Heat injury and repair in Campylobacter jejuni

Polyphosphate kinases modulate Campylobacter jejuni outer membrane constituents and alter its capacity to invade and survive in intestinal epithelial cells in vitro

Campylobacter jejuni is the most prevalent cause of bacterial gastroenteritis worldwide. Polyphosphate kinases 1 and 2 (PPK1 and PPK2) regulate several cellular processes, including the biosynthesis of the bacterial cell wall. Despite their importance, whether PPK1 and PPK2 modulate the composition of C. jejuni outer membrane constituents (OMCs) and consequently impact its interaction with host cells remains unknown. Our comparative analysis between C. jejuni wild type, Δppk1, and Δppk2 strains showed qualitative and quantitative differences in the total OMC composition among these strains. Importantly, these OMC variations observed on the C. jejuni polyphosphate kinase mutants are directly related to their capacity to invade, survive, and alter the immune response of intestinal epithelial cells in vitro. Specifically, sub-fractionation of the C. jejuni OMC indicated that OMC proteins are uniquely associated with bacterial invasion, whereas C. jejuni OMC proteins, lipids, and lipoglycans are all associated with C. jejuni intracellular survival. This study provides new insights regarding the function of polyphosphate kinases and their role in C. jejuni infection.

Stress, sublethal injury, resuscitation, and virulence of bacterial foodborne pathogens

Environmental stress and food preservation methods (e.g., heating, chilling, acidity, and alkalinity) are known to induce adaptive responses within the bacterial cell. Microorganisms that survive a given stress often gain resistance to that stress or other stresses via cross-protection. The physiological state of a bacterium is an important consideration when studying its response to food preservation techniques. This article reviews the various definitions of injury and stress, sublethal injury of bacteria, stresses that cause this injury, stress adaptation, cellular repair and response mechanisms, the role of reactive oxygen species in bacterial injury and resuscitation, and the potential for cross-protection and enhanced virulence as a result of various stress conditions.

Response of heat-shocked Vibrio parahaemolyticus to subsequent physical and chemical stresses

Vibrio parahaemolyticus foodborne strains 405, 556, and 690 and a V. parahaemolyticus chopping board isolate were heat shocked at 42 degrees C for 15, 30, or 45 min. Heat shock, regardless of heating periods tested, caused an increased demand for NaCl during recovery from heat injury. Further study with strain 690 and the chopping board isolate also revealed that heat shock generally increased the survival of the test organism during subsequent exposure to 47 degrees C, 20 ppm H202, and 8% ethanol and reduced the tolerance of the test organism to low temperatures (5 and -18 degrees C). The extent of the heat shock response of V. parahaemolyticus varied with strain and the duration of treatment. Furthermore, heat shock treatments in the present study caused the leakage of nucleic acids from V. parahaemolyticus cells. This effect was most pronounced with cells heat shocked at 42 degrees C for 45 min.

Development of a selective broth medium for the detection of injured Campylobacter jejuni by capacitance monitoring

The purpose of these studies was to develop a conductimetric method for the rapid detection of Campylobacter jejuni. Numerous basal medium components were analyzed to develop a growth-enhancing broth medium for detection of freeze-injured Campylobacter cells using a conductimetric system. The final medium was composed of a modified Campy-Line agar from which the agar and triphenyltetrazolium chloride were removed and the amino acid, L-arginine was added. Pure isolates of C. jejuni. (frozen and thawed to produce stressed cells) were utilized to test the detection methodology. Monitoring of significant changes in the capacitance signal was found suitable for detection of Campylobacter proliferation. Using stressed pure cultures, Campylobacter growth was repeatedly detected at very low inoculum levels (about one cell per well). There was a direct linear relationship between detection times (DTs) and the initial inoculum level. For example, using a single strain, the mean DT (n = 20) at the 10 CFU/ml inoculum level was 28.6 h, with 100% of the inoculated wells detecting. The mean DTs at the 100, 1,000, and 10,000 CFU/ml inoculum levels were 24.9, 21.4, and 17.0 h, respectively. This study demonstrates that conductimetric methods can be utilized for the rapid detection of C. jejuni.

The recovery of Arcobacter butzleri NCTC 12481 from various temperature treatments

AIMS

The aim of this study was to determine the growth and survival characteristics for Arcobacter butzleri NCTC 12481.

