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Biomedical subjects

L Okerman

Publications and source records attributed to L Okerman.

At least 19 recordsLinked to original sources
PubMed2005

Interlaboratory study based on a one-plate screening method for the detection of antibiotic residues in bovine kidney tissue.

A microbiological test based on one-plate, seeded with Bacillus subtilis BGA, is frequently used in Belgium as a screening method to monitor antibiotic residues in kidney tissue of slaughter animals. The procedure as described in the National Legislation recommends test agar pH 7.2 from Merck. Since this type of agar is no more commercially available, two kinds of agar medium are proposed on the market: niertest agar from Biotrading and Standard II nutrient agar from Merck. Niertest agar, which is actually used by a few laboratories, is a ready-to-use medium manufactured from test agar pH 7.2 from Merck. Its composition is identical to those of test agar pH 7.2. Standard II nutrient agar is the second alternative culture medium which is used by a higher number of laboratories. The equivalence of the standard II nutrient agar medium to both identical culture media (test agar pH 7.2 and niertest agar) was evaluated during a national collaborative trial. Results of this study as well as the experimental procedure are presented.

Animals↗
PubMed2004

Evaluation and establishing the performance of different screening tests for tetracycline residues in animal tissues.

Four methods intended for screening muscle tissue for residues belonging to the tetracycline group were compared using artificially contaminated as well as incurred samples. Two agar diffusion methods were studied: one with Bacillus subtilis as a test strain, the second with Bacillus cereus. Two variants of each method were compared: thin plates for analysis of intact or minced meat, and thick plates for analysis of meat fluid. The thin plate variants could not be evaluated with artificially contaminated samples because it was impossible to prepare homogeneously spiked, undiluted meat. The thick plates were suited for doxycycline and chlortetracycline, but they did not detect oxytetracycline or tetracycline in spiked meat fluid. The results of these tests done on incurred meat were very good for doxycycline and satisfying or just failing for oxytetracycline, while the best detection capability was obtained when intact frozen meat was examined on thin plates seeded with B. cereus. Two commercially available screening tests were also evaluated. The Premi(R) test, an inhibitor test with Bacillus stearothermophilus as a test strain and an indicator for growth, was not suited for detection of tetracyclines up to the maximum residue limit. Tetrasensor(R), a receptor test specific for tetracyclines, proved a quick and simple test able to detect meat samples artificially contaminated with tetracycline, oxytetracycline, doxycycline or chlortetracycline, as well as meat incurred with oxytetracycline or doxycycline.

Animals↗
PubMed2001

Inhibition tests for detection and presumptive identification of tetracyclines, beta-lactam antibiotics and quinolones in poultry meat.

A combination of three plates, seeded with strains of Micrococcus luteus, Bacillus cereus or Escherichia coli, can be used for detection of residues of beta-lactam antibiotics, tetracyclines and fluoroquinolones. The sensitivity of each plate is optimal for only one of these groups, resulting in detection limits (LOD) lower than the corresponding maximum residue limits (MRL) and in distinct inhibition patterns typical for each antibiotic family. Beta-lactam antibiotics such as penicillin G, ampicillin and amoxicillin give only inhibition zones on the plate with M. luteus. Tetracyclines are detected up to the MRL level with B. cereus, and fluoroquinolones with E. coli. The LODs of the antibiotics tested were as follows: penicillin G (PENG) 0.9 ng, ampicillin (AMPI) 0.6 ng and amoxicillin (AMOX) 1.0 ng on the plate with M. luteus; tetracycline (TET) 4 ng, oxytetracycline (OXY) 3 ng, doxycycline (DOX) 0.6 ng, and chlortetracycline (CHL) 0.3 ng on the plate with B. cereus; enrofloxacin (ENRX) 1.5 ng, ciprofloxacin (CIPX) 0.5 ng and flumequine (FLUM) 1.5 ng on the plate with E. coli. The combination of plates enables the laboratory to select appropriate chromatographic techniques for identification and quantification of the residues. On the other hand, the three groups can also be detected on one plate seeded with Bacillus subtilis, although the limits of detection are higher: PENG 0.4 ng, AMPI and AMOX 3 ng, TET 5 ng, OXY 8 ng, DOX 1 ng, CHL 0.5 ng, ENRX 4 ng, CIPX 10 ng and FLUM 4 ng. The test was applied to 228 broiler fillets and to 27 turkey thighs, originating from different poultry slaughterhouses. Nineteen broiler fillets contained inhibiting substances. The positive results of the inhibition tests were confirmed with a chromatographic technique. Doxycycline residues were found in 16 samples and amoxicillin in two.

