The emerging role of group A beta hemolytic Streptococcus as retropharyngeal abscess pathogen in children--a change which doesn't matter?

Usually, a case of retropharyngeal abscess (RPA) in children represents a suppurative stage in the evolution of lymphadenitis in the retropharyngeal space, secondary to infection elsewhere in the head or neck (eg, sinusitis, tonsillitis, otitis). Modern medicine has contributed to a significant decrease in childhood RPA incidence and mortality. In many cases, infections which could have produced a case of RPA were resolved with antimicrobial therapy; recently, antimicrobial therapy has emerged as a conservative approach for some cases of RPA management. Over the past decade, particularly since 1999, we noted a recrudescence of medical reports on RPA, indicating an increase in the incidence of this entity. In this issue of the Southern Medical Journal, Abdel-Haq et al report 64 cases over a 10-year period, a 4.5-fold increase in RPA incidence, during the 1993 to 2003 period, as compared with the 1978 to 1989 period at the same institution. There was a sharp increase after the year 2000, with 16 cases in 2003, more than the highest previously reported multi-annual case rate of 12.8 per year. In other studies, the start of this increase occurs in 1995 or during the 1993 to 1998 period. This increased incidence may be partially explained by more accurate diagnoses, due, in part, to the increased use of contrast-enhanced computed tomography (CT). In instances where antibiotics are prescribed for the primary infection, RPA may remain undiagnosed. The positive predictive value of the CT scan was estimated to be between 84 to 94%. The increased incidence of RPA in children correlates with the emergence of group A -hemolytic Streptococcus (GABHS) as the pathogen of this clinical entity. Previous data indicated that Streptococcus viridans and Staphylococcus aureus were dominant organisms. In this report, GABHS was recovered in 54% of RPA cases with microbiologic findings compared with 35% in a previous study at the same institution. Similar emergences were reported in other series: 65% as found by Craig and Schunk, and 44% by Kirse and Roberson. Is this a real increase in GABHS involvement or not? Considering in vitro uniform GABHS susceptibility to penicillins and resistance problems with other pathogens, this explanation is highly improbable. The high rate of oropharyngeal infections as found by Abel-Haq et al (97%) indicates a real GABHS emergence. What implications may occur due to this change in RPAcausative pathogens? Concerning outcome, even GABHS infection could be severe in other sites; in RPA this virulence was not described. Concerning therapy, the antimicrobials most prescribed for RPA patients were aminopenicillin/ lactamase inhibitors or clindamycin with or without 2nd/ 3rd generation cephalosporins; GABHS susceptibility is constant for penicillins and very high for clindamycin, and some authors noted that these options could remain unchanged. However, in some areas, over the past 10 years, GABHS macrolide resistance has achieved high levels: 35.8% in Spain and 46% in Taiwan. Furthermore, several statistics indicate that 9 to 55% of macrolide-resistant GABHS strains are also resistant to clindamycin, and 20 to 25% to telithromycin. The misuse and abuse of macrolides will increase the rate of GABHS resistance and to related antibiotics (lincosamides, synergistins, ketolides), compromising clindamycin use as an initial regimen for RPA. Therefore, in areas with GABHS resistance to macrolides, there is a reason to prefer a penicillin-based initial regimen for RPA; this option will diminish the risk of septic complications and of poststreptococcal syndromes. In other areas, with a negligible risk of GABHS resistance to clindamycin, clindamycin in vitro efficiency is similar to penicillins, with the advantage of an antitoxic effect and an excellent oral bioavailability, and could be a better option. Some authors used clindamycin in monotherapy for RPA – without failures, but others, as in this issue, recommend an association with an antibiotic to cover some rare involved Gram negative rods—7 of 101 strains in their report. It is probable that efficient surgical drainage solves RPA, making the choice of a “best antibiotic” less important; furthermore, the recent series did not note any deaths, regardless of the received antibiotic regimen. Therefore, the choice of antibiotic therapy could have implications only on the rate of infection relapse and surgical re-intervention, or over illness duration. RPA is a rare and underdiagnosed illness, which makes it impossible to perform randomized, comparative clinical studies to define the optimal approach in every subpopulation of patients. Where it is possible, the surveillance of the GABHS resistance to macrolides, lincosamides, synergistins and ketolides should be done to update the efficacy of antimicrobial regimens for RPA. From the Infectious Diseases Department, “Matei Bals” Infectious Diseases Institute, Bucharest, Romania.