Effectiveness of steam pasteurization in controlling microbiological hazards of cull cow carcasses in a commercial plant

The purpose of the study, carried out in a beef processing plant, was to evaluate the effectiveness of a new prototype for steam pasteurization treatment in controlling microbiological hazards. Samples were taken by swabbing randomly selected sites before and after pasteurization and again after chilling to obtain total aerobic counts (TAC), total coliform counts (TCC), and generic Escherichia coli counts (ECC) on Petrifilm plates and to determine the prevalence of Salmonella spp., Listeria monocytogenes, and E. coli O157:H7 using standard enrichment techniques. Escherichia coli and L. monocytogenes strains were tested for various factors associated with their virulence by using colony hybridization and polymerase chain reaction (PCR), respectively. Antimicrobial susceptibility was determined for each isolate that was potentially pathogenic to humans by using the disk-diffusion method. Mean values for TAC, TCC, and ECC were 2.18, 0.16, and 0.06 log10 CFU/cm2, respectively, before pasteurization; 1.17, 0.03, and 0.01 log10 CFU/cm2 after pasteurization; and 0.89, 0.02, and 0.01 log10 CFU/cm2 after chilling. Prevalence of L. monocytogenes, Salmonella spp., and E. coli O157:H7 on carcasses was 0.8%, 0.0%, and 0.0%, respectively, before pasteurization; 2.6%, 0.0%, and 0.0% after pasteurization; and 3.1%, 0.1%, and 0.0% after chilling. The prevalence of E. coli containing > or = 1 virulence gene was 14.7%. More specifically, 11.88% of the isolates obtained before pasteurization, 22.2% obtained after pasteurization, and 31.2% obtained after chilling had virulence genes. All L. monocytogenes isolates tested positive for the presence of 3 major virulence factors (hlyA, inlB, and plcB). Antibiograms showed that certain isolates were susceptible to all antibiotics, some showed an intermediate sensitivity, and others were multiresistant. Overall, these results suggest that steam pasteurization is an effective means of improving safety quality of beef carcasses. However, pasteurization may indirectly contribute to the growth of some pathogenic microorganisms, such as L. monocytogenes.     

Sheep as a new experimental host for Babesia divergens

Babesia divergens was cultivated in sheep erythrocytes in RPMI 1640 supplemented with 10% Fetal Calf Serum (FCS) or sheep serum. In vitro cultures in sheep red blood cells were initiated with human erythrocytes infected in vitro with B. divergens Rouen 1987 or with gerbil blood infected with several isolates from bovine origin. After the first subcultures on sheep erythrocytes, a ten-fold multiplication of the parasites was obtained within 48 h. Erythrocytes from three splenectomized sheep were infected in vitro with B. divergens; when parasitaemia reached 10%, the animals were inoculated with homologous parasitized erythrocytes. All sheep expressed hyperthermia with a peak between the 6th and the 9th day post-infection (p-i) and a transitory parasitaemia 10 days p-i. In vitro primary cultures were performed on two of these sheep, demonstrating the parasite persistence at very low parasitaemia in the infected animals. Splenectomized sheep can be used as a new model for B. divergens chronic infection.     

Direct and Specific Assessment of Colonisation of Wheat Rhizoplane by Pseudomonas fluorescens Pf29A

The efficacy of fluorescent pseudomonads as suppressors of soil-borne diseases is linked to their ability to colonise plant roots. Monitoring the dynamics of biocontrol agents in the rhizosphere should improve the irreliability. We designed a pair of Sequenced Characterised Amplified Region (SCAR) primers specific to Pseudomonas fluorescens Pf29A, based on a specific 700 bp RAPD product selected in a previous work. Primer specificity was tested with DNA samples extracted from rhizospheric soil and rhizoplane of wheat plants grown in two different non-sterile soils. We assessed the total population of Pf29A by PCR and the culturable population by counting a tetracycline-resistant Pf29A transformant producing Green Fluorescent Protein (GFP), on selective medium 5 days after inoculation of non-sterile soil. SCAR primers were specific for Pf29A in both soils. We evaluated the limit of detection to 14.2 fg of target DNA, equivalent to 242 Pf29A cells per cm of wheat root. Culturable populations of Pf29A transformant accounted for 13% and 4% of the total populations 5 days after treatment with 10³ and 10⁷ CFU of transformed Pf29A per gram of soil. The SCAR derived sequence is a good candidate to develop a strain specific and sensitive PCR-quantification of Pf29A available for population dynamic studies in fields. We confirm that only a small proportion of the total Pf29A rhizosphere population is culturable.     

