Bacterial Culture and Sensitivity Testing: Methods and Interpretation

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Specimen quality is paramount; collection before antimicrobial therapy, using appropriate transport media (e.g., Amies with charcoal for aerobes/anaerobes), and timely processing (within 24-48 hours for swabs, 30 minutes for urine) are critical for accurate bacterial culture and sensitivity results.
• Standard identification strategies combine macroscopic colony morphology, Gram staining, and biochemical panels, with advanced methods like MALDI-TOF mass spectrometry offering rapid and precise species determination, which is crucial as resistance patterns vary significantly between species.
• Antimicrobial susceptibility is determined by disk diffusion (Kirby-Bauer) or broth dilution (MIC) methods, with results interpreted against CLSI-published veterinary-specific breakpoints to categorize isolates as susceptible, intermediate, or resistant, guiding therapeutic choices.
• Culture-negative results do not definitively rule out infection and may indicate prior antimicrobial use, the presence of fastidious or non-viable organisms, or a non-bacterial etiology; molecular methods like PCR can detect pathogens but do not provide susceptibility data.
• Intermediate susceptibility results indicate a borderline situation where higher doses or drugs concentrating at the infection site may be effective, while oxacillin resistance in staphylococci predicts resistance to all beta-lactams, necessitating selection from alternative drug classes.
• Quantitative culture is essential for differentiating infection from contamination at sites with expected commensal flora (e.g., urine, duodenal juice, BAL fluid), with specific colony count thresholds guiding interpretation.

This article explains the laboratory methods used to culture bacteria from veterinary specimens and to determine antimicrobial susceptibility. It is written for veterinary students and practitioners who submit samples to diagnostic laboratories and need to interpret the resulting reports. The content covers specimen handling, culture techniques, identification strategies, susceptibility testing methods, and the clinical reasoning that connects laboratory findings to therapeutic choices. Specific bacterial diseases and individualised treatment protocols are outside the scope of this reference.

Bacterial culture and sensitivity testing answer two related questions. First, which bacteria are present in a clinical specimen and in what relative quantity? Second, which antimicrobial agents are likely to inhibit those bacteria at concentrations achievable in the patient? The first question requires appropriate specimen collection, transport, and culture conditions. The second requires standardized susceptibility testing and knowledge of the interpretive criteria that define susceptible, intermediate, and resistant categories.

The value of culture and sensitivity testing depends entirely on the quality of the specimen submitted. A poorly collected or improperly transported sample produces misleading results regardless of laboratory skill. Conversely, a well-collected specimen from a site with a genuine bacterial infection can guide therapy with far greater precision than empirical drug selection. The procedures described here follow the standards used by veterinary diagnostic laboratories and reference bodies such as the MSD Veterinary Manual and the American Veterinary Medical Association practice resources.

At a Glance

Specimen Collection and Transport

The specimen must represent the site of infection and avoid contamination from adjacent flora. Collection methods include sterile swabs, tissue biopsy, aspirates of fluid, and urine obtained by cystocentesis. Swabs are acceptable for superficial wounds and mucosal surfaces, but aspirates and tissue samples yield higher diagnostic value for deep infections. For bite wounds, both aerobic and anaerobic culture should be requested because mixed populations are common. In a prospective study of 104 dog bite wounds, 67% grew a mixture of aerobes and anaerobes, and infected wounds were significantly more likely to culture positive than contaminated wounds (bacteriology of infected and non-infected dog bite wounds).

Transport conditions affect organizm viability. Aerobic organizms survive on swabs in transport medium for 24 to 48 hours at refrigerated temperature. Anaerobic organizms are more fragile and benefit from rapid transport in anaerobic transport systems. Urine should be cultured within 30 minutes of collection or refrigerated and processed within 24 hours. Samples from body cavities and joints should be submitted in sterile containers without additives. Freezing is generally detrimental to bacterial recovery. One study of milk samples found that freezing at -20°C for 24 hours significantly reduced the yield of Gram-positive catalase-positive cocci, Gram-negative bacilli, and Gram-positive bacilli compared with fresh processing (diagnosis of intramammary infection in culture-negative samples).

