Porcine Strains Research Articles

Genotypic and phenotypic characterisation of Escherichia coli strains associated with porcine pyelonephritis

Urinary tract infection (UTI) is a severe problem in humans as well as in many domestic animals like pigs. The most frequent infectious agent in UTI is uropathogenic Escherichia coli. Such strains have been extensively characterised with respect to virulence and fitness factors as well as clonal type when it comes to human isolates. However, relatively little has been done to characterise the corresponding porcine strains. On this background we have analysed 20 porcine pyelonephritis E. coli strains isolated from infected pig kidneys. The strains were quite distinct from that of human uropathogenic strains with regards to adhesion profile and haemolysin production. Also, the clonal profiles differed from that of human infections since our strains all belonged to the E. coli clonal groups A and B1.

Detection and Characterization of Group C Rotaviruses in Asymptomatic Piglets in Ireland

Group C rotaviruses are important human enteric pathogens that have also been detected in a variety of mammalian species, including pigs. Group C rotaviruses have been identified in piglets with diarrhea, but their ecology remains to be elucidated. By screening of 292 fecal samples collected from 4- to 5-week-old asymptomatic pigs from four herds in Ireland between 2005 and 2007, 13 (4.4%) samples tested positive by reverse transcription-PCR for group C rotavirus. Group A rotaviruses were also detected in 19 samples but not in conjunction with group C viruses. The gene encoding the major group C neutralization antigen, the outer capsid protein VP7, was sequenced. The majority of the strains were very closely related to each other (>99% amino acid [aa] identity) and were characterized as genogroup G1 since they were genetically related to the prototype porcine strain Cowden (92.6% aa identity). Conversely, two strains (1GA/05/Cork/Ire and 281/07/Dublin/Ire) were characterized as genogroup G6 since they displayed the highest identity (89.2 to 94.0% aa) to porcine G6 strains (43/06-22-like). Unexpectedly, one such G6 strain, 1GA/05/Cork/Ire, lacked the 4-aa insertion in the VP7 variable region VR8 found in all the other G6 group C rotaviruses. This study provides evidence that porcine group C rotavirus may be detected not infrequently in asymptomatic piglets. In addition, it provides evidence that, unlike the human viruses, porcine group C rotaviruses display broad genetic heterogeneity, which may pose a challenge for the development of prophylactic tools.

Molecular detection of norovirus in sheep and pigs in New Zealand farms

Human norovirus (NoV) is reportedly the major cause of non-bacterial gastroenteritis outbreaks worldwide and is commonly associated with water- and food-borne transmission via the faecal–oral route. Aside from humans, norovirus has been detected in pigs, cattle and mice. The close relatedness of some human and animal noroviruses has raised concerns about potential zoonotic transmission. Our laboratory recently reported the development of a multiplex real-time RT-PCR for the detection and genotyping of norovirus of genogroups I–III. Here we report a study of 56 faecal specimens from pigs and sheep that were collected and screened for noroviruses using this assay. Norovirus was found in 2/23 (9%) of porcine specimens (all were genogroup II) and in 8/33 (24%) of ovine specimens (all were genogroup III). Samples tested positive for norovirus were verified by conventional RT-PCR with different primer sets. Genomes of representative porcine and ovine norovirus strains underwent partial sequence analysis (343 and 2045 bases, respectively). This is the first report describing norovirus in sheep.

Human, porcine and bovine rotaviruses in Slovenia: evidence of interspecies transmission and genome reassortment

A surveillance of human, porcine and bovine rotaviruses was carried out in Slovenia in 2004 and 2005. Stool samples were collected from a total of 406 pigs (373 from asymptomatic animals), 132 cattle (126 from asymptomatic animals) and 241 humans (all with diarrhoea), tested for group A rotaviruses using RT-PCR and analysed by sequencing. The aims of the study were to determine the incidence of asymptomatic rotavirus infection in animals, to look for evidence of zoonotic transmission and to detect reassortment among rotaviruses. The rates of asymptomatic shedding of rotaviruses in pigs and cattle were 18.0 % (67/373) and 4.0 % (5/126), respectively. Evidence for zoonotic transmission was detected in one human rotavirus strain, SI-MB6, with the G3P[6] genotype combination, as the nucleotide and predicted amino acid sequences of the VP6, VP7, VP8* and NSP4 genes of strain SI-MB6 and of porcine strains showed high nucleotide and amino acid sequence identity. Two porcine rotavirus strains carried VP7 of probable human origin, suggesting an interspecies reassortment event in the past.

