| Abstract: | 24 seven-week-old hybrid healthy pigs (weighted 25.5?.4 kg ) from a source were randomly allotted to four groups (six each): the blank group, the negative group, the positive group and the test group. Pigs in the negative group and the test group were developed into a typical subacute Streptococcosis suis by inoculating subcutaneously 0.45 billion of pure living Streptococcus suis (type C55126) per kilogram body weight. Pigs in the positive group and the test group were intravenously injected ciprofloxacin (5 mg kg1 of BW) for 8 consecutive days (twice daily). Pigs in the blank group and positive group were inoculated with a placebo (0.85% NaCl). Some immunity parameters were tested on day 0, 7, 14, 21 and 28 after inoculation. Total leukocytes were counted with microscope. Differential leukocyte counts were performed on Giemsa-stained blood smears. The effect on the nitroblue tetrazolium (NBT) reduction of neutrophil was used to determine its phagocytic ability. Lymphocyte proliferation was determined by using the mitogens PHA. The total serum IgG concentration was measured by radial single immunodiffusion. A 50% hemolytic test was used to investigate the complement activity in serum. Whereas, a phytohemagglutinin (PHA) skin test was used to investigate in vivo immunity. We got the following results: Ciprofloxacin can retard the clinical signs of an increase of leukocyte counts, a large percent of lymphocytes and a relative percentage decrease of neutrophis. Ciprofloxacin could promote nitroblue tetrazolium (NBT) reduction by neutrophil. Though there was no obvious difference (P>0.05) between the test group and the negative group, the interaction of both Streptococcosis suis and ciprofloxacin was significantly different(P<0.01, on day 14, 21, 28 post-inoculation). The two factors enhanced NBT reduction by neutrophils of pigs in the test group in coordination (P<0.01, significantly higher than the blank group). In vitro proliferation to phytohemagglutinin (PHA) of lymphocytes from ciprofloxacin-treated diseased pigs was increased finally. Mean index, which was stimulated (SI) by PHA, of proliferation on lymphocytes in negative group, was significantly lower (P<0.01) than the blank group on days after inoculation, so do the SI of the test group on day 7, 14, 21 after inoculation. However, the drug increased the lymphocyte proliferation and led to the markedly higher response (P<0.01) in test group at the 28th day post-inoculation than the negative group, though there was no difference (P>0.05) between the test group and the blank group. Delayed-type hypersensitivity (DTH) to PHA was increased in diseased animals after receiving the treatment with ciprofloxacin. Owing to the difference of interaction (P<0.01, on day 21, 28 after inoculation), the DTH response was increased on the 21st day after inoculation (P<0.01. In comparison with both the negative group and the blank group). At the same time, the DTH response in negative group was lower than the blank group (P<0.05). The drug caused the decrease of IgG level in serum (P<0.05, on day 14 after inoculation, lower than the negative group). On day 14 after inoculation, the complement activity in se-rum in the test group was lower than the blank group (P<0.05), but on day 28, it was higher (P<0.05) than the negative group. |
