Evaluation of the effect of therapeutic durations on small ruminant bacterial pneumonia.

BACKGROUND: Sheep and goat production in Ethiopia is hindered by numerous substandard production systems and various diseases. Respiratory disease complexes (RDC) pose a significant threat to the productivity of these animals. Pneumonia is a common manifestation of respiratory disease complexes and often necessitates a prolonged course of antibiotic treatment. This study aimed to optimize and propose the ideal duration of therapy for pneumonia in sheep and goats. METHODS: The study was conducted from February to June 2021 at the Veterinary Teaching Hospital of the College of Veterinary Medicine and Agriculture, Addis Ababa University. The study recruited 54 sheep and goats presented to the hospital for treatment with a confirmed RDC as determined based on clinical signs and bacteriological methods. The animals were randomly allocated to 5 groups each group receiving 10% oxytetracycline (Phenxyl, Phenix, Belgum) intramuscularly for a duration of 3, 4, 5, 6 and 7 consecutive days. The treatment outcomes were assessed by recording vital signs (body temperature, respiratory rate, heart rate, coughing, and nasal discharges), performing lung ultrasonography (L-USG) as well as collection of nasal swabs for bacterial isolation and molecular identification before and after completion of the treatment. An ordered logistic regression model with random effects was employed to determine the optimal therapeutic duration, taking into account the cumulative scores of the outcome variables across the different groups. RESULTS: Among the 54 sheep and goats treated with 10% oxytetracycline, a total of 74.07% (95% CI, 60.35-85.04) achieved complete recovery, as confirmed through clinical, ultrasound, and bacteriological methods. In Group 1 (G1), out of 12 sheep and goats, 8 (83.0%) recovered completely; in Group 2 (G2), out of 11 animals, 9 (82.0%) recovered completely; in Group 3 (G3), out of 11 animals, 10 (93.0%) recovered completely; in Group 4 (G4), out of 9 animals, 9 (100.0%) recovered completely; and in Group 5 (G5), out of 11 animals, 10 (91.0%) recovered completely. Bacteriological examination of nasal swabs indicated involvement of M. hemolytica in 27 (50.00%) and P. multocida in 13 (24.07%) of pneumonic animals. Detection of specific marker genes confirmed only five of the presumptive M. hemolytica isolates, whilst no isolates tested positive for P. multocida. Post-treatment samples collected from recovered animals did not yield any M. hemolytica nor P. multocida. Based on results from clinical signs, L-USG, and bacterial infection variables, the group of sheep and goats treated for seven consecutive days (G5) showed the highest recovery score compared to the other groups, and there was a statistically significant difference (coefficient (ß) = - 2.296, p = 0.021) in variable score between G5 and G1. These findings suggest that the administration of 10% oxytetracycline for a full course of seven consecutive days resulted in symptomatic and clinical recovery rates from respiratory disease in sheep and goats.

Effect of different post-partum therapeutic protocols with intrauterine oxytetracycline, oxytocin and/or GnRH injection in post-kidding goats on oxytetracyclines residues in goat milk and postpartum ovarian resumption with referring to clinical and haematological pictures.

BACKGROUND: The post-parturient period in goat had marked changes in an animal's endocrine and metabolic status as well as by reduction in feed intake when the nutrient demand for impending lactogenesis was increasing. The current study aimed to monitor the residues of oxytetracycline in Baladi goat milk and their hazards on public health as well as the time required until complete disappearance of this medicament from milk through following up periods included 0, 12, 24, 36, 48, 60, 72, 84, 96 and 120 h in post-kidding goat following intrauterine application of oxytetracycline. The study also compared between the efficacy of oxytetracycline only, oxytetracycline with oxytocin, or oxytetracycline with GnRH, through monitoring the clinical findings and haematological pictures at days 0, 5 and 7 post-partum as well as studying the changes in numbers and size of follicles at days 15, 30 and 45 postpartum after different treatments strategies in different groups i.e. Control healthy goat (Contgr), Oxytetracycline treated goat (Oxytetgr), Oxytetracycline-oxytocin treated goat (Oxytet-Oxytogr) and Oxytetracycline-GnRH treated goat (Oxytet-GnRHgr). The study was carried out on clinically healthy Baladi goats (n = 40) that gave birth recently. They were divided into 4 equal groups (n = 10 goats for each); Contgr which received no medication after birth, Oxytetgr which administrated oxytetracycline tablets intrauterine at day of birth, Oxytet-Oxytogr which treated by oxytetracycline tablets intrauterine at day of birth followed by oxytocin injection at 3rd day after birth, and Oxytet-GnRHgr which treated by oxytetracycline tablets intrauterine at day of birth followed by GNRH injection at 3rd day after birth. RESULTS AND CONCLUSIONS: The study concluded the highest oxytetracyclines residues in goats' milk were reported after 36 h following intrauterine oxytetracycline application where complete disappearance of oxytetracyclines residues in goats' milk required 120 h elapsed after intrauterine oxytetracycline application in which the goats milk became safe for human consumption. The study also reported powerful influence of the applied variable therapeutic regimens on post-partum ovarian resumption through clear significant variations in numbers and sizes of follicles either between different goats' groups within the same day, or between days 15, 30 and 45 post-partum within each independent goat group.

