紫色色杆菌感染小熊猫引起肺炎的临床调查

Clinical investigation of pneumonia in the red panda (Ailurus fulgens) caused by the non-pigmented strain of Chromobacterium violaceum

本文报道了福州大熊猫研究中心小熊猫感染紫色色杆菌引起肺炎的群发病例。7只小熊猫中,出现以呼吸衰竭为主要临床症状的3只小熊猫在发病3 d内全部死亡,病死率100%。死亡的小熊猫解剖病变为气管内有白色泡沫样分泌物,肺有化脓性坏死并严重淤血;胸腔,心包积液且胸水浑浊;肝脏呈弥漫性空泡变性,淤血和散在局灶性坏死。通过流行病学调查,病理解剖观察,细菌分离培养和鉴定及动物回归试验,诊断为紫色色杆菌无色变种感染。根据GenBank数据库提供的紫色色杆菌16S RNA基因序列,设计一对引物(5’GAG CAAACA GGA TTA GAT ACC 3’;5’TTA CGG TTA CCT TGT TAC GAC 3’),获得目的基因片段739 bp,将核苷酸序列测定的结果与GenBank数据库提供的7株紫色色杆菌进行同源性比较。分离的菌株(FJ08A)与CV09株、ES-BV4400株同源性均为98.8%,与AY117554株、EAV2株、AJ871127株、LMG3953株、JS1株同源性分别为98.2%、98.0%、94.9%、93.1%、92.8%。依据调查结果和药物敏感试验,对其余4只未发病的小熊猫采取肌肉注射头孢哌酮钠和口服复方新诺明进行预防性治疗,效果良好,未有新病发生。结果表明:(1)紫色色杆菌是革兰氏阴性菌,致病性强,致死率高,腹腔注射分离的紫色色杆菌菌液导致接种小白鼠在2～3 d内全部死亡。小熊猫感染后,发病迅速,致死率高,应引起重视;(2)紫色色杆菌是一种条件致病菌,外伤感染是主要致病因素。

This clinical investigation reports several cases of pneumonia in the red panda（Ailurus fulgens） which occurred at Fuzhou Giant Panda Research Center in July,2008.Among 7 infected animals,3 red pandas died within 3 days after showing symptoms of high fever and severe respiratory disease.Necropsy results showed a white foamy discharge in the trachea;suppurative necrosis and massive congestion in the lung;turbid pleural and pericardial effusions;a liver with multiple atrophic foci and focal congestive necrosis.Through bacterial isolation and identification,the pathogen was confirmed to be non-pigmented Chromobacterium violaceum.Based on GenBank database of 16S RNA gene sequences for Chromobacterium violaceum,primer pairs（5＇ GAG CAA ACA GGA TTA GAT ACC 3＇;5＇ TTA CGG TTA CCT TGT TAC GAC 3＇） were designed to amplify a 739 bp gene fragment by PCR.The nucleotide sequences obtained subsequently were compared to seven strains of Chromobacterium violaceum from the GenBank database and found to be 98.8% identical to strains CV09 and ESBV4400 as well as 98.2%,98.0%,94.9%,93.1% and 92.8% identical to strains AY117554,EAV2,AJ871127,LMG3953 and JS1,respectively.Intraperitoneal inoculation of 5 mice with the isolated pathogen culture resulted in the death of all mice within 2-3 days,a reflection of the virulence of this isolate.Several measures were implemented to control the spread of infection including disinfecting of the grounds,housing environment,and water supply.We further tested the clinical isolate for antibiotic susceptibility and based on these findings,the 4 remaining asymptomatic pandas were all treated twice daily intramuscularly with Cefoperazone sodium for two days in combination with oral dosing of Sulfamethoxazole twice a day for four days,and no new case was seen after the treatments.This investigation indicates that the rapid onset of infection and high fatality rate of Chromobacterium violaceum in the red panda should be noted and we conclude that trauma or injury to these animals in combination with pathogen contaminated surroundings and water supplies are the main reasons for onset of the infection.