Antibody response of swine experimentally infected with Mycoplasma hyosynoviae.

Antibody responses of swine inoculated intranasally with M. hyosynoviae were determined using complement-fixation, latex-agglutination, metabolic-inhibition, and mycoplasmacidal tests. The infected swine developed latex-agglutinating antibodies by 6 days postinoculation, complement-fixing and metabolic-inhibiting antibodies by 9-12 days, and mycoplasmacidal antibodies which were first detected from 12 days to 8 weeks postinoculation. Antibody titers persisted for as long as 6 months postinoculation. Complement-fixing and mycoplasmacidal antibodies were mainly IgG, and latex-agglutinating antibodies were IgM. Early metabolic-inhibiting antibodies were IgM while later antibodies were mainly IgG. None of the pigs had detectable complement-fixing antibodies to Mycoplasma hyorhinis.

Modified metabolic-inhibition test for detection of antibodies to Mycoplasma hyosynoviae in swine serum.

A modification of the metabolic inhibition (MI) test was used for detection of antibodies against Mycoplasma hyosynoviae in convalescent swine serum. Supplementation of the MI system with 1% unheated normal rabbit serum, as well as 6% unheated normal guinea pig serum was required for detection of MI antibodies in early phase, postinfection serum and markedly improved detection of MI antibodies in late phase, postinfection serum. Factor(s) supplies by rabbit serum was not supplied by unheated normal swine serum.

Susceptibility of sows to experimentally induced Escherichia coli mastitis.

A study was conducted to compare susceptibility of sows from 2 herds to experimentally induced Escherichia coli mastitis. Four sows each from herds R and S were inoculated intramammarily at postpartum hour 8 with a strain of E coli shown previously to be capable of producing mastitis. After inoculation with E coli, sows from herd S had higher temperatures, lower WBC counts, and lower plasma protein:fibrinogen ratios than did sows from herd R. Inoculated sows from herd S lost 83% of newborn pigs due to starvation by 14 days after inoculation, whereas sows from herd R lost none. Control, noninoculated sows from both herds had normal temperatures, normal hematologic values, and minimal mortality of piglets. Levels of antibodies (complement fixing, enzyme-linked immunosorbent assay, and agglutinating) to E coli in preinoculation sera from the 2 populations of sows did not differ. Assay of lactoferrin by radial immunoassay revealed comparable concentrations in milk of sows from both herds during the first 24 hours after sows had delivered, but significantly higher values were detected in milk from sows of herd S at postpartum days 2 and 3. The basis for the marked difference in susceptibility to E coli-induced mastitis was not determined except that "susceptible" sows (herd S) were from a conventional herd and "resistant" sows (herd R) were from a specific-pathogen-free herd.

Bacteriologic study of sow agalactia.

Necropsy of 13 agalactic and 11 normally lactating sows at 1 to 2 days after parturition revealed that 7 of the agalactic and 4 of the clinically normal sows had lesions of mastitis. Escherichia coli, Streptococcus equisimilis, and Staphylococcus epidermidis were the predominant organisms isolated. The organisms were isolated as pure and as mixed cultures and all 3 were isolated from normal appearing, as well as mastitic, glands. Pure culture isolation of E. coli (44 gland segments) was significantly associated with microscopic lesions of mastitis, regardless of the number of colonies isolated, whereas pure culture isolation of Streptococcus equisimilis or S epidermidis in low to moderate numbers was not. Isolation of large numbers of beta-hemolytic streptococci (2 gland segments) or of S epidermidis (6 gland segments) was associated with microscopic evidence of mastitis. Cultural examination of uterus and cervix revealed 5 isolates of strict anaerobic bacteria, all different species, from 4 of the 24 sows. Culture of 2 mammary glands from each sow revealed no strict anaerobes. Phase-contrast microscopic examination of specimens from mammary glands, uterus, and cervix of each sow revealed no spirochetes. Attempts to isolate mycoplasmas and chlamydiae from mammary gland, uterine tube (fallopian tube), uterus, cervix, and urethra of the 24 sows were negative. The evidence confirms previous reports that coliforms are the most significant bacteria in mastitis of the sow.

Determination of sensitivity of Mycoplasma hyosynoviae to tylosin and selected antibacterial drugs by a microtiter technique.

A microtiter technique was used for determination of the sensitivity of Mycoplasma hyosynoviae to antibiotics and other drugs. Use of a biphasic agar-broth medium in microtiter plates allowed direct visualization of growth. Results were more reproducible with this system than when broth alone was used and evaluation based on color change was required. Attempts to adapt the test for use with Mycoplasma hyorhinis were not successful. Minimal inhibitory concentrations of 12 drugs and drug combinations for 12 strains of M. hyosynoviae are presented. Drugs with the lowest minimal inhibitory concentrations were tylosin (0.37 mcg/ml)and lincomycin (0.88 mcg/ml), both of which have been used for treatment and control of M. hyosynoviae arthritis. Comparison of the minimal inhibitory concentrations of tylosin for 43 isolates of M. hyosynoviae obtained in 1959 and 1960 and from 1966 through 1971 indicated the possibilty of decreasing sensitivity to the drug although differences between recent isolates and earlier ones were not statistically significant.