Therapeutic efficacy of enrofloxacin in treatment of Francisella orientalis infections in juvenile Nile tilapia (Oreochromis niloticus L.).

Outbreaks of infections by Francisella orientalis represent one of the main obstacles to Nile tilapia (Oreochromis niloticus L.) farming. It is responsible for acute mortality in fingerlings and juveniles. The main control measure available is oral antibiotic therapy. This study compared the therapeutic efficacy of the antibiotics enrofloxacin and oxytetracycline, the most commonly used antimicrobial, against francisellosis in juvenile Nile tilapia (O. niloticus). Fish were challenged with a virulent isolate of F. orientalis and treated with medicated feed containing one of two doses of oxytetracycline (100 or 300 mg/kg of live weight (LW)) or 10 mg/kg of LW of enrofloxacin. The positive and negative control groups received feed without antibiotics; the negative control group was unchallenged. The results showed that enrofloxacin at a dose of 10 mg/kg of LW is effective against francisellosis in juvenile Nile tilapia (O. niloticus). Treatment with oxytetracycline did not eliminate the pathogen from the infected host, and the surviving fish became carriers. Enrofloxacin was able to cure the fish of infection with F. orientalis. This study suggests that enrofloxacin is a better option for treating francisellosis in Nile tilapia (O. niloticus L.). It controls mortality and avoids the carrier state in the fish, thus reducing the possibility of recurrence in the affected batches.

Efficiency of conventional and nanoparticle oxytetracycline in treatment of clinical endometritis in postpartum dairy cows.

The incidence of clinical endometritis in dairy cows postpartum is one of the important reasons for financial losses in the dairy industry. The costs of treatment, milk losses, infertility, repeated breeding, and high annual culling rate of dairy cows present immediate losses in case of treatment failure. The commonly used therapeutic methods for clinical endometritis have not been successful nor have given definitive solutions to overcome the complications of the disease in dairy cows. Therefore, it was necessary to propose an innovative treatment program to overcome the reasons for the failure and lack of effectiveness of the treatment of clinical endometritis. This was tackled in the current study; oxytetracycline with different concentrations, oxytetracycline 5% (OTCC5%), oxytetracycline 20% (OTCC20%), and oxytetracycline 20% nanoparticles (OTC-NPs) were used for the treatment of clinical endometritis. Diagnosis of clinical endometritis was based on the assessment of high serum concentration of pro-inflammatory cytokines, acute phase protein, increased endometrium thickness, and intrauterine discharges with different degrees of echogenicity monitored by ultrasonography. Application of OTC-NPs revealed a decrease in serum concentration of pro-inflammatory cytokines (IL-1, IL-6, and TNF-α) and acute phase proteins compared to OTCC20% and OTCC5% groups. The improvement achieved by OTC-NPs may be attributed to the reduction of OTC particles into nano size which facilitates its tissue bioavailability, dispersion, penetration power to deeper tissues, and its more broad-spectrum activities. These activities were clearly apparent after the evacuation of uterine contents using a single dose of PGF2α. The OTC-NPs revealed a reduction in serum concentration of cytokines compared to OTCC20% and OTCC5% groups arranged as follows: 10.11, 25.45, 35.56 for IL-1; 99, 300, 319 for IL-6; 1.01, 4.40, 8.06 for CRP; and 46, 183, 266 for TNF-α. Furthermore, an increase in serum concentration of albumin (3.34) was obtained by OTC-NPs compared to OTCC5% (1.70). This improvement can be taken as evidence of liver resumption functions and inflammatory reactions. On the other side, globulin concentration recorded an increase like albumin and total proteins in OTC-NPs compared to others. A reduction in the endometrium thickness in OTC-NPs with the disappearance of intrauterine discharges was monitored by ultrasonography. This confirmed the subsiding of clinical endometritis in OTC-NPs group. Moreover, a significant improvement in conception and pregnancy rate in OTC-NPs compared to other groups were observed.

In vitro susceptibility of Mycoplasma iowae isolates to antimicrobial agents.

