The antimicrobial susceptibility of Mycobacterium tuberculosis H37Rv and 17 clinical isolates of the same species was determined using a bioluminescence assay to measure adenosine triphosphate (ATP) produced by bacteria in the broth dilution test performed in Dubos-Tween-albumin broth. The results were compared with those obtained with the standard dilution proportional method performed on Löwenstein-Jensen medium. The drugs tested were streptomycin, rifampin, ethambutol and isoniazid. There was high correlation between bacterial count and ATP concentration in a liquid culture of Mycobacterium tuberculosis H37Rv (r = 0.993); when several cultures of the same strain were assayed after different incubation periods the correlation was somewhat lower (r = 0.846). Addition of tuberculostatic drugs in inhibitory concentrations resulted in a reduction in the ATP concentration as compared to control assays without drugs. Results of susceptibility tests performed by the two methods agreed in 66 out of 68 assays. Differences in the inhibitory concentrations determined by the two methods were due to differences in the methods. Whereas the standard method requires 3 to 4 weeks of incubation, results of the bioluminescence assay were available after five days of incubation. Automation of the assay for routine use is possible.

We are currently facing an antimicrobial resistance crisis, which means that a lot of bacterial pathogens have developed resistance to common antibiotics. Hence, novel and innovative solutions are urgently needed to combat resistant human pathogens. A new source of antimicrobial compounds could be bacterial volatiles. Volatiles are ubiquitous produced, chemically divers and playing essential roles in intra- and interspecies interactions like communication and antimicrobial defense. In the last years, an increasing number of studies showed bioactivities of bacterial volatiles, including antibacterial, antifungal and anti-oomycete activities, indicating bacterial volatiles as an exciting source for novel antimicrobial compounds. In this review we introduce the chemical diversity of bacterial volatiles, their antimicrobial activities and methods for testing this activity. Concluding, we discuss the possibility of using antimicrobial volatiles to antagonize the antimicrobial resistance crisis.

Social arthropods such as termites, ants, and bees are among others the most successful animal groups on earth. However, social arthropods face an elevated risk of infections due to the dense colony structure, which facilitates pathogen transmission. An interesting hypothesis is that social arthropods are protected by chemical compounds produced by the arthropods themselves, microbial symbionts, or plants they associate with. Stegodyphus dumicola is an African social spider species, inhabiting communal silk nests. Because of the complex three-dimensional structure of the spider nest antimicrobial volatile organic compounds (VOCs) are a promising protection against pathogens, because of their ability to diffuse through air-filled pores. We analyzed the volatilomes of S. dumicola, their nests, and capture webs in three locations in Namibia and assessed their antimicrobial potential. Volatilomes were collected using polydimethylsiloxane (PDMS) tubes and analyzed using GