Physiological Activity of Campylobacter jejuni Far below the Minimal Growth Temperature

The behavior of Campylobacter jejuni at environmental temperatures was examined by determining the physiological activities of this human pathogen. The minimal growth temperatures were found to be 32 and 31°C for strains 104 and ATCC 33560, respectively. Both strains exhibited a sudden decrease in growth rate from the maximum to zero within a few degrees not only near the maximal growth temperature but also near the minimal growth temperature. This could be an indication that a temperature-dependent transition in the structure of a key enzyme(s) or regulatory compound(s) determines the minimal growth temperature. Oxygen consumption, catalase activity, ATP generation, and protein synthesis were observed at temperatures as low as 4°C, indicating that vital cellular processes were still functioning. PCR analysis showed that cold shock protein genes, which play a role in low-temperature adaptation in many bacteria, are not present in C. jejuni. The fact that chemotaxis and aerotaxis could be observed at all temperatures shows that the pathogen is able to move to favorable places at environmental temperatures, which may have significant implications for the survival of C. jejuni in the environment.     

Relationship between progesterone concentrations in milk and blood and time of ovulation in dairy cattle

The objective of this study was to investigate whether monitoring progesterone concentrations in milk and blood plasma can be used to predict time of ovulation in dairy cattle. Whole milk was sampled twice daily and blood samples were collected once a day before the morning milking. Ovulation was assessed by trans-rectal ultrasonography at 4h intervals beginning from the end of estrus. For a parameter to be useful as predictor for time of ovulation, it should be precise (i.e. variation between animals should not exceed 12h). In milk, progesterone concentration dropped <15 ng/ml at 97.7+/-17.8h (range: 54-126 h) before ovulation, to <5 ng/ml at 79.7+/-11.2h (range: 54-98) before ovulation to decline further to <2n g/ml at 70.7+/-16.8h (range: 38-90 h) before ovulation (n=20). In plasma, progesterone concentration dropped to <4ng/ml 90.5+/-19.6h (range: 66-138 h) before ovulation and to <2 ng/ml at 75.0+/-12.2 h (range: 50-98) before ovulation. These intervals were not influenced by parity, milk production or days in milk. In conclusion, monitoring of progesterone alone is not sufficient to predict ovulation because of the large variation in timing of decrease of progesterone concentrations relative to ovulation between animals. At best the range is about 2 days.     

Residual Viral and Bacterial Contamination of Surfaces after Cleaning and Disinfection

Environmental surfaces contaminated with pathogens can be sources of indirect transmission, and cleaning and disinfection are common interventions focused on reducing contamination levels. We determined the efficacy of cleaning and disinfection procedures for reducing contamination by noroviruses, rotavirus, poliovirus, parechovirus, adenovirus, influenza virus, Staphylococcus aureus, and Salmonella enterica from artificially contaminated stainless steel surfaces. After a single wipe with water, liquid soap, or 250-ppm free chlorine solution, the numbers of infective viruses and bacteria were reduced by 1 log₁₀ for poliovirus and close to 4 log₁₀ for influenza virus. There was no significant difference in residual contamination levels after wiping with water, liquid soap, or 250-ppm chlorine solution. When a single wipe with liquid soap was followed by a second wipe using 250- or 1,000-ppm chlorine, an extra 1- to 3-log₁₀ reduction was achieved, and except for rotavirus and norovirus genogroup I, no significant additional effect of 1,000 ppm compared to 250 ppm was found. A reduced correlation between reduction in PCR units (PCRU) and reduction in infectious particles suggests that at least part of the reduction achieved in the second step is due to inactivation instead of removal alone. We used data on infectious doses and transfer efficiencies to estimate a target level to which the residual contamination should be reduced and found that a single wipe with liquid soap followed by a wipe with 250-ppm free chlorine solution was sufficient to reduce the residual contamination to below the target level for most of the pathogens tested.     

