Antimicrobial Agents In Veterinary Medicine Research Articles

First Report of OXA-48 and IMP Genes Among Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolates from Diarrheic Calves in Tunisia.

Antimicrobial resistance is one of the most serious threats to human and animal health. Evidence suggests that the overuse of antimicrobial agents in animal production has led to the emergence and dissemination of multidrug-resistant isolates. The objective of this study was to assess the rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in calf feces and to characterize their resistance genes for antibiotics like beta-lactams and colistin, but also to determine their virulence genes. Fecal samples were collected from 100 diarrheic calves in the region of Bizerte, Tunisia. After isolation, E. coli isolates were screened for antimicrobial resistance against 21 antibiotics by the disc diffusion method. Characterization of β-lactamase genes and determination of associated resistance genes were performed by polymerase chain reaction. Among 71 E. coli isolates, 26 (36.6%) strains were ESBL-producing. Most of these isolates were multidrug-resistant (92.3%) and the most prevalent beta-lactamase genes detected were blaCTX-M (n = 26), blaSHV (n = 11), and blaTEM (n = 8), whereas only 1 isolate carried the blaCMY gene. In addition, resistance to carbapenems was detected in two isolates; one of them harbored both blaOXA-48 and blaIMP genes and the other isolate carried only the blaIMP gene. Several resistance genes were identified for the first time in Tunisia from cases of diarrheic calves. Furthermore, to the best of our knowledge, this is the first report of detection and identification of carbapenem resistance genes and virulence genes from calves in North Africa. A high occurrence of antimicrobial resistance of E. coli recovered from fecal samples of calves with diarrhea was observed, highlighting the need for prudent use of antimicrobial agents in veterinary medicine to decrease the incidence of multidrug-resistant bacteria for both animals and humans.

Gram-positive bacteriocins: usage as antimicrobial agents in veterinary medicine.

Antimicrobial resistance is a worldwide spread phenomenon that affects both human and veterinary medicine. This issue has led to a "One Health" approach in order to coordinate efforts and set back the development of drug-resistant microbes. In the search for alternatives therapies, bacteriocins or antimicrobial peptides have proven to be effective both in vitro and in vivo for multiples pathogens, even those resistant to many classic antibiotics. Gram-positive bacteriocins have been the most studied to the present. The use of bacteriocins as therapeutically active molecules is limited mainly due to difficulties in production, purification, delivery systems and regulatory approvals. To overcome some of these limitations, biotechnological and nanotechnological approaches are evaluated. Bacteriocins proved to be a good complement for conventional antibiotics therapy. Antimicrobial peptides are nowadays included in the veterinary products such as udder disinfectant for dairy cattle and dermatological medicated wipe for topical use on dogs, cats, and horses. But there are other potential uses to explore in the veterinary field for both companion and production animals.

Characterization, mechanism of action and optimization of activity of a novel peptide-peptoid hybrid against bacterial pathogens involved in canine skin infections

Integumentary infections like pyoderma represent the main reason for antimicrobial prescription in dogs. Staphylococcus pseudintermedius and Pseudomonas aeruginosa are frequently identified in these infections, and both bacteria are challenging to combat due to resistance. To avoid use of important human antibiotics for treatment of animal infections there is a pressing need for novel narrow-spectrum antimicrobial agents in veterinary medicine. Herein, we characterize the in vitro activity of the novel peptide-peptoid hybrid B1 against canine isolates of S. pseudintermedius and P. aeruginosa. B1 showed potent minimum inhibitory concentrations (MICs) against canine S. pseudintermedius and P. aeruginosa isolates as well rapid killing kinetics. B1 was found to disrupt the membrane integrity and affect cell-wall synthesis in methicillin-resistant S. pseudintermedius (MRSP). We generated 28 analogues of B1, showing comparable haemolysis and MICs against MRSP and P. aeruginosa. The most active analogues (23, 26) and B1 were tested against a collection of clinical isolates from canine, of which only B1 showed potent activity. Our best compound 26, displayed activity against P. aeruginosa and S. pseudintermedius, but not the closely related S. aureus. This work shows that design of target-specific veterinary antimicrobial agents is possible, even species within a genus, and deserves further exploration.

Antimicrobial Resistance in Escherichia coli.

