One Health and antimicrobial resistance, a United States perspective.

Antimicrobial drugs are a precious resource, responsible for saving millions of lives since their discovery. Unfortunately, some antimicrobials are rapidly losing their effectiveness due to the development and spread of antimicrobial resistance (AMR), a multi-faceted and complex problem affecting humans, animals, plants and the environment. While AMR is a global problem, in this paper, the authors briefly highlight some ongoing efforts in the United States of America aimed at integrating a One Health approach into policies and programmes that address this important health threat.

Les antibiotiques sont des ressources de grande valeur qui ont sauvé des millions de vies depuis leur découverte. Malheureusement, certains agents antimicrobiens perdent rapidement leur efficacité en raison de l'apparition et propagation des résistances à ces agents, phénomène complexe et multidimensionnel qui affecte l'homme, les animaux, les plantes et l'environnement. La résistance aux agents antimicrobiens est un problème mondial ; dans cet article, les auteurs décrivent certaines initiatives actuellement mises en oeuvre aux États-Unis d'Amérique pour intégrer l'approche Une seule santé dans les politiques et les programmes conçus pour lutter contre cette menace sanitaire majeure.

Los fármacos antimicrobianos son un recurso valiosísimo, cuyo uso ha salvado millones de vidas desde que fueron descubiertos. Lamentablemente, algunos de ellos están perdiendo rápidamente eficacia debido a la aparición y propagación de resistencias, lo que plantea un problema tan complejo como poliédrico, que afecta a personas, animales, plantas y ecosistemas. Aunque la dimensión del problema es planetaria, los autores destacan aquí brevemente algunas de las iniciativas en curso en los Estados Unidos de América que tienen por objetivo integrar los planteamientos de Una sola salud en el conjunto de políticas y programas desde los cuales se aborda esta importante amenaza sanitaria.

Hemostasis biomarkers and incident cognitive impairment: the REGARDS study.

Essentials Cognitive disorders are increasing and vascular risk factors play a role in this. We performed a nested case control study of hemostasis biomarkers and cognitive impairment (CI). Higher baseline fibrinogen, factor VIII and D-dimer were related to incident CI over 3.5 years. Adjusted for other risk factors, 2+ abnormal markers (but not single ones) led to higher risk. SUMMARY: Background Vascular risk factors are associated with cognitive impairment, a condition that imposes a substantial public health burden. We hypothesized that hemostasis biomarkers related to vascular disease would be associated with the risk of incident cognitive impairment. Methods We performed a nested case-control study including 1082 participants with 3.5 years of follow-up in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a longitudinal cohort study of 30 239 black and white Americans aged ≥ 45 years. Participants were free of stroke or cognitive impairment at baseline. Baseline D-dimer, fibrinogen, factor VIII and protein C levels were measured in 495 cases who developed cognitive impairment during follow-up (based on abnormal scores on two or more of three cognitive tests) and 587 controls. Results Unadjusted odds ratios (ORs) for incident cognitive impairment were 1.32 (95% confidence interval [CI] 1.02-1.70) for D-dimer > 0.50 µg mL-1 , 1.83 (95% CI 1.24-2.71) for fibrinogen > 90th percentile, 1.63 (95% CI 1.11-2.38) for FVIII > 90th percentile, and 1.10 (95% CI 0.73-1.65) for protein C < 10th percentile. There were no differences in associations by race or region. Adjustment for demographic, vascular and health behavior risk factors attenuated these associations. However, having at least two elevated biomarkers was associated with incident cognitive impairment, with an adjusted OR of 1.73 (95% CI 1.10-2.69). Conclusion Elevated D-dimer, fibrinogen and FVIII levels were not associated with the occurrence of cognitive impairment after multivariable adjustment; however, having at least two abnormal biomarkers was associated with the occurrence of cognitive impairment, suggesting that the burden of these biomarkers is relevant.

Genome-wide meta-analyses of smoking behaviors in African Americans.