Epidemiological Data on PathogenicYersinia enterocoliticain Southern Germany During 2000–2006

Yersinia enterocolitica is the most common species causing enteric yersiniosis, which is still the third most frequently reported foodborne gastroenteritis in Europe. Y. enterocolitica generally causes sporadic human infections, and outbreaks are rare. The most important infection source of yersiniosis is believed to be contaminated pork and pork products. Data on the prevalence of pathogenic Y. enterocolitica in animals and foodstuffs are very limited and old; thus, more information on the extent and range of the prevalence of this enteropathogen in nonhuman sources is needed. In this work, prevalence of pathogenic Y. enterocolitica in different sources in Bavaria is presented. Further, the antimicrobial resistance of human and nonhuman strains is reported. The highest isolation rate of pathogenic Y. enterocolitica (67%) was found in tonsils of slaughter pigs. No pathogenic strains were isolated from cattle, sheep, turkey, and horses. ail-Positive Y. enterocolitica was detected in dogs (5%), cats (3%), and rodents (3%) by real-time PCR. Pathogenic Y. enterocolitica was isolated only from raw pork, especially from edible offal (51%). Surprisingly, 38% of game was contaminated with this pathogen when the samples were studied with PCR. Additionally, some raw pork sausages and one poultry sample were PCR positive. All pathogenic Y. enterocolitica isolates from nonhuman sources were belonging to bioserotype 4/O:3. Antimicrobial resistance of 60 human and 140 porcine strains of bioserotype 4/O:3 was tested by the agar disc diffusion method to 15 different antimicrobial agents. All Y. enterocolitica 4/O:3 strains were susceptible to most of the tested antibacterial agents.

Detection and Quantification of Group C Rotaviruses in Communal Sewage

Group C rotaviruses have been recognized as a cause of acute gastroenteritis in humans, cattle, and swine, although the true epidemiologic and clinical importance of this virus in these hosts has not yet been fully established. A real-time PCR assay based on a broadly reactive primer pair was developed and used to quantitatively determine the viral load of group C rotaviruses in environmental samples. A total of 35 raw and 35 treated sewage samples collected at the same sampling time in four Hungarian sewage treatment plants during a survey in 2005 were tested for the presence of group C rotaviruses. The overall detection rates were 91% (32 of 35) for the influent and 57% (20 of 35) for the effluent samples. Molecular characterization of the amplified partial VP6 gene revealed the cocirculation of human and animal (i.e., bovine and porcine) strains that were easily distinguishable by melting curve analysis. Human strains yielded relatively high viral loads (mean, 1.2 x 10(7); median, 6.9 x 10(5) genome equivalents per liter influent sewage) and appeared to display seasonal activity over the study period, whereas animal strains appeared to circulate throughout the year at much lower average titers (bovine strains mean, 9.9 x 10(4); median, 3.0 x 10(4); porcine strains mean, 3.9 x 10(4); median, 3.1 x 10(4) genome equivalents per liter influent sewage). Our findings suggest that monitoring of communal sewage may provide a good surrogate for investigating the epidemiology and ecology of group C rotaviruses in humans and animals.

Genetic heterogeneity in the VP7 of group C rotaviruses

Evidence for a possible zoonotic role of group C rotaviruses (GCRVs) has been recently provided. To gain information on the genetic relationships between human and animal GCRVs, we sequenced the VP7 gene of 10 porcine strains detected during a large surveillance study from different outbreaks of gastroenteritis in piglets. Four GCRV strains were genetically related to the prototype GCRV porcine Cowden strain. A completely new VP7 genotype included 4 strains (344/04-7-like) that shared 92.5% to 97.0% aa identity to each other, but < 83% to human GCRVs and < 79% to other porcine and bovine GCRVs. A unique 4-aa insertion (SSSV or SSTI), within a variable region at the carboxy-terminus of VP7, represented a distinctive feature for these 4 unique strains. An additional strain, 134/04-18, was clearly different from all human and animal GCRVs (< 85% aa identity) and likely accounts for a distinct VP7 genotype. The VP7 of a unique strain, 42/05-21, shared similar ranges of aa sequence identities with porcine and human strains (88.0–90.7% to porcine GCRVs and 85.2–88.2% to human GCRVs). Plotting the VP7 gene of strain 42/05-21 against the VP7 of human and porcine strains revealed discontinuous evolution rates throughout the VP7 molecule, suggesting different mutational pressure or a remote intragenic recombination event. These findings provide the need for future epidemiological surveys and warrant studies to investigate the pathogenic potential of these novel GCRVs in pigs.