Multidrug resistance in Escherichia coli has become a worrying issue that is increasingly observed in human but also in veterinary medicine worldwide. E. coli is intrinsically susceptible to almost all clinically relevant antimicrobial agents, but this bacterial species has a great capacity to accumulate resistance genes, mostly through horizontal gene transfer. The most problematic mechanisms in E. coli correspond to the acquisition of genes coding for extended-spectrum β-lactamases (conferring resistance to broad-spectrum cephalosporins), carbapenemases (conferring resistance to carbapenems), 16S rRNA methylases (conferring pan-resistance to aminoglycosides), plasmid-mediated quinolone resistance (PMQR) genes (conferring resistance to [fluoro]quinolones), and mcr genes (conferring resistance to polymyxins). Although the spread of carbapenemase genes has been mainly recognized in the human sector but poorly recognized in animals, colistin resistance in E. coli seems rather to be related to the use of colistin in veterinary medicine on a global scale. For the other resistance traits, their cross-transfer between the human and animal sectors still remains controversial even though genomic investigations indicate that extended-spectrum β-lactamase producers encountered in animals are distinct from those affecting humans. In addition, E. coli of animal origin often also show resistances to other-mostly older-antimicrobial agents, including tetracyclines, phenicols, sulfonamides, trimethoprim, and fosfomycin. Plasmids, especially multiresistance plasmids, but also other mobile genetic elements, such as transposons and gene cassettes in class 1 and class 2 integrons, seem to play a major role in the dissemination of resistance genes. Of note, coselection and persistence of resistances to critically important antimicrobial agents in human medicine also occurs through the massive use of antimicrobial agents in veterinary medicine, such as tetracyclines or sulfonamides, as long as all those determinants are located on the same genetic elements.

Use of fluoroquinolones in practice of veterinary medicine of Ukraine

Antibacterial agents are one of the most important groups of medical preparations in the treatment of bacterial infection of different localization in humane and in veterinary medicine. The consequence of their rational use (the establishment of sensitivity of the pathogenic microflora, compliance with the course of treatment, etc.) have a high therapeutic effect and the minimum development of resistant strains of microorganisms. The widely used group of antimicrobial agents in veterinary medicine are second-generation fluorohinolone antibiotics that have good pharmacokinetic properties, a broad spectrum of bactericidal activity, and relatively low toxicity, although they have their own warnings and restrictions on the use of small animals during the formation of bone tissue. To achieve high therapeutic efficacy and minimizing of side effects, it is described the compatibility of some fluoroquinolones with other pharmacological groups. They found their application in the treatment of both productive animals, poultry, fur animals and petty domestic (dogs and cats) with a bacterial infection of the urinary tract, digestive and respiratory systems, infected wounds, etc. The article describes the detailed mechanism of action of the antibiotics of the fluoroquinolone group, which provides an opportunity for a deeper understanding of the manifestation of the bactericidal effect, as well as their classification by generation or generation. Particular attention deserves attention to the time of carrenia of fluoroquinolones in the context of their application to productive animals, because high quality livestock products minimize the development of resistant strains in humans and provide them with health. There is also a list of all registered medicinal products registered in Ukraine containing: ofloxacin, enrofloxacin, ciprofloxacin, marbofloxacin, denofloxacin, which carries important informative information for practicing doctors, pharmacists, etc.

Critically important antimicrobial preparations for veterinary medicine

The resistance of microorganisms, bacterial pathogens, to antimicrobials is a global problem in both healthcare and veterinary medicine. It is believed that the main reason for the emergence and spread of antimicrobial resistance in humans is the transfer of antibiotic resistant strains of microorganisms or genes, determinants of resistance, through products of animal origin from productive animals to humans. Thus, the main way of antimicrobial resistance containment is to restrain and minimize it through the prudent use of antibiotics in veterinary medicine, especially those that are critically important for productive animals. In addition, some classes of antibacterial substances and antibiotics, that are widely used in humane medicine, are used in veterinary medicine. The need to use and preserve these important therapeutic agents is relevant from the point of view of the concept «One Health». The article provides a list of all antibacterial substances used by productive animals for their importance in veterinary medicine, developed by a special group of experts of the World Organisation for Animal Health (OIE). Any antimicrobial agent authorized for use in veterinary medicine for productive animals, in accordance with the criteria for quality, safety and efficacy as defined in Section 6.9 of the Terrestrial Animal Health Code, is considered to be important for veterinary medicine. All the antimicrobial substances used for productive animals are divided in this list on critical, very important and important for veterinary medicine. Attention was also drawn to the peculiarities of the use of critical antimicrobial agents in veterinary medicine, especially those recognized as critical in humane medicine. These include aminoglycosides, cephalosporins of the 3rd and 4th generation, fluoroquinolones, glycopeptides, macrolides, some penicillins and polymyxins. The article also describes the classification of critical antimicrobials by the European Medicines Agency (EMA) and the Panel of Experts on Antimicrobials (AMEG) of the WHO based on the risk profile for humans through the development of antimicrobial resistance after application to productive animals. Such an assessment will give veterinary practitioners an important justification when they make decisions about the clinical treatment of bacterial infections and the responsible appointment of antimicrobial therapy. This will help to reach the balance among the achievement of the effectiveness of antimicrobial therapy of productive animals, reducing of the selective pressure on the development of antibiotic resistance and ensuring of a high level of human health.