4-Quinolones↗
PubMed1998

Detection of antibiotics in muscle tissue with microbiological inhibition tests: effects of the matrix.

The effects of the tissue matrix on detection limits of antibiotics with microbiological inhibition tests, intended for muscle tissue, were measured. Pieces of frozen meat were laid directly on top of paper disks impregnated with aqueous antibiotic solutions. Inhibition zones were compared with those obtained by the same standard solution without tissue. Only tetracyclines were detected as efficiently with as without muscle tissue. Inhibition zones of the beta-lactam antibiotics ampicillin and penicillin G, and the fluoroquinolone antibiotics enrofloxacin and ciprofloxacin were smaller when muscle tissue was added to low levels of standard solution. At higher levels the differences were not substantial. Inhibition zones of tylosin were smaller and irregular or had disappeared completely, while ceftiofur, sulfadimidine, erythromycin, lincomycin, and streptomycin were not detected in spiked muscle tissue at concentrations fivefold higher than the detection limits without tissue. These results indicate that ceftiofur, sulfonamides, streptomycin and some macrolide antibiotics cannot be detected in intact meat with the plates and bacterial strains prescribed in the European Four Plate Test, a test which was initially intended as a multi-residue method for muscle tissue. Two plates of this system are not suitable for screening purposes; a third one detects tetracyclines and beta-lactam antibiotics in spiked tissue; the fourth one is sensitive for beta-lactam antibiotics and for some but not all macrolides. Samples spiked with the fluoroquinolones enrofloxacin and ciprofloxacin can be detected with an additional plate, not included in the Four Plate Test.

Animals↗
PubMed1998

Detection of residues of tetracycline antibiotics in pork and chicken meat: correlation between results of screening and confirmatory tests.

Residues of the tetracycline group of antibiotics were quantified in pork and chicken muscle tissue that had previously been screened with a microbiological inhibition test and an immunological method. Pieces of frozen pork and chicken meat were screened on a pH 6 culture medium seeded with Bacillus subtilis. An aqueous extract of the inhibitor-positive samples was then screened with a group-specific commercial ELISA kit, able to detect levels of oxytetracycline, chlortetracycline, tetracycline and doxycycline corresponding with the European MRL or lower. The cut-off value of the ELISA was set at a B/B0 value of 75%. Finally, confirmation and quantification were performed using a validated HPLC method with fluorescence detection. The fluorescence was induced by complexation of the tetracyclines with the zirconium cation which is added post-column to the HPLC eluate. This fluorescence makes it possible to quantitate residues below one-half of the MRL. To gain additional qualitative information some samples were also analysed with LC-MS-MS. ELISA analysis demonstrated the presence of residues of tetracyclines in 12 out of 19 inhibitor-positive pork samples and in 19 out of 21 inhibitor-positive chicken samples. Doxycycline was detected with HPLC in 10 of these 12 pork samples and in 18 out of 19 chicken samples. The two other ELISA positive pork samples contained oxytetracycline, while no tetracyclines were found in one ELISA positive chicken meat sample. The correlation between the ELISA B/B0 values and the actual levels determined with the HPLC method was poor, whereas a better correlation was observed between the inhibition zones and the doxycycline levels. Our results indicate that an inhibition test with a medium at pH 6 and B. subtilis as test organism is well suited to screen pork and chicken muscle tissue for residues of tetracycline antibiotics. Since many positive samples contained doxycycline levels below the MRL, a confirmatory method is necessary to quantify the residues.