The identification and exploration of genetic loci that influence smoking behaviors have been conducted primarily in populations of the European ancestry. Here we report results of the first genome-wide association study meta-analysis of smoking behavior in African Americans in the Study of Tobacco in Minority Populations Genetics Consortium (n = 32,389). We identified one non-coding single-nucleotide polymorphism (SNP; rs2036527[A]) on chromosome 15q25.1 associated with smoking quantity (cigarettes per day), which exceeded genome-wide significance (ß = 0.040, s.e. = 0.007, P = 1.84 × 10(-8)). This variant is present in the 5'-distal enhancer region of the CHRNA5 gene and defines the primary index signal reported in studies of the European ancestry. No other SNP reached genome-wide significance for smoking initiation (SI, ever vs never smoking), age of SI, or smoking cessation (SC, former vs current smoking). Informative associations that approached genome-wide significance included three modestly correlated variants, at 15q25.1 within PSMA4, CHRNA5 and CHRNA3 for smoking quantity, which are associated with a second signal previously reported in studies in European ancestry populations, and a signal represented by three SNPs in the SPOCK2 gene on chr10q22.1. The association at 15q25.1 confirms this region as an important susceptibility locus for smoking quantity in men and women of African ancestry. Larger studies will be needed to validate the suggestive loci that did not reach genome-wide significance and further elucidate the contribution of genetic variation to disparities in cigarette consumption, SC and smoking-attributable disease between African Americans and European Americans.

The risk of Parkinson disease associated with urate in a community-based cohort of older adults.

BACKGROUND/AIMS: Studies suggest an inverse association between urate concentration and the risk of Parkinson disease (PD). We investigated this in the Cardiovascular Health Study in an elderly community-based cohort of adults. METHODS: The association of baseline urate (µmol/l) and incident PD over 14 years was assessed with locally weighted scatterplot smoothing (LOESS) regression from which categories of low (<300 µmol/l), middle (300-500 µmol/l), and high (>500 µmol/l) urate ranges were derived. Multivariate logistic regression models assessed the risk of PD for each urate range. Linear and quadratic terms were tested when modeling the association between urate and the risk of PD. RESULTS: Women had significantly lower urate concentrations than did men [316.8 µmol/l (SD 88.0) vs. 367.4 µmol/l (SD 87.7), p < 0.0001] and in women no associations between urate and PD risk were observed. In men, LOESS curves suggested a U-shaped or threshold effect between urate and PD risk. With the middle range as reference, the risk of developing PD was significantly increased for urate <300 µmol/l (OR 1.69, 95% CI 1.03-2.78) but not for urate >500 µmol/l (OR 1.55, 95% CI 0.72-3.32) in men. A negative linear term was significant for urate <500 µmol/l, and across the entire range a convex quadratic term was significant. CONCLUSIONS: Results suggest a more complex relationship than previously reported between urate levels and the risk of PD in men. Low urate concentrations were associated with a higher PD risk and high urate concentrations were not associated with a further decrease in PD risk.

Post hoc Parkinson's disease: identifying an uncommon disease in the Cardiovascular Health Study.

BACKGROUND: Although ongoing cohort studies offer a unique opportunity to apply existing information collected prospectively to further the scientific understanding of Parkinson's disease (PD), they typically have limited information for clinical diagnosis. METHODS: We used combinations of self-report, International Classification of Diseases - 9th edition codes and antiparkinsonian medications to identify PD in the Cardiovascular Health Study. To determine whether the expected inverse association between smoking and PD is evident using our outcome definitions, we assessed baseline smoking characteristics for various definitions of PD. RESULTS: We identified 60 cases with prevalent PD (1.0%; 95% confidence interval, CI = 0.8-1.3%) and 154 with incident PD by year 14. Clear associations were observed for current smokers (odds ratio, OR = 0.50; 95% CI = 0.26-0.95) and for those who smoked ≥50 pack-years (OR = 0.53; 95% CI = 0.29-0.96). Estimates for smoking were similar when ≥2 data sources were required. Estimates for self-report alone were attenuated towards null. CONCLUSIONS: Using multiple data sources to identify PD represents an alternative method of outcome identification in a cohort that would otherwise not be possible for PD research. Ongoing cohort studies can provide settings in which rapid replication and explorations of new hypotheses for PD are possible.

