Streptococcus Suis: Past and Present

Staats, J.J., Feder, I., Okwumabua, O. and Chengappa, M.M., 1997. Streptococcus suis: past and present. Veterinary Research Communications, 21 (6), 381-407Steptococcus suis is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. In swine, the disease has spread worldwide but is more prevalent in countries with intensive swine management practices. The disease syndromes caused by S. suis in swine include arthritis, meningitis, pneumonia, septicaemia, endocarditis, polyserositis, abortions and abscesses. S. suis has also been implicated in disease in humans, especially among abattoir workers and swine and pork handlers. In humans, S. suis type 2 can cause meningitis, which may result in permanent hearing loss, septicaemia, endocarditis and death. The pathogenic mechanism of S. suis is not well defined. Several virulence factors have been identified, but their roles in pathogenesis and disease have not been well elucidated. Much work is in progress on characterization of virulence factors and mechanisms, with emphasis on the control of the disease. Because of the non-availability of suitable immunoprophylaxis, control of S. suis infection has depended mainly on the use of antimicrobials.     

Efficacy of tiamulin against experimentally induced Streptococcus suis type-2 infection in swine

Eighteen 4-week-old pigs were used in a study to evaluate tiamulin in drinking water for control of experimentally induced Streptococcus suis type-2 infection. Pigs in groups A and B (n = 6 pigs/group) were aerosolized with a logarithmic-growth phase culture of S suis type 2, whereas pigs in group C (n = 6 pigs) served as noninfected and nonmedicated controls. After exposure to S suis, pigs in group B were given 180 mg of tiamulin/L of drinking water for 5 days. Pigs in group B consumed more feed (P = 0.009) and gained body weight faster (P = 0.02) than did pigs in group A. Pigs in group A had higher rectal temperature (P = 0.05) for up to 7 days after S suis exposure, higher clinical sign scores (P = 0.008), higher serum cortisol concentration on days 7 and 14, higher gross lesion scores (P = 0.03), and higher microscopic lesion scores (P = 0.01) than did pigs in groups B and C. Gross and microscopic lesions in pigs of groups A and B included meningitis, pneumonia, pleuritis, pericarditis, peritonitis, and synovitis of variable severity. Streptococcus suis type 2 was recovered from tissue specimens of 2 group-A pigs and 1 group-B pig. Data indicated that tiamulin administered via drinking water significantly reduced the effects of S suis type-2 infection.     

Isolation of Clostridium perfringens from neonatal calves with ruminal and abomasal tympany, abomasitis, and abomasal ulceration

Eight neonatal calves (2 to 21 days old) with suspected abomasal displacement or intestinal obstruction after acute onset of abdominal tympany, colic, depression, or death were referred to Kansas State University for clinical examination or for necropsy. Results of routine hematologic and serum chemical analyses did not reveal consistent changes. Necropsy revealed abomasal distention, with various degrees of abomasitis, hemorrhage, and ulceration, but did not reveal evidence of displaced abomasum or obstructed intestine. Specimens of ruminal contents collected via stomach tube or at necropsy and abomasal contents collected at necropsy were obtained for anaerobic bacteriologic culture. Clostridium perfringens was isolated from all specimens, and on the basis of toxin neutralization tests in mice, 7 were type A and one was type E. Copper concentrations in serum and tissues were within normal limits. It appeared that the acute abdominal syndrome in these neonatal calves was unrelated to copper deficiency, and that C perfringens, particularly type A, may have had an appreciable contributory role in its pathogenesis.     

Improved method for obtaining streptomycin-dependent mutants from Pasteurella multocida and Pasteurella haemolytica, using N-methyl-N'-nitro-N-nitrosoguanidine.

N-Methyl-N'-nitro-N-nitrosoguanidine was used in a modified and improved procedure to obtain streptomycin-dependent mutants of type A Pasteurella multocida and type 1 Pasteurella haemolytica. The relative virulence of these mutants was determined by mouse inoculation with and without streptomycin.     

Factors affecting the leukotoxin activity of Fusobacterium necrophorum.

