Two new laboratory techniques for recovery and identification of beta-hemolytic streptococci are reviewed. One of these is an augmented culture medium containing nucleic acid, maltose and neomycin in addition to the classic agar base. Increased use of throat culture has followed a field trial of this augmented medium, with which pediatricians experienced no difficulty in distinguishing beta-hemolysis in the recognition of streptococci. The other technique, identification of streptococci with fluorescent antibody, affords a rapid means of grouping and typing on direct throat smears in those locations in which the equipment and specific fluorescein-tagged antisera are available.
Results are reported on the recovery of beta-hemolytic streptococci after transport on inert material (a Dacron-tipped throat swab in a tube with desiccant and on a Filter Paper Strip in a kit). Field trials in pediatric clinics and offices resulted in recovery of 90.5% of all positives using the Filter Paper Strip and 50.5% of the positives when swabbings were plated as controls from paired throat cultures on 1,017 children. The Filter Paper Strip technique is recommended as a reliable means of bringing the laboratory to the pediatrician. Similar trials of the Dacron swab with desiccant accounted for 80% of the positives from paired throat cultures on 552 children, with 73% positives from control cultures. The Dacron-tipped swab with desiccant technique was ready for reference laboratory study.
In the field trials of the Filter Paper Strip and Dacron-tipped swab techniques, the beta-hemolytic streptococci were isolated and classified by group and type. Of 193 positives, 82% were Group A, the rest were Group B, C or G; one-fifth were Group A, type 12. Percent by group and type is essentially the same as that reported in an earlier study of the same population. The proportion of Group C and G streptococci is high, one-seventh of the total. The proportion of Group A, type 12 organisms appears to warrant study of possible association between streptococci and glomerulonephritis in these population groups.
The new augmented culture medium, the rapid grouping and typing with fluorescent antibody, and the recently developed technique for transport on inert material enhance the value of laboratory aids to the clinician in recovery and in the identification of beta-hemolytic streptococci from throat cultures.
- Copyright © 1959 by the American Academy of Pediatrics