Dietary propionic acid enhances antibacterial and immunomodulatory effects of oxytetracycline on Nile tilapia, Oreochromis niloticus.

This study was carried out to evaluate the potential antibacterial and immunomodulatory effects of the dietary acidifier propionic acid (PA) when given alone or in combination with oxytetracycline (OTC) on Nile tilapia (Oreochromis niloticus). Apparently healthy O. niloticus (n = 240; 52 ± 3.75 g) were randomly allocated into four equal groups (n = 60/group): control group fed a basal diet alone and the other three groups fed basal diets supplemented with either PA (200 mg /kg of diet, PA group) or OTC (500 mg/kg of diet, OTC group) alone or in combination (PA + OTC group). Each group was subdivided into two subgroups (n = 30/subgroup, each subgroup had triplicate of 10 fish); subgroup (A) was used to evaluate the antibacterial effects with the aforementioned 2 weeks feeding regime, and subgroup (B) was used to evaluate the immunomodulatory effects against Aeromonas hydrophila infection with similar 2 weeks feeding regime. Among the four groups, PA + OTC group showed the highest significant (p < 0.0001) antibacterial activity as indicated by widest inhibition zones against A. hydrophila and lowest total gastrointestinal bacterial counts. Additionally, this group had the best immunomodulatory effect as noticed by a significant (p < 0.05) increase in total serum protein, globulin, IgM, phagocytic activity and index, lysosome activity, and significant (p < 0.05) upregulation in the expression levels of immunity-related genes (MHC I, MHC IIA, MHC IIB, Tlr7, IgM heavy chain, TNFα, and IL1ß) in head-kidney. Notably, the combined dietary PA and OTC improved the hematological parameters and reduced the oxidative damage of hepatopancreas and head-kidney induced by OTC. This data suggests dietary PA as potential adjuvant to OTC in O. niloticus diets to get maximal antibacterial and immunomodulatory effects.

Validation of the BetaStar® Advanced for Tetracyclines Test Kit for the Screening of Bulk Tank and Tanker Truck Milks for the Presence of Tetracycline Drug Residues.

A validation study was conducted for an immunochromatographic method (BetaStar® Advanced for Tetracyclines) for detection of tetracycline antibiotic residues in raw, commingled bovine milk. The assay was demonstrated to detect tetracycline, chlortetracycline, and oxytetracycline at levels below the FDA tolerance levels but above the maximum sensitivity thresholds established by the National Conference on Interstate Milk Shipments. Results of internal and independent laboratory dose-response studies employing spiked samples were in agreement. All three drugs at the approximate 90/95% sensitivity levels were detected in milk collected from cows that had been treated with the specific drug. Selectivity of the assay was 100%, as no false-positive results were obtained in testing 881 control milk samples. Testing the estimated 90/95 sensitivity level for tetracycline (213 ppb), chlortetracycline (272 ppb), and oxytetracycline (180 ppb) and at 1000 ppb for each antibiotic resulted in 100% positive tests for each tetracycline. Results of ruggedness experiments established the operating parameter tolerances for the test. Results of cross-reactivity testing established that the assay detects certain other tetracycline drugs but does not cross-react with any of 32 drugs belonging to seven different drug classes. Abnormally high bacterial or somatic cell counts (SCC) in raw milk produced no assay interference.

Protective effect of propolis against oxidative stress and immunosuppression induced by oxytetracycline in rainbow trout (Oncorhynchus mykiss, W.).

The aim of this study was to investigate the effects of propolis on oxytetracycline (OTC)-induced oxidative stress and immunosuppression in fish. OTC (100 mg per kg⁻¹ body weight) was orally administered to fish for 14 days. A significant elevation in the level of malondialdehyde, as an index of lipid peroxidation, and reductions in antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase) and low molecular weight antioxidant (reduced glutathione) levels were observed in the blood, liver, kidney, spleen, and heart tissues of OTC-treated fish. OTC also had a suppressive effect on specific and non-specific immune system parameters, such as leucocyte counts, oxidative radical production (nitrobluetetrazolium activity), total plasma protein and immunoglobulin levels, and phagocytic activity. Pre-treatment, post-treatment, and simultaneous treatment with propolis (50 mg per kg⁻¹ body weight, orally) attenuated the OTC-induced oxidative stress by significantly decreasing the levels of malondialdehyde in tissues. In addition, propolis significantly increased the level of reduced glutathione and the catalase, glutathione peroxidase, and superoxide dismutase activities. Upon the administration of propolis, the suppressed immune system parameters were significantly increased in fish treated with OTC. The present results suggest that pre-treatment, post-treatment, and simultaneous administration of propolis might alleviate OTC-induced oxidative stress and immunosuppression.

