Introduction: Immune-potentiating functions of Lactobacillus plantarum strains in the common carp were evaluated. Material and Methods: Fourteen days of feeding fish dry diet supplemented with the bacteria provided parameters of nonspecific humoral immunity (lysozyme, ceruloplasmin, γ-globulin, total protein levels, and serum bactericidal activity) and cellular immunity (pinocytosis, respiratory burst activity, and potential killing activity of organ phagocytes), as well as the proliferative response of organ lymphocytes stimulated with mitogens. The resistance of fish to infection with Aeromonas hydrophila was also determined. Results: Dietary supplementation with L. plantarum had a substantial influence on the activity of organ phagocytes, especially the potential killing activity of head kidney cells. A significant increase in the proliferative activity of LPS-stimulated B lymphocytes and in the levels of γ-globulins and total protein was observed. The supplemented diet conveyed higher resistance than the control diet as the cumulative fish mortalities after infection with A. hydrophila were 65% and 85%, respectively. Conclusion: The results indicate that dietary supplementation with L. plantarum stimulates the antibacterial resistance of common carp and may reinforce defence against bacterial infections, but further studies need to be conducted.

Disinfection is key for controlling microbial contamination and ensuring the safe production of milk and dairy products. In this study, we developed a new disinfection method using quaternary ammonium surfactant N-dodecyl-2-(pyridin-1-yl) acetamide chloride as the main component to form a bactericidal complex with either chlorhexidine acetate or glutaraldehyde, and we evaluated the bactericidal effects, safety, and clinical application value of the compound disinfectants. An in vivo acute oral toxicity assay in mice showed an LD50 > 5000 mg/kg body weight without abnormality in pathological tissue sections. Comparison with commercially available products also showed that they have outstanding bactericidal effects. Clinical trials proved that the compound disinfectants have excellent bactericidal effects on the air and ground of the dairy farm and on the skin of cattle, especially in a dairy farm environment. Our findings confirm that the new compound disinfectants have excellent bactericidal performance and are safe to use as disinfectants to prevent mastitis and contamination of the cattle farm environment.

OBJECTIVE To evaluate the impact of gentamicin, silver, or both additives in polymethylmethacrylate (PMMA) beads on methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilm formation in vitro. SAMPLE 4 preparations of PMMA beads (formed with no additive [control], gentamicin, silver, and gentamicin and silver). PROCEDURES Beads from each group were exposed to 10 MRSP isolates known to be strong biofilm formers. Following incubation, the beads were rinsed to remove planktonic bacteria, then sonicated to dislodge biofilm-associated bacteria. Resulting suspensions were serially diluted, plated on blood agar, and incubated overnight; CFUs were counted. Variance of mean CFU counts following log10 transformation was analyzed among PMMA groups. RESULTS None of the PMMA additives tested completely inhibited MRSP biofilm formation. There was a significant effect of gentamicin and gentamicin plus silver on this variable, compared with controls, but not of silver alone. There was no difference between gentamicin and gentamicin plus silver. When only isolates not susceptible to gentamicin were evaluated, there were no significant differences among PMMA additive groups. Within gentamicin-susceptible isolates, there was an impact of gentamicin and gentamicin plus silver, but no impact of silver alone and no difference between gentamicin and gentamicin plus silver. CONCLUSIONS AND CLINICAL RELEVANCE Gentamicin-impregnated PMMA was effective at reducing biofilm formation of gentamicin-susceptible MRSP isolates but had no effect on isolates not susceptible to gentamicin. Silver-impregnated PMMA had no effect on MRSP biofilm formation. Results suggested that gentamicin-impregnated PMMA may not be effective in vivo against MRSP isolates not susceptible to gentamicin. Antibacterial efficacy of silver should not be assumed without proper testing of the target bacteria and specific silver compound.

Objective-To evaluate the ability of bovine complement to kill a variety of field isolates and laboratory strains of Brucella abortus. Design-The experimental approach was to determine the sensitivity of B abortus isolates to killing by bovine serum, and to document the role of complement in brucellacidal activity. Sample population-Six laboratory isolates and 12 field isolates of B abortus were tested. Procedure-The ability of B abortus to survive exposure to undiluted bovine serum for 2 hours at 37 C was assessed. The role of complement in killing was determined by examining the ability of heat (56 C for 60 minutes) and cobra venom factor to obliterate the activity in serum, and by detecting binding of the ninth component of bovine complement to serum-sensitive target cells. Results-Isolates of B abortus that were resistant to the bactericidal activity of normal bovine serum were revealed. These included field isolates and laboratory strains. Furthermore, the study confirmed earlier reports that bovine serum-mediated killing of B abortus is caused by the complement cascade. Conclusions-Some isolates of B abortus, like other gram-negative bacteria, were resistant to complement-mediated killing. Resistance was associated with smooth colony morphology. Isolates lacking detectable O antigen were serum sensitive.

