Prevalence and Antibiotic Susceptibility of Group A Beta Haemolytic Streptococcal Isolates and Assessment of the Sensitivity of Selected Clinical Predictive rules in Chuldren Presenting with Acute Pharyngitis to the University Teaching Hospital, Lusaka, Zambia

Background: Group A beta haemolytic streptococcus(GABHS) associated pharyngitis is an important infection in children because of its potential to complicate into rheumatic fever and rheumatic heart disease - these are preventable with timely and appropriate antibiotic treatment. Physicians in resource poor settings such as Zambia have largely had to rely on unvalidated clinical scoring systems to decide on whether to administer antibiotics when presented with a child who has evidence of pharyngitis. The objective of this study was to determine the prevalence and antibiotic susceptibility of GABHS isolates as well as to assess the sensitivity of three clinical diagnostic criteria in children presenting with acute pharyngitis to the paediatric department.
Methods: This was a descriptive cross sectional study that was carried out over a period of six months (April- September 2011) at the paediatric outpatient department of the University Teaching Hospital in Lusaka, Zambia, involving children 3-15 years of age presenting with pharyngitis. The enrolled study participants all underwent a standard clinical assessment during which their respective clinical findings were recorded using data sheets. In addition, all the recruited participants had laboratory work out that included a throat swab for culture and subsequent typing as well as antibiotic sensitivity testing of respective isolated organisms. Data analysis with regard to prevalence and antibiotic susceptibility of GABHS isolates as well as assessment of the sensitivity of three clinical diagnostic criteria (Zambia treatment guideline criteria; The WHO ARI management criteria; The modified Centor score) was done using Epi Info version 3.3.2 and Open Epi version 2.3.
Results: A total of 146 children were recruited. Of these, 22 had GABHS pharyngitis, accounting for a prevalence of 15.1%. All the GABHS isolates were susceptible to penicillin while 5(19%) had reduced susceptibility to erythromycin. None of the parameters on the Zambia treatment guideline criteria ,when used individually ,was found to have sensitivity to detect GABHS pharyngitis; Pharyngeal exudates had a sensitivity of 4.5%, 40% for painful enlarged tonsils, 18% for both fever and tender cervical lymph nodes and 36% for the absence of viral signs. The WHO ARI management criteria were not assessed because none of the children with GABHS pharyngitis displayed any of the signs required by the criteria. The modified
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Centor score had a sensitivity of only 9.1% while the area under the Reciever Operator Curve (ROC) was 0.51.
Conclusion: The prevalence of GABHS pharyngitis in children presenting with acute pharyngitis at UTH is 15.1%. Penicillin remains the suitable drug of choice for treatment and both tested criteria have poor sensitivity to identify GABHS pharyngitis. Further study in a primary care setting is needed to develop and adapt more sensitive criteria for the diagnosis of GABHS pharyngitis suitable for a high rheumatic heart disease endemic area