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Biomedical subjects

F M Aarestrup

Publications and source records attributed to F M Aarestrup.

At least 91 records · Page 5Linked to original sources
PubMed1997

Avoparcin used as a growth promoter is associated with the occurrence of vancomycin-resistant Enterococcus faecium on Danish poultry and pig farms.

We determined the association between the use of the glycopeptide antibiotic avoparcin as a growth promoter and the occurrence of Enterococcus faecium (VREF) with high-level resistance to vancomycin (MIC > or = 64 micrograms ml-1) on poultry and pig farms. The investigations were conducted as retrospective cohort studies, where groups of farms exposed or not exposed to avoparcin between September 1994 and April 1995 were compared. In poultry, the association between the use of avoparcin and the occurrence of VREF was confounded by the use of broad-spectrum antibiotics, and the adjusted relative risk was 2.9 (1.4-5.9). In pigs, the association had a similar magnitude with a non-adjusted relative risk of 3.3 (0.9-12.3). The similar findings in the two studies provide evidence in favour of a causal association between the use of avoparcin and the occurrence of VREF on farms, and suggest that food animals constitute a potential reservoir of infection for VREF in humans.

Animals↗
PubMed1997

Antimicrobial susceptibility patterns of thermophilic Campylobacter spp. from humans, pigs, cattle, and broilers in Denmark.

The MICs of 16 antimicrobial agents were determined for 202 Campylobacter jejuni isolates, 123 Campylobacter coli isolates, and 6 Campylobacter lari isolates from humans and food animals in Denmark. The C. jejuni isolates originated from humans (75), broilers (95), cattle (29), and pigs (3); the C. coli isolates originated from humans (7), broilers (17), and pigs (99); and the C. lari isolates originated from broilers (5) and cattle (1). All isolates were susceptible to apramycin, neomycin, and gentamicin. Only a few C. jejuni isolates were resistant to one or more antimicrobial agents. Resistance to tetracycline was more common among C. jejuni isolates from humans (11%) than among C. jejuni isolates from animals (0 to 2%). More resistance to streptomycin was found among C. jejuni isolates from cattle (10%) than among those from humans (4%) or broilers (1%). A greater proportion of C. coli than of C. jejuni isolates were resistant to the other antimicrobial agents tested. Isolates were in most cases either coresistant to tylosin, spiramycin, and erythromycin or susceptible to all three antibiotics. More macrolide-resistant isolates were observed among C. coli isolates from swine (79%) than among C. coli isolates from broilers (18%) and humans (14%). Twenty-four percent of C. coli isolates from pigs were resistant to enrofloxacin, whereas 29% of C. coli isolates from humans and none from broilers were resistant. More resistance to streptomycin was observed among C. coli isolates from swine (48%) than among C. coli isolates from broilers (6%) or humans (0%). The six C. lari isolates were susceptible to all antimicrobial agents except ampicillin and nalidixic acid. This study showed that antimicrobial resistance was found only at relatively low frequencies among C. jejuni and C. lari isolates. Among C. coli isolates, especially from swine, there was a high level of resistance to macrolides and streptomycin. Furthermore, this study showed differences in the resistance to antimicrobial agents among Campylobacter isolates of different origins.

Animals↗
PubMed1997

Molecular characterization of Escherichia coli strains isolated from pigs with edema disease.

