弗氏柠檬酸杆菌对动物和人致病性研究进展

弗氏柠檬酸杆菌在自然界广泛分布,是一种典型的人-畜-鱼共患病条件性致病菌,一般情况下不引起动物和人发病。近年来,陆续有报道弗氏柠檬酸杆菌强毒株也能引起动物败血症甚至急性死亡,且对水产动物的致病报道较多。人类可因弗氏柠檬酸杆菌感染而发生腹泻、食物中毒和继发感染。弗氏柠檬酸杆菌引起动物和人感染时有携带如β-内酰胺酶等新型耐药基因的可能,且发现有cfa、ST和SLT等多种毒力因子。综合研究表明弗氏柠檬酸杆菌可能是一种尚未被人们充分认识的病原菌,且有危害加重的趋势。因此,在动物和人类疾病防治中不能忽视弗氏柠檬酸杆菌。论文主要阐述了弗氏柠檬酸杆菌对动物和人的致病性方面取得的进展,旨在引起研究者对弗氏柠檬酸杆菌致病性的重视,并展望了弗氏柠檬酸杆菌未来研究的方向。     

一株弗氏柠檬酸杆菌的分离鉴定及致病性研究

为确定导致罗非鱼患病的原因,本试验对濒临死亡的罗非鱼进行无菌解剖,从心脏部位分离得到1株细菌,通过形态学观察、生理生化鉴定和16S rDNA分析,确定菌株为弗氏柠檬酸杆菌（Citrobacter freundii）。药敏试验结果显示,该菌株具有很强的多重耐药性,测试的20种药物中,该菌株对恩诺沙星、青霉素等13种药物具有完全耐药性,仅对头孢曲松、头孢他啶、头孢拉定、哌拉西林、舒巴坦5种药物敏感。人工感染试验结果显示,该菌对草鱼、黄颡鱼、罗非鱼、禾花鲤具有较强的致病性。本试验结果阐明了罗非鱼患病的原因,同时在养殖过程中可指导养殖户合理用药。     

鲫鱼弗氏柠檬酸杆菌的耐药表型及耐药基因检测

为了检测鲫鱼费氏柠檬酸杆菌的耐药表型及耐药基因,试验采用标准Kirby-Bauer纸片扩散法检测鲫鱼弗氏柠檬酸杆菌对13种抗生素的耐药表型,并用PCR法检测弗氏柠檬酸杆菌对四环素类和磺胺类抗生素的6种耐药基因(tetA、tetC、tetM、Sul1、Sul2和Sul3)。结果表明:鲫鱼弗氏柠檬酸杆菌对四环素、氨苄西林、强力霉素、红霉素、头孢拉定和阿莫西林耐药;仅检测出四环素类的tetA和tetM基因,而其他未检测出。     

Ichthyosis in two dogs.

Ichthyosis in 2 dogs was characterized by extreme hyperkeratosis on all or part of the skin and by extreme thickening of the digital and metapodial pads. The skin disorder closely resembled human lamellar ichthyosis, in which the histologic features include a thickened granular layer, mitotic figures, and dense collections of coarse keratohyaline granules. The disease was believed to be inherited, probably autosomal recessive, inasmuch as none of the parents was affected. Treatment of 1 dog with 5% lactic acid in hydrophilic ointment reduced the hyperkeratosis and decreased the shedding of scales.     

