BACKGROUND: Colibacillosis in broiler chickens is associated with economic loss and localized or systemic infection. Usually, the last resort is antibacterial therapy. Insight into the disease pathogenesis, host responses and plausible immunomodulatory effects of the antibacterials is important in choosing antibacterial agent and optimization of the treatment. Selected responses of broiler chickens experimentally infected with Escherichia coli (E. coli) and also those treated with florfenicol are evaluated in this study. Chickens (n = 70, 5 weeks old) were randomly assigned to four groups. The control groups included normal control (NC) and intratracheal infection control (ITC) (received sterile bacterial medium). The experimental groups consisted of intratracheal infection (IT) that received bacterial suspension and intratracheal infection with florfenicol administration (ITF) group.
RESULTS: Florfenicol reversed the decreased albumin/globulin ratio to the level of control groups (p > 0.05). Serum interleukin 10 (IL-10) and interferon-gamma (IFN-γ) concentrations decreased in IT birds as compared to NC group. Florfenicol decreased the serum interleukin 6 (IL-6) concentration as compared to IT group. Milder signs of inflammation, septicemia, and left shift were observed in the leukogram of the ITF group. Florfenicol decreased the severity of histopathological lesions in lungs and liver. Depletion of lymphoid tissue was detected in spleen, thymus and bursa of IT group but was absent in ITF birds. The number of colony forming units of E. coli in liver samples of ITF group was only slightly lower than IT birds.
CONCLUSIONS: Experimental E. coli infection of chickens by intratracheal route is associated with remarkable inflammatory responses as shown by changes in biochemical and hematological parameters. Histopathological lesions in lymphoid organs (especially in the spleen) were also prominent. Florfenicol has positive immunomodulatory effects and improves many of the lesions before the full manifestation of its antibacterial effects. These effects of florfenicol should be considered in pharmacotherapy decision-making process.

Knowledge on the characteristics of different infection models of avian colibacillosis is mandatory for performing reliable experimental studies. This study compares the characteristics of two infection models of colibacillosis (by intratracheal and subcutaneous routes) in broilers. Broilers (125), 35 days old, were randomly allocated to four experimental (n = 20) and three control (n = 15) groups: 1) negative control; 2) intratracheal infection control; 3) subcutaneous infection control; 4) intratracheal infection (IT); 5) intratracheal infection with florfenicol administration (ITF); 6) subcutaneous infection (SC); and 7) subcutaneous infection with florfenicol administration (SCF). Clinical signs and mortalities were recorded, and gross examination of carcasses was performed. On days 3 and 5 postchallenge (PC), 5 birds/group were euthanatized. Despite similar onset and type of clinical signs and mortality of birds in the IT and SC groups, especially on early days PC, birds in the SC group had lower body weight than IT birds. Lung injuries were more prominent in the IT group than the SC group. Birds of the SC group showed cellulitis and severely injured kidneys in contrast to the IT group. On day 3 PC, the number of positive heart blood samples for bacterial growth in the ITF group was half that of the IT group, whereas SC and SCF birds had similar positive numbers. Infection by the subcutaneous route results in more severe disease. The intratracheal route produces results more similar to colibacillosis under field conditions with regard to clinical signs, pathogenesis, and response to therapy, albeit it is more difficult to perform than a subcutaneous challenge.
Un estudio comparativo sobre dos modelos de infección de colibacilosis en pollos de engorde: Características clínicas, patogénesis y respuesta a la terapia. El conocimiento de las características de los diferentes modelos de infección de colibacilosis aviar es necesario para realizar estudios experimentales confiables. Este estudio compara las características de dos modelos de infección de colibacilosis (por vía intratraqueal y por vía subcutánea) en pollos de engorde. Pollos de engorde (n = 125), de 35 días de edad, se asignaron aleatoriamente a cuatro grupos experimentales (n = 20) y tres controles (n = 15): 1) control negativo (NC), y grupos 2 y 3) controles de infección intratraqueal o subcutánea (ITC o SCC), 4) infección intratraqueal (IT), 5) infección intratraqueal con administración de florfenicol (ITF), 6) infección subcutánea (SC), y 7) infección subcutánea con administración de florfenicol (SCF). Se registraron los signos clínicos y la mortalidad, y se realizó un examen macroscópico de las canales. En los días tres y cinco posteriores a la exposición (PC), se sacrificaron 5 aves por grupo. A pesar de que fueron similares el inicio y tipo de signos clínicos y la mortalidad en las aves de los grupos inoculados por infección intratraqueal y subcutánea, especialmente en los primeros días después del desafío, las aves de los grupos inoculado por vía subcutánea tenían un peso corporal más bajo que las aves inoculadas por la vía intratraqueal. Las lesiones pulmonares fueron más prominentes en el grupo inoculado por vía intratraqueal que en el grupo inoculado por vía subcutánea. Las aves del grupo inoculado por vía subcutánea mostraron celulitis y riñones severamente lesionados en contraste con el grupo inoculado por vía intratraqueal. En el día tres después del desafío, el número de muestras de sangre del corazón positivas para crecimiento bacteriano en el grupo con infección intratraqueal y con administración de florfenicol fue la mitad que en el grupo inoculado intratraquealmente, mientras que las aves inoculadas por vía subcutánea e inoculadas subcutáneamente con administración de florfenicol tuvieron números positivos similares. En conclusión, la infección por vía subcutánea resulta en una enfermedad más severa. La vía intratraqueal produce resultados más similares a la colibacilosis en condiciones de campo con respecto a los signos clínicos, la patogenia y la respuesta a la terapia, aunque es más difícil de realizar que un desafío subcutáneo.

