INVASIVE GROUP A STREPTOCOCCAL INFECTIONS

Isolation rate, T-serotyping and susceptibility to antibiotics of Group A Streptococcus from pediatric infections in Athens

OBJECTIVE

The epidemiology of Group A Streptococcus (GAS) in Greece is not known. We have therefore conducted this prospective study to investigate the isolation rate of GAS from pediatric specimens, determine T-serotype frequency and examine the susceptibility of GAS to penicillin, erythromycin and clindamycin.

METHODS

Over a 3-year study-period (1993-95) 11 597 clinical specimens obtained from sick children were inoculated on appropriate culture media. The isolation and identification of GAS strains were assessed by conventional methods. T-typing was performed by slide agglutination. Serum opacity factor (OF) was detected by microwell

METHOD

The susceptibility of the strains was tested by the Kirby Bauer method.

RESULTS

GAS were isolated from 1125 out of 11 597 (9.7%) clinical specimens, mostly from throat samples (15.6%). T-serotyping was performed in 652 GAS strains. A significant difference of the incidence of T-serotypes was observed within the 3 years studied (chi2 = 70.3, DF = 18, P < 0.001). The most dominant isolates were T-1 (25%), T-4 (20%) and T-12 (16%) during 1993, 1994 and 1995, respectively. Non-typeable (NT) strains were 4%. OF and hyaluronic acid were produced from 49.8% and 3% of the strains, respectively. All isolated strains were susceptible to penicillin and clindamycin. Resistance to erythromycin was 5.0-8.7% over the 3-year study period.

CONCLUSIONS

There was a wide distribution of GAS T-serotypes in Athens and a significant change in their annual predominance. All strains were susceptible to penicillin and clindamycin, but a low level of erythromycin resistance was observed.

Development of streptococcal pyrogenic exotoxin C vaccine toxoids that are protective in the rabbit model of toxic shock syndrome

Streptococcal pyrogenic exotoxin C (SPE C) is a superantigen produced by many strains of Streptococcus pyogenes that (along with streptococcal pyrogenic exotoxin A) is highly associated with streptococcal toxic shock syndrome (STSS) and other invasive streptococcal diseases. Based on the three-dimensional structure of SPE C, solvent-exposed residues predicted to be important for binding to the TCR or the MHC class II molecule, or important for dimerization, were generated. Based on decreased mitogenic activity of various single-site mutants, the double-site mutant Y15A/N38D and the triple-site mutant Y15A/H35A/N38D were constructed and analyzed for superantigenicity, toxicity (lethality), immunogenicity, and the ability to protect against wild-type SPE C-induced STSS. The Y15A/N38D and Y15A/H35A/N38D mutants were nonmitogenic for rabbit splenocytes and human PBMCs and nonlethal in two rabbit models of STSS, yet both mutants were highly immunogenic. Animals vaccinated with the Y15A/N38D or Y15A/H35A/N38D toxoids were protected from challenge with wild-type SPE C. Collectively, these data indicate that the Y15A/N38D and Y15A/H35A/N38D mutants may be useful as toxoid vaccine candidates.

Streptococcal toxic shock syndrome presenting as suspected child abuse

Natural disease processes can predispose individuals to develop external body lesions that mimic traumatic injury. This can be particularly problematic in pediatric cases in which clinicians are alerted to the problems of child abuse. Streptococcal toxic shock syndrome is a systemic infectious illness that can manifest itself with erythematous and necrotizing skin lesions. We report a fatal case of streptococcal toxic shock syndrome in a 4-year-old girl who presented with skin lesions that were initially thought to be traumatic in origin. A report of possible child abuse was filed with the state. Based on the morphologic findings and bacteriologic culture results at autopsy, these lesions and the cause of death in this case were instead determined to result from streptococcal toxic shock syndrome.

In vitro activity of cefepime and ceftazidime against 197 nosocomial blood stream isolates of streptococci: a multicenter sample

The increasing prevalence of streptococci as causes of potentially fatal nosocomial bacteremia requires that antimicrobial agents used for empiric therapy in hospitalized patients include both pneumococci and viridans group streptococci as well as beta-hemolytic streptococci in their activity profile. In this study, the in vitro activity of cefepime, a new fourth-generation cephalosporin, was compared with other cephalosporins versus 197 nosocomial blood stream isolates of streptococci (20 Streptococcus pneumoniae, 104 viridans group, and 73 beta-hemolytic) isolated from patients at more than 30 medial centers from 1995 to 1997. Additional agents tested included penicillin, erythromycin, and vancomycin. Overall, cefepime inhibited 83% of the isolates at concentrations < or = 0.5 microgram/mL and 100% at < or = 8 micrograms/mL. By comparison, ceftazidime inhibited 35 and 88% of isolates at the same concentrations. Cefepime was approximately eightfold more potent than ceftazidime against S. pneumoniae, viridans group streptococci, and beta-hemolytic streptococci. Among the 42 isolates with penicillin MICs > 0.12 microgram/mL, 100% were inhibited by cefepime and only 48% by ceftazidime at < or = 8 micrograms/mL. The rank order of activity for all six agents against the 197 isolates was vancomycin > ceftriaxone > cefepime > penicillin > erythromycin > ceftazidime. Based on the results of the present study, cefepime and ceftriaxone were the superior cephalosporins in potency and spectrum for empiric coverage of patients at risk for streptococcal blood stream infections.

Comparative antistreptococcal activity of two newer fluoroquinolones, levofloxacin and sparfloxacin

The objective of this study was to evaluate the in vitro activity of sparfloxacin, levofloxacin, ofloxacin, and ciprofloxacin against contemporary strains of streptococci. Susceptibility testing of a panel of 300 recent clinical isolates of streptococci (100 each of beta-hemolytic, viridans group, and Streptococcus pneumoniae) using reference broth microdilution methods was performed, and the results were compared. Sparfloxacin was the most active of the four tested fluoroquinolones, inhibiting 99-100% of all isolates at concentrations of < or = 1 microgram/ml, and was two- to eightfold more potent than the three comparative agents. Levofloxacin was also quite active, inhibiting 98-100% of the isolates at concentrations < or = 2 micrograms/ml. Both sparfloxacin and levofloxacin possess an improved spectrum and potency against contemporary strains of streptococci compared to currently available fluoroquinolones.

Streptococcal toxic shock-like syndrome: case report and review of the literature

Streptococcal toxic shock-like syndrome is a newly recognized complication of infections by group A beta-haemolytic streptococci (GABHS). Previous reports of this syndrome have originated from developed countries, predominantly North American and Europe. This report describes a 5-year-old Saudi child who developed this syndrome in association with streptococcal pharyngitis. It indicates that the recent resurgence of severe GABHS diseases is a global phenomenon.