Efficacy of combined porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae vaccination in piglets.

Three vaccination challenge studies were performed to evaluate the impact on vaccine efficacy of combining porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae vaccines. Piglets were vaccinated with either a M hyopneumoniae bacterin, a modified live PRRSV vaccine based on a European-type PRRSV strain, or a combination of both vaccines, followed by experimental infection with either M hyopneumoniae or PRRSV. Vaccine efficacy was evaluated by assessing lung lesion scores for M hyopneumoniae and measuring viraemia for PRRSV. There were no significant differences between the protective efficacy of the combined vaccine protocol and the protective efficacy of the two single vaccines, indicating that PRRSV vaccination did not interfere with M hyopneumoniae vaccine efficacy and vice versa.

The antibody responses to swine influenza virus (SIV) recombinant matrix 1 (rM1), matrix 2 (M2), and hemagglutinin (HA) proteins in pigs with different SIV exposure.

The influenza invariant matrix 2 (M2) protein is a potential subunit vaccine candidate to induce protective immunity against broader strains of influenza A viruses (IAV). Antibodies to M2 protein have not been well characterized in IAV natural hosts. To characterize M2-specific antibodies in pigs, an ELISA to the extracellular region of the M2 (M2e) protein was developed. Sera from pigs experimentally infected with three different swine influenza virus (SIV) subtypes, immunized with an SIV inactivated vaccine, or positive for SIV maternally derived antibodies (MDA) in the absence of SIV infection were tested in assay. Confirmation of antibody titer status of pigs, was determined using a hemagglutination-inhibition (HI) test and the presence of antibodies to matrix 1 (M1) protein was measured by a recombinant M1 (rM1)-based ELISA. The antibody titers to the HA and M2e proteins but not to the rM1 were directly correlated to the dose of virus used to infect the pigs and the level of antibodies detected by the HI assay varied according to SIV subtype. Pigs experimentally infected with SIV produced low levels of M2e antibodies compared to antibodies detected by the HI and rM1 assays. Vaccination alone followed by infection did not increase the levels of M2e antibodies in contrast to HA and rM1 antibodies. Pigs with MDA had different levels of HA antibodies and were positive to M2e antibodies, but results were not correlated to HA antibodies levels and inconsistently present.

Temporal relationship between cigarette smoking and risk of Parkinson disease.

OBJECTIVE: To characterize further the relationship between smoking history and Parkinson disease (PD) risk by considering temporal and qualitative features of smoking exposure, including duration, average intensity, and recentness, as well as the relative importance of smoking during different periods of life. METHODS: We prospectively assessed incident PD from 1992 to 2001 among 79,977 women and 63,348 men participating in the Cancer Prevention Study II Nutrition Cohort, according to their cigarette smoking status and lifetime smoking histories. RESULTS: During follow-up, 413 participants had definite or probable PD confirmed by their treating neurologists or medical record review. Compared with never smokers, former smokers had a relative risk (RR) of 0.78 (95% CI 0.64 to 0.95) and current smokers had an RR of 0.27 (95% CI 0.13 to 0.56). On average, participants with more years smoked, more cigarettes per day, older age at quitting smoking, and fewer years since quitting smoking had lower PD risk. The relative risks and trends did not vary significantly by sex. The cumulative incidence of PD was lowest among participants who quit smoking at later ages. A 30% to 60% decreased risk of PD was apparent for smoking as early as 15 to 24 years before symptom onset, but not for smoking 25 or more years before onset. CONCLUSIONS: The lower risk of Parkinson disease among current and former smokers varied with smoking duration, intensity, and recentness. The dependence of this association on the timing of smoking during life is consistent with a biologic effect.

