SummaryA globally disseminated strain of M1T1 group A Streptococcus (GAS) has been associated with severe infections in humans including necrotizing fasciitis and toxic shock syndrome. Recent clinicoepidemiologic data showed a striking inverse relationship between disease severity and the degree to which M1T1 GAS express the streptococcal cysteine protease, SpeB. Electrophoretic 2-D gel analysis of the secreted M1T1 proteome, coupled with MALDI-TOF mass spectroscopy, revealed that expression of active SpeB caused the degradation of the vast majority of secreted GAS proteins, including several known virulence factors. Injection of a SpeB + + + +

The group A Streptococcus (GAS) sof gene encodes the serum opacity factor protein, which is capable of opacifying mammalian sera and binding at least two host proteins, fibronectin and fibrinogen. The sof gene exists in approximately 50% of clinical isolates, and there is a classical association of so-called nephritogenic strains with the opacity factor-positive phenotype. In both a type emm49 strain and a type emm12 strain, the sequences upstream of the 5 end of sof and downstream of the putative terminator were determined to be nearly identical to a region in the M type 1 genome approximately 10 kb upstream of the emm1 gene. This close genetic linkage is likely reflected in the strict correlation of opacity factor phenotype with specific emm genotypes. A new fibronectin-binding protein gene, sfbX, was discovered immediately downstream of sof in emm12 and emm49 strains and in several other sof-positive strains. The sof and sfbX genes were found to be expressed on the same transcription unit, which was correlated with the putative promoter and rho-independant terminator sequences that flank these two genes. The sfbX genes from different emm types are predicted to encode ϳ650-residue surface-bound proteins sharing 89 to 92% sequence identity. SfbX residues approximately 1 to 480 are not highly similar to those of other known proteins, with the closest match being the Staphylococcus aureus coagulase protein. The remaining portions of these proteins (residues 481 to 650) contain four putative fibronectin-binding repeats highly similar to those of other streptococcal fibronectin-binding proteins and a potential LP(X)SG cell wall anchor motif. Targeted in-frame allelic-exchange mutagenesis, complementation, and heterologous-expression studies found that serum opacification is encoded by sof alone and that sfbX encodes a fibronectin-binding function. A recombinant SfbX protein was found to bind immobilized fibronectin and to partially inhibit GAS adherence to fibronectin. The sfbX gene was found to be present only in sof-positive strains, and together these genes could influence the spectrum of tissues colonized by sof-positive GAS.

Study objective Randomized trials suggest that nonoperative treatment of uncomplicated appendicitis with antibiotics-first is safe. No trial has evaluated outpatient treatment and no US randomized trial has been conducted, to our knowledge. This pilot study assessed feasibility of a multicenter US study comparing antibiotics-first, including outpatient management, with appendectomy. Methods Patients aged 5 years or older with uncomplicated appendicitis at 1 US hospital were randomized to appendectomy or intravenous ertapenem greater than or equal to 48 hours and oral cefdinir and metronidazole. Stable antibiotics-first-treated participants older than 13 years could be discharged after greater than or equal to 6-hour emergency department (ED) observation with next-day follow-up. Outcomes included 1-month major complication rate (primary) and hospital duration, pain, disability, quality of life, and hospital charges, and antibiotics-first appendectomy rate. Results Of 48 eligible patients, 30 (62.5%) consented, of whom 16 (53.3%) were randomized to antibiotics-first and 14 (46.7%) to appendectomy. Median age was 33 years (range 9 to 73 years), median WBC count was 15,000/μL (range 6,200 to 23,100/μL), and median computed tomography appendiceal diameter was 10 mm (range 7 to 18 mm). Of 15 antibiotic-treated adults, 14 (93.3%) were discharged from the ED and all had symptom resolution. At 1 month, major complications occurred in 2 appendectomy participants (14.3%; 95% confidence interval [CI] 1.8% to 42.8%) and 1 antibiotics-first participant (6.3%; 95% CI 0.2% to 30.2%). Antibiotics-first participants had less total hospital time than appendectomy participants, 16.2 versus 42.1 hours, respectively. Antibiotics-first-treated participants had less pain and disability. During median 12-month follow-up, 2 of 15 antibiotics-first-treated participants (13.3%; 95% CI 3.7% to 37.9%) developed appendicitis and 1 was treated successfully with antibiotics; 1 had appendectomy. No more major complications occurred in either group. Conclusion A multicenter US trial comparing antibiotics-first to appendectomy, including outpatient management, is feasible to evaluate efficacy and safety.

Staphylococcus aureus and beta-hemolytic streptococci (BHS) are the 2 main types of bacteria causing soft-tissue infections. Historically, BHS were believed to be the primary cause of diffuse, nonculturable cellulitis. However, with the recent epidemic of community-associated methicillin-resistant S aureus (MRSA) causing culturable soft-tissue infections, it is currently unclear what role either of these bacteria has in cases where the cellulitis is diffuse and nonculturable. This uncertainty has led to broad-spectrum and haphazard use of antibiotics for this infection type, which has led to increased risk of adverse drug reactions, health care costs, and emergence of resistance in bacteria. To investigate this issue, we conducted a prospective investigation between December 2004 and June 2007, enrolling all adult patients admitted to the inpatient service at the Olive View-UCLA Medical Center, a county hospital of Los Angeles, with diffuse, nonculturable cellulitis. Acute and convalescent serologies for anti-streptolysin-O and anti-DNase-B antibodies were obtained. Patient data were analyzed for response to beta-lactam antibiotics. The primary outcome was the proportion of these cases caused by BHS, as diagnosed by serologies and/or blood cultures, and the secondary outcome was the response rate of patients to beta-lactam antibiotics. Of 248 patients enrolled, 69 were dropped from analysis because of loss to follow-up or exclusion criteria. Of the 179 remaining patients, 73% of nonculturable cellulitis cases were caused by BHS. Analysis of outcomes to beta-lactam antibiotic treatment revealed that patients diagnosed with BHS had a 97% (71/73) response, while those who did not have BHS had a 91% (21/23) response, with an overall response rate of 95.8% (116/121). Results of this large, prospective study show that diffuse, nonculturable cellulitis is still mainly caused by BHS, despite the MRSA epidemic, and that for this infection type, treatment with beta-lactam antibiotics is still effective. A cost-effective, evidence-based algorithm can be useful for the empiric management of uncomplicated soft-tissue infections based on the presence or absence of a culturable source.

Streptococcal pyrogenic exotoxin (Spe) B, a streptococcal cysteine protease, is believed to be important in group A streptococcal (GAS) pathogenesis. The present study examined the effect of SpeB on the activity of superantigenic exotoxins secreted by M1T1 GAS isolates. The proliferative response of human lymphocytes to culture supernatant (SUP) from an SpeB(+) isolate increased significantly (P<.05) when the isolate was grown with N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]-agmatine, a cysteine protease inhibitor. The lymphocyte-stimulating activity of SUP from a spontaneous SpeB(-) variant or SpeB(-) knockout (DeltaSpeB) mutant was also significantly higher than that of SUP from the SpeB(+) parent isolate (P<.001). The addition of recombinant SpeB to the DeltaSpeB mutant reduced the lymphocyte response to a level comparable to that with the SpeB(+) isolate. SpeB affected superantigens that stimulate cells expressing T cell receptor Vbeta (TCRBV)-4, TCRBV7, and TCRBV8 but not those that stimulate TCRBV2. SpeB has a selective proteolytic effect on GAS superantigens.