ABSTRACTMycoplasma iowae, a potential re-emerging avian pathogen mainly affecting turkeys, has been reported from many parts of the world. Poor hatchability, embryonic death, joint and skeletal abnormalities, poor ossification, runting-stunting, poor feathering and airsacculitis may be observed in infected flocks. The reduction of the severity of clinical signs and short-term control of M. iowae are performed by antibiotic treatment. However, M. iowae develops resistance more rapidly and is considered to be more resistant to antimicrobials than other avian pathogenic mycoplasmas. The aim of the present study was to determine the in vitro susceptibility of 101 M. iowae isolates and strains to ten clinically important antimicrobial agents, and to analyse and compare the susceptibility patterns of isolates of various origins and from a wide time-period. The examined reference strains showed high susceptibility to all antimicrobials except for spectinomycin. Low concentrations of tiamulin, florfenicol and oxytetracycline inhibited the growth of the clinical isolates. Nevertheless, slow tendency of increasing minimum inhibitory concentration (MIC) values was observed over time in the case of the above mentioned agents, while MIC values of enrofloxacin showed relatively rapid changes. Spiramycin, erythromycin, tilmicosin, tylosin, lincomycin and spectinomycin did not inhibit the bacterial growth in most of the cases. Isolates originating from captive game birds showed similar susceptibility profiles to isolates from industrial turkey hosts. The widely detected low susceptibility of M. iowae isolates to macrolides, lincomycin and spectinomycin, and the increase of MIC values of frequently used antimicrobials against this pathogen, emphasize the importance of targeted antibiotic therapy.RESEARCH HIGHLIGHTSAntimicrobial susceptibilities of 101 Mycoplasma iowae isolates were determined.Minimum inhibitory concentrations were determined by broth micro-dilution method.Tiamulin, oxytetracycline and florfenicol showed low MIC values.Isolates rapidly adapted to antimicrobial pressure.

Susceptibility of caprine mastitis pathogens to tildipirosin, gamithromycin, oxytetracycline, and danofloxacin: effect of serum on the in vitro potency of current macrolides.

Mastitis is a significant disease in dairy ruminants, causing economic losses to the livestock industry and severe risks to public health. Antibiotic therapy is one of the most crucial practices to treat mastitis, although the susceptibility of caprine mastitis pathogens to current antibiotics has not been tested under standard or modified incubation conditions. This work evaluated the in vitro activity of tildipirosin, gamithromycin, oxytetracycline, and danofloxacin against caprine mastitis pathogens incubated following standard conditions of Clinical and Laboratory Standards Institute (CLSI) and deviation method by 25% supplementation with goat serum. Mycoplasma agalactiae, Escherichia coli, Staphylococcus aureus, Streptococcus spp., and coagulase-negative Staphylococci (CNS) were isolated from dairy goats with mastitis in Spain. Minimum inhibitory concentrations (MICs) were determined using the broth microdilution technique. The lowest MIC90 under standard conditions was obtained with danofloxacin for mastitis-causing pathogens. An exception was M. agalactiae, where danofloxacin and oxytetracycline obtained low values. However, after adding serum, gamithromycin showed the lowest MIC50 for S. aureus, Streptococcus spp., and CNS. The lowest MIC50 was obtained with all the antibiotics tested (< 0.125 µg/ml) against M. agalactiae. Supplementing with serum resulted in a significant variation in tildipirosin and gamithromycin MIC values for CNS, S. aureus, M. agalagtiae, and E. coli. In brief, the MIC for antibiotics used against mastitis should be determined under conditions closely resembling intramammary infections to obtain representative susceptibility patterns against mastitis pathogens. Caprine mastitis pathogens were broadly susceptible to danofloxacin under standard conditions. The potency of macrolides against caprine mastitis pathogens increases when serum is present in culture media.

First isolation of Klebsiella variicola from a horse pleural effusion.

