Streptococcus

epidemiology of streptococcal infections

1. Streptococcal Diseases Prepared by Samira Fattah Assis. Lec. College of health sciences-HMU

2. STREPTOCOCCAL DISEASES CAUSED BY GROUP A (BETA HEMOLYTIC) STREPTOCOCCI Identification— Group A streptococci cause a variety of disease, the most frequently encountered conditions are: streptococcal pharyngitis tonsillitis (sore throat) streptococcal skin infections (impetigo or pyoderma ).

3. STREPTOCOCCAL DISEASES CAUSED BY GROUP A (BETA HEMOLYTIC) STREPTOCOCCI Other diseases and infections include: Scarlet fever Puerperal fever Septicemia Erysipelas Cellulitis Otitis media Pneumonia, Peritonsillitis wound infections and rarely, necrotizing fasciitis, rheumatic fever and a toxic shock-like syndrome.

4. patients with streptococcal sore throat typically exhibit sudden onset of fever, exudative tonsillitis or pharyngitis (sore throat), with tender, enlarged anterior cervical lymph nodes. subsequent otitis media may occur; as may acute glomerulonephritis (1–5 weeks, mean 10 days) or acute rheumatic fever (mean 19 days). Rheumatic heart ( valvular ) disease occurs days to weeks after acute streptococcal infection.

5. Scarlet fever is a form of streptococcal disease characterized by a skin rash, occurring when the infecting strain produces a pyrogenic exotoxin . Clinical characteristics may include enanthem , strawberry tongue and exanthem . The rash is often felt (like sandpaper) better than seen and appearing most often on the neck, chest, folds of the axilla and elbow.

6. Typically, the scarlet fever rash does not involve the face, but there is flushing of the cheeks. High fever, nausea and vomiting often accompany severe infections. During convalescence, desquamation of the skin occurs at the tips of fingers and toes. The case-fatality rate in some parts of the world has occasionally been as high as 3%.

7. Erysipelas is an acute cellulitis characterized by a red, tender, oedematous spreading lesion of the skin, often with a definite raised border. Face and legs are common sites. The disease is more common in women and may be especially severe, with bacteraemia , in patients suffering from debilitating disease. Case-fatality rates vary depending on the part of the body affected and whether there is an associated disease.

8. Streptococcal puerperal fever is an acute disease, usually febrile, with local and general symptoms/signs of bacterial invasion of the genital tract and sometimes the bloodstream in the postpartum or postabortion patient. Case-fatality rate is low when streptococcal puerperal fever is adequately treated.

9. Toxic shock syndrome (TSS) in people with invasive group A streptococcal infection has been increasingly recognized since 1987. clinical features include hypotension and any of the following: -renal impairment -thrombocytopenia -disseminated intravascular coagulation - SGOT or bilirubin elevation ageneralized erythematous macular rash or soft-tissue necrosis (necrotizing fasciitis).

10. Streptococci of other groups can produce infections in humans Betahemolytic organisms of group B found in the human vagina may cause neonatal sepsis and suppurative meningitis, as well as urinary tract infections, postpartum endometritis and other systemic disease in adults, especially those with diabetes mellitus. Group D organisms (including enterococci ), hemolytic or nonhemolytic , are involved in bacterial endocarditis and urinary tract infections. Groups C and G have produced outbreaks of streptococcal tonsillitis, usually foodborne . Group C and G infections are more common in adolescents and young adults. Alpha-hemolytic streptococci are also a common cause of bacterial endocarditis .

11. laboratory findings for group A streptococcal disease are based on the isolation of the organisms from affected tissues on blood agar or other appropriate media or on identification of group A streptococcal antigen in pharyngeal secretions (the rapid antigen detection test). Colony morphology and the production of clear beta- hemolysis on blood agar made with sheep’s blood identify streptococci on cultures inhibition by special antibiotic discs containing bacitracin (0.02– 0.04 units) constitutes tentative identification. Specific serogrouping procedures provide definitive identification.

12. Infectious agent Streptococcus pyogenes group A streptococci of over 130 serologically distinct types that vary by geographic and time distributions. Group A streptococci producing skin infections usually differ serologically from those associated with throat infections.

13. Occurrence Streptococcal pharyngitis /tonsillitis and scarlet fever are common in temperate zones, well recognized in semitropical areas and less frequently recognized in tropical climates. Before the age of 2–3, streptococcal infections may occur but streptococcal pharyngitis is unusual; this peaks in age group 6–12 and declines thereafter. Cases occur year round but peak in colder seasons.

14. Acute rheumatic fever may occur as a nonsuppurative complication following infection with group A serotypes that have the capacity to produce clinical infection of the upper respiratory tract. Rheumatic fever remains a great health problem in the developing world.

15. Reservoir Humans.

16. Mode of transmission Large respiratory droplets or direct contact with patients or carriers rarely indirect contact through objects. Individuals with acute upper respiratory tract (especially nasal) infections are particularly likely to transmit infection. In populations where impetigo is prevalent, the same strain may appear in the throat (without clinical evidence of throat infection).