Plasmid-mediated growth hormone-releasing hormone efficacy in reducing disease associated with Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus infection.

The purpose of this study was to determine the effects of plasmid-mediated growth hormone releasing hormone (GHRH) supplementation on the clinical outcomes of pigs vaccinated against and challenged with either Mycoplasma hyopneumonia (M. hyo) and/or with porcine reproductive and respiratory syndrome (PRRS) virus. Before the first vaccination, pigs received a single i.m. injection of 0.625 mg of a porcine GHRH-expressing plasmid followed by electroporation of the injection site. Pigs were vaccinated at 2-wk intervals, challenged with either M. hyo and/or PRRS virus 2-wk after the second vaccination, and necropsied at 17 and 36 d after challenge. Clinical parameters associated with M. hyo challenge were improved with the GHRH treatment. Average daily gain between challenge and necropsy was improved (P = 0.04). Respiratory scores for M. hyo-challenged pigs tended to be lower in GHRH-treated animals compared to controls, and coughing scores were improved by the treatment (P = 0.01). Macroscopic lesions associated with M. hyo infection pneumonia were fewer in the group that received the GHRH-expressing plasmid. No differences between treatment groups in the macroscopic pneumonia associated with PRRS virus were observed. No differences in serum antibodies to M. hyo or PRRS virus were observed with GHRH treatment. Nevertheless, IgG in the bronchioalveolar lavage was increased by the GHRH treatment in M. hyo-challenged animals (P < 0.03). The results of this study suggest that GHRH supplementation before vaccination may enhance the protection against M. hyo-induced pneumonia and that a single dose of GHRH-expressing plasmid was sufficient to elicit an improved clinical outcome in this disease challenge model.

Effects of the timing of the administration of Mycoplasma hyopneumoniae bacterin on the development of lesions associated with porcine circovirus type 2.

To determine whether there is an effect of the timing of vaccination on porcine circovirus type 2 (PCV-2) replication and PCV-2-associated lesions, 78 pigs were randomly assigned to eight groups: group 1 (10 pigs) was vaccinated with a commercial Mycoplasma hyopneumoniae vaccine at two and four weeks of age, group 2 (nine pigs) was vaccinated at four and six weeks of age, group 3 (10 pigs) at six and eight weeks of age and group 4 (10 pigs) at eight and 10 weeks of age; group 5 (nine pigs) was vaccinated once with a double dose at four weeks of age, and group 6 (10 pigs) was vaccinated once with a double dose at eight weeks of age. Groups 7 and 8, both of 10 pigs, were not vaccinated. At eight weeks of age, the pigs in groups 1 to 7 were inoculated with PCV-2. Fourteen days after they had been inoculated, the pigs in groups 1, 4 and 5 had significantly (P<0.05) more copies of the PCV-2 genome in their serum than the unvaccinated pigs. Microscopically, 14 of the 68 inoculated pigs had normal lymphoid tissues, 40 had mild PCV-2-associated lymphoid lesions and 14 had moderate lesions. The mean overall lymphoid lesions (lymphoid depletion, granulomatous inflammation, and quantity of PCV-2 antigen in spleen, tonsil, and five lymph nodes) were significantly (P<0.05) more severe in groups 4 and 5 than in groups 2, 3, 7 and 8.

An investigation of susceptibility to porcine reproductive and respiratory syndrome virus between two genetically diverse commercial lines of pigs.

