In spite of MALDI-TOF’s success in streamlining and providing extremely accurate identifications, even with previously problematic organisms, the success of currently available systems in identifying S. pneumoniae has been poor [8,9]. Hello, thank you for visiting my blog. Among the multiple genes that encode production of individual capsules, some are specific for individual polysaccharides, whereas others are conserved among nearly all pneumococci and even some other streptococci.13. A heavy inoculum should be plated on blood agar and incubated at 37°C with 5% CO2. Culture of pneumococci is frequently performed in media supplemented with blood under an atmosphere enriched in carbon dioxide since as many as 8% of the strains may require it for growth. The organism is catalase negative, but generates hydrogen peroxide (H2O2) via a flavoenzyme system and therefore grows better in the presence of a source of catalase, such as red blood cells. Enter your email address to subscribe to this blog and receive notifications of new posts by email. However, S. pneumoniae is a clade within the evolutionarily related mitis group of streptococci that can share many characteristics, including similar ribosomal proteins , making the distinction between S. pneumoniae and its less pathogenic relatives difficult by MALDI-TOF. Moreover, it was reported that, in vitro, pneumolysin is capable of inducing caspase-independent apoptosis in neurons and microglia via apoptosis-inducing factor (AIF) and mitochondrial damage (Braun et al., 2002, 2007). Optochin lyses pneumococci (positive test), but alpha-streptococci are resistant (negative test), thus aiding in its identification. The transparent phenotype is more capable of colonizing the nasopharynx, whereas the opaque phenotype shows increased virulence during systemic infections. On the basis of functional genomic analysis, it is estimated that the pneumococcus contains more than 500 surface proteins. Optochin (OP or P) disks (6 mm, 5 µg) can be obtained from a commercial vendor. The introduction of routine pneumococcal vaccination for all children in the United States to reduce invasive pneumococcal disease has also reduced the rates of acute otitis media in children caused by vaccine containing S. pneumoniae serotypes; however, it has not eliminated pneumococcus as a pathogen of the inner ear and upper respiratory tract, as 90 serotypes exist and the current protein conjugate vaccine formulation in routine use covers only 13 serotypes. Quality control of Optochin Sensitivity test. Differentiation of S. pneumoniae from other α-hemolytic streptococci is most often performed by the optochin inhibition test. Mario Ramirez, in Molecular Medical Microbiology (Second Edition), 2015. In the case of an isolate completely resistant to optochin, the diameter of the disk (6 mm) should be recorded. However, the emergence of optochin-resistant variants  has raised questions about the validity of using this test as the only test in the presumptive identification of pneumococci. Monitoring for S. pneumoniae infection is often conducted by nasopharyngeal culture onto blood agar. Of particular importance in the pathogenesis of pneumococcal disease are those that bind to choline, including surface proteins A and C (PspA, PspC), surface adhesin (choline-binding protein) A (CbpA), choline-binding protein C, and proteins involved in receptivity to DNA acquisition or competence (Table 201-1). Pneumolysin is a cytotoxic protein that targets the cholesterol-containing membranes of host membranes for pore formation and cell lysis. Optochin resistance is frequently due to point mutations in the atpC gene, which encodes a subunit of the membrane-spanning ATPase. However, because of the occurrence of nonpathogenic isolates (Fallon et al., 1988), detection of S. pneumoniae in rats, even if a respiratory problem is present in the colony, does not necessarily provide a diagnosis without corroborating histopathology, nor does isolation of S. pneumoniae from asymptomatic rats necessarily indicate a colony health threat.