Impact of antiretroviral therapy during acute or early HIV infection on virologic and immunologic outcomes: results from a multinational clinical trial.

OBJECTIVE: To assess how antiretroviral therapy (ART) initiation during acute or early HIV infection (AEHI) affects the viral reservoir and host immune responses. DESIGN: Single-arm trial of ART initiation during AEHI at 30 sites in the Americas, Africa, and Asia. METHODS: HIV DNA was measured at week 48 of ART in 5 million CD4+ T cells by sensitive qPCR assays targeting HIV gag and pol. Peripheral blood mononuclear cells were stimulated with potential HIV T cell epitope peptide pools consisting of env, gag, nef, and pol peptides and stained for expression of CD3, CD4, CD8, and intracellular cytokines/chemokines. RESULTS: From 2017 to 2019, 188 participants initiated ART during Fiebig stages I (n = 6), II (n = 43), III (n = 56), IV (n = 23), and V (n = 60). Median age was 27 years (interquartile range 23-38), 27 (14%) participants were female, and 180 (97%) cisgender. Among 154 virally suppressed participants at week 48, 100% had detectable HIV gag or pol DNA. Participants treated during Fiebig I had the lowest HIV DNA levels (P < 0.001). Week 48 HIV DNA mostly did not correlate with concurrent CD4+ or CD8+ T cell HIV-specific immune responses (rho range -0.11 to +0.19, all P > 0.025). At week 48, the magnitude, but not polyfunctionality, of HIV-specific T cell responses was moderately reduced among participants who initiated ART earliest. CONCLUSION: Earlier ART initiation during AEHI reduced but did not eliminate the persistence of HIV-infected cells in blood. These findings explain the rapid viral rebound observed after ART cessation in early-treated individuals with undetectable HIV DNA by less sensitive methods.

Predictors of HIV rebound differ by timing of antiretroviral therapy initiation.

BACKGROUNDIdentifying factors that predict the timing of HIV rebound after treatment interruption will be crucial for designing and evaluating interventions for HIV remission.METHODSWe performed a broad evaluation of viral and immune factors that predict viral rebound (AIDS Clinical Trials Group A5345). Participants initiated antiretroviral therapy (ART) during chronic (N = 33) or early (N = 12) HIV infection with ≥ 2 years of suppressive ART and restarted ART if they had 2 viral loads ≥ 1,000 copies/mL after treatment interruption.RESULTSCompared with chronic-treated participants, early-treated individuals had smaller and fewer transcriptionally active HIV reservoirs. A higher percentage of HIV Gag-specific CD8+ T cell cytotoxic response was associated with lower intact proviral DNA. Predictors of HIV rebound timing differed between early- versus chronic-treated participants, as the strongest reservoir predictor of time to HIV rebound was level of residual viremia in early-treated participants and intact DNA level in chronic-treated individuals. We also identified distinct sets of pre-treatment interruption viral, immune, and inflammatory markers that differentiated participants who had rapid versus slow rebound.CONCLUSIONThe results provide an in-depth overview of the complex interplay of viral, immunologic, and inflammatory predictors of viral rebound and demonstrate that the timing of ART initiation modifies the features of rapid and slow viral rebound.TRIAL REGISTRATIONClinicalTrials.gov NCT03001128FUNDINGNIH National Institute of Allergy and Infectious Diseases, Merck.

A partner protection package for HIV cure-related trials involving analytical treatment interruptions.

Analytical treatment interruptions (ATIs) have become a key methodological approach to evaluate the effects of experimental HIV cure-related research interventions. During ATIs, sex partners of trial participants might be at risk of acquiring HIV. This risk raises both ethical and feasibility concerns about ATI trials. We propose a partner protection package (P3) approach to address these concerns. A P3 approach would provide guidance to investigators, sponsors, and those who are designing and implementing context-specific partner protections in HIV cure-related trials involving ATIs. The approach would also help assure institutional review boards, trial participants, and communities that ATI trials with a P3 would provide appropriate partner protections. We offer a prototype P3 framework that delineates three basic considerations for protecting participants' sex partners during ATI trials: (1) ensuring the scientific and social value of the ATI and the trial, (2) reducing the likelihood of unintended HIV transmission, and (3) ensuring prompt management of any acquired HIV infection. We outline possible ways of implementing these basic considerations.