Antimicrobial Resistance Phenotypic Profile of Isolates from Clinical Infections in Dogs

Background: Antimicrobial resistance is described as a condition in which a micro-organism is able to survive when exposed to an antimicrobial agent. The resistance rates to antimicrobials in companion animals have risen considerably. Studies of local antimicrobial susceptibility profiles are needed as well as education and warning about the use of tests for the identification and susceptibility of pathogenic bacterial strains. The aim of this study was to identify the main antimicrobial resistance in clinical samples of dogs, and to detect multidrug-resistant strains of importance to public health.Materials, Methods & Results: Bacterial pathogens of 77 dog infections were isolated and their sensitivity profile to antimicrobials was determined. One hundred bacterial isolates were identified. Of these, 61 were Gram-positive (55 Staphylococcus spp., 4 Enterococcus spp. and 2 Streptococcus spp.) and 39 Gram-negative (36 fermenters and 3 non-fermenters). Seventy-nine isolates were considered multiresistant following individual assessment of drugs, and 85 following the evaluation of classes. Only 3 were sensitive to all drugs. Four isolates were resistant to all classes and only sensitive to some antibiotics. Of the 55 samples of Staphylococcus spp., 36 (65.45%) were identified as phenotypically MRS. Two isolates of Enterococcus spp. were resistant to vancomycin (VRE). Also 66.67% (26/39) of the samples were positive for the presumptive test for ESBL. For the MRS-positive isolates detected in this study, chloramphenicol was the antimicrobial that showed superior sensitivity in 74.29% of the cases (27/36); therefore it is considered the most appropriate for treatment of this type of micro-organism. In case of aminoglycosides, when their resistance was checked in MRS isolates, all resistance percentages increased, implying a limited use of this class for such a type of multi-resistant micro-organism. Contrarily, in case of ESBL, a superior sensitivity was observed towards MRS isolates, thus making them a prime treatment choice for the infection caused by these micro-organisms.Discussion: Literature have reported a gradual increase in multidrug resistance towards antimicrobial agents in veterinary medicine over the past decades. In this study, 64% of multiresistant strains were considered of significant importance, notably MRS (36), VRE (2) and ESBL (26). The early identification of pathogens in animals has become an important step in order to minimize the transmission of antibacterial resistance. The increase in the number of multidrug-resistant bacteria in animals and humans demonstrates the need to develop and implement measures in order to monitor and control the spread of this resistance. It is possible that the increased drug resistance is linked to the constant exposure to these drugs and the subsequent selective pressure, causing the transfer of resistant genes between strains. Carbapenems and glycopeptides should be used with caution in veterinary medicine in order to prevent such processes of selection that develop resistance in micro-organisms to these two classes, which can result in cross-resistance between animals and humans and create obstacles in the treatment of patients, especially for the two drugs mentioned, since they are important for the treatment of nosocomial infections in humans. The resistance percentage towards fluoroquinolones was identified to be higher in Gram-positive isolates, particularly in MRS, which showed 75% resistance against this class (according to the CLSI, resistance to one fluoroquinolone antimicrobial agent provides resistance to other antimicrobials of this class). For ESBL isolates, the resistance was shown to be 50%. The resistance towards the fluoroquinolones and aminoglycosides class can be associated with the expression of the genes that produce ESBL.

40 years of veterinary papers in JAC - what have we learnt?

