A prevalence survey for zoonotic enteric bacteria in a research monkey colony with specific emphasis on the occurrence of enteric Yersinia.

Transmissible pathogenic and opportunistic zoonotic enteric bacteria comprise a recognized occupational health threat to exposed humans from non-human primates (NHPs). In an effort to evaluate the occurrence of selected enteric organisms with zoonotic and biohazard potential in a research colony setting, we performed a prevalence study examining 61 juvenile and young adult rhesus macaques participating in a transplant immunology project. Primary emphasis was directed specifically to detection of pathogenic enteric Yersinia, less well-documented and reported NHP pathogens possessing recognized significant human disease potential. NHPs were surveyed by rectal culture during routine health monitoring on three separate occasions, and samples incubated using appropriate media and specific selective culture methods. Enteric organisms potentially transmissible to humans were subcultured and identified to genus and species. Significant human pathogens of the Salmonella/Shigella, Campylobacter, and enteric Yersinia groups were not isolated throughout the survey, suggesting prevalence of these organisms may generally be quite low.

A controlled trial of topical nitroglycerin in a New Zealand white rabbit model of brown recluse spider envenomation.

STUDY OBJECTIVES: Topical nitroglycerin has been reported to prevent skin necrosis from brown recluse spider bites, but this has never been scientifically tested. This study attempts to assess the effects of topical nitroglycerin on experimental Loxosceles reclusa envenomations. METHODS: We performed a randomized, blinded, controlled study in an animal care facility. Twenty-four New Zealand white rabbits were experimentally envenomated by means of subcutaneous injection with 20 microg of brown recluse spider venom. Rabbits were randomized to 1 of 2 experimental groups. The treatment group received 1 in of 2% topical nitroglycerin ointment every 6 hours for 3 days applied directly to the envenomation site. The control group received the vehicle without nitroglycerin. Gross examination of the lesions and measurements of the areas of the lesions were made daily. Creatine phosphokinase (CPK), blood urea nitrogen, creatinine, hemoglobin, and hematocrit levels were measured on days 0, 5, and 10. Lesions were excised after 10 days and examined by a blinded pathologist, who measured the area of necrosis and quantified inflammation and edema using a standard wound-healing score. For all values, mean values plus SD were determined. All comparisons made over multiple time points were assessed for significance by using a repeated-measures analysis of variance followed by Fisher least significant difference and Scheffé post hoc comparisons. A P value of.05 or less was used to determine significance. The Student's t test was used to compare the means of single measures. Significance was determined by using 95% confidence intervals. Comparisons of total area of necrosis were made with the nonparametric Mann-Whitney U test because of the heavy positive skew of the data. RESULTS: Skin necrosis developed in all animals. Mean values of the lesion area were not significantly different over time between the 2 groups of animals. At day 10, the median area of necrosis was 22.3 cm2 for the treatment group and 15.4 cm2 for the control group (P =.12). The inflammation score was 3.33+/-0.78 for the treatment group and 2.79+/-1.29 for the control group (P < .01). The edema score was 1.25+/-1.28 for the treatment group and 0.98+/-1.10 for the control group (not significantly different). CPK levels increased dramatically in both groups, with the greatest increase in the treatment group. In both groups hemoglobin and hematocrit levels decreased significantly, whereas WBC counts and platelet counts increased significantly, without significant differences between the 2 groups. CONCLUSION: At the dose used in this experiment, topical nitroglycerin did not prevent skin necrosis, increased inflammation score, and increased serum CPK levels. The results of this study do not support the use of topical nitroglycerin in the treatment of L reclusa envenomation and suggest that systemic toxicity could be increased.

IL-10 reduces Th2 cytokine production and eosinophilia but augments airway reactivity in allergic mice.