Microarray analyses of shrimp immune responses.

Shrimp aquaculture is one of the major foodproducing industries in the world. However, it is being impacted by several problems including diseases, antibiotic use, and environmental factors. The extent of the effects of these problems in the immune system of the shrimp at the molecular level is just beginning to be understood. Here, we review the gene expression profile of shrimp in response to some of these problems using the high-throughput microarray analysis, including white spot syndrome virus, yellow head virus, Vibrio spp., peptidoglycan, oxytetracycline, oxolinic acid, salinity, and temperature.

Growth performance and immune response of two commercial broiler strains fed diets containing Lactobacillus cultures and oxytetracycline under heat stress conditions.

1. Hubbard x Hubbard (HH) and Shaver x Shaver (SS) chicks given a dietary supplement of either 50 mg/kg oxytetracycline (OTC) or 1 g/kg Lactobacillus culture (LC) were exposed to 36 +/- 1 degrees C for 3 h daily from day (d) 21 to 42. 2. Prior to heat treatment, body weight (d 21) and weight gain (d 1 to d 21) of OTC and LC birds were greater than those fed the control diet. Chicks given LC had the best food efficiency followed by OTC and control birds during d 1 to d 21. Body weight (d 1 and d 21) and weight gain (d 1 to d 21) were greater for HH tlhan SS chicks. 3. After 3 weeks of heat exposure, birds receiving the LC diet had greater body weight and weight gain, higher food intake and lower food efficiency than OTC and control chicks. 4. Antibody production against Newcastle discase vaccine on d 21 was not affected by strain or diet. On d 42, while diet had negligible effect on this variable among the SS broilers, HH birds fed LC had higher antibody production than those on the control diet. 5. Neither strain nor diet had a significant effect on mortality.

Antimicrobial resistance of enteropathogenic Escherichia coli strains from a nosocomial outbreak in Kenya.

The majority of the 78 enteropathogenic (EPEC) and the 151 non-EPEC Escherichia coli strains isolated from preterm neonates during an outbreak of gastroenteritis in a hospital in Nairobi, Kenya, were resistant to trimethoprim-sulfamethoxaxole, chloramphenicol, oxytetracycline and ampicillin, but only a few strains were resistant to cefazolin, cefamandole, cefotaxime, amikacin and nalidixic acid. Fourteen different antimicrobial resistance patterns were observed in the 229 strains of E. coli analysed. Eighty-two percent of the EPEC strains belonged to two resistance pattern compared with 79% of non-EPEC strains which exhibited three resistance patterns. There was no consistent relationship between plasmid profile group and antimicrobial resistance pattern, although one resistance pattern was more frequently observed in EAF-positive strains belonging to the dominant plasmid profile group. Nine percent of the EPEC strains were resistant to gentamicin compared to 37% in the non-EPEC group. No correlation was observed between administration of gentamicin and percentage of resistant strains isolated. None of the nine neonates receiving gentamicin died during the outbreak. Gentamicin resistance was observed in E. coli strains from six out of these nine neonates. Five out of fourteen neonates who received other antimicrobials, or no antibiotic treatment at all, died.

Protection of cattle against heartwater in Botswana: comparative efficacy of different methods against natural and blood-derived challenges.

Five groups of Tswana-cross castrated male cattle between 20 and 30 months of age (a total of 158 animals) were transported from a ranch in a heartwater-free area of south Botswana to a feedlot near Gaborone in the east of Botswana where heartwater is endemic. On arrival, one group was vaccinated intravenously with the Onderstepoort sheep blood heartwater vaccine, one group was vaccinated intravenously with the new Onderstepoort tick-derived heartwater vaccine and a third group was vaccinated subcutaneously with this tick-derived vaccine. Vaccine reactions were blocked with long acting oxytetracycline on the first day of fever. A fourth group had a series of injections of long acting oxytetracycline on days 0, 7, 14 and 21 after arrival, and a fifth served as untreated controls. The animals remained at the feedlot for 65 days during which time they faced a low level of challenge by Amblyomma hebraeum ticks. None contracted heartwater and so they were then challenged, together with a further group of control cattle, with a dose of the sheep blood vaccine. Some animals in all groups had severe heartwater reactions and died despite therapy, but 76.7 per cent, 64.5 per cent and 74.3 per cent of the cattle in the blood vaccine, intravenous tick vaccine and long acting oxytetracycline groups respectively were resistant to challenge, compared with 48.3 per cent of the subcutaneous tick vaccine group and 36.4 per cent of the controls. It was concluded that intravenous vaccination of susceptible adult cattle with either the blood or the tick-derived vaccine needs careful monitoring in the month after vaccination and does not necessarily result in immune animals.(ABSTRACT TRUNCATED AT 250 WORDS)

[T- and B-lymphocyte count in the spleen and lymph nodes of guinea pigs administered oxytetracycline intramuscularly]. / Kolichestvo T- i B-limfotsitov v selezenke i limfaticheskikh uzlakh morskikh svinok v uslovii vnutrimyshechnogo vvedeniia oksitetratsiklina.