A total of 22 clinical streptococcal isolates, predominantly Streptococcus zooepidemicus, associated with endometritis in horses were tested for their ability to withstand the natural bactericidal properties of freshly obtained blood. During a 3-hour incubation in blood from a single horse, 8 of these isolates survived and grew; the remainder were killed. To determine whether this ability to grow extended to blood of other horses, 5 of these growing isolates were tested for their ability to grow in the blood of 5 additional horses. The same 5 horses were used for each isolate. The isolates grew in blood of some of the horses, but were killed in blood of the others. However, the horse's blood that mediated killing was different for each isolate. Killing required leukocytes, but the specificity for killing appeared to reside in plasma, although plasma by itself was not bactericidal. Heat-stable and heat-labile components in plasma, interpreted as antibody and complement, respectively, appeared necessary for killing. Isolates that could grow in fresh blood lost this ability after 10 passages in artificial media. Results of these experiments of phagocytosis in fresh blood may provide helpful insights into the phagocytosis of S zooepidemicus in equine uterine f1uid.

Effect of estrogen (E2) and progesterone (P4) on uterine antibacterial activity and immunoglobulin concentrations in mares was studied. In 2 in vitro experiments, 6 mixed-breed mares were ovariectomized, and uterine fluid and blood serum were analyzed. Antibacterial assay methods were used to determine inhibitory effects on Streptococcus zooepidemicus of uterine fluid samples collected on days 3, 5, and 8, and serum obtained on day 8 of treatment. Single radial immunodiffusion methods were used to quantify amounts of IgA and IgG in uterine fluid and serum on days 3, 5, 8, and 14 of treatment. Neither E2 nor P4 increased activity of serum and uterine fluid against S zooepidemicus. Numbers of colony-forming units per milliliter of bacteria were significantly (P < 0.01) lower in control Hanks' balanced salt solution with 1.0% gelatin (HBSSG) than in uterine fluids. Bacterial numbers were significantly (50%) greater in uterine fluids and serum than in HBSSG controls for both treatments. Both fluids, especially serum, supported significantly (P < 0.01) more growth of S zooepidemicus than did HBSSG when incubated for 0, 2, and 4 hours. These findings are in contrast to previous reports of antibacterial activity in the uterus of sexually intact mares undergoing an estrous cycle: great reduction of bacterial count in uterine fluid from mares in diestrus, and significant increases in bacterial numbers in uterine fluid or serum from mares in estrus. Treatment comparisons between serum and uterine fluid IgA and IgG concentrations were not significantly different, although overall IgA concentration in the uterus was higher than concentration in serum. The IgG concentration in uterine fluid was higher in P4- than E2-treated mares. However, IgG concentration was significantly (P < 0.01) higher in uterine fluid on day 8 in P4-treated mares than on day 3 or 5. Results of this study indicate that neither immunoglobulin concentration nor hormone treatment has a direct effect on streptocidal activity.

Chemical and cytologic effects and bactericidal activity of gentamicin in septic synovial fluid were evaluated in an experimental model of infectious arthritis in horses. Septic arthritis was induced by inoculation of approximately 7.5 x 10(6) colony-forming units of Escherichia coli into 1 antebrachiocarpal joint in each of 16 clinically normal adult horses. Clinical signs of septic arthritis were evident 24 hours after inoculation. Horses were allotted to 3 groups: group-1 horses (n = 5) each were given 150 mg of gentamicin (50 mg/ml; 3 ml) intra-articularly (IA); group-2 horses (n = 5) each were given 2.2 mg of gentamicin/kg of body weight, IV, every 6 hours; and group-3 horses (n = 6) each were given buffered gentamicin, consisting of 3 mEq of sodium bicarbonate (1 mEq/ml; 3 ml) and 150 mg of gentamicin (50 mg/ml; 3 ml), IA. Synovial fluid specimens were obtained at posttreatment hour (PTH) 0, 0.25, 1, 4, 8, 12, and 24 via an indwelling intra-articular catheter. Synovial fluid pH was evaluated at PTH 0, 0.25, and 24. Microbiologic culture and cytologic examination were performed on synovial fluid specimens obtained at PTH 0 and 24, and gentamicin concentration was measured in all synovial fluid specimens. At PTH 0, E coli was isolated from synovial fluid specimens obtained from all horses. Synovial fluid pH was lower (range, 7.08 to 7.16) and WBC count was higher (range, 88,000 to 227,200 cells/microliter) and predominantly neutrophilic (95 to 99%) at PTH 0 than before inoculation. Synovial fluid pH was lowered further (mean, pH 6.63) after IA administration of gentamicin in group-1 horses; mean pH remained unchanged (7.07) after buffered-gentamicin administration in group-3 horses. At PTH 0.25, mean peak synovial fluid gentamicin concentration in horses of groups 1 and 3 (4,745 and 6,190 microgram/ml, respectively) was 1,000 times greater than that in group-2 horses (5.1 microgram/ml) at the same time. Synovial fluid gentamicin concentration in group-1 and group-3 horses was always greater than that in group-2 horses and remained greater than a minimal inhibitory concentration of gentamicin (2 microgram/ml) against many common equine bacterial pathogens for at least 24 hours after injection. Further, the calculated apparent half-life and clearance of gentamicin in synovial fluid calculated after IA administration were similar in horses of groups 1 and 3. By PTH 24, E coli could not be isolated from synovial fluid specimens obtained from group-1 horses. However, moderate to heavy growth of E coli was isolated from synovial fluid specimens obtained at PTH 24 from horses in groups 2 and 3 (80 and 66%, respectively). In selected cases, IA administration of unbuffered gentamicin may be a useful supplement to drainage, lavage, and systemic antibacterial and anti-inflammatory treatment in horses with naturally acquired infectious arthritis.

