Epidemiology of mycobacterial resistance (especially Mycobacterium tuberculosis)

Еffect of the essential oil of <i>Satureja montana</i> L. on the growth of cultures of conditionally pathogenic microorganisms

Introduction. Essential oils contain antimicrobial components that are highly active against a wide range of microorganisms. Essential oils are natural, environmentally safe, low-toxic substances with a minimal list of side effects; no antimicrobial resistance is formed to them. The aim of the research was to study the influence of the essential oil of Satureja montana L., growing in the Crimea, on the growth of cultures of opportunistic microorganisms. Materials and methods. The short-term effect of savory oil on the growth of referenсе strains of microorganisms was studied in accordance with the European Standard for determining the rate of inactivation of microorganisms by the test substance (1997). To study the long-term effect of savory oil on clinical isolates of Staphylococcus aureus, we used the method of dilutions in a liquid medium, followed by measurement of the optical density of growth of the suspension culture biomass. The effect of savory oil on the formation of biofilms by clinical isolates of S. aureus was also studied. Results. Whole savory oil and its dilutions of 1 : 10 and 1 : 100 with short-term action (1060 min) completely suppressed the growth of referenсе strains of bacteria; growth of the referenсе strain Candida albicans CCM 885 was inhibited only by whole oil and a 1 : 10 dilution, while a 1 : 100 dilution had a bacteriostatic effect. Dilutions of essential oil 1 : 100 and 1 : 1000 had a pronounced antibacterial effect on the suspension culture of clinical isolates of S. aureus. Savory oil also inhibited biofilm formation by 11 isolates S. aureus. Conclusion. The essential oil of Satureja montana L. exhibits a pronounced antimicrobial effect against referenсе strains of S. aureus ATCC 25923, Escherichia coli ATCC 25922 and fungi C. albicans CCM 885. The antibacterial effect of this essential oil on clinical isolates of S. aureus allows us to offer it as a component of combined preparations for the treatment of infections caused by antibiotic-resistant strains of staphylococcus.

Comparison of the manual Mycobacteria Growth Indicator tube and the Etest with the method of proportion for susceptibility testing of Mycobacterium tuberculosis

BACKGROUND

Clinical microbiology laboratories should provide reliable results on susceptibility testing of Mycobacterium tuberculosis to different agents.

METHODS

The manual Mycobacteria Growth Indicator Tube (MGIT) and Etest were compared to the method of proportion (MOP) for susceptibility testing of 88 clinical isolates of M. tuberculosis against isoniazid (INH), rifampin (RIF), streptomycin (STR) and ethambutol (EMB). Isolates were recovered from different patients and were identified at species level by PCR and hybridization.

RESULTS

Resistance to INH was detected in 20.5, 29.5 and 12.5% of the isolates, followed by STR resistance (19.3, 26.1 and 1.1%), RIF (9.1, 4.5 and 5.7%) and EMB (2.3, 11.4 and 2.3%) by the MOP, MGIT and Etest, respectively. Sensitivity of the manual MGIT ranged from 37.5% for RIF resistance to 100% for EMB, while Etest sensitivity ranged from 5.9% for STR to 62.5% for RIF.

CONCLUSIONS

MOP remains the method of choice, with the manual MGIT showing superior sensitivity at detecting resistance to INH, STR and EMB compared to the Etest.