Identification and characterization of Streptococcus suis.

A total of 188 Streptococcus suis strains isolated from pigs with various lesions, mainly bronchopneumonia, were identified using classical biochemical methods and using the API 20 STREP system. The serological classification was performed by precipitation reactions after Lancefield extraction, slide-coagglutinations and capsular reaction tests. Fifty-nine strains belonged to Types 1, 1/2 or 2, 78 strains to Types 3-8 and 51 strains were non-typable. The results of the different tests and the biochemical differences between the different serotypes are discussed.

Identification of porcine Serpulina strains in routine diagnostic bacteriology.

Serpulina strains from pigs were identified using simple tests. The large size of S. hyodysenteriae in stainings from colonic contents and faeces was found useful for the presumptive differentiation of this major pathogenic species from the other Serpulinae. However, this morphological characteristic gets lost upon cultivation. The 'ring phenomenon' aided to confirm the strong haemolysis typical for S. hyodysenteriae. The weakly haemolytic species S. innocens, S. pilosicoli, S. intermedia and S. hyodysenteriae could be differentiated with the help of the indole spot test and two or four other simple enzymatic tests. Nearly half of the S. hyodysenteriae strains isolated in Belgium were indole-negative. Such strains have only rarely been reported earlier, and were absent among the strains from other European countries examined.

Slide precipitation: a simple method to type Actinobacillus (Haemophilus) pleuropneumoniae.

Soluble thermostable antigens prepared from Actinobacillus pleuropneumoniae, as commonly applied in the ring precipitation test, were used in rapid slide tests. This method was easier to perform than the ring precipitation test and showed the same specificity. This specificity was higher than that obtained in slide agglutination tests using whole bacterial cells.

Characteristics of different Streptococcus suis ecovars and description of a simplified identification method.

Streptococcus suis strains associated with different animal hosts or located in different body regions constitute special ecovars of S. suis. A group of CO2-dependent strains which showed several unusual traits was found in the genital tract of swine, and mannitol- and sorbitol-fermenting strains were isolated from sheep, cattle and horses. S. suis was found to be biochemically more heterogenous than originally described. A detailed description is given of additional characteristics of the species as well as of characters which should be modified in the species description. A simple scheme which uses the amylase and the Voges-Proskauer (acetoin) reactions for the identification of S. suis is proposed. All S. suis strains tested produced a characteristic amylase reaction on Mueller-Hinton plates or on Columbia Agar Base enriched with starch.

An atypical Staphylococcus aureus intramammary infection in a dairy herd.

An atypical Staphylococcus aureus (S. aureus) strain, isolated in a dairy herd over an 8 month period, was examined. The S. aureus strain was clumping factor negative, weakly heat-resistant deoxyribonuclease positive and produced narrow zones of double haemolysis. In total, 57 quarter infections were observed. Prevalence data per month, calculated as the percentage of quarters infected with this atypical S. aureus strain varied from 7.5% to 17.7% and the new infection rate varied from 0.14 to 0.55. In routine bacteriology, the large number of quarters infected with the atypical S. aureus could easily be misclassified as quarters infected with non-aureus staphylococci.

Identification of aesculin-hydrolyzing streptococci, lactococci, aerococci and enterococci from subclinical intramammary infections in dairy cows.

Aesculin-hydrolyzing, catalase-negative, gram-positive cocci isolated from subclinical intramammary infections in dairy cows were identified to species level using growth characteristics and biochemical activity. The results indicated that the aesculin-hydrolyzing cocci associated with this type of infection are a very heterogenic group. S. uberis strains, including inulin- or beta-glucuronidase-negative isolates, accounted for only about one-third of the collection, and Enterococcus faecalis strains for one-fifth. Other species of some importance included (in descending order of isolation frequency) Aerococcus viridans, Streptococcus pluranimalium, Lactococcus garvieae, Streptococcus bovis and Streptococcus gallolyticus.

Identification of a new biotype of Actinomyces hyovaginalis in tissues of pigs during diagnostic bacteriological examination.

Bacterial strains isolated from a large variety of necropsy samples of pigs and previously described as a phenotypical homogeneous group were shown to belong to the species Actinomyces hyovaginalis. This was unexpected because their colonial characteristics, as well as their origins, were very different from those originally reported for the vaginal strains on which the species description of A. hyovaginalis was based. Colonial morphology, as well as fermentation of cellobiose, reactions in hippurate and nitrate and production of beta-glucuronidase, allowed separation of the strains studied here from the vaginal strains. Analysis of tRNA intergenic length polymorphisms (tDNA-PCR), 16S rRNA-gene sequencing and DNA-DNA hybridizations were carried out and led to the proposal of a separate biotype within the species A. hyovaginalis. Since, the strains were isolated from different body sites, this biotype has been designated as the 'general' biotype of A. hyovaginalis, while the strains on which the original species description was based are designated as the 'vaginal' biotype.

