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A microneutralization test (MNT) system utilizing cytopathic effect end points was effective in determing neutralization indexes for infectious bronchitis virus antibodies. The system is reproducible within 1 index unit at the 95% level of probability. Comparison of the MNT to tests in eggs resulted in a positive correlation (B =0.81), which was significant (P greater than 0.01). The quantitative dose-response relationship of the MNT is linear (P greater than 0.005), with the 95% prediction limits fitting between one 10-fold dilution.

A microneutralization fluorescent-antibody (MFA) test was effective in determining the level of antibodies to avian infectious bronchitis virus. A comparison of the MFA test with the cytopathic effect microneutralization (MNT) test and 50% plaque reduction (PR) test resulted in positive correlations that were significant (P less than 0.001). The PR test was more sensitive than either the MFA or the MNT test, but there was no significant difference between the sensitivities of the MFA and MNT tests. The MFA test has advantages over the PR test in the capacity to test large numbers of sera in a shorter period of time. The MFA test also can be completed in one-half the time required for the MNT test.

The most prevalent microorganisms isolated from urine specimens of dogs (385) and cats (132) with clinical signs of urinary tract infections were Escherichia coli, Proteus spp., and Staphylococcus aureus. The results of quantitative urine-culturing methods showed 48.6% of the canine and 12.1% of the feline specimens had more than 10(5) organisms per ml of urine. The bacteria isolated appear to have a greater resistance to antibacterial agents than previously reported.