Participant Perspectives and Experiences Following an Intensively Monitored Antiretroviral Pause in the United States: Results from the AIDS Clinical Trials Group A5345 Biomarker Study.

The AIDS Clinical Trials Group A5345 study (NCT03001128) included an intensively monitored antiretroviral pause (IMAP), during which participants living with HIV temporarily stopped antiretroviral treatment (ART) in an effort to identify biomarkers that could predict HIV rebound. We evaluated the potential impact of the IMAP on A5345 study participants in the United States by questioning them immediately after the IMAP and at the end of the study. We administered longitudinal sociobehavioral questionnaires to participants following the IMAP when they resumed ART and at the end of the study. We summarized descriptive data from the post-IMAP and end-of-study questionnaires. Open-ended responses were analyzed using conventional content analysis. Reactions to pausing ART involved a mixture of curiosity and satisfaction from contributing to science. All participants indicated adherence with the ART interruption. About half (9/17) of post-IMAP questionnaire respondents reported having sexual partner(s) during the IMAP, and of those, nearly all (8/9) did not find it difficult to use measures to prevent HIV transmission to partners. The majority believed that they benefited from the study, yet some had elevated anxiety following the IMAP and at the end of the study. Most (24/29) respondents who completed the end-of-study questionnaire would recommend the study to other people living with HIV. Our findings underscore the relevance of the psychosocial aspects of participating in studies that involve interruptions of ART. Understanding how participants experience this research is invaluable for informing the design of future research aimed at sustained ART-free virologic suppression.

Time to Viral Rebound After Interruption of Modern Antiretroviral Therapies.

BACKGROUND: Development of human immunodeficiency virus (HIV) remission strategies requires precise information on time to HIV rebound after treatment interruption, but there is uncertainty regarding whether modern antiretroviral therapy (ART) regimens and timing of ART initiation may affect this outcome. METHODS: AIDS Clinical Trials Group (ACTG) A5345 enrolled individuals who initiated ART during chronic or early HIV infection and on suppressive ART for ≥2 years. Participants underwent carefully monitored antiretroviral interruption. ART was restarted upon 2 successive viral loads ≥1000 copies/mL. We compared participants of A5345 with participants of 6 historic ACTG treatment interruption studies. RESULTS: Thirty-three chronic-treated and 12 early-treated participants interrupted ART with evaluable time to viral rebound. Median time to viral rebound ≥1000 HIV RNA copies/mL was 22 days. Acute retroviral rebound syndrome was diagnosed in 9% of the chronic-treated and none of the early-treated individuals. All participants of the historic studies were on older protease inhibitor-based regimens, whereas 97% of A5345 participants were on integrase inhibitor-based ART. There were no differences in the timing of viral rebound comparing A5345 versus historic studies. In a combined analysis, a higher percentage of early-treated participants remained off ART at posttreatment interruption week 12 (chronic vs early: 2% vs 9%, P = .0496). One chronic-treated and one early-treated A5345 participant remained off ART for >24 weeks. All participants resuppressed after ART reinitiation. CONCLUSIONS: Early ART initiation, using either older or newer ART regimens, was associated with a significant delay in the time to HIV rebound after ART interruption, lowering the barrier for HIV remission.

Anti-HIV antibody development up to 1 year after antiretroviral therapy initiation in acute HIV infection.

