Development of a hierarchical typing approach for Mycobacterium avium subsp. paratuberculosis (MAP) and characterization of MAP field cultures from Central Germany.

AIMS: Development of a novel hierarchical Mycobacterium avium subsp. paratuberculosis (MAP) typing approach and characterization of MAP field cultures in Central Germany. METHODS AND RESULTS: By combining single nucleotide polymorphisms (SNPs) and mycobacterial interspersed repetitive unit-variable number tandem repeat, we developed a highly discriminating and phylogenetically accurate hierarchical MAP typing approach. Moreover, a novel stepwise workflow was employed to reduce the number of SNP reactions required making the typing approach more affordable. MAP field cultures (n = 142) from dairy herds in Central Germany were classified as cattle type and showed a high level of heterogeneity. Intra-herd multiple genotypes were evident in (13-25%) of the investigated herds. CONCLUSIONS: The hierarchical MAP typing approach proved to be useful in fine discrimination between MAP cultures within limited geographical regions. This could potentially be used in unravelling MAP transmission chains in the respective regions. The observed heterogeneity in some herds is assumed to be due to either multiple introductions through inter-herd trade or intra-herd evolution over time. SIGNIFICANCE AND IMPACT OF THE STUDY: Future MAP epidemiological studies will benefit from the advantages of the novel hierarchical typing approach. The SNP number reduction approach employed here could be extrapolated for other analogous pathogens.

The role of 'atypical' Brucella in amphibians: are we facing novel emerging pathogens?

AIMS: To discuss together the novel cases of Brucella infections in frogs with the results of published reports to extend our current knowledge on 'atypical' brucellae isolated from amphibians and to discuss the challenges we face on this extraordinary emerging group of pathogens. METHODS AND RESULTS: Since our first description, an additional 14 isolates from four different frog species were collected. Novel isolates and a subset of Brucella isolates previously cultured from African bullfrogs were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), Fourier transform-infrared (FT-IR) spectroscopy and broth microdilution susceptibility testing. MALDI-TOF MS worked very efficiently for an accurate bacterial identification to the genus level. Within the cluster analysis, 'atypical' brucellae grouped distant from Brucella melitensis and were even more separated by FT-IR spectroscopy with respect to their geographical origin. Minimum inhibitory concentrations of 14 antimicrobial substances are provided as baseline data on antimicrobial susceptibility. CONCLUSIONS: The case history of Brucella infections in amphibians reveals a variety of pathologies ranging from localized manifestations to systemic infections. Some isolates seem to be capable of causing high mortality in zoological exhibitions putting higher demands on the management of endangered frog species. There is considerable risk in overlooking and misidentifying 'atypical' Brucella in routine diagnostics. SIGNIFICANCE AND IMPACT OF THE STUDY: Brucella have only recently been described in cold-blooded vertebrates. Their presence in frog species native to Africa, America and Australia indicates a more common occurrence in amphibians than previously thought. This study provides an extensive overview of amphibian brucellae by highlighting the main features of their clinical significance, diagnosis and zoonotic potential.

First report of MIRU-VNTR genotyping of Mycobacterium avium subsp. paratuberculosis isolates from Egypt.

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease, an economically important disease in ruminants worldwide. It was first isolated in Egypt in 2005. Since then, the pathogen has been detected in different Egyptian provinces. In order to trace the source of infection, genotyping using simple methods of high discriminatory power such as mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR) were carried out in different countries. Until now there is no published information about MIRU-VNTR genotyping of MAP isolates in Egypt. To address that point, 100 faecal samples were collected and cultivated from 3 different suspected dairy farms. Fourteen isolates belonging to one farm were identified as MAP and subjected to genotyping using 8 different MIRU-VNTR loci PCRs. Two different genotypes were recognized based on size polymorphism observed in one locus (VNTR-7) that was confirmed by sequencing. Our work provides a preliminary basis of constructing a MIRU-VNTR genotyping database of MAP in Egypt.

Mycobacterium tuberculosis exposure of livestock in a German dairy farm: implications for intra vitam diagnosis of bovine tuberculosis in an officially tuberculosis-free country.

