ABSTRACT
The aim of this study was to contribute to our knowledge of the construct validity of the Griffiths Scales of Mental Development (Griffiths Scales) through an examination of the underlying dimensions tapped by the six subscales, using Common Factor Analysis. A sample of 430 South African children, from four ethnic groups (i. e. White, Mixed Race, Asian and Black) participated. The correlation coefficients obtained for the South African groups were compared to those Griffiths obtained in her work with the British standardization sample of the Griffiths Scales. The pattern of correlation for South African and British subjects was found to be similar. This suggests that the Scales are measuring a construct which is consistent across cultures and through time. A factor analysis was performed with the data for each South African ethnic group separately and the factor solutions were compared to determine whether the Griffiths Scales measure similar or different constructs for the groups. The results indicate that the Griffiths Scales tend to measure one factor, and including only common variables, the factor appears to be similar cross-culturally.
Subject(s)
Child Development , Mental Processes , Child , Child, Preschool , Ethnicity , Factor Analysis, Statistical , Humans , South AfricaABSTRACT
The study was conducted to determine whether pre-enrichment would increase sensitivity of detecting Streptococcus (Str.) agalactiae, Staphylococcus (S.) aureus, and mycoplasma in bovine milk. Two procedures were followed, one involving direct inoculation of milk on bovine blood agar, and the other involving preenrichment in broth followed by inoculation on agar. Logistic regression was used to predict the probability of isolation as a function of culture procedure and two additional covariates, the California Mastitis Test (CMT) score of the milk and the type of sample (indicating sample storage temperature and herd mastitis status). A total of 13778 milk samples was cultured for each of the three bacteria. By using results of both direct inoculation and pre-enrichment, the probability of isolation compared to use of direct inoculation only and adjusted for effects of other variables was increased 3.6-fold for Str. agalactiae, 1.6-fold for S. aureus and 1.7-fold for mycoplasma. The probability of isolation for all three bacteria increased as the CMT score increased. For Str. agalactiae, there was a statistical interaction predicting that enrichment improved the odds of isolation more from milk with high CMT scores than from milk with low scores. Results indicate that pre-enrichment can substantially increase the sensitivity of bacteriological screening of dairy cows for mastitis caused by Str. agalactiae, S. aureus, and mycoplasma.
Subject(s)
Mastitis, Bovine/diagnosis , Milk/microbiology , Mycoplasma/isolation & purification , Staphylococcus aureus/isolation & purification , Streptococcus agalactiae/isolation & purification , Animals , Cattle , Female , Mycoplasma Infections/diagnosis , Mycoplasma Infections/veterinary , Predictive Value of Tests , Probability , Regression Analysis , Staphylococcal Infections/diagnosis , Staphylococcal Infections/veterinary , Streptococcal Infections/diagnosis , Streptococcal Infections/veterinaryABSTRACT
A study was undertaken to evaluate effectiveness of a digitonin disk inhibition test to discriminate between Acholeplasma laidlawii and Mycoplasma sp. isolated from bovine milk. The test measured zone diameters of growth inhibition surrounding a digitonin-containing disk on solid medium. Zones of inhibition for 20 isolates of A. laidlawii, ranging from 8-14 mm, did not overlap those of 261 isolates of Mycoplasma sp., ranging from 16 to 38 mm. Examination of variation in zone diameters for M. bovis found that inhibition was not appreciably affected by agar dehydration. Zones of inhibition increased with increasing dilutions of stock culture and decreased with increasing incubation time. Analysis of variance and Fisher's least significant difference test of logn zone diameters revealed that differences in mean logn zone diameters were different at the 0.01 level of significance between some of the six species of mycoplasma examined, indicating that growth among some species of mycoplasma was effected differently by digitonin. The digitonin test was found to clearly discriminate between A. laidlawii and Mycoplasma sp. indicating that the test would be useful as a practical screening test of individual-cow and bulk tank milk for mycoplasmas.