Early initiation of antiretroviral therapy (ART) in acute HIV infection (AHI) is effective at limiting seeding of the HIV viral reservoir, but little is known about how the resultant decreased antigen load affects long-term Ab development after ART. We report here that Env-specific plasma antibody (Ab) levels and Ab-dependent cellular cytotoxicity (ADCC) increased during the first 24 weeks of ART and correlated with Ab levels persisting after 48 weeks of ART. Participants treated in AHI stage 1 had lower Env-specific Ab levels and ADCC activity on ART than did those treated later. Importantly, participants who initiated ART after peak viremia in AHI developed elevated cross-clade ADCC responses that were detectable 1 year after ART initiation, even though clinically undetectable viremia was reached by 24 weeks. These data suggest that there is more germinal center (GC) activity in the later stages of AHI and that Ab development continues in the absence of detectable viremia during the first year of suppressive ART. The development of therapeutic interventions that can enhance earlier development of GCs in AHI and Abs after ART initiation could provide important protection against the viral reservoir that is seeded in individuals treated early in the disease.

Characterization of genetic diversity and population structure within Staphylococcus chromogenes by multilocus sequence typing.

Staphylococcus chromogenes is a common skin commensal in cattle and has been identified as a frequent cause of bovine mastitis and intramammary infections. We have developed a seven locus Multilocus Sequence Typing (MLST) scheme for typing S. chromogenes. Sequence-based typing systems, such as MLST, have application in studies of genetic diversity, population structure, and epidemiology, including studies of strain variation as a factor in pathogenicity or host adaptation. The S. chromogenes scheme was tested on 120 isolates collected from three geographic locations, Vermont and Washington State in the United States and Belgium. A total of 46 sequence types (STs) were identified with most of the STs being location specific. The utility of the typing scheme is indicated by a discrimination power of 95.6% for all isolates and greater than 90% for isolates from each of the three locations. Phylogenetic analysis placed 39 of the 46 STs into single core group consistent with a common genetic lineage; the STs in this group differ by less than 0.5% at the nucleotide sequence level. Most of the diversification in this lineage group can be attributed to mutation; recombination plays a limited role. This lineage group includes two clusters of single nucleotide variants in starburst configurations indicative of recent clonal expansion; nearly 50% of the isolates sampled in this study are in these two clusters. The remaining seven STs were set apart from the core group by having alleles with highly variable sequences at one or more loci. Recombination had a higher impact than mutation in the diversification of these outlier STs. Alleles with hypervariable sequences were detected at five of the seven loci used in the MLST scheme; the average sequence distances between the hypervariable alleles and the common core alleles ranged from 12 to 34 nucleotides. The extent of these sequence differences suggests the hypervariable alleles may be remnants of an ancestral genotype.

Participant Perspectives and Experiences Entering an Intensively Monitored Antiretroviral Pause: Results from the AIDS Clinical Trials Group A5345 Biomarker Study.

The AIDS Clinical Trials Group (ACTG) A5345 study included an intensively monitored antiretroviral pause (IMAP), during which a cohort of participants temporarily stopped antiretroviral treatment during chronic HIV infection. We surveyed participant perceptions and understanding of A5345 using a cross-sectional sociobehavioral questionnaire. Participants completed the baseline questionnaire either before or after initiating the study's IMAP. Questionnaire responses were linked to existing demographic data. Quantitative responses were analyzed overall and stratified by IMAP status. Open-ended responses were analyzed using conventional content analysis. Thirty-two participants completed the baseline sociobehavioral questionnaire. Half (n = 16) completed it before (i.e., pre-IMAP initiation group) and half (n = 16) after IMAP initiation (i.e., post-IMAP initiation group). Eight pre-IMAP initiation respondents (50%) and 11 post-IMAP respondents (69%) responded "yes" when asked if they perceived any direct benefits from participating in A5345. Perceived societal-level benefits included furthering HIV cure-related research and helping the HIV community. Perceived personal-level benefits included the opportunity to learn about the body's response to IMAP and financial compensation. The majority of respondents-13 from each group (81% of each)-reported risks from participation, for example, viral load becoming detectable. A5345 participants perceived both societal- and personal-level benefits of study participation. While the majority of survey respondents perceived participatory risks, nearly one in five did not. Key messages pertaining to study-related risks and benefits may need to be clarified or reiterated periodically throughout follow-up in HIV cure-related studies with IMAPs. Clinical Trail Registration Number: NCT03001128.

