Effect of incubation atmosphere and temperature on isolation of Campylobacter jejuni from human stools

The HtrA protease of Campylobacter jejuni is required for heat and oxygen tolerance and for optimal interaction with human epithelial cells

Campylobacter jejuni is a predominant cause of food-borne bacterial gastroenteritis in the developed world. We have investigated the importance of a homologue of the periplasmic HtrA protease in C. jejuni stress tolerance. A C. jejuni htrA mutant was constructed and compared to the parental strain, and we found that growth of the mutant was severely impaired both at 44 degrees C and in the presence of the tRNA analogue puromycin. Under both conditions, the level of misfolded protein is known to increase, and we propose that the heat-sensitive phenotype of the htrA mutant is caused by an accumulation of misfolded protein in the periplasm. Interestingly, we observed that the level of the molecular chaperones DnaK and ClpB was increased in the htrA mutant, suggesting that accumulation of non-native proteins in the periplasm induces the expression of cytoplasmic chaperones. While lack of HtrA reduces the oxygen tolerance of C. jejuni, the htrA mutant was not sensitive to compounds that increase the formation of oxygen radicals, such as paraquat, cumene hydroperoxide, and H2O2. Using tissue cultures of human epithelial cells (INT407), we found that the htrA mutant adhered to and invaded human epithelial cells with a decreased frequency compared to the wild-type strain. This defect may be a consequence of the observed altered morphology of the htrA mutant. Thus, our results suggest that in C. jejuni, HtrA is important for growth during stressful conditions and has an impact on virulence.

Diverse roles for HspR in Campylobacter jejuni revealed by the proteome, transcriptome and phenotypic characterization of an hspR mutant

Campylobacter jejuni is a leading cause of bacterial gastroenteritis in the developed world. The role of a homologue of the negative transcriptional regulatory protein HspR, which in other organisms participates in the control of the heat-shock response, was investigated. Following inactivation of hspR in C. jejuni, members of the HspR regulon were identified by DNA microarray transcript profiling. In agreement with the predicted role of HspR as a negative regulator of genes involved in the heat-shock response, it was observed that the transcript amounts of 13 genes were increased in the hspR mutant, including the chaperone genes dnaK, grpE and clpB, and a gene encoding the heat-shock regulator HrcA. Proteomic analysis also revealed increased synthesis of the heat-shock proteins DnaK, GrpE, GroEL and GroES in the absence of HspR. The altered expression of chaperones was accompanied by heat sensitivity, as the hspR mutant was unable to form colonies at 44 degrees C. Surprisingly, transcriptome analysis also revealed a group of 17 genes with lower transcript levels in the hspR mutant. Of these, eight were predicted to be involved in the formation of the flagella apparatus, and the decreased expression is likely to be responsible for the reduced motility and ability to autoagglutinate that was observed for hspR mutant cells. Electron micrographs showed that mutant cells were spiral-shaped and carried intact flagella, but were elongated compared to wild-type cells. The inactivation of hspR also reduced the ability of Campylobacter to adhere to and invade human epithelial INT-407 cells in vitro, possibly as a consequence of the reduced motility or lower expression of the flagellar export apparatus in hspR mutant cells. It was concluded that, in C. jejuni, HspR influences the expression of several genes that are likely to have an impact on the ability of the bacterium to successfully survive in food products and subsequently infect the consumer.

Comparison of a novel microaerobic system with three other gas-generating systems for the recovery of Campylobacter species from human faecal samples

Three commercial gas-generating systems--CampyGen (Oxoid, UK), Oxoid BR56 (Oxoid, UK), and CampyPak Plus (Becton Dickinson, USA)--and the evacuation replacement technique were compared for the recovery of Campylobacter spp. from 500 human faecal samples collected from patients with gastroenteritis. Four hundred fifty faecal samples were tested upon receipt in the laboratory. Fifty faecal samples that had been previously found to be positive for Campylobacter spp. were tested retrospectively; these had been stored at 4 degrees C for more than 48 h. A total of 41 (9.1%) of the fresh faecal samples and 41 of 50 (82%) of the stored faecal samples were positive for thermophilic campylobacters. The CampyGen, the Oxoid BR56, the CampyPak Plus, and the evacuation replacement system detected Campylobacter spp. in 40 (97.6%), 39 (95.1%), 41 (100%), and 41 (100%) of the positive fresh faecal samples and in 37 (90.2%), 40 (97.6%), 39 (95.1%), and 40 (97.6%) of the stored samples, respectively. There was no statistical difference in performance of any of the four gas systems used (p = 0.98; chi-square test). Eighty-six percent of the isolates were Campylobacter jejuni and 14% were Campylobacter coli. Biotyping and phage typing of the isolates demonstrated that they were of a diverse range of subtypes. This study demonstrates that thermophilic campylobacters can be isolated from human diarrhoeal faecal samples using any of the four microaerobic-atmosphere-generating systems.

