Bactericidal activity of combinations of gentamicin with penicillin or clindamycin against Streptococcus mutans

Inhibition of Streptococcus mutans biofilms with bacterial-derived outer membrane vesicles

BACKGROUND

Biofilms are microbial communities surrounded by a self-produced extracellular matrix which protects them from environmental stress. Bacteria within biofilms are 10- to 1000-fold more resistant to antibiotics, making it challenging but imperative to develop new therapeutics that can disperse biofilms and eradicate infection. Gram-negative bacteria produce outer membrane vesicles (OMV) that play critical roles in communication, genetic exchange, cargo delivery, and pathogenesis. We have previously shown that OMVs derived from Burkholderia thailandensis inhibit the growth of drug-sensitive and drug-resistant bacteria and fungi.

RESULTS

Here, we examine the antibiofilm activity of Burkholderia thailandensis OMVs against the oral biofilm-forming pathogen Streptococcus mutans. We demonstrate that OMV treatment reduces biofilm biomass, biofilm integrity, and bacterial cell viability. Both heat-labile and heat-stable components, including 4-hydroxy-3-methyl-2-(2-non-enyl)-quinoline and long-chain rhamnolipid, contribute to the antibiofilm activity of OMVs. When OMVs are co-administered with gentamicin, the efficacy of the antibiotic against S. mutans biofilms is enhanced.

CONCLUSION

These studies indicate that bacterial-derived OMVs are highly effective biological nanoparticles that can inhibit and potentially eradicate biofilms.

AZDAST the new horizon in antimicrobial synergism detection

The attempts via introducing many methods have been conducted to select the best antibiotic combination in the treatment of seriously ill patients. Operational or interpretational complexity or time-consuming along with sufficient accuracy led to postpone routine clinical use of these tests until today, despite the urgent need for them. By this study and proposed method, selection of the best double antibiotic synergistic combination against resistant pathogen is simply same as Kirby-Bauer antibiotic susceptibility test. It seems, precise and reliable results (very low coefficient of variation) will be introduced it as a routine accurate diagnostic doubled antimicrobial synergism test.•

The objective of this study was to introduce a novel method in antibiotic interaction detection.

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It demonstrates high sensitivity and accuracy.

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Easy implementation by routine microbiology labs materials and equipment and so easy stand-alone interpretation seems to make it friendly test be able to replacing the previous methods.

Bacterial endocarditis due to penicillin-resistant Streptococcus viridans

Bacterial endocarditis remains a formidable diagnostic and therapeutic problem for clinicians. Streptococcus viridans still accounts for 45 to 50 per cent of all cases and between 5 to 10 per cent of all clinical isolates of Streptococcus viridans from patients with bacterial endocarditis may be relatively resistant to penicillin. The case of a 9-year-old child with Tetralogy of Fallot and a Waterston shunt who subsequently developed bacterial endocarditis due to penicillin-resistant Streptococcus viridans following failure of oral penicillin dental prophylaxis is presented. In the face of penicillin resistance, additional considerations for workup, including microbiological assays for antimicrobial synergism become necessary in the selection of a therapeutic regimen.

Bactericidal activity of the combinations of gentamicin with clindamycin or chloramphenicol against species of Escherichia coli and Bacteroides fragilis

The bactericidal activity of clindamycin, chloramphenicol, and gentamicin alone and of gentamicin plus clindamycin and gentamicin plus chloramphenicol was studied on 8 strains of Escherichia coli and 10 strains of Bacteroides fragilis isolated from clinical material. Gentamicin did not interfere with the activity of clindamycin or chloramphenicol against B. fragilis. The activity of gentamicin against E. coli was not influenced by clindamycin, but chloramphenicol suppressed the rapid bactericidal activity of gentamicin in seven out of eight strains of E. coli examined.

Empyema due to Streptococcus mutans

Empyema due to Streptococcus mutans occurred following dental manipulation in two patients with periodontal disease. Isolation of this dental pathogen from pleural fluid localized the site of origin of the empyemas to the oropharynx and precluded the need to search for a remote intra-abdominal source of these pleuropulmonary infections. Although there is controversy regarding the susceptibility of S mutans to penicillin, the isolates from our patients were markedly sensitive to the drug, and both patients were cured with penicillin therapy and surgical drainage.

Bactericidal activity of combinations of penicillin or clindamycin with gentamicin or streptomycin against species of viridans streptococci

Checkerboard bactericidal studies were performed with two strains each of Streptococcus mitis, S. salivarius, and S. sanguis, and the results were analyzed by the use of isobolograms. Synergy between penicillin and streptomycin or gentamicin was demonstrated with four strains, representing two of S. salivarius, one of S. sanguis, and one of S. mitis; the remainder were either too susceptible or too resistant to be analyzed. Clindamycin with streptomycin or gentamicin acted synergistically with three strains, representing two of S. sanguis and one of S. salivarius; the remainder were either too susceptible or too resistant to be analyzed.