Streptococcal infections antibiotics

Acute pharyngitis presents a diagnostic and therapeutic dilemma. The majority of sore throats are caused by a variety of viruses fewer than 20% are bacterial and hence potentially responsive to antibiotic therapy. However, antibiotics are widely prescribed and this reflects the difficulty in discriminating streptococcal from non-streptococcal infections clinically in the absence of microbiological documentation. Nonetheless, Strep, pyogenes is the most important bacterial pathogen and this responds to oral penicillin. However, up to 10 days treatment is required for its eradication fixm the throat. This requirement causes problems with compliance since symptomatic improvement generally occurs within 2-3 days. 

Staphylococcus aureus is responsible for a variety of skin infections which require therapeutic approaches different from those of streptococcal infections. Staphylococcal celluhtis is indistinguishable clinically from streptococcal cellulitis and responds to cloxacillin or flucloxacillin, but generally fails to respond to penicillin owing to penicillinase (/3-lactamase) production. Staphylococcus aureus is an important cause of superficial, localized skin sepsis which varies ftom small pustules to boils and occasionally to a more deeply invasive, suppurative skin abscess known as a carbuncle. Antibiotics are generally not indicated for these conditions. Pustules and boils settle with antiseptic soaps or creams and often discharge spontaneously, whereas carbuncles frequently require surgical drainage. Staphylococcus aureus may also cause... 

A topical antibiotic or antifungal may be used to control the spread of infection but generally is unnecessary. For staphylococcal or streptococcal folliculitis, antibiotic ointments such as mupirocin might be administered three times daily. Antifungal shampoo can be used for dermatophytes. 

As streptococcal cellulitis is indistinguishable clinically from staphylococcal cellulitis, administration of a semisynthetic penicillin (nafrillin or oxacillin) or first-generation cephalosporin (cefazolin) is recommended until a definitive diagnosis, by skin or blood cultures, can be made (Table 47-4). If documented to be a mild cellulitis secondary to streptococci, oral penicillin VK, or intramuscular procaine penicillin may be administered. More severe streptococcal infections should be treated with IV antibiotics (such as ceftriaxone 50 to 100 mg/kg as a single dose). 

Obstetric infections can be treated with penicillin-beta-lactamase inhibitors such as amoxicillin-clavulanic acid, with extended spectrum penicillins (with or without beta-lacamase inhibitors if justified by local resistance surveillance data), with a first or second generation cephalosporin combined with metronidazole. In severe cases of streptococcal infection high doses of penicillin in combination with clindamycin is the treatment of choice. In amnionitis, maternal morbidity resolves with delivery. In endometritis, antibiotics should be stopped after the... 

Erythromycin is effective in the treatment and prevention of S. pyogenes and other streptococcal infections, but not those caused by the more resistant fecal streptococci. Staphylococci are generally susceptible to erythromycin, so this antibiotic is a suitable alternative drug for the penicillin-hypersensitive individual. It is a second-line drug for the treatment of gonorrhea and syphilis. Although erythromycin is popular for the treatment of middle ear and sinus infections, including H. influenzae, possible erythromycin-resistant S. pneumoniae is a concern. 

Overuse of antibiotics comes from the desire to treat colds and other illnesses caused by viruses rather than bacteria. Unlike bacteria, viruses do not respond to antibiotics. Yet the symptoms of bacterial and viral infections are similar enough that patients often want antibiotics for both. For example, a study from Harvard University reports that more than a million children a year unnecessarily receive antibiotics for sore throats.53 While 15 to 36 percent of children with sore throats have a bacterial streptococcal infection that antibiotics can treat, 54 percent of the children studied received an antibiotic. Other studies report similar overuse among adults for sinus infections. Although only a small portion of sinus infections result from bacteria, most patients visiting physicians for the problem get a prescription for an antibiotic. 

