Sequestering agents bind dietary aflatoxin B1 (AFB1) and reduce absorption from an animal's gastrointestinal tract. As a result, they protect an animal from the toxic effects of AFB1 and reduce transfer of the metabolite, aflatoxin M1 (AFM1), into milk. Three experiments, using late-lactation Holstein cows fed AFB1-contaminated feed, were conducted to evaluate several potential sequestering agents for their abilities to prevent or reduce the transmission of AFM1 into milk. Six agents previously tested in our laboratory for AFB1 binding in vitro were evaluated in these experiments. These were: SA-20, an activated carbon (AC-A); Astra-Ben-20, a sodium bentonite (AB-20); MTB-100, an esterified glucomannan (MTB-100); Red Crown, a calcium bentonite (RC); Flow Guard, a sodium bentonite (FG); and Mycrosorb, a sodium bentonite (MS). Five of the six sequestering agents significantly (P < 0.01) reduced AFM1 contamination of milk (AB-20, 61%; FG, 65%; MS, 50%; MTB-100, 59%; and RC, 31%); whereas, AC-A, activated carbon, had no effect on AFM1 transmission at 0.25% of feed. By the first milking (1 day after cows consumed contaminated feed), AFM1 appeared in milk, then reached maximum levels after three days, and was absent from milk within four days after AFB1 was removed from the feed. Sodium bentonites at 1.2% of feed showed good potential as AFB1 binders; MTB-100, a yeast cell wall product, was equally effective at 0.05% in feed. Potential AFB1 binding agents should be evaluated experimentally to demonstrate efficacy. Our data show that sequestering agents can reduce AFM1 in milk of cows fed AFB1-contaminated feed.

This outbreak of listeriosis was caused by noncommercial, fresh, Mexican-style cheese made from contaminated raw milk traced to 1 local dairy. We recommend educating Hispanic women about food safety while they are pregnant, enforcing laws that regulate the sale of raw milk and dairy products made by unlicensed manufacturers, making listeriosis a reportable disease in all states, routinely interviewing case patients, and routinely subtyping clinical L. monocytogenes isolates.

Eight bull calves (four Holsteins and four Ayrshire calves with mean birth weight of 38.8 kg) were ruminally cannulated at 3 d of age and allocated to one of two weaning programs. All calves were fed colostrum for 3 d after birth and milk until weaning. Calves in the conventional-weaning program were fed a starter diet from 3 d of age and weaned at 6 wk of age. In the early-weaning program, calves were fed a highly palatable pre-starter diet from 3 d of age until they consumed 227 g/d, and then fed a mixture of pre-starter (227 g) and starter diet ad libitum. Calves in this group were weaned at 4 wk of age. Ruminal samples were collected at 3 and 7 d, then weekly thereafter through 8 wk and at 10 and 12 wk of age to assess microbial activity. Calves in the early-weaned group had a higher concentration of total ruminal volatile fatty acids at an earlier age than the calves in the conventional-weaning program. This was accompanied by a trend toward higher lactate concentrations and lower ruminal pH in the early-weaned group during their first 4 wk of age. Lactate and ammonia concentrations decreased with calf age. The total anaerobic bacterial counts increased slightly with calf age, whereas Streptococcus bovis and facultative bacterial populations decreased with calf age. Amylolytic, proteolytic, lactobacilli, lactate-utilizers, cellulolytic and methanogenic bacterial populations increased progressively in both groups. Cellulolytic and methanogenic bacteria were present in both groups at 3 d of age. No protozoa were detected in calves of either group. In general, the most significant changes in bacterial populations and metabolic activity in both groups occurred between 4 and 6 wk of age. Although calves in both groups had similar patterns of bacterial development, calves in the early-weaning program tended to have high ruminal microbial activity at an earlier age than the conventionally weaned calves.

Bacteroides thetaiotaomicron can utilize amylose, amylopectin, and pullulan as sole sources of carbon and energy. The enzymes that degrade these polysaccharides were found to be primarily cell associated rather than extracellular. Although some activity was detected in extracellular fluid, this appeared to be the result of cell lysis. The cell-associated amylase, amylopectinase, and pullulanase activities partitioned similarly to the periplasmic marker, acid phosphatase, when cells were exposed to a cold-shock treatment. Two other enzymes associated with starch breakdown, at-glucosidase and maltase, appeared to be located in the cytoplasm. Intact cells of B. thetaiotaomicron were found to bind '4C-starch. Binding was probably mediated by a protein because it was saturable and was decreased by treatment of cells with proteinase K. Results of competition experiments showed that the starch-binding proteins had a preference for maltodextrins larger than maltohexaose and a low affinity for maltose and maltotriose. Both the degradative enzymes and starch binding were induced by maltose. These findings indicate that starch utilization by B. thetaiotaomicron apparently does not involve secretion of extracellular enzymes. Rather, binding of the starch molecule to the cell surface appears to be a first step to passing the molecule through the outer membrane and into the periplasmic space.