Feeding level does not affect progesterone levels in intermittently suckled sows with lactational ovulation

The aim of this study was to examine whether the low post-ovulatory plasma P(4) levels found in intermittently suckled (IS) sows are related to the high feeding level during intermittent lactation. Multiparous sows (n=21) were separated from their piglets for 12h per day starting at day 14 of lactation until 6 days after ovulation. At day 28 of lactation, 9 sows had ovulated (spontaneous) and the remaining 12 sows were treated with PG600 (PG600-induced). At ovulation sows were allocated to either a high (H) feeding level (on average 6.5 kg) or a low (L) feeding level (high feeding level minus 2.5 kg) until 6 days after ovulation. Plasma P(4) levels were not affected by feeding level or type of ovulation (P>0.10), and neither were CL parameters, embryo survival rate and embryo development at day 30 of gestation. In conclusion, low levels of plasma P(4) were found in IS sows with lactational ovulation but these were not affected by feeding level during the first week after ovulation. Further studies are needed to investigate which factors cause the lower plasma P(4) levels in these sows.     

The use of latex agglutination tests for determining Campylobacter species

A comparison was made between three commercially available latex agglutination tests for the detection of Campylobacter. All tests showed clear agglutination with pure cultures of several Campylobacter strains in both the spiral and coccoid form. The Microscreen test was able to detect 10 times less cells than the Campyslide and Meritec tests. The latex tests were also applied to enrichment broth cultures of chicken products. Sixty-nine per cent of the Campylobacter positive enrichment broth cultures were positive with the Microscreen test. The Meritec test detected 63% of the positive samples. The Campyslide test detected only 15% of the positive samples and often showed non-specific agglutination.     

Temperature-dependent membrane fatty acid and cell physiology changes in coccoid forms of Campylobacter jejuni.

The effect of temperature and the availability of nutrients on the transition of spiral Campylobacter jejuni cells to coccoid forms was investigated. Ageing of spiral C. jejuni cells in either nutrient-poor or nutrient-rich environments resulted in the formation of nonculturable coccoid cells at 4, 12, and 25 degrees C after different periods, with the cells incubated at 4 degrees C in nutrient-deficient media remaining culturable the longest. To study the phenomenon, ATP levels, protein profiles, and fatty acid compositions were monitored under conditions where the transition from spiral to coccoid cells occurred. During storage, the levels of intracellular ATP were highest in cells incubated at low temperatures (4 and 12 degrees C) and remained constant after a small initial decrease. During the transformation from spiral to coccoid forms, no alteration in protein profiles could be detected; indeed, inhibition of protein synthesis by chloramphenicol did not influence the transition. Furthermore, DNA damage by gamma irradiation had no effect on the process. Membrane fatty acid composition of cocci formed at low temperatures was found to be almost identical to that of spiral cells, whereas that of cocci formed at 25 degrees C was clearly different. Combining these results, it is concluded that the formation of cocci is not an active process. However, distinctions between cocci formed at different temperatures were observed. Cocci formed at 4 degrees C show characteristics comparable to those of spirals, and these cocci may well play a role in the contamination cycle of C. jejuni.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intermittent suckling enables estrus and pregnancy during lactation in sows: effects of stage of lactation and lactation during early pregnancy

Previously we demonstrated that pre-ovulatory LH and post-ovulatory progesterone (P4) concentrations in plasma were low and embryo development was retarded when sows were induced to ovulate during lactation by submitting them to intermittent suckling (IS). The present study investigated whether this was due to: (1) stage of lactation when IS was initiated, and (2) continuation of IS post-ovulation. Multiparous Topigs40 sows were studied under three conditions: conventional weaning at Day 21 of lactation (C21; n = 30), intermittent suckling from Day 14 of lactation (IS14; n = 32), and intermittent suckling from Day 21 of lactation (IS21; n = 33). Sows were separated from piglets for 12 h daily during IS. IS sows were either weaned at ovulation or 20 d following ovulation. One-third (21/63) of the IS21 and C21 sows had already ovulated or had large pre-ovulatory follicles at Day 21 and were excluded from further study. Initiation of IS at Day 14 instead of Day 21 of lactation tended to reduce P4 at 7 d post-ovulation (P = 0.07), did not affect pregnancy rate, and tended to reduce embryo survival (P = 0.06). Continuation of IS during pregnancy resulted in lower P4 at 7 and 12 d post-ovulation, tended to reduce embryo weight and pregnancy rate (P < 0.10), whereas embryo survival was not affected. This study presents data for a population of sows in which follicle growth and ovulation are easily triggered under suckling conditions. Further, when these sows are bred during lactation, initiation of IS at 21 rather than 14 d of lactation with weaning at ovulation yields the most desirable reproductive performance.     

