Preliminary report on the results of the second phase of a round- robin endotoxin assay study using cotton dust

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Utilization of substrates by bacterial communities (biofilm) as they develop on stored chicken meat samples

Understanding and controlling the metabolic processes of microorganisms associated with chicken meat can lead to safer poultry products with a longer shelf life. The objective of the present study was threefold: 1) to determine the feasibility of using 96-well Biolog GN microtiter plates to assess substrate utilization profiles of bacterial communities (biofilm) as they develop on poultry products, 2) to identify substrates metabolized by microbial populations associated with stored chicken meat, and 3) to compare the substrate utilization profiles of biofilm communities as they develop on meat stored at 4 C (refrigeration temperature) for up to 5 d or at 13 C (a temperature common in poultry processing areas) for 2 d. The protocol used herein for preparing inocula for microplates was acceptable for the collection of optical density values (590 nm) in microplate wells as an indicator of microbial substrate utilization over time. Data from treatment of chicken meat samples using this protocol indicate that most of the 95 substrates tested were metabolized by microbial communities present as early as 1 d after storage at 4 or at 13 C. However, the rapidity (incubation time required for initial substrate utilization) and frequency (percentage of plates positive for transformation of an individual substrate) of metabolism of the substrates by the biofilm communities varied from 4 to 164 h of plate incubation and from 17 to 100% of microplates, respectively. At 13 C, polymers were the most rapidly metabolized substrate group, followed by carbohydrates, carboxylic acids, miscellaneous or amino acids, and amides or amines. Initial utilization of these substrate groups at 4 C occurred within a consistently shorter period (24 h of plate incubation). The frequency of metabolism of each individual substrate group varied only 3 to 16% between samples stored at 4 and 13 C. However, a greater difference in frequency of utilization of some individual substrates was noted. Such divergences may be useful in characterizing biofilm communities implicated in pathogenicity or affecting food quality of poultry products.

Temperature and flow rate effects on mass median diameters of thermally generated malathion and naled fogs

The effects of temperature and flow rate on mass median diameters (mmds) of thermally generated aerosol clouds were studied. Number 2 fuel oil alone, undiluted and diluted malathion 91, and undiluted naled were examined. There was a significant flow rate x temperature interaction on the mmds of diluted malathion fogs: i.e., differences among flow rates depended on temperature and vice versa.

A comparison of Teflon slides and the Army Insecticide Measuring System for sampling aerosol clouds

The effects of method of droplet analysis, reader of Teflon slides and distance on mass median diameter of a Cythion aerosol cloud were examined in the calibration of an Army Insecticide Measuring System (AIMS). There were no significant differences in results among readers and between the AIMS and readers. There were slight but statistically significant differences between readers of Teflon slides and between the methods of analysis. Data supports the manufacturer's recommendation that, for the AIMS, the distance at which an aerosol generator air blast is between 3 and 7 m3 s-1 must be determined.

Malathion aerosol cloud behavior in a Coastal Plains pine flatwoods

The study examines malathion aerosol cloud behavior in a North Florida pine flatwoods. Droplet mass median diameters (MMD) decreased over distance in both open and pine flatwoods. A sharp decrease in number of aerosol droplets per cm2 occurred between 3.1 and 15.2 m and a gradual decline in droplets per cm2 occurred beyond 15.2 m in both treatment areas. There were no interactions between habitat and distance in regard to MMD or droplets per cm2. Analysis of variance models accounted for 82% of the variability in the MMD data and 79% of the variability in the number of droplets per cm2.