The effect of cultural conditions on the production of leukotoxin by biotypes A and B of F. necrophorum was investigated. Biotypes A and B were grown in prereduced, anaerobically sterilized, brain-heart infusion (BHI) broth. The average leukotoxin titer of culture supernatant was 18 times higher from biotype A strains than from biotype B strains. Leukotoxin activity peaked during the late-log and early-stationary phases of growth, then declined precipitously in both biotypes. F. necrophorum biotype A was grown in different media (BHI, liver infusion, and Eugon broths), at various pH (6.6, 7.3, 7.7, and 8.2), incubation temperatures (30, 35, 39, and 43 degrees C), redox potentials (-352 to +375 mV), and iron concentrations (less than 0.2, 4.2, 42.1, and 361.4 microM). Anaerobic BHI broth with pH from 6.6 to 7.7 at 39 degrees C incubation temperature supported maximal F. necrophorum growth and leukotoxin production. The optimum redox potential for F. necrophorum growth was in the range of -230 to -280 mV. However, the presence of titanium III citrate or dithiothreitol (7.78 mM) in the medium decreased (P less than 0.05) the leukotoxicity of F. necrophorum. Low iron concentration (less than 0.2 microM) decreased (P less than 0.05) growth rate but not leukotoxin activity of F. necrophorum, whereas high iron concentration inhibited the leukotoxin activity.     

Field-trial evaluation of a Pasteurella vaccine in preconditioned and nonpreconditioned lightweight calves

A field-trial evaluation confirmed the efficacy of a pasteurella vaccine as a means of preventing bovine pneumonia. The vaccine was comprised of streptomycin-dependent Pasteurella multocida (type A:3) and Pasteurella haemolytica (type 1). Vaccinal efficacy was defined in terms of greater body weight gains, less severe clinical signs of pneumonia, and smaller death rates as compared with the same factors in nonvaccinated calves. During the 50-day trial, vaccinated calves gained weight faster than did nonvaccinated calves (P = 0.05). Economic advantage was not found for administering a booster dose of the vaccine (P = 0.25). Nonpreconditioned nonvaccinated calves made greater dollar profits than did preconditioned nonvaccinated calves (P = 0.16). A comparison of all preconditioned calves with all nonpreconditioned calves revealed that illness and death losses were less in the preconditioned calves (P = 0.07). An evaluation of the cost vs benefit factors revealed significant advantages for administering 1 dose of vaccine of $19.08 for a preconditioned calf (P = 0.006) and of $11.39 for a nonpreconditioned calf (P = 0.05). The data indicated that there was no economic advantage for preconditioning and that the greatest economic gain was made by the vaccinated nonpreconditioned calves.     

Fusobacterium necrophorum infections: Virulence factors,pathogenic mechanism and control measures

Fusobacterium necrophorum, a Gram-negative, non-spore-forming anaerobe, is a normal inhabitant of the alimentary tract of animals and humans. Two types of F. necrophorum, subspecies necrophorum (biotype A) and funduliforme (biotype B), have been recognized, which differ morphologically, biochemically, and biologically. The organism is an opportunistic pathogen that causes numerous necrotic conditions (necrobacillosis) such as bovine hepatic abscesses, ruminant foot abscesses and human oral infections. The pathogenic mechanism of F. necrophorum is complex and not well defined. Several toxins, such as leukotoxin, endotoxin, haemolysin, haemagglutinin and adhesin, have been implicated as virulence factors. Among these, leukotoxin and endotoxin are believed to be more important than other toxins in overcoming the host's defence mechanisms to establish the infection. F. necrophorum is encountered frequently in mixed infections and, therefore, synergisms between F. necrophorum and other pathogens may play an important role in infection. Several investigators have attempted to induce protective immunity against F. necrophorum using bacterins, toxoids, and other cytoplasmic components. Generally, none of the immunogens has afforded statisfactory protection against Fusobacterium infections. Because of the unavailability of suitable immunoprophylaxis, the control of F. necrophorum infection has depended mainly on the use of antimicrobial compounds.Abbreviations CFU colony-forming units - DNA deoxyribonucleic acid - DNase deoxyribonuclease - Eh redox potential - ELISA enzyme-linked immunosorbance assay - LPS lipopolysaccharide - MPN most-probable number - PMN polymorphonuclear cells - rRNA ribosoma ribonucleic acid - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - subsp. subspecies     