Novel Criteria for Diagnosing Acute and Early Human Immunodeficiency Virus Infection in a Multinational Study of Early Antiretroviral Therapy Initiation.

BACKGROUND: Antiretroviral therapy (ART) initiation during acute and early human immunodeficiency virus infection (AEHI) limits HIV reservoir formation and may facilitate post-ART control but is logistically challenging. We evaluated the performance of AEHI diagnostic criteria from a prospective study of early ART initiation. METHODS: AIDS Clinical Trials Group A 5354 enrolled adults at 30 sites in the Americas, Africa, and Asia who met any 1 of 6 criteria based on combinations of results of HIV RNA, HIV antibody, Western blot or Geenius assay, and/or the signal-to-cutoff (S/CO) ratio of the ARCHITECT HIV Ag/Ab Combo or GS HIV Combo Ag/Ab EIA. HIV status and Fiebig stage were confirmed by centralized testing. RESULTS: From 2017 through 2019, 195 participants were enrolled with median age of 27 years (interquartile range, 23-39). Thirty (15.4%) were female. ART was started by 171 (87.7%) on the day of enrollment and 24 (12.3%) the next day. AEHI was confirmed in 188 (96.4%) participants after centralized testing, 4 (2.0%) participants were found to have chronic infection, and 3 (1.5%) found not to have HIV discontinued ART and were withdrawn. Retrospectively, a nonreactive or indeterminate HIV antibody on the Geenius assay combined with ARCHITECT S/CO ≥10 correctly identified 99 of 122 (81.2%) Fiebig II-IV AEHI cases with no false-positive results. CONCLUSIONS: Novel AEHI criteria that incorporate ARCHITECT S/CO facilitated rapid and efficient ART initiation without waiting for an HIV RNA result. These criteria may facilitate AEHI diagnosis, staging, and immediate ART initiation in future research studies and clinical practice. CLINICAL TRIALS REGISTRATION: NCT02859558.

Recommendations for measuring HIV reservoir size in cure-directed clinical trials.

Therapeutic strategies are being clinically tested either to eradicate latent HIV reservoirs or to achieve virologic control in the absence of antiretroviral therapy. Attaining this goal will require a consensus on how best to measure the numbers of persistently infected cells with the potential to cause viral rebound after antiretroviral-therapy cessation in assessing the results of cure-directed strategies in vivo. Current measurements assess various aspects of the HIV provirus and its functionality and produce divergent results. Here, we provide recommendations from the BEAT-HIV Martin Delaney Collaboratory on which viral measurements should be prioritized in HIV-cure-directed clinical trials.

Plasmacytoid dendritic cells sense HIV replication before detectable viremia following treatment interruption.

Plasmacytoid dendritic cells (pDCs) are robust producers of IFNα and one of the first immune cells to respond to SIV infection. To elucidate responses to early HIV-1 replication, we studied blood pDCs in 29 HIV-infected participants who initiated antiretroviral therapy during acute infection and underwent analytic treatment interruption (ATI). We observed an increased frequency of partially activated pDCs in the blood before detection of HIV RNA. Concurrent with peak pDC frequency, we detected a transient decline in the ability of pDCs to produce IFNα in vitro, which correlated with decreased phosphorylation of IFN regulatory factory 7 (IRF7) and NF-κB. The levels of phosphorylated IRF7 and NF-κB inversely correlated with plasma IFNα2 levels, implying that pDCs were refractory to in vitro stimulation after IFNα production in vivo. After ATI, decreased expression of IFN genes in pDCs inversely correlated with the time to viral detection, suggesting that pDC IFN loss is part of an effective early immune response. These data from a limited cohort provide a critical first step in understanding the earliest immune response to HIV-1 and suggest that changes in blood pDC frequency and function can be used as an indicator of viral replication before detectable plasma viremia.

Rapid HIV RNA rebound after antiretroviral treatment interruption in persons durably suppressed in Fiebig I acute HIV infection.

