SP-CHAP, an endolysin with enhanced activity against biofilm pneumococci and nasopharyngeal colonization

Streptococcus pneumoniae (Spn), a Gram-positive bacterium, is responsible for causing a wide variety of invasive infections. The emergence of multi-drug antibiotic resistance has prompted the search for antimicrobial alternatives. Phage-derived peptidoglycan hydrolases, known as endolysins, are an attractive alternative. In this study, an endolysin active against Spn, designated SP-CHAP, was cloned, produced, purified, biochemically characterized, and evaluated for its antimicrobial properties. Cysteine, histidine-dependent amidohydrolase/peptidase (CHAP) domains are widely represented in bacteriophage endolysins but have never previously been reported for pneumococcal endolysins. Here, we characterize the first pneumococcal endolysin with a CHAP catalytic domain. SP-CHAP was antimicrobial against all Spn serovars tested, including capsular and capsule-free pneumococci, and it was found to be more active than the most widely studied pneumococcal endolysin, Cpl-1, while not affecting various oral or nasal commensal organisms tested. SP-CHAP was also effective in eradicating Spn biofilms at concentrations as low as 1.56 µg/mL. In addition, a Spn mouse nasopharyngeal colonization model was employed, which showed that SP-CHAP caused a significant reduction in Spn colony-forming units, even more than Cpl-1. These results indicate that SP-CHAP may represent a promising alternative to combating Spn infections.

IMPORTANCE

Considering the high rates of pneumococcal resistance reported for several antibiotics, alternatives are urgently needed. In the present study, we report a Streptococcus pneumoniae-targeting endolysin with even greater activity than Cpl-1, the most characterized pneumococcal endolysin to date. We have employed a combination of biochemical and microbiological assays to assess the stability and lytic potential of SP-CHAP and demonstrate its efficacy on pneumococcal biofilms in vitro and in an in vivo mouse model of colonization. Our findings highlight the therapeutic potential of SP-CHAP as an antibiotic alternative to treat Streptococcus pneumoniae infections.

The effect of normalization of serum complement and anti-DNA antibody on the course of lupus nephritis: a two year prospective study

A prospective study was carried out in 25 patients with systemic lupus erythematosis (SLE) on the effect of normalizing serum complement (CH50) and anti-DNA antibodies on the course of lupus nephritis. In 16 of the 25 patients, CH50 was maintained within the normal range for two years. Urinary protein excretion increased or remained low in all 16. Repeat renal biopsies were performed in 10 of these 16, and disclosed either stabilization of glomerular disease or diminution. In the nine patients in whom CH50 could not be normalized with tolerated doses of drugs, urinary protein excretion increased or remained increased. Repeat renal biopsies in six of these nine patients were carried out and showed worsening of glomerular disease in five. No clear-cut correlation was found between urinary protein excretion or renal disease and the serum levels of anti-DNA antibody. We conclude from these observations that continuous normalization of CH50 by drug therapy in patients with SLE is associated with stabilization or diminution of lupus nephritis.