Antimicrobial therapy continues to be important in reducing losses due to pneumonic forms of Mycoplasma bovis disease in beef and dairy calves. Although M. bovis diseases have been documented as frequent and economically important in the United States, there are no published reports on the antimicrobial activity of approved compounds against US strains. In this study, the authors report on the activity of 9 different antimicrobials against 223 recently recovered isolates of M. bovis. These isolates represent accessions from 5 geographic regions of the United States and were grouped by 4 tissues of origin (milk, respiratory, joint, or ear and eye). A broth microdilution test was used to determine minimum inhibitory concentration (MIC) values by reading redox changes detected in broth with alamarBlue (resazurin) indicator. For each antimicrobial, the median, MIC50, MIC90, mode, and range were calculated, and the values used for comparisons. In the absence of accepted breakpoint values, published MIC cutoff values for animal mycoplasmas as well as Clinical Laboratory Standards Institute interpretive criteria were used as a reference to define in vitro activity. The MIC values from active antimicrobials were found to distribute independently of region of origin of the isolates or of tissue of origin. Enrofloxacin, florfenicol, and spectinomycin were found to be active compounds in vitro. Oxytetracycline and chlortetracycline were active against more than half of the isolates. Very few isolates were inhibited by tilmicosin and none by erythromycin, ampicillin, or ceftiofur. The antimicrobial profiles determined for these US strains were remarkably similar to those reported for European isolates. However, unlike in Europe, there appears to be no diversity of profiles when US isolates are grouped by region or tissue of origin.

Abstract. This survey was undertaken to determine the relative frequency of agents that are currently associated with neonatal diarrhea in swine, including Clostridium difficile and porcine reproductive and respiratory syndrome virus (PRRSV). The subjects for this study were the first 100 live 1-7-day-old piglets submitted to the Iowa State University Veterinary Diagnostic Laboratory with a clinical signalment of diarrhea, beginning on January 1, 2000. The evaluation of each pig included bacterial culture of a section of ileum, 2 sections of jejunum, and a single section of colon; a fluorescent antibody test (FAT) or immunohistochemistry (IHC) for transmissible gastroenteritis virus (TGEV); ELISA's for rotavirus and C. difficile toxins; IHC for PRRSV; and microscopic examination of ileum, midjejunum, spiral colon, liver, spleen, and lung. Survey results demonstrate a decline in the relative number of diagnoses of TGEV, Escherichia coli, and Clostridium perfringens type C compared with retrospective data. The combined case frequency rate for these 3 pathogens dropped from 70% in 1988 to 21% in 2000. This survey also demonstrated the emergence of C. difficile as an important pathogen of neonatal swine. Clostridium difficle toxin was detected in the colon contents of 29% of the piglets, and at least 1 toxin-positive animal was identified in 55% of the cases. All 29 C. difficile toxin-positive piglets had mesocolonic edema, and colitis was observed in 21 of 29 toxin-positive animals. PRRSV-positive macrophages were detected in the lamina propria of intestinal villi by IHC in 10 piglets with diarrhea. In 6 of these cases, PRRSV was the only pathogen detected. Gross and microscopic lung lesions were not a reliable indicator of PRRSV infection in these neonatal pigs with diarrhea. The addition of tests for C. difficile and PRRSV to a routine neonatal diarrhea diagnostic protocol resulted in a significant increase in the diagnostic success rate on both individual animal and case bases.The composition and priority rank of differential diagnoses for common disease syndromes is continuously changing as management practices, emerging diseases, and government programs alter the relative prevalence of contributing agents. This appears to be particularly true of neonatal diarrhea in swine. A report outlining retrospective diagnostic laboratory data from 1988 indicates that Escherichia coli and transmissible gastroenteritis (TGE) were each detected in 26% of suckling pigs with diarrhea, clostridial enteritis in 18%, coccidiosis in 15%, and rotavirus in 8% of the cases. 13 Escherichia coli, TGE, and necrotic clostridial enteritis combined to account for 70% of the case diagnoses in 1988. 13 These 3 diseases were detected in only 26% of neonatal diarrhea cases submitted to the Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) in 1999. Clostridium perfringens type A and Clostridium difficile, 2 diseases that were not reported in the retrospective study from 1998, were identified in 7% of the neonatal diarrhea cases ...