The objective of this study was to determine whether host genetics play a role in susceptibility to the respiratory disease in growing pigs caused by the porcine reproductive and respiratory syndrome virus (PRRSV). Based on a previous study, 2 genetically diverse commercial lines of pigs that also were divergent in the susceptibility of monocyte-derived macrophages to PRRSV infection in vitro were selected for an in vivo challenge study. Based on the average percentage of infected macrophages for each line, a line derived from the Large White breed was characterized as fluorescence-activated cell sorting(hi) (FACS(hi)), and a line derived from Duroc and Pietrain breeds was characterized as FACS(lo). Pigs from each line were challenged at 6 wk of age with PRRSV VR-2385 and necropsied at 10 or 21 d after infection. Data collected included clinical evaluation of disease, virus titration in serum and lung lavage fluid, macroscopic lung lesion scores, and microscopic lung lesion scores. The FACS(lo) line had consistently more severe clinical disease compared with the FACS(hi) line in the early stages of infection. Differences between line means were significant (P < 0.05) at 10 d after infection for all variables just described, and the FACS(lo) line showed more severe signs of disease. By 21 d after infection, clinical signs and lesions were resolving, and the differences between lines were significant (P < 0.04) only for microscopic lung lesion scores but approached significance (P < 0.08) for virus titer in serum. At 21 d after infection, the relationship between the lines reversed; the FACS(hi) line had higher serum virus titers than the FACS(lo) line. This report provides evidence that strongly suggests the existence of a host genetic component in disease susceptibility to PRRSV and indicates that further study is warranted to define the cellular mechanisms that affect disease susceptibility.

In vitro susceptibility of macrophages to porcine reproductive and respiratory syndrome virus varies between genetically diverse lines of pigs.

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be responsible for financial losses in the swine industry worldwide. It remains undetermined whether genetic variability of the host in susceptibility to PRRSV exists and if this variability can be exploited to help control this important disease. The objective of this study was to determine if an in vitro flow cytometry (FACS) assay that detects the percentage of monocyte-derived macrophages (MDM) infected with PRRSV could be utilized to demonstrate genetic variability in the susceptibility between distinct lines of pigs. Over 400 growing pigs from six genetic lines maintained in a single commercial breeding herd were screened using an in vitro FACS assay. From this initial screening, two genetically diverse lines of pigs that were also divergent in their FACS results were selected for further study. An additional 264 pigs from these two lines were subsequently tested for in vitro susceptibility to PRRSV. As in the preliminary screening, the Large White line had significantly higher average percent positive MDM over the Duroc-Pietrain synthetic line. This report suggests a genetic component for susceptibility to PRRSV exists and that the in vitro assay may be useful in predicting the relative susceptibility to PRRSV in large groups of animals.

Experimental reproduction of postweaning multisystemic wasting syndrome in pigs by dual infection with Mycoplasma hyopneumoniae and porcine circovirus type 2.

The objectives of this study were to investigate the interactions between Mycoplasma hyopneumoniae and porcine circovirus type 2 (PCV2) and to establish a model for studying the pathogenesis of and testing intervention strategies for the control of PCV2-associated porcine respiratory disease complex (PRDC). Sixty-seven pigs were randomly assigned to four groups. Group 1 (n=17) pigs served as controls, group 2 (n=17) pigs were inoculated with M. hyopneumoniae, group 3 (n=17) pigs were dual infected with M. hyopneumoniae and PCV2, and group 4 (n=16) pigs were inoculated with PCV2. Pigs were inoculated intratracheally with M. hyopneumoniae at 4 weeks of age followed by intranasal inoculation with PCV2 at 6 weeks of age. Dual-infected pigs had moderate dyspnea, lethargy, and reduced weight gain. The overall severity of macroscopic lung lesions, PCV2-associated microscopic lesions in lung and lymphoid tissues, and the amount of PCV2-antigen associated with these lesions were significantly (P <0.05) higher in dual-infected pigs compared with all other groups. Four of 17 (23.5%) dual-infected pigs had decreased growth rate and severe lymphoid depletion and granulomatous lymphadenitis associated with high amounts of PCV2-antigen consistent with postweaning multisystemic wasting syndrome (PMWS). PCV2-antigen in lung tissue was most often associated with M. hyopneumoniae-induced peribronchial lymphoid hyperplasia, suggesting that this is an important site for PCV2 replication in the lung. This study indicates that M. hyopneumoniae potentiates the severity of PCV2-associated lung and lymphoid lesions, increases the amount and prolongs the presence of PCV2-antigen, and increases the incidence of PMWS in pigs.