BACKGROUND: Respiratory diseases are the second most common cause of illnesses in horses, their etiology can be viral, bacterial, immune-mediated, or mechanical (Racklyeft and Love DN, Aust Vet J 78:549-59, 2000; Austin et al., J Am Vet Med Assoc 207:325-328, 1995; Arroyo et al., J Vet Intern Med 31:894-900, 2017). Klebsiella variicola is a Gram-negative bacterium that was initially identified as an endophyte in soil and plants such as bananas, rice, sugar cane and maize but recent studies have identified this microorganism as an emerging pathogen in humans (Rodríguez-Medina et al., Emerg Microbes Infect 8:973-988, 2019; Fontana et al., J Clin Microbiol 57:e00825-18, 2019; Rosenblueth et al., Syst Appl Microbiol 27:27-35, 2004). This paper describes, for the first time to our knowledge, the isolation of K. variicola from pleural effusion in a male adult horse. CASE PRESENTATION: 17-years Italian Saddle Horse with respiratory distress and fever was admitted to the Veterinary Teaching Hospital of the Department of Veterinary Medical Sciences, University of Bologna. At home, the patient had undergone antibiotic therapy without clinical improvement. Vital signs on admission revealed an increased respiratory rate, tachycardia, pyrexia and weight loss. The animal was submitted for collateral examination including thoracic radiology and ultrasound and thoracoscopy that showed bilateral pleural effusion associated with multifocal pulmonary atelectasis. During the thoracoscopic examination, that confirmed the presence of a seropurulent pleural effusion, a sample of pleural fluid was collected and Gram-negative bacteria were isolated and subjected to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) that allowed the identification of K. variicola. The isolate was sensitive to amikacin, cefazolin, enrofloxacin, marbofloxacin, tetracycline, and trimethoprim-sulfamethoxazole;the horse was treated with Oxytetracycline and amikacin. Despite a general health improvement of the subject, the pleural effusion did not resolve after treatment. CONCLUSIONS: This paper describes, for the first time, the isolation of K. variicola in a horse with respiratory disease. The misidentification between K. variicola and K. pneumoniae has caused unawareness about significant aspects of this bacterial species. In fact, even though in animals the role of this bacterium is not clear, in humans it has been recognized as an emerging pathogen. The use of new methods for bacterial identification will probably lead to the isolation of a greater number of strains which will have to be studied to acquire knowledge that will be useful to clarify the clinical importance and relevance of K. variicola also in animals.

Oxytetracycline reduces inflammation and treponeme burden whereas vitamin D3 promotes ß-defensin expression in bovine infectious digital dermatitis.

Digital dermatitis (DD), a common ulcerative disease of the bovine foot causing lameness and reducing productivity and animal welfare, is associated with infection by spirochete Treponema bacteria. Topical tetracycline, the most common treatment, has inconsistent cure rates; therefore, new therapeutic options are needed. We compared effects of topical oxytetracycline and vitamin D3 on innate immunity in DD-affected skin. Cows with active DD lesions were treated topically with oxytetracycline or vitamin D3 and skin biopsies were collected from lesions. Tissue samples were examined histologically, transcriptional expression of pro-inflammatory cytokines, Toll-like receptors (TLRs), and host defense peptides assessed, and the presence of specific treponeme species determined. Effects of treatments at a mechanistic level were studied in a human keratinocyte model of treponeme infection. Oxytetracycline promoted hyperplastic scab formation in ulcerated DD lesions and decreased transcriptional expression of Cxcl-8 (neutrophil chemoattractant). Oxytetracycline also reduced numbers of Treponema phagedenis and T. pedis and enhanced Tlr2 mRNA expression. Vitamin D3 did not modify expression of cytokines or Tlrs, or bacterial loads, but enhanced transcription of tracheal antimicrobial peptide (Tap), a key bovine ß-defensin. Combing oxytetracycline and vitamin D3 provides complementary clinical benefits in controlling DD through a combination of antimicrobial, immunomodulatory, and pro-healing activities.

A tick cell line as a powerful tool to screen the antimicrobial susceptibility of the tick-borne pathogen Anaplasma marginale.

Anaplasma marginale is the causative agent of the severe bovine anaplasmosis. The tick Rhipicephalus microplus is one of the main vectors of A. marginale in tropical and subtropical regions of the world. After the tick bite, the bacterium invades and proliferates within the bovine erythrocytes leading to anemia, impairment of milk production and weight loss. In addition, infection can cause abortion and high mortality in areas of enzootic instability. Immunization with live and inactivated vaccines are employed to control acute bovine anaplasmosis. However, they do not prevent persistent infection. Consequently, infected animals, even if immunized, are still reservoirs of the bacterium and contribute to its dissemination. Antimicrobials are largely employed for the prophylaxis of bovine anaplasmosis. However, they are often used in sublethal doses which may select pre-existing resistant bacteria and induce genetic or phenotypic variations. Therefore, we propose a new standardized in vitro assay to evaluate the susceptibility of A. marginale strains to different antimicrobials. This tool will help health professionals to choose the more adequate treatment for each herd which will prevent the selection and spread of resistant strains. For that, we initially evaluated the antimicrobial susceptibility of two field isolates of A. marginale (Jaboticabal and Palmeira) infecting bovines. The least susceptible strain (Jaboticabal) was used for the standardization of an antimicrobial assay using a culture of Ixodes scapularis-derived tick cell line, ISE6. Results showed that enrofloxacin (ENRO) at 0.25, 1 or 4 µg/mL and oxytetracycline (OTC) at 4 or 16 µg/mL are the most efficient treatments, followed by OTC at 1 µg/mL and imidocarb dipropionate (IMD) at 1 or 4 µg/mL. In addition, this proposed tool has technical advantages compared to the previously established bovine erythrocyte culture. Thereby, it may be used to guide cattle farmers to the correct use of antimicrobials. The choice of the most suitable antimicrobial is essential to eliminate persistent infections, prevent the spread of resistant strains and help controlling of bovine anaplasmosis.