Germany has been an officially bovine tuberculosis (bTB)-free (OTF) country since 1996. Gradually rising numbers of bTB herd incidents due to Mycobacterium bovis and M. caprae in North-Western and Southern Germany during the last few years prompted the competent authorities to conduct a nationwide bTB survey in 2013/2014. This led to the detection of a dairy herd in which as many as 55 cattle reacted positively to consecutive intra vitam testing. Test-positive animals lacked visible lesions indicative of bTB at necropsy. Extensive mycobacterial culturing as well as molecular testing of samples from 11 tissues for members of the M. tuberculosis complex (MTC) yielded negative results throughout. However, caseous lymphadenitis of Ln. mandibularis accessorius was observed during meat inspection of a fattening pig from the same farm at regular slaughter at that time. Respective tissue samples tested MTC positive by polymerase chain reaction, and M. tuberculosis T1 family were identified by spoligotyping. Four human reactors within the farmer's family were also found to be immunoreactive. As exposure of livestock to M. tuberculosis is not generally considered, its impact may result in regulatory and practical difficulties when using protocols designed to detect classical bTB, particularly in OTF countries.

CD2/CD21 index: a new marker to evaluate udder health in dairy cows.

Lymphocytes play a significant role in the immunological processes of the bovine mammary gland and were found to be the dominant cell population in the milk of healthy udder quarters. The objective of this study was to investigate the quantitative relationship between CD2(+) T and CD21(+) B lymphocytes using flow cytometry. In a first study, quarter foremilk samples from apparently healthy udder quarters [somatic cell counts (SCC) ≤100,000 cells/mL; n=65] were analyzed and compared with diseased quarters (SCC >100,000 cells/mL; n=15). Percentages of CD2(+) T cells were significantly higher in milk samples with SCC ≤100,000 cells/mL than in those with SCC >100,000 cells/mL, whereas percentages of CD21(+) B cells developed in the opposite direction. As a result of this opposing trend, a new variable, the CD2/CD21 index-representing the percentages of CD2(+) cells per CD21(+) cells-was defined. Although diseased quarters with SCC >100,000 cells/mL and the detection of major pathogens revealed generally CD2/CD21 indices <10, values >10 were observed in apparently healthy quarters. Hence, a CD2/CD21 index cutoff value of 10 may be suitable to aid differentiation between unsuspicious and microbiologically suspicious or diseased udder quarters. To test whether CD2/CD21 indices <10 were primarily related to pathogens, quarters with SCC ≤100,000 cells/mL and >100,000 cells/mL with different bacteriological status (culture negative, or minor or major pathogens) were selectively examined in a second biphasic study. In the first trial, 63 udder quarters were analyzed and 55 of these quarters were able to be sampled again in the second trial carried out 14 d later. In both trials, results of the first study were confirmed. Indeed, CD2/CD21 indices <10 were also found in quarters showing SCC ≤100,000 cells/mL and containing minor or major pathogens at the time of the current or previous bacteriological analysis. The results of our examinations indicated a clear relationship between the CD2/CD21 index and the bacteriological status of the mammary gland. In combination with SCC, it offers a new marker for quick differentiation of unsuspicious and microbiologically suspicious or diseased udder quarters.

Isolation and identification of main mastitis pathogens in Mexico / Isolação e identificação dos micróbios patogênicos principais da mastite em México

The present work is a large epidemiological study aiming to detect the prevalence of subclinical mastitis and to investigate the major udder pathogens in Jalisco State, western Mexico. For this purpose, 2205 dairy cows, representing 33 Mexican dairy herds, were involved. Of 2205 cows, 752 mastitic animals were diagnosed and only 2,979 milk samples could be obtained for further investigation. All 2979 milk samples were subjected to California Mastitis Test (CMT) to differentiate clinical cases from subclinical ones where 1996 samples (67 %) reacted positively. Of these, 1087 samples (54.5%) came from cows suffering from clinical cases of mastitis. Bacteriological identification of the causative agents revealed the presence of a major group of pathogens including the Coagulase negative staphylococci (CNS), S.aureus, S.agalactiae, Corynebacterium spp. and Coliform bacteria which were detected in 464 (15.6%), 175 (5.9%), 200 (6.8%), 417 (14%) and 123 (4.1%) of the 2927 investigated quarters, 295 (15.4%), 118 (15.7%), 111 (14.8%), 227 (30.2%) and 109 (14.5%) of the 752 examined cows and in 33 (100%), 22 (66.7%), 19 (57.6%), 30 (90.1%) and 27 (81.8%) of the 33 herds involved, respectively. Other pathogens could be detected in the investigated milk samples such as S. dysgalactiae (0.4%), S.uberis (0.37%), Bacillus spp. (1%), Nocardia spp. (0.6%) und Candida spp. (0.1%). Meanwhile, others were present in a negligible ratio; including the Aerococcus viridans, and Enterococcus spp., Lactococcus lactis, S. bovis.

