Primary Plate Identification of Group A Streptococcus on a Selective Medium

Importance of Inoculum Size and Sampling Effect in Rapid Antigen Detection for Diagnosis of Streptococcus pyogenes Pharyngitis

“…This study addresses two important questions regarding S. pyogenes detection in throat swab specimens: what culture medium and/or technique should serve as the gold standard and whether an increase in sample size will increase the sensitivity of rapid antigen detection. We were surprised that, contrary to our previously reported results (13,17), culture on selective medium was not superior to culture on SBA, although prior reports have suggested that results may vary depending both on the medium formulation and on the medium batch (9). In fact, reported sensitivities for the TestPack as well as other S. pyogenes antigen detection tests seem to vary inversely with the rigor of the culture techniques used, with anaerobic incubation (i.e., more rigorous culture environment) tending to yield lower sensitivities than aerobic incubation (8,10,11,14,15).…”

Importance of Inoculum Size and Sampling Effect in Rapid Antigen Detection for Diagnosis of Streptococcus pyogenes Pharyngitis

“…This study addresses two important questions regarding S. pyogenes detection in throat swab specimens: what culture medium and/or technique should serve as the gold standard and whether an increase in sample size will increase the sensitivity of rapid antigen detection. We were surprised that, contrary to our previously reported results (13,17), culture on selective medium was not superior to culture on SBA, although prior reports have suggested that results may vary depending both on the medium formulation and on the medium batch (9). In fact, reported sensitivities for the TestPack as well as other S. pyogenes antigen detection tests seem to vary inversely with the rigor of the culture techniques used, with anaerobic incubation (i.e., more rigorous culture environment) tending to yield lower sensitivities than aerobic incubation (8,10,11,14,15).…”

Lack of reliability of primary grouping of beta-hemolytic streptococci by culture of throat swabs with streptocult supplemented with bacitracin disks in general practice

“…Four other studies on primary grouping of BHS in office cultures have been carried out (12,14,16,18). In all these studies the primary reading was considered a screening test, which for the purposes of this study was compared with the results obtained by the fluorescent-antibody technique (14,16,18) or by a further bacitracin susceptibility testing of the strain after isolation in pure culture (12). Specimens ultimately found positive for BHS group A had been correctly identified on the primary plate reading in 56.1% (14), 62.7% (18), 64.0% (12), and 75.7% (16) of cases.…”

Importance of Inoculum Size and Sampling Effect in Rapid Antigen Detection for Diagnosis of Streptococcus pyogenes Pharyngitis

“…This study addresses two important questions regarding S. pyogenes detection in throat swab specimens: what culture medium and/or technique should serve as the gold standard and whether an increase in sample size will increase the sensitivity of rapid antigen detection. We were surprised that, contrary to our previously reported results (13,17), culture on selective medium was not superior to culture on SBA, although prior reports have suggested that results may vary depending both on the medium formulation and on the medium batch (9). In fact, reported sensitivities for the TestPack as well as other S. pyogenes antigen detection tests seem to vary inversely with the rigor of the culture techniques used, with anaerobic incubation (i.e., more rigorous culture environment) tending to yield lower sensitivities than aerobic incubation (8,10,11,14,15).…”

Lack of reliability of primary grouping of beta-hemolytic streptococci by culture of throat swabs with streptocult supplemented with bacitracin disks in general practice

“…Four other studies on primary grouping of BHS in office cultures have been carried out (12,14,16,18). In all these studies the primary reading was considered a screening test, which for the purposes of this study was compared with the results obtained by the fluorescent-antibody technique (14,16,18) or by a further bacitracin susceptibility testing of the strain after isolation in pure culture (12). Specimens ultimately found positive for BHS group A had been correctly identified on the primary plate reading in 56.1% (14), 62.7% (18), 64.0% (12), and 75.7% (16) of cases.…”

Importance of Inoculum Size and Sampling Effect in Rapid Antigen Detection for Diagnosis of Streptococcus pyogenes Pharyngitis

“…This study addresses two important questions regarding S. pyogenes detection in throat swab specimens: what culture medium and/or technique should serve as the gold standard and whether an increase in sample size will increase the sensitivity of rapid antigen detection. We were surprised that, contrary to our previously reported results (13,17), culture on selective medium was not superior to culture on SBA, although prior reports have suggested that results may vary depending both on the medium formulation and on the medium batch (9). In fact, reported sensitivities for the TestPack as well as other S. pyogenes antigen detection tests seem to vary inversely with the rigor of the culture techniques used, with anaerobic incubation (i.e., more rigorous culture environment) tending to yield lower sensitivities than aerobic incubation (8,10,11,14,15).…”

Lack of reliability of primary grouping of beta-hemolytic streptococci by culture of throat swabs with streptocult supplemented with bacitracin disks in general practice

“…Four other studies on primary grouping of BHS in office cultures have been carried out (12,14,16,18). In all these studies the primary reading was considered a screening test, which for the purposes of this study was compared with the results obtained by the fluorescent-antibody technique (14,16,18) or by a further bacitracin susceptibility testing of the strain after isolation in pure culture (12). Specimens ultimately found positive for BHS group A had been correctly identified on the primary plate reading in 56.1% (14), 62.7% (18), 64.0% (12), and 75.7% (16) of cases.…”