The present study was conducted to investigate the epidemiological relationship of isolates of Escherichia coli causing edema disease. Classical edema disease has not previously been described in Denmark, but between February 1994 and November 1995 cases appeared in 51 pig herds, among which direct or indirect trading contacts were confirmed for 36 of the herds. A total of 213 isolates from pigs with edema disease in Denmark and other countries and 23 E. coli O139 isolates from pigs with diarrhea or healthy pigs were analyzed to characterize their O serogroups, HindIII ribotypes, and pulsed-field gel electrophoresis (PFGE) types, and 183 of the isolates were also analyzed for their plasmid profiles. The resulting PFGE types of the isolates from pigs with edema disease were examined by cluster analysis. Ten isolates from three herds could not be typed with the available O antisera, whereas all other isolates were of serotype O139. However, all isolates from pigs with edema disease belonged to the same HindIII ribotype, which was not observed among the isolates from pigs with diarrhea or healthy pigs. All isolates from Danish pigs with edema disease except for three isolates originating from two herds belonged to the same or closely related XbaI PFGE types; the other three isolates were assigned to possibly related types. Isolates from pigs with edema disease in different countries belonged to different PFGE types. All isolates from Danish pigs with edema disease grouped together in one cluster, in contrast to isolates from other countries, which did not form any clusters. E. coli strains of serogroup O139 from pigs with diarrhea or isolated from the feces of healthy Danish pigs were very different. Plasmid profiles differed largely among isolates. However, among the isolates from Danish pigs with edema disease, one type predominated within herds. The present study indicated that most, if not all, of the observed cases of edema disease in Denmark were part of the same outbreak. The combination of PFGE typing and ribotyping was useful for studying the possible clonal relationship among strains, whereas plasmid profiling was less informative.

Animals↗
PubMed1997

Prevalence and duration of intramammary infection in Danish heifers during the peripartum period.

Milk samples were collected from 180 heifers from 20 herds around parturition to study the prevalence and persistence of intramammary infection (IMI). A total of 3382 quarter milk samples was collected each week from 4 wk before parturition to 4 wk after parturition. Staphylococcus chromogenes, the most commonly found bacterial species before parturition, was isolated from 15% of all quarters. However, IMI with Staph. chromogenes decreased shortly after parturition to around 1% of quarters. Infectious with Staphylococcus simulans and Staphylococcus epidermidis occurred in 1 to 3% of quarters both before and after parturition. Infections with Staph. simulans persisted in the same quarter for several weeks, but IMI with Staph. epidermidis were transient. Streptococcus dysgalactiae was isolated from 4 to 6% of quarters before and immediately after parturition, but the prevalence of IMI with Strep. dysgalactiae decreased. A strong association existed between IMI with Strep. dysgalactiae before parturition and IMI with Strep. dysgalactiae after parturition, and, using DNA typing, the persistence of 9 IMI was confirmed. Infections with Staphylococcus aureus rarely occurred before parturition, but the rate of IMI with Staph. aureus greatly increased during the 1st wk after parturition. No association was found between bacterial status before parturition and IMI with Staph. aureus after parturition. Overall, the presence of bacterial IMI in a quarter before parturition increased the risk of IMI for the lactating cow. This study demonstrated that variability in prevalence and duration of IMI according to bacterial species occurred around first parturition.

Animals↗
PubMed1997

A study of phage- and ribotype patterns of Staphylococcus aureus isolated from bovine mastitis in the Nordic countries.

This study was conducted to investigate the geographical distribution of phage and ribotypes of Staphylococcus aureus causing bovine mastitis in the 5 Nordic countries. A total of 403 isolates of S. aureus was isolated from 403 different dairy herds. One hundred five strains were isolated in Denmark, 81 in Finland, 17 in Iceland, 96 in Norway and 104 in Sweden. The isolates were phage typed and characterized for their EcoRI restriction fragment length polymorphisms of the genes encoding ribosomal RNA (ribotyping). A total of 351 (87%) of the 403 isolates could be typed by phages assigning them to 25 different phage types. Two to 3 different phage types predominated within each country. One type (29/52) accounted for 36% of all the isolates and was found in 4 of the countries. A total of 87 different ribotypes was found among the isolates investigated. As for phage typing 2 to 3 different types predominated within countries. However, except for one type (ribotype 1), which was commonly found in Denmark, Sweden and Finland, different ribotypes predominated within each country. The combination of phage and ribotyping assigned the isolates to 178 different types. Ninety-six percent of the isolates of ribotype 1 belonged to phage type 29/52. This combined type accounted for 17% of all the 403 isolates. These findings show that a large number of different types of S. aureus can be isolated from cases of bovine mastitis. However, few types predominate within different countries. These predominating types seem to be specific in each country, however, a single type was common for both Denmark, Sweden and Finland. This could suggest differences in the virulence or in modes of transmission of predominating and rare types of S. aureus associated with bovine mastitis.