Focal dermatitis and cellulitis in broiler chickens: bacteriological and pathological findings.

Involvement of aerobic bacteria, especially Escherichia coli, in lesions of cellulitis in broiler chickens was investigated. Samples of subcutaneous caseous material for bacteriological examination were collected aseptically at the slaughterhouse from 109 broilers with lesions. Skin tissue was taken from five of these birds for histopathological examination. In 96 of the 109 (88.1%) broilers sampled, E. coli was isolated from the lesion, and in 60 of these birds it was the only bacterial species found. In 33 broilers, Streptococcus dysgalactiae was found along with E. coli. Although serotype O78 was isolated the most frequently, numerous other serotypes were found; no correlation could be established between the size of the lesions and the serotype isolated. The microscopic lesions were characterized by thickening of the dermis with a granulomatous inflammatory reaction. This study confirms the frequent association of E. coli with cellulitis lesions in broiler chickens and reports the frequent isolation of S. dysgalactiae from the lesion.

Epidemiology of methicillin-resistant Staphylococcus aureus in dairy herds.

Sixty-eight methicillin-resistant Staphylococcus aureus strains were isolated from mastitis milk samples originating from 20 Belgian dairyherds. All these strains appeared to be representatives of one single strain which was probably of human origin. Evidence is presented indicating a rapid in vivo evolutionary change in this strain. The following characteristics were found to be variable: the production of beta haemolysin inversely connected with fibrinolysin (staphylokinase) activity; the production of lipase, enterotoxin B and delta haemolysin; the resistance to neomycin, chloramphenicol, tetracyclines, methicillin and spectinomycin associated with constitutive or inducible macrolide resistance.

A simple identification scheme for coagulase negative staphylococci from bovine mastitis.

Coagulase-negative staphylococci from cases of bovine mastitis were identified to species level by using an identification scheme based on a three-plate test system which tested for DNase on DNA agar, for protease on calcium caseinate agar, and for the organism's sensitivity to novobiocin, desferrioxaminine (deferoxamine) and fosfomycin by agar diffusion tests. Testing for the inhibition of Staphylococcus delta haemolysin (Skalka 1991) can replace the protease tests.

Taxon 20 (Fam. Pasteurellaceae) infections in European brown hares (Lepus europaeus).

Hemolytic bacteria, phenotypically related to organisms previously identified as Pasteurella haemolytica and tentatively named Taxon 20, were isolated from cases of purulent bronchopneumonia and from conjunctivitis in European brown hares (Lepus europaeus). The bronchopneumonia, sometimes accompanied by lesions in other organs, occurred without other concomitant disease. The conjunctivitis was found mainly in animals suffering from the European brown hare syndrome.

Serotyping and quantitative determination of in vitro antibiotic susceptibility of Actinobacillus pleuropneumoniae strains isolated in Belgium (July 1991-August 1992).

One hundred and ninety nine Actinobacillus pleuropneumoniae isolates obtained from the respiratory tract of pigs in Belgium (1991-1992) were serotyped using slide agglutination and slide precipitation tests. Biotype 1-serotype 2 and 3 strains were isolated most frequently and represented 36% and 21% of the isolates, respectively. Serotype 9 and serotype 5B strains represented 15% and 10% of the total number of isolates, respectively, while serotypes 7, 8, 10 and 11 were isolated only sporadically. Serotypes 5B, 10 and 11 were isolated for the first time in Belgium. Biotype 2 strains represented 12.5% of the total number and all belonged to the serotype 2. The in vitro susceptibility of 138 strains was determined for ten commonly used antibiotics. For three antibiotics, ampicillin, chloramphenicol, and oxytetracycline, a bimodal distribution of strain sensitivities was observed. A total of 17 strains (12%) were considered to have acquired resistance to one or more of these antibiotics.

[Pasteurella] caballi infection not limited to horses - a closer look at taxon 42 of Bisgaard.

