Group A streptococcal infection
Group A streptococcal infections are a number of infections with Streptococcus pyogenes, a group A streptococcus (GAS).[1] S. pyogenes is a species of beta-hemolytic Gram-positive bacteria that is responsible for a wide range of infections that are mostly common and fairly mild. If the bacteria enter the bloodstream an infection can become severe and life-threatening, and is called an invasive GAS (iGAS).[2][3]
Group A streptococcal infection
Infection of GAS may spread through direct contact with mucus or sores on the skin.[2] GAS infections can cause over 500,000 deaths per year.[4] Despite the emergence of antibiotics as a treatment for group A streptococcus, cases of iGAS are an increasing problem, particularly on the continent of Africa.[5]
There are many other species of Streptococcus, including group B streptococcus Streptococcus agalactiae, and Streptococcus pneumoniae, which cause other types of infections. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes.
Prevention[edit]
S. pyogenes infections are best prevented through effective hand hygiene.[20] No vaccines are currently available to protect against S. pyogenes infection, although research has been conducted into the development of one.[21] Difficulties in developing a vaccine include the wide variety of strains of S. pyogenes present in the environment and the large amount of time and number of people that will be needed for appropriate trials for safety and efficacy of the vaccine.[21][22]
Treatment[edit]
The treatment of choice is penicillin, and the duration of treatment is around 10 days.[23] Antibiotic therapy (using injected penicillin) has been shown to reduce the risk of acute rheumatic fever.[24] In individuals with a penicillin allergy, erythromycin, other macrolides, and cephalosporins have been shown to be effective treatments.[25]
Treatment with ampicillin/sulbactam, amoxicillin/clavulanic acid, or clindamycin is appropriate if deep oropharyngeal abscesses are present, in conjunction with aspiration or drainage.[26] In cases of streptococcal toxic shock syndrome, treatment consists of penicillin and clindamycin, given with intravenous immunoglobulin.[27]
For toxic shock syndrome and necrotizing fasciitis, high-dose penicillin and clindamycin are used. Additionally, for necrotizing fasciitis, surgery is often needed to remove damaged tissue and stop the spread of the infection.[20]
No instance of penicillin resistance has been reported to date, although since 1985, many reports of penicillin tolerance have been made.[28] The reason for the failure of penicillin to treat S. pyogenes is most commonly patient noncompliance, but in cases where patients have been compliant with their antibiotic regimen, and treatment failure still occurs, another course of antibiotic treatment with cephalosporins is common.[25]
The 30-valent N-terminal M-protein-based vaccine as well as the M-protein vaccine (minimal epitope J8 vaccine) are two vaccines for GAS that are currently getting close or becoming clinical studies, however, other vaccines using conserved epitopes are progressing.[29]
Epidemiology[edit]
Cases of GAS are still present today, but were also evident before World War I. This was shown by a training camp located in Texas, where a harmful strain of pneumonia complicating measles was caused by a strain of Streptococcus.[30] Existence of streptococci strains was additionally found in World War II. An epidemic of streptococcal infection in the United States Navy during this war indicated that this type of disease was able to exist and spread in formerly unexposed individuals by environments that serological types of group A streptococci preferred.[30] In later years, a positive test result for the presence of group A streptococci was found in 32.1 percent of individuals after throat cultures were carried out in a 20 yearlong (1953/1954-1973/1974) study performed in Nashville, TN.[30] Also, from 1972 to 1974, recurring GAS illness was observed with a prevalence of 19 percent in school-aged children as well as a prevalence rate of 25 percent in families.[30] The severity of streptococcal infections has decreased over the years, and so has rheumatic fever (a sequelae of GAS) which is indicated by the change in numerous hospitals from containing wards allocated for the sole purpose of treating rheumatic fever to hardly seeing the disease at all.[30] Environmental factors, such as less crowding and the increase of family living space, can account for the reduction in incidence and severity of group A streptococci.[30] With more space for individuals to reside in, it provides the bacteria with less opportunities to spread from person to person. This is especially important considering an estimated 500,000 deaths worldwide all occurring after acute rheumatic fever, invasive infection, or subsequent heart disease can be accredited to GAS.[31] This number is quite large, often leaving the health care system encumbered, since 91 percent of patients infected with invasive GAS need to be hospitalized with 8950–11,500 episodes and 1050-1850 deaths taking place each year.[31] A later study that occurred from 2005 to 2012 found that there were 10,649-13,434 cases consequently resulting in 1136-1607 deaths per year.[29]