Culture Methods and Isolation

Primary culture uses solid media that support the growth of common veterinary pathogens. Blood agar supports most aerobic and facultative organizms. MacConkey agar selects for Gram-negative bacilli and indicates lactose fermentation. Additional media may be used for specific specimen types or suspected organizms. Cultures are incubated at 35 to 37°C in air, with added carbon dioxide for some fastidious species, and examined at 24 and 48 hours. Anaerobic culture requires an oxygen-free environment provided by an anaerobic jar, chamber, or commercial gas-generating system.

Quantitative culture is used when the distinction between infection and contamination matters. Urine cultures are interpreted by colony count, with significant bacteriuria defined by the laboratory reference for the collection method. Quantitative duodenal juice culture has been used to define small intestinal bacterial overgrowth in dogs, with a threshold of more than 10^5 colony-forming units per milliliter (comparison of direct and indirect tests for small intestinal bacterial overgrowth). Similar quantitative logic applies to bronchoalveolar lavage fluid and other sites where commensal flora are expected.

Identification of Isolates

Identification begins with colony morphology, hemolysis pattern, and Gram stain reaction. Gram-positive cocci in clusters suggest staphylococci, in chains suggest streptococci, and Gram-positive rods suggest Bacillus, Corynebacterium, or anaerobes. Gram-negative rods require further differentiation using oxidase, catalase, and biochemical panels. Commercial identification systems and MALDI-TOF mass spectrometry provide rapid, accurate species identification for most veterinary isolates.

Species identification matters for susceptibility interpretation because resistance patterns differ. Oxacillin resistance among Staphylococcus intermedius isolates from canine clinical samples increased over a five-year period and was associated with multidrug resistance, with one in five staphylococcal isolates resistant to oxacillin by 2005 (prevalence of oxacillin and multidrug resistant staphylococci in dogs). Accurate species identification allows the laboratory to apply the correct interpretive criteria and alerts the clinician to organizms with predictable resistance mechanisms.

Antimicrobial Susceptibility Testing

Susceptibility testing determines whether an organizm is inhibited by clinically achievable antimicrobial concentrations. The two standard methods are disk diffusion and broth dilution. Disk diffusion, also called the Kirby-Bauer method, places paper disks impregnated with fixed antimicrobial concentrations on an inoculated agar plate. After incubation, the zone of inhibition around each disk is measured and compared with published breakpoints. Broth dilution methods determine the minimum inhibitory concentration (MIC), the lowest antimicrobial concentration that prevents visible growth. MIC values are expressed in micrograms per milliliter and interpreted using the same breakpoint systems.

Interpretive breakpoints are published by the Clinical and Laboratory Standards Institute (CLSI). Veterinary-specific breakpoints exist for common drug-organizm combinations in dogs, cats, horses, and food animals. Where veterinary breakpoints are unavailable, human breakpoints may be applied with caution. The laboratory report should state the method used and the breakpoint source. Susceptibility categories are reported as susceptible, intermediate, or resistant. An intermediate result does not necessarily mean therapeutic failure, it may indicate that higher doses or site-specific concentrations could be effective.

Interpretation of Culture Results

Culture results must be interpreted in the context of specimen quality, sampling site, and the patient's clinical status. A positive culture does not prove causation, and a negative culture does not exclude infection. Growth of a potential pathogen from a contaminated or poorly collected specimen can misdirect therapy, while failure to grow fastidious or anaerobic organizms from an improperly transported sample can produce a false negative.

Quantitative culture adds interpretive value in specific settings. For duodenal juice in dogs, a threshold of greater than 10⁵ colony-forming units per milliliter has been used to classify small intestinal bacterial overgrowth, although clinical response to antibiotics does not always correlate with bacterial numbers German et al., quantitative duodenal juice bacteriology. In urine specimens collected by cystocentesis, any growth of a uropathogen is generally considered significant, whereas voided samples require higher thresholds. In bronchoalveolar lavage fluid, growth above 10⁴ CFU per milliliter is often used as a cutoff, but this varies with the laboratory and the species.

Mixed cultures present a common interpretive challenge. Polymicrobial growth is expected from sites with resident microbiota, including skin, mucosal surfaces, and bite wounds. In a prospective study of canine bite wounds, 67% of wounds grew a mixture of aerobes and anaerobes, and infected wounds were significantly more likely to culture positive than contaminated wounds Meyers et al., bacteriology of dog bite wounds. When a mixed culture is reported, the clinician must decide which organizms are clinically relevant. Prioritize organizms present in high numbers, organizms isolated in pure culture, and organizms with known pathogenic potential at that site. Ignore probable contaminants unless they dominate the growth or the patient fails to respond to therapy directed at the primary pathogen.