O trabalho atual é um estudo epidemiológico que objetiva detectar a predominância da mastite subclínica e investigar os micróbios patogênicos principais do úbere no México ocidental. Com esta finalidade, foram utilizadas 2205 vacas leiteiras, representando 33 rebanhos de leiteiras mexicanas. Além dessas 2205 vacas, 752 animais com mastite foram diagnosticados, considerando-se que somente 2979 amostras do leite poderiam ser obtidas para a posterior investigação. Todas as 2979 amostras do leite foram submetidas ao teste da mastite de Califórnia (CMT) para diferenciar casos clínicos dos subclínicos, visto que 1996 amostras (67%) reagiram positivamente. Além dessas, 1087 amostras (54.5%) vieram das vacas que sofrem de casos clínicos de mastite. A identificação bacteriológica dos agentes causais revelou a presença dos Staphylococcus negativos para coagulase (CNS), S. aureus, S. agalactiae, outros spp. Streptococcal, Corynebacterium spp., e as bactérias de coliformes foram detectadas em 464 (15.6%), 175 (5.9%), 200 (6.8%), 109 (3.9%), 417 (14%) e em 123 (4.1%) dos 2927 quartos investigados; em 295 (15.4%), 118 (15.7%), 111 (14.8%), 95 (12.6%), 227 (30.2%) e em 109 (14.5%) das 752 vacas examinadas e, finalmente, em 33 (100%), 22 (66.7%), 19 (57.6%), 30 (90.1%), 30 (90.1%) e em 27 (81.8%) dos 33 rebanhos envolvidos, respectivamente.

First description of Trueperella (Arcanobacterium) bernardiae of animal origin.

In the present study a Trueperella (Arcanobacterium) bernardiae strain isolated from an anal swab of a three-day-old piglet could be identified phenotypically, by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and genotypically by sequencing the 16S rDNA, the 16S-23S rDNA intergenic spacer region (ISR) and by sequencing the superoxide dismutase A encoding gene sodA. The present study gives the first information about the presence of T. (A.) bernardiae in specimen of animals.

Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for species identification of bacteria of genera Arcanobacterium and Trueperella.

In the present study matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was evaluated for species identification of 98 bacteria previously classified phenotypically and genotypically to genera Arcanobacterium and Trueperella. Species identification was carried out by comparing the main spectra of each strain with the main spectra of reference strains of both genera and 3740 database entries included in the MALDI Biotyper 2.0 software package (Bruker Daltonik GmbH, Bremen, Germany). MALDI-TOF MS correctly identified (log (score) values ≥ 2.0) all investigated strains of the species A. (T.) bialowiezense (n=3), A. (T.) bonasi (n=7), A. haemolyticum (n=10), A. pluranimalium (n=1) and A. (T.) pyogenes (n=77). According to the present results MALDI-TOF MS had a comparable discriminating power than previously conducted tests on DNA level. Further studies with strains isolated from human infections would show the robustness of MALDI-TOF MS for identification of bacteria of these genera.

Flow cytometric differential cell counts in milk for the evaluation of inflammatory reactions in clinically healthy and subclinically infected bovine mammary glands.

