(BQ) Part 1 book "Medical microbiology and infection at a glance" presentation of content: Structure and classification of bacteria, innate immunity and normal flora, pathogenicity and pathogenesis of infectious disease, antibiotics in clinical use, antibacterial therapy, emerging infections, streptococcal infections,... and other contents.
Asymptomatic Pharyngeal Colonization with Gas: Treatment
When a carrier is transmitting infection to others, attempts to eradicate carriage are warranted. Data are limited on the best regimen to clear GAS after penicillin alone has failed. The combination of penicillin V (500 mg four times daily for 10 days) and rifampin (600 mg twice daily for the last 4 days) has been used to eliminate pharyngeal carriage. A 10-day course of oral vancomycin (250 mg four times daily) and rifampin (600 mg twice daily) has eradicated rectal colonization.
Erysipelas is a streptococcal infection of the superficial dermis and consists of well-demarcated, erythematous, edematous, warm plaques
Classic cases of erysipelas, with typical features, are almost always due to β-hemolytic streptococci, usually GAS and occasionally group C or G. Often, however, the appearance of streptococcal cellulitis is not sufficiently distinctive to permit a specific diagnosis on clinical grounds.
Group B Streptococcal Infection in Adults: Treatment
GBS is less sensitive to penicillin than GAS, requiring somewhat higher doses. Adults with serious localized infections (pneumonia, pyelonephritis, abscess) should receive doses of ~12 million units of penicillin G daily; patients with endocarditis or meningitis should receive 18–24 million units per day in divided doses. Vancomycin is an acceptable alternative for penicillin-allergic patients.
Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Henoch-Schönlein nephritis associated with streptococcal infection and persistent hypocomplementemia: a case report...
Pharyngitis Although seen in patients of all ages, GAS pharyngitis is one of the most common bacterial infections of childhood, accounting for 20–40% of all cases of exudative pharyngitis in children; it is rare among those under the age of 3. Younger children may manifest streptococcal infection with a syndrome of fever, malaise, and lymphadenopathy without exudative pharyngitis. Infection is acquired through contact with another individual carrying the organism.
Streptococcal disease caused by Streptococcus iniae is without doubt one of the major
bacterial diseases in fish. It has been reported to cause significant mortality in more than 12
different aquaculture species. Its distribution is worldwide in both freshwater and
marine environments. The annual impact to aquaculture has been estimated to be over US$100
million. However, in the past, very few reports have described its presence in Asia.
Harrison's Internal Medicine Chapter 130. Streptococcal and Enterococcal Infections
Streptococcal and Enterococcal Infections: Introduction
Many varieties of streptococci are found as part of the normal flora colonizing the human respiratory, gastrointestinal, and genitourinary tracts. Several species are important causes of human disease. Group A Streptococcus (GAS, S.
Enterococci may be resistant to penicillins via two distinct mechanisms. The first is β-lactamase production (mediating resistance to penicillin and ampicillin), which has been reported for E. faecalis isolates from several locations in the United States and other countries. Because the amount of β-lactamase produced may be insufficient for detection by routine antibiotic susceptibility testing, isolates from serious infections should be screened specifically for βlactamase production with a chromogenic cephalosporin or another method.
Brain Abscess (See also Chap. 376) Brain abscess often occurs without systemic signs. Almost half of patients are afebrile, and presentations are more consistent with a space-occupying lesion in the brain; 70% of patients have headache, 50% have focal neurologic signs, and 25% have papilledema. Abscesses can present as single or multiple lesions resulting from contiguous foci or hematogenous infection, such as endocarditis. The infection progresses over several days from cerebritis to an abscess with a mature capsule.
Timing of Cardiac Surgery In general, when indications for surgical treatment of infective endocarditis are identified, surgery should not be delayed simply to permit additional antibiotic therapy, since this course of action increases the risk of death (Table 118-6). Delay is justified only when infection is controlled and congestive heart failure is fully compensated with medical therapy. After 14 days of recommended antibiotic therapy, excised valves are culture-negative in 99% and 50% of patients with streptococcal and S. aureus endocarditis, respectively.