Antiretroviral therapy during the earliest stage of acute HIV infection (Fiebig I) might minimize establishment of a latent HIV reservoir and thereby facilitate viremic control after analytical treatment interruption. We show that 8 participants, who initiated treatment during Fiebig I and were treated for a median of 2.8 years, all experienced rapid viral load rebound following analytical treatment interruption, indicating that additional strategies are required to control or eradicate HIV.

Interactive effects of dexamethasone and opsonized Mycoplasma bovis on bovine neutrophil function in vitro.

Previously we had reported that exposure to high levels of glucocorticoids, and to unopsonized Mycoplasma bovis, has a negative interactive effect on bovine neutrophil function in vitro, and this interactive effect was a function of M. bovis strain differences. Here we hypothesized that in vitro treatment of bovine neutrophils by glucocorticoid would impair phagocytosis of opsonized M. bovis compared to non-treated neutrophils and such impairment would be a function of M. bovis strain differences. Neutrophils isolated from 20 mid-lactation cows were treated with immunosuppressive dose of 5 × 10-4 M dexamethasone or placebo and incubated with one of four opsonized M. bovis strains that had been isolated from bovine origin. After incubation neutrophil function measured included: percentage reduction in log10 of M. bovis CFU/ml, percentage of phagocytizing neutrophils, phagocytized M. bovis per neutrophil, and killed M. bovis per neutrophil. Least square means of all neutrophil groups were contrasted using linear mixed-effects models. Effects due to strain, treatment, and their interaction on neutrophil function measured by the number of phagocytized M. bovis per neutrophil and number of killed M. bovis per neutrophil were different (P < 0.05). However, no significant strain by treatment interaction effect on percentage reduction in log10 of M. bovis CFU/ml was found. Neither a strain nor a strain by treatment interaction was found to affect the percentage phagocytizing neutrophils. These findings might explain in part the association of stressful events with subsequent outbreaks of Mycoplasma bovis associated bovine diseases.

Comparison of Virulence Gene Identification, Ribosomal Spacer PCR, and Pulsed-Field Gel Electrophoresis for Typing of Staphylococcus aureus Strains Isolated from Cases of Subclinical Bovine Mastitis in the United States.

Staphylococcus aureus is one of the most important pathogens causing contagious mastitis in dairy cattle worldwide. The objectives of this study were to determine if recently described S. aureus genotype B was present among previously characterized isolates from cases of bovine intramammary infection in the United States and to compare pulsed-field gel electrophoresis (PFGE) to the combination of ribosomal spacer PCR (RS-PCR) and virulence gene identification for typing of S. aureus strains. The hypothesis was that isolates that were previously characterized as contagious would be identified as genotype B and that the results of the two strain-typing methods would be comparable. Isolates were selected from a collection of S. aureus isolates from eight dairy farms. Mammary quarter milk somatic cell count (SCC) and N-acetyl-ß-d-gluconaminidase (NAGase) activity data were known and used to evaluate strain pathogenicity. RS-PCR was performed with conventional gel electrophoresis, and PCR was used for toxin gene identification. RS-PCR patterns were associated with a specific virulence gene pattern, as previously reported. Five RS-PCR banding patterns were identified. None of the isolates were characterized as genotype B. No association between RS-PCR types and milk SCC was found; however, NAGase activity was significantly higher in milk from mammary glands infected with RS-PCR banding type 1 (RSP type 1) than in milk from those infected with RSP type 2. The discriminatory power values were 1.0 and 0.46 for PFGE and RS-PCR, respectively. These data suggest that genotype B may have a limited geographic distribution and that PFGE is more discriminatory than RS-PCR performed with conventional gel electrophoresis for typing of S. aureus isolates of bovine origin.

Virologic and immunologic effects of adding maraviroc to suppressive antiretroviral therapy in individuals with suboptimal CD4+ T-cell recovery.

