Application of reversed-phase liquid chromatography and prepacked C18 cartridges for the analysis of oxytetracycline and related compounds.

The reversed-phase (RP) chromatographic separation of oxytetracycline (OTC) 4-epioxytetracycline (4-epiOTC), alpha-apooxytetracycline (alpha-apoOTC), and beta-apooxytetracycline (beta-apoOTC) has been accomplished on an Inertsil C8 column at ambient temperature. Using the simplex method of solvent optimization, a 0.1 M ammonium acetate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (72.5:12.5:15, v/v/v) mobile phase was found to give excellent separation of the compounds. OTC, 4-epiOTC, alpha-apoOTC and beta-apoOTC were resolved in 35 min with calculated detection limits of 40, 20, 50 and 140 ng/ml, respectively. Solid-phase extraction (using RP C18 cartridges) of OTC and OTC degradation compounds from distilled water and porcine muscle was tested at four concentration levels ranging from 200 to 2000 ng/ml (g); overall mean recovery of OTC from distilled water and porcine tissue was greater than 90% and 70%, respectively.

Identification of psychrotrophic Micrococcaceae spp. isolated from fresh beef stored under carbon dioxide or vacuum.

Seventy-four Gram-positive, catalase-positive coccal strains were isolated from fresh beef stored under carbon dioxide (< 500 ppm O2) or vacuum for up to 15 weeks at 0, 2 or 4 degrees C. Isolates were identified using biochemical tests listed in several published protocols and the API Staph-Ident System. No isolates were identified as Staphylococcus aureus. Twenty-nine isolates were identified as Staphylococcus saprophyticus (five distinct groups), 24 isolates were identified as Staphylococcus gallinarum and 21 isolates were identified as Micrococcus varians. The staphylococcal isolates were coagulase-negative, non-hemolytic and novobiocin resistant. They produced acid from several carbohydrates under aerobic conditions, hydrolysed gelatin but not collagen, showed lipolytic activity and grew in 15% NaCl. The Micrococcus varians isolates also were salt-tolerant, produced acid only from glucose, fructose and galactose (two strains), and were resistant to lysozyme (1600 micrograms/ml). Lactic acid was the major end product of aerobic glucose metabolism. All S. saprophyticus and M. varians isolates tested contained cell wall fatty acids with chain length > or = C20:0.

Effect of lighting treatment on the productivity, health, behavior and sexual maturity of heavy male turkeys.

1. Turkey poults (1620) were used to compare the effects of three lighting programmes on heavy strain males reared to 188 d: constant light (24L:0D, CON); increasing light (6L:18D at 7 d gradually increasing to 20L:4D by 63 d, INC); a pattern identical to INC followed by a decrease in daylength from 84 d to 10L:14D at 112 d (DID). 2. Lighting affected growth pattern but had no effect on body weight at 118 d or overall food to gain ratio. 3. Both INC and DID lighting reduced overall mortality in comparison to CON light primarily because of a reduction in the incidence of skeletal disease and spontaneous cardiomyopathy. INC and DID lighting increased the incidence of cannibalism. 4. Turkeys given INC or DID lighting had a superior ability to walk in comparison to those birds given CON light. 5. INC and DID males stood, ate and drank more frequently, and sat less often than CON turkeys during behavioural observation. 6. There were no lighting effects on carcase composition except that INC and DID birds had heavier keel bones. The ultimate force per cm2 (stress) required to break femora was greater for turkeys given INC and DID lighting (P = 0.065). 7. Plasma testosterone concentrations at 117 d were 272.5, 115.2 and 29.5 pg/ml for turkeys given CON, INC and DID lighting, respectively (P = 0.072). Testosterone concentration was not related to growth rate.

Detachment ofPseudomonas fluorescens from biofilms on glass surfaces in response to nutrient stress.

The effects of glucose and nitrogen depletion on the colonization of glass Petri plates byPseudomonas fluorescens were studied in batch culture. Colonization of the surfaces was initiated before colonization of the bulk phase, and biofilm formation was observed. This resulted in an apparent lag in the batch growth curve for the cell suspension. The lag phase was an artifact caused by the partitioning of cells between the bulk and solid phase of the culture and was not due to a reduction in the growth rate of unattached cells. The specific growth rate of the unattached cells (0.331 hour(-1)) was almost twice that determined for the total population (0.171 hour(-1)). Consequently the growth rate of biofilm-forming bacteria cannot be determined in batch culture unless the growth of both attached and unattached cells is monitored, and batch growth curves may contain artifacts due to the formation and dispersion of biofilms. The depletion of either glucose or nitrogen led to the active detachment of cells from the biofilm. An increase in the hydrophobicity of unattached cells was noted on depletion of carbon. This increase was the result of emigration of cells from the surface into the bulk phase.

Evaluation of Four Media for Recovery of Heat-Stressed Streptococci.

Two strains of Streptococcus faecium and one strain of Streptococcus faecalis were subjected to heat stress in a ham broth and recovered on all purpose tween agar; deMan, Rogosa, Sharpe agar; tryptone-dextrose-yeast extract-meat extract-peptone agar; and tryptic soy agar. Survival curves for the organisms recovered on each agar were constructed and D values (death rates) were calculated. Differences in death rates were noted for each organism between different media. The greatest recovery of cells that had received sub-lethal heat treatment occurred using all purpose tween agar.

Microbiological Stability of Pasteurized Ham Subjected to a Secondary Treatment in Retort Pouches.

A ham processing procedure consisting of pasteurizing, packaging in retort pouches, and subjecting the hams to a secondary heat treatment was evaluated as a method of increasing microbial stability. Pasteurized hams reheated at 121°C for 10 min and stored at 1±1°C or 6±1°C showed no microbial growth after 6 or 12 months of storage. The number of microorganisms in pasteurized hams not receiving the secondary heat treatment ranged from 103/g to >108/g and from 102 to >108/cm2 on the surface after 3 to 5 months of storage. Pasteurized hams that had been inoculated with Clostridium sporogenes spores before pasteurization followed by a secondary heat treatment at 121°C for 10 min showed a delay in the occurrence of swollen packages when stored at room temperature compared to hams not receiving the secondary heat treatment. However, the secondary heat treatment did not prevent spoilage of hams. Ham that has not been treated to eliminate spores should be refrigerated.