Site streptococci

Various strains of oral streptococci produce D-glucosyltransferases which utilize sucrose as a o-glucosyl donor in the production of soluble and insoluble D-glucans. Consequently, it may be expected that some deoxyfluoro derivatives of sucrose function as competitive inhibitors for the dextransu-crases of tooth bacteria, thus preventing decay, or at least may be used as active-site probes for the enzymes. Another aim of these researches is to find non-metabolizable sweeteners. 

Leucocidins kill leucocytes and are produced by many strains of streptococci, most strains of Staphylococcus aureus and likewise most strains of pathogenic Gram-negative bacteria, isolated from sites of infection. 

Recognizing the presumed site of infection and most common pathogens associated with the infectious source should guide antimicrobial choice, dose, and route of administration. For example, community-acquired pneumonia is caused most commonly by S. pneumoniae, E. coli is the primary cause of uncomplicated UTIs, and staphylococci and streptococci are implicated most frequently in skin and skin-structure infections (e.g., cellulitis). 

Armstrong attributed the increased resistance of dentin matrix to proteolysis to the blockage of susceptible sites by covalently bound carbohydrate. Later it became clear that the Maillard reaction induces the formation of covalent bonds (cross-links) between protein molecules, accounting for such resistance as well. The presence of non-degradable matrix proteins inhibits mineral dissolution (Chapter 2). In addition, both brown pigments and cross-linked proteins inhibit the production of extracellular polysaccharides by cariogenic streptococci (Kobayashi et al., 1990). 

Mechanism of Action An oxalodinone anti-infective that binds to a site on bacterial 23S ribosomal RNA, preventing the formation of a complex that is essential for bacterial translation. Therapeutic Effect Bacteriostatic against enterococci and staphylococci bactericidal against streptococci. 

Retapamulin is a semisynthetic pleromutilin derivative effective in the treatment of uncomplicated superficial skin infection caused by group hemolytic streptococci and S aureus, excluding MRSA. Topical retapamulin 1% ointment is indicated for use in adult and pediatric patients, 9 months or older, for the treatment of impetigo. Recommended treatment regimen is twice-daily application for 5 days. Retapamulin is well tolerated with only occasional local irritation of the treatment site. 

Bjorck, L., Kastem, W., Lindahl, G., and Wideback, K. (1987) Streptococcal protein G, expressed by streptococci or by Escherichia coli, has separate binding sites for human albumin and IgG. Mol. Immunol. 24,1113-1122. 

Inoculate streptococci on the shaved back of the mouse (alternative sites for the initiation of subcutaneous infections are the flanks and the scruff of the neck) by subcutaneous injection ... 

As already pointed out, staphylococci and streptococci are generally more sensitive to biocides than Gram-negative bacteria examples are provided in Table 18.4. On the other hand, mycobacteria and especially bacterial spores are much more resistant. A major reason for this variation in response is associated with the chemical composition and structure of the outer cell layers such that there is restricted uptake of a biocide. In consequence of this cellular impermeability, a reduced concentration of the antimicrobial compound is available at the target site(s) so that the cell may escape severe injury. Another, less frequently observed, mechanism is the presence of constitutive, biocidedegrading enzymes. 

As noted earher (Sect. 12.1.3), the reduced enamel epithelium is replaced with adherent salivary proteins, mostly amylase and acidic proline-rich proteins. The acidic PRPs are at about a three times greater concentration than in secreted saliva. The acidic domain of these proteins especially has a high affinity for hydroxyapatite. Once bound to pelhcle, the N-terminus of acidic-PRPs forms an attachment site for the major classes of commensal bacteria (viridans streptococci and Actinomyces spp.) that occupy the mucosal surfaces and saliva of a healthy oral cavity. Some streptococci grow by themselves in dental biofilms, but many others grow better if certain Actinomyces spp. are also present. 

Fig. 13 2 Common bacteria of plaque. Slides show typical gram stain for (a) viridans streptococci (b) fch nomyces naeslundii, previously, viscostts (c) Eikenella corrodens, and (d) Fusobacterium nucleatum (From Public Health Image Library (PHIL) at the CDC - Bacteria Site http //phil.cdc. go v/phil/home. asp)...

Infections from dog bite wounds are caused predominantly by organisms documented to be from the dog s oral flora. Most infections are polymicrobial, with approximately five bacterial isolates per culture. Pasteurella species are the most frequent isolates. Other common aerobes include streptococci, staphylococci, Moraxella, and Neisseria. The most common anaerobes are Fusobacterium, Bacteroides, Porphyromonas, and Prevotella Wound-site cultures in both infected and noninfected patients have similar bacteria present, with aerobic organisms isolated from 74% to 90% and anaerobic organisms isolated from 41% to 49%. ... 

Streptokinase (SK), in spite of its name (-ase suffix), is a nonenzyme protein (mol. wt. 47,000). It is a catabolic product of group C 3-hemolytic streptococci. Unlike the real enzymes to be considered, it activates the fibrinolytic system indirectly. More recent research has shown that necessary steps require a prior formation of a 1 1 complex with plasminogen. This alters its conformation, thereby exposing an active site in the modified proenzyme. It is this modified complex that becomes the actual PA. SK is still a widely used thrombolytic agent, primarily because it is the least costly, is easy to obtain and had been in use for years before other PAs became available. 

Streptokinase is a 47-kDa protein produced by beta-hemolytic streptococci. It has no intrinsic enzymatic activity, but it forms a stable, noncovalent 1 1 complex with plasminogen. This produces a conformational change that exposes the active site on plasminogen that cleaves arginine 560 on free plasminogen molecules to form free plasmin. 

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