Animals↗
PubMed1996

Listeria monocytogenes in bovine mastitis. Possible implication for human health.

During the 23-year period 1972 through 1994 quarter milk samples from 1,132,958 cows originating from 36199 herds were examined for the presence of Listeria monocytogenes. Through the period the reference population amounted to 12,742,600 cow years and 401,682 herd years. The percentage of cows infected with L. monocytogenes varied from 0.01 to 0.1% (mean 0.04%) and of herds with an infected cow from 0.2 to 4.2% (mean 1.2%) through the period, showing a low but constant level of infection. A comparison of 33 isolates from bovine mastitis and 27 human clinical isolates was made by sero- and ribotyping. Serotyping showed that all bovine and 17 (63%) of the human isolates belonged to serogroup 1, whereas 10 (37%) of the human isolates belonged to serogroup 4. Ribotyping using EcoRI as restriction enzyme divided the 60 isolates into 16 different types, 7 of which were found among both the bovine and human types. The combination of the typing methods showed that 26 (79%) bovine and 13 (48%) human isolates shared common types. This study showed that a low but constant percentage of Danish dairy herds have cows infected with L. monocytogenes and that some of the bovine types could be found among types causing human infections.

Animals↗
PubMed1996

Genotypic and phenotypic diversity of Streptococcus dysgalactiae strains isolated from clinical and subclinical cases of bovine mastitis.

This study was conducted to characterize Streptococcus dysgalactiae isolated from cases of bovine mastitis. One hundred strains from 100 dairy herds in Denmark, 29 strains from 29 dairy herds in Pennsylvania, USA, 7 reference strains and 18 strains consisting of 9 paired strains from 9 quarters were investigated using biotyping (utilization of tagatose and sorbitol) and HindIII ribotyping. Four different biotypes were observed. Only 34 of the 100 Danish strains utilized either tagatose or sorbitol, 18 utilized tagatose, 15 sorbitol and 1 both tagatose and sorbitol. In contrast, among the American strains one (3.4%) did neither utilize tagatose or sorbitol, twenty (69.0%) utilized tagatose, four (13.8%) sorbitol and four (13.8%) both tagatose and sorbitol. HindIII ribotyping produced 15 different types among all the strains, 9 different types were found among the Danish strains and 8 types among American strains. Five types were observed among both the Danish and the American strains. The 7 reference strains were assigned to 5 different ribotypes. Three type strains (ATCC 27957, NCTC 4670, NCTC 4335) were assigned to a type that was present among both the Danish and the American strains. Ribotyping was the most discriminatory typing method. Agreement between ribo- and biotyping was observed, and especially pronounced among the Danish strains. The 9 paired strains were in case found to have identical ribo- and biotype.

Animals↗
PubMed1996

Epidemiological aspects of group B streptococci of bovine and human origin.

