CHAPTER 23 



NEISSERIA 



Definition. — Neisseria. 



Gram-negative cocci, usually arranged in pairs. Strict parasites, often growing 

 poorly on ordinary media, but growing well on serum media. Frequently patho- 

 genic. 



Type species is N. gonorrhoeoe. 



The first member of this group to be described was the gonococcus ; it was 

 observed by Neisser in 1879 in the pus cells of patients with gonorrhoea, and was 

 successfully cultivated by Bumm (1885a, b) and by Leistikow and Loeffler (Leisti- 

 kow 1882) in 1882. Weichselbaum isolated the meningococcus from the cerebro- 

 spinal fluid of patients with cerebrospinal meningitis in the year 1887. In 1895 

 Jaeger described a similar organism, which he regarded as identical with the 

 meningococcus, but which was almost certainly not this organism ; it is now 

 known as the Diplococcus crassus. R. PfeifEer (see Fliigge 1896) described 

 the Micrococcus catarrhalis in 1896 ; he found it in the bronchioles and alveoli 

 of children with broncho-pneumonia ; it was carefully studied in 1902 by Ghon 

 and H. PfeifEer. In 1906 von Lingelsheim described a number of Gram-negative 

 cocci in the nasopharynx of healthy and diseased persons ; these included the 

 Micrococcus pharyngis siccus, the Micrococcus pharyngis cinereus, the Diplococcus 

 mucosus, and the Micrococcus pharyngis flavus i, ii, mid Hi. More recently Branham 

 (1930) has added another member to the group, N. flavescens. This organism 

 was isolated from the spinal fluid of patients with epidemic cerebrospinal 

 meningitis. 



Habitat. — -With the exception of the gonococcus, which is the causative organism 

 of gonorrhoea, those species of Gram-negative cocci which have been adequately 

 described are found almost exclusively in the nasopharynx of healthy and diseased 

 persons, or, in the case of the meningococcus, in the meninges and cerebrospinal 

 fluid of patients with cerebrospinal fever. 



Morphology. — The members of the group are all Gram-negative cocci, but they 

 differ considerably in their morphology and arrangement, and in the ease with 

 which they are decolorized by alcohol. Not only do they diiler from one another, 

 but the same organism may vary considerably according to environmental con- 

 ditions ; thus, in the body, the meningococcus and the gonococcus present an 

 almost typical arrangement in the form of diplococci with flattened or slightly 

 concave adjacent sides, but in culture they appear as oval or spherical cocci without 

 the typical diplococcal arrangement. Most of the members of the group are arranged 

 in pairs, tetrads, or small groups ; but some members, such as N. pharyngis, 



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