoplasmataceae, were not serologically identified.     

Studies of bovine Mycoplasma mastitis. 3. Testing of biochemical properties of Mycoplasma strains isolated from 3 stocks

Thirty-two isolates of altered milk samples taken from cows with mastitis on three industrialised dairy cattle units were biochemically tested following five passes through no-inhibitor media, assessment of filtratability through 450-nm-membrane filter, and clone assay. Something between five and ten clones of each of the strains involved were tested for their growth properties both at 22 degrees C and in no-serum media, sensitivity to digitonin and capability of aesculin hydrolysis. TTC reduction (triphenyltetrazolium-chloride), as well as for decomposition of glucose, arginine, and urea. The properties found were characteristic of M. bovis, A. laidlawii, and A. axanthum, and of the family of mycoplasmataceaea in the strains of one of the stocks.     

Experimental infections of bulls with Mycoplasma (M.) bovis and M. bovigenitalium

M. bovis or M. bovigenitalium species experimentally used in intrapreputial infection were re-isolated from 7 of 8 bulls. Clinically manifest diseases did not develop at all, though slight inflammatory lesions were recorded from the genital tract of 2 animals. Mycoplasma findings are discussed together with results obtained from spermatological and hematological investigations.     

Antimicrobial susceptibilities of Mycoplasma isolated from bovine mastitis in Japan

Mycoplasma spp. are highly contagious pathogens and intramammary Mycoplasma infection is a serious issue for the dairy industry. As there is no effective vaccine for Mycoplasma infection, control depends on good husbandry and chemo‐antibiotic therapy. In this study, antimicrobial susceptibility of Mycoplasma strains recently isolated from cases of bovine mastitis in Japan was evaluated by minimum inhibitory concentration (MIC). All Mycoplasma bovis strains were sensitive to pirlimycin, danofloxacin and enrofloxacin, but not kanamycin, oxytetracycline, tilmicosin or tylosin. M. californicum and M. bovigenitalium strains were sensitive to pirlimycin, danofloxacin, enrofloxacin, oxytetracycline, tilmicosin and tylosin, but not to kanamycin. This is the first report to describe the MIC of major antimicrobial agents for Mycoplasma species isolated from bovine mastitis in Japan.     

Characterization of staphylococci associated with clinical and subclinical bovine mastitis

Attempts were made to identify 900 species of staphylococci or micrococci recovered from samples of bovine milk examined for mastitis pathogens. The presence and identity of haemolysins was recorded together with results of disc diffusion antibiotic sensitivity tests. The occurrence of clinical mastitis was also noted and somatic cell counts (SCC) were performed on milk samples which were normal in appearance. Eight hundred and thirty-one coagulase positive staphylococci were obtained, of which 810 were S. aureus and 21 were S. intermedius. Of 65 coagulase negative staphylococci the species of 19 could not be determined by the identification systems used. The remainder were identified as S. hyicus sub sp. hyicus (1), S. hyicus sub sp. chromogenes (19), S. haemolyticus (17), S. hominis (3), S. epidermidis (4), S. capitis (1) and either S. hominis or S. warneri (1). Four other isolates could not clearly be assigned to the genus Staphylococcus or Micrococcus and were designated irregular strains. No micrococci were identified. The presence of alpha, beta, or delta haemolysins occurring singly or in various combinations was identified in 98.3% of coagulase positive staphylococci and in 60% of coagulase negative staphylococci. Epsilon haemolysin was detected in 47.6% of the coagulase negative staphylococci and in 9.5% of S. intermedius. All staphylococci were sensitive to tetracycline (30 microg), novobiocin (1.6 microg), nafcillin (30 microg), methicillin (10 microg) and cephalothin (30 microg) and variable numbers of each species were sensitive to penicillin (2 iu) and streptomycin (10 microg). One non-identified species of coagulase negative staphylococcus was sensitive to erythromycin (0.4 microg) the remaining staphylococci were resistant. Each of the four irregular strains was sensitive to erythromycin and novobiocin. Clinical mastitis was associated with 30.6% of coagulase positive staphylococci, 15.3% of coagulase negative staphylococci, and two of the four irregular strains (50%). Subclinical mastitis as determined by SCC of 500 x 10(3) or greater was associated with 92.7% of coagulase positive and 37.5% of coagulase negative staphylococci.     

Invasive potential of bacterial isolates associated with subclinical bovine mastitis

This work describes differences in the invasive ability of bacterial isolates associated with mastitis. Invasion ability was determined by the uptake and survival in a primary culture of bovine mammary epithelial cells (BMEC). BMEC were isolated from a healthy lactating cow and characterized by their morphology, immunostaining for cytokeratin and the detection of beta- and kappa-casein mRNAs. Ten bacterial isolates comprising the staphylococcal species Staphylococcus aureus (3), Staphylococcus epidermidis (1), Staphylococcus haemolyticus (1), Staphylococcus equorum (2), Staphylococcus xylosus (1) and Brevibacterium stationis (2) obtained from raw milk of cows with mastitis from backyard farms were assayed for their ability to invade BMEC. Only two S. aureus and one S. epidermidis isolates were able to invade BMEC, at similar levels to the S. aureus control strain ATCC 27543. In conclusion, using the in vitro model of infection used in this study, differences in bacterial invasion capability may be detected.     

Studies of Mycoplasma mastitis in cattle. 7. Mycoplasma mastitis in 3 dairy cattle herds

Reported in this paper is the occurrence of enzootic mastitis in three dairy cattle stocks. The outbreaks had been caused by Mycoplasma bovis, Acholeplasma laidlawii, Acholeplasma axanthum as well as by one unidentified strain of the family of mycoplasmataceae. All animals with positive response to mycoplasma tests were identified an selected by repetitive testing of cultures in milk samples which had been taken from all lactating and dry cows and heifers as well as by evaluation of organ samples obtained from slaughtered cows. Regular cleaning and disinfection of stands in cowsheds, cattle tracks, and milk parlours as well as disinfection of udders and milking cups worked extremely well throughout the action in control of those cases of enzootic mycoplasma mastitis.