Preventive effect of zinc against cadmium-induced oxidative stress in the rat testis

The aim of this study was to investigate the antioxidant role of zinc (Zn) in the Cd-exposed testes of Wistar rats. Subchronic exposure to Cd (CdCl(2), 40 mg/l, per os) for 30 days resulted in a significant reduction in growth rate (-11%) and relative weights of testes (-36%) and seminal vesicles (-80%). Treated rats displayed a decrease in testicular and plasma testosterone levels, respectively (-70%, P<0.05; -48%, P<0.05), epididymal sperm count (-22%, P<0.05), and spermatozoa motility (-35%, P<0.05). In contrast, Cd increased the malondialdehyde (+46%, P<0.05), metallothionein (+200%, P<0.05), and 8-oxodGuo concentrations (+71%, P<0.05) in the testis. In the gonad, Cd decreased the GPx (-30%, P<0.05), CAT (-32%, P<0.05), mitochondrial Mn-SOD (-34%, P<0.05), and cytosolic CuZn-SOD (-32%, P<0.05) activities. Zinc supplementation (ZnCl(2), 40 mg/l, per os) in the Cd-exposed rats restored the activities of GPx, CuZn-SOD, and Mn-SOD in the testes to the levels of the control group. Moreover, zinc administration was capable of reducing the elevated levels of malondialdehyde in the testis. Interestingly, zinc supplementation attenuated DNA oxidation induced by Cd in the gonad and restored the testosterone level and sperm count to the levels of the control group. Zinc administration minimized oxidative damage and reversed the impairment of spermatogenesis and testosterone production induced by Cd in the rat testis.     

Intraocular pharmacokinetics of intravenously administered marbofloxacin in rabbits with experimentally induced acute endophthalmitis

OBJECTIVE: To compare penetration of IV administered marbofloxacin in intraocular fluids of healthy and inflamed eyes in rabbits with endotoxin-induced endophthalmitis. ANIMALS: 35 pigmented rabbits. PROCEDURES: Endophthalmitis was induced in the right eye via intravitreal administration of Escherichia coli endotoxin. The left eye was a control eye. After 24 hours, a single dose of marbofloxacin (4 mg/kg, IV) was administered. Groups of rabbits (n = 5/group) were euthanized 0.5, 1, 2, 4, 6, 10, and 18 hours later, and blood and ocular fluids were collected. Marbofloxacin concentrations were determined via reverse-phase high-performance liquid chromatography, and pharmacokinetic analysis of the data was performed with a mono-compartmental model. RESULTS: Mean area under the aqueous concentration-time curve was significantly lower in control eyes (1.64 +/- 0.07 microg*h/mL) than in inflamed eyes (3.31 +/- 0.11 microg*h/mL). Similarly, drug penetration into aqueous humor was 33% and 65% for control eyes and inflamed eyes, respectively. Mean area under the vitreous humor concentration-time curve for control eyes(1.75 +/- 0.05 microg*h/mL) was significantly less than for inflamed eyes (2.39 +/- 0.16 microg*h/mL). In the vitreous humor, corresponding penetrations were 34% and 47%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Penetration of marbofloxacin into the aqueous and vitreous humor after IV administration was significantly enhanced by intraocular inflammation, suggesting a role for this antimicrobial in the prophylaxis or treatment of bacterial endophthalmitis caused by susceptible pathogens.     

Testing the efficacy of medium chain fatty acids against rabbit colibacillosis

Enteropathogenic Escherichia coli (EPEC) represents a major cause of lethal diarrhea in young mammals. Although the pathogenicity mechanisms of EPEC are now well understood, the intrinsic and environmental factors that control the expression of EPEC virulence remain largely unknown. In the rabbit, suckling reduces pups' sensitivity to EPEC infection. Hence, we have hypothesized that uncharacterized factors present in doe milk may mediate this protection. Medium chain fatty acids (MCFA), known to possess antimicrobial properties, are highly abundant in doe milk. We demonstrate that caprylic acid exhibits a clear bacteriostatic effect in vitro against the rabbit EPEC strain E22 (O103:H2:K-), in a dose-dependent manner. In vivo, the dietary inclusion of triglycerides of MCFA did not however reduce the sensitivity of young rabbits challenged with this EPEC strain. The mortality and fecal excretion of EPEC were not reduced, and the bacterial adhesion to ileum was not inhibited. Amount of MCFA reaching the ileal level might have been too low and/or their association to other milk antimicrobials may have been required to observe a positive effect on disease evolution in a context of a highly virulent challenge.     