The possible role of the complement-mediated bactericidal system in protection of swine against contagious pleuropneumonia was investigated. Strains of Actinobacillus (Haemophilus) pleuropneumoniae representing serotypes 2, 3 and 5 were found to be fully resistant to the bactericidal action of porcine serum from precolostral, clinically normal adult, and chronically infected pigs. All strains were also resistant to hyperimmune rabbit serum, but 3 of 4 strains were sensitive to normal human serum. This bactericidal effect was lost when human serum was previously absorbed with the homologous bacteria, indicating that antibody was necessary for killing. Addition of human serum to porcine serum or to absorbed human serum did not restore the bactericidal system. Pretreatment of the bacteria with undiluted heat-treated human serum also failed to sensitize the bacteria to the absorbed serum, indicating that a heat-labile, absorbable factor may have been required for killing of A pleuropneumoniae. None of the strains was sensitized to porcine serum by sublethal treatment with polymyxin B, a treatment that is known to disrupt the integrity of the outer membrane and induce serum sensitivity in gram-negative bacteria. The ability of A pleuropneumoniae to resist complement killing in vitro may reflect a virulence mechanism in vivo that assists bacteria in avoiding the pulmonary defenses of swine and promotes bacterial invasion of the lungs.

The relationship of serum complement activity and bacteriostatic activity was investigated in male guinea pigs given aflatoxin and/or rubratoxin. In experiment 1, guinea pigs were given 0.6 mg of aflatoxin/kg of body weight, PO, once. In experiment 2, guinea pigs were given 0.02 mg of aflatoxin/kg, PO, and/or 8 mg of rubratoxin, PO, 11 times. Aflatoxin (0.02 mg/kg) had no effect given alone, but potentiated the effect of rubratoxin. In both experiments, changes in complement activity were accompanied by similar but not always significant (P less than 0.05) changes in bacteriostatic activity of serum. Guinea pigs given 0.06 mg of aflatoxin/kg had significant (P less than 0.05) changes in complement titers and in serum alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase activities. Guinea pigs given repeated oral doses of aflatoxin and/or rubratoxin had changes in complement titers, bacteriostasis, and alkaline phosphatase and aspartate aminotransferase activities, but not in alanine aminotransferase activities. Significant differences were detected only when average values for all guinea pigs given rubratoxin or rubratoxin with aflatoxin were compared with average values for guinea pigs not given rubratoxin.

OBJECTIVE To evaluate the effects of vaporized hydrogen peroxide (VHP) sterilization on the in vitro antimicrobial efficacy of meropenem-impregnated polymethyl methacrylate (M-PMMA) beads. SAMPLE 6-mm-diameter polymethyl methacrylate beads that were or were not impregnated with meropenem. PROCEDURES Meropenem-free polymethyl methacrylate and M-PMMA beads were sterilized by use of an autoclave or VHP or remained unsterilized. To determine the antimicrobial efficacy of each bead-sterilization combination (treatment), Mueller-Hinton agar plates were inoculated with 1 of 6 common equine pathogens, and 1 bead from each treatment was applied to a sixth of each plate. The zone of bacterial inhibition for each treatment was measured after 24 hours. To estimate the duration of antimicrobial elution into a solid or liquid medium, 1 bead from each treatment was transferred every 24 hours to a new Staphylococcus aureus–inoculated agar plate or a tube with PBS solution, and an aliquot of the eluent from each tube was then applied to a paper disc on an S aureus–inoculated agar plate. All agar plates were incubated for 24 hours, and the zone of bacterial inhibition was measured for each treatment. RESULTS In vitro antimicrobial efficacy of M-PMMA beads was retained following VHP sterilization. The duration of antimicrobial elution in solid and liquid media did not differ significantly between unsterilized and VHP-sterilized M-PMMA beads. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that M-PMMA beads retained in vitro antimicrobial activity and eluted the drug for up to 2 weeks after VHP sterilization.