Somatic cell counts (SCC) are generally used as an indicator of udder health. In Germany, a cutoff value of 100,000 cells/mL is currently used to differentiate between healthy and diseased mammary glands. In addition to SCC, differential cell counts (DCC) can be applied for a more detailed evaluation of the udder health status. The aim of this study was to differentiate immune cells in milk of udder quarters classified as healthy based on SCC values of <100,000 cells/mL. Twenty cows were selected and 65 healthy udder quarters were compared with a control group of 15 diseased udder quarters (SCC>100,000 cells/mL). Cells were isolated from milk of all quarters to measure simultaneously percentages of lymphocytes, macrophages, and polymorphonuclear neutrophilic leukocytes (PMNL) by flow cytometric analysis. The bacteriological status of all 80 quarters was also determined. Differential cell count patterns of milk samples (n = 15) with extreme low SCC values of ≤ 6,250 cells/mL revealed high lymphocyte proportions of up to 88%. Milk cell populations in samples (n = 42) with SCC values from >6,250 to ≤ 25,000 cells/mL were also dominated by lymphocytes, whereas DCC patterns of 6 out of 41 milk samples with SCC values from ≥ 9,000 to ≤ 46,000 cells/mL indicated already inflammatory reactions based on the predominance of PMNL (56-75%). In 13 of 15 milk samples of the diseased udder quarters (SCC >100,000 cells/mL), PMNL were categorically found as dominant cell population with proportions of ≥ 49%. Macrophages were the second predominant cell population in almost all samples tested in relation to lymphocytes and PMNL. Further analysis of the data demonstrated significant differences of the cellular components between udder quarters infected by major pathogens (e.g., Staphylococcus aureus; n = 5) and culture-negative udder quarters (n = 56). Even the percentages of immune cells in milk from quarters infected by minor pathogens (e.g., coagulase-negative staphylococci; n = 19) differed significantly from those in milk of culture-negative quarters. Our flow cytometric analysis of immune cells in milk of udder quarters classified as healthy by SCC <100,000 cells/mL revealed inflammatory reactions based on DCC.

Genetic relatedness of methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolated from a dog and the dog owner.

In the present study four methicillin-resistant Staphylococcus pseudintermedius (MRSP) strains isolated from a dog (n=3) and the anterior nares of the dog owner (n=1) were investigated by conventional and molecular methods. The species identity of the four S. pseudintermedius strains was confirmed by conventional methods, by PCR mediated amplification of S. intermedius/S. pseudintermedius specific segments of thermonuclease encoding gene nuc and by restriction fragment length polymorphism analysis of phosphoacetyltransferase encoding gene pta. Investigation of the four S. pseudintermedius for toxinogenic potential revealed that all four strains were positive for the exfoliative toxin encoding gene siet and the leukotoxin encoding genes lukS, lukF. The oxacillin and penicillin resistance of the four S. pseudintermedius strains could be determined by cultivation of the strains on oxacillin resistant screening agar base, ChromID MRSA Agar and Brilliance MRSA Agar and by multiplex PCR detecting the resistance genes mecA and blaZ. The genetic relatedness of the strains was studied by macrorestriction analysis of their chromosomal DNA using pulsed field gel electrophoresis (PFGE). According to PFGE all four S. pseudintermedius strains represent an identical bacterial clone indicating a cross transmission between the dog and the dog owner.

Molecular identification and further characterization of Arcanobacterium pyogenes isolated from bovine mastitis and from various other origins.

The present study was designed to identify phenotypically and genotypically 61 Arcanobacterium pyogenes isolated from bovine mastitis and from various other origins. The A. pyogenes isolates showed the typical cultural and biochemical properties of this species and displayed CAMP-like synergistic hemolytic activities with various indicator strains. The species identity could be confirmed genotypically by amplification and sequencing of the superoxide dismutase A encoding gene sodA of reference strains representing 8 species of genus Arcanobacterium and subsequent design of A. pyogenes sodA gene-specific oligonucleotide primer. The A. pyogenes sodA gene-specific oligonucleotide primer allowed, together with previously described A. pyogenes 16S-23S rDNA intergenic spacer region-specific oligonucleotide primer, a reliable molecular identification of all 61 A. pyogenes of various origins. The additionally performed PCR-mediated amplification of 5 known and putative virulence factor encoding genes revealed that 100, 20, 87, 75, and 98% of the A. pyogenes carried the genes plo, cbpA, nanH, nanP, and fimA, which allowed an individual strain characterization. This might help to elucidate the role the putative virulence factors play in bovine mastitis and in various other infections caused by this bacterial pathogen.

Characterization of Arcanobacterium abortisuis by phenotypic properties and by sequencing the 16S-23S rDNA intergenic spacer region.