Lidocaine treatment of dogs with Escherichia coli septicemia

Effects of lidocaine on organ localization of neutrophils and bacteria and on hemodynamic and metabolic variables were determined during septic shock in dogs. Twelve anesthetized dogs were infused with 10(10) Escherichia coli/kg of body weight through a portal vein catheter over a 1-hour period. Six of these 12 dogs were treated with 2 mg of lidocaine HCl/kg (6 mg/kg/h) 15 minutes after the bacterial infusion had begun. Six dogs not given E coli (surgical controls) were given saline solution at the same rate as the bacterial and lidocaine infusions. Over 4 hours, nontreated dogs with septicemia developed systemic hypotension, decreased cardiac output, increased portal pressure, increased serum alanine transaminase activity, increased liver extravascular water, increased liver glycogen depletion, and decreased PaO2, compared with control dogs. Accumulations of polymorphonuclear leukocytes and E coli were found in the liver and lungs of dogs with septicemia. Lidocaine treatment did not alter the hemodynamic measurements and resulted in metabolic acidosis and hypoalbuminemia. Decreased numbers of E coli were recovered from the liver of lidocaine-treated dogs, whereas increased numbers of organisms were recovered from the blood. Neutrophil sequestration was increased in the liver, but not the lungs of lidocaine-treated dogs.     

Nondiabetic emphysematous cystitis in two dogs.

Emphysematous cystitis unassociated with diabetes mellitus was diagnosed in two dogs. One dog had chronic recurring urinary tract infection with aerobic and anaerboic bacteria, and the other had urinary tract infection associated with renal glucosuria. In both dogs, the cystitis was resolved with appropriate antibacterial therapy.     

Cranial thoracic diskospondylitis in two dogs.

Cranial thoracic diskospondylitis was diagnosed in 2 dogs. Staphylococcus aureus was isolated from the vertebral lesion of both dogs, from the urine of one dog, and from the blood of the other dog. In each case, curettage of the affected disk and contiguous vertebrae was accomplished via thoracotomy. Both dogs recovered following curettage and antibiotic therapy.     

Anaerobic bacterial pneumonia with septicemia in two racehorses

Anaerobic bacterial pneumonia with septicemia was diagnosed in 2 Thoroughbred racehorses referred with respiratory tract disease that had failed to respond to initial treatment with various antibiotics including penicillin and trimethoprim-sulfamethoxazole. Multiple anaerobic organisms, including Bacteroides spp and Fusobacterium spp, were isolated from blood and transtracheal aspirates obtained from both horses and from aspirates of cutaneous nodules obtained from 1 horse. The latter horse responded to metronidazole treatment followed by procaine penicillin G administration and regained its health over the following 6 months. The other horse did not respond as favorably to a similar antibiotic regimen and died following an acute episode of pulmonary hemorrhage after remaining intermittently febrile for 7 weeks. Although in vitro antimicrobial susceptibility tests indicated that all anaerobic organisms isolated from both horses were susceptible to penicillin, the infection in these horses responded poorly to initial treatments with this drug. We speculated that adequate penicillin concentration was not attained in the deep foci of infection in the lungs. Animals with anaerobic bacterial infections that fail to respond to penicillin or from which penicillin-resistant anaerobes are isolated may benefit from treatment with metronidazole.     

Phycomycosis in fifteen dogs and two cats.

Phycomycosis was confirmed by histologic examination of biopsy specimens from 15 dogs and at necropsy in 2 cats. The fungal infections occurred most frequently in young adult dogs (1-3 yr) of the larger breeds. The gastrointestinal tract was the organ most commonly involved. Treatment by surgical excision, amphotericin B, and sodium iodide alone or in combination was attempted in five cases. Mortality was 100%.     

Spontaneous aortic dissecting hematoma in two dogs.

This report describes 2 cases of spontaneous aortic dissecting hematoma in young Border Collie and Border Collie crossbred dogs. Histology was performed in one of the cases involving an unusual splitting of the elastin present within the wall of the aorta, consistent with elastin dysplasia as described in Marfan syndrome in humans. The first case involved a young purebred Border Collie that died suddenly and the second case involved a Border Collie crossbred dog that died after a 1-month history of seizures. Gross lesions included pericardial tamponade with dissection of the ascending aorta in the former case and thoracic cavity hemorrhage, mediastinal hematoma, and aortic dissection in the latter. Histologic lesions in the case of the Border Collie crossbred dog included a dissecting hematoma of the ascending aorta with elastin dysplasia and right axillary arterial intimal proliferation.     