Animals↗
PubMed1996

A new pathogenic Staphylococcus aureus type in commercial rabbits.

Heavy losses in commercial rabbitries with mainly cutaneous infections were found to be caused by a special Staphylococcus aureus type. This type differs from the previously known rabbit and hare pathogenic strains causing similar infections, mainly in its unique phage type.

Abscess↗
PubMed1990

In vivo activity of orally administered antibiotics and chemotherapeutics against acute septicaemic pasteurellosis in rabbits.

Different antibiotics and chemotherapeutics were tested for therapeutic efficacy in rabbits, in an experimental model using a Pasteurella multocida strain which causes hyperacute septicaemia in this animal species. Only enrofloxacin, administered in the drinking water at a concentration of 50-100 mg/l cured the rabbits, provided that a daily intake of 5 mg/kg body weight was achieved. The other drugs tested (tetracycline, spiramycin, erythromycin and a combination of sulfamerazine with trimethoprim), at doses recommended for rabbits, showed little or no activity at all, with the exception of chloramphenicol, which was only partially effective.

4-Quinolones↗
PubMed1987

Failure of oil adjuvants to enhance immunity induced in mice by an inactivated rabbit Pasteurella multocida vaccine.

Mice were immunized with different preparations of a killed whole cell Pasteurella multocida vaccine and challenged with successive tenfold dilutions of the homologous strain. Vaccines adjuvanted with mineral oil did not confer better protection against death than non-adjuvanted suspensions, even when the mice were challenged at 3 months after vaccination. Very good protection was obtained when the non-adjuvanted suspension had been administered twice.

Adjuvants, Immunologic↗
PubMed1987

Enteric infections caused by non-enterotoxigenic Escherichia coli in animals: occurrence and pathogenicity mechanisms. A review.

Not all E. coli that cause diarrhoea in farm animals act by elaborating the classical heat-labile or heat-stable enterotoxins. These newly recognised animal enteropathogenic E. coli (EPEC) attach to and efface the microvilli of the gut epithelium and resemble the well known human EPEC. In rabbits, only this type of E. coli enteritis is known to be important and a similar disease has been shown to occur in cattle also. There is no doubt that adherence factors are important in the pathogenesis of animal EPEC, but they are not well understood when compared with the adhesion of human EPEC, or to the adhesion of animal ETEC. The enteropathogenic effect is probably due to Shiga-like toxin, a cytotoxin that is active on Vero cells and has also been called Verotoxin. A different type of Verotoxin is produced by most serotypes that are associated with post-weaning diarrhoea and oedema disease in pigs. This toxin is suspected to play a role in the pathogenesis of the latter.

Animals↗
PubMed1985

Biotypes of enteropathogenic Escherichia coli strains from rabbits.

Forty-five enteropathogenic (enteropathogenic Escherichia coli-like) strains isolated in commercial rabbit farms were subdivided into four biotypes with the help of six carbohydrate fermentation tests, ornithine decarboxylase tests, and motility tests. E. coli strains which caused neonatal diarrhea in baby rabbits belonged to a single biotype, biotype 1, and displayed the same serotype antigens. Biotype 2 strains provoked diarrhea of variable severity in weaned rabbits and were also pathogenic for baby rabbits under laboratory conditions. Biotype 1 and biotype 2 strains resembled each other in many respects. Biotype 3 and biotype 4 (represented by a single strain) were highly pathogenic for weaned rabbits, but they provoked no symptoms or lesions in baby rabbits. Biotype 3 formed a homogeneous group of nonmotile strains which possessed the O15 antigen. Forty-two strains from nondiarrheic rabbits constituted a very heterogeneous collection of biotypes, most of which could easily be differentiated from the pathogenic types. Biotyping can be used to recognize rabbit pathogenic strains.