EVALUATION OF CANINE LUMBOSACRAL STENOSIS USING INTRAVENOUS CONTRAST-ENHANCED COMPUTED TOMOGRAPHY

The objective of this study was to evaluate intravenous contrast-enhanced computed tomography as a technique for predicting the within-level location(s) of compressive soft tissues in the canine lumbosacral spine. Pre-operative intravenous contrast-enhanced computed tomography of the L5-S3 vertebral levels was performed in 12 consecutive large breed dogs with lumbosacral stenosis. The images were evaluated for enhancement of soft tissues by two radiologists who were unaware of the surgical findings. For each within-level location (dorsal canal, ventral canal, right lateral recess, left lateral recess) enhancement was classified as present, absent or equivocal. The results were compared with the results of surgical exploration and histopathology of excised tissues. The positive predictive values of intravenous contrast-enhanced computed tomography for compressive soft tissues involving the dorsal canal, ventral canal and lateral recesses were 83%, 100%, and 81% respectively. Negative predictive values for compressive soft tissues involving these locations were 29%, 50%, and 40% respectively.     

Efficacy of hexaflumuron against the fungus-growing termite Pseudacanthotermes spiniger (Sjöstedt) (isoptera,macrotermitinae)

The efficacy of hexaflumuron, a benzophenylurea insecticide, has been studied for the first time on a fungus-growing termite (Pseudacanthotermes spiniger Sjöstedt, Macrotermitinae). Results show that hexaflumuron could be useful in treating infestations of such pest species, which are of great economic importance in many tropical and equatorial countries. Foraging workers harvested and introduced treated food into the nest and subsequently contaminated the brood by trophallaxis. Hexaflumuron showed potent larvicidal activity. The compound did not appear to be rapidly degraded by the digestive enzymes of termite workers, nor by the symbiotic fungus Termitomyces eurhizus Heim growing on fungus combs. This chitin synthesis inhibitor did not act as a fungicide, since growth of the mycelium of this fungus was not inhibited in vitro. © 1998 Society of Chemical Industry     

Life history traits and trade-offs between two species of the ascochyta blight disease complex of pea

Plant disease complexes are a playground to investigate coinfections in natural or cultivated systems. Pathogens of such complexes may affect each other through direct and/or indirect interactions and lead to changes in virulence or aggressiveness, offspring production, and transmission. As coinfections by sympatric host-pathogens can strongly influence pathogen dynamics and their evolutionary trajectories, new insights into the mechanisms of their coexistence is thus of critical importance. In order to characterize differences in ecological niches liable to explain species coexistence on the same host, the inter- and intraspecific diversity of the life history traits in natural collections of the two main pathogens (Peyronellaea (formerly Didymella) pinodes [Dp] and Phoma medicaginis var. pinodella [Pmp]) of the ascochyta blight disease complex of pea was evaluated under controlled conditions. Dp strains developed 1.3 times faster and produced longer, mainly bicellular spores and in lower amounts (3.7 times less) than Pmp strains. Pmp strains were separated into two groups, one producing more pycnidiospores, mainly bicellular, with less resources, and the other with mainly unicellular ones. These three groups can be interpreted as three distinct life history strategies: pioneer colonizer (Dp), scavenger (large-spored Pmp), and intermediate (small-spored Pmp), allowing differentiation in access to and use of resources. While this experimental work provides new insight into coexistence of two species of the ascochyta blight disease complex of pea, it also raises the question of the benefit of having two distinct life history strategies for one species (Pmp).     

紫外吸收剂和游离基捕获剂对杨木APMP纸浆白度稳定效果的研究

高得率纸浆残余木质素中对紫外光和近紫外光高度敏感的特定化学的。结合大气中的氧分子,通过形成游离基中间体而产生发色物质,导致高得率纸浆的光返色（返黄）。紫外吸收类化合物、离基捕获呈抗氧剂等处理纸浆罅纸张返色的研究已有报道。本文研究了杨森ＡＰＭＰ纸浆手抄片添加紫外吸收类化合物、游离基捕获剂和抗氧剂等的工艺条件效果。结果Ｔｉｎｕｖｉｎ１１３０与脂肪醇混合物处理还原,纸浆抗光诱导返色效果尤为显著,该技术方