The intensification of production practices in the aquaculture industry has led to the indiscriminate use of antibiotics to combat diseases and reduce costs, which has resulted in environmental pollution, posing serious threats to aquaculture sustainability and food safety. However, the toxic effect of florfenicol (FF) exposure on the hepatopancreas of crustaceans remains unclear. Herein, by employing Chinese mitten crab (Eriocheir sinensis) as subjects to investigate the toxic effects on histopathology, oxidative stress, apoptosis and microbiota of hepatopancreas under environment-relevant (0.5 and 5 μg/L), and extreme concentrations (50 μg/L) of FF. Our results revealed that the damage of hepatopancreas tissue structure caused by FF exposure in a dose-and time-dependent manner. Combined with the increased expression of apoptosis-related genes (Caspase 3, Caspase 8, p53, Bax and Bcl-2) at mRNA and protein levels, activation of catalase (CAT) and superoxide dismutase (SOD), and malondialdehyde (MDA) accumulation, FF exposure also induced oxidative stress, and apoptosis in hepatopancreas. Interestingly, 7 days exposure triggered more pronounced toxic effect in crabs than 14 days under environment-relevant FF concentration. Integrated biomarker response version 2 (IBRv2) index indicated that 14 days FF exposure under extreme concentration has serious toxicity effect on crabs. Furthermore, 14 days exposure to FF changed the diversity and composition of hepatopancreas microbiota leading remarkable increase of pathogenic microorganism Spirochaetes following exposure to 50 μg/L of FF. Taken together, our study explained potential mechanism of FF toxicity on hepatopancreas of crustaceans, and provided a reference for the concentration of FF to be used in culture of Chinese mitten crab.

The objective of this study was to synthesize and characterize pharmaceutical characteristics of florfenicol sustained-release granules (FSRGs) in vitro and in vivo. FSRGs were synthesized using monostearate, polyethylene glycol 4000 and starch. In vitro dissolution profiles were studied using the rotating basket method in pH 1.2 HCl solution and pH 4.3 acetate buffer. Twenty-four male healthy Landrace×Yorkshire pigs were equally divided into three groups and administered a 20 mg/kg i.v bolus of florfenicol solution and dosed orally with FSRGs in the fasting and fed states. The Higuchi model was the best fit for the drug release profile in pH 1.2 and pH 4.3 media, and the mechanism of drug dissolution was governed by both diffusion and dissolution. We established a level A in vitro - in vivo correlation for FSRGs and the in vivo profile of the FSRGs can be estimated by the in vitro drug release.