We investigated the effects of interleukin (IL)-10 administration on allergen-induced Th2 cytokine production, eosinophilic inflammation, and airway reactivity. Mice were sensitized by intraperitoneal injection of ragweed (RW) adsorbed to Alum and challenged by intratracheal instillation of the allergen. Sensitization and challenge with RW increased concentrations of IL-10 in bronchoalveolar lavage (BAL) fluid from undetectable levels to 60 pg/ml over 72 h. Intratracheal instillation of 25 ng of recombinant murine IL-10 at the time of RW challenge further elevated BAL fluid IL-10 concentration to 440 pg/ml but decreased BAL fluid IL-4, IL-5, and interferon-gamma levels by 40-85% and eosinophil numbers by 70% (P < 0.0001). Unexpectedly, the same IL-10 treatment increased airway reactivity to methacholine in spontaneously breathing mice that had been sensitized and challenged with RW (P < 0.001). IL-10 treatment in naive animals or RW-sensitized mice challenged with PBS failed to increase airway reactivity, demonstrating that IL-10 induces an increase in airway reactivity only when it is administered in conjunction with allergic sensitization and challenge. The results demonstrate that IL-10 reduces Th2 cytokine levels and eosinophilic inflammation but augments airway hyperreactivity. Thus, despite its potent anti-inflammatory activity, IL-10 could contribute to the decline in pulmonary function observed in asthma.

Oral administration of chitin down-regulates serum IgE levels and lung eosinophilia in the allergic mouse.

Previous studies showed that local macrophages phagocytose nonantigenic chitin particles (1-10 micrometer polymers of N-acetyl-d -glucosamine) through mannose receptors and produce IL-12, IL-18, and TNF-alpha. These cytokines lead to the production of IFN-gamma by NK cells. To determine whether chitin could down-regulate Th2 responses, chitin was given orally (8 mg/day for 3 days before and 13 days during ragweed allergen immunization) in BALB/c and C57BL/6 mice. These ragweed-immunized mice were given ragweed intratracheally on day 11. Three days after the challenge, the immunized mice with saline (controls) showed increases in serum IgE levels and lung eosinophil numbers. The chitin treatment resulted in decreases of these events in both strains. To dissect the inhibitory mechanisms of Th2 responses, spleen cells (4 x 106 cells/ml) isolated from the ragweed-immunized mice (controls) were cultured in the presence of ragweed and/or chitin for 3 days (recall responses). Ragweed alone stimulated the production of IL-4 (0.6 ng/ml), IL-5 (20 U/ml), and IL-10 (3.2 ng/ml), but not IFN-gamma. Ragweed/chitin stimulation resulted in significant decreases of IL-4, IL-5, and IL-10 levels and the production of IFN-gamma (48 U/ml). Moreover, spleen cells isolated from the chitin-treated mice showed ragweed-stimulated IFN-gamma production (15 U/ml) and significantly lower levels of the Th2 cytokines, suggesting that the immune responses were redirected toward a Th1 response. Collectively, these results indicate that chitin-induced innate immune responses down-regulate Th2-facilitated IgE production and lung eosinophilia in the allergic mouse.

Contaminated wounds: infection rates with subcutaneous sutures.

STUDY OBJECTIVE: To determine whether buried absorbable subcutaneous sutures (BASS) increase the infection rate in irrigated contaminated wounds. METHODS: This was a randomized, prospective trial in a rat model, with the histologist blinded to treatment group. A single 2-cm dorsal incision was made on each of 30 anesthetized 250-g Sprague-Dawley rats and inoculated with approximately 10(8) organisms of Staphylococcus aureus. After irrigation, 15 wounds were closed with running 4-0 nylon transdermal sutures, and 15 were closed with three interrupted 4-0 coated polyglactin 910 (Vicryl) subcuticular sutures (BASS) and running 4-0 nylon transdermal sutures. On day 7, wounds were scored on a scale of 0 to 3 in six categories: inflammatory infiltrates, fibroplasia and capillary proliferation, necrosis, exudates, giant cells, and edema. The possible range for the cumulative wound score was 0 (no inflammation) to 18 (severe inflammation and infection). RESULTS: The median total wound score in wounds closed with BASS was 14 (range, 7 to 16); it was 8 (range, 5 to 15) for wounds closed without BASS (P = .0004). The subscores for inflammation, necrosis, exudate, and edema were also significantly higher in wounds closed with BASS. CONCLUSION: BASS increase the infection rate and the degree of inflammation in contaminated wounds, despite through irrigation.

Subcuticular sutures and the rate of inflammation in noncontaminated wounds.

