Surveillance assessment for veterinary biocidal products in Korea: A laboratory investigation.

Veterinary biocides used in animal husbandry have the potential to cause human health concerns. Biocidal products for veterinary use, which contain pesticides approved in Korea, comprise 49 active ingredients within 234 products. Within 17 of these products there are 3 ingredients which are highly hazardous pesticides: coumaphos, dichlorvos and methomyl. In this study, the content of the active ingredients of 160 products sold domestically was investigated. Samples were collected for 119 biocidal products for veterinary use. These were analysed by high-performance liquid chromatography (HPLC) and gas chromatography (GC). Seventeen products were noncompliant (insufficient or excess quantity of active ingredients). The ingredients that were below the stated concentrations were amitraz, chlorpyrifos-methyl, cypermethrin, cyromazine, dichlorvos, fipronil, muscamone and trichlorfon. The ingredients that exceeded the stated concentrations were abamectin, fluvalinate and pyriproxyfen. The noncompliance rate in biocidal products for veterinary use was 9.19%. The results of this study show that three highly hazardous pesticides (coumaphos, dichlorvos and methomyl) and 10 active ingredients (abamectin, amitraz, chlorpyrifos-methyl, cypermethrin, cyromazine, fipronil, fluvalinate, muscamone, pyriproxyfen and trichlorfon) deviated from the stated concentrations. Thus, management plans should be established to ensure compliant veterinary drugs by post-distribution quality control, such as planning for regular inspection.

Antimicrobial Susceptibility and Association with Toxin Determinants in Clostridium perfringens Isolates from Chickens.

The aim of the present study was to investigate variation in antimicrobial resistance in Clostridium perfringens (C. perfringens) isolated from chickens after withdrawal of antimicrobial growth promoters (AGPs); and to investigate the correlation between the presence of toxin genes (cpb2, netB, and tpeL) and antimicrobial resistance. Altogether, 162 isolates of C. perfringens were obtained from chickens displaying clinical signs of necrotic enteritis (n = 65) and from healthy chickens (n = 97) in Korea during 2010-2016. Compared to before AGP withdrawal, increased antimicrobial resistance or MIC50/MIC90 value was observed for nine antimicrobials including penicillin, tetracycline, tylosin, erythromycin, florfenicol, enrofloxacin, monensin, salinomycin, and maduramycin. Significantly (p < 0.05) higher resistance to gentamicin, clindamycin, and virginiamycin was found in isolates from chickens with necrotic enteritis compared to those from healthy chickens. tpeL gene was not detected in C. perfringens isolates from healthy chickens. A correlation between toxin gene prevalence and antibiotic resistance was found in the C. perfringens isolates. Because the usage of antimicrobials may contribute to the selection of both resistance and toxin genes, these can potentially make it challenging to control antimicrobial resistance in pathogenic colonies. Therefore, a more complete understanding of the interplay between resistance and virulence genes is required.

In vitro synergistic potentials of novel antibacterial combination therapies against Salmonella enterica serovar Typhimurium.

BACKGROUND: The antibiotics generally used in farm animals are rapidly losing their effectiveness all over the world as bacteria develop antibiotic resistance. Like some other pathogenic bacteria multidrug-resistant strains of Salmonella enterica serovar Typhimurium (S. Typhimurium) are also frequently found in animals and humans which poses a major public health concern. New strategies are needed to block the development of resistance and to prolong the life of traditional antibiotics. Thus, this study aimed to increase the efficacy of existing antibiotics against S. Typhimurium by combining them with opportunistic phenolic compounds gallic acid (GA), epicatechin, epicatechin gallate, epigallocatechin and hamamelitannin. Fractional inhibitory concentration indexes (FICI) of phenolic compound-antibiotic combinations against S. Typhimurium were determined. Based on the FICI and clinical importance, 1 combination (GA and ceftiofur) was selected for evaluating its effects on the virulence factors of this bacterium. Viability of Rattus norvegicus (IEC-6) cell in presence of this antibacterial combination was evaluated. RESULTS: Minimum inhibitory concentrations (MICs) of GA, epigallocatechin and hamamelitannin found against different strains of S. Typhimurium were 256, (512-1024), and (512-1024) µg/mL, respectively. Synergistic antibacterial effect was obtained from the combination of erythromycin-epicatechin gallate (FICI: 0.50) against S. Typhimurium. Moreover, additive effects (FICI: 0.502-0.750) were obtained from 16 combinations against this bacterium. The time-kill assay and ultrastructural morphology showed that GA-ceftiofur combination more efficiently inhibited the growth of S. Typhimurium compared to individual antimicrobials. Biofilm viability, and swimming and swarming motilities of S. Typhimurium in presence of GA-ceftiofur combination were more competently inhibited than individual antimicrobials. Viabilities of IEC-6 cells were more significantly enhanced by GA-ceftiofur combinations than these antibacterials alone. CONCLUSIONS: This study suggests that GA-ceftiofur combination can be potential medication to treat S. Typhimurium-associated diarrhea and prevent S. Typhimurium-associated blood-stream infections (e.g.: fever) in farm animals, and ultimately its transmission from animal to human. Further in vivo study to confirm these effects and safety profiles in farm animal should be undertaken for establishing these combinations as medications.

