Advances in understanding disease epidemiology and implications for control and eradication of tuberculosis in livestock: the experience from New Zealand.

A deteriorating tuberculosis problem in cattle and deer in New Zealand has been halted and then reversed over the last decade. Mycobacterium bovis infection in both wild and domestic animal populations has been controlled. This has been achieved by applying a multi-faceted science-based programme. Key features of this have been a comprehensive understanding of the epidemiology of tuberculosis in animals, confidence in sampling wild animal populations, effective application of diagnostic tests in cattle and deer, and the ability to map M. bovis genotypes.

[Animal pathogens as biological weapons]. / Patogeny zwierzece jako bron biologiczna.

In this article, the most important animal pathogens, which, according to CDC classification, can be used as biological agents, are presented. The means of dissemination and the ways of infection's propagation are reviewed. Typical and the most dangerous signs and symptoms are described, as well as the consequences of these infections.

Development of a procedure for discriminating among Escherichia coli isolates from animal and human sources.

Counts of Escherichia coli cells in water indicate the potential presence of pathogenic microbes of intestinal origin but give no indication of the sources of the microbial pollution. The objective of this research was to evaluate methods for differentiating E. coli isolates of livestock, wildlife, or human origin that might be used to predict the sources of fecal pollution of water. A collection of 319 E. coli isolates from the feces of cattle, poultry, swine, deer, goose, and moose, as well as from human sewage, and clinical samples was used to evaluate three methods. One method was the multiple-antibiotic-resistance (MAR) profile using 14 antibiotics. Discriminant analysis revealed that 46% of the livestock isolates, 95% of the wildlife isolates, and 55% of the human isolates were assigned to the correct source groups by the MAR method. Amplified fragment length polymorphism (AFLP) analysis, the second test, was applied to 105 of the E. coli isolates. The AFLP results showed that 94% of the livestock isolates, 97% of the wildlife isolates, and 97% of the human isolates were correctly classified. The third method was analysis of the sequences of the 16S rRNA genes of the E. coli isolates. Discriminant analysis of 105 E. coli isolates indicated that 78% of the livestock isolates, 74% of the wildlife isolates, and 80% of the human isolates could be correctly classified into their host groups by this method. The results indicate that AFLP analysis was the most effective of the three methods that were evaluated.

O-antigen structural variation: mechanisms and possible roles in animal/plant-microbe interactions.

Current data from bacterial pathogens of animals and from bacterial symbionts of plants support some of the more general proposed functions for lipopolysaccharides (LPS) and underline the importance of LPS structural versatility and adaptability. Most of the structural heterogeneity of LPS molecules is found in the O-antigen polysaccharide. In this review, the role and mechanisms of this striking flexibility in molecular structure of the O-antigen in bacterial pathogens and symbionts are illustrated by some recent findings. The variation in O-antigen that gives rise to an enormous structural diversity of O-antigens lies in the sugar composition and the linkages between monosaccharides. The chemical composition and structure of the O-antigen is strain-specific (interstrain LPS heterogeneity) but can also vary within one bacterial strain (intrastrain LPS heterogeneity). Both LPS heterogeneities can be achieved through variations at different levels. First of all, O-polysaccharides can be modified non-stoichiometrically with sugar moieties, such as glucosyl and fucosyl residues. The addition of non-carbohydrate substituents, i.e. acetyl or methyl groups, to the O-antigen can also occur with regularity, but in most cases these modifications are again non-stoichiometric. Understanding LPS structural variation in bacterial pathogens is important because several studies have indicated that the composition or size of the O-antigen might be a reliable indicator of virulence potential and that these important features often differ within the same bacterial strain. In general, O-antigen modifications seem to play an important role at several (at least two) stages of the infection process, including the colonization (adherence) step and the ability to bypass or overcome host defense mechanisms. There are many reports of modifications of O-antigen in bacterial pathogens, resulting either from altered gene expression, from lysogenic conversion or from lateral gene transfer followed by recombination. In most cases, the mechanisms underlying these changes have not been resolved. However, in recent studies some progress in understanding has been made. Changes in O-antigen structure mediated by lateral gene transfer, O-antigen conversion and phase variation, including fucosylation, glucosylation, acetylation and changes in O-antigen size, will be discussed. In addition to the observed LPS heterogeneity in bacterial pathogens, the structure of LPS is also altered in bacterial symbionts in response to signals from the plant during symbiosis. It appears to be part of a molecular communication between bacterium and host plant. Experiments ex planta suggest that the bacterium in the rhizosphere prepares its LPS for its roles in symbiosis by refining the LPS structure in response to seed and root compounds and the lower pH at the root surface. Moreover, modifications in LPS induced by conditions associated with infection are another indication that specific structures are important. Also during the differentiation from bacterium to bacteroid, the LPS of Rhizobium undergoes changes in the composition of the O-antigen, presumably in response to the change of environment. Recent findings suggest that, during symbiotic bacteroid development, reduced oxygen tension induces structural modifications in LPS that cause a switch from predominantly hydrophilic to predominantly hydrophobic molecular forms. However, the genetic mechanisms by which the LPS epitope changes are regulated remain unclear. Finally, the possible roles of O-antigen variations in symbiosis will be discussed.