The E and EAC rosette formation tests, carried out in order to determine the count of T and B lymphocytes in the spleen and lymph nodes of guinea pigs after several intramuscular of oxytetracycline, showed a decrease in the ability of B lymphocytes in the reaction of EAC rosette formation with the simultaneous rise of the level of "zero" cells without surface receptors characteristic of T and B lymphocytes. The data obtained in this study indicated the possibility for tetracyclines to effect the differntiation and ripening of the medullary precursors of B lymphocytes.

[Distribution and binding of oxytetracycline in the body of immunized animals]. / Raspredelenie i sviazyvanie oksitetratsiklina v organizme immunizirovannykh zhivotnykh

Distribution and binding of oxytetracycline in immunized animals at various periods of immunogenesis (5, 10, 15, 20, 30 and 90 days after vaccination) were studied on rabbits, using dry live brucellosis vaccine, strain 19 as the antigen. The results of the study showed that immunological reconstruction of the macroorganism, its protective forces had a definite effect on the character of distribution, absorption and levels of oxytetracycline, as well as the processes of the antibiotic binding in the organism. The changes were indirect dependence on the immunogenesis periods: at the beginning of immunogenesis there was some increase in the antibiotic levels, as well as increased binding of the drug in the organs where reconstruction, activation and hyperplasia of the lymphoreticular cells occurred. During the productive phase of the antigen formation the antibiotic levels were 1,5-2 times lower, however, the processes of the antibiotic binding were more pronounced in the organs, where immunocompetent cells and antibodies were synthesized. During extinction of immunogenesis reduction of the initial antibiotic levels was recorded. Therefore, the changes directly depended on the periods of immunogenesis.

[Tetracycline distribution in the body of animals and its effect on cellular interaction in the immune response]. / Raspredelenie tetraysiklinov v organizme zhivotnykh i vliianie ikh na vzaimodeistvie kletok v immunnom otvete

Distribution of tetracyclines and their effect on interaction of the cells in the immune response were studied on pigs and rabbits non-vaccinated, immunized with formolvaccin against paratyphoid fever and experimentally infected with the paratyphoid causative agent. It was found that oxytetracycline and tetracycline administered parentally to the animals formed complexes with the proteins and especially with albumins and gamma-globulins, were rapidly adsorbed by the lymphocytes and consumed by the cells of the reticulo-macro- and micro-phage systems, epithelium of the kidney cannaculi and the cells of the liver parenchyma. Immunomorphological changes accompanied by formation of antibodies to the antibiotics were found in the bloodforming-lymphoid system after repeated parental administrations of the tetracyclines. The titers of the antibodies to oxytetracycline and tetracycline were high by the 5th--14th day after the antibiotic administration and the relatively high levels persisted for 1.5 months. The use of tetracyclines during the induction stage of immunogenesis had a pronounced inhibitory effect on development of immunity against the paratyphoid fever antigen. On the basis of the tetracycline capacity for binding with immunoglobulins and intensive adsorption by the lymphocytes it is possible to suppose that the inhibitory effect of the antibiotics on immunogenesis was connected with their blocking the receptors of T- and B-lymphocytes.

Lymphocyte transformation test in fixed drug eruption.

Twenty-one patients with fixed drug eruption were studied with the lymphocyte transformation test. In no patient was there blast transformation when the responsible drug (1:10,000 dilution) was added to the lymphocyte culture. The addition to the lymphocyte culture of 0.4 ml of autologous serum, taken at the acme of the clinical reaction, produced blast transformation of the lymphocytes, and when the responsible drug (1:10,000 dilution) was added to this system, blast transformation increased by several times. The addition of the responsible drug to autologous serum obtained during clinical remission produced a minimal or negative response. These findings suggest that during fixed drug eruptions a blast transforming factor appears temporarily in the serum and increases its activity in the presence of the responsible drug. This factor spontaneously diminishes or disappears a few days after clinical exacerbation.