Pharmacokinetic and pharmacodynamic integration of enrofloxacin against Salmonella Enteritidis after administering to broiler chicken by per-oral and intravenous routes.

It is crucial to optimize the dose of fluoroquinolones to avoid antibiotic resistance and to attain clinical success. We undertook this study to optimize the dose of enrofloxacin against Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) in chicken by assessing its pharmacokinetic/pharmacodynamic (PK/PD) indices. The antibacterial activities of enrofloxacin against S. Enteritidis were evaluated. After administering 10 mg/kg body weight (b.w.) of enrofloxacin to broiler chickens of both sexes by intravenous (IV) and peroral (PO) routes, blood samples were drawn at different intervals and enrofloxacin concentrations in plasma were determined. PK/PD indices were calculated by integrating the PK and PD data. The elimination half-lives (T1/2), time required to reach peak concentration (Tmax), peak concentration (Cmax), and area under curve (AUC) after administering enrofloxacin by PO and IV routes were 25.84 ± 1.40 h, 0.65 ± 0.12 h, 3.82 ± 0.59 µg/mL, and 20.84 ± 5.0 µg·h/mL, and 12.84 ± 1.4 h, 0.22 ± 0.1 h, 6.74 ± 0.03 µg/mL, and 21.13 ± 0.9 µg.h/mL, respectively. The bioavailability of enrofloxacin was 98.6% ± 8.9% after PO administration. The MICs of enrofloxacin were 0.0625-1 µg/mL against S. Enteritidis strains, and the MIC50 was 0.50 µg/mL. The Cmax/MIC50 were 7.64 ± 0.2 and 13.48 ± 0.7 and the 24 h AUC/MIC50 were 41.68 ± 0.1 and 42.26 ± 0.3 after administering the drug through PO and IV routes, respectively. The data in this study indicate that the application of 50 mg/kg b.w. of enrofloxacin to chicken through PO and IV routes with a dosing interval of 24 h can effectively cure S. Enteritidis infection, indicating the need for a 5-fold increase in the recommended dosage of enrofloxacin in chicken.

The phenotypic and molecular resistance induced by a single-exposure to sub-mutant prevention concentration of marbofloxacin in Salmonella Typhimurium isolates from swine.

In the present study, the molecular mechanisms of antibiotic resistance in Salmonella Typhimurium clinical isolates from pigs were investigated using a single-step mutation model of exposure to sub-mutant prevention concentrations (MPCs) of marbofloxacin. The minimum inhibitory concentrations (MICs) of seven antibacterial drugs were evaluated against 30 S. Typhimurium clinical isolates from different pigs. MPCs of marbofloxacin were also determined. The mechanism of marbofloxacin-resistance was investigated by sequencing analysis of target gene mutations and quantifying the overexpression of efflux pumps and their regulators by quantitative RT-PCR. Marbofloxacin showed the highest potency against all isolates (23.3%), including multi-drug resistant isolates. The MPC50 (0.5µg/mL) and MPC90 (2µg/mL) of marbofloxacin were determined, as were MPC/MIC ratios of 2.5 to 8. A gyrA mutation (Ser83Phe or Asp87His) was detected in isolates with an MIC>0.06µg/mL and all single-step mutants. Moreover, expression of acrAB-tolC and marA/soxS/ramA increased following a single-step mutation, but only ramA expression showed a positive correlation with the resistance phenotype of clinical isolates and single-step mutants (p<0.05). Furthermore, the acrR mutation was detected in two clinical isolates and 50% of single-step mutants, regardless of whether the gyrA mutation was present. This is the first report of acrR mutations in S. Typhimurium isolates from pigs in Korea. Our findings suggest that a single-exposure to sub-MPCs of marbofloxacin was sufficient to reduce the susceptibility of Salmonella isolates. Therefore, optimized dosing based on application with the MPC concept is required to reduce the chances of marbofloxacin resistance.