Trends in antimicrobial resistance of Salmonella isolated from animals, foods of animal origin, and the environment of animal production in Canada, 1994-1997.

The purpose of our study was to determine the occurrence, magnitude, trends, and relationships regarding antibiotic resistance of Salmonella isolated from animals, animal food products, and the environment of animals. We examined 621 strains of 67 different serovars isolated in 1994, 721 strains of 75 different serovars isolated in 1995, 1,219 strains of 83 different serovars isolated in 1996, and 1,336 Salmonella strains of 92 different serovars isolated in 1997, for resistance to 17 antibiotics at one to three different concentrations with the agar dilution method. The overall resistance magnitude regressed from 9.2% in 1994 to 8.1% in 1997. Resistance to streptomycin (30.4% of 3,897 isolates), tetracycline (27.3%), and sulfisoxazole (23.7%) was highest. Resistance to streptomycin, tetracycline, kanamycin, and gentamicin declined during the 4-year period. Notable increases in resistance to ampicillin, chloramphenicol, and neomycin occurred during the 1994-1997 years. None of the isolates was resistant to amikacin. None of the isolates was resistant to ciprofloxacin at 1, 2, and 4 microg/ml. Salmonella bredeney isolates from turkeys showed a decreased sensitivity to ciprofloxacin and were resistant at the low level of 0.125 microg/ml, but none of these isolates was resistant at 1 microg/ml. Resistance to nalidixic acid correlated significantly with decreased sensitivity to ciprofloxacin; 122 of 127 (96%) isolates resistant to nalidixic acid at 32 microg/ml were resistant to ciprofloxacin at 0.125 microg/ml but sensitive at 1 microg/ml. Resistance to S. typhimurium to each of the seven antibiotics ampicillin, chloramphenicol, kanamycin, neomycin, streptomycin, sulfisoxazole, and tetracycline increased persistently during each of the years 1994-1997, but none of the S. typhimurium isolates showed decreased sensitivity to ciprofloxacin. Clinical isolates of Salmonella were twice as frequently resistant to the antimicrobials in the test panel than isolates obtained during surveys. Salmonella isolates from turkeys were more frequently resistant than isolates from pigs, cattle, and chickens.

Antibiotic resistance in bacteria of animal origin: methods in use to monitor resistance in EU countries.

A study on the ongoing monitoring programmes in 13 European countries was made as part of a concerted action funded by the European Commission. Five main reference systems were used in the surveyed countries and three categories of bacteria were monitored, zoonotic agents, indicator bacteria and veterinary pathogens. The five reference systems and an overview of the national monitoring programmes are described. Differences exist and there is a real need for standardisation at the European level. This harmonisation could be set up both for microbiological methods and the epidemiological results derived from common methods. Disk diffusion methods are most widely used and many of the monitored species and control strains are similar in the action's participating countries.

Antibiotic resistance monitoring in bacteria of animal origin: analysis of national monitoring programmes.

