Schmitt C S, Halbur P G, Roth J A, Kinyon J M, Kasorndorkbua C, Thacker B
Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
Vet Microbiol. 2001 Jan 5;78(1):29-37. doi: 10.1016/s0378-1135(00)00289-3.
The objective of this research was to evaluate the efficacy of two antimicrobials (ampicillin and ceftiofur), a modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine, and low dose exposure to Streptococcus suis on disease associated with PRRSV/S. suis coinfection. Fifty-six, crossbred, PRRSV-free pigs were weaned at 10-12 days of age and randomly assigned to five treatment groups. All pigs were inoculated with 2ml of 10(6.4) TCID50/ml of high virulence PRRSV isolate VR-2385 intranasally at 29-31 days of age (day 0 of the study) followed 7 days later by intranasal inoculation with 2ml of 10(8.9)colony forming units(CFU)/ml S. suis type 2 isolate ISU VDL #40634/94. Pigs in group 1 (n=10) served as untreated infected positive controls. Pigs in group 2 (n=12) were treated with 5.0 mg/kg ceftiofur hydrochloride intramuscularly (IM) on days 8, 11, and 14. Pigs in group 3 (n=11) were treated with 11 mg/kg ampicillin IM on days 8-10. Pigs in group 4 (n=12) were vaccinated 14 days prior to PRRSV challenge with a commercial modified-live PRRSV vaccine. Pigs in group 5 (n=11) were exposed to a 1:100 dilution of the S. suis challenge inoculum 19 days prior to S. suis challenge. Mortality was 80, 25, 82, 83, and 36% in groups 1-5, respectively. The reduced dose S. suis exposure had some residual virulence, evidenced by S. suis induced meningitis in two pigs after exposure. Treatment with ceftiofur hydrochloride and reduced dose exposure to S. suis were the only treatments which significantly (P<0.05) reduced mortality associated with PRRSV/S. suis coinfection, significantly (P<0.05) reduced recovery of S. suis from tissues at necropsy, and significantly (P<0.05) reduced the severity of gross lung lesions.
本研究的目的是评估两种抗菌药物（氨苄青霉素和头孢噻呋）、一种猪繁殖与呼吸综合征病毒（PRRSV）的改良活疫苗以及低剂量接触猪链球菌对与PRRSV/猪链球菌混合感染相关疾病的疗效。56头无PRRSV的杂交仔猪在10 - 12日龄断奶，并随机分为五个治疗组。所有仔猪在29 - 31日龄（研究第0天）时经鼻接种2ml含10(6.4) TCID50/ml高毒力PRRSV毒株VR - 2385，7天后经鼻接种2ml含10(8.9)菌落形成单位（CFU）/ml的2型猪链球菌毒株ISU VDL #40634/94。第1组（n = 10）的猪作为未治疗的感染阳性对照。第2组（n = 12）的猪在第8、11和14天肌肉注射（IM）5.0mg/kg盐酸头孢噻呋进行治疗。第3组（n = 11）的猪在第8 - 10天肌肉注射11mg/kg氨苄青霉素进行治疗。第4组（n = 12）的猪在PRRSV攻毒前14天用市售的PRRSV改良活疫苗进行免疫接种。第5组（n = 11）的猪在猪链球菌攻毒前19天接触1:100稀释的猪链球菌攻毒接种物。第1 - 5组的死亡率分别为80%、25%、82%、83%和36%。低剂量猪链球菌接触具有一定残余毒力，证据是接触后有两头猪发生了猪链球菌诱导的脑膜炎。盐酸头孢噻呋治疗和低剂量猪链球菌接触是仅有的能显著（P<0.05）降低与PRRSV/猪链球菌混合感染相关死亡率、显著（P<0.05）降低尸检时从组织中分离出猪链球菌的数量以及显著（P<0.05）减轻肺部大体病变严重程度的治疗方法。