Distribution of the clpX gene in Brachyspira species and reactivity of recombinant Brachyspira pilosicoli ClpX with sera from mice and humans

Previously, a clpX gene encoding a predicted 67 kDa membrane-associated ATPase subunit of the Clp protease (ClpX) was identified in a porcine strain (95/1,000) of the intestinal spirochaete Brachyspira pilosicoli. In the current study, the distribution of this large clpX gene was investigated in a collection of strains representing all seven Brachyspira spp. Using PCR with internal primers, an 878 bp portion of the gene was detected in 29 of 35 strains (83 %) of B. pilosicoli, 6 of 24 strains (25 %) of Brachyspira hyodysenteriae, 14 of 16 strains (88 %) of Brachyspira intermedia, 6 of 17 strains (35 %) of Brachyspira innocens, 1 of 6 strains (17 %) of Brachyspira murdochii, 1 of 2 strains (50 %) of Brachyspira aalborgi and not in the single strain of Brachyspira alvinipulli. The whole gene was sequenced from 20 Brachyspira spp. strains and compared with the clpX gene from B. pilosicoli 95/1,000 (GenBank accession no. AY466377). The genes had 99.3-99.7 % nucleotide sequence similarity and the predicted products had 99.7-100 % amino acid sequence similarity. The clpX gene from WesB, a human strain of B. pilosicoli, was cloned and expressed as a histidine-tagged fusion protein in Escherichia coli BL21. The purified protein was used to vaccinate mice and their sera were found to recognize the expected approximately 67 kDa protein in whole-cell preparations of WesB. Sera from mice vaccinated with formalin-treated whole-cell proteins of WesB reacted with the recombinant protein. These results indicate that ClpX is both conserved and immunogenic and hence might be useful as a subunit vaccine component for Brachyspira spp. infections. Sera from humans with no known exposure to B. pilosicoli reacted with the recombinant ClpX protein, indicating that it is unlikely to be useful as a reagent for serological detection of Brachyspira spp. infections.

Phylogenetic analysis of porcine rotavirus in Argentina: Increasing diversity of G4 strains and evidence of interspecies transmission

Group A rotaviruses are one of the most frequently detected viral agents associated with neonatal diarrhea in piglets. In order to characterize rotavirus (RV) strains circulating in Argentinean swine, four porcine production farms located in Buenos Aires were studied. RV strains genotyped as P[6]G4, P[6]G8 and P[1]G6 were found in piglets under 30 days of age, without diarrhea. Phylogenetic and sequence analysis of the VP7 gene from G4 strains available in databases, reveals five porcine new lineages (III–VII) and three sublineages (VIIa–VIIc). The G4 porcine Argentinean strains were grouped with a porcine RV strain isolated in Brazil and another RV strain isolated from a child with diarrhea in Mexico, constituting an American lineage (VII). On the other hand, porcine G6 and G8 were closely related to RV's circulating in Argentinean cattle and South-American camelids, respectively. The fact that G4 porcine lineages were epidemiologically related to human strains, and G6 and G8 Argentinean porcine strains were found related to bovine and South-American camelids, respectively, suggests that pigs might play a crucial role as reservoir and generator of newly adapted emerging RV strains for human and other species.

Prevalence and Mechanism of Resistance against Macrolides, Lincosamides, and Streptogramins amongEnterococcus faeciumIsolates from Food-Producing Animals and Hospital Patients in Belgium