This review, for the occasion of the 40th anniversary of the Journal of Antimicrobial Chemotherapy (JAC), gives an overview of the manuscripts related to veterinary bacteriology published in the journal in the past 40 years with a focus on 'One Health' aspects. From 1975 to 2000 the number of manuscripts related to veterinary medicine was limited, but thereafter, the number steadily increased. Most manuscripts published were related to food-producing animals, but companion animals and minor species were also covered. Subjects included antimicrobial usage in animals and the consequences for human medicine, new resistance genes and mechanisms, the prevalence and epidemiology of antimicrobial resistance, and the emergence of resistant bacteria in animals with zoonotic potential such as livestock-associated MRSA (LA-MRSA), methicillin-resistant Staphylococcus pseudintermedius (MRSP) and ESBL-producing Enterobacteriaceae. These manuscripts have added to our knowledge on the risks of transmission of resistant bacteria from animals to humans and the importance of the prudent use of antimicrobial agents in veterinary medicine.

Properties and antimicrobial susceptibility of Trueperella pyogenes isolated from bovine mastitis in China.

Trueperella (T.) pyogenes is an opportunistic pathogen that causes suppurative diseases in domestic animals. In this work, the properties, pathogenesis and phenotypic diversity of T. pyogenes isolates from bovine mastitis were studied. Both pyolysin (plo) and collagen-binding protein (cbp) virulence factor genes were detected by PCR in all T. pyogenes isolates (n = 50). Using the tissue culture plate method, 90% of T. pyogenes isolates were able to form biofilms. The minimum inhibitory concentrations (MICs) of 13 antimicrobials against T. pyogenes isolates were determined. High susceptibility was observed to rifampin (96%), ampicillin (94%), ciprofloxacin (94%), and penicillin (92%), while low susceptibility was found to trimethoprim-sulphamethoxazole (10%) and bacitracin (2%). The intracellular assay revealed that T. pyogenes isolates had different cytopathogenic effects on cells. The high percentage (28.6%) of T. pyogenes isolates suggests that this bacterium is an important contributor to mastitis. Moreover, the high occurrence of multidrug resistance, biofilm production, intracellular survival, and the temporal dynamics of T. pyogenes interactions are key factors for a better understanding of how immunity acts on infections with these bacteria and how they evade immune surveillance, thus highlighting the need for the prudent use of antimicrobial agents in veterinary medicine.

Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine as Exemplified by the Swine Pathogen Streptococcus suis.

Use of antimicrobial agents in veterinary medicine is essential to control infectious diseases, thereby keeping animals healthy and animal products safe for the consumer. On the other hand, development and spread of antimicrobial resistance is of major concern for public health. Streptococcus (S.) suis reflects a typical bacterial pathogen in modern swine production due to its facultative pathogenic nature and wide spread in the pig population. Thus, in the present review we focus on certain current aspects and problems related to antimicrobial use and resistance in S. suis as a paradigm for a bacterial pathogen affecting swine husbandry worldwide. The review includes (i) general aspects of antimicrobial use and resistance in veterinary medicine with emphasis on swine, (ii) genetic resistance mechanisms of S. suis known to contribute to bacterial survival under antibiotic selection pressure, and (iii) possible other factors which may contribute to problems in antimicrobial therapy of S. suis infections, such as bacterial persister cell formation, biofilm production, and co-infections. The latter shows that we hardly understand the complexity of factors affecting the success of antimicrobial treatment of (porcine) infectious diseases and underlines the need for further research in this field.

The management of risk arising from the use of antimicrobial agents in veterinary medicine in EU/EEA countries - a review.

Antimicrobials are essential medicines for the treatment of many microbial infections in humans and animals. Only a small number of antimicrobial agents with new mechanisms of action have been authorized in recent years for use in either humans or animals. Antimicrobial resistance (AMR) arising from the use of antimicrobial agents in veterinary medicine is a concern for public health due to the detection of increasing levels of resistance in foodborne zoonotic bacteria, particularly gram-negative bacteria, and due to the detection of determinants of resistance such as Extended-spectrum beta-lactamases (ESBL) in bacteria from animals and in foodstuffs of animal origin. The importance and the extent of the emergence and spread of AMR from animals to humans has yet to be quantified. Likewise, the relative contribution that the use of antimicrobial agents in animals makes to the overall risk to human from AMR is currently a subject of debate that can only be resolved through further research. Nevertheless, risk managers have agreed that the impact on public health of the use of antimicrobials in animals should be minimized as far as possible and a variety of measures have been introduced by different authorities in the EU to achieve this objective. This article reviews a range of measures that have been implemented within European countries to reduce the occurrence and the risk of transmission of AMR to humans following the use of antimicrobial agents in animals and briefly describes some of the alternatives to the use of antimicrobial agents that are being developed.

