For farm-level mass application through drinking water or drench administration, the live paratyphus vaccine API is first converted into a lyophilised oral powder. A stabiliser matrix composed of sucrose and trehalose at a 1:1 mass ratio plus phosphate buffer adjusted to pH 7.0–7.4 is blended with the live bacterial antigen before freezing. The bulk suspension is filled into stainless steel trays and placed in a production freeze dryer where shelf temperature is ramped from −40 °C to −30 °C during primary drying at a chamber pressure of 0.1–0.2 mbar. Secondary drying continues until residual moisture is less than 2.5 % and water activity is controlled at 0.15–0.30. The dried cake is milled under nitrogen purge at 15–20 °C and immediately packed into aluminium foil laminate sachets. Reconstitution at piglet unit level uses potable water from which free chlorine residues have been removed by sodium thiosulphate pretreatment. The reconstituted suspension is administered as a single drench dose or through drinking water lines within 4 h at 20–25 °C; holding beyond this window leads to logarithmic viability loss. Terminal units are 100-dose and 500-dose sachets with an internal desiccant pouch. Batch release includes viable count enumeration and identity testing according to Ph. Eur. 5.2.2. Published stability data for this specific paratyphus strain is limited, therefore real-time storage at 2–8 °C is monitored to full shelf life rather than predicted from accelerated conditions.

Field usage in farrowing units shows the main bottleneck is not the lyophilised powder itself but the quality of the water used for reconstitution. Iron, manganese, and organic matter in borehole water can bind to bacterial cells and reduce recoverable viable count; inline particulate filtration at 5 μm followed by ultraviolet sterilisation is recommended before mixing, although the UV unit must be operated before addition of the vaccine to avoid direct UV killing. Drench equipment with peristaltic pumps should be cleaned with hot water and dried before use; residual disinfectant in dosing lines causes batch-to-batch variability in delivered dose.

Why Aseptic Filling, Not Terminal Sterilisation, Governs Injectable Live Vaccine Safety

If the injection route is selected, the live paratyphus vaccine is supplied as a freeze-dried plug in Type I borosilicate glass vials and is reconstituted with diluent immediately before subcutaneous or intramuscular injection. Because the API contains live bacterial cells, terminal heat sterilisation is incompatible; aseptic filling of the lyophilised bulk is the only practical sterility-assurance pathway. The formulation vehicle is an isotonic phosphate-buffered sucrose solution containing 5–10 % w/v sucrose at pH 7.0–7.2. After filling, semi-stoppered vials enter a freeze dryer equipped with automated stoppering. Primary drying keeps product temperature below −25 °C and secondary drying brings residual moisture below 2.0 %. Headspace oxygen is displaced with nitrogen to less than 3 % before final sealing. Reconstitution time is specified as less than 120 s at 20–25 °C; a longer reconstitution time indicates cake collapse or moisture uptake. Extraneous bacterial and fungal contamination is tested by membrane filtration after specific neutralisation or inhibition of the vaccine strain; the diluent is tested for sterility according to Ph. Eur. 2.6.1. Purity and identity of the live antigen are confirmed by selective agar and serological profiling. The diluent is a separate 10 mL vial of sterile water for injection or isotonic sodium chloride solution, depending on the approved route. The injection route is selected in breeding farms where individual piglet dosing and immediate documentation are required. Batches are packed in partitioned cartons with the vials and diluent syringes separated to prevent mechanical shock during transport.

Production-scale lyophilisation of live bacterial injections presents a known conflict between cake elegance and viability retention. Aggressive secondary drying produces a mechanically robust cake but can reduce CFU count by more than 0.5 log10 if shelf temperature exceeds 25 °C at the end of secondary drying. Therefore the cycle is not optimised for appearance alone; collapsed or friable cakes may be acceptable only if reconstitution time and viable count meet specification. Freeze-dryer loading pattern alters sublimation rate across the batch. Edge vials dry faster than centre vials on shelves with uneven temperature distribution; container-mapping studies are used to define worst-case positions. The formulated product is not compatible with terminal gamma irradiation because free radicals generated in the glass and diluent inactivate the bacterial antigen.

Enteric-Coated Hard Capsule Matrix and Gastric Acid Bypass

Enteric-coated hard capsules are used when oral delivery must bypass gastric low-pH conditions and release live cells in the jejunum. The API is first lyophilised with trehalose and mannitol, dry-milled, and blended with microcrystalline cellulose and magnesium stearate at a final lubricant concentration of 0.25–0.5 %. The blend is filled into size 4 hypromellose capsules, sealed with an aqueous gelatin band, and coated in a side-vented pan coater. The enteric film is based on methacrylic acid–ethyl acrylate copolymer dispersion applied to a coating weight gain of 10–15 %. Inlet air temperature is maintained at 45–50 °C while product bed temperature is kept below 30 °C because live bacterial titre falls when the capsule mass temperature exceeds this range for extended periods. Delayed-release performance is assessed by a modified USP <711> procedure: the capsule remains intact in 0.1 M hydrochloric acid for 2 h at 37 °C, then disintegrates in phosphate buffer pH 6.8 within 30 min. Viable count after acid challenge is expressed as log reduction; the acceptance criterion is typically no more than 1 log10 reduction, although the exact limit is strain-specific and is defined by the marketing authorisation. Terminal packaging is push-through aluminium blister with desiccant.