Restriction fragment length polymorphism of the gene encoding rRNA (ribotyping) was used in combination with conventional epidemiological markers to study phenotypic variations among Streptococcus agalactiae of bovine origin and the possible epidemiological interrelationship between the bovine and human reservoirs of Streptococcus agalactiae. The bovine material constituted 53 strains (9 antigen combinations) isolated from 11 herds. Herds with a uniform as well as heterogenic antigenic pattern were included. Furthermore, strains isolated in the course of time from the same persistently infected quarters were examined. The human material constituted 16 strains, 4 each of 4 serotypes, isolated from healthy carriers. Finally, nine serotype- and the group reference strains were examined. All strains were serotyped by double diffusion in agarose gel, biotyped (lactose +/-), and ribotyped using two restriction enzymes, Hind III and HhaI. All isolates could be typed by ribotyping and seven ribotypes were identified among the reference strains. The restriction enzymes used alone or in combination gave typing results that allowed discrimination between and within serotype. Combined use of serotype, Hind III and HhaI ribotypes produced 11 types among the 16 human strains. Ribotype analysis discriminated between herds infected with the same serotype. Strains of varying antigenic patterns from the same herd had the same ribotype. Phenotypic variations in serotype observed in persistent intramammary infection were not related to genetic changes as monitored by ribotype. Two ribotypes were represented among both bovine and human strains. The discriminating capability of lactose fermentation was of limited value.

Animals↗
PubMed1996

Glycopeptide susceptibility among Danish Enterococcus faecium and Enterococcus faecalis isolates of animal and human origin and PCR identification of genes within the VanA cluster.

The MICs of vancomycin and avoparcin were determined for isolates of Enterococcus faecium and isolates of Enterococcus faecalis recovered from the feces of humans and animals in Denmark. Two hundred twenty-one of 376 (59%) isolates of E. faecium and 2 of 133 (1.5%) isolates of E. faecalis were resistant to vancomycin (MICs, 128 to > or = 256 micrograms/ml), and all vancomycin-resistant isolates were resistant to avoparcin (MICs, 64 to > or = 256 micrograms/ml). All vancomycin-resistant isolates examined carried the vanA, vanX, and vanR genes, suggesting that a gene cluster similar to that of the transposon Tn1546 was responsible for the resistance.

Animals↗
PubMed1995

Evaluation of phenotypic and genotypic methods for epidemiological typing of Staphylococcus aureus isolates from bovine mastitis in Denmark.

The value of five different typing methods (antibiogram typing, biotyping, phage typing, plasmid profiling and restriction fragment length polymorphism of the gene encoding 16S and 23S ribosomal RNA (ribotyping)), in discriminating 105 Staphylococcus aureus strains from bovine milk samples obtained from 105 different Danish dairy herds was investigated. A total of 85 strains (81%) proved susceptible to all of the 11 antibiotics tested, and the remaining 20 strains could be divided into 5 different antibiogram patterns. The predominant resistance pattern, penicillin resistance, was observed in 15 (75%) of the 20 antibiotic resistant strains. Biotyping assigned the strains to 14 different types, with the most common type accounting for 25.7% of the strains. Ninety eight (93.3%) strains could be typed by phages, assigning them to 19 different phage types. The predominant phage type accounted for 31.4% of the strains. Eight different plasmid profiles was observed among 24 (23%) strains harbouring plasmids. Ribotyping yielded 30 different types, with the most common accounting for 29.5% of the strains. The single most discriminatory typing method was ribotyping (0.863) followed by biotyping (0.842) and phage typing (0.795). Plasmid profiling (0.395) and antibiogram typing (0.327) had low discriminatory indices. Correspondence among ribotypes and the presence or absence of plasmids were observed, as was some degree of correspondence between ribotype, phage type and biotype. In general the correspondence between phage type and ribotype were stronger than between biotype and ribotype and between biotype and phage type. All combinations of two or more methods led to an improved index of discrimination compared to the individual methods indicating, that some subdivision of types had taken place. The combination of phage, bio- or ribotyping or all three methods in combination are considered to be an efficient combination of typing methods for epidemiological investigation of S. aureus mastitis.

Animals↗
PubMed1995

Analysis of associations between major histocompatibility complex (BoLA) class I haplotypes and subclinical mastitis of dairy cows.