Campylobacter jejuni: a study on environmental conditions affecting culturability and in vitro adhesion/invasion

Aims:  Nongrowing cultures of Campylobacter jejuni lose their culturability. It is unclear whether this loss in culturability also affects their ability to interact with host cells. The purpose of this study was to determine the relevance of the number of culturable cells to the ability to adhere/invade in Caco-2 cells.
Methods and Results:  For C. jejuni C356, culturability and adhesion/invasion were monitored in time (days) under different storage conditions (temperature, medium, atmosphere). Decrease rates of both culturability and adhesion/invasion were dependent on the conditions used, but the number of adhering/invading cells per culturable cell was not affected by the environmental conditions. Furthermore five strains were monitored at one condition. The culturability and adhesion/invasion decrease rates did not significantly differ per strain; however the number of adhering/invading cells per culturable cell was strain dependent.
Conclusions:  Culturability and adhesion/invasion of C. jejuni are linearly related. The number of adhering/invading cells per culturable C. jejuni cell is strain dependent, but is not affected by environmental conditions.
Significance and Impact of the Study:  It was shown that the number of culturable cells is a good measure for the in vitro adhesion/invasion of. C. jejuni.     

Reproduction results and offspring performance after non-surgical embryo transfer in pigs

Increased interest in transfer of valuable genetic material around the world with minimal health risks has stimulated the development of non-surgical embryo transfer (nsET) technologies in pigs. Experimental evidence shows that nsET without sedation of the recipients is now feasible. The goal of this study, therefore, was to evaluate a method of nsET under commercial conditions. The experiment included 135 donor gilts and 45 multiparous recipient sows. Ovulation was induced in both donors and recipients, and nsET was performed using the Swinlet catheter. Donor gilts averaged 16.5 (7-45) corpora lutea, but this depended on age of the donor (P < 0.05). An average of 10.1 transferable blastocysts was recovered per donor, and the recovery rate was 84%. For 44 nsET, 14 recipients (31%) came into estrous before Day 23 after ovulation, 7 recipients (16%) came into estrous between Days 23 and 30, 3 recipients (6.8%) came into estrous between Days 39 and 48, 2 recipients (4.5%) had a late abortion. Finally, 18 of 44 recipients (41%) resulted in successful births, with an average liter size of 7.2 +/- 2.8. Birth weight of nsET piglets were 0.2 kg more than control piglets, but depended on litter size ((P < 0.05). The sex-ratio was not different from 50%. No anatomical abnormalities were observed in the offspring of nsET. Of the recipients that did not become pregnant from nsET, 91% became pregnant after insemination in the next estrous. Gilts born from nsET gave on average 12.4 +/- 3.0 total born piglets in their first pregnancy. In conclusion, the nsET procedure used in this study can be applied in practice without the need for special facilities, such as surgical and anesthesia equipment.     

Listeria monocytogenes: diagnostic problems

The first isolation methods for the detection of Listeria spp. were generally based on the direct culture of samples on simple agar media, but isolation of the pathogenic Listeria monocytogenes was difficult. In time, new techniques were developed, based on a variety of selective and elective agents in isolation and enrichment media, which gained better and quicker results. Current reference methods allow the recovery of L. monocytogenes from a variety of foods with relative ease. However, more comparative studies are needed to select one horizontal method. It is suggested that the procedure of the International Organization for Standardization is a good base for such comparisons.