Methods of antibiotic resistance monitoring of bacteria from animals in 12 European countries were surveyed in 1998. Most laboratories used disk diffusion methods, usually expressing results qualitatively, although a few also expressed the results either as MICs or zone diameters. The number of antibiotics used ranged from 5 to 37 (mean 15) and the most common antibacterials were streptomycin, gentamicin, neomycin, ampicillin, tetracyclines, chloramphenicol and sulphonamides. Salmonellae were monitored by most centres but few-tested campylobacter regularly. Escherichia coli from a wide range of animal species were tested in nine countries. Enterococci were tested on a limited ad hoc basis in six countries. Staphylococci, streptococci and pasteurellae were also frequently monitored but the number of isolates tested showed wide variation. Overall the presentation of the results differed, but most programmes used disk diffusion, control strains and monitored similar bacteria. Thus, it may be possible to harmonise monitoring programmes within the EU.

Bacterial symbioses. Predation and mutually beneficial associations.

The endosymbiotic theory, which has proved to explain the origin of mitochondria and chloroplasts, also posits the origin of nucleus and other cellular organelles that could have derived from ancient relationships among bacteria. It seems that predation might have been a prerequisite to the establishment of symbiosis as a source of evolutionary novelty. This review describes current different examples of bacteria able not only to attack and degrade other bacteria, but also to establish stable symbiotic relationships with different eukaryotic organisms.

Functions of bacterial flagella.

Many bacterial species are motile by means of flagella. The structure and implantation of flagella seems related to the specific environments the cells live in. In some cases, the bacteria even adapt their flagellation pattern in response to the environmental conditions they encounter. Swarming cell differentiation is a remarkable example of this phenomenon. Flagella seem to have more functions than providing motility alone. For many pathogenic species, studies have been performed on the contribution of flagella to the virulence, but the result is not clear in all cases. Flagella are generally accepted as being important virulence factors, and expression and repression of flagellation and virulence have in several cases been shown to be linked. Providing motility is always an important feature of flagella of pathogenic bacteria, but adhesive and other properties also have been attributed to these flagella. In nonpathogenic bacterial colonization, flagella are important locomotive and adhesive organelles as well. In several cases where competition between several bacterial species exists, motility by means of flagella is shown to provide a specific advantage for a bacterium. This review gives an overview of studies that have been performed on the significance of flagellation in a wide variety of processes where flagellated bacteria are involved.

Safe biotechnology (5). Recommendations for safe work with animal and human cell cultures concerning potential human pathogens.

The benefits of using animal or human cell cultures have been clearly demonstrated in diagnostic and therapeutic research and in their application for manufacturing. Cell cultures serve as a tools for the production of vaccines, receptors, enzymes, monoclonal antibodies and recombinant DNA-derived proteins. They represent an integral part of drug development for which corresponding facilities, equipment and manufacturing processes are required. Although the cells themselves offer no particular risk to workers in laboratories and production areas or to the environment, the cell cultures may be contaminated with viruses, mycoplasma, bacteria, yeast and fungi or might contain endogenous viruses. The containment level for animal and human cells is therefore determined by the risk class of these agents. The history of animal and human cell cultures has proved that they can be handled safely. The recommendations in this publication concern the safe handling of cell cultures (tissue explants, primary cell cultures) and permanent cell lines of animal and human origin. A classification system of safety precautions has been elaborated according to the potential for contamination with the pathogenic agents involved.

Evaluation of the Sceptor system for identification of bacteria of veterinary origin.

The Sceptor system (Becton Dickinson Diagnostic Instrument Systems, Towson Md.) was assessed for its ability to identify veterinary clinical isolates. A total of 605 bacteria, including 315 isolates of the family Enterobacteriaceae, 191 gram-negative nonenteric bacteria, and 99 gram-positive bacteria, were tested. Overall, 534 (88.3%) were correctly identified, 28 (4.6%) were not identified, 12 (2.0%) were incorrectly identified at the genus levels, and 32 (5.3%) were incorrectly identified at the species level. The Sceptor system correctly identified 292 (92.7%) isolates of Enterobacteriaceae, 165 (86.4%) gram-negative nonenteric bacteria, and 77 (77.8%) gram-positive bacteria. One hundred thirty organisms not contained in the data base were tested with the Sceptor system to assess the possibility of expanding the data base. The Sceptor system was an acceptable method for the identification of isolates of Enterobacteriaceae but not gram-negative nonenteric and gram-positive bacteria of animal origin. Development of a veterinary isolate-specific data base would improve the utility of the Sceptor system in veterinary diagnostic bacteriology.

In vitro susceptibility of bacteria to a ticarcillin-clavulanic acid combination.

