Granada agar sensitivity and detection of group B streptococcus.
نویسنده
چکیده
In their recent article Overman et al. (5) present data on the sensitivity of Granada agar (7). These data are similar to those presented by the same authors in a poster with the same title (D. D. Eley, S. B. Overman, B. E. Jacobs, and J. A. Ribes, Abstr. 100th Gen. Meet. Am. Soc. Microbiol., abstr. C-238, 2000). In the poster they reported a sensitivity of 60% and in the article they reported sensitivities of 18.9 and 68.8% for two batches of Granada agar (Hardy Diagnostics, Santa Maria, Calif.). These results differ from of all other evaluations, which have found sensitivity higher than 90% (1, 2, 4, 10). There has been a flurry of e-mails on the American Society for Microbiology Division C list concerning Granada agar, and it is clear that the problem is stability. As stated in Hardy’s technical literature (catalog no. G123), Granada agar deteriorates quickly at room temperature and is useless after a few days. To overcome this problem, plates should always be kept refrigerated during shipment and in the laboratory. This short shelf life of Granada agar at room temperature is mainly caused by hydrolysis of starch by the amylase present in the horse serum (8). A key point is the use of the correct peptone. GBS pigment production is complex (even the pigment structure is unknown). The first starch-serum medium for the detection of group B streptococcus (GBS) pigment was designed in 1977 (3). Since then it has become apparent that Proteose Peptone 3 (Becton-Dickinson, Difco, Franklin Lakes, N.J.) is the only suitable peptone, because it contains peptides necessary for GBS pigment production (9). Overman et al. incorrectly insist that Granada agar must always be incubated anaerobically. GBS pigment production is related not to anaerobiosis but to growth conditions. The pigment can be easily detected by using the medium in tubes or by covering the inoculated plate with a cover slide (10), as described in Hardy’s technical literature. An overlooked fact is that hemolysis and the pigment are inseparable in GBS. All hemolytic strains are pigmented, and all pigmented strains are hemolytic (6, 11, 13). The genetic link is so tight that mutants lose simultaneously their abilities to produce pigment and hemolysin (12). Overman et al. have found an Enterococcus sp. producing pigment in Granada agar. But since the first starch-serum medium was described (3), this is the only report of its kind and therefore this finding requires confirmation. The results obtained by Overman et al. for the sensitivity of different batches of Granada agar (18 and 68.8%) can be explained by poor storage conditions during transport or in the laboratory. This issue is acknowledged by the authors when they state, “Possibly also underlying the high false negative rate for Granada agar is the issue of medium stability.” Their conclusion is misleading when they state that Granada agar has poor sensitivity. They should argue that Granada agar should be shipped and stored under the right conditions and that any batch of deteriorated medium should be discarded.
منابع مشابه
Comparison of two culture media and three sampling techniques for sensitive and rapid screening of vaginal colonization by group B streptococcus in pregnant women.
The Centers for Disease Control and Prevention (CDC) recommend universal screening of all pregnant women between 35 and 37 weeks of gestation for group B streptococci (GBS) by use of a selective broth medium. Recent reports suggest that Granada medium can be used for rapid and direct visual identification of GBS colonies. However, studies comparing the Granada medium method to the selective bro...
متن کاملEvaluation of Granada agar plate for detection of Streptococcus agalactiae in urine specimens from pregnant women.
The Granada agar plate (GAP; Biomedics SL, Madrid, Spain) was evaluated for the detection of group B streptococci (GBS) in urine specimens from pregnant women submitted for testing for asymptomatic bacteriuria and was compared with blood agar (BA [Columbia agar with 5% sheep blood]; bioMérieux, Marcy l'Etoile, France). The GAP detected 103 out of 105 GBS, whereas BA detected only 50. Use of the...
متن کاملLiquid Granada medium for detection of group B streptococci.
Heelan et al. (5) recently presented data on the sensitivity of a liquid Granada medium (9) (GBS broth) for detection of Streptococcus agalactiae. We have tested this medium, and it contains, as Granada medium, starch, proteose peptone 3, methotrexate, a Good’s buffer, serum, glucose, and selective agents. So, we agree with the authors that detection of orangered colonies in GBS broth is 100% s...
متن کاملGenotyping of Streptococcus agalactiae (group B streptococci) isolated from vaginal and rectal swabs of women at 35-37 weeks of pregnancy
BACKGROUND Group B streptococci (GBS), or Streptococcus agalactiae, are the leading bacterial cause of meningitis and bacterial sepsis in newborns. Here we compared different culture media for GBS detection and we compared the occurrence of different genotypes and serotypes of GBS isolates from the vagina and rectum. METHODS Streptococcus agalactiae was cultured separately from both rectum an...
متن کاملComparative Molecular and Microbiologic Diagnosis of Vaginal Colonization by Group B Streptococcus in Pregnant Women during Labor
Objective(s) Rapid tests for detection of Streptococcus agalactiae or Group B Streptococci (GBS) at the onset of labor are needed to permit early intrapartum antibiotic prophylaxis. This study aimed to evaluate the PCR assays targeting the 16S ribosomal RNA gene (16S rDNA) for detection of the GBS in comparison with a specific culture method. Materials and Methods Two swabs were used to obta...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of clinical microbiology
دوره 41 8 شماره
صفحات -
تاریخ انتشار 2003