The prevalence of acquired resistance to streptogramins, macrolides, and lincosamides and the genetic background of this resistance was investigated in Enterococcus faecium strains isolated from food-producing animals and hospital patients 4-5 years after the ban of streptogramins as growth promoters. The minimum inhibitory concentrations (MICs) of quinupristin/dalfopristin (Q/D), virginiamycin M1 (virgM1), erythromycin (ery), tylosin (tyl), and lincomycin (lin) were determined by the agar dilution method for E. faecium isolates derived from pigs (80), broilers (45), and hospitalized patients (103). Resistance or susceptibility was interpreted using a microbiological criterion and breakpoints recommended by the Clinical Laboratory Standards Institute (CLSI), if available. The isolates were also screened by PCR for erm(B), lnu(A), lnu(B), mef(A/E), vat(D), vat(E), vga(A), vga(B), and vgb(A) genes. Acquired resistance to Q/D, virgM1, ery, tyl, and lin was detected in 34%, 96%, 46%, 46%, and 69% of the porcine strains, respectively. For broiler strains this was 15% (Q/D), 98% (virgM1), 69% (ery), 71% (tyl), and 89% (lin) and for human strains 23% (Q/D), 65% (virgM1), 54% (ery), 52% (tyl), and 60% (lin). Strains showing cross-resistance against macrolides and lincosamides almost always carried the erm(B) gene. This gene was present in 64% of the Q/D-resistant isolates. Only in two human and three broiler Q/D- and virgM1-resistant isolates, a combination of the erm(B) and vat(D) or vat(E) genes was found. The genetic background of resistance could not be determined in the other Q/D- or virgM1-resistant strains. This study demonstrates that streptogramin resistance is frequently present in strains from hospitalized patients and food-producing animals, but the genetic basis hitherto mostly remains obscure.

Insight into Host Cell Carbohydrate-recognition by Human and Porcine Rotavirus from Crystal Structures of the Virion Spike Associated Carbohydrate-binding Domain (VP8*)

Rotavirus infection leads to the death of half a million children annually. The exact specifics of interaction between rotavirus particles and host cells enabling invasion and infection have remained elusive. Host cell oligosaccharides are critical components, and their involvement aids the virus in cell-recognition and attachment, as well as dictation of the remarkable host-specificity that rotaviruses demonstrate. Interaction between the rotavirus spike-protein carbohydrate-binding domain (VP8*) and cell surface oligosaccharides facilitate virus recognition of host cells and attachment. Rotaviruses are considered, controversially, to recognise vastly different carbohydrate structures and either with incorporation of terminal sialic acid or without, as assessed by their ability to infect cells that have been pre-treated with sialidases. Herein, the X-ray crystallographic structures of VP8* from the sialidase insensitive Wa and the sialidase sensitive CRW-8 rotavirus strains that cause debilitating gastroenteritis in human and pig are reported. Striking differences are apparent regarding recognition of the sialic acid derivative methyl α-d-N-acetylneuraminide, presenting the first experimental evidence of the inability of the human rotavirus strain to bind this monosaccharide, that correlates with Wa and CRW-8 recognising sialidase-resistant and sialidase-sensitive receptors, respectively. Identified are structural features that provide insight in attainment of substrate specificity exhibited by porcine strains as compared to rhesus rotavirus. Revealed in the CRW-8 VP8* structure is an additional bound ligand that intriguingly, is within a cleft located equivalent to the carbohydrate-binding region of galectins, and is suggestive of a new region for interaction with cell-surface carbohydrates. This novel result and detailed comparison of our representative sialidase-sensitive CRW-8 and insensitive Wa VP8* structures with those reported leads to our hypothesis that this groove is used for binding carbohydrates, and that for the human strains, as for other sialidase-insensitive strains could represent a major oligosaccharide-binding region.

Characterization of fimbriae extracts from porcine enterotoxigenic Escherichia coli strains carrying F6 (987P) antigen.

Fimbrial extracts from porcine enterotoxigenic Escherichia coli (ETEC) strains carrying F6 (987P) intestinal colonization factor antigen wereobtained using the thermal shock method. The extracts were analyzed by SDSPAGE and immunoblotting using different fimbriae-specific antisera. Two major protein bands with molecular masses of 17.5 and 21.9 kDa were detected. The 21.9-kDa band was identified as the major subunit of F6 fimbrial antigen in strains of serogroups O9 and O141. The 17.5-kDa band was associated with porcine strains of serogroups O9 and O20.

Prevalence of Streptococcus suis Genotypes in Wild Boars of Northwestern Germany

Invasive serotype 2 (cps2+) strains of Streptococcus suis cause meningitis in pigs and humans. Four case reports of S. suis meningitis in hunters suggest transmission of S. suis through the butchering of wild boars. Therefore, the objective of this study was to investigate the prevalence of potentially human-pathogenic S. suis strains in wild boars. S. suis was isolated from 92% of all tested tonsils (n=200) from wild boars. A total of 244 S. suis isolates were genotyped using PCR assays for the detection of serotype-specific genes, the hemolysin gene sly, and the virulence-associated genes mrp and epf. The prevalence of the cps2+ genotype among strains from wild boars was comparable to that of control strains from domestic pig carriers. Ninety-five percent of the cps2+ wild boar strains were positive for mrp, sly, and epf*, the large variant of epf. Interestingly, epf* was significantly more frequently detected in cps2+ strains from wild boars than in those from domestic pigs; epf* is also typically found in European S. suis isolates from humans, including a meningitis isolate from a German hunter. These results suggest that at least 10% of wild boars in Northwestern Germany carry S. suis strains that are potentially virulent in humans. Additional amplified fragment length polymorphism analysis supported this hypothesis, since homogeneous clustering of the epf* mrp+ sly+ cps2+ strains from wild boars with invasive human and porcine strains was observed.