Antimicrobial Susceptibility Testing: Methods

Susceptibility testing determines whether an isolate is likely to respond to a given antimicrobial at standard dosing. Two principal methods are used in veterinary diagnostics: disk diffusion and broth dilution.

Disk diffusion, also called the Kirby-Bauer method, involves placing paper disks impregnated with fixed antimicrobial concentrations onto an agar plate inoculated with a standardized bacterial suspension. After incubation, the diameter of the zone of inhibition is measured and compared with interpretive criteria. The method is inexpensive, flexible, and suitable for most rapidly growing aerobes. It provides a qualitative result: susceptible, intermediate, or resistant.

Broth dilution methods determine the minimum inhibitory concentration (MIC), the lowest antimicrobial concentration that visibly inhibits bacterial growth. MIC testing can be performed in tubes, microtitre plates, or commercial panels. The result is quantitative and allows comparison with achievable drug concentrations at the site of infection. MIC values are particularly useful for organizms with slow growth, for anaerobes, and when the infection site has poor drug penetration.

Both methods require standardized inoculum preparation, controlled incubation conditions, and validated interpretive breakpoints. Breakpoints are derived from pharmacokinetic and pharmacodynamic data, clinical outcome studies, and population distributions of MIC values. Veterinary-specific breakpoints exist for some organizm-drug combinations, but for many combinations the laboratory must rely on human breakpoints. This limitation matters because drug doses, protein binding, and tissue penetration differ between species. When veterinary breakpoints are unavailable, the susceptibility result should be interpreted with caution and in light of the specific dose and dosing interval used.

Interpreting Susceptibility Results

The susceptibility report classifies each organizm-antimicrobial pair as susceptible, intermediate, or resistant. These categories predict the likelihood of clinical success at standard dosing.

The intermediate category is not a failure of the test. It identifies a borderline situation where the outcome depends on the dose, the drug's pharmacokinetics, and the infection site. For example, an isolate classified as intermediate to a beta-lactam might respond to treatment of a urinary tract infection, where the drug reaches high concentrations, but not to treatment of osteomyelitis.

Oxacillin resistance in staphylococci requires special attention. Oxacillin resistance predicts resistance to all beta-lactam antimicrobials, including penicillins, cephalosporins, and carbapenems, regardless of the in vitro results for those drugs. In canine clinical samples, oxacillin resistance among Staphylococcus intermedius isolates increased over a five-year period and was associated with multidrug resistance Jones et al., oxacillin resistance in canine staphylococci. When a staphylococcal isolate is reported as oxacillin resistant, the clinician should assume beta-lactam resistance and select therapy from a different drug class.

Susceptibility Testing in Special Populations

Anaerobes are not routinely tested in all laboratories. Susceptibility testing of anaerobes is technically demanding, slow, and often unnecessary because many anaerobes have predictable susceptibility patterns. Testing is reserved for serious infections, immunocompromised patients, or when the patient has failed empirical therapy. When anaerobes are tested, MIC methods are preferred over disk diffusion.

Slow-growing organizms, including Nocardia, Actinomyces, and some mycobacteria, require prolonged incubation and specialised media. Susceptibility testing for these organizms is performed by reference laboratories and may take weeks. The clinician should not delay therapy while awaiting results. Empirical treatment should be initiated based on the organizm's expected susceptibility profile and adjusted when the report becomes available.

Freshwater-associated infections illustrate the importance of species-specific susceptibility data. Aeromonas species isolated from water and animal tissue samples were relatively resistant to trimethoprim, cefazolin, and ampicillin, while ciprofloxacin, imipenem, ceftazidime, and trimethoprim-sulfamethoxazole were effective against more than 90% of Gram-negative isolates Auerbach et al., freshwater bacteriology and susceptibility. Empirical therapy for infections acquired from freshwater environments should account for these resistance patterns, and culture and susceptibility testing should guide definitive treatment.