Quantification of Veterinary Antibiotics in Pig and Poultry Feces and Liquid Manure as a Non-Invasive Method to Monitor Antibiotic Usage in Livestock by Liquid Chromatography Mass-Spectrometry.

Antibiotics are active substances frequently used to treat and prevent diseases in animal husbandry, especially in swine and poultry farms. The use of manure as a fertilizer may lead to the dispersion of antibiotic residue into the environment and consequently the development of antibiotic-resistant bacteria. Most pharmaceutical active ingredients are excreted after administration, in some cases up to 90% of the consumed dose can be found in the feces and/or urine as parent compound. Therefore, due to antibiotic metabolism their residues can be easily detected in manure. This article describes a method for simultaneous analysis of ciprofloxacin, chlortetracycline, doxycycline, enrofloxacin, lincomycin, oxytetracycline, tetracycline, tiamulin, trimethoprim and tylosin in feces, liquid manure and digestate. Antibiotics were extracted from the different matrices with McIlvaine-Na2EDTA buffer solution and the extract was purified by the use two techniques: d-SPE and SPE (Strata-X-CW cartridges) and final eluent was analyzed by LC-MS and LC-MS/MS. The European Commission Decision 2002/657/EC was followed to conduct the validation of the method. Recoveries obtained from spiked pig and poultry feces and liquid manures samples ranged from 63% to 93% depending on analytes. The analysis of 70 samples (feces, liquid manure and digestate) revealed that 18 samples were positive for the presence of doxycycline, oxytetracycline, tetracycline, chlortetracycline, enrofloxacin, tiamulin and lincomycin. The results obtained in the presented study demonstrated that animal feces can be used as a non-invasive method detection antibiotic usage in animal production.

Effect of tetracycline treatment regimens on antibiotic resistance gene selection over time in nursery pigs.

BACKGROUND: The majority of antimicrobials given during the production of pigs are given to nursery pigs. The influence of antimicrobial use on the levels of antimicrobial resistant (AMR) genes is important to quantify to be able to assess the impact of resistance on the food chain and risk to human and animal health. RESULTS: This study investigated the response on the levels of nine AMR genes to five different treatment strategies with oxytetracycline, and the dynamics of gene abundance over time by following 1167 pigs from five different farms in Denmark. The results showed no significant difference between treatments and an increase in abundance for the efflux pump encoding tet(A) gene and the genes encoding the ribosomal protection proteins tet(O) and tet(W) tetracycline resistant genes following treatment, while tet(M) showed no response to treatment. However, it was also observed that the levels of tet(O), tet(W), and ermB in some farms would drift more over time compared to a single treatment-course with antibiotic. CONCLUSION: This study underlines the large variation in AMR levels under natural conditions and the need for increased investigation of the complex interactions of antimicrobial treatment and other environmental and managerial practices in swine production on AMR gene abundance.

Evaluation of new generation macrolides for the treatment and metaphylaxis of contagious bovine pleuropneumonia (CBPP) in cattle experimentally infected with Mycoplasma mycoides subspecies mycoides.

BACKGROUND: Contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subspecies mycoides (Mmm) is an important disease of cattle that causes serious economic losses. With the known effectiveness of new generation macrolides, tulathromycin and gamithromycin were assessed in comparison with oxytetracycline as a positive control and saline as a negative control for effectiveness in inhibiting lung lesion development, promoting resolution, preventing spread and bacteriological clearance in susceptible local cattle breeds in two separate studies in Kenya and Zambia. Animals were monitored for clinical signs, sero-conversion as well as detailed post-mortem examination for CBPP lesions. RESULTS: Using the Hudson and Turner score for lesion type and size, tulathromycin protected 90%, gamithromycin 80%, and oxytetracycline 88% of treated animals in Kenya. In Zambia, all animals (100%) treated with macrolides were free of lung lesions, while oxytetracycline protected 77.5%. Using the mean adapted Hudson and Turner score, which includes clinical signs, post-mortem findings and serology, tulathromycin protected 82%, gamithromycin 56% and oxytetracycline 80% of the animals in Kenya whereas in Zambia, tulathromycin protected 98%, gamithromycin 94% and oxytetracycline 80%. The saline-treated groups had 93 and 92% lesions in Kenya and Zambia respectively, with Mmm recovered from 5/14 in Kenya and 10/13 animals in Zambia. Whereas the groups treated with macrolides were free from lesions in Zambia, in Kenya 5/15 tulathromycin-treated animals and 6/15 gamithromycin-treated animals showed lesions. Oxytetracycline-treated animals showed similarities with 3/14 and 4/15 showing lesions in Zambia and Kenya respectively and Mmm recovery from one animal in Kenya and six in Zambia. In both studies, lesion scores of saline-treated groups were significantly higher than those of the antibiotic treated groups (p < 0.001). In sentinel animals, CBPP lesions were detected and Mmm recovered from one and two animals mixed with the saline-treated groups in Kenya and Zambia respectively. CONCLUSIONS: This study demonstrated that tulathromycin, a mycoplasmacidal, can achieve metaphylactic protection of up to 80%, while non-recovery of Mmm from sentinels suggests macrolides effectiveness in preventing spread of Mmm. It is recommended that further studies are conducted to evaluate strategies comparing vaccination alone or combining vaccination and antibiotics to control or eradicate CBPP.

