Novel strategy for biofilm inhibition by using small molecules targeting molecular chaperone DnaK.

Biofilms are complex communities of microorganisms that attach to surfaces and are embedded in a self-produced extracellular matrix. Since these cells acquire increased tolerance against antimicrobial agents and host immune systems, biofilm-associated infectious diseases tend to become chronic. We show here that the molecular chaperone DnaK is important for biofilm formation and that chemical inhibition of DnaK cellular functions is effective in preventing biofilm development. Genetic, microbial, and microscopic analyses revealed that deletion of the dnaK gene markedly reduced the production of the extracellular functional amyloid curli, which contributes to the robustness of Escherichia coli biofilms. We tested the ability of DnaK inhibitors myricetin (Myr), telmisartan, pancuronium bromide, and zafirlukast to prevent biofilm formation of E. coli. Only Myr, a flavonol widely distributed in plants, inhibited biofilm formation in a concentration-dependent manner (50% inhibitory concentration [IC50] = 46.2 µM); however, it did not affect growth. Transmission electron microscopy demonstrated that Myr inhibited the production of curli. Phenotypic analyses of thermosensitivity, cell division, intracellular level of RNA polymerase sigma factor RpoH, and vulnerability to vancomycin revealed that Myr altered the phenotype of E. coli wild-type cells to make them resemble those of the isogenic dnaK deletion mutant, indicating that Myr inhibits cellular functions of DnaK. These findings provide insights into the significance of DnaK in curli-dependent biofilm formation and indicate that DnaK is an ideal target for antibiofilm drugs.

[Comparison of the effects of traditional and modern processing methods on antibacterial and anti-inflammatory effects of Musca domestica].

OBJECTIVE: To investigate the different effects of traditional and modern processing methods onantibacterial and anti-inflammatory effects of Musca domestica. METHODS: Antibacterial and anti-inflammatory effects of traditional and modem processing products were carried out on Staphylococcus aureus, Escherichia coli and macrophage RAW264.7 which activated by LPS. RESULTS: The antibacterial and anti-inflammatory effects were more pronounced in modern processing product treatment group than those of traditional processing product treatment group. CONCLUSION: Modern processing technology can protect the substances in Musca domestica which have antibacterial and anti-inflammatory effects.

[Comparison of properties of Mahuang decoction and Maxing Shigan decoction based on biothermodynamics].

OBJECTIVE: To probe into the objectivity and authenticity of four properties beteen Mahuang decoction and Maxing Shigan decoction from biothermodynamics. METHOD: The power-time curves of growth of Staphylococcus aureus at different concentrations between Mahuang decoction and Maxing Shigan decoction were determined by TAM Air Isothermal Calorimeter. The growth rate constants of promotive and inhibitory actions were calculated. Moreover, the difference of properties beteen Mahuang decoction and Maxing Shigan decoction was analyzed from the point of view of TCM theory. RESULT: Both the Mahuang decoction and Maxing Shigan decoction could inhibit the growth and metabolism of Staphylococcus aureus. The k and Pm were decreased with the mass increase of the decoction. However, inhibitory activity of Mahuang decoction with warm property was weaker than that of Maxing Shigan decoction with cool property. Moreover, Mahuang decoction decreased heat output in growth metabolism more weakly than Maxing Shigan decoction. There was a stable difference between them. CONCLUSION: Studying on biothermodynamics can show the difference of four properties of Traditional Chinese Medicine. So, it provides a new and useful means for the study of the properties of traditional Chinese medicine.

[Analysis on processing mechanism of calamine].

OBJECTIVE: To study processing method and mechanism of Calamine. METHOD: Thermogravimetry analysis method and nano-technology were adopted to analyze and synthesize the components in Calamine, Tetracycline was took as the comparison drug to determine the antibacterial activity of Calamine and its components. RESULT: A part of zinc carbonate in Calamine was decomposed into zinc oxide when processing, and the particle size was smaller than before. The antibacterial activity of Calamine is decided by the content and particle size of zinc oxide, and has nothing with zinc carbonate. The more content and the smaller particle size of zinc oxide, the more powerful antibacterial activity of Calamine. CONCLUSION: The content and the particle size of zinc oxide can be the important targets in the processing of Calamine.

Use of simulated blood cultures for antibiotic effect on time to detection of the two blood culture systems BacT/ALERT and BACTEC 9240.

To avoid the influence of pre-analytical steps, this study was performed using sterile blood spiked with defined loads of microorganisms as inoculum. Time-to-Detection (TTD) was evaluated for the most frequently encountered bacteria comparing two commercially available blood culture systems, BD BACTEC 9240 (Becton Dickinson) and BacT/ALERT (Organon Teknika). The effect of the most widely used antibiotics on TTD was evaluated on both systems. TTD was measured with antibiotics at their trough and at increasing concentrations. The results show that the BACTEC PLUS system recovers more pathogens with shorter time to detection than the BacT/ALERT FAN system when beta-lactam antibiotics (Ampicillin, Cefotaxime) are present at their respective trough concentration corresponding to parenteral therapy. The two systems seem to be equally efficient when Gentamicin, Ciprofloxacin and Trimethoprim/sulfamethoxazole are used; in the case of Vancomycin, BACTEC seems more effective than BacT/ALERT.

Skin disease presenting as an outbreak of pseudobacteremia in a laboratory worker.

An outbreak of pseudobacteremia due to Streptococcus pyogenes (group A streptococci [GAS]) and methicillin-susceptible Staphylococcus aureus (MSSA) was traced to the venting procedure for aerobic bottles prior to their loading into the incubator of the BacT/Alert analyzer (Organon Teknika). Bacteria shed by a laboratory worker suffering from impetigo and cellulitis contaminated the aerobic bottles of 10 patients. All blood culture isolates, in addition to the isolates from the laboratory worker, were of the same GAS M and T types. All MSSA isolates from blood cultures and the index case's hands had the same lytic phage profile. Procedural breakdowns were identified in the laboratory. Bottles were vented outside the biological safety cabinet, gloves were not worn, and unprotected needles were used for the venting procedure. The source of the aspirated bacteria that contaminated the bottles was identified and the index case was treated promptly.