Swine Pasteurella multocida Vaccine, Live (Strain 679-230) is a veterinary biological active ingredient consisting of lyophilized live attenuated Pasteurella multocida bacteria carrying the strain designation 679-230. It is assigned to the presentation family of veterinary-grade API for tablets, injections, capsules, powders, granules, premix, and solutions; however, the live-cell nature of this strain restricts the biologically valid presentation to the lyophilized powder-in-vial form for reconstitution as an injectable suspension. Tablet, capsule, granule, and premix formats are not appropriate for delivery of this live bacterial antigen because compression shear, binder exposure, and gastrointestinal pH would reduce viable count below the minimum dose requirement. The strain is intended for active immunization of healthy swine against pasteurellosis caused by Pasteurella multocida. In pharmacopoeial monographs and marketing authorizations, strain 679-230 is specified as a live vaccine strain with defined limits for viable count, residual moisture, purity, safety, and efficacy.

The model identifier is the strain designation 679-230, which links the product to an attenuated parent culture maintained in a seed lot system. Pasteurella multocida in swine is associated with pneumonia, atrophic rhinitis, and septicemia. The live vaccine is used to stimulate immunity before field exposure; however, the exact age at first vaccination, route, booster schedule, and duration of immunity must be verified against the approved product-specific summary of product characteristics because the strain is not interchangeable with inactivated Pasteurella multocida bacterins or toxoid-containing combination products.

How Is a Releaseable Lyophilized Plug Distinguished from a Failed Batch?

Release testing for the 679-230 live vaccine focuses on the physical state of the lyophilized plug, the viable count after reconstitution, and the absence of adventitious agents. The lyophilized plug must be intact, uniform, and easily reconstitutable in sterile diluent. A collapsed or fragmented plug is not acceptable because it indicates moisture penetration, insufficient primary drying, or loss of vacuum during storage. The release specification table below summarizes the control parameters that a batch must satisfy before distribution.

The limit of ≥ 2.0 × 10⁹ CFU per dose is a minimum release value; commercial batches are typically controlled to exceed this value because viable count declines during storage under 2 °C to 8 °C. The residual moisture limit of ≤ 3.0% is critical for live-cell stability because higher moisture in the lyophilized plug accelerates degradation of the bacterial cell membrane and reduces viable count. Batch release data are reviewed under testing and release obligations comparable to 21 CFR 211.165, with stability data collected under long-term and accelerated conditions to justify the approved shelf life.

Unlike inactivated Pasteurella multocida bacterins, which deliver a fixed mass of antigen in an oil or aluminum hydroxide adjuvant, the live 679-230 strain replicates in the host after parenteral injection and stimulates both humoral and cell-mediated immune responses. The absence of oil adjuvant reduces the frequency of injection-site granulomas, but it also means that the product cannot be expected to provide the same duration of immunity as a two-dose inactivated program. Mucosal IgA responses may be induced when the live strain is administered by a route that permits bacterial replication in nasopharyngeal-associated lymphoid tissue; however, published data for this specific configuration is limited. The onset of immunity is generally reported as 7 to 14 days after vaccination in challenge studies, whereas inactivated bacterins usually require a primary and booster series to reach protective titers.

The live vaccine differs from subunit vaccines based on outer membrane proteins or recombinant dermonecrotoxin derivatives because it presents multiple surface antigens in replicating form. This antigenic breadth can be relevant under field conditions where Pasteurella multocida isolates vary in capsular type and somatic antigen. The product is not a substitute for toxoid-based vaccines against progressive atrophic rhinitis when the primary pathogenic mechanism is the Pasteurella multocida dermonecrotoxin rather than septicemic or pneumonic infection. The live 679-230 product should also be differentiated from avirulent live vectors and chemically attenuated preparations, which may have different safety and shedding profiles in swine populations.

Production-Scale Freeze-Drying Controls Viable Count More Than Fermentation Biomass

In commercial manufacturing, the upstream fermentation of Pasteurella multocida strain 679-230 is conducted in stirred-tank bioreactors at 37 °C with dissolved oxygen maintained above 30% saturation and pH controlled between 7.2 and 7.6. The harvested cell paste is formulated with stabilizers and filled into glass vials. The subsequent lyophilization step, rather than the fermentation biomass, is the dominant source of viable count loss. Production-scale freeze-dryers for this type of live bacterial vaccine commonly operate with shelf temperature ramped from −45 °C to −20 °C during primary drying, chamber pressure between 30 Pa and 80 Pa, and condenser temperature below −55 °C. Load-dependent edge-vial and center-vial temperature differences can produce inter-vial residual moisture variation; vials with poor shelf contact or high fill volume may retain moisture above 3.0% and fail release. Therefore, batch loading patterns, fill volume, and shelf contact are monitored in routine commercial freeze-drying to maintain viable count at or above the release limit after reconstitution.

