Antimicrobial susceptibility patterns and sensitivity to tulathromycin in goat respiratory bacterial isolates

Antimicrobial Susceptibility and Resistance Mechanisms in Mannheimia haemolytica Isolates from Sheep at Slaughter

Mannheimia haemolytica is the main pathogen contributing to pneumonic pasteurellosis in sheep. The aim of this study was to investigate the antimicrobial resistance levels in M. haemolytica isolates from the lungs of slaughtered sheep and to examine the genetic resistance mechanisms involved. A total of 256 M. haemolytica isolates, 169 from lungs with pneumonic lesions and 87 from lungs without lesions, were analyzed by the disk diffusion method for 12 antimicrobials, and the whole genome of 14 isolates was sequenced to identify antimicrobial resistance determinants. Levels of phenotypic resistance ranged from <2% for 10 antimicrobials (amoxicillin, amoxicillin-clavulanic, ceftiofur, cefquinome, lincomycin/spectinomycin, gentamicin, erythromycin, florfenicol, enrofloxacin, and doxycycline) to 4.3% for tetracycline and 89.1% for tylosin. Six isolates carried tetH genes and four isolates carried, in addition, the strA and sul2 genes in putative plasmid sequences. No mutations associated with macrolide resistance were identified in 23 rDNA sequences, suggesting that the M. haemolytica phenotypic results for tylosin should be interpreted with care in the absence of well-established epidemiological and clinical breakpoints. The identification of strains phenotypically resistant to tetracycline and of several resistance genes, some of which were present in plasmids, highlights the need for continuous monitoring of susceptibility patterns in Pasteurellaceae isolates from livestock.

Assessment of animal diseases caused by bacteria resistant to antimicrobials: sheep and goats

In this opinion, the antimicrobial-resistant bacteria responsible for transmissible diseases that constitute a threat to the health of sheep and goats have been assessed. The assessment has been performed following a methodology based on information collected by an extensive literature review and expert judgement. Details of the methodology used for this assessment are explained in a separate opinion. A global state of play on antimicrobial resistance in clinical isolates of Staphylococcus aureus, Escherichia coli (non-VTEC), Pseudomonas aeruginosa, Dichelobacter nodosus, Moraxella ovis, Mannheimia haemolytica, Pasteurella multocida, Mycoplasma ovipneumoniae, Mycoplasma agalactiae, Trueperella pyogenes, Streptococcus uberis, Bibersteinia trehalosi, Campylobacter fetus, Mycoplasma mycoides subsp. capri, Mycoplasma capricolum subsp. capricolum, Fusobacterium necrophorum is provided. Among those bacteria, EFSA identified E. coli with ≥ 66% certainty as being the most relevant antimicrobial-resistant bacteria in sheep and goat in the EU based on the available evidence. The animal health impact of these most relevant bacteria, as well as their eligibility for being listed and categorised within the animal health law framework will be assessed in separate scientific opinions.

Comparison of Antimicrobial Treatment Incidence Quantification Based on Detailed Field Data on Animal Level with the Standardized Methodology of the European Medicines Agency in Veal Calves, Switzerland, 2016-2018

Precise quantification of antimicrobial treatment incidence (TI) is crucial for benchmarking. Two widespread methods for treatment incidence quantification were compared for agreement. Field data were obtained from 38 veal farms from 2016 to 2018 (1905 calves, 1864 treatments). Calculation of TI_swiss for calves was based on detailed treatment records using pharmacokinetic values from the Swiss Veterinary Medicines Compendium. The method published by the European Medicines Agency was used to calculate TI in defined daily doses (TI_DDD). For each calf and treatment, TI_swiss and TI_DDD were calculated on level of the antimicrobial class, drug, application route, and farm. The quotient (Q) of TI_swiss and TI_DDD was calculated. Divergence in results between the two methods of ≤25% was arbitrarily set as good agreement. The agreement between TI_swiss and TI_DDD was mostly good. On class level, good agreement was observed for treatments representing 71.5% of the TI_DDD, and 74.5% of the total TI_DDD on drug level. Poor agreement was mainly observed for tylosin and sulfadimidine. The agreement was better for parenteral than for oral treatments (81.6% vs. 72.3%). For practically orientated calculation on farm level, good agreement was observed (77.5% of the TI_DDD). The TI_DDD method showed mostly good agreement, especially for parenteral treatments.

