Streptococcus intermedius liver abscesses and colon cancer: a case report

Certain species of bacteria are known to be associated with colorectal cancer. We report a case of adenocarcinoma of the colon with bacteraemia and liver abscesses due to Streptococcus intermedius. The isolation of this organism should prompt investigation for colorectal neoplasm, which may be present but asymptomatic, without metastases, and therefore at a curative stage.

Fluoroquinolone resistance is a poor surrogate marker for type II topoisomerase mutations in clinical isolates of Streptococcus pneumoniae

The association between fluoroquinolone susceptibility and DNA mutations coding for amino acid substitutions in the quinolone resistance-determining region was assessed with 44 clinical isolates of Streptococcus pneumoniae. Twenty-three strains bore at least one amino acid substitution. Only seven strains with mutations were suggested by diminished susceptibility to ciprofloxacin (MIC, > or =2 microg/ml).

Intracellular targets of moxifloxacin: a comparison with other fluoroquinolones

The in vitro activity of the novel 8-methoxyquinolone, moxifloxacin, against Streptococcus pneumoniae was evaluated, and the intracellular targets of this agent were studied. Analysis of mutant strains selected with moxifloxacin demonstrated that first-step mutants bore amino acid substitutions at position 81 in the GyrA subunit of DNA gyrase. This suggests that, unlike older fluoroquinolone agents such as ciprofloxacin and levofloxacin, but similar to other C-8 substituted quinolones like sparfloxacin and gatifloxacin, moxifloxacin targets the GyrA subunit of DNA gyrase as an initial lethal event. Such a mechanism results in high activity against increasingly common S. pneumoniae strains bearing substitutions in DNA topoisomerase IV. Moxifloxacin was active with an MIC of </= 0.25 mg/L against S. pneumoniae clinical isolates, and against mutants, selected in the laboratory with ciprofloxacin or levofloxacin, that bore a Ser-79-->Phe/Tyr substitution in ParC. The moxifloxacin MIC for strains with mutations in the structural genes for both DNA gyrase subunit GyrA and DNA topoisomerase IV subunit ParC did not exceed 2 mg/L, a level within clinically achievable serum concentrations for this agent. We also found that moxifloxacin is a poor substrate for active efflux in S. pneumoniae. Therefore, the high activity of moxifloxacin against S. pneumoniae appears to be a result of both enhanced activity against DNA gyrase and topoisomerase IV, and reduced efflux from the bacterial cell.

A convenient assay for estimating the possible involvement of efflux of fluoroquinolones by Streptococcus pneumoniae and Staphylococcus aureus: evidence for diminished moxifloxacin, sparfloxacin, and trovafloxacin efflux

We developed a simplified assay for estimating efflux by measuring the effect of reserpine on the growth of Streptococcus pneumoniae and Staphylococcus aureus over 7 h. Reserpine enhanced ciprofloxacin and levofloxacin 17 to 68%. The hydrophobic drug trovafloxacin and the drug moxifloxacin, with a bulky C-7 substituent but hydrophilicity similar to that of levofloxacin, showed little (0 to 11%) reserpine-enhancing effect. The ease of resistant mutant strain selection correlated with efflux susceptibility.