Antimicrobial Agents in Veterinary Medicine

Antimicrobial Agents in Veterinary Medicine

Workshop report: The 2012 Antimicrobial Agents in Veterinary Medicine: exploring the consequences of antimicrobial drug use: a 3‐D approach

Antimicrobial resistance is a global challenge that impacts both human and veterinary health care. The resilience of microbes is reflected in their ability to adapt and survive in spite of our best efforts to constrain their infectious capabilities. As science advances, many of the mechanisms for microbial survival and resistance element transfer have been identified. During the 2012 meeting of Antimicrobial Agents in Veterinary Medicine (AAVM), experts provided insights on such issues as use vs. resistance, the available tools for supporting appropriate drug use, the importance of meeting the therapeutic needs within the domestic animal health care, and the requirements associated with food safety and food security. This report aims to provide a summary of the presentations and discussions occurring during the 2012 AAVM with the goal of stimulating future discussions and enhancing the opportunity to establish creative and sustainable solutions that will guarantee the availability of an effective therapeutic arsenal for veterinary species.

Antimicrobial resistance and the standards of the World Organisation for Animal Health

Antimicrobial resistance and the use of antimicrobial agents in veterinary medicine are complex issues that are currently a source of major international concern. It is therefore essential for the World Organisation for Animal Health (OIE) to consider this issue, while at the same time continuing to address the problem of zoonotic diseases. That is why the OIE has included objectives for veterinary drugs, especially antimicrobials, in its Strategic Plan. The OIE plays an active part in discussions on this subject in conjunction with other international organisations working in this field, such as the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO). Furthermore, the OIE has adopted guidelines both for defining harmonised methodologies for antimicrobial resistance surveillance and monitoring and for helping countries to conduct a risk analysis tailored to their situation and to take appropriate management measures. The OIE has included this issue in its programme of assistance to countries by offering them structural enhancement tools: the Tool for the Evaluation of Performance of Veterinary Services (O1E PVS Tool), PVS Gap Analysis, veterinary legislation support, and training for veterinary national focal points, with the aid of its Collaborating Centres for veterinary medicinal products. Only by mobilising all countries to improve the quality of antimicrobials, to introduce antimicrobial resistance surveillance and to implement measures for the responsible and prudent use of antimicrobials, will it be possible to halt the spread of antimicrobial resistance.

Prudent use guidelines: a review of existing veterinary guidelines

The World Organisation for Animal Health (OIE) TerrestrialAnimal Health Code considers the prudent use of antimicrobial agents in veterinary medicine to comprise a series of practical measures and recommendations which confer benefits to animal and public health while preserving and maintaining the therapeutic efficacy of antimicrobials. This paper reviews some of the main veterinary prudent use guidelines which have been published in English and the responsibilities of those involved at all levels in the administration of antimicrobials to animals, including national regulatory authorities. The OIE guidelines are considered comprehensive and cover all of those levels, from regulatory authorities to veterinarians and food producers. Guidelines produced by national authorities, professional veterinary associations or farming associations and which are targeted at particular individuals, for example veterinarians or food animal producers, will, obviously, restrict their coverage to those aspects considered relevant for their target audience.

Suscetibilidade a antimicrobianos e produção de betalactamase em amostras de Staphylococcus isolados de mastite caprina no semiárido paraibano

RESUMO Este trabalho teve como objetivo avaliar a susceptibilidade antimicrobiana in vitro e a produção de betalactamase de 42 amostras de Staphylococcus isolados de mastite subclínica caprina. Foram utilizados 14 Staphylococcus chromogenes, 10 S. waneri, 6 S. saprophyticus, 5 S. aureus, 3 S. epidermidis, 2 S. intermedius e 2 Staphylococcus coagulase negativo. Os maiores índices de resistência foram para penicilina 66,67% e ampicilina 63,89% e sensibilidade frente à cefoxitina 97,62%. A múltipla resistência a 3 ou mais antimicrobianos foi observada em 42,86% dos isolados. Das 42 amostras de Staphylococcus avaliadas, 73,81% foram positivas para o teste de produção de betalactamase. A concentração inibitória mínima apresentou 100% das amostras susceptíveis à norfloxacina e os valores de resistência para os demais antimicrobianos não ultrapassaram os 30%. A alta resistência apresentada para penicilina e ampicilina demonstra a limitação no uso desses antimicrobianos no tratamento da mastite caprina na região. Embora neste estudo as cefalosporinas tenham apresentado boa sensibilidade, o uso desses fármacos em medicina veterinária se torna preocupante devido à incidência de estirpes produtoras de betalactamase.

