The pyogenic organisms studied in this exercise are primarily pathogens of the upper respiratory tract although they may be found in the absence of disease in the nasopharynx. The important genera are Neisseria and Hemophilus.
The Neisseriae comprise a family of Gram-negative organisms most of which are non-pathogenic inhabitants of the upper respiratory tract. They are cocci that occur in pairs with adjacent surfaces slightly flattened to give them a bean-shaped appearance. All of the species in this family produce the enzyme oxidase, and so can be differentiated from most other Gram-negative bacteria (except Pseudomonas) by the Oxidase Test.
Two members of this family are important pathogens with humans being the sole reservoir of these two species. Neisseria meningitidis causes purulent meningitis, occasionally epidemic in distribution. Infections due to Neisseria gonorrhoeae have presently reached epidemic proportions. Primarily a venereal infection, sequelae to initial infection may consist of septic arthritis and endocarditis.
Branhamella sicca, Branhamella flavescens and other members of the Neisseriae family are normal flora of the nasopharynx, and can also be found in the female genital tract. These are usually non-pathogenic and thus must be differentiated from the pathogens in cultures taken from areas contaminated with normal flora. Although placed in a different genus (Branhamella), these organisms exhibit gram stain reactions identical to the pathogenic Neisseria species.
The Hemophilus group are Gram-negative, non-motile, aerobic, pleomorphic bacilli. These organisms require enriched media for primary isolation and all grow better in the presence of blood (Hemophilus = blood loving). The factors essential for the growth of some or all of the species in this genus are a heat-stable factor (X- factor) identified as hemin or hematin, and a heat-labile factor (V-factor) replaceable by nicotinamide adenine dinucleotide (NAD) or closely related compounds.
|SPECIES||GROWTH FACTOR REQUIREMENTS||HEMOLYSIS|
|Hemin (X factor)||NAD (V factor)|