Pharmacokinetic and Pharmacodynamic Evaluation of Marbofloxacin in Pig against Korean Local Isolates of Actinobacillus pleuropneumoniae.

The pharmacokinetics of marbofloxacin in pigs after intravenous (i.v.), intramuscular (i.m.), and peroral (p.o.) administration and pharmacokinetic/pharmacodynamic indices of this drug against Korean local isolates of Actinobacillus pleuropneumoniae were determined in this study. Marbofloxacin (2.50 mg/kg of body weight) was administered, and blood samples were collected with designated time intervals. Plasma-extracted marbofloxacin was injected into the LC-MS/MS system. The in vitro and ex vivo antibacterial activities of marbofloxacin were evaluated against 20 isolates of A. pleuropneumoniae. The mean peak plasma concentrations (Cmax) after i.v., i.m., and p.o administration were 2.60 ± 0.10, 2.59 ± 0.12, and 2.34 ± 0.12 µg/mL at 0.25 ± 0.00, 0.44 ± 0.10, and 1.58 ± 0.40 h, respectively. The area under the plasma concentration-time curves (AUC0-24) and elimination half-lives were 24.80 ± 0.90, 25.80 ± 1.40, and 23.40 ± 5.00 h·µg/mL and 8.60 ± 0.30, 12.80 ± 1.10, and 8.60 ± 0.00 h, for i.v., i.m., and p.o. administration, correspondingly. The AUC0-24/MICs of marbofloxacin after i.v., i.m., and p.o. administration were 253.86 ± 179.91, 264.1 ± 187.16, and 239.53 ± 169.75 h, respectively. The Cmax/MIC values were 26.58 ± 18.84, 26.48 ± 18.77, and 23.94 ± 16.97, and T>MICs were 42.80 ± 1.01, 36.40 ± 1.24, and 38.60 ± 1.18 h, after i.v., i.m., and p.o. administration, respectively. Thus, marbofloxacin dosage of 2.50 mg/kg of body weight by i.v., i.m., and p.o. administration with 24 h dosing interval will provide effective treatment for the infection of pig by A. pleuropneumonia.

National post-market surveillance assessment of veterinary medicines in Korea during the past decade.

BACKGROUND: Veterinary medicines have been widely used for the prevention and treatment of diseases, growth promotion, and to promote feeding efficacy in livestock. As the veterinary medicine industry has steadily grown, it is crucial to set up a baseline for the quality of medicine as well as the insufficiency or excessiveness of the active ingredients in drug products to ensure the compliance, safety and efficacy of these medicines. Thus, the 10 years data of post-marketing quality control study was summarized to determine the rate and extent of non-compliance of these medicines and to establish baseline data for future quality control measures of veterinary medicine. RESULTS: In this study, 1650 drugs for veterinary use were collected per year from each city and province in Korea and analysed for the quantity of active ingredients according to the "national post-market surveillance (NPMS) system" over the past decade. The NPMS assessment was performed using liquid and gas chromatography, titration, UV/Vis spectrophotometry, and bioassays. A total of 358 cases were deemed noncompliant, with the average noncompliance rate for all medicine types being 2.0%. The average noncompliance rates for antibiotics, biologics and other chemical drugs except antibiotics (OCD) were 1.1%, 1.2%, and 3.0%, respectively. The first leading cause for noncompliant products was insufficient quantity of major ingredients (283 cases), and the second leading cause was the existence of excess amount of active ingredients (60 cases). Tylosin, spiramycin, ampicillin, tetracyclines and penicillins were most frequently found to be noncompliant among antibiotics. Among the OCD, the noncompliance was found commonly in vitamin A. CONCLUSION: The overall trend presented gradually decreasing violation rates, suggesting that the quality of veterinary medicines has improved. Consistent application of the NPMS assessment and the establishment of the Korea Veterinary Good Manufacturing Practice (KVGMP) will help to maintain the good quality of medicine.