The associations between BoLA class I haplotypes and subclinical mastitis were investigated using information on 333 cows from three different breeds and crossbreeds from 14 dairy herds in Denmark. Somatic cell count and bacteriological status were used as markers for subclinical mastitis. Associations between BoLA class I haplotypes and IMI status were also determined. The association between BoLA class I haplotypes and subclinical mastitis was weak. The A10(W50), A11, A12(A30), A16, A19(A6), A21, A26, and A31(A30) alleles were associated with different markers of subclinical mastitis. Susceptibility or resistance to the two bacteria categories was associated with different alleles. This study indicated that BoLA antigens may be involved in resistance to mastitis and that resistance may be specific for a particular pathogen.

Alleles↗
PubMed1995

A comparative study of Staphylococcus aureus strains isolated from bovine subclinical mastitis during 1952-1956 and 1992.

Fifty-two strains of S. aureus isolated from cases of bovine subclinical mastitis in 52 different dairy herds in Denmark, in the periods 1952 to 1956 and 1992, were compared with regard to their phage- and EcoRI ribotypes. Furthermore, susceptibility to penicillin and production of fibrinolysin were used as additional phenotypic markers. Forty-nine strains (94%) could be separated into 12 phage types. Ribotyping assigned the 52 strains to 21 different types. Both methods showed that 57% of the 1950's strains and between 38-45% of the 1992 strains belonged to 3 dominating types. The remaining strains were placed by ribotyping in 8 types occurring among the 1952-1956 strains and 10 types occurring among the 1992 strains. In 87% of the strains the results of the 2 typing methods were in accordance. However, 7 strains gave different results by the 2 methods including 2 strains with major differences. Penicillin resistance only occurred in a single genotype from the 1950's compared to 6 different genotypes among the 1992 strains.

Animals↗
PubMed1995

Prevalence of coagulase gene polymorphism in Staphylococcus aureus isolates causing bovine mastitis.

This study was conducted to investigate polymorphism of the coagulase gene of Staphylococcus aureus causing bovine mastitis. One hundred eighty-seven strains of S. aureus were isolated from bovine mastitic milk samples obtained from 187 different Danish dairy farms. The isolates were characterised for restriction fragment length polymorphism (RFLP) of the coagulase gene. A variable region of the coagulase gene was amplified using the polymerase chain reaction (PCR) followed by AluI restriction enzyme digestion. A total of 15 different RFLP patterns were observed. The predominant pattern was found in 35% of the isolates. The ease of analysing coagulase gene polymorphisms among a large number of strains, and the multiple distinct polymorphic patterns generated, supports the use of this technique in epidemiological investigations of bovine mastitis. The predominating variants may have predelection for causing intramammary infections.

Animals↗
PubMed1995

The effect of thalidomide on BCG-induced granulomas in mice.

Granuloma proliferation is the result of a series of complex biological events in which a variety of cell types and cytokines are involved. Tumor necrosis factor alpha (TNF-alpha) plays a central role. In the present study, we investigated the effect of thalidomide (alpha-N-pthalimidoglutarimide), a selective inhibitor of TNF-alpha synthesis, on granuloma formation during BCG infection in Oncins France 1 (OF-1) mice. Subcutaneous injections of 30 mg/kg body weight of thalidomide daily for 14, 21 or 28 days into the mice resulted in the reduction of the size and total number of liver granulomas. The most striking effect of thalidomide was observed after 28 days, when the total number of liver granulomas was reduced by as much as 40% (P < 0.05). Serum TNF-alpha levels of thalidomide-treated mice were significantly lower (85%) than control mice on day 14 and remained lower (55%) on days 21 and 28. Positive immunohistochemical staining specific for TNF-alpha were demonstrable only in well-developed granulomas in which central mononuclear cells presented extensive differentiation into epithelioid cells. Daily administration of thalidomide for 21 to 28 days to the BCG-infected mice inhibited local TNF-alpha expression in well-developed granulomas. The mechanisms by which thalidomide modulates the granuloma proliferation are discussed.

Animals↗