The present study was designed to characterize phenotypically and genotypically nine Arcanobacterium abortisuis strains collected from specimen of pigs in a period of nine years. All nine A. abortisuis strains and A. abortisuis reference strain DSM 19515 displayed a synergistic hemolytic reaction with Staphylococcus aureus ß-hemolysin, Rhodococcus equi, and Arcanobacterium haemolyticum indicator strains and showed the typical biochemical properties of this species. The species identity could be confirmed by identification and sequencing of the 16S-23S rDNA intergenic spacer region (ISR), which appeared to be a useful target for genotypic characterization of this bacterial species. The A. abortisuis strains of the present study were isolated from specimen of pigs together with various other bacterial species indicating that the pathogenic importance of this newly described species remains to be elucidated.

Somatic cell counts and bacteriological status in quarter foremilk samples of cows in Hesse, Germany--a longitudinal study.

Somatic cell counts (SCC) are generally used as an indicator of udder health. Currently in Germany, 100,000 cells/mL is the threshold differentiating infected and noninfected mammary glands. The aim of our study was the detailed analysis of udder health in a representative part of the dairy cow population in Hesse, Germany. Between 2000 and 2008, 615,187 quarter foremilk samples were analyzed. In addition to evaluation of distribution of SCC and prevalence of mastitis pathogens, pathogen prevalence was also calculated depending on SCC. The data indicated that 38% of all samples had SCC >100,000 cells/mL and 62% showed SCC ≤ 100,000 cells/mL; 31% of all samples revealed SCC ≤ 25,000 cells/mL. Coagulase-negative staphylococci were the dominant pathogens in the Hessian quarter foremilk samples (17.17% of all samples) followed by Corynebacterium spp. (13.56%), Streptococcus uberis (8.7%), and Staphylococcus aureus (5.01%). Mastitis pathogens were detected in 83% of all samples with SCC >100,000 cells/mL. However, the prevalence of mastitis pathogens in the SCC range from 1,000 to ≤ 100,000 cells/mL was 8.5% (5.51% minor pathogens, 2.01% major pathogens, and 0.98% other pathogens). For farms producing high quality milk, exceptional hygiene management is compulsory. One of the farms randomly selected showed clearly different results from the Hessian survey. Fifteen percent more samples lay in the SCC range ≤ 100,000 cells/mL with a lower prevalence of mastitis pathogens of 1.91% (1.03% minor pathogens, 0.83% major pathogens, and 0.05% other pathogens). Based on these results, inflammatory processes can obviously be detected in mammary glands of udder quarters healthy according to the current definitions. However, we argue that such inflammation can be detected by examination of the relationship of immune cells in milk.

Identification of Arcanobacterium pyogenes isolated by post mortem examinations of a bearded dragon and a gecko by phenotypic and genotypic properties.

The present study was designed to identify phenotypically and genotypically two Arcanobacterium (A.) pyogenes strains isolated by post mortem examinations of a bearded dragon and a gecko. The A. pyogenes strains showed the typical biochemical properties and displayed CAMP-like synergistic hemolytic activities with various indicator strains. The species identity could be confirmed genotypically by amplification and sequencing of the 16S rDNA gene and, as novel target gene, by sequencing of the beta subunit of RNA polymerase encoding gene rpoB, of both strains and of reference strains representing nine species of the genus Arcanobacterium. The species identity of the two A. pyogenes strains could additionally be confirmed by PCR mediated amplification of species specific parts of the 16S-23S rDNA intergenic spacer region, the pyolysin encoding gene plo and by amplification of the collagen-binding protein encoding gene cbpA. All these molecular targets might help to improve the future identification and further characterization of A. pyogenes which, as demonstrated in the present study, could also be isolated from reptile specimens.

Identification of Arcanobacterium haemolyticum isolated from postcastrational complications of a horse.

An Arcanobacterium haemolyticum strain isolated from a postcastrational lesion of a horse was identified phenotypically and genotypically. The latter was performed by sequencing the 16S-23S rDNA intergenic spacer region (ISR), by amplification of the gene encoding A. haemolyticum phospholipase D, by amplification of A. haemolyticum specific parts of ISR-23S rDNA and by amplification of the newly described CAMP factor family protein encoding gene of A. haemolyticum. This indicates (as described previously for seven additional A. haemolyticum strains; Hassan et al. 2009) that A. haemolyticum seems to occur also in infections of horses.

Synergistic and antagonistic hemolytic activities of bacteria of genus Arcanobacterium and CAMP-like hemolysis of Arcanobacterium phocae and Arcanobacterium haemolyticum with Psychrobacter phenylpyruvicus.