METHODS AND RESULTS

The temperature and pH growth ranges were 15-39 degrees C and pH 6.0-8.0, as determined using impedance microbiology. The maximum specific growth rate was 00.57 h(-1) at 30 degrees C, pH 7.0. Arcobacter butzleri harvested from the exponential phase was more resistant to heat treatment than stationary phase cells (D55 1.1 and 0.4 min, respectively). Fluorescent dye uptake, and the release of UV-absorbing material, increased in heat-treated cells. After 21 d storage at 4 and -20 degrees C, A. butzleri was recovered on blood agar, but not on the isolation media CAT or CCDA.

CONCLUSION

Arcobacter butzleri cells from the exponential phase were less heat sensitive than those from the stationary phase. The organism was able to survive cold storage for at least 3 weeks.

SIGNIFICANCE AND IMPACT OF THE STUDY

The growth and survival characteristics have been quantified thus providing a greater understanding of this newly emerging pathogen.

Survival and recovery of viable but noncultivable forms of Campylobacter in aqueous microcosm

Previous studies suggesting that the persistence of thermotolerant Campylobacter in water, especially as a viable but non-cultivable form (VNC), was involved in human campylobacteriosis, the capacities of survival and resuscitation of a significant collection of 85 strains in aqueous microcosms were investigated. Two-thirds of these strains (68%) were not detectable on agar medium after a stay of 14-21 days, whereas 21% reached this state before 14 days and 11% were non-cultivable after a stay of 21 days. Some strains remained cultivable after 35 days in a shaken aqueous microcosm and beyond 60 days without shaking. After 30 days, 51% of the non-detectable strains by conventional culture were recovered after injection in 9-day fertilised chicken eggs. A kinetic study showed that the age of the viable but non-cultivable forms and characteristics of the strains could explain the variations of recovery. These results suggest that viable but non-cultivable forms of Campylobacter could be a potential risk of colonisation of human or animals and that an embryonic factor seems to be essential to allow resuscitation.

Effect of low-osmolality nutrient media on growth and culturability of Campylobacter species

The growth and culturability of Campylobacter jejuni NCTC 11351 and other campylobacters were examined in media having different osmolalities at a range of temperatures (4, 25, and 42 degreesC). The medium osmolalities used ranged from the osmolality of full-strength nutrient medium (modified campylobacter broth having an osmolality of around 254 mosmol) down to 96 mosmol. The following two methods were used to produce media having different osmolalities: dilution of the nutrient medium with distilled water and reformulation of the medium such that the concentrations of various osmolytes were altered while the nutrient content of the medium was unchanged. The results obtained with the two experimental methods were similar, indicating that there was an osmotic threshold effect, such that none of the campylobacters examined (C. jejuni NCTC 11351 and ATCC 33291, Campylobacter lari, and Campylobacter coli) grew in media having osmolalities around 130 mosmol and at temperatures below at 42 degreesC. Conversely, growth occurred in media having osmolalities of around 175 mosmol and above. Osmolar concentrations can be expressed in terms of osmolarity or osmolality. Osmolality is easier to evaluate, is the more commonly used term, and was used in the current study. In nutrient media having low osmolalities (i.e., 130 mosmol and below), the number of CFUs per milliliter declined rapidly regardless of the temperature, and no cells were recovered after 24 h. However, at nongrowth temperatures (25 and 4 degreesC) in higher-osmolality media (175 mosmol and above) a significant population was recovered throughout the experiment (up to 96 h). In low-osmolality nutrient media, the cellular morphology was principally coccoid, while in the early stages of growth in full-strength media the morphology was predominantly rodlike. We propose that the formation of coccoid cells in these experiments was the result of osmotic stress in low-osmolality media. This osmotic effect was apparent regardless of the osmolyte used to reformulate the medium (NaCl, KCl, Na2SO4, NH4Cl, and glucose were used).

Pre-enrichment and enrichment methods for isolating small number of campylobacteria from contaminating flora

A method was developed to detect fewer than 100 CFU of campylobacteria from SIFF transport medium to which thawing drip from deep frozen broiler carcasses was added as a source of contamination and which was then stored at room temperature for 20 h. The method was made possible by using pre–enrichment in 1 % buffered peptone water under a microaerophilic atmosphere for 5 h at 43°C before selective enrichment either in brucella enrichment broth and on brucella blood selective agar supplemented with Skirrow antibiotics or in CCD enrichment broth and on blood free CCD selective agar. The other pre–enrichment broth studied was alkaline peptone water with reducing agents (RAPW) and the other enrichment broths and selective agars were Preston broth and agar, THAL broth and alkaline tryptose broth (ATB) and brucella agar with ATB antibiotics. Contaminating flora can be a problem when using enrichment broths and selective agars with limited antibiotic supplementation.