Penicillin V is a narrow-spectrum penicillin and has similar antibacterial activity to benzylpenicillin. It is active against many streptococcal infections, but it is inactivated by penicillinases. Flucloxacillin is a penicillinase-resistant antibiotic and is effective against infections caused by penicillin-resistant staphylococci. In comparison to penicillin V, attachment of carbocyclic/heterocyclic ring directly to the C6 carbonyl group confers resistance to beta-lactamases due to steric hindrance around the amide group. 

Trade names Pristinamycine Pyostacine (Sanofi-Aventis) Indications Staphylococcal streptococcal infections Category Antibiotic, streptogramin Half-life 4.03 2.77 hours... 

Early antibiotic therapy does not prevent subsequent PSGN, but it may reduce the severity of the disease. It can, however, prevent the spread of the streptococcal infection to other family members. Antibiotic prophylaxis is not recommended because infected patients will develop long-lasting, often lifelong immunity against the strain of streptococci. Exposure to another nephritogenic strain of streptococci is possible, but unlikely. 

As shown in Scheme 19.5, however, prontosil is itself an inactive prodrug that, upon oral administration, requires metabolic reduction by the gut microflora to become sulfanilamide, 6. The latter is an active antimicrobial that is very effective against streptococcal infections upon its absorption into the body. Once this was understood, the birth of the sulfonamide antibiotics can be said to have occurred and both Domagk and his daughter lived happily-ever-after. It was later shown that the structure of 6 resembles that of para-aminobenzoic acid (PABA) because... 

Scheme 19.5 Landmark experiment leading to the birth of the sulfonamide antibiotics. Prontosil, 5, is itself inactive but upon oral administration 5 is metabolized by gut microflora to 6, sulfanilamide, which exhibits excellent activity against streptococcal infections. 6 has gone on to become the prototypical sulfonamide antibiotic from which numerous other successful antibiotic drugs have been designed.

Streptococcus pyogenes may get into foods from infected handlers since they are carried on airb)orne droplets from the respiratory tract of infected people who may sneeze or cough on food. The disease caus by this bacteria is commonly called strep throat. Other Streptococcal bacteria can get into the food and cause scarlet fever. However, this is uncommon in the United States today. These diseases are characterized by fever, vomiting, and sore throat. To prevent their spread, food should E)e protected from contamination by infected handlers. Once contracted, the disease responds to penicillin and other antibiotics. Occasionally streptococcal infections produ(3e cxjmplications such as rheumatic fever and glomerulonephritis. 

In the 1930s, a bright red azo dye, prontosil, was discovered to have antibiotic activities against streptococcal infections. It was off patent before these properties were known, but led to the development of the sulfonamide antibiotics. Discuss the structures and chemistry involved in these developments. 

The goals of therapy for streptococcal pharyngitis are to eradicate infection in order to prevent complications, shorten the disease course, and reduce infectivity and spread to close contacts. Sequelae that can be prevented by antibiotic use are peritonsillar or retropharyngeal abscess, cervical lymphadenitis, and rheumatic fever. There is no evidence that antibiotic use has an impact on the incidence of poststreptococcal glomerulonephritis. 

A negative rapid streptococcal antigen test can be used to rule out streptococcal angina in patients with nonspecific symptoms and thus the need for antibiotics. When traditional throat cultures are used, complications of poststreptococcal infection can still be avoided when treatment is initiated upon a positive culture result. 

Although thera-peutic equivalence is assured if two formulations are bioequivalent, the therapeutic equivalence of two bioinequivalent formulations can be judged only within a specific clinical context (23). Thus, if we ordinarily treat streptococcal throat infections with a 10-fold excess of penicillin, a formulation having half the bioavailability of the usual formulation would be therapeutically equivalent, since it still would provide a 5-fold excess of antibiotic. 

Sulfanilamide is an effective antibiotic and has been used safely for many years to treat streptococcal and pneumococcal infections. However, sulfanilamide is generated from the azo-reduction of Prontesil, which is an example of a prodrug. A prodrug has no therapeutic effect on its own but generates active metabolites. The metabolism of prontesil, a prodrug, to its active metabolite, sulfanilamide, can be used as an example of azo reduction (Figure 6). 

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