Mutagenesis of Bacteroides thetaiotaomicron with the transposon Tn4351 produced five classes of mutants that were not able to grow on amylose or amylopectin. These classes of mutants differed in their ability to grow on maltoheptaose (G7) and in the level of starch-degrading enzymes produced when bacteria were grown on maltose. All of the mutants were deficient in starch binding. Since one class of mutants retained normal levels of starch-degrading enzymes, this indicates that binding of the starch molecule by a cell surface receptor is necessary for starch utilization by B. thetaiotaomicron. Analysis of a starch-negative mutant that grew on G7 indicated that B. thetaiotaomicron possessed two starch-binding components or sites. One component (site A), apparently missing in this mutant, had an absolute preference for larger starch oligomers, whereas the other component (site M) also had a high affinity for maltodextrins (G4 through G7). Mutants not able to grow on maltodextrins (>G4) probably lacked both of these binding components. Only one class of mutants did not grow normally on maltose, but instead had a 4-to 5-h lag on maltose and a slower growth rate than the wild type. This class of mutants did not produce any of the starch-degrading enzymes or bind starch, even when growing on maltose. Such a phenotype probably resulted from transposon inactivation of a central regulatory gene or a gene encoding an enzyme that produces the inducer. The fact that both the degradative enzymes and the starch-binding activity were affected in this mutant indicates that genes encoding the cell surface starch-binding site are under the same regulatory control as genes encoding the enzymes.Bacteroides thetaiotaomicron, a gram-negative, obligate anaerobe that is normally found in the human colon, can utilize three types of starch: amylose, amylopectin, and pullulan. In the accompanying paper (1), we showed that the starch-degrading enzymes were mainly cell associated rather than extracellular. We also demonstrated that intact cells of B. thetaiotaomicron could bind starch. Starch-binding sites were saturable, and binding was decreased when cells were treated with proteinase K. The genes encoding the starchbinding components, like the genes encoding the degradative enzymes, were induced by maltose. These results indicated that the first step in starch utilization is the binding of starch to the cell surface. Presumably, starch is then passed through the outer membrane and brought into contact with degradative enzymes in the periplasmic space.However, demonstrating that starch is bound by intact bacteria, apparently involving a receptor-mediated step, does not prove that binding is necessary for starch utilization. To obtain evidence that binding is involved in starch utilization, it was necessary to find mutants that are unable to utilize starch because they cannot bind starch. Since starch-binding sites had a preference for long-chain maltodextrins (1), such mutants should still be able to utilize maltose and perhaps short-chain...

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in both human and veterinary medicine. The importance of companion animals as reservoirs of human infections is currently unknown. The companion animals of 49 MRSA-infected outpatients (cases) were screened for MRSA carriage, and their bacterial isolates were compared with those of the infected patients using Pulsed-Field Gel Electrophoresis (PFGE). Rates of MRSA among the companion animals of MRSA-infected patients were compared to rates of MRSA among companion animals of pet guardians attending a “veterinary wellness clinic” (controls). MRSA was isolated from at least one companion animal in 4/49 (8.2%) households of MRSA-infected outpatients vs. none of the pets of the 50 uninfected human controls. Using PFGE, patient-pets MRSA isolates were identical for three pairs and discordant for one pair (suggested MRSA inter-specie transmission p-value = 0.1175). These results suggest that companion animals of MRSA-infected patients can be culture-positive for MRSA, representing a potential source of infection or re-infection for humans. Further studies are required to better understand the epidemiology of MRSA human-animal inter-specie transmission.

SUMMARYThe daily progression of the 2006 (January-June) Nigerian avian influenza (AI H5N1) epidemic was assessed in relation to both spatial variables and the generation interval of the invading virus. Proximity to the highway network appeared to promote epidemic dispersal : from the first AI generation interval onwards >20 % of all cases were located at <5 km from the nearest major road. Fifty-seven per cent of all cases were located f31 km from three highway intersections. Findings suggest that the spatial features of emerging infections could be key in their control. When the spatial location of a transmission factor is well known, such as that of the highway network, and a substantial percentage of cases (e.g. >20 %) are near that factor, early interventions focusing on transmission factors, such as road blocks that prevent poultry trade, may be more efficacious than interventions applied only to the susceptible population.

Eight neonatal bull calves were rumen fistulated and assigned to one of two weaning programs to study the effect of diet and weaning age on ruminal metabolic development. All calves were fed colostrum until 3 d of age and milk until weaning. Calves in the early weaning program were fed milk and a highly palatable, prestarter diet until they consumed 227 g/d and then a mixture of 227 g of prestarter and all the starter diet they would eat. Calves in this group were weaned at 4 wk of age. Calves in the conventional weaning program were fed milk and a starter diet and weaned at 6 wk of age. Eight ruminal samples were collected over 12 h from each calf at 1, 4, 8, and 12 wk of age. Ruminal fluid samples were analyzed for pH, VFA, NH3 N, and L(+)-lactate and D(-)-lactate concentrations. Calves weaned early had lower ruminal pH, higher total VFA concentration, and higher molar proportion of butyrate than conventionally weaned calves. Ruminal NH3 N and lactate concentrations were not significantly affected by the weaning program, although lactate tended to be higher in calves weaned early. Ruminal VFA concentration increased and NH3N concentration decreased with increased feed consumption by calves in both groups. Molar proportions of acetate, isobutyrate, and isovalerate decreased, and those of propionate increased with age in both groups. Apparently, ruminal metabolic development, as evidenced by changes in fermentation products, was faster in calves weaned early than in calves weaned conventionally.