Molecular Methods and Culture Correlation

Molecular methods, particularly real-time polymerase chain reaction (PCR), are increasingly used for direct detection of pathogens from clinical samples. PCR offers speed and sensitivity, but it does not provide a viable isolate for susceptibility testing. In bovine mastitis diagnostics, PCR identified bacteria in 89% of clinical samples compared with 77% by culture, and PCR detected major pathogens in many samples that were culture negative Koskinen et al., PCR versus culture for mastitis diagnosis. However, PCR also detected three or more bacterial species in a large number of clinical samples, a finding that may represent mixed infection, contamination, or detection of non-viable organizms.

Culture remains necessary when susceptibility testing is required. PCR-positive, culture-negative samples present a clinical dilemma: the pathogen is identified, but no isolate is available for susceptibility testing. In this situation, the clinician must rely on published susceptibility data for the identified species, local resistance patterns, and the patient's response to empirical therapy. Freezing milk samples before culture can reduce the yield of Gram-positive cocci and Gram-negative bacilli, so samples intended for culture should be processed promptly Bexiga et al., culture of frozen milk samples.

Documentation and Reporting

The laboratory report should include the specimen type, collection date, culture method, quantity of growth, organizm identification, and susceptibility results. The clinician should record the indication for culture, the antimicrobials used before sampling, and the clinical response to therapy. This information supports interpretation of the culture result and informs future treatment decisions.

Susceptibility reports should list only antimicrobials that are clinically relevant and licensed for the species being treated. Reporting drugs that are not approved for the species or that have no veterinary breakpoints can lead to inappropriate prescribing. The clinician should verify that the reported antimicrobials are appropriate for the patient's species, the infection site, and the production system. Regional differences in antimicrobial availability and regulatory requirements also influence drug selection, and the AVMA practice resources and MSD Veterinary Manual provide species-specific guidance on antimicrobial use.

Recognized Complications and Failure Modes

Culture and susceptibility testing can fail silently. The most consequential failure is a false-negative culture result from a sample that was collected after antimicrobial therapy began, transported improperly, or processed with an inappropriate atmosphere. Detection depends on correlating the laboratory result with the clinical picture. A negative culture from a lesion with cytologic evidence of sepsis should trigger suspicion of a sampling or transport problem, not immediate acceptance of the result.

Contamination produces the opposite error. Skin commensals, environmental organizms, and laboratory contaminants can be misidentified as pathogens. The risk is highest with samples collected through infected tissue planes or from sites that are difficult to decontaminate. Discriminating contamination from true infection requires attention to the quantity and purity of growth, the organizm's known habitat, and the cytologic correlation. Growth of multiple organizms with no dominant isolate, especially when the sample was collected through a contaminated route, favours contamination over polymicrobial infection.

Antimicrobial susceptibility results can mislead when the tested drug does not reflect the drug that will reach the infection site. Disc diffusion and broth dilution methods assume achievable drug concentrations at the site of infection. For infections in sequestered sites such as the central nervous system, the eye, or abscess cavities, a susceptible result may not predict clinical efficacy. The clinician must integrate pharmacokinetic knowledge with the laboratory report.

Early detection of these failures requires systematic review of each culture request. Check the submission date against the treatment history. Confirm that the sample type and collection method match the laboratory's validated protocols. Review the Gram stain or cytology alongside the culture result. Discrepancies between direct examination and culture are the earliest warning that something has gone wrong.

Common Errors and Corrective Actions

Less experienced clinicians frequently submit samples that are too small, too dry, or collected from a site that has been recently treated with topical antiseptics. A swab that barely touches the lesion surface yields few viable organizms. The corrective action is to collect generous samples from the active edge of a lesion, using tissue or fluid instead of swabs where possible, and to place samples in appropriate transport media immediately.

A second common error is requesting susceptibility testing on every isolate regardless of clinical significance. This practice generates reports that can mislead treatment decisions and consumes laboratory resources. Susceptibility testing should be performed on isolates judged likely to be pathogens based on sample quality, quantity of growth, and clinical context. Commensal flora and probable contaminants do not require susceptibility testing.

Misinterpretation of intermediate susceptibility results is another frequent error. An intermediate result does not mean the drug is ineffective. It means the drug may be effective if the infection site achieves higher drug concentrations, such as with urinary tract infections where many drugs concentrate in urine. The clinician should check whether the drug has site-specific pharmacokinetic advantages before discarding it.