A total of 57 bacteria representing eight species of genus Arcanobacterium (A.) were investigated for hemolytic properties on blood agar containing sheep and rabbit blood and for CAMP-like reactions. An enhanced hemolysis on blood agar containing rabbit blood compared to sheep blood could be observed for A. haemolyticum, less pronounced for A. hippocoleae and A. pluranimalium. A synergistic hemolytic reaction with staphylococcal beta-hemolysin appeared to be constantly visible for A. hippocoleae, A. pluranimalium and A. pyogenes, with Streptococcus agalactiae for A. phocae and A. haemolyticum, with Rhodococcus equi for A. phocae, A. haemolyticum, A. pluranimalium and A. pyogenes and with A. haemolyticum for A. hippocoleae, A. pluranimalium and A. pyogenes, respectively. A reverse CAMP-reaction in the zone of staphylococcal beta-hemolysin could be observed for A.phocae and A.haemolyticum. In addition, a novel CAMP-like reaction could be noted between Psychrobacter phenylpyruvicus, identified by 16S rDNA sequencing, and A. phocae and A. haemolyticum. These synergistic or antagonistic hemolytic properties could possibly be used as additional criteria for identification of bacteria of genus Arcanobacterium.

Phenotypic and genotypic characterization of Staphylococcus aureus isolated from raw camel milk samples.

In the present study 320 milk samples collected from 160 apparently healthy camels of three different locations in Sudan were investigated for the presence of Staphylococcus aureus resulting in the isolation of this bacterial pathogen from 28 milk samples from 24 camels. Twenty-five S. aureus were identified phenotypically and by PCR mediated amplification of species-specific genes or gene segments. Investigation of the S. aureus for toxinogenic potential revealed that three S. aureus strains were positive for the enterotoxin encoding gene sec and the genes seg, sei, sem, sen and seo, representing the egc gene cluster. In addition all 25 S. aureus were positive for the superantigen-like encoding gene ssl7 (set1). Partial sequencing of gene sec of the three S. aureus strains yielded an almost complete sequence identity to the sequence of the sec variant sec2. However, all three sec2 genes of the present study showed a deletion of one base causing a frame shift and a corresponding earlier stop codon. According to the present results, the raw camel milk collected from three locations in Sudan seems to be, at least at this stage, of minor importance as vector causing staphylococcal food poisoning.

Molecular identification of Arcanobacterium bialowiezense and Arcanobacterium bonasi based on 16S-23S rRNA intergenic spacer region sequences.

In the present study, the 16S-23S rDNA intergenic spacer region (ISR) of Arcanobacterium (A.) bialowiezense DSM 17162, A. bonasi DSM 17163, A. bernardiae DSM 9152, A. haemolyticum DSM 20595, A. hippocoleae DSM 15539, A. phocae DSM 10002, A. pluranimalium DSM 13483 and A. pyogenes DSM 20630 was amplified, sequenced and compared with the corresponding 16S rRNA gene sequences yielding comparable phylogenetic relationships. The ISR sequence of A. bialowiezense and A. bonasi allowed the design of species-specific oligonucleotide primers which could successfully be used for PCR-mediated identification of previously characterized A. bialowiezense and A. bonasi isolated from infections of the European bison. The presented molecular identification might help to improve a future diagnosis of both newly described bacterial pathogens.

Genotyping of Staphylococcus aureus isolated from humans, bovine subclinical mastitis and food samples in Argentina.

The aim of the present study was to characterize genotypically 45 Staphylococcus aureus strains isolated from humans, bovine subclinical mastitis and food samples in Argentina by rep-PCR and PCR amplification of virulence genes. Resistances to various antibiotics could be observed for the human S. aureus, less pronounced for the bovine strains, but not for the eight S. aureus isolated from food samples. The strains could be classified genotypically by rep-PCR and by amplification of the genes encoding protein A, coagulase, clumping factor, the collagen adhesin domains A and B, capsular polysaccharide 5 and 8, the accessory gene regulator agr classes I to III, and the S. aureus gene regulator sae. rep-PCR analyses and the different gene patterns revealed that the strains could be divided into seven groups mostly matching with the origin of the isolates. The present study describes genotypic variations of S. aureus strains isolated from different origins in Argentina. The study provides a valuable insight into molecular specificities of this important pathogen.