17. Anal, vaginal, skin and pharyngeal carriers have been responsible for nosocomial outbreaks of serious streptococcal infection, particularly following surgical procedures. Identification of the carrier often involves intensive epidemiological and microbiological investigation. eradication of the carrier state is often difficult and may require multiple courses of specific antibiotic regimens.

18. Incubation period Short, usually 1–3 days, rarely longer.

19. Period of communicability In untreated, uncomplicated cases, 10–21 days; in untreated conditions with purulent discharges, weeks or months. With adequate penicillin treatment, transmissibility generally ends within 24 hours.

20. Susceptibility Susceptibility to streptococcal pharyngitis /tonsillitis and scarlet fever is general, although many people develop either antitoxin- or type-specific antibacterial immunity, or both, through inapparent infection. Antibacterial immunity develops against the specific M-type of group A streptococcus that induced infection and may last for years. Antibiotherapy may interfere with the development of type-specific immunity.

21. Immunity against erythrogenic toxin, and hence against rash, develops within a week after onset of scarlet fever and is usually permanent; second attacks of scarlet fever are rare. Some degree of passive immunity to group A streptococcal disease occurs in newborns with transplacental maternal type specific antibodies. Patients who had one attack of rheumatic fever have a significant risk of recurrence of rheumatic fever, often with further cardiac damage following group A streptococcal infections. Individuals who had erysipelas appear predisposed to subsequent attacks. Recurrence of glomerulonephritis is unusual, perhaps because very few M-types are “ nephritogenic ”.

22. Methods of control Preventive measures: Educate the public and health workers about modes of transmission; about the relationship of streptococcal infection to acute rheumatic fever, rheumatic heart disease and glomerulonephritis ; and about the need for prompt diagnosis and completion of the full course of antibiotherapy prescribed for streptococcal infections. 2) Provide easily accessible laboratory facilities for recognition of group A hemolytic streptococci. 3) Pasteurize milk and exclude infected people from handling milk likely to become contaminated.

23. 4) Prepare other potentially dangerous foods just prior to serving or adequately refrigerate in small quantities at 4°C (39°F) or less. 5) Exclude people with skin lesions from food handling. 6) Secondary prevention of complications: To prevent streptococcal reinfection monthly injections of long-acting benzathine penicillin G (or daily penicillin orally in compliant patients) should be given for at least 5 years. Those who do not tolerate penicillin may be given sulfisoxazole orally or erythromycin if necessary.

24. Control of patient, contacts and the immediate environment : 1) Report to local health authority: Obligatory report of epidemics, 2) Isolation: Drainage and secretion precautions may be terminated after 24 hours’ effective antibiotherapy ; antibiotherapy should be continued for 10 days to avoid development of rheumatic heart disease. 3) Investigation of contacts and source of infection.

25. Epidemic measures: 1) Determine source and manner of spread (person-to-person, milk, food). Outbreaks can often be traced to an individual with an acute or persistent streptococcal infection or bearing streptococci (nose, throat, skin, vagina or perianal area) through identification of the M-type of the streptococcus. 2) Investigate promptly any unusual grouping of cases to identify possible common sources, such as contaminated milk or foods. 3) For outbreaks in special close contact groups (e.g. the military, day care centers, schools, nursing homes), it may be necessary to administer penicillin to the entire group to terminate spread.

26. GROUP B STREPTOCOCCAL SEPSIS OF THE NEWBORN Human subtypes of group B streptococci ( S. agalactiae ) produce invasive disease in the newborn under 2 distinct forms: -Early onset disease (from 1–7 days), with sepsis, pneumonia and less frequently meningitis, osteomyelitis or septic arthritis, is acquired in utero or during delivery. -Late onset disease (7 days to several months) is acquired in about half the cases through person-to-person contact and presents mostly as meningitis or sepsis.

27. Advances in neonatal care has led to a fall in the case fatality rate from 50% to 4%. Survivors may have speech, hearing or visual problems, psychomotor retardation or seizure disorders if there has been meningeal involvement. About 10%–30% of pregnant women harbour group B streptococci in the genital tract, and about 1% of their offspring may develop symptomatic infection.so those are candidates for intrapartum antibiotic prophylaxis.

28. DENTAL CARIES OF EARLY CHILDHOOD, STREPTOCOCCAL Streptococcus mutans is present in these carious lesions. These Gram positive facultative anaerobes produce caries in young experimental animals in the presence of dietary sugar. They are members of the viridans group of streptococci; hemolysis of blood agar is usually alpha or gamma. They are common residents of dental plaque.

29. Mother-to-child transmission occurs through transfer of infected saliva by kissing the baby on the mouth or, more likely, by tasting food on the baby’s spoon before serving it. mothers with extensive dental caries usually have high levels of mutans streptococci in their saliva.

30. To prevent dental caries of early childhood, promote good oral hygiene in mothers . Counsel parents and caretakers about the dangers of dental caries from feeding children milk a containing sugar and of transferring saliva to a baby’s mouth when mothers and other caretakers have untreated carious teeth.