Effects of rifampicin on plasma pharmacokinetics of tulathromycin in goats

We investigated the pharmacokinetic profile of co-administration of tulathromycin with rifampicin. Healthy male goats were allocated to three groups (n = 8) as Group A (single dose 2.5 mg/kg tulathromycin s.c.), B (10 mg kg^-1  day^-1 rifampicin p.o. daily for 7 days and single dose 2.5 mg/kg tulathromycin s.c. on 8th day), and C (10 mg kg^-1  day^-1 rifampicin p.o. daily for 21 days and single dose 2.5 mg/kg tulathromycin s.c. on 8th day). Blood samples were collected from jugular veins. Plasma samples were analyzed for tulathromycin by liquid chromatography-mass spectrometry (LC-MS/MS). Peak plasma concentration (C_max ) values of tulathromycin were 1,390 ± 173, 958 ± 106, and 807 ± 116 ng/ml in groups A, B, and C, respectively. C_max value of group A was greater than other groups (p < .05). Mean residence time based on time zero to last sample time (MRT_last ) values were 52 ± 1, 56 ± 4 and 66 ± 4 hr in A, B, and C groups, respectively whereas mean residence time based on time zero extrapolated to infinity (MRT_{INF_obs} ) values were 69 ± 4, 85 ± 5, and 86 ± 4 hr, respectively. MRT_last and MRT_{INF_obs} values were greater in B and C groups than group A (p < .05). These findings suggest that rifampicin administration may change several pharmacokinetic parameters of tulathromycin in goats.

Evaluation of a Pasteurella multocida Respiratory Disease Induction Model for Goats (Capra aegagrus hircus)

Infectious respiratory diseases are a serious health concern worldwide. However, few models describe the experimental induction of lung infection, or the effect of experimental infection on clinical pathologic parameters in goats. Goats offer benefits compared to cattle because of size and tractability and compared to sheep with regard to specific features of their anatomy. In previous experimental models of infection in goats, coadministration of an immunosuppressive dose of a corticosteroid is common; however, protocols that use corticosteroid often note mortality as an adverse effect. We therefore investigated an infection protocol that did not use immunosuppression but instead relied on 2 intratracheal inoculations of Pasteurella multocida in healthy meat goats to induce clinical and hematologic changes associated with respiratory infection. Healthy Boer or Boer-Kiko cross goats (n = 6; age, 10 mo) were inoculated with Pasteurella multocida and were monitored over a 312-h period for clinical and hematologic parameters of infection. After induction of pneumonia, the goats had a significant 1.2 °C rise in rectal temperature and auscultatable rales for up to 96 h. Lymphocyte counts, serum amyloid A values, and respiratory scores were significantly different before and after induction of disease and were consistent with respiratory infection. No mortality was associated with this experimental infection, and minimal gross pathologic changes were noted at study termination. The clinical and pathologic findings of this study suggest a potentially reproducible method of establishing clinical respiratory infection in goats. The repeated intratracheal inoculation method of inducing caprine respiratory disease can be used to produce experimental respiratory disease in goats when the use of corticosteroid is not desirable. With the feasibility of this method established, additional research evaluating the optimal dose and frequency of P. multocida administration is needed.

Effects of experimentally induced respiratory disease on the pharmacokinetics and tissue residues of tulathromycin in meat goats

Tulathromycin is a macrolide antibiotic commonly used for the treatment of respiratory disease in food animal species including goats. Recent research in pigs has suggested that the presence of disease could alter the pharmacokinetics of tulathromycin in animals with respiratory disease. The objectives of this study were (a) compare the plasma pharmacokinetics of tulathromycin in healthy goats as well as goats with an induced respiratory disease; and (b) to compare the tissue residue concentrations of tulathromycin marker in both groups. For this trial, disease was induced with Pasteurella multocida. Following disease induction, tulathromycin was administered. Samples of plasma were collected at various time points up to 312 hr posttreatment, when study animals were euthanized and tissue samples were collected. For PK parameters in plasma, V_z (control: 28.7 ± 11.9 ml/kg; experimental: 57.8 ± 26.6 ml/kg) was significantly higher (p = 0.0454) in the experimental group than the control group, and nonsignificant differences were noted in other parameters. Among time points significantly lower plasma concentrations were noted in the experimental group at 168 hr (p = 0.023), 216 hr (p = 0.036), 264 hr (p = 0.0017), 288 hr (p = 0.0433), and 312 hr (p = 0.0486). None of the goats had tissue residues above the US bovine limit of 5 µg/g at the end of the study. No differences were observed between muscle, liver, or fat concentrations. A significantly lower concentration (p = 0.0095) was noted in the kidneys of experimental goats when compared to the control group. These results suggest that the effect of respiratory disease on the pharmacokinetics and tissue residues appear minimal after experimental P. multocida infection, however as evidenced by the disparity in C_max , significant differences in plasma concentrations at terminal time points, as well as the differences in kidney concentrations, there is the potential for alterations in diseased versus clinical animals.