Rapid determination of ß-lactam antimicrobial resistance in bacteria by a liquid chromatography-mass spectrometry-based method.

Conventional antimicrobial susceptibility tests (ASTs) are very time consuming and insufficiently precise to promptly select a proper antimicrobial treatment. This difficulty disrupts the management of infections and exacerbates the development of antimicrobial resistance. Generally, antimicrobial resistance involves the chemical modification of an antimicrobial compound to an inactive form by an enzyme released by bacteria. This modification causes a structural change and is followed by a characteristic mass shift of the antimicrobials. Using this mechanism, we developed a new liquid chromatography-mass spectrometry method to rapidly determine the degree of resistance of Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium), Escherichia coli, and Staphylococcus aureus to amoxicillin, ampicillin, and penicillin G, respectively. This method was successfully applied to 20 bacterial isolates from Korean slaughterhouses and farms. There were 18-Da mass shifts in resistant strains compared with susceptible strains of Salmonella Typhimurium, E. coli, and S. aureus, and the intensities of the hydrolyzed penicillin mass spectra were much higher in resistant strains than those in susceptible strains, which together indicate the reliability of this method. A comparison of the mass spectrometry-derived results with that from conventional ASTs revealed an identical classification of the tested bacteria according to sensitivity and resistance. Notably, this assay method requires only 2 h for determining the susceptibility status of a strain. This newly developed method is able to determine the extent of antimicrobial resistance qualitatively and quantitatively within a very short time and could be used to replace conventional AST methods. Graphical abstract Rapid determination of ß-lactam antimicrobial resistance in bacteria by LC-MS/MS.

Veterinary drug residues in domestic and imported foods of animal origin in the Republic of Korea.

The Korean National Residue Programme comprises three different approaches for evaluating domestic and imported foods of animal origin: monitoring, surveillance/enforcement and an exploratory test programme. Monitoring and surveillance/enforcement testing programmes are routinely implemented by 17 Provincial Veterinary Services for domestic products and regional offices of the Animal and Plant Quarantine Agency (QIA) for imported products. The exploratory project conducted at QIA headquarters is designed to test substances that are not included in monitoring and enforcement testing programmes. Here, we carried out exploratory testing for determining the presence of 42 veterinary drugs that have no established Korean maximum residue limits and analysed their levels simultaneously, in a total of 3108 samples of domestic and imported animal-origin foods. Of the tested drugs, acetylsalicylic, paracetamol, clopidol, diclazuril, amprolium, toltrazuril and its metabolites (toltrazuril sulphone and toltrazuril sulphoxide) and phenylbutazone and its metabolites (oxyphenylbutazone) were detected.

Multiresidue determination of ten nonsteroidal anti-inflammatory drugs in bovine, porcine, and chicken liver tissues by HPLC-MS/MS.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the group of drugs having the therapeutic efficacy of analgesic and antipyretic. To detect health-threatening residues of NSAIDs, a fast and easy multiresidue method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was described. Ten NSAIDs were extracted from the tissues using 2 mL of acetonitrile and 0.1 mL of 2 mM ammonium formate in distilled water. After clean-up using C18 sorbent, it was evaporated under nitrogen, reconstituted with 1 mL distilled water and analyzed by LC-MS/MS. The method was validated based on guideline for residue testing laboratory. Furthermore, the method has also been applied successfully to detect ten NSAIDs from bovine, porcine, and chicken liver tissues. In a total of 315 liver samples tested, acetylic salicylic acid was detected from 28 porcine and 2 chicken liver tissues at levels of 13 ∼ 576 and 50 ∼ 53 ng/g, respectively. Subsequently, paracetamol was detected in 15 porcine liver tissues with a detection levels of 28 ∼ 381 ng/g. Phenylbutazone and its metabolite, oxyphenylbutazone, were detected at 247 and 15 ng/g range in one of the bovine liver tissue, respectively.

Characterization and in vitro inhibition studies of Bacillus anthracis FtsZ: a potential antibacterial target.