AIM: To investigate if taxon 42 of Bisgaard isolated from pigs represents genuine [Pasteurella] caballi, which was previously only isolated from horses. METHODS AND RESULTS: A total of 15 field isolates from horses and pigs from five different countries representing three continents were subjected to extended phenotypical characterization. Although minor differences were observed between taxon 42 and [P.] caballi, these differences did not allow phenotypic separation. Ribotyping based on HindIII digestion showed five profiles based on nine band positions. One [P.] caballi strain and two taxon 42 strains shared the same profile. Ribotyping using HpaII gave a higher diversity with nine profiles based on ten band positions. While no profiles were shared between the taxon 42 and [P.] caballi strains, pattern analysis showed that two of the taxon 42 isolates were most similar (91% similarity) with a [P.] caballi isolate. The 16S rRNA gene sequencing of one strain of taxon 42 and one strain of [P.] caballi was performed and compared with the published sequence for the type strain of [P.] caballi. The three strains showed nearly identical sequences with at least 99.8% similarity. DNA re-associations measured by the micro-well method were 79 and 77%, respectively between the type strain of [P.] caballi and two strains of taxon 42 representing distinct ribotypes and confirmed that taxon 42 belongs to [P.] caballi. CONCLUSION: The present investigation documents that [P.] caballi can be isolated from clinical respiratory specimens from pigs and the recognized association with respiratory infections in horses and horse bite infection in humans. Strains classified as taxon 42 are [P.] caballi isolated from pigs and for both pigs and horses, lesions mainly include the respiratory tract. SIGNIFICANCE AND IMPACT OF THE STUDY: The results will improve the diagnostics and progress studies of virulence and epidemiology of [P.] caballi.

In vitro susceptibility of Clostridium perfringens isolated from farm animals to growth-enhancing antibiotics.

Minimal inhibitory concentration (MIC) determinations were carried out with seven growth-enhancing antibiotics against 95 Clostridium perfringens field isolates obtained during 1991 and 1992 from poultry, pigs and calves. All were resistant to 64 micrograms ml-1 of the bambermycin antibiotic, flavomycin (flavophospholipol) and susceptible to avoparcin (MIC90 0.25 micrograms ml-1), avilamycin (MIC90 0.5 micrograms ml-1) and salinomycin (MIC90 < or = 0.12 micrograms ml-1). Acquired resistance against bacitracin was detected in some isolates from poultry and bovines and resistance to tylosin and virginiamycin in some strains from all species investigated. Overall, the prevalence of resistance was comparable to the low levels recorded in 1979 in Cl. perfringens isolates from the same animal host species.

Bèta-hemolytic streptococci from pigs: bacteriological diagnosis.

Bèta-hemolytic streptococci from lesions in pigs were identified as S. dysgalactiae biotype "equisimilis" and S. dysgalactiae serovar L, S. porcinus, S. agalactiae, E. faecalis and CO2 dependent and broad bèta-hemolytic S. suis. Data are provided which can be used in the interpretation of commercial identification systems. Tests results and physiological characteristics which complete identification procedures using coagglutination tests are proposed and discussed.

Composition of the enterococcal and streptococcal intestinal flora of poultry.

Identification to species level showed that Enterococcus faecalis and Ent. faecium largely dominated the enterococcal and streptococcal gut flora of 1-d-old chicks. Enterococcus faecalis was rare in 3- to 5-week-old broilers. Two species, Ent. faecium and Streptococcus alactolyticus, were isolated from nearly all broilers examined. Enterococcus hirae and Ent. durans were found in the small intestines of this category of poultry. In layers and parent stock of over 12 weeks of age, Ent. cecorum dominated with Strep. alactolyticus ranking next. Other species were isolated irregularly. Enterococcus avium and Ent. gallinarum, originally described from chickens, were rarely found. These species did not appear to belong to the normal intestinal flora of poultry.

Identification and composition of the streptococcal and enterococcal flora of tonsils, intestines and faeces of pigs.

Streptococcus suis was the most frequent Streptococcus spp. in pig tonsils, followed by the beta-haemolytic porcine 'equisimilis' ecovar of Strep. dysgalactiae. The intestinal streptococcal flora was composed of Strep. bovis, Strep. hyointestinalis and Strep. suis. Many of these intestinal Strep. suis belonged to a beta-glucuronidase-negative biotype which is infrequent in lesions. Nearly half of the strains presumptively identified as Strep. alactolyticus produced acid from lactose. This species was not found in tonsils and intestines but was about equally prevalent as Strep. hyointestinalis in pig faeces and rectal swabs. Other streptococci were rare in this material. Enterococci were much less frequently identified than streptococci in tonsils and faeces. In intestinal samples Enterococcus faecalis, Ent. faecium, Ent. hirae and Ent. cecorum were most frequently found. In faeces Ent. faecium was the most prevalent enterococcus. The characteristics of the less well known species Strep. alactolyticus and Strep. hyointestinalis are described in detail, and guidelines for their differentiation from Strep. bovis and Strep. suis given.