Enterococcus

ENTEROCOCCUS Escherich, syn.: Micrococcus ovalis Escherich, Streptococcus faecalis of English authors; Strept. enteritidis Hirsch and Liebmann; Diplococcus intestinalis Takel and Lanz. Enterococcus belongs to the streptococcus group and was first described by Escherich in 1886, when he isolated a coccus from the intestine of an infant, which he named oval micrococcus due to its elongated shape. For the first 25 years, this microbe did not attract the attention of bacteriologists and was considered a harmless saprophyte. However, its frequent presence as a saprophyte in the human body, especially in the intestine and urogenital tract, as well as its undoubted pathogenicity led to a thorough study of its biological properties. The name enterococcus was not immediately established for this microbe; only in 1889 did the French scientist Thierrélin isolate a similar coccus in cases of enteritis with suppurations and named it enterococcus, a name that has remained for this microbe to the present day. Morphological properties. Enterococcus has the shape of an elongated coccus (Schmitz, K. Meyer) and resembles pneumococcus in form but lacks a capsule and is somewhat larger in size; according to Escherich, the diameter of the coccus is 0.2-0.3 μ, and in the stage of division it reaches 0.6-0.7 μ. A small slit is noticeable between two cocci; the cocci are arranged in pairs and short chains, sometimes in small clusters. They are polymorphic and sometimes take the form of diplobacteria, stain well with aniline dyes and according to Gram. Biological properties. Enterococcus grows well on all ordinary nutrient media at 37°, as well as at room temperature; it does not liquefy gelatin with rare exceptions (K. Meyer); on agar it gives transparent drop-like colonies typical of the streptococcus group, 1-2 mm in size; blood agar usually does not hemolyze, but K. Meyer described individual strains that give hemolysis and grayish-white colonies on blood medium. In broth, enterococcus always forms a uniform turbidity; after several days, a sediment that stretches appears at the bottom. Enterococcus withstands heating to 60°, ferments mannitol, breaks down glycosides 46S (esculin, salicin, arbutin, amygdalin and methyl-glycoside), mostly does not break down raffinose, does not dissolve in bile and is resistant to optochin. Differential diagnosis. To distinguish enterococcus from other cocci of the related group (pathogenic streptococci, pneumococcus), special media have been proposed: 1. Medium with bile in the form of 1% peptone water + 20% bile. Enterococcs grow well in this medium and can survive in it, while streptococci die after 24 hours in an incubator. Solutions of sodium taurocholate kill streptococci and are tolerated by enterococcs in a concentration of 1:10. 2. For the breakdown of glycosides, Rochaix applied in 1924 the liquid esculin medium of Harrison and Vanderleek. The essential component in this medium is the presence of iron salts, which when esculin is broken down into grape sugar and esculetin form colored compounds with the latter, colored black. 3. Thermoresistance is determined by heating a single-broth culture in glass capillaries in a water bath at 60°, which is successfully tolerated by most strains of E. In terms of its morphological and biological properties, E. is closest to the milk streptococci; Gundel considers both microorganisms to belong to the same species. The pathogenicity of E. can manifest under certain conditions (weakening of the body, subsequent infection) and has been noted by both French and German authors. Schmitz notes the presence of E. in chronic enteritis of infants. Kurt Meyer found E. in various suppuration processes related to the intestine (appendicitis, paratyphlitis, paraproctitis); enterococcus is particularly often found in urine in cases of cystitis and pyelitis and has special significance in inflammation of the bile ducts, in which it was detected in 41.5% of cases and was isolated in pure culture by K. Meyer in 22 cases. Individual cases of enterococcal pleurisy, meningitis and sepsis and endocarditis have also been described.