FtsZ is an essential bacterial cell division protein that is an attractive target for the development of antibacterial agents. FtsZ is a homologue of eukaryotic tubulin, has GTPase activity, and forms a ring-type structure to initiate cell division. In this study, the FtsZ of Bacillus anthracis was cloned into a bacterial expression vector and overexpressed into Escherichia coli BL21 (DE3) cells. The overexpressed B. anthracis FtsZ was soluble and purified to homogeneity using Ni-His-tag affinity chromatography. Like other known FtsZs, the recombinant B. anthracis FtsZ also showed GTP-dependent polymerization, which was analyzed using both spectrophotometric and Transmission Electronic Microscopic (TEM) analysis. Using the purified FtsZ, we screened a naturally extracted chemical library to identify potent and novel inhibitors. The screening yielded three chemicals, SA-011, SA-059, and SA-069, that inhibited the in vitro polymerization activity of FtsZ in the micromolar range (IC50 of 55-168 µM). The inhibition potency was significantly comparable with that of berberine, a known potential inhibitor of FtsZ. Understanding the biochemical basis of the effect of these inhibitors on B. anthracis growth would provide a promising path for the development of new antianthracis drugs.

Quantitative analysis of eugenol in clove extract by a validated HPLC method.

Clove (Eugenia caryophyllata) is a well-known medicinal plant used for diarrhea, digestive disorders, or in antiseptics in Korea. Eugenol is the main active ingredient of clove and has been chosen as a marker compound for the chemical evaluation or QC of clove. This paper reports the development and validation of an HPLC-diode array detection (DAD) method for the determination of eugenol in clove. HPLC separation was accomplished on an XTerra RP18 column (250 x 4.6 mm id, 5 microm) with an isocratic mobile phase of 60% methanol and DAD at 280 nm. Calibration graphs were linear with very good correlation coefficients (r2 > 0.9999) from 12.5 to 1000 ng/mL. The LOD was 0.81 and the LOQ was 2.47 ng/mL. The method showed good intraday precision (%RSD 0.08-0.27%) and interday precision (%RSD 0.32-1.19%). The method was applied to the analysis of eugenol from clove cultivated in various countries (Indonesia, Singapore, and China). Quantitative analysis of the 15 clove samples showed that the content of eugenol varied significantly, ranging from 163 to 1049 ppb. The method of determination of eugenol by HPLC is accurate to evaluate the quality and safety assurance of clove, based on the results of this study.

Intracellular expression of cytokines and granzyme B in auricular lymph nodes draining skin exposed to irritants and sensitizers.

The murine local lymph node assay (LLNA) has been extensively utilized to evaluate sensitizing chemicals. However, there have been some concerns that its use to discriminate between classes of chemicals is minimal. It is thus desirable to identify better or alternative immune endpoints with in LLNA itself. Here, we evaluated the protein and/or mRNA levels of cytokines and granzyme B (GzmB), a cytotoxic lymphocyte product, to discriminate between sensitizers and irritants and to characterize the chemical sensitizers when used as supplemental indicators in LLNA endpoints. For this, CBA/N mice were topically treated daily with a well-known chemical sensitizer such as a strong contact sensitizer 1-chloro-2,4-dinitrobenzene (DNCB), a skin contact sensitizer 2-phenyl-4-ethoxymethylene-5-oxazolone (OXA), and a skin or respiratory sensitizer toluene 2,4-diisocyanate (TDI), and the non-sensitizing irritants, croton oil (CRO) and nonanoic acid (NA), for 3 consecutive days. The protein and/or mRNA levels in auricular lymph nodes draining the ear skin were then analyzed by real-time RT-PCR and immunoassay. The sensitizers, but not the irritants, evoked pronounced interleukin (IL)-2, IL-3 and IL-4 or interferon (IFN)-gamma. Significantly, different sensitizers evoked different cytokine patterns of IL-4 and IFN-gamma, as DNCB strongly up-regulated both IFN-gamma and IL-4, OXA up-regulated IFN-gamma strongly but IL-4 weakly, and TDI up-regulated IL-4 strongly but IFN-gamma weakly. The sensitizers also strongly up-regulated GzmB mRNA, while the irritants had a much weaker effect. Thus, these cytokines and GzmB mRNA may be useful as additional endpoints for discriminating between irritants and sensitizers or contact and respiratory sensitizers in the LLNA.