BACKGROUND: Combination antiretroviral therapy (ART) suppresses HIV-1 replication, but does not restore CD4 T-cell counts in all individuals. To investigate the effects of maraviroc on HIV-1 persistence and the relations between virologic and immunologic parameters in individuals with incomplete CD4 T-cell recovery, we performed a prospective, open-label pilot trial in which maraviroc was added to a suppressive ART regimen for 24 weeks. DESIGN: A5256 was a single-arm trial in which individuals on suppressive ART with incomplete CD4 T-cell recovery added maraviroc for 24 weeks. METHODS: We quantified low-level, residual viremia in plasma and total HIV-1 DNA and 2-long terminal repeat (2-LTR) circles in peripheral blood mononuclear cells before and after maraviroc intensification. We also evaluated markers of CD4 and CD8 T-cell immune activation (%CD38HLA-DR) and apoptosis (%caspase3/Bcl-2). RESULTS: No effect of maraviroc was found on the probability of detectable plasma viremia (≥1 copy/ml; n = 31, exact McNemar P = 1.0) or detectable 2-LTR circles (n = 28, P = 0.25) or on total HIV-1 DNA (n = 28, 90% confidence interval -0.1, +0.3 log10 copies/10 CD4 T-cells). Premaraviroc HIV-1 DNA levels were inversely related to premaraviroc %CD38HLA-DR CD4 T-cells (Spearman = -0.52, P = 0.004), and lower premaraviroc HIV-1 DNA levels were associated with larger decreases in %CD38HLA-DR CD4 T-cells during maraviroc intensification (Spearman = 0.44, P = 0.018). CONCLUSION: In individuals on suppressive ART with incomplete CD4 T-cell recovery, maraviroc intensification did not affect measures of HIV-1 persistence but did decrease persistent CD4 T-cell immune activation especially in individuals with low preintensification levels of HIV-1 DNA.

Effects of dexamethasone and Mycoplasma bovis on bovine neutrophil function in vitro.

It is well established that exposure either to elevated levels of glucocorticoids, or to Mycoplasma bovis (M. bovis), has a negative effect on bovine neutrophil function. The objective of this research was to determine whether in vitro treatment of bovine neutrophils by M. bovis strains (n=4) and glucocorticoids would additively impair phagocyte function. Twenty, healthy, dairy cows were enrolled. Whole blood was collected from all cows for neutrophil isolation. Phagocytosis and the generation of superoxide anion (O2(-)) were tested in vitro by incubation of neutrophils with FITC labeled Escherichia coli (E. coli) and cytochrome c after treatment. Treatments included: NM1-4D (neutrophils treated with dexamethasone and exposed to one of the four M. bovis strains); NM1-4 (neutrophils exposed to one of the four M. bovis strains only); ND (neutrophils treated with dexamethasone only); and N (non-treated control neutrophils). The overall percentages of neutrophils phagocytizing E. coli were: 32%, 51%, 37%, and 53% ± 5.25% for treatments NM1-4D, NM1-4, ND, and N, respectively. The overall statistically transformed means of phagocytized E. coli per neutrophil were: 1.37, 1.72, 1.33, and 1.67 ± 0.057 for treatments NM1-4D, NM1-4, ND, and N, respectively. The overall statistically transformed means of neutrophil O2(-) production were: 8.60, 11.91, 9.01, and 12.21 ± 0.21 nmol/10(6) for treatments NM1-4D, NM1-4, ND, and N, respectively. Exposure of neutrophils to M. bovis plus dexamethasone had an additive effect on generation of reactive oxygen species (p=0.0057), but not on the percentage of neutrophils phagocytizing E. coli (p=0.0817) or number of E. coli phagocytized per neutrophil (p=0.2946). Only one of the four M. bovis strains had a negative effect on neutrophil phagocytic function. Dexamethasone treatment consistently decreased neutrophil function as indicated by decreased percentage of neutrophils phagocytizing E. coli, decreased number of E. coli phagocytized per neutrophil, and decreased neutrophil O2(-) production, compared to controls (p<0.0001). Results suggested a synergistic effect of in vitro incubation of glucocorticoids and M. bovis on reduction of bovine neutrophil function as measured by generation of reactive oxygen species. These findings may explain in part the interaction between stressful events and outbreak of Mycoplasma bovis associated bovine disease.

