Effectiveness of antibacterial prophylaxis during induction chemotherapy in children with acute lymphoblastic leukemia.

BACKGROUND: Pediatric patients receiving induction chemotherapy for newly diagnosed acute lymphoblastic leukemia (ALL) are at high risk of developing life-threatening infections. We investigated whether uniform antibacterial guidelines, including mandatory antibacterial prophylaxis in afebrile patients during induction, decreases the incidence of microbiologically documented bacteremia. METHODS: Between 2012 and 2015, 230 patients with newly diagnosed ALL (aged 1-21) were enrolled on Dana-Farber Cancer Institute ALL Consortium Protocol 11-001 (DFCI 11-001). Induction therapy, regardless of risk group, included vincristine, prednisone, doxorubicin, methotrexate, and PEG-asparaginase. Afebrile patients received fluoroquinolone prophylaxis at the initiation of induction and those presenting with fever received broad-spectrum antibiotics; antibiotics were continued until blood count recovery. Rates of documented bacteremias and fungal infections on DFCI 11-001 were compared to those on the predecessor protocol (DFCI 05-001), which included the same induction phase without antibiotic prophylaxis guidelines. RESULTS: Sixty-six (28.7%) patients received fluoroquinolone prophylaxis, the remaining patients received broad-spectrum antibiotics. Twenty-four (36.4%) patients on prophylaxis developed fever and seven (10.6%) developed bacteremia. The overall rate of infection during induction on DFCI 11-001 was lower than on DFCl 05-001 (14.3% vs. 26.3%, P < 0.0001) due to a decreased rate of bacteremia (10.9% vs. 24.4%, P < 0.0001). The rate of fungal infections (4.8% vs. 3.6%) and induction death (0.9% vs. 2%) was not significantly different. CONCLUSION: For children with newly diagnosed ALL, uniform antibiotic administration until blood count recovery, including fluoroquinolone prophylaxis for afebrile patients, reduced the incidence of bacteremia during the induction phase. Larger, randomized studies should be performed to confirm these findings.

Inert plastics as indicators of physiological processes in the gastrointestinal tract of ruminants.

Various types of plastics with different physical properties have been useful in measuring rumination and passage events in the gastrointestinal tract (GIT) of ruminants. Plastic ribbons and monofilaments are available in different diameters, specific gravities and hardness and they can be cut to various lengths. Specific studies that are amenable to these materials include physical appetite control, regurgitation for rumination, passage from the rumen with or without rumination and passage through the entire GIT. Passage of particles through specific portions of the GIT can be measured in animals with various fistula preparations. The rumination of plastic ribbon in the rumen is similar to that of long forage. If the particle length is 7 cm or less, the particle can be regurgitated and produces normal rumination patterns. Movement of particles from one part of the rumen to another can be measured. Multiple sites can be studied in the same experiment by using particles of different colors. Isolating particles from ingesta or fecal residues usually starts with sieving to remove the small particles. Various subsequent separation schemes include flotation or sedimentation, air streams or acid digestion; when other methods fail, particles can be manually separated and counted. Plastic markers have several potential uses in ruminant research but they also have limitations. Because they are inert, they cannot undergo the hydration, density and size changes that occur with normal feed particles.

Efficiency of mastication in relation to hay intake by cattle.

Four dry Holstein cows and four hay levels (50, 75, 100 and 125% of NRC-recommended dry matter intake) were used to study the efficiency of mastication and rumination in relation to hay intake. The experimental design was a 4 x 4 Latin square with 7-day periods. Increased hay levels resulted in increased rumination time, eating time, number of rechewings and boluses. When corrected for cell wall constituents (CWC) intake, rumination time decreased as level of hay intake increased, while eating time increased. Consequently, total chewing time per kilogram CWC intake did not differ (P less than .05) with hay level. Results indicate that ingested roughages required a constant amount of trituration either by eating or by rumination. The amount of each fecal particle size fraction retained by four different sieve sizes, and the total of these larger particles (above .3 mm), did not differ (P greater than .05) among hay levels. Results suggest that acceptability of indigestible particles by the reticulo-omasal orifice was not affected by the amount of hay intake.

Physical parameters of fiber affecting passage from the rumen.