During enteric coating, process humidity is held below 40 % RH because moisture plasticises the capsule shell and can allow the enteric film to crack at the cap-body interface. Capsule band sealing before coating prevents leakage at the joint when the dosage form travels through the acid phase. The acid-resistance test is performed on whole capsules, not opened capsules, because the cap-body seal is a critical barrier.

For feed premix, carrier selection controls distribution of viable paratyphus vaccine antigen in piglet rations. The lyophilised API is first diluted with carrier at a ratio between 1:9 and 1:19 before final feed addition. The carrier is lactose monohydrate or calcium carbonate pre-dried to moisture below 5 %. Mixing is performed in a low-shear ribbon mixer for 15–20 min to avoid heat accumulation; high-shear mixing is not used. The premix is let down into complete feed at a rate calculated from the CFU/g batch potency and the prescribed dose per kg of final feed; a universal inclusion rate is not applicable because titre varies by seed lot. Homogeneity testing follows the sampling principles of ISO 6497:2002, and stability is evaluated under VICH GL18. Final premix is packed in 20 kg polyethylene-lined paper bags and stored according to the approved stability profile.

Direct Compression Tablet Forming and Viability Preservation

Tablet presentation is applied where individual oral dosing of piglets in large farrowing units is required and medicated feed or drinking water cannot guarantee intake. The live paratyphus API is not compressed in raw state; it is first lyophilised with mannitol and sucrose to produce a dry, free-flowing powder. Direct compression is preferred over wet granulation because residual granulation water reduces viable count. The compression blend contains the API lyophilisate, mannitol, microcrystalline cellulose, crospovidone at 2–4 %, and magnesium stearate at 0.5 %. Tablets are produced on a rotary tablet press using 8 mm flat-faced bevel-edged tooling at compression forces below 10 kN. Hardness is maintained at 30–50 N, friability below 1.0 %, and disintegration in water at 37 °C is less than 60 s. Uniformity of dosage units is verified according to Ph. Eur. 2.9.40 or USP <905>. Tablets are packed in 100-count HDPE bottles with silica gel desiccant and stored at 2–8 °C.

Compression speed and dwell time influence viability. At turret speeds above 30 rpm on a 6 kN press, local adiabatic heating from particle deformation is negligible, but precompression force must be limited to 4 kN to avoid double-shock damage to the lyophilised cells. Tablet porosity remains above 15 % to allow rapid wetting; higher density tablet matrices slow disintegration but improve hardness. The formulation is not suitable for aqueous film coating because water ingress during coating reduces viable count.

Granulation of live vaccine API into dust-free top-dressing granules is performed by fluid-bed top-spray granulation rather than high-shear granulation to limit shear heating. The fluidised API lyophilisate is processed at inlet air temperature 40–50 °C and product bed temperature 28–35 °C. An aqueous polyvinylpyrrolidone binder solution at 5 % w/v concentration is sprayed at a rate that keeps bed moisture below 10 %; the aqueous phase is evaporated rapidly by heated inlet air. Final granules are classified between 250 μm and 850 μm by analytical sieving according to Ph. Eur. 2.9.38. Granules are packed in foil-lined pouches and top-dressed onto creep feed immediately before consumption.

When Liquid Oral Solution Is Selected Over Powder at Breeding Facilities

Liquid oral solutions are used in piglet processing rooms where drench guns or automated oral dispensers are already calibrated. The live vaccine API is suspended or dissolved in a stabiliser vehicle composed of phosphate-buffered sucrose, low-concentration polysorbate at 0.1–0.5 % w/v, and purified water. The pH is adjusted to 6.8–7.2. Filling is performed under nitrogen in amber polyethylene terephthalate bottles to limit oxidative stress. The solution is not heat-sterilised; it is aseptically compounded and stored at 2–8 °C with a short shelf life, typically 14–30 days after production. Preservatives such as benzalkonium chloride are not added because cationic surfactants reduce bacterial viability. Compatibility with oral electrolyte preparations must be verified before mixing; published data for this specific configuration is limited. Terminal package is a 100 mL bottle with a pump dosing device delivering a fixed volume per actuation.

Dissolved oxygen and headspace oxygen must be controlled because oxidative stress damages the bacterial cell membrane. Nitrogen overlay keeps dissolved oxygen below 2 mg/L at filling. The solution is incompatible with polyvinyl chloride administration tubing containing plasticiser; low-density polyethylene or silicone tubing is used for drench set-up.