A vibriosis outbreak in the Pacific white shrimp, Litopenaeus vannamei reared in biofloc and clear seawater.

In May and June 2015, moderate and severe lesions were observed in Litopenaeus vannamei reared in clear seawater while, at the same time, lesions in shrimp reared in biofloc were considerably fewer. The signs of disease included anorexia, lethargy, melanization, expanded chromatophores, luminescence and necrotic areas in the uropods, suggesting a possible vibriosis. However, lesions observed in shrimp reared in biofloc disappeared after a certain time and without mortality in tanks, whereas mortality and severe signs continued to be observed in shrimp reared in clear seawater. To treat the possible vibriosis, oxytetracycline was administered only in clear seawater tanks, but the results were not successful. Bacterial cultures from hepatopancreas tissues of shrimp from both rearing systems confirmed a vibriosis outbreak only in the clear seawater system. Subsequently, Vibrio harveyi, Vibrio rotiferianus, Photobacterium sp. and Photobacterium damselae were identified from bacterial culture previously isolated for both rearing systems by molecular methods. Shewanella sp. was isolated and identified only in biofloc. To understand the possible pathogenicity and resistance mechanisms of the Vibiro strains for both rearing systems, pathogenicity (toxR) and oxytetracycline resistance-related genes (tet(B), tet(D), tet(G)) were determined. Although these genes were expressed for both rearing systems, biofloc proved to have the ability to control the development of the disease, in comparison to clear water, where the vibriosis was evident regardless of the administration of oxytetracycline as a treatment.

Comparative evaluation of different therapeutic protocols for contagious caprine pleuropneumonia in Himalayan Pashmina goats.

Therapeutic management of contagious caprine pleuroneumonia (CCPP) involves mostly the use of oxytetracycline followed by enrofloxacin and rarely tylosin. In many parts of the world including India, the former antibiotics are commonly available than the latter. Therefore, prolonged use of the same leads to the development of antibiotic resistance and decreased efficacy of drug. Besides, inflammatory and allergic pathogenesis of CCPP envisages combination therapy. In this study, we evaluated the effectiveness of the combination therapy using different antibiotics (oxytetracycyline @ 10: group I, enrofloxacin @ 5 group II, and tylosin: group III, @ 10 mg/kg body weight), along with anti-inflammatory (meloxicam @ 0.5 mg/kg) and anti-allergic (pheneramine maleate @ 1.0 mg/kg) drugs. These drugs were given intramuscularly at the interval of 48 h for four times in three test groups (n = 10) of Pashmina goats, viz. groups I, II, and III, respectively, affected with CCPP. Group IV (n = 10) was kept as healthy control when group V (n = 10) treated with oxytetracycline @ 10 mg/kg alone was used as positive control. Clinical signs, clinical parameters, pro-inflammatory cytokine (tumor necrosis factor alpha (TNF-α)), and oxidative stress indices (total oxidant status (TOS), total antioxidant status (TAS)) were evaluated at hours 0, 48, 96, and 144 of experimental trial. Tylosin-based combination therapy resulted in a rapid and favorable recovery resulting in restoration of normal body temperature (102.46 ± 0.31 °F), respiration rate (16.30 ± 0.79 per minute), and heart rate (89.50 ± 2.63 per minute) compared to the oxytetracycline (102.95 ± 0.13, 21.30 ± 1.12, 86.00 ± 2.33, respectively) and enrofloxacin (102.97 ± 0.19, 21.00 ± 1.25, 90.00 ± 2.58, respectively) treated groups. By hour 144, all the groups showed restoration of clinical parameters of normal health and diminishing signs of CCPP, viz. fever, dyspnea, coughing, nasal discharge, weakness, and pleurodynia. Significant (P ≤ 0.05) decrease in levels of TNF-α and non-significant (P > 0.05) decrease in levels of TOS and an increase in levels of TAS were noted from hour 0 to 144 in all the test groups. Within the groups, no significant (P > 0.05) change was noted in TNF-α, TOS, and TAS levels; however, TNF-α levels were comparatively lower in group III. Hematological parameters did not differ significantly (P > 0.05). From these findings, it can be inferred that tylosin-based combination therapy is relatively better for early, rapid, and safe recovery besides minimizing inflammatory and oxidative cascade in CCPP affected Pashmina goats compared to oxytetracycline- and enrofloxacin-based therapies.