Group A Streptococci
Lancefield's group A consists of a single species, S. pyogenes. As its species name implies, this organism is associated with a variety of suppurative infections. In addition, GAS can trigger the postinfectious syndromes of ARF (which is uniquely associated with S. pyogenes infection; Chap. 315) and PSGN (Chap. 277).
Worldwide, GAS infections and their postinfectious sequelae (primarily ARF and rheumatic heart disease) account for an estimated 500,000 deaths per year.
Impetigo contagiosa is a superficial streptococcal or Staphylococcus aureus infection consisting of honey-colored crusts and erythematous weeping erosions. Occasionally, bullous lesions may be seen. (Courtesy of Mary Spraker, MD.)
The classic presentation of impetigo usually poses little diagnostic difficulty. Cultures of impetiginous lesions often yield S. aureus as well as GAS. In almost all cases, streptococci are isolated initially and staphylococci appear later, presumably as secondary colonizing flora. In the past, penicillin was nearly always effective against these infections.
Deep Soft-Tissue Infections: Treatment
Once necrotizing fasciitis is suspected, early surgical exploration is both diagnostically and therapeutically indicated. Surgery reveals necrosis and inflammatory fluid tracking along the fascial planes above and between muscle groups, without involvement of the muscles themselves. The process usually extends beyond the area of clinical involvement, and extensive debridement is required. Drainage and debridement are central to the management of necrotizing fasciitis; antibiotic treatment is a useful adjunct (Table 130-3), but surgery is lifesaving.
Streptococcal Toxic Shock Syndrome: Treatment
In light of the possible role of pyrogenic exotoxins or other streptococcal toxins in streptococcal TSS, treatment with clindamycin has been advocated by some authorities (Table 130-3), who argue that, through its direct action on protein synthesis, clindamycin is more effective in rapidly terminating toxin production than penicillin—a cell-wall agent. Support for this view comes from studies of an experimental model of streptococcal myositis, in which mice given clindamycin had a higher rate of survival than those given penicillin.
Infection with Viridans Streptococci: Treatment
Isolates from neutropenic patients with bacteremia are often resistant to penicillin; thus these patients should be treated presumptively with vancomycin until the results of susceptibility testing become available. Viridans streptococci isolated in other clinical settings usually are sensitive to penicillin.
Abiotrophia Species (Nutritionally Variant Streptococci)
Occasional isolates cultured from the blood of patients with endocarditis fail to grow when subcultured on solid media.
Diagnosis The primary goal of diagnostic testing is to separate acute streptococcal pharyngitis from pharyngitis of other etiologies (particularly viral) so that antibiotics can be prescribed more efficiently for patients to whom they may be beneficial. The most appropriate standard for the diagnosis of streptococcal pharyngitis, however, has not been definitively established. Throat swab culture is generally regarded as such.
Pharyngitis: Treatment Antibiotic treatment of pharyngitis due to S. pyogenes confers numerous benefits, including a decrease in the risk of rheumatic fever. The magnitude of this benefit is fairly small, however, since rheumatic fever is now a rare disease, even among untreated patients. When therapy is started within 48 h of illness onset, however, symptom duration is also decreased. An additional benefit of therapy is the potential to reduce the spread of streptococcal pharyngitis, particularly in areas of overcrowding or close contact.
To select the optimal therapy for streptococcal endocarditis, the minimum inhibitory concentration (MIC) of penicillin for the causative isolate must be determined (Table 118-4). The 2-week penicillin/gentamicin or
ceftriaxone/gentamicin regimens should not be used to treat complicated native valve infection or prosthetic valve endocarditis. The regimen recommended for relatively penicillin-resistant streptococci is advocated for treatment of endocarditis caused by organisms of group B, C, or G.
Bacteria rapidly become resistant to rifampin by developing mutations in the B subunit of RNA polymerase that render the enzyme unable to bind the antibiotic. The rapid selection of resistant mutants is the major limitation to the use of this antibiotic against otherwise-susceptible staphylococci and requires that the drug be used in combination with another antistaphylococcal agent.
Linezolid Enterococci, streptococci, and staphylococci become resistant to linezolid in vitro by mutation of the 23S rRNA binding site. Clinical isolates of E. faecium and E.