Development of Statistical Models to Simulate the Testing of Farmers Stock Peanuts for Aflatoxin Using Visual, Thin Layer Chromatography, and Minicolumn Methods1

The negative binomial probability function was used to model the distribution of sample aflatoxin test results when replicated grade samples from farmers stock peanuts are analyzed by thin layer chromatography and minicolumn methods. The Poisson probability funtion was used to model the distribution of the number of kernels with visible Aspergillus flavus growth found in replicated grade samples of farmers stock peanuts when the visible A. flavus method is used. The probabilities of accepting a lot of farmers stock peanuts with given aflatoxin concentrations when using a 465-g grade sample and 2 different accept/reject levels were predicted with the models and compared to observed acceptance probabilities computed from previously published data for each of the 3 methods. The comparisons showed good agreement between the predicted acceptance probabilities and the observed acceptance probabilities.

Dengue hemorrhagic fever in Malaysia: the 1973 epidemic

The first major Malaysian epidemic of dengue hemorrhagic fever with severe manifestations occurred in 1973, with 969 reported cases and 54 deaths. In a detailed study of 138 clinically diagnosed and laboratory confirmed cases at the General Hospital in Kuala Lumpur, hemorrhagic manifestations were observed in 68.7% and shock in 18.1% of the patients. The cases occurred mainly from May to September, largely in urban and suburban areas of the majority of the states in the country. A main focus of infection was Jinjang, a heavily populated outlying district of Kuala Lumpur, where unusually high incidences of morbidity, severe disease and mortality were seen. Severe disease was seen mostly in children under the age of 15 years, although a significant number of adults suffered milder illnesses. The Chinese population was chiefly affected, due to their living in crowded, low-income housing where the vector, Aedes aegypti, occurred in the greatest numbers. All four dengue types were recovered during the epidemic period, although dengue 3 (DEN-3) was incriminated as the major epidemic type. Entomological data revealed high indices of A. aegypti throughout the country and left little doubt that this epidemic was aegypti transmitted. Spraying and fogging operations were carried out in attempts to control vector populations.

Comparison of five populations of Tylenchulus semipenetrans to Citrus, Poncirus, and their hybrids

The infectivity of five populations of Tylenchulus semipenetrans were compared and differentiated on 10 hosts (5 Citrus spp., 1 Poncirus trifoliata, and 4 hybrids of Citrus spp. X P. trifoliata). Differences in levels of infection and development (P = 0.01) occurred between Citrus spp. and P. trifoliata cv. 'Pomeroy' and their three hybrids, C. paradisi X P. trifoliata cv. 'Swingle' citruntelo and C. sinensis, cv. 'Ruby' orange X P. trifoliata cv. 'Webber Fawcett 14-7', and '15-7'. Poncirus trifoliata cv. Pomeroy was susceptible to a California biotype 3 and highly resistant to the other citrus nematode populations. Low infection levels with California biotype 1, Arizona, and Florida populations on Swingle citrumelo, and the two Ruby orange hybrids indicated inherited resistance. Reproduction of the nematode population from Texas was greatest on the three hybrids, Swingle citrumelo, Ruby orange 14-7, and 15-7, from the California 1, Arizona, and Florida populations, but its comparable densities on P. trifoliata and Citrus spp. were not sufficiently different from these populations to consider it a separate biotype. California biotype 3 was sufficiently different from all other populations to be considered a different biotype, and it was named the "Poncirus biotype."

Swab and excised tissue sampling for total and Enterobacteriaceae counts of fresh and surface-frozen broiler skin

Excised broiler skin tissue (12.3 cm 2 area) was (a) blended for various times up to 2 min. or (b) shaken 25, 50, or 75 times with or without sterile glass beads. Blending for 10 sec. or shaking 75 times with glass beads yielded the highest total plate count (TPC) and Enterobacteriaceae count (ENT). Counts did not significantly differ between these methods when freshly processed, unfrozen broiler skin was sampled. However, blending yielded significantly higher TPC and ENT than the conventional sampling procedure or swabbing a 12.3 cm. 2 area of the intact skin for 30 sec. with a calcium alginate swab. When sampling hard chilled (surface frozen) broiler skin, there was no significant difference between shaking and blending for TPC, but shaking gave a significantly higher ENT with less variation than blending. Blending, however, yielded significantly higher TPC and ENT counts than swabbing.