Antibiotic susceptibility profiles of Mycoplasma synoviae strains originating from Central and Eastern Europe.

BACKGROUND: Mycoplasma synoviae causes infectious synovitis and respiratory diseases in chickens and turkeys and may lead to egg shell apex abnormalities in chickens; hence possesses high economic impact on the poultry industry. Control of the disease consists of eradication, vaccination or medication. The aim of the present study was to determine the in vitro susceptibility to 14 different antibiotics and an antibiotic combination of M. synoviae strains originating from Hungary and other countries of Central and Eastern Europe. RESULTS: Minimal inhibitory concentration (MIC) values of a total of 41 M. synoviae strains were determined by the microbroth dilution method. The strains were collected between 2002 and 2016 and originated from Hungary (n = 26), Austria (n = 3), the Czech Republic (n = 3), Slovenia (n = 3), Ukraine (n = 3), Russia (n = 2) and Serbia (n = 1). Tetracyclines (with MIC50 values of 0.078 µg/ml, ≤0.25 µg/ml and 0.5 µg/ml for doxycycline, oxytetracycline and chlortetracycline, respectively), macrolides (with MIC50 values of ≤0.25 µg/ml for tylvalosin, tylosin and tilmicosin), pleuromutilins (with MIC50 values of 0.078 µg/ml and ≤0.039 µg/ml for tiamulin and valnemulin) and the combination of lincomycin and spectinomycin (MIC50 1 µg/ml (0.333/0.667 µg/ml)) were found to be the most effective antibiotic agents against M. synoviae in vitro. High MIC values were detected in numerous strains for fluoroquinolones (with MIC50 values of 1.25 µg/ml and 2.5 µg/ml for enrofloxacin and difloxacin), neomycin (MIC50 32 µg/ml), spectinomycin (MIC50 2 µg/ml), lincomycin (MIC50 0.5 µg/ml) and florfenicol (MIC50 4 µg/ml). Nevertheless, strains with elevated MIC values were detected for most of the applied antibiotics. CONCLUSIONS: In the medical control of M. synoviae infections the preliminary in vitro antibiotic susceptibility testing and the careful evaluation of the data are crucial. Based on the in vitro examinations doxycycline, oxytetracycline, tylvalosin, tylosin and pleuromutilins could be recommended for the therapy of M. synoviae infections in the region.

What is the true in vitro potency of oxytetracycline for the pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida?

The pharmacodynamics of oxytetracycline was determined for pig respiratory tract pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Indices of potency were determined for the following: (i) two matrices, broth and pig serum; (ii) five overlapping sets of twofold dilutions; and (iii) a high strength starting culture. For A. pleuropneumoniae, minimum inhibitory concentration (MIC) was similar for the two matrices, but for P. multocida, differences were marked and significantly different. MIC and minimum bactericidal concentration (MBC) serum: broth ratios for A. pleuropneumoniae were 0.83:1 and 1.22:1, respectively, and corresponding values for P. multocida were 22.0:1 and 7.34:1. For mutant prevention concentration (MPC) serum: broth ratios were 0.79:1 (A. pleuropneumoniae) and 20.9:1 (P. multocida). These ratios were corrected for serum protein binding to yield fraction unbound (fu) serum: broth MIC ratios of 0.24:1 (A. pleuropneumoniae) and 6.30:1 (P. multocida). Corresponding fu serum: broth ratios for MPC were almost identical, 0.23:1 and 6.08:1. These corrections for protein binding did not account for potency differences between serum and broth for either species; based on fu serum MICs, potency in serum was approximately fourfold greater than predicted for A. pleuropneumoniae and sixfold smaller than predicted for P. multocida. For both broth and serum and both bacterial species, MICs were also dependent on initial inoculum strength. The killing action of oxytetracycline had the characteristics of codependency for both A. pleuropneumoniae and P. multocida in both growth media. The in vitro potency of oxytetracycline in pig serum is likely to be closer to the in vivo plasma/serum concentration required for efficacy than potency estimated in broths.

Evaluation of long-acting oxytetracycline and a commercial monovalent vaccine for the control of Campylobacter fetus subsp. venerealis infection in beef bulls.

A blinded randomized controlled trial was used to evaluate a multi-modal therapeutic regime for treatment of beef bulls infected with Campylobacter fetus subsp. venerealis (Cfv). Treatment included 2 doses of a commercially available monovalent vaccine and long-acting oxytetracycline applied twice at a 2-week interval with treatment completed 2 weeks before post-treatment observation. Fifteen confirmed Cfv infected bulls were randomly allocated to control (n = 8) or treatment groups (n = 7). Preputial scrapings were collected each week from before infection to 11 weeks following the last treatment. When the polymerase chain reaction (PCR) results for both culture and preputial scrapings were interpreted in parallel, there were no significant differences between treated and untreated bulls. Regardless of the type of diagnostic testing considered, treatment with 2 label doses of this regime did not stop shedding of Cfv in all treated bulls and is, therefore, not recommended as an effective management strategy.