STUDY OBJECTIVE: To determine whether buried, absorbable, subcuticular sutures increase the degree of inflammation in noncontaminated wounds. DESIGN: Randomized, blinded, prospective trial. SETTING: Laboratory. PARTICIPANTS: Eleven Sprague-Dawley rats weighing 300 to 325 g. INTERVENTIONS: Four wounds were made on each rat. Two wounds on each were closed with three interrupted buried, absorbable, subcuticular sutures 6-0 polyglactin 910 and running 5-0 nylon skin sutures. The other two wounds were closed with running 5-0 nylon skin sutures alone. RESULTS: Fourteen days after the sutures were placed, the animals were killed, and histologic preparations were made from each wound. Each sample was scored on a scale of 0 to 3 for the presence of inflammatory infiltrates, fibroplasia and capillary proliferation, necrosis, exudates, giant cells, and edema. We determined a total wound score by adding the scores from each category. The mean total wound score was 4.46 +/- 2.92 for those closed with buried, absorbable, subcuticular sutures and 4.91 +/- 2.56 for those closed without buried, absorbable, subcuticular sutures. Using the Wilcoxon rank-sum test, we found no statistically significant difference in mean total wound score of wounds closed with and without buried, absorbable, subcuticular sutures (alpha = .01). The probability of detecting a twofold difference in total wound scores was 60% (beta = .40). CONCLUSION: Buried, absorbable, subcuticular sutures do not significantly increase the degree of inflammation in noncontaminated wounds.

Fever of unknown origin: due to C. albicans or other fungi acting on the hypothalamus?

Recently, it was shown that cerebrospinal fluid (CSF) contaminated with the fungus Trichosporon beigelii produces an intense fever when the organism is microinjected directly into the thermosensitive region of the anterior hypothalamic preoptic area (AH/POA). The purpose of this study was to determine if the AH/POA possesses a corresponding sensitivity to another fungal organism, Candida albicans. In adult male Sprague-Dawley rats, an intracerebral cannula was implanted stereotaxically above the AH/POA and a radio transmitter for the continuous recording of body temperature (Tb) was placed in the peritoneal cavity. After recovery, one of two solutions was microinjected in the AH/POA: a pyrogen-free, filtered artificial CSF and a second cultured with C. albicans in a concentration of approximately 12 x 10(8) organisms/ml. Whereas the filtered CSF failed to evoke a significant rise in Tb, C. albicans produced a febrile response of 0.8-1.5 degrees C in the rats within 1 h after its microinjection into the AH/POA. This fever persisted typically for > or = 12 h but after 24 h Tb returned to the baseline. Histological examination of the cerebral tissue postmortem revealed focally extensive granulomatous encephalitis with disseminated inflammation throughout the parenchyma of rats given repeated microinjections of C. albicans. Since C. albicans is a highly potent pyrogen acting directly on thermosensitive neurons, it is envisaged that a massive accumulation of the organism within the brain could be responsible pathologically for the protracted fever "of unknown origin" which gives rise to clinical morbidity.

Behavioral and physiologic effects of inapparent wound infection in rats.

There is a common notion that rats are resistant to postoperative wound infection because many recover from surgery performed under nonsterile conditions. As a result, nonaseptic surgical techniques are used commonly in rat surgery. Our aim was to determine if these techniques cause wound infection and, if so, whether or not the infection, inapparent to casual observation, creates measurable changes in rat physiology and behavior. Rats subjected to craniotomies or laparotomies and inoculated with 10(8) Staphylococcus aureus or Pseudomonas aeruginosa or sterile saline were tested for open-field activity, freezing behavior, home-cage behavior score, and wheel-running activity. Physiologic indices included lactate dehydrogenase, blood glucose, plasma fibrinogen, complete blood counts, wound bacterial counts and histology scores, body temperature, and body weight. Although no clinical signs were detected by postoperative observation, rats inoculated with bacteria were significantly less active in the open field and the duration of freezing behavior was shorter. Plasma fibrinogen, serum glucose, total white blood cell counts, and wound histology scores were significantly altered in the bacteria-inoculated rats. These findings underscore the need for sterile techniques in rat surgery to avoid confounding experimental data.