Prevalence of group A beta-hemolytic streptococcus oropharyngeal colonization in children and therapeutic regimen based on antistreptolysin levels: Data from a city from southern Brazil

Abstract

Oropharyngitis is one of the leading community infections, especially in children. The majority of etiological agents are viral; however, when bacterial, Lancefield's Group A beta-hemolytic Streptococcus (GABHS) deserves a special attention, given the risk of development of rheumatic fever (RF). Even with the introduction of antibiotic therapy - penicillin - and the increased knowledge regarding RF pathogenesis, the chronic rheumatic cardiopathy (CRC) remains the lead cause of cardiac surgery among young adults in Brazil, not unlike what takes place in other developing or underdeveloped countries. The Jones' criteria could result in up to 70% of false-negative cases of RF. Although the sensibility, specificity, and positive and negative predictive values of antistreptolysin- O (ASO) in RF are widely discussed, we reviewed the medical literature and did not find these same rates in relation to ASO and oropharyngeal culture.ASO is the most used exam to detect the previous contact with group A Streptococcus (GAS), but the optimal action would be to determine local cutoff values, considering whether its serum title elevated, avoiding the treatment of patients that do not need to receive penicillin, while determining those who deserves it. The overdiagnosis, based on ASO titles, can generate resistant strains. On the other hand, the underdiagnosis, based on the clinical diagnostic, leads to the permanence of CRC as an important problem for public health. Our population study encompassed 180 children of up to 12 years old. Oropharyngeal culture and blood exams were executed. The lead objective of the study was to determine the real accuracy of ASO. The secondary outcomes are: (a) establishing what the prevalence of GABHS is in this part of the population; (b) determining the sensibility, specificity, and positive and negative predictive values of ASO when compared with oropharyngeal culture; and (c) verifying if there is any resistance to penicillin G benzathine and other antibiotics that are often used. The proposed cutoff rate of ASO was generated by the ROC (Receiver Operating Characteristics) curve analysis, developing an innovative method of this enzyme interpretation, optimizing the approach of GABHS oropharyngeal infection and rheumatic fever. The average age of participants was 6.82 (±2.65) years. The prevalence of group A Streptococcus found was 3.9% and 25.5% of patients presented the ASO reagent. ASO showed quantitatively and qualitatively significant relations towards the presence of GABHS (p = 0.0001 for both relations) as well as for other streptococci (p = 0.0001 and p = 0.04, respectively). Throughout the ROC curve, 200 U Todd was the value that resulted in the best accuracy, demonstrating 100% of sensibility and 80% of specificity in the GAS infection documentation. The results that were found emphasize the need for similar studies in different populations. This allows for a better guidance in diagnosis and treatment of GABHS oropharyngitis, in order to prevent RF and CRC.