Uso prudente de antimicrobianos y propuestas de mejora en veterinaria

The alarms that have sounded in the last two decades of the 20(th) century in the feld of antimicrobial resistance in livestock farming have led to the development of various measures that have substantially improved the use of antimicrobial agents in veterinary medicine. These measures mainly involve the implementation of new pharmaceutical legislation and the hygiene package provisions. Even though awareness of the regulations is high, surveillance systems have been implemented and the promotion of appropriate use has begun to show results, it is necessary to maintain these measures while promoting alternatives to the use of antimicrobials. In particular, alternatives are needed for those agents used for prevention of bacterial diseases, either specifically, through vaccination and improvement of biosafety (use of insecticides, disinfectants and insect repellents), or generally by improving farm facilities and animal welfare. All of these alternatives would reduce the need to use antimicrobial agents in animals. These actions should be complemented by training for all those players involved (veterinarians, farmers, the pharmaceutical industry, veterinary medicines suppliers and food retailers), and by establishing more effective cooperation between human and veterinary medicine.

Veterinary Drug Usage and Antimicrobial Resistance in Bacteria of Animal Origin

In the production of food animals, large amounts of antimicrobial agents are used for therapy and prophylaxis of bacterial infections and in feed to promote growth. There are large variations in the amounts of antimicrobial agents used to produce the same amount of meat among the different European countries, which leaves room for considerable reductions in some countries. The emergence of resistant bacteria and resistance genes due to the use of antimicrobial agents are well documented. In Denmark it has been possible to reduce the usage of antimicrobial agents for food animals significantly and in general decreases in resistance have followed. Guidelines for prudent use of antimicrobial agents may help to slow down the selection for resistance and should be based on knowledge regarding the normal susceptibility patterns of the causative agents and take into account the potential problems for human health. Current knowledge regarding the occurrence of antimicrobial resistance in food animals, the quantitative impact of the use of different antimicrobial agents on selection of resistance and the most appropriate treatment regimes to limit the development of resistance is incomplete. Programmes monitoring the occurrence and development of resistance and consumption of antimicrobial agents are strongly desirable, as is research into the most appropriate ways to use antimicrobial agents in veterinary medicine.

Use of Antimicrobial Agents in Veterinary Medicine and Implications for Human Health

This review discusses why veterinary usage of antimicrobial agents is wrongly accused of causing a substantial part of the problem of resistant human pathogens. Without doubt, resistant organisms in animals are selected by veterinary antimicrobials. However, these are not a major human health risk either because the role of veterinary usage in selection or propagation is insignificant, or because resistant populations selected by veterinary usage do not pose a substantial risk to human health. Indeed, resistant bacterial infections in humans causing serious quantitative and qualitative health consequences are rarely food-borne and are not the same as those selected by veterinary usage of antimicrobial agents. The available evidence for veterinary selection of resistance, transmission to humans, and subsequent health consequences are reviewed for food-borne zoonotic pathogens. A risk assessment strategy is proposed to quantify potential hazards in order to decide on the most effective risk management strategy.

CpG oligodeoxynucleotides stimulate canine and feline immune cell proliferation

Oligodeoxynucleotides (ODNs) with unmethylated CpG dinucleotide motifs may be useful as non-specific immune system stimulants and adjuvants for protein or nucleic acid vaccines in humans and other primates. They may also be useful in cancer immunotherapy and in the modulation of allergic responses or mucosal immunity. To begin to determine the potential utility of CpG ODN technology in small animal veterinary medicine, we developed procedures to analyze the effects of CpG ODN on canine and feline blood, spleen and lymph node (LN) cells. We find that certain CpG ODN cause good lymphocyte proliferation (as monitored by [ 3 H] -thymidine incorporation) in both canine and feline spleen and LN cells, but not in blood. This overall stimulatory effect of CpG ODN on spleen and LN cells is CpG dependent. The reverse sequences, GpC ODNs, do not cause significant lymphocyte proliferation in the cat; however, dogs are more sensitive to stimulation by the non-specific immune effects of the phosphorothioate backbone. We conclude that unmethylated CpG ODNs may also have potential uses as immune stimulants for vaccines and other antimicrobial agents in veterinary medicine for companion animals.