Immunostimulatory properties of a novel adjuvant administered with inactivated influenza virus vaccine

The immunopotentiating activity of a new delivery system was investigated comparatively to Alhydrogel adjuvant, as an antiviral inactivated vaccine after one injection. The efficiency of the new formulation (BioMed) was evaluated with an inactivated porcine strain of influenza (A/Sw/IN/1726/88 H1N1) in the pig model. The first assessment criteria was the follow-up of selected immunological parameters such as, antibody levels, lymphoproliferation, double positive CD4+CD8+ T lymphocytes and cytokine production (IL-2, IL-4, IFN-gamma). The second criteria was the estimate of the protection level of animals exposed to a homologous challenge of 50 PID50 one month after a single immunizing or control injection. In the BioMed group of animals, 4 pigs (out of 6) were free of macroscopic lesion, while lesions could be seen in all individuals of other groups and virus was isolated in only one animal, whereas all other animals of other groups had virus in their lungs. This better protection of BioMed animals seems to be correlated mainly with higher levels of antibodies and to a lesser extent with a slightly better CMI response and probably with the production of memory CD4+CD8+ T cells.

Molecular characterization of novel G5 bovine rotavirus strains.

Group A rotaviruses are a major cause of acute gastroenteritis in young children as well as many domestic animals. The rotavirus genome is composed of 11 segments of double-stranded RNA and can undergo genetic reassortment during mixed infections, leading to progeny viruses with novel or atypical phenotypes. The aim of this study was to determine if the bovine group A rotavirus strains KJ44 and KJ75, isolated from clinically infected calves, share genetic features with viruses obtained from heterologous species. All 11 genes sequences of the KJ44 and KJ75 strains were sequenced and analyzed. The KJ44 VP4 had 91.7% to 96.3% deduced amino acid identity to the bovine related P[1] strain, whereas the KJ75 strain was most closely related to the bovine related P[5] strain (91.9% to 96.9% amino acid identity). Both KJ44 and KJ75 strains also contained the bovine related VP3 gene. The remaining 9 segments were closely related to porcine group A rotaviruses. The KJ44 and KJ75 strains showed high amino acid identity to the G5 rotaviruses, sharing 90.4% to 99.0% identity. In addition, these strains belonged to the NSP4 genotype B, which is typical of porcine rotaviruses and subgroup I, with the closest relationship to the porcine JL-94 strain. These results strongly suggest that bovine rotavirus strains with the G5 genotype occur in nature as a novel G genotype in cattle as a result of a natural reassortment between bovine and porcine strains.

Sporadic human Yersinia enterocolitica infections caused by bioserotype 4/O : 3 originate mainly from pigs

Yersinia enterocolitica 4/O : 3 is the most frequent cause of sporadic human yersiniosis in Finland and Germany. To investigate the possible link between pigs and humans, 282 human and 534 porcine strains from Finland and Germany were characterized with PFGE using NotI, ApaI and XhoI enzymes. Most of the human strains (>80 %) were indistinguishable from the porcine strains in both countries and most of the genotypes (178/182) were different in Finland and Germany. The indistinguishable genotypes among human and porcine strains together with different genotypes in Finland and Germany indicate that pigs are an important source of sporadic yersiniosis in both countries.

Characterization of VP1, VP2 and VP3 Gene Segments of A Human Rotavirus Closely Related to Porcine Strains

Long RNA electropherotype rotavirus strains with subgroup I specificity predominated the infantile gastroenteritis outbreak in Manipur, India, in 1987-88. One such strain (RMC321) was found to possess porcine characteristics in 7 out of 8 genes sequenced. Partial characterization of its remaining VP1, VP2 and VP3 genes along with a porcine rotavirus strain (HP140) uncovered their close genetic relation to porcine strains. VP7 was the only gene segment of this strain with significant genetic identity to human strains. This indicates that a rotavirus reassortant strain with most of its genetic material derived from a porcine strain may cause symptomatic infection in a human host.

