Region X, the cell-wall-attachment part of staphylococcal protein A

The sequence of region X of staphylococcal protein A has been determined. The hypothesis has been put forward that this region spans the Staphylococcus aureus cell wall and is responsible for the binding to the peptidoglycan. The primary amino acid sequence of region X was determined for two strains exhibiting cell-wall-bound protein A, Cowan I and 8325-4. The sequence determination of the Cowan I material is partial and was performed by Edman degradation, in contrast to the sequence of the 8325-4 material which was completely analyzed by nucleotide sequencing of the corresponding gene. The region consists of two structurally different domains, a highly repetitive region (Xr), with an octapeptide structure repeated approximately 12 times, and a C-terminal domain (Xc) with an unique sequence. A comparison between the two strains reveals a high mutual homology as well as a high internal homology between the octapeptide structures. Six out of eight amino acids are identical in the repetition of this structure throughout region Xr in both proteins and the other two are changed in a rather regular pattern.     

Vision screening at 8 and 18 months. Steering Committee of Oxford Region Child Development Project.

OBJECTIVE--To determine the effectiveness of an existing screening programme based in the community for ocular and vision defects in infants considered at increased risk of such defects. DESIGN--Children with ocular or vision defect by the age of 2 were ascertained by searching records. Those from populations at high risk were matched with their results from screening tests. The characteristics of the cases among this population were compared with those of the cases in the remainder of the population. Patterns of referral and age at referral were studied in both groups. SETTING--The study was conducted within Oxfordshire Health District. SUBJECTS--433 Children at high risk born in 1984 to mothers living in the health district at delivery and who either weighed less than 2000 g or weighed 2000 g and over and required admission to a special care nursery for longer than 24 hours. The low risk population (6254) were infants without these characteristics who were resident in the health district at the time of referral. INTERVENTIONS--Screening tests for vision or ocular defects already routinely used were applied by health visitors at 8 and 18 months to the children at high risk. MAIN OUTCOME MEASURE--Comparison of results of screening tests with vision and ocular defects detected by the age of 2. RESULTS--Screening tests in current use for vision loss and squint in this age group were insensitive and had a low positive predictive value when applied to a high risk population. Defects that were not apparent on direct inspection were unlikely to be detected by these tests. In the high risk group the relative risk of having a defect was 2.8 (95% confidence interval 1.8 to 4.5) but 85% of all cases detected by the age of 2 were in children at low risk. Referral patterns and age of referral differed in the two groups. CONCLUSIONS--Screening by health visitors of high risk populations contributes little to the detection of vision and ocular defects. This type of evaluation needs to be applied also to low risk populations, who have different referral patterns and contribute most of the cases.