Students and clinicians also err by treating the susceptibility report as a fixed prescription instead of a decision aid. The report lists drugs tested against the isolate, but the choice of drug must incorporate patient factors, formulation availability, cost, and the risk of promoting further resistance. The laboratory report narrows the options, it does not make the decision.

Limitations of Current Evidence

The evidence base for veterinary bacteriology carries important gaps. Much of the published data on antimicrobial susceptibility comes from single institutions or regional referral populations, and resistance patterns vary substantially by geography and over time. A susceptibility pattern reported from one region may not apply to another. The increase in oxacillin resistance among staphylococci from canine clinical samples documented at one teaching hospital illustrates how resistance can shift within a single population over a few years. Clinicians should interpret published resistance data with caution and rely on local laboratory data where available.

Culture-based methods have inherent detection limits. Studies of bovine mastitis samples show that PCR identifies pathogens in a substantial number of samples that are culture-negative, and culture can miss organizms present in mixed infections. Similarly, samples that yield minor pathogens or no growth in conventional culture may still harbour significant organizms detectable by molecular methods. These findings indicate that a negative culture does not exclude infection, particularly when the clinical presentation strongly suggests a bacterial cause.

Quantitative culture thresholds for sites such as the small intestine remain contested. The definition of small intestinal bacterial overgrowth based on duodenal juice bacterial counts has been questioned, and the correlation between bacterial numbers and clinical response to antibiotics is imperfect. Expert opinion differs on whether quantitative thresholds or clinical response should define the syndrome.

Escalation and Referral

Referral or specialist consultation is warranted when the infection fails to respond to therapy guided by susceptibility testing, when the isolate is unusual or highly resistant, or when the infection involves a site where treatment failure carries serious consequences. A veterinary microbiologist or clinical pathologist can advise on additional testing, alternative drug classes, or interpretation of unusual resistance patterns.

Laboratory involvement should be sought early when the clinical picture and culture results conflict. The laboratory can repeat identification, perform additional biochemical tests, or clarify whether a particular result reflects a technical issue. Direct communication with the laboratory is more productive than repeated submissions of the same sample type.

Regulatory reporting obligations vary by jurisdiction and by the organizm isolated. Certain pathogens, particularly those with zoonotic potential or those subject to surveillance programs, may require notification to public health or animal health authorities. The WOAH terrestrial animal health standards describe international reporting expectations for listed diseases, and national veterinary authorities publish local requirements. The AVMA practice resources provide guidance on professional obligations in the United States. Clinicians should know which organizms in their region trigger reporting requirements before they encounter them.

Troubleshooting Guide

The MSD Veterinary Manual provides species-specific guidance on sample collection and interpretation that can supplement laboratory protocols.

Frequently Asked Questions

How should I proceed when a laboratory reports "no growth" but I strongly suspect a bacterial infection?

A "no growth" result does not exclude infection. Consider prior antimicrobial administration, which suppresses viable organizms for days. Review specimen quality and transport conditions. Anaerobes, fastidious organizms, and intracellular pathogens may fail to grow on routine media. In mastitis samples, culture-negative results are common, and molecular methods such as real-time PCR can detect pathogens that conventional culture misses, as demonstrated in field comparisons of bovine milk samples. Repeat sampling from a fresh lesion, add anaerobic culture, or request extended incubation. Correlate with cytology, which may reveal bacteria even when culture is negative. If clinical signs are compelling, treat based on cytologic findings and known local resistance patterns while awaiting confirmatory testing.

What minimum equipment and expertise are needed to perform in-house culture and susceptibility testing?

A standard incubator, sterile loop, blood agar, MacConkey agar, and Gram stain supplies permit aerobic isolation and preliminary identification. Disc diffusion requires Mueller-Hinton agar, standardized inoculum, commercial antibiotic discs, and zone measurement tools. Interpretive criteria require current breakpoint tables, which laboratories must update regularly. In-house testing suits simple aerobes such as Escherichia coli and staphylococci. Anaerobic culture, MALDI-TOF identification, and broth microdilution are impractical in most practice settings. Refer isolates with unusual morphology, mixed growth, or suspected resistance to a reference laboratory. The MSD Veterinary Manual provides guidance on laboratory methods and quality assurance expectations for practice-based testing.