Effect of porcine parvovirus vaccination on the development of PMWS in segregated early weaned pigs coinfected with type 2 porcine circovirus and porcine parvovirus.

The objectives of this study were to determine if coinfection of segregated early weaned (SEW) pigs with porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV) induces an increase in the incidence of post-weaning multisystemic wasting syndrome (PMWS) compared to singular PCV2 infection, and to determine if vaccination against PPV protects pigs against PMWS associated with PCV2/PPV coinfection in SEW pigs. Seventy, 3-week-old, SEW pigs were randomly assigned to one of the five groups. Pigs in group 1 (n = 14) served as the negative controls, group 2 pigs (n = 14) were inoculated with PCV2, group 3 pigs (n = 12) were inoculated with PPV, groups 4 (n = 16) and 5 (n = 14) pigs were inoculated with both PCV2 and PPV. Pigs in groups 1-3 and 5 were vaccinated with two doses of a killed parvovirus-leptospira-erysipelothrix (PLE) vaccine prior to inoculation. The PCV2/PPV-coinfected pigs (groups 4 and 5) had significantly (P < 0.05) higher and more persistent fevers than the singular PCV2-infected pigs. One pig in each of the coinfected groups developed clinical disease (fever, respiratory disease, jaundice, weight loss) consistent with PMWS. Lymphoid depletion was significantly (P < 0.05) more severe in the dually-infected pigs at 42 days post-inoculation (DPI). Vaccinated, coinfected pigs (group 5) remained viremic significantly (P < 0.05) longer and had higher copy numbers of genomic PCV2 DNA in sera at 28, 35, and 42 DPI compared to the unvaccinated coinfected pigs (group 4). PPV-viremia was detected only in the unvaccinated group 4 pigs. PLE-vaccination prevented PPV-viremia but did not prevent clinical PMWS or reduce the severity of lymphoid depletion in PCV2/PPV-coinfected pigs. Evidence of increased incidence of clinical PMWS due to vaccination was not observed in this model.

Effect of vaccination with selective bacterins on conventional pigs infected with type 2 porcine circovirus.

The objective of this study was to determine whether vaccination with bacterins commonly used in the USA, when administered at a time typical of US protocol, enhances porcine circovirus type 2 (PCV2) replication and the incidence and severity of clinical signs and lesions characteristic of postweaning multisystemic wasting syndrome (PMWS) in conventional pigs. Sixty-one pigs free of PCV2 were randomly assigned to four groups. Groups 1 (n = 15) and 2 (n = 15) pigs served as sham-inoculated negative controls. Groups 3 (n = 14) and 4 (n = 17) pigs were inoculated intralymphoid with PCV2 field isolate ISU-40895. Pigs in groups 2 and 4 were vaccinated with Actinobacillus pleuropneumoniae (APP) and Mycoplasma hyopneumoniae (M. hyopneumoniae) bacterins 21 days before and again 1 day before inoculation with PCV2. Mild transient respiratory disease and diarrhea were observed from 13 to 34 days postinoculation (DPI) in pigs in groups 3 and 4. Half the pigs from each group were necropsied at 22 and 34 DPI, respectively. Moderately enlarged, tan-colored lymph nodes were observed in the majority of pigs in groups 3 and 4. There was a significantly (P < 0.05) longer length of viremia (2.14 +/- 0.26 versus 4.44 +/- 0.23 weeks), a higher copy number of the PCV2 genome in serum, a wider range of tissue distribution of PCV2 antigen, and an increased severity of lymphoid depletion in pigs vaccinated with commercial APP and M. hyopneumoniae vaccines and inoculated with PCV2 compared with PCV2-inoculated unvaccinated pigs. Swine producers and veterinarians may need to consider changes in vaccination protocols in herds with recurrent PCV2-associated PMWS.