Complete Genome Sequence of the Bovine Mastitis Pathogen Mycoplasma californicum Strain ST-6T (ATCC 33461T).

Mycoplasma californicum is one of several mycoplasmal species associated with bovine mastitis. The complete genome sequence of 793,841 bp has been determined and annotated for the M. californicum ST-6 type strain, providing a resource for the identification of surface antigens and putative pathoadaptive features.

Dissimilarity of ccrAB gene sequences between methicillin-resistant Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus among bovine isolates in Korea.

The sequences of the ccrAB genes from bovine-, canine- and chicken-originating methicillin-resistant Staphylococcus (S.) epidermidis (MRSE) and bovine methicillin-resistant Staphylococcus (S.) aureus (MRSA) were compared to investigate the frequency of intra-species horizontal transfer of the staphylococcal cassette chromosome mec (SCCmec) complex. Nineteen MRSE strains were isolated from bovine milk, chickens, and dogs, and their genetic characteristics were investigated by multilocus sequence typing and SCCmec typing. Among the animal MRSE strains, the most frequent SCCmec type was type IV, which consisted of the type B mec complex and ccrAB type 2. The ccrA2 and ccrB2 genes were sequenced from the bovine, chicken and canine MRSE strains and compared with those of the bovine MRSA strains. The sequences generally clustered as MRSA and MRSE groups, regardless of the animal source. Additionally, no bovine MRSE sequence was associated with the bovine MRSA groups. Although most of the bovine MRSE and MRSA isolates possessed SCCmec type IV sequences, our results suggest that the intra-species gene transfer of the SCCmec complex between bovine S. aureus and bovine S. epidermidis strains is not a frequent event.

Effects of tulathromycin on incidence of various diseases and growth of young heifers.

OBJECTIVE: To determine the effects of administration of 1 dose of tulathromycin on the incidence of various diseases and growth, identify risk factors for slow growth, and determine the association of Mycoplasma bovis status with the incidence of otitis media in calves. DESIGN: Randomized controlled trial and cross-sectional study. ANIMALS: 788 dairy heifer calves (median age, 3 days). PROCEDURES: Calves received tulathromycin or a saline (0.9% NaCl) solution control treatment once. Calves were observed daily for 8 weeks by farm staff to detect diseases. Nasal swab specimens were collected from some calves for Mycoplasma spp culture. RESULTS: Tulathromycin-treated calves had significantly lower odds of developing otitis media (OR, 0.41; 95% confidence interval, 0.58 to 0.82) versus control calves. Control calves had significantly higher odds of developing diarrhea (OR, 1.8; 95% confidence interval, 1.2 to 2.6) versus tulathromycin-treated calves. Control calves and those with failure of passive transfer, fever, lameness, respiratory tract disease, or diarrhea had significantly lower average daily gain versus other calves. Seventeen of the 66 (26%) calves that underwent repeated testing had positive Mycoplasma spp culture results, but positive results were not associated with otitis media. One of 42 calves with otitis media tested for Mycoplasma spp had positive results, and 1 of 43 age-matched calves without otitis media had positive results. CONCLUSIONS AND CLINICAL RELEVANCE: Tulathromycin-treated calves in this study had a lower incidence of diarrhea and otitis media versus control calves. Various diseases had negative effects on average daily gain. Mycoplasma bovis status was not associated with otitis media in calves.

A Staphylococcus xylosus isolate with a new mecC allotype.

Recently, a novel variant of mecA known as mecC (mecA(LGA251)) was identified in Staphylococcus aureus isolates from both humans and animals. In this study, we identified a Staphylococcus xylosus isolate that harbors a new allotype of the mecC gene, mecC1. Whole-genome sequencing revealed that mecC1 forms part of a class E mec complex (mecI-mecR1-mecC1-blaZ) located at the orfX locus as part of a likely staphylococcal cassette chromosome mec element (SCCmec) remnant, which also contains a number of other genes present on the type XI SCCmec.