Methods for detecting and enumerating Campylobacter jejuni and Campylobacter coli in poultry

Methods, media, and biochemical tests for detecting, enumerating, isolating, and identifying Campylobacter jejuni and C. coli in foods are summarized with special consideration of poultry and poultry products. Information is drawn largely from the American Public Health Association Compendium of Methods for the Microbiological Examination of Foods and the US Food and Drug Administration Bacteriological Analytical Manual for Foods. Reference is also made to recently advanced techniques and procedures.

Assessment of in vivo revival, growth, and pathogenicity of Escherichia coli strains after copper- and chlorine-induced injury

Cells of one enteroinvasive and three enterotoxigenic strains of Escherichia coli were exposed to sublethal concentrations of copper and chlorine to produce 85 to 94% injury. Injured cells were intraluminally inoculated into ligated ileal loops of anesthetized mice, and injury was assessed at timed intervals. Substantial recovery (72-84%) of copper- and chlorine-injured cells was observed in the inoculated loops at 4 and 3 h, respectively. No appreciable increase in total numbers was observed during these time intervals. In vitro revival of copper-injured cells in phosphate-buffered saline alone after incubation at 35 degrees C for 4 h was not observed. However, a 60 to 70% revival occurred when 200 micrograms of protein per ml of mouse intestinal mucosal homogenate was incorporated into saline cell suspensions. The enterotoxigenic activity of copper-injured cells in rabbit ileal loops was somewhat reduced compared with that of chlorine-injured or uninjured cells. These results show that injured pathogenic E. coli cells can revive in the small intestine and appear to retain their enterotoxigenic activity.

A comparative study of the rod and coccoid forms of Campylobacter jejuni ATCC 29428

Coccoid forms in cultures of a strain of the enteric pathogen Campylobacter jejuni were investigated. A culture containing 100% coccoid forms was non-viable. Coccoid forms had a lesser content of cytoplasmic components and nucleic acids than rods of C. jejuni. During the conversion to coccoid forms nucleotides leaked from the cells. The results of treatments with ionic and non-ionic detergents, and lysozyme and ethylenediaminetetraacetic acid indicated a changed cell wall in coccoid forms compared with rods. Using rate-zonal centrifugation coccoid forms were found to be less dense than rods. The results of this study indicate that the coccoid form of C. jejuni ATCC 29428 is a degenerate cell form which is undergoing cellular degradation.

Sensitivity to bile salts of Shigella flexneri sublethally heat stressed in buffer or broth

Batch cultures of Shigella flexneri M4243 were grown at 37 degrees C in broth to early stationary phase, washed, and heated at 50 degrees C in 0.1 M phosphate buffer (pH 7.0). Cells were surface plated on a tryptic phytone glucose agar (TPGA), TPGA with 0.15 or 0.85% bile salts no. 3 (TPGA-BS 0.15 or TPGA-BS 0.85), or TPGA with 0.25 or 0.50% sodium deoxycholate (TPGA-DC 0.25 or TPGA-DC 0.50). Cells sampled after no heating produced colony counts on TPGA-BS 0.85 or on TPGA-DC 0.50 that were no more than about 0.5 log lower than for unheated cell samples plated on TPGA. Cells heated at 50 degrees C for 30 min produced colony counts on TPGA-DC 0.50 or on TPGA-BS 0.85 that were about 1.5 logs lower than on TPGA. Cells heated for 30 min and shifted to TPG broth at 37 degrees C to allow resuscitation required about 2 h to regain tolerance to 0.85% BS. However, heated cells resuscitated on solid TPGA at 35 degrees C before being challenged with overlays of TPGA-BS 0.85 or TPGA-DC 0.50 required 6 to 8 h on TPGA to regain tolerance to 0.85% BS or 0.50% DC. To regain tolerance to overlays of 0.15% BS or 0.25% DC, heated cells required resuscitation periods on TPGA of about 2 or 2 to 6 h, respectively. Cells heated in TPG broth and sampled after no heating produced colony counts on TPGA that were about 1.5 logs lower than for unheated cell suspensions, suggesting greater apparent injury when heat stressed in broth than in buffer.(ABSTRACT TRUNCATED AT 250 WORDS)