Prevalence of β-hemolytic groups C and F streptococci in patients with acute pharyngitis

The roles of group C and F streptococci in causing endemic pharyngitis are still controversial, although group C streptococci are implicated in the outbreaks of pharyngitis and associated disorders.

The aim of this study was to determine the prevalence and the role of these groups of β-hemolytic streptococci in acute pharyngitis with emphasis on the Streptococcus anginosus group. The antimicrobial susceptibility profile of these bacterial isolates and their ability to produce some virulence factors was also determined.

Throat swab specimens were collected from 177 patients suffering from acute pharyngitis who had been admitted to the Hilla Teaching Hospital, Hilla, Iraq, during October 2009 to January 2010. The necessary biochemical tests were conducted and the organisms identified using standard procedures. Susceptibility of isolates pathogens to several antibiotics was examined using standard susceptibility testing. Virulence factors of these isolates were also determined using standard methods.

Results revealed that a total of 67 isolates belonged to β-hemolytic streptococci, of which 11(16.4%) isolates belonged to anginosus group streptococci, which possessed Lancefield group C and F antigens. Most of these bacterial isolates have the ability to produce more than one virulence factor such as capsule, hemolysin, CFA III, and lipase enzyme. The bacterial isolates were highly resistant to ampicillin, cefotaxime, and cefepime while they exhibited moderate resistance to tetracycline, ceftriaxone, and ciprofloxacin. On the other hand, they showed a high sensitivity to vancomycin, ofloxacin, and clindamycin.

This study concluded that groups C and F Streptococci were implicated as a cause of acute pharyngitis in 6.2% of the specimens among other groups of streptococci. Most of these isolates have the ability to produce more than one virulence factor. There was a high rate of resistance among isolates for β-lactam antibiotics; however, they were highly susceptible to vancomycin, ofloxacin, and clindamycin.