Immunology of the porcine respiratory disease complex.

PRDC is a multifactorial respiratory syndrome that includes several respiratory pathogens. As can be observed in this article, although the pathogenesis of some of the respiratory pathogens of pigs is fairly well defined, the host response and the immune response necessary to control the pathogen often remain unclear. As our ability to evaluate the porcine immune system and its ability to respond to disease improves, the knowledge of how each of these respiratory pathogens alter and evade the immune system will increase. The pathogens most commonly isolated from pigs with clinical signs of PRDC either infect the cells of the immune system or induce significant immunopathology. Thus, PRRSV and M. hyopneumoniae, the two most common pathogens associated with PRDC, alter the ability of the respiratory immune system to respond to their presence and the presence of other pathogens. By changing the respiratory immune system, these two common pathogens increase the susceptibility to the many other pathogens associated with PRDC. As we learn more about the pathogens of the respiratory system, their interactions with each other, and the mechanisms by which they modulate the immune system, our ability to develop effective control measures will improve.

Interaction between Mycoplasma hyopneumoniae and swine influenza virus.

An experimental respiratory model was used to investigate the interaction between Mycoplasma hyopneumoniae and swine influenza virus (SIV) in the induction of pneumonia in susceptible swine. Previous studies demonstrated that M. hyopneumoniae, which produces a chronic bronchopneumonia in swine, potentiates a viral pneumonia induced by the porcine reproductive and respiratory syndrome virus (PRRSV). In this study, pigs were inoculated with M. hyopneumoniae 21 days prior to inoculation with SIV. Clinical disease as characterized by the severity of cough and fever was evaluated daily. Percentages of lung tissue with visual lesions and microscopic lesions were assessed upon necropsy at 3, 7, 14, and 21 days following SIV inoculation. Clinical observations revealed that pigs infected with both SIV and M. hyopneumoniae coughed significantly more than pigs inoculated with a single agent. Macroscopic pneumonia on necropsy at days 3 and 7 was greatest in both SIV-infected groups, with minimal levels of pneumonia in the M. hyopneumoniae-only-infected pigs. At 14 days post-SIV inoculation, pneumonia was significantly more severe in pigs infected with both pathogens. However, by 21 days postinoculation, the level of pneumonia in the dual-infected pigs was similar to that of the M. hyopneumoniae-only-infected group, and the pneumonia in the pigs inoculated with only SIV was nearly resolved. Microscopically, there was no apparent increase in the severity of pneumonia in pigs infected with both agents compared to that of single-agent-challenged pigs. The results of this study found that while pigs infected with both agents exhibited more severe clinical disease, the relationship between the two pathogens lacked the profound potentiation found with dual infection with M. hyopneumoniae and PRRSV. These findings demonstrate that the relationship between mycoplasmas and viruses varies with the individual agent.

Differential production of proinflammatory cytokines: in vitro PRRSV and Mycoplasma hyopneumoniae co-infection model.

