Minimal inhibitory concentration of 42 antimicrobial agents was determined against 57 field strains of Actinobacillus pleuropneumoniae isolated from pigs in Spain. Penicillins, aminoglycosides, and tetracyclines had irregular activity; ticarcillin, tobramycin, and doxycycline were the most active of each group, respectively. Macrolides, vancomycin, dapsone, and tiamulin, to which strains had high rate of resistance, were almost ineffective. Thiamphenicol, colistin, rifampin, fosfomycin, mupirocin, and metronidazole had good activity, with resistance ranging between 0 and 8.8%. Finally, cephalosporins (except cephalexin) and quinolones especially ciprofloxacin, enrofloxacin, and sparfloxacin) were the most active antibiotics against A pleuropneumoniae.

Corynebacterium pseudotuberculosis phospholipase D (PLD) significantly affected viability of ovine neutrophils after 24 hours' exposure, This effect was more marked in cells that ingested PLD emulsified in oil. Treatment of neutrophils with PLD significantly (P < 0.05) reduced the ability of these cells to migrate toward activated sheep serum. The PLD was not chemotactic, but it activated normal sheep serum, producing factors that were chemotactic for neutrophils.

A study was performed to determine whether equine peritoneal macrophages produce interleukin 6 (IL-6) in vitro in response to endotoxin. Peritoneal fluid was collected from 14 clinically normal adult horses and was used as the source of peritoneal macrophages. Macrophages from each horse were isolated and cultured separately in vitro in the absence or presence of various concentrations (0.5, 5, or 500 ng/ml) of endotoxin (lipopolysaccharide from Escherichia coli 055:B5). Culture medium supernatants were collected after 3, 6, 12, and 24 hours' incubation and were frozen at - 70 C until assayed for IL-6 activity. Supernatant IL-6 activity was determined by use of a modified colorimetric assay and the murine hybridoma cell line B13.29 clone B.9, which is dependent on IL-6 for survival. Results indicated that equine peritoneal macrophages produce IL-6 in vitro and that supernatant medium IL-6 activity was significantly (P < 0.05) increased by exposure to endotoxin. Significant (P < 0.05) time and treatment effects on macrophage IL-6 production were apparent. The IL-6 activity peaked at 6 or 12 hours' incubation, then remained high through 24 hours' incubation, regardless of endotoxin exposure. Medium IL-6 activity during 3 and 6 hours' incubation was significantly (P < 0.05) greater in macrophages exposed to 5 or 500 ng of endotoxin/ml than in those exposed to 0.5 ng of endotoxin/ml; however peak IL-6 activity was similar among all endotoxin concentrations. Endotoxin concentration did not have an effect on medium IL-6 activity from macrophages exposed to endotoxin for 12 or 24 hours.

Stimulation of bovine alveolar macrophages with calcium ionophore A23187 resulted in marked production of leukotriene (LT)B4 and a lesser increase in thromboxane (TX)B2, whereas opsonized zymosan (OPZ) resulted in production of TXB2 and relatively small increases in LTB4 and prostaglandin (PG)F2 alpha. Alveolar macrophages incubated with recombinant bovine interferon-gamma or lipopolysaccharide, and subsequently stimulated with A23187 or OPZ, had altered arachidonic acid metabolism, producing markedly increased amounts of TXB2 and PGF2 alpha, and slightly increased LTB4. Incubation of alveolar macrophages with lipopolysaccharide had a more profound effect on the increased amounts of TXB2 and PGF2 alpha, observed in response to stimulation with A23187 or OPZ, than did incubation with interferon-gamma. Alveolar macrophages incubated with recombinant bovine interferon-alpha 1-1 also produced slightly increased amounts of LTB4 when stimulated with A23187 or OPZ. Altered arachidonic acid metabolism by alveolar macrophages exposed to interferons and lipopolysaccharide may contribute to the development of pulmonary inflammation, such as in the early stages of bacterial pneumonia following viral infections that induce interferon production.

An in vitro bioassay system was used to study the effects of cyclopiazonic acid (CPA) mycotoxin on cardiac muscle. Acute exposure to 6 microgram of CPA/ml of modified Krebs-Henseleit solution significantly (P < 0.05) decreased 5 in vitro turkey cardiac muscle performance criteria: maximal weight a muscle could lift; maximal contraction velocity; relaxation velocity; time to peak contraction; and total time for muscle contraction and relaxation. The effect on these 5 criteria appeared to result from intracellular changes partially associated with calcium availability and were irreversible, suggesting that physiologic changes had developed after acute exposure to CPA.

The ability of equine endometrium to release prostaglandin (GH) F, PGE2, and leukotriene (LT) B4 was studied in vitro, using endometrial tissue from diestrous mares. Because of the high cross-reactivity of the PGF antiserum with PGF1alpha and with PGF2alpha, results were quoted as total immunoreactive PGF. Significant concentrations of these arachidonate metabolites were released into tissue culture medium between 1 and 24 hours of incubation. Significantly higher concentrations of PGE, but not of PGE2 or LTB4, were released from endometria of mares with chronic endometritis than from genitally normal mares. Prostaglandin F was released only in low concentrations from the endometrium of a mare with pyometra, but concentrations of PGE2 and LTB4 were similar to those of genitally normal mares.