TABLE 1.

Unique serogroup 15 factor reactivity of new serotype 15D employing CDC Streptococcus lab typing antisera and SSI^a typing antisera

Pneumococcal strain	CDC or SSI 15 poola	CDC factors 15bfb	CDC factors 15dec	CDC factor 15gd	CDC or SSI factor 15ee	CDCor SSI factor 15hf	SSI factor 15bg	SSI factor 15cg
15A strain 389/39	+	−	+	+	−	−	−	+
15F strain 688/63	+	+	−	−	−	−	+	+
15B strain 7904/39	+	+	+	−	+	+	+	−
15C strain 553/62	+	−	+	−	+	−	−	−
15D invasive US 84245	+	+	−	+	−	−	+	+
15D carriage Mozambique MZ877	+	+	−	+	−	−	+	+

^aPooled antiserum prepared against serotypes 15A, 15F, 15B, and 15C. Identical results were obtained using CDC and commercial antiserum from Serum Staten Institut (SSI, Copenhagen Denmark) where indicated. For CDC purposes, pooled antiserum, factor 15bf, factor 15de, and factor 15g routinely used to resolve serogroup 15 strains into its 4 different serotypes (and now can be used for identifying 5 different serotypes with the inclusion of 15D). The reagents were prepared as described (3).

^bFactor 15bf consists of antiserum prepared against serotype 15F strain followed by absorbing with serotype 15A strain.

^cFactor 15de consists of antiserum prepared against serotype 15C strain followed by absorbing with serotype 15F strain.

^dFactor 15g consists of antiserum prepared against serotype 15A strain followed by absorbing with serotype 15F strain and serotype 15C strain. We highlight this result since it is the only serologic difference shown in the table between serotypes 15F and 15D.

^eFactor 15e consists of antiserum prepared against serotype 15C strain followed by absorbing with serotype 15A strain.

^fFactor 15h consists of antiserum prepared against serotype 15B strain followed by absorbing with serotype 15F strain and 15C strain.

^gFactors 15b and 15c were obtained from SSI (Serum Staten Institut).