Animals↗
PubMed1984

Cutaneous staphylococcosis in rabbits.

An outbreak of cutaneous staphylococcosis caused high mortality among newborn and very young rabbits. The most typical lesions were exudative dermatitis in the youngest, subcutaneous abscesses in rabbits of all ages and mastitis in lactating does. Generalised staphylococcosis was a frequent secondary manifestation of the disease.

Animals↗
PubMed1984

Pathogenic properties of Escherichia coli strains isolated from diarrheic commercial rabbits.

Thirty-two different strains of Escherichia coli isolated from diarrheic commercial rabbits showing intestinal attachment of bacilli were studied. None of the strains produced thermostable or thermolabile enterotoxins, and none was invasive. Strains isolated from suckling rabbits attached in vitro to the brush borders of intestinal villi, whereas strains from weanling rabbits did not. After experimental infection of 5-week-old rabbits, the 26 strains isolated from weaned diarrheic rabbits attached to the epithelium of ileum, cecum, and colon, whereas only slight attachment was found after infection with the six strains isolated from suckling diarrheic rabbits. The former strains induced diarrhea in 87% of the rabbits, whereas the latter induced diarrhea in only 9% of inoculated rabbits. E. coli isolated from healthy rabbits did not cause diarrhea. Strains isolated from diarrheic suckling rabbits all belonged to serotype O109:K-:H2, whereas strains from diarrheic weaned rabbits belonged to at least eight different serogroups. It is suggested that two different mechanisms of E. coli enteropathy might exist in rabbits.

Animals↗
PubMed1981

Protective effects of inactivated Pasteurella vaccines in specific pathogen free rabbits.

Different inactivated P. multocida vaccines were investigated for their protective capacities against experimental infection with virulent P. multocida strains in SPF rabbits. It was found that bacterins without adjuvant and bacterins combined with the adjuvants tested provoked immunity against aerosol infection with homologous strains. However, most bacterins tested caused local tissue irritation. Further work was done with oil adjuvant vaccines because lesions were less severe with this type of vaccine. Some of the multicomponent vaccines tested gave good immunity against heterologous infection, while others did not.

Adjuvants, Immunologic↗
PubMed1981

Characteristics of Staphylococcus aureus strains from rabbits.

Clumping factor- (slide coagulase-) and DNase-positive staphylococci isolated from lesions and carrier sites in rabbits in Belgium, France and the Netherlands all belonged to the species Staphylococcus aureus. Their biotype characteristics were heterogenic. The great majority of the strains could be allotted to 3 biotypes. One ground showed the characteristics of human S. aureus strains. Other strains belonged to a second group which cannot be associated with a specific host species and the features of most strains which belonged to the third group were similar to those of strains commonly found in pigs. The third group was associated which cutaneous staphylococcosis in young rabbits. Geographic differences in the prevalence of these groups were noted. Many strains were epidemiologically related or belonged to a single phage type which showed evidence of epidemic spread.

Animals↗
PubMedDate not supplied

A one-plate microbiological screening test for antibiotic residue testing in kidney tissue and meat: an alternative to the EEC four-plate method?

A one-plate screening method is described for the microbiological detection of antibiotic residues by growth inhibition of Bacillus subtilis in agar medium, at pH 7, which contains trimethoprim for better detection of sulphonamides. beta-Glucuronidase is added to the samples to enable the detection of chloramphenicol residues. The sensitivity was determined for 16 antimicrobial substances frequently used in animal husbandry. A comparison was made with the sensitivity of the EEC four-plate test and existing maximum residue levels. The method has been used in Belgium for 5 years for the monitoring of antimicrobial residues in kidney tissue and meat of slaughter animals.

Anti-Bacterial Agents↗