Detection of Escherichia coli Shiga toxin (stx) and enterotoxin (estA and elt) genes in fecal samples from non-diarrheic and diarrheic greyhounds

Virulence factors responsible for acute diarrhea in greyhounds have not been well established. The objective of this study was to determine if a correlation exists between disease and the presence of the Escherichia coli toxin genes in non-diarrheic and diarrheic greyhound feces. DNA extracted from broth cultures was evaluated for the presence of Shiga toxin and enterotoxin genes and broth samples were evaluated for Shiga toxin and heat-labile enterotoxin. Shiga toxin (stx1 and stx2) and enterotoxin (et and estA) genes were identified in both non-diarrheic and diarrheic samples after in vitro cultured of swabs at 37 degrees C for 16-24h. The stx1 gene was present in 3% of non-diarrheic and 15% diarrheic samples and the stx2 gene was identified in 36 and 23%, non-diarrheic and diarrheic samples, respectively. Shiga toxin was present in 48% diarrheic and 25% of the non-diarrheic in vitro cultured samples. The elt gene was detected in vitro cultured swabs in 12% of the non-diarrheic and 7% of the diarrheic samples. Labile toxin was present in the feces of small numbers of both groups of dogs. A significant correlation existed between the presence of both stx1 genes and Shiga toxin in feces, and lack of disease in non-diarrheic (P=0.01) and presence of disease in diarrheic (P=0.024) greyhounds. Correlation between production of Shiga toxin and detection of stx1 or stx2 was significant in both the diarrheic and non-diarrheic feces (P=0.03); however, only the presence of stx1 correlated with diarrhea in both groups of samples (P<0.008). The incidence of toxigenic E. coli in both non-diarrheic and diarrheic greyhounds indicates a zoonotic potential from dogs to humans and requires further study.     

Association of a Pasteurella haemolytica-like organism with enteritis in swine.

A Pasteurella haemolytica-like organism was isolated from the intestines of 28 swine with clinical, gross, or microscopic evidence of enteritis. In 15 cases, other known enteric pathogens were also demonstrated, and in 13 cases, no other pathogens were detected. The mean age of affected animals was 44 days. Most of the animals had clinical evidence of diarrhea. Gross enteric lesions were present in 17 of 21 cases. Microscopic lesions were present in 24 of 26 cases. A diffuse or segmental moderate to severe necrotizing enteritis was the most common lesion in cases in which only the Pasteurella haemolytica-like organism was isolated. Biochemical tests gave results consistent with Pasteurella haemolytica, and 5 of 15 isolates met criteria for biotype A. Negative results were found with an indirect haemagglutination procedure for P. haemolytica.     

Ophthalmic examination and conjunctival bacteriologic culture results from a herd of North American bison.

OBJECTIVE: To establish ocular characteristics, determine nature and prevalence of ocular lesions, and identify representative bacterial flora from the conjunctiva of North American bison (Bison bison). DESIGN: Prospective study. ANIMALS: 63 bison; 45 males and 18 females. PROCEDURE: Ophthalmic examinations were performed on 1 group of 38 bison in December 1997 and on a second group of 25 in March 1998. Eyes were examined with a penlight, magnification loop, and indirect ophthalmoscope. Two culture swabs were used to obtain samples from the inferior conjunctival sac. One swab was submitted for isolation of bacteria and the second was submitted for isolation of Mycoplasma organisms. RESULTS: 15 ocular abnormalities were observed in 13 of the 63 bison. These included minor ocular discharge in 5 animals, 1 eyelid laceration, 1 periocular Demodex spp infection, 6 corneal abnormalities, 1 anterior synechia, and 1 cataract. Seventeen species of bacteria were isolated from the 63 swabs submitted for culture. The most prevalent bacteria were of the genus Bacillus (74.6%). Mycoplasma organisms were not observed. CONCLUSIONS AND CLINICAL RELEVANCE: Corneal abnormalities were the most frequently identified ocular lesions in bison. Bacterial flora of the conjunctiva and ocular characteristics were similar to those reported for cattle.