Campylobacter bacteremia: clinical experience with three different blood culture systems at Mayo Clinic 1984-1990

The efficiency of three commercially available blood culture systems for isolating Campylobacter sp. was investigated. Thirteen of 189,688 blood cultures from patients seen at the Mayo Clinic from 1984 through 1990 were positive for Campylobacter sp. Eleven out of 13 blood cultures positive for Campylobacter sp. were part of a complete three bottle set of cultures (Isolator from Du Pont, Roche Septi-Chek from Hoffman-La Roche, and non-vented Tryptic Soy Broth from Difco), none of them providing a specific microaerophilic mileu. The aerobic Roche Septi-Chek seems to be more efficient for the detection of Campylobacter sp. in blood cultures than either the anaerobic Tryptic Soy Broth (Difco) or the Isolator (Du Pont) using the incubator condition of 5% CO2.

Comparison of different procedures, transport media, and enrichment media for isolation of Campylobacter species from healthy laying hens and humans with diarrhea

A comparison was made with some of the available transport and enrichment media for the isolation of Campylobacter species. The merits of duplicate versus single sampling were also investigated. Fecal samples from 721 healthy laying hens and 328 patients with diarrhea were included in the study. The media compared were modified Stuart medium, Campythio-glycolate medium, semisolid motility test medium, and Campylobacter enrichment broth. The isolation rate of Campylobacter species was significantly increased by taking duplicate instead of single samples. The highest outcome was found when one of the two samples was an enrichment medium, such as semisolid motility test medium.

Viable but nonculturable stage of Campylobacter jejuni and its role in survival in the natural aquatic environment

Conditions influencing the survival of Campylobacter jejuni in the natural aquatic environment have been determined. Release of Campylobacter spp. into natural waters by animal hosts is postulated to play a key role in the maintenance of viability and transmission of the organism in the environment. Laboratory flask microcosms containing filter-sterilized stream water were used to test C. jejuni for the ability to remain viable in simulated natural systems. The microcosms were compared with the biphasic and shaking broth procedures used routinely for growth of Campylobacter spp. in the research laboratory. The stream-water microcosms were analyzed to determine effects of temperature and aeration on the survival of a well-characterized C. jejuni strain isolated originally from a human campylobacteriosis patient. Morphological characteristics were evaluated by phase-contrast microscopy and scanning or transmission electron microscopy. Survival curves were quantified on the basis of plate counts, epifluorescent microscopy, optical density measurements, and direct viable counts associated with protein synthesis in the absence of DNA replication. A significant difference was observed between results of direct enumeration, i.e., direct viable counts or acridine orange direct counts, and those from spread plate cultures. In all cases, increasing temperature of cultivation resulted in decreased recoverability on laboratory media, due possibly to an increased metabolic rate, as analyzed by CO2 evolution in the presence of radiolabeled glutamate. Stream water held at low temperature (4 degrees C) sustained significant numbers of campylobacters for greater than 4 months. Microcosms, aerated with shaking, exhibited logarithmic decline in recoverable C. jejuni, while stationary systems underwent a more moderate rate of decrease to the nonculturable state.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of pathogenic Campylobacter species in blood culture systems

Because differences in recognition of Campylobacter fetus and Campylobacter jejuni in systemic infections may be due partially to differences in the ability to cultivate these organisms, we studied their growth characteristics in two widely used blood culture systems. In the Roche Septi-Chek system (Hoffman-La Roche, Inc., Nutley, N.J.), over a broad range of inocula all strains were detected in broth within 2 days and on paddles within 3 days. In the BACTEC 6B aerobic bottles (Johnston Laboratories, Inc., Towson, Md.), C. jejuni and C. fetus took a median of 5 and 3 days, respectively, to reach the growth index threshold. However, in the BACTEC 7D anaerobic bottles, C. fetus required a median of 2 days to reach the growth index threshold, whereas for C. jejuni the median was greater than 10 days. The poor performance of C. jejuni in both BACTEC systems may have been due to unfavorable incubation atmospheres and may partially explain why C. jejuni bacteremia is so infrequently detected. Overall, the Roche Septi-Chek system was excellent for detecting Campylobacter strains in blood cultures.