Évaluation de l'oxytétracycline d'action prolongée et d'un vaccin monovalent commercial pour maîtriser l'infection parCampylobacter fetusssp.venerealischez les taureaux de boucherie. Un essai clinique randomisé à l'insu a été utilisé pour évaluer un régime thérapeutique multimodal pour le traitement des taureaux de boucherie infectés par Campylobacter fetus ssp. venerealis (Cfv). Le traitement a inclus deux doses d'un vaccin monovalent disponible dans le commerce et de l'oxytétracycline d'action prolongée appliquée deux fois à un intervalle de 2 semaines et le traitement a été complété deux semaines avant l'observation post-traitement. Quinze taureaux présentant une infection confirmée par Cfv ont été assignés au hasard au groupe témoin (n = 8) ou au groupe de traitement (n = 7). Des grattages de la surface du prépuce ont été prélevés à chaque semaine à partir du moment avant l'infection jusqu'à 11 semaines suite au dernier traitement. Lorsque les résultats de l'amplification en chaîne par polymérase (ACP) pour les cultures et les biopsies de surface du prépuce ont été interprétés en parallèle, il n'y avait aucune différence significative entre les taureaux traités et les taureaux non traités. Sans égard au type de test diagnostique considéré, le traitement à l'aide de deux doses recommandées sur l'étiquette n'a pas freiné l'excrétion de Cfv chez tous les taureaux traités et n'est donc pas recommandé comme une stratégie de gestion efficace.(Traduit par Isabelle Vallières).

CLINICAL DISEASE ASSOCIATED WITH ANAPLASMA PHAGOCYTOPHILUM INFECTION IN CAPTIVE PRZEWALSKI'S HORSES (EQUUS FERUS PRZEWALSKII).

Anaplasma phagocytophilum is a tick-borne pathogen of domestic horses and the causative agent of equine granulocytic anaplasmosis. This case series describes three confirmed cases of clinical anaplasmosis, and a fourth case of presumptive anaplasmosis in Przewalski's horses ( Equus ferus przewalskii) housed at the Smithsonian Conservation Biology Institute from 2008 to 2014. Clinical signs varied among individuals with affected horses exhibiting lethargy, weakness, pyrexia, hypophagia, reluctance to move, or ataxia. Anaplasmosis cases were confirmed with a combination of identification of neutrophilic inclusions (morulae) on peripheral blood smear, positive polymerase chain reaction (PCR) testing of whole blood, or convalescent titers. All animals recovered after antimicrobial therapy with oxytetracycline. Diagnosis should be made by a combination of clinical signs plus identification of morulae or positive A. phagocytophilum PCR. Treatment is curative using oxytetracyline intramuscularly or intravenously followed by daily therapy with oxytetracyline or minocycline for 14-30 days. The authors recommend that A. phagocytophilum infection be included on any differential list for Przewalski's horses presenting with fever or ataxia within or near an enzootic area.

Soil-borne reservoirs of antibiotic-resistant bacteria are established following therapeutic treatment of dairy calves.

We determined if antibiotics residues that are excreted from treated animals can contribute to persistence of resistant bacteria in agricultural environments. Administration of ceftiofur, a third-generation cephalosporin, resulted in a ∼ 3 log increase in ceftiofur-resistant Escherichia coli found in the faeces and pen soils by day 10 (P = 0.005). This resistant population quickly subsided in faeces, but was sustained in the pen soil (∼ 4.5 log bacteria g(-1)) throughout the trial (1 month). Florfenicol treatment resulted in a similar pattern although the loss of florfenicol-resistant E. coli was slower for faeces and remained stable at ∼ 6 log bacteria g(-1) in the soil. Calves were treated in pens where eGFP-labelled E. coli were present in the bedding (∼ 2 log g(-1)) resulting in amplification of the eGFP E. coli population ∼ 2.1 log more than eGFP E. coli populations in pens with untreated calves (day 4; P < 0.005). Excreted residues accounted for > 10-fold greater contribution to the bedding reservoir compared with shedding of resistant bacteria in faeces. Treatment with therapeutic doses of ceftiofur or florfenicol resulted in 2-3 log g(-1) more bacteria than the estimated ID50 (2.83 CFU g(-1)), consistent with a soil-borne reservoir emerging after antibiotic treatment that can contribute to the long-term persistence of antibiotic resistance in animal agriculture.