COCCI

From Big Medical Encyclopedia

COCCI — the bacteria which are characterized by spherical shape of cells in which development cycle are never formed rod forms.

Classification

In old English classification system [Wilson and Myles (G. S. Wilson, A. A. Miles), 1957] To. are carried to two families: Coccaceae (a tribe of Neissereae and Micrococcaceae with the sorts Neisseria, Staphylococcus, Micrococcus, Sarcina and Rhodococcus) and Bacteriaceae (a tribe of Lactobacilleae with the sorts Streptococcus and Leuco-nostoc).

According to the 8th edition of determinant of bacteria of Berdzhi (Bergey’s Manual of determinative bacteriolory, 1974) gram-positive To. divide into two groups: a) aerobic (see. Aerobes ) and optional anaerobic cocci, b) anaerobic (see. Anaerobe bacterias ). The first group includes two families: 1) Micrococcaceae combining three sorts — Micrococcus, Staphylococcus and Planococcus, 2) Streptococcaceae including 5 childbirth — Streptococcus, Leuconostoc, Pediococcus, Aerococcus, Gemela. To group anaerobic To. the Peptococcaceae family combining the following four sorts belongs: Peptococcus, Peptostreptococcus, Ruminococcus u Sarcina.

Gram-negative K. it is also possible to divide into two groups: a) aerobic, b) anaerobic. Carry three families to the first group: 1) Neisseriaceae combining two sorts — Neisseria and Branhamella, 2) Methylomonadaceae including the sort Methylococcus; 3) Halobacteriaceae including the sort Halococcus. Carry the Veillonellaceae family combining three sorts to the second group — Veillonella, Acidaminococcus, Megasphaera.

Morphology

Many To. in a form approach true spheres. In some cases (e.g., at reproduction) spherical shape undergoes some changes and separate cells can be ellipse. From typical spherical shape deviations are frequent; e.g., Streptococcus pneumoniae has a point of one of poles and the cell becomes similar to a lancet, at Neisseria gonorrhoeae (gonokokk) separate cells can have an appearance of a coffee bean with the concave parties turned one to another. In old cultures and under unfavorable conditions of growth strongly inflated spherical, kolbovidny and other involutional shapes meet sometimes. Size K. from 0,2 to 2,5 microns fluctuate, 0,5 — 1,0 microns are more often. Stafilokokki and streptococci reach 0,6 — 1,0 microns in the diameter and pneumococci of 0,5 — 1,25 microns. Diameter of micrococci of some types can reach on average 1 — 1,5 micron (e.g., Micrococcus luteus has to dia. 1,0 — 1,2 microns). Diameter of some types sartsin reaches 2,5 microns (e.g., Sarcina ventriculi).

To. are well painted by different aniline paints and have no acid resistance. To. usually are not mobile and deprived of flagellums (they are available only for the few childbirth, napr, for Planococcus); endospores are not formed. Pneumococci, some types of streptococci and golden staphylococcus have the capsules consisting of complex polysaccharides.

To. breed by division. When the bacterial cell shares, two affiliated or at once separate one from another, or remain together, adjoining cellular membranes. When this incomplete division continues during many consecutive divisions of a bacterial cell, units of cells are formed; their form depends on the planes in which there will be consecutive divisions, and from number of cell divisions. The units which are formed in such way are very characteristic and present an important factor in the characteristic To. Those organisms which after cell division are completely separated and seem under a microscope single and scattered randomly across the field of sight, are called micrococci. Groups of two To. carry the name of diplococcuses. If division To. occurs only in one plane and formed To. remain together, the chain from as a result turns out To. in the form of a necklace, consisting sometimes of several tens cells. These microbes are called streptococci or tsepekokka.

At the division happening in two mutually perpendicular planes there are combinations To., called by tetracocci if groups on 4 cocci, and merismopediya are formed if groups consist of many To. If division correctly repeats in three mutually perpendicular planes, then connection of cells in the form of packages — so-called sartsina turns out. If To. share diversely without special correctness and remain together, forming the chaotic accumulations of cells reminding bunches, they are called by stafilokokkam or grozdekokkam.

Not all cells under review under a microscope are located in characteristic groups, many microbes of an odinochna. Formation of a chain of streptococci depends on the environment of cultivation. Lactic streptococci, e.g., form long chains in milk culture, but when grow in nutrient broth, can form only short chains. In smears from pus or similar material the coccal forms are usually had a characteristic arrangement.

To. differ in difficult exchange which usually includes amino-acid and carbohydrate metabolism. The majority To. it is easily cultivated on artificial mediums. Some To., e.g. Neisseria meningitidis, Neisseria gonorrhoeae, demand for growth of addition of protein. Chromogenesis is often observed. Colonies To. smooth, with smooth edges, at many types painted in yellowish, orange or reddish color. Developing in fluid medium — a beef-extract broth, To. give uniform dregs.

Pathogenicity of cocci

Among numerous To. for inf. pathologies of the person and animals the greatest value have those which have a complex of the properties providing their pathogenic activity which is expressed in ability To. to produce in the course of life activity toxicants (ekzo-or endotoxins) and other aggressive substances, causing inf. diseases and being the reason of complications of other diseases. On degree of manifestation of pathogenic properties K. it is possible to divide on saprofitichesky, not having pathogenic properties (some lactic streptococci, To. the sorts Leuconostoc, Planococcus, Sarcina), conditionally pathogenic (some diplococcuses allocated from mucous membranes, some micrococci and tetracocci) and pathogenic. Among the last in pathology of the person pneumococci, piogenic streptococci, gonokokk, meningokokk, golden staphylococcus have the greatest value.

Unlike a pneumococcus, the gonokokka and a meningokokka, pathogenic streptococci and especially staphylococcus, having considerable resistance to adverse external effects and ability to live both in aerobic, and in anaerobic conditions, are eurysynusic in the nature. Pathogenic staphylococcus often meet in the soil, water, air and almost always on the surface of a human body, cause various diseases of skin from folliculites to an anthrax, osteomyelites and some other a serious illness. Pathogenic streptococci are also eurysynusic in the nature, often meet on the surface of a human body, on mucous membranes and are activators of an ugly face, quinsy, puerperal sepsis and some other a serious illness.

Separate childbirth and types To. — see. Neisseria , Pnevmokokki , Stafilokokki , Streptococci .

See also Bacteria .



Bibliography: Krasilnikov N. A. Determinant of bacteria and actinomycetes, page 250, M. — L., 1949; The Guide to microbiological diagnosis of infectious diseases, under the editorship of K. I. Matveev, M., 1973; The Reference book on microbiological and virologic methods of a research, under the editorship of M. O. Birger, M., 1973; Bergey’s manual of determinative bacteriology, ed. by R. E. Bucbanan a. N. E. Gibbons, Baltimore, 1975; Prevot A. R. Biologie des maladies dues aux of ana£robies, p. 417, P., 1955; W i 1 s o n G. S. a. Miles A. A. Topley and Wilson’s principles of bacteriology and immunity, v. 1—2, L., 1964.

G. V. Vygodchikov.

Яндекс.Метрика