Violative chemical residues in edible tissues from food-producing animals are of global public health concern. Great efforts have been made to develop physiologically based pharmacokinetic (PBPK) models for estimating withdrawal intervals (WDIs) for extralabel prescribed drugs in food animals. Existing models are insufficient to address the food safety concern as these models are either limited to 1 specific drug or difficult to be used by non-modelers. This study aimed to develop a user-friendly generic PBPK platform that can predict tissue residues and estimate WDIs for multiple drugs including flunixin, florfenicol, and penicillin G in cattle and swine. Mechanism-based in silico methods were used to predict tissue/plasma partition coefficients and the models were calibrated and evaluated with pharmacokinetic data from Food Animal Residue Avoidance Databank (FARAD). Results showed that model predictions were, in general, within a 2-fold factor of experimental data for all 3 drugs in both species. Following extralabel administration and respective U.S. FDA-approved tolerances, predicted WDIs for both cattle and swine were close to or slightly longer than FDA-approved label withdrawal times (eg, predicted 8, 28, and 7 days vs labeled 4, 28, and 4 days for flunixin, florfenicol, and penicillin G in cattle, respectively). The final model was converted to a web-based interactive generic PBPK platform. This PBPK platform serves as a user-friendly quantitative tool for real-time predictions of WDIs for flunixin, florfenicol, and penicillin G following FDA-approved label or extralabel use in both cattle and swine, and provides a basis for extrapolating to other drugs and species.

Florfenicol is a broad spectrum antibacterial, licensed globally for treatment of animal and aquaculture diseases. In the EU, Canada and US it is not permitted for use in animals producing milk or eggs. There are no published methods for analysis of total florfenicol content in milk/milk products as these lack a hydrolysis step, failing to meet the marker residue definition. A method for determining total florfenicol content in milk that meets this definition is reported for the first time. Use of a UHPLC-MS/MS multiple reaction monitoring-cubed method improved the selective detection and quantitation of lower levels of florfenicol amine in milk compared to MRM only. Single laboratory validation data and withdrawal profile in bovine milk are presented. A withdrawal period of over 50 days is indicated in case of off-label use. Requirement for hydrolysis is demonstrated.

BACKGROUND: Respiratory infections are the main indication for antimicrobial use in calves. Optimal treatment duration currently is unknown, but shorter duration would likely decrease selection for antimicrobial resistance.
OBJECTIVE: Determine differences in cure rate and healing time between animals treated with florfenicol and oxytetracycline in a natural outbreak of respiratory disease using reaeration observed on thoracic ultrasound examination as healing criterion.
METHODS: Commercial farm housing 130, 3 to 9 month old Belgian blue beef calves.
METHODS: Randomized clinical trial during an outbreak of respiratory disease. Metaphylactic treatment was initiated, randomly treating animals with either florfenicol or oxytetracycline. Ultrasonographic follow-up was done the first day and every other day for a 14-day period. At the individual animal level, treatment was discontinued when reaeration of the lungs occurred. Differences in cure rate and healing time were determined.
RESULTS: Of the 130 animals studied, 67.7% developed a lung consolidation ≥0.5 cm. The mean ultrasonographic healing time was 2.5 days in the florfenicol group compared to 3.1 days in the oxytetracycline group (P = .04). After single treatment, 80.6% and 60.3% had no consolidations in the florfenicol and oxytetracycline groups, respectively (P = .01). A Mycoplasma bovis strain was genetically and phenotypically determined to be susceptible to both antimicrobials.
CONCLUSIONS: Ultrasonographic lung reaeration shows potential as a cure criterion to rationalize antimicrobial use for outbreaks of pneumonia. In our study, florfenicol resulted in a faster cure and higher reduction in antimicrobial usage than did oxytetracycline.