In vitro testing of bacterial susceptibility to a combination of ticarcillin and clavulanic acid was done, using 406 aerobic gram-positive and gram-negative isolates (considered to be pathogens) cultured from equine and small animal specimens. A microdilution broth technique of susceptibility testing was performed, using trays with wells containing a range of doubling concentrations of dehydrated ticarcillin (range, 0.50 to 128 micrograms/ml) with fixed concentration of clavulanic acid (4 micrograms/ml). The following isolates of equine origin were (90%) susceptible to concentrations of ticarcillin and clavulanic acid combinations of less than or equal to 16 and 4 micrograms/ml, respectively: Staphylococcus aureus, S intermedius, Klebsiella pneumoniae, Enterobacter aerogenes, Ent agglomerans, Ent cloacae, Escherichia coli, Actinobacillus sp, Corynebacterium pseudotuberculosis, Rhodococcus equi, Proteus vulgaris, and Bordetella bronchiseptica. Isolates of small animal origin (90%) susceptible to less than or equal to 16 and 4 micrograms of ticarcillinclavulanic/ml included S aureus, S intermedius, Ent aerogenes, Ent agglomerans, Pasteurella multocida, B bronchiseptica, Pr mirabilis, and Serratia sp.

Tuberculosis in East Sussex. IV. A systematic examination of wild mammals other than badgers for tuberculosis.

A detailed investigation of the possible role of wild mammals, other than badgers, in the maintenance of Mycobacterium bovis in an area on the South Downs of East Sussex was carried out over 3 years. Estimates of population sizes were made where possible and minimum sample sizes were selected to be 95% certain of including at least one infected animal if the prevalence was at least 5%. Samples of wild mammals were taken from populations which had the highest potential direct or indirect contact rate with known infected badgers. M. bovis was not isolated from any of the 15 species of wild mammals. It was concluded that badgers are able to maintain M. bovis in an area independently of other species, and that in the area studied other species were not a source of infection for the cattle herds.

Evidence for the presence of duck hepatitis B virus in wild migrating ducks.

A virus closely related to duck hepatitis B virus (DHBV) was isolated from serum and liver samples of wild migratory ducks (mallards) caught in two separate wildlife reserve parks in France. In the first one (Dombes region) 12% of wild mallards were positive for DHBV, and in the second (River Somme) 3% of mallards were found positive. The DHBV isolated from the serum of wild mallards was also associated with an endogenous DNA polymerase activity capable in vitro of completing a partially double-stranded viral DNA into a fully double-stranded DNA of 3 kb. The various replicative DNA forms reported for DHBV were also detected in the liver of wild viraemic mallards. The DNA restriction enzyme pattern of the wild mallard strain differed from that of American and French strains of DHBV. The wild mallard strain DHBV was experimentally transmitted to mallard and Pekin ducklings and induced a chronic viraemia in both varieties of infected birds. This strain might be the common ancestor of all DHBV strains isolated from domestic ducks world-wide. The discovery of a DHBV-related virus in the natural wild population might be an important clue in the study of the different roles of environmental, host and viral factors in the pathogenesis of DHBV infection, and their possible oncogenic action in ducks.

Ribavirin therapy for Hantaan virus infection in suckling mice.

We recently reported that ribavirin inhibited Hantaan virus (HV) replication in vitro. In the present study, we used the HV suckling mouse model to evaluate the efficacy of treatment with various doses of ribavirin. Beginning on day 10, untreated animals, infected with ten times the amount of HV (strain 76/118) required to kill 50% of the animals, lost weight; by days 15 to 18, they developed paralysis of both hind limbs, and they died between days 20 and 21. Treatment with 50 mg of ribavirin/kg per day begun on day 10-following onset of early clinical signs and demonstrable virus in serum and organs--saved 11 of 20 animals compared with 0 of 70 controls. Treated animals did not develop further signs of infection, and by day 22, survivors resumed normal weight gain. After ribavirin treatment, titers of virus decreased in serum, liver, and spleen by two days; in lung within six days; and in the kidney by eight days. By day 18, titers in organs of treated animals were 100-fold lower than in sham-treated animals, with the exception of the brain. Titers of virus in brain fell by day 20, when virus in untreated animals reached greater than 10(7) pfu/g. Treated survivors continued to have decreasing titers of virus in organs and were followed for 75 days with no sign of disease recurrence.