How do culture and susceptibility results differ between dogs and cats, and when should I adjust my interpretation?

Species-specific differences in normal flora and common pathogens affect interpretation. Dog bite wounds, for example, frequently yield mixed aerobic and anaerobic populations, with Pasteurella canis and streptococci predominating in infected wounds. Feline wounds more often involve Pasteurella multocida. Susceptibility breakpoints are generally derived from human or canine data, and extrapolation to cats may misclassify isolates. Oxacillin resistance in canine staphylococci has increased and is associated with multidrug resistance, so confirm methicillin resistance with additional testing instead of assuming oxacillin results apply across species. When breakpoints are uncertain, report the isolate and request reference laboratory testing with species-specific interpretive criteria where available.

What should I do when the laboratory reports an isolate as susceptible to an antibiotic I cannot use in that patient?

Susceptibility reports list options, not mandates. Cross-reference the report with patient factors including species, age, pregnancy status, organ function, and withdrawal periods for food animals. Consult current formulary and label references for species-specific contraindications. If the preferred drug is unavailable, select an alternative with a similar mechanism and predicted cross-susceptibility, but verify this against the actual susceptibility pattern instead of assuming class equivalence. For multidrug-resistant isolates, request additional agents or minimum inhibitory concentration testing. The AVMA practice resources address judicious antimicrobial use principles that support rational selection when standard options are excluded.

How should I document culture and susceptibility results in the medical record?

Record the specimen source, collection date and method, transport medium, and time to laboratory processing. Document the isolation method, colony morphology, Gram stain appearance, and identification method. List each antimicrobial tested with the zone diameter or minimum inhibitory concentration value and the interpretive category. Note any discrepancies between in-house and reference laboratory results. Record the clinical decision, including the antimicrobial selected, dose, and duration, and the rationale when the choice deviates from the susceptibility report. This documentation supports antimicrobial stewardship reviews and future treatment decisions. The Davis-Thompson Foundation case materials illustrate structured diagnostic reporting that can guide record keeping.

How do I explain culture and susceptibility results to a client who expects an immediate answer?

Explain that culture takes 24 to 72 hours because bacteria must grow before identification and testing. Describe the process in practical terms: the laboratory grows the organizm, identifies it, then tests which antibiotics stop its growth. Emphasize that the test identifies the best options, not that other antibiotics are ineffective. If empiric treatment was started, explain that results may confirm the current choice or support a change. For resistant infections, frame the result as information that allows targeted therapy instead of failure. Acknowledge that some infections require repeat sampling. The WOAH terrestrial animal health standards emphasize transparent communication of diagnostic findings in animal health programs, a principle that applies equally to individual client discussions.

Related Clinical & Scientific Guides

• Hypersensitivity Reactions: Types and Mechanisms
• Therapeutic Decision-Making for Respiratory Infections in Cattle
• Monitoring Fluid Therapy in Critically Ill Veterinary Patients

References and Further Reading

• Bacteriology of the freshwater environment: implications for clinical therapy.. 1987.
• The bacteriology and antimicrobial susceptibility of infected and non-infected dog bite wounds: fifty cases.. 2008.
• Prevalence of oxacillin- and multidrug-resistant staphylococci in clinical samples from dogs: 1,772 samples (2001-2005).. 2007.
• Field comparison of real-time polymerase chain reaction and bacterial culture for identification of bovine mastitis bacteria.. 2010.
• Comparison of direct and indirect tests for small intestinal bacterial overgrowth and antibiotic-responsive diarrhea in dogs.. 2003.
• Diagnosis of intramammary infection in samples yielding negative results or minor pathogens in conventional bacterial culturing.. 2011.
• Davis-Thompson Foundation Veterinary Pathology Resources. Davis-Thompson Foundation.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

Related Articles

• Bacterial Pathogenesis: Virulence Factors and Mechanisms
• Clinical Pathology: Hematology and Biochemistry Interpretation
• Interpretation of Histopathology Reports: A Guide for Clinicians
• Diagnostic Cytology: Sample Collection and Interpretation
• Therapeutic Decision-Making for Bacterial Skin Infections in Dogs

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.