Accessory carpal bone displacement in two dogs.

The diagnosis and treatment of luxation of the accessory carpal bone in a racing greyhound, and subluxation of the same bone in a lurcher, are described. The injury in the lurcher occurred in both carpi, but on separate occasions. Both dogs had severe thoracic limb lameness with marked carpal swelling. The diagnosis of luxation was obvious from carpal radiographs. The subluxations were difficult to detect on palpation, but were suspected and confirmed on exploratory surgery, which showed an avulsion of the lateral support structures of the accessory carpal bone from the distal ulna. Pancarpal arthrodesis with accessory carpal bone excision undertaken in the greyhound was successful. Following repair of the torn ligaments, the lurcher returned to full activity without lameness before sustaining the same injury to the other carpus. The anatomy of the accessory carpal support structures and the aetiology of the injuries are discussed.     

Massive envenomation by Vespula spp. in two dogs.

Two dogs, a 5 year old golden retriever and a 5 year old yellow Labrador, were stung by numerous yellow jackets (Vespula sup.). Both dogs exhibited signs consistent with direct toxic effect of the wasp venom. The laborador was more severely affected, and was euthanized less than 24 hours after after admission. On postmorten, changes were seen that were consistent with anaphylaxis and disseminated intravascular coagulation. The golden retriever, although exhibiting respiratory distress, prolongation of coagualtion, and increased liver enzymes, eventually made a full recovery.     

Pseudogout in two dogs

Extract

Pseudogout is a common condition in elderly people in which sudden onset of intense joint pain and synovitis develop. Peri-synovial calcium crystal deposition is the cause of the synovitis rather than the uric acid deposition in common gout. It is a rare condition in dogs, having only been reported twice before. Two dogs presenting with acute lameness and pyrexia showed many macrophages and occasional neutrophils containing intracellular crystals on cytological examination of synovial fluid. The crystals were single or multiple, small to large, clear, square or rhomboid-shaped, weakly birefringent and resembled those described for pseudogout. Occasional crystals were also present free in the matrix. Non-steroidal anti-inflammatory drugs that are effective in reducing pain in people with pseudogout provided no relief to either patient, but twice daily oral prednisolone therapy was successful. Dosage was gradually tapered as clinical signs improved over a period of 6 weeks.     

In vitro inhibition of Citrobacter freundii, a red-leg syndrome associated pathogen in raniculture, by indigenous Lactococcus lactis CRL 1584

Red-leg syndrome (RLS) is one of the main infectious diseases that cause economic losses in Lithobates catesbeianus hatcheries, Citrobacter freundii being an etiological agent. Treatment or prevention with therapeutics or chemicals results in modifications of the indigenous microbiota, development of antibiotic resistance, presence of their residues in food and enhancement of production costs. Thus, probiotics could be used as an alternative therapy. Lactic acid bacteria are part of the indigenous microbiota of healthy frogs and can prevent pathogen colonization by different mechanisms, including the production of antagonistic substances. In this work, the evaluation and characterization of the inhibition of C. freundii CFb by Lactococcus lactis subsp. lactis CRL 1584, a potentially probiotic candidate, were carried out. This strain produced lactic acid, H(2)O(2) and bacteriocin in static and shaken conditions and inhibited pathogen growth in associative cultures, with an earlier inhibition under agitated conditions. The elimination of each of the antimicrobial metabolites partially abolished the inhibition of the pathogen, suggesting that the inhibitory effect could be attributed to a combined action of the three antagonistic molecules. Electron microphotographs revealed the damage caused by L. lactis CRL 1584 supernatants to C. freundii cells. The addition of pure lactic acid, H(2)O(2) and bacteriocin to the culture media showed that each metabolite caused different morphological modifications in C. freundii, in agreement with the effect on viable cell counts. The results support the possibility that L. lactis CRL 1584 might be considered as a probiotic to be used in the prevention of RLS in raniculture.