336 Microbes and You 



Neisseria meningitidis 



Neisseria meningitidis (formerly called Neisseria intracellularis) 

 was discovered in 1887 by Weichselbaum. The organisms are 

 spheres measuring about 0.6 to 0.8 micron in diameter, and 

 morphologically the bacteria closely resemble the gonococci. 

 These microbes were found originally in cerebrospinal fluid, but 

 they can be isolated during an epidemic from the nasopharynx, 

 blood, conjunctiva, joints, and petechiae (minor hemorrhages 

 under the skin) of infected individuals. 



About 15% of persons are healthy carriers of these organisms 

 in their nasopharynx, and during outbreaks of the disease the 

 carrier rate may rise to over 50%. The onset of meningitis is 

 usually preceded by a respiratory infection, and this is followed by 

 a stiffness of the neck, severe fever, and sometimes coma. Fresh 

 virulent strains of these Neisseria will kill mice if the organisms 

 are injected. Four different types have been described on the 

 basis of serological reactions. Before the use of antibiotics, fatality 

 rates as high as 50% were reported, but with modern treatment the 

 mortality rate has dropped to less than 10%. 



Meningitis is a condition that can be caused by any microbe, 

 including the tuberculosis organisms, streptococci, staphylococci, 

 influenzae, and others, but the epidemic form of the disease is 

 caused only by Neisseria meningitidis. 



GRAM POSITIVE RODS 



Diseases of human beings caused by gram positive rods may be 

 considered in groups based upon the oxygen requirements of the 

 bacteria and the abilit\^ of the organisms to produce spores. 



CORYNEBACTERIUM DIPHTHERIAE 



Rods, varying greatly in dimensions, 0.3 to 0.8 by 1.0 to 8.0 

 microns, occurring singly. The rods are straight or slightly 

 curved, frequently swollen at one or both ends. Do not stain 

 uniformly with methylene blue, and have granules best shown 

 by special stains. Non-motile. Gram positive in young cultures. 

 Aerobic and facultative, with an optimum growth temperature 

 of from 34-36° C. Source is from membranes in the pharynx. 