An in vitro culture system was developed to investigate the induction of proinflammatory cytokines by Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus (PRRSV). M. hyopneumoniae infected porcine tracheal ring explants were co-cultured with PRRSV infected pulmonary alveolar macrophages (PAMs) for 24h to assess the cytokine production of each pathogen alone and the interaction between the two pathogens in vitro. Semiquantitative RT-PCR was used to measure interleukin (IL) 1alpha, IL1beta, IL6, IL8, IL10, IL12 and tumor necrosis factor (TNF) alpha mRNA in PAMs. Commercial ELISAs were used to measure soluble IL1beta, IL8, IL10 and TNF in the culture supernatant. In the dual infected group, mRNA expression of IL1alpha, IL1beta, IL8 and TNF was increased. Both the M. hyopneumoniae- and PRRSV-infected only groups tended to have increased expression of IL1alpha, IL1beta and IL8 mRNA, although no statistical difference was observed. Increased levels of IL1beta, IL8 and IL10 were present in the supernatant of the dual infected group as measured by ELISA. No increase in soluble TNF was observed in any of the groups. IL8 levels appeared high in all groups independent of infection status. The cause of the elevated IL8 was unknown, however, it may have been a non-specific response by the cells to tissue damage during the harvesting of the tracheal rings. Correlation between mRNA expression and the soluble cytokine levels were similar in the dual infected groups with the exception of IL10 and TNF. Levels of mRNA and soluble protein levels in the single pathogen infected groups were not as consistent. The increased production of proinflammatory cytokines IL1alpha, IL1beta, IL8 and TNF in the group infected with both M. hyopneumoniae and PRRSV suggests that cytokine induced inflammation may play an important role in the severe, chronic pneumonia induced by the concurrent infection of the two pathogens.

Evaluation of the ability of tilmicosin to prevent adherence of Mycoplasma hyopneumoniae to cilia using a differentiated swine respiratory epithelial culture system.

Mycoplasmal pneumonia caused by Mycoplasma hyopneumoniae is a serious economic problem for swine producers in the United States. Mycoplasma hyopneumoniae colonizes ciliated respiratory epithelial cells. The organism has been shown to be sensitive to tilmicosin, a synthetic macrolide, in antibiotic sensitivity assays. The efficacy of tilmicosin to inhibit adherence of M. hyopneumoniae to ciliated epithelial cells without direct contact between the antibiotic and the organism was evaluated using in vitro methods. The study demonstrated that tilmicosin inhibited the adherence of M. hyopneumoniae at the highest level tested in the system (2 microg/ml) suggesting that tilmicosin may be efficacious against mycoplasmal pneumonia.

Evaluation of local and systemic immune responses induced by intramuscular injection of a Mycoplasma hyopneumoniae bacterin to pigs.

OBJECTIVE: To evaluate immune responses induced by administration of Mycoplasma hyopneumoniae bacterin to pigs. Animals-60 healthy 7- to 10-day-old cross-bred boars. PROCEDURE: Pigs were assigned to 1 of 4 pig groups (15 pigs/group): vaccinated, challenged; vaccinated, nonchallenged; nonvaccinated, challenged; nonvaccinated, nonchallenged. Vaccinated pigs received IM injections of a mycoplasma bacterin on days 0 and 14, whereas nonvaccinated pigs received saline (0.9% NaCl) solution. Pigs in the challenged groups were inoculated intratracheally with M hyopneumoniae on day 42. Pigs were euthanatized and necropsied 41, 44, 48, and 70 days after the first vaccination, and proportion of lung surface with pneumonic lesions was determined. Percentage of lymphocyte subpopulations and number of interferon-gamma (IFN-gamma) secreting lymphocytes in blood and tissues, cytokine and antibody concentrations in bronchoalveolar lavage (BAL) fluid, and serum antibody concentrations were determined. RESULTS: Vaccination against and infection with M hyopneumoniae induced a local mucosal immune response in the respiratory tract of pigs. Proportion of lung surface with pneumonic lesions in vaccinated challenged pigs was reduced on day 70, compared with nonvaccinated challenged pigs. Vaccination stimulated the production of M hyopneumoniae-specific IFN-gamma secreting blood lymphocytes. Tumor necrosis factor-alpha concentration in BAL fluid on day 70 was increased in nonvaccinated challenged pigs, compared with vaccinated challenged pigs. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination against M hyopneumoniae induced local, mucosal, humoral, and cellular immune responses. Moreover, vaccination reduced the severity of lung lesions in challenged pigs, suggesting that mucosal antibodies, mediation of the inflammatory response, and cell-mediated immune responses are important for control of mycoplasmal pneumonia in pigs.