The formulation collapse temperature is a critical process boundary. If the product temperature exceeds the collapse temperature during primary drying, the lyophilized matrix can lose macroporous structure, slow reconstitution, and reduce the recoverable viable count. Industrial cycles are therefore developed with thermocouple and comparative pressure measurement to confirm that the product remains below collapse temperature and that primary drying is complete before secondary drying. Secondary drying is used to reduce residual moisture below the release limit; excessive secondary drying, however, can desiccate the bacterial cells beyond their tolerance and reduce viable count. The drying endpoint is verified by comparative pressure measurement, not by time alone. For this live bacterial strain, a collapsed or moisture-stressed batch should not be reworked by re-lyophilization because the additional thermal and osmotic stress causes unpredictable viable count loss.

For field administration, the freeze-dried powder is reconstituted with sterile diluent immediately before injection. The reconstituted suspension should be used within 2 hours when held at 2 °C to 8 °C; extended holding at room temperature causes viable count decline. Pigs are usually vaccinated at an age and by a route defined in the approved product documentation; the product is not a mass-medication premix, and feed or water delivery is not recommended because the live organism cannot survive gastric pH and bile salts. When handling the product, personnel should use aseptic technique to avoid introducing environmental contaminants into the reconstituted vial. The vaccine should not be mixed with antimicrobial solutions or other vaccines in the same syringe unless compatibility has been demonstrated for the specific combination.

The route of administration is typically subcutaneous or intramuscular, but the approved label may specify one route over the other to reduce local reactions or optimize immune response. Vaccination should be deferred in animals with fever, severe parasitism, or immunosuppressive disease because the live strain requires competent host responses to establish immunity. The product is not recommended for use in sows during late gestation unless specifically authorized, because live bacterial replication may be associated with transient pyrexia or reproductive stress in susceptible animals. Published data for this specific configuration in pregnant sows is limited; therefore, use should follow the approved product documentation and veterinary risk assessment.

When Concurrent Antimicrobials Suppress Strain 679-230 Replication

Because strain 679-230 is a live attenuated bacterium, its replication in vivo is inhibited by circulating concentrations of antimicrobial agents. Antimicrobial feed additives, injectable antibiotics, or drinking-water medications administered within a defined interval before or after vaccination may reduce or abolish the immune response. The withdrawal interval is product-specific; typical guidelines for live Pasteurella vaccines recommend avoiding antimicrobial therapy for 7 days before and 7 days after vaccination unless the product-specific summary of product characteristics states otherwise. Tetracyclines, β-lactams, sulfonamides, and macrolides are of particular concern because they are active against Pasteurella multocida. This constitutes a major operational boundary for the live 679-230 vaccine and differentiates it from inactivated Pasteurella multocida bacterins, which do not require viable bacterial replication and are therefore tolerant of concurrent antibiotic use within the same period.

In herds where antimicrobial feed additives are used continuously, vaccination with the live 679-230 strain may be contraindicated unless the feed medication is withdrawn for the required interval. The presence of subinhibitory antimicrobial concentrations can also generate a weak immune response that is not detectable by routine serology but fails to protect against field challenge. Diarrhea, high environmental temperature, and transport stress can further reduce the viable dose available for immune induction. These limitations must be considered when planning vaccination programs in high-health or high-stress production systems.

Comparative Release Data for Live and Inactivated Pasteurella multocida Products

The following table compares the live 679-230 product with inactivated Pasteurella multocida bacterins. The comparison is based on general immunobiological properties and should not be used to select a product without review of the approved label, challenge data, and regional regulatory authorization.

Batch release for the live 679-230 product includes both in-process and final-product controls conducted under 21 CFR 211.165 or equivalent GMP principles. Environmental monitoring of filling and lyophilization suites is performed according to ISO 14644-1:2015 cleanroom classification. The product should be transported and stored at 2 °C to 8 °C and protected from light. Freezing of the lyophilized plug is not required after lyophilization, but rehydration with warm diluent may cause thermal shock and viable count loss. The product should not be used if the vial vacuum is lost, the plug is collapsed, or the reconstituted suspension contains visible particulates. These operational boundaries ensure that the live bacterial antigen is delivered within its established potency specification.