Haemophilus influenzae was first isolated by Pfieffer during the 1889 influenza pandemic. For a time, H. influenzae was believed to be the causative agent of influenza and originally was called the influenza bacillus. However, subsequent studies demonstrated the fallacy of…
Characteristics Of Pathogens Among the gram-positive catalase-negative cocci, streptococci and enterococci cause most human infections. The remaining organisms belong to 5 genera that can be identified according to the criteria proposed by Facklam and colleagues ( Table 124.1 ), and…
The β-hemolytic streptococci can be subdivided on the basis of whether they form large colonies or minute colonies on solid agar. Most notable among those β-hemolytic streptococci that form large colonies are Streptococcus pyogenes (group A) and Streptococcus agalactiae (group…
The viridans streptococci are genetically diverse organisms that share the propensity to colonize humans and occasionally penetrate local barriers to cause life-threatening disease. Their importance as the predominant cause of endocarditis in children and adults has been known for decades.…
Historically enterococci, Streptococcus bovis, and S. equinus were grouped together as Lancefield group D streptococci. However, genomic analysis resulted in the reclassification of these organisms, and enterococci now are considered a separate genus ( Table 120.1 ). This chapter focuses…
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The ability to differentiate among distinct groups of organisms and to communicate with a common language about organisms in the context of disease is essential for clinical microbiologists and for physicians caring for patients. The official taxonomic ranks for naming…