Identification of a novel VP4 genotype carried by a serotype G5 porcine rotavirus strain

Rotavirus genome segment 4, encoding the spike outer capsid VP4 protein, of a porcine rotavirus (PoRV) strain, 134/04-15, identified in Italy was sequenced, and the predicted amino acid (aa) sequence was compared to those of all known VP4 (P) genotypes. The aa sequence of the full-length VP4 protein of the PoRV strain 134/04-15 showed aa identity values ranging from 59.7% (bovine strain KK3, P8[11]) to 86.09% (porcine strain A46, P[13]) with those of the remaining 25 P genotypes. Moreover, aa sequence analysis of the corresponding VP8* trypsin cleavage fragment revealed that the PoRV strain 134/04-15 shared low identity, ranging from 37.52% (bovine strain 993/83, P[17]) to 73.6% (porcine strain MDR-13, P[13]), with those of the remaining 25 P genotypes. Phylogenetic relationships showed that the VP4 of the PoRV strain 134/04-15 shares a common evolutionary origin with porcine P[13] and lapine P[22] rotavirus strains. Additional sequence analyses of the VP7, VP6, and NSP4 genes of the PoRV strain 134/04-15 revealed the highest VP7 aa identity (95.9%) to G5 porcine strains, a porcine-like VP6 within VP6 genogroup I, and a Wa-like (genotype B) NSP4, respectively. Altogether, these results indicate that the PoRV strain 134/04-15 should be considered as prototype of a new VP4 genotype, P[26], and provide further evidence for the vast genetic and antigenic diversity of group A rotaviruses.

Relationships among porcine and human P[6] rotaviruses: Evidence that the different human P[6] lineages have originated from multiple interspecies transmission events

Porcine rotavirus strains (PoRVs) bearing human-like VP4 P[6] gene alleles were identified. Genetic characterization with either PCR genotyping or sequence analysis allowed to determine the VP7 specificity of the PoRVs as G3, G4, G5 and G9, and the VP6 as genogroup I, that is predictive of a subgroup I specificity. Sequence analysis of the VP8* trypsin-cleavage product of VP4 allowed PoRVs to be characterized further into genetic lineages within the P[6] genotype. Unexpectedly, the strains displayed significantly higher similarity (up to 94.6% and 92.5% at aa and nt level, respectively) to human M37-like P[6] strains (lineage I), serologically classifiable as P2A, or to the atypical Hungarian P[6] human strains (HRVs), designated as lineage V (up to 97.0% aa and 96.1% nt), than to the porcine P[6] strain Gottfried, lineage II (<85.1% aa and 82.2 nt), which is serologically classified as P2B. Interestingly, no P[6] PoRV resembling the original prototype porcine strain, Gottfried, was detected, while Japanase P[6] PoRV clustered with the atypical Japanase G1 human strain AU19. By analysis of the 10th and 11th genome segments, all the strains revealed a NSP4B genogroup (Wa-like) and a NSP5/6 gene of porcine origin. These findings strongly suggest interspecies transmission of rotavirus strains and/or genes, and may indicate the occurrence of at least 3 separate rotavirus transmission events between pigs and humans, providing convincing evidence that evolution of human rotaviruses is tightly intermingled with the evolution of animal rotaviruses.

Comparison and Transferability of theerm(B) Genes between Human and Farm Animal Streptococci

To obtain better insights into the possible exchange of resistance genes between human and animal streptococci, the sequences of the erm (B) genes of streptococcal isolates from humans, pigs, pork carcasses, chickens, and calves were compared. Identical erm (B) gene sequences were present in strains from humans, pigs, pork carcasses, and calves. During in vitro mating experiments, the erm (B) gene was exchanged between porcine Streptococcus suis and human S. pneumoniae, S. pyogenes, and S. oralis strains. The presence of different tetracycline resistance genes and the int Tn 1545 gene was determined in animal streptococci carrying the erm (B) gene. Although tet(M) and int Tn 1545 genes were detected in 24% of the porcine and pork carcass streptococcal strains, the tet(O) gene was the predominant tetracycline resistance gene in these strains (81%). The latter gene was co-transferred with the erm (B) gene from porcine S. suis strains to human streptococci in the mating experiments. These results show that, identical erm (B) gene sequences were present in animal and human streptococci and that transfer of the erm (B) gene from porcine S. suis to human streptococci and vice versa is possible, but probably occurs at a low frequency.