Comparing clinical effects of marbofloxacin and gamithromycin in goat kids with pneumonia

The aim of this study was to compare the clinical efficacy of a single-dose of gamithromycin (GM) or marbofloxacin (MR) in kids with naturally occurring pneumonia. Thirty-six kids, aged 2-2.5 months, with body weight ranging from 12 kg to 18 kg were presented with clinical signs of pneumonia. The most prominent clinical findings were an increase in the respiratory rate, crackling lung sounds on auscultation, coughing, nasal discharge and an increased rectal temperature. Mannheimia haemolytica and Mycoplasma spp. colonies were isolated from microbiological examination of six transtracheal washes and lung tissues of one necropsied kid. The severity of pneumonia was evaluated by using cumulative clinical score (CCS). The CCS of the 36 kids used in the study were four and above. Kids were randomly divided into two equal groups; the GM group received a single subcutaneous dose of GM at a dosage of 6 mg/kg and the MR group received MR intramuscularly at a dosage of 8 mg/kg as a single-dose. No side effects related to the drugs were detected in either group. All 36 kids were clinically examined 3 weeks after the initiation of the treatment. Clinical signs in both groups were almost completely absent at the end of the study. A single administration of GM or MR was successfully used in the treatment of kids with pneumonia.

Complete Closed Genome Sequences of Three Bibersteinia trehalosi Nasopharyngeal Isolates from Cattle with Shipping Fever

Bibersteinia trehalosi is a respiratory pathogen affecting cattle and related ruminants worldwide. B. trehalosi is closely related to Mannheimia haemolytica and is often associated with bovine respiratory disease complex (BRDC), a polymicrobial multifactorial disease. We present three complete closed genome sequences of this species generated using an automated assembly pipeline.

Estimating tulathromycin withdrawal time in pigs using a physiologically based pharmacokinetics model

A physiologically based pharmacokinetics model was developed to predict tulathromycin concentrations in edible swine tissues. Physiological parameters included volumes of and plasma flows through different tissues which were obtained from the literatures. The tissue/plasma partition coefficient was calculated according to the area method, and the model was validated through a comparison of predicted and observed concentrations. Withdrawal times in different tissues were predicted. The physiologically based pharmacokinetics model presented here provided accurate predictions of the observed concentrations in all tissues. The results showed that the injection site had the longest withdrawal time (21 days), followed by skin together with fat (19 days) and then kidney (10 days), lung (6 days), liver (4 days) and muscle (1 day). A withdrawal time of 21 days was finally predicted for tulathromycin in swine after a single intramuscular injection at 2.5 mg/kg body weight.

Diversity of bacterial species in the nasal cavity of sheep in the highlands of Ethiopia and first report of Histophilus somni in the country

A study was conducted to isolate bacterial species/pathogens from the nasal cavity of apparently healthy and pneumonic sheep. Nasal swabs were collected aseptically, transported in tryptose soya broth and incubated for 24 h. Then, each swab was streaked onto chocolate and blood agar for culture. Bacterial species were identified following standard bacteriological procedures. Accordingly, a total of 1,556 bacteria were isolated from 960 nasal swabs collected from three different highland areas of Ethiopia, namely Debre Berhan, Asella, and Gimba. In Debre Berhan, 140 Mannheimia haemolytica, 81 Histophilus somni, 57 Staphylococcus species, and 52 Bibersteinia trehalosi were isolated. While from Gimba M. haemolytica, Staphylococcus, Streptococcus, and H. somni were isolated at rates of 25.2, 15.9, 11.4, and 5.9 %, respectively, of the total 647 bacterial species. In Asella from 352 bacterial species isolated, 93 (26.4 %) were M. haemolytica, 48 (13.6 %) were Staphylococcus species, 26 (7.4 %) were B. trehalosi, and 17 (4.8 %) H. somni were recognized. Further identification and characterization using BIOLOG identification system Enterococcus avium and Sphingomonas sanguinis were identified at 100 % probability, while, H. somni and Actinobacillus lignerisii were suggested by the system. The study showed that a variety of bacterial species colonize the nasal cavity of the Ethiopian highland sheep with variable proportion between healthy and pneumonic ones. To our knowledge, this is the first report on isolation of H. somni, an important pathogen in cattle, from the respiratory tract of a ruminant species in the country.