Under conditions of stress, cells of Campylobacter assume a coccoid shape that may be an evolutionary strategy evolved by the organism to enable survival between hosts. However, the physiology of Campylobacter as it devolves from spiral to coccoid-shaped morphology is poorly understood. In this study, conditions influencing the survival of Campylobacter jejuni ATCC 35921 in broth were determined. Cells in late log phase were resuspended in broth at 4 or 60 degrees C. The culturability of these cold- or heat-stressed cell suspensions was determined by spread plate counts and the activity of cells by the direct viable count technique and 5-cyano-2,3-ditolyltetrazolium chloride staining. C. jejuni changed form completely from culturable to viable but nonculturable cells (VBNC) within 25 days at 4 degrees C, and 15 min at 60 degrees C. Light microscopy of C. jejuni VBNC cells showed that the spiral-shaped cells became coccoid, and transmission electron microscopy of C. jejuni VBNC cells showed that the outer membrane was lost in aging cell suspensions. Furthermore, a limited proteomic study was carried out to compare C. jejuni proteins that exhibited increased or decreased synthesis on exposure to 60 degrees C.

Lauric acid and monolaurin in combination with lactic acid were evaluated for their effectiveness in reducing total plate count (TPC) and Staphylococcus aureus of fresh pork loin. Fresh pork loins were dipped in control (non treated), sterile distilled water, 3.2 mg/ml lauric acid, 0.4% (v/v) lactic acid, 0.2 mg/ml lauric acid + 0.1% (v/v) lactic acid, 0.1 mg/ml monolaurin, 0.05 mg/ml monolaurin + 0.1% (v/v) lactic acid solution. Total plate count, population of S. aureus and physical and sensory qualities were determined. TPC and S. aureus counts found in pork loin treated with lauric acid and monolaurin alone and in combination with lactic acid were not significantly different (P > 0.05). The colour, odour and overall acceptability of the pork loins were adversely affected by the treatment with lactic acid alone, but when combinations of the agents were used the sensory quality was acceptable. Furthermore, during storage, both lipids in combination with lactic acid controlled growth of S. aureus for 8 and 4 days of storage at 4 and 15°C respectively, and TPC for 8 and 2 days of storage at 4 and 15°C, respectively. The low pH of the antimicrobials caused the highest weight loss of range 4.41-5.38% drip loss, 22.56-23.35% cooking loss, and discolouration. In contrast, L * , PV, TBARS of pork in all treatments increased but shear force and a * decreased as storage was longer in all solution types (P < 0.05). However, for sensory acceptability, there was no loss of colour or adverse odour and the overall acceptability scores remained satisfactory.

The microaerophilic nature of Campylobacter jejuni has complicated its recovery from human and animal sources. In this study, enhancement of the growth and aerotolerance of C. jejuni ATCC 35921 in nutrient broth no. 2 (NB2) was investigated. The efficiency of recovery of C. jejuni in NB2 containing FBP (0.025% [each] ferrous sulfate, sodium metabisulfite, and sodium pyruvate), 5% laked horse blood, hemin, Oxyrase, or activated charcoal in an aerobic atmosphere was compared with that obtained under microaerophilic incubation. The shortest lag time (lamda) for cells grown aerobically was observed with NB2 supplemented with FBP, 5% laked horse blood, 0.01 g/liter of hemin, or 0.15 U/ml of Oxyrase. The efficacy of these media to resuscitate C. jejuni cells in late exponential phase, as well as cells subjected to stress induced by cold, heat, starvation, or acid, was determined in aerobic or microaerobic atmospheres. The h of cells grown aerobically in NB2 containing both FBP and blood was similar to that obtained in the same medium incubated in a microaerobic environment (P > 0.05). However, the X was longer during aerobic growth when low numbers of cells (approximately 1 log CFU/ml) in late exponential phase were used as the initial inoculum. The best recovery of stressed C. jejuni was observed in NB2 supplemented with FBP and blood and incubated aerobically. Enrichment in media incorporating FBP and 5% laked horse blood is a simple, convenient, and time-saving method to replace microaerophilic incubation methods for the resuscitation of C. jejuni.

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