Brucella melitensis is the cause of brucellosis in sheep and goats, which often results in abortion. Few cases of B. melitensis infection in goats have occurred in the United States over the last 25 years. However, vigilance must be maintained, as it is for the bovine milk industry, to ensure that brucellosis is not introduced into the U.S. goat population. The objective of this study was to develop a sensitive and specific indirect enzyme-linked immunosorbent assay (iELISA) for the detection of B. melitensis-specific antibodies in goat milk. Brucella salt-extractable protein extract was employed as an antigen, and a horseradish peroxidase-labeled polyclonal anti-goat antibody was used as an anti-species conjugate. Thirteen of 13 (100%) individual infected goat milk samples tested positive and 134 of 134 (100%) uninfected bulk milk samples tested negative by the developed iELISA. Three positive milk samples with high, medium, and low absorbance values were used to simulate one positive animal in an otherwise negative herd. By this estimation, one high-titer animal could be detected in a herd of >1,600 animals. Detection estimates for medium-and low-titer animals were one positive animal per herd of <200 and 50 animals, respectively. Based on this estimation, it is recommended that herds be sampled in groups of 50 animals or less for bulk milk testing. The iELISA developed for this study was found to be sensitive and specific and shows potential for use as a bulk milk test for the detection of B. melitensis-specific antibodies in goat milk.Brucella species have impacted human and animal health for thousands of years (4, 18). Brucellae cause disease in goats, cattle, sheep, pigs, dogs, marine mammals, and several wild animals. The focus of this work was to develop a sensitive and specific diagnostic test for the detection of anti-brucella antibodies in goat milk. Goats are the natural hosts for Brucella melitensis. Although the United States has reported the eradication of B. melitensis in animals since 1972 (5), sporadic outbreaks have occurred in relation to infected imported goats (10,23). For the health of American goat milk consumers, vigilance in brucella detection must continue for the goat milk industry just as it has for the bovine milk industry.Brucella detection assays for goats are nearly the same as those for cattle because of the considerable genetic similarity between B. melitensis and B. abortus, and they have been extensively reviewed elsewhere (14). All of these methods have primarily focused on the use of serum as a diagnostic specimen. To date, little has been done to develop and validate diagnostic tests to detect B. melitensis infections by using goat milk. The detection of B. abortus in cow milk has been successful for years by use of the milk ring test (19). Because of a difference between the physiologic properties of goat and cow milk, the milk ring test does not perform well with goat samples (13).The objective of this study was to develop an indirect enzyme-linked immunosorbent assay (i...

Brucella melitensis is the cause of brucellosis in sheep and goats resulting in abortion. Few cases of B. melitensis infection in goats have occurred in the United States over the last 25 years. However, vigilance for brucellosis in goats must be maintained as it is in the bovine milk industry to ensure it is not introduced into the U.S. goat population. Diagnostic methods using serum have primarily been used for anti-brucellae antibody detection in goats. Collecting serum samples requires added labor for the producer and stress for the animal. A diagnostic test for specimens such as milk would therefore be advantageous. The objective of this study was to develop a sensitive and specific, indirect enzyme-linked immunoassay (iELISA) for the detection of B. melitensis antibody in goat milk. Brucella salt-extractable protein extract (BCSP) was employed as an antigen, and a horseradish peroxidase labeled polyclonal anti-goat antibody was used as an anti-species conjugate. Thirteen of 13 (I 00%) individual positive milk samples tested positive, and 134 of 134 (100%) negative bulk milk samples tested negative by the iELISA developed. Three positive milk samples of high, medium, and low titer were serially diluted in negative milk to simulate one positive animal in a negative herd. By this estimation, one high titer animal could be detected in a herd of greater than 1600 animals. Estimation for medium and low titer animals was one animal in a herd of less than 200 animals. The iELISA developed was found to be sensitive and specific and has potential for use as a bulk milk test for the detection of Brucella melitensis antibody in goat milk.

Mycoplasma bovis is involved in mastitis, pneumonia and polyarthritis of beef and dairy cattle. Infections can affect all ages and respond poorly to antimicrobial therapy. Variation in antimicrobial susceptibility profiles among isolates of M. bovis recovered from various tissues in dairy or beef outbreaks has been suspected but not verified. Increasing resistance of isolates has been recently documented, 1 so it appears that periodic large-scale surveillance would be useful to veterinarians, diagnosticians and researchers, especially to compare isolates from different regions within the US. It would also be beneficial to establish a standardized method for in-vitro susceptibility testing. This report contains antimicrobial susceptibilities for 223 isolates obtained from five US regions and from four tissue sites.