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Journal of Clinical Microbiology, August 1999, p. 2648-2651, Vol. 37, No. 8
Microbiology Service1
and Department of Obstetrics and
Gynecology,2 Hospitals Vall d'Hebron,
Universitat Autònoma de Barcelona, Barcelona, Spain
Received 24 February 1999/Returned for modification 26 March
1999/Accepted 18 May 1999
Granada medium was evaluated for the detection of group B
streptococci (GBS) in vaginal and rectal swabs compared with selective Columbia blood agar and selective Lim broth. From May 1996 to March
1998, 702 pregnant women (35 to 37 weeks of gestation) participated in
this three-phase study; 103 (14.7%) of these women carried GBS. In the
first phase of the experiment (n = 273 women),
vaginorectal specimens were collected on the same swab; the
sensitivities of Granada tube, selective Columbia blood agar, and Lim
broth were 31.4, 94.3, and 74.3%, respectively. In the second and
third phases (n = 429 women), vaginal and rectal
specimens were collected separately; the sensitivities of Granada
plate, selective Columbia blood agar, and Lim broth (subcultured at
4 h on selective Columbia agar in the second phase and at 18 to
24 h in Granada plate in the third phase) were 91.1, 83.9, and
75%, respectively, in the second phase and 88.5, 90.4, and 63.5%,
respectively, in the third phase. There were no statistically
significant differences in GBS recovery between the Granada agar plate
and selective Columbia blood agar, but the Granada plate provided a
clear advantage; the characteristic red-orange colonies produced
overnight by GBS can be identified by the naked eye and is so specific
that further identification is unnecessary. The use of the Granada tube
and Lim broth did not result in increased isolation of GBS. In
conclusion, the Granada agar plate is highly sensitive for detecting
GBS in vaginal and rectal swabs from pregnant women and can provide
results in 18 to 24 h.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Evaluation of the Granada Agar Plate for Detection
of Vaginal and Rectal Group B Streptococci in Pregnant Women
*
Corresponding author. Mailing address: Servicio de
Microbiología, Hospitals Vall d'Hebron, Pg. Vall d'Hebron
119-129, 08035 Barcelona, Spain. Phone: 34-93-274 6894. Fax: 34-93-274 6803. E-mail: anando{at}cs.vhebron.es.
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