Our objective was to review the factors that affect fiber passage from the rumen. Rumen residence time and passage from the rumen are important in control of intake, digestibility, protein metabolism, and protein escape. Physical factors associated with particle size and particle specific gravity affect passage from the rumen. Although particles of 5 cm may pass through the reticulo-omasal orifice, most particles leaving the rumen are smaller than 1 mm. Polypropylene ribbon cut into 7-cm lengths, introduced into the rumen, markedly reduced intake and were ruminated to fine particle size before being passed. Materials with specific gravity less than 1.0 are ruminated extensively and are passed slowly. As specific gravity of plastic particles increase, rumination of particles is decreased and passage is increased. Particles with specific gravities between 1.17 and 1.42 pass most rapidly. Increasing specific gravities further results in a decline in passage and a further lowering of rumination of particles. Natural hay and fresh forages are hydrated in the rumen, which causes functional specific gravity to increase. Some factors that affect rate of change of functional specific gravity of forages have been investigated. Small particle size, autoclaved rumen fluid, buffer solutions, and specific salts increased the rate of change of functional specific gravity of particles. Understanding of these factors may enable us to make better decisions in managing ruminant productions systems.

Chewing efficiency and body size of kid goats.

Thirty-two observations were made on 27 goats (18 mature, nonlactating females and 9 doe kids) to study the relationship among metabolic body size (body weight X 75), cell wall constituent intake, and chewing efficiency. A jaw motion recorder determined the minutes spent eating and ruminating during 24 h. Greater cell wall intake increased the amount of cell wall chewed per minute. Body size was directly related to cell wall eaten and ruminated per minute. In 2- and 3-mo-old kids, incomplete development of rumen function and body size both appeared to affect chewing efficiency. The chewing efficiency of 9-mo-old kids resembled that of the mature goats after adjustments for body size. Because rumination time seldom exceeds 10 h per day, the efficiency with which the time available for rumination is used will affect intake.

Passage and rumination of inert particles varying in size and specific gravity as determined from analysis of faecal appearance using multicompartment models.

Plastic particles of defined length (2, 5 mm) and specific gravity (sp.gr. 1.10, 1.34, 1.77) were administered just before feeding into the reticulo-rumen of four cattle and four swamp buffaloes given a diet predominantly of rice straw ad lib. Simultaneously, doses of ground rice straw marked with Cr and Yb were likewise given. Plastic particles were recovered from faeces for 12 d after dosing, and divided into non-ruminated (NR) and ruminated (R) particles. Excretion data of plastic particles were interpreted using a four-pool model incorporating passage of NR (kp) and R from the reticulo-rumen, post-ruminal passage, rate of chewing (kr) and two lag times. An inverse relationship was found between kr and sp.gr. The kr was higher for 5 mm than that for 2 mm particles. In contrast, kp was greatest for particles of sp.gr. 1.34, with higher kp for 2 mm than for 5 mm particles. Rates of passage and rumination (kp, kr) were higher for buffaloes than for cattle. Rumination time was related to kr, most highly (r2 0.96) with kr of 2 mm, 1.10 sp.gr. particles. Fragmentation of 5 mm particles by rumination tended to increase the rate of passage from the rumen. Ruminal passage rates of Yb and Cr markers were poorly correlated with each other and with kp of any of the plastic markers. Reanalysis of published data from plastic particle studies supported the relationships between sp.gr., size, kp and kr.(ABSTRACT TRUNCATED AT 250 WORDS)

Mastication and rumination in relation to body size of cattle.

Effect of body size on number of minutes per kilogram cell wall constituents spent chewing during eating and ruminating was studied in a total of 59 mature animals including 18 Holstein cows, 12 Jersey cows, 6 Ayrshire cows, 11 Guernsey cows, and 12 steers. Larger animals were more efficient chewers, spending less time chewing per kilogram of ingested cell wall constituents. Body size accounted for 52% and differences of intake of cell wall constituents accounted for an additional 22% of variability of chewing time. Neither breed nor ambient temperature contributed significantly to explaining the variability. Size of fecal particles and amount of each size did not differ significantly for different body sizes. These results suggest that acceptability of particles to the reticulo-omasal orifice was not different for different body sizes. Correlation was nil between body size and speed of chewing.

Regression of brown adipose tissue mitochondrial function and structure in neonatal goats.

Rapidly regressing perirenal brown adipose tissue (BAT) of neonatal goats was studied to correlate changes in mitochondrial metabolism and thermogenic capacity with changes in mitochondrial structure. The alpha-glycerophosphate shuttle activity of perirenal BAT mitochondria declined 60% from birth to 6 days of age. Oxygen consumption and thermogenic capacity measured by ion conductance peaked at birth and declined to low levels at 6 days. Sample electron micrographs of perirenal BAT showed intact electron-dense mitochondria with many cristae and little matrix area at 2 days. However, by 6 days the mitochondria were very relaxed with large matrix area, few cristae, and observable degradation. These results indicate that the morphological changes exhibited by rapidly regressing goat's perirenal BAT in the 1st wk postpartum are accompanied by dramatic alterations in BAT mitochondrial function.