In order to explore the transcriptomics and proteomics targets and pathways of Salvia miltiorrhiza polysaccharides (SMPs) alleviating florfenicol (FFC)-induced liver injury in broilers, 60 1-day-old broilers were randomly divided into 3 groups: control group ( GP1) was fed tap water, FFC model (GP2) was given tap water containing FFC 0.15 g/L, and SMPs treatment group (GP3) was given tap water containing FFC 0.15 g/L and SMPs 5 g/L. Starting from 1 day of age, the drug was administered continuously for 5 days. On the 6th day, blood was collected from the heart and the liver was taken. Then 3 chickens were randomly taken from each group, and their liver tissues were aseptically removed and placed in an enzyme-free tube. Using high-throughput mRNA sequencing and TMT-labeled quantitative proteomics technology, the transcriptome and proteome of the three groups of broiler liver were analyzed, respectively. The results of the study showed that the liver tissue morphology of the chicks in the GP1 and GP3 groups was complete and there were no obvious necrotic cells in the liver cells. The liver tissue cells in the GP2 group showed obvious damage, the intercellular space increased, and the liver cells showed extensive vacuolation and steatosis. Compared with the GP1 group, the daily gain of chicks in the GP2 group was significantly reduced (P < 0.0 5 or P < 0.01). Compared with the GP2 group, the GP3 group significantly increased the daily gain of chicks (P <0.0 5 or P <0.01). Compared with the GP1 group, the serum levels of ALT, AST, liver LPO, ROS, and IL-6 in the GP2 group were significantly increased (P < 0.0 5 or P < 0.01), and the contents of T-AOC, GSH-PX, IL-4, and IL-10 in the liver were significantly decreased (P < 0.0 5 or P < 0.01). After SMPs treatment, the serum levels of ALT, AST, liver LPO, ROS, and IL-6 were significantly reduced (P < 0.0 5 or P < 0.01), and the contents of T-AOC, GSH-PX, IL-4, and IL-10 in the liver were significantly increased (P < 0.0 5 or P < 0.01). There were 380 mRNA and 178 protein differentially expressed between GP2 group and GP3 group. Part of DEGs was randomly selected for QPCR verification, and the expression results of randomly selected FABP1, SLC16A1, GPT2, AACS, and other genes were verified by QPCR to be consistent with the sequencing results, which demonstrated the accuracy of transcriptation-associated proteomics sequencing. The results showed that SMPs could alleviate the oxidative stress and inflammatory damage caused by FFC in the liver of chicken and restore the normal function of the liver. SMPs may alleviate the liver damage caused by FFC by regulating the drug metabolism-cytochrome P450, PPAR signaling pathway, MAPK signaling pathway, glutathione metabolism, and other pathways.

OBJECTIVE: In Egypt, Nile tilapia represents the main cultured type due to its economical price, palatability and easy culturing. This study was aimed to elucidate the pathogenicity of V. alginolyticus isolated from diseased sea bass and experimentally infected healthy Nile tilapia fish.
METHODS: Healthy Nile tilapia fish were injected I/P with V. alginolyticus isolated from diseased sea bass. Symptoms and mortality rates of infected Nile tilapia fish were recorded during the experimental period. Re-isolation of V. alginolyticus was done from infected tilapia fish by bacteriological methods. For confirmation the pathogenicity of Vibrio isolated either from marine fish or tilapia fish, PCR test was done using tdh and bla gens. Liver and kidney function tests with histopathological examinations of some organs were performed. Treatment trial was done according to the antibiotic sensitivity test.
RESULTS: The isolated Vibrio is highly pathogenic to Nile tilapia fish causing deterioration in all parameters which finished by severe mortalities. Treatment with florfenicol, enrofloxacin, or oxytetracycline reduced the mortality rate and improved liver and kidney function parameters of infected Nile tilapia fish.
CONCLUSIONS: V. alginolyticus can infect both marine and fresh water fish inducing a high mortality rate. Treatment of infected fish with florfenicol, enrofloxacin, or oxytetracycline reduces the mortality rate.

This study evaluated changes in cutaneous mucosal immunity (total protein (TP) and immunoglobulin (TIg), lysozyme, protease, esterase, and alkaline phosphatase (ALP)) and some immune-related genes expression (tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-8, hepcidin-like antimicrobial peptides (HAMP), and immunoglobulin M (IgM)) in the intestine of rainbow trout (Oncorhynchus mykiss) orally-administrated florfenicol (FFC) and/or olive leaf extract (OLE), experimentally infected with Streptococcus iniae. The juvenile fish (55 ± 7.6 g) were divided into different groups according to the use of added OLE (80 g kg-1 food), the presence/absence of FFC (15 mg kg-1 body weight for 10 consecutive days), and the streptococcal infectivity (2.87 × 107 CFU mL-1 as 30% of LD50-96h). The extract\'s chemical composition was analyzed using the high-performance liquid chromatography (HPLC) system. The skin mucus and intestine of fish were sampled after a 10-day therapeutic period for all groups, and their noted indices were measured. Our results signified that the oleuropein, quercetin, and trans-ferulic acid were the most obvious active components of OLE which were found by HPLC analysis. The combined use of OLE and FFC could lowered some skin mucus immunological indices (e.g., TP, TIg, and ALP), and the gene expression of inflammatory cytokines (e.g., TNF-α and IL-1β) of rainbow trout. Moreover, lysozyme and protease activities respectively were invigorated by the FFC and OLE treatment. Also, the use of OLE as a potential medicine induced the gene expression of HAMP. As the prevention approach, it would be recommended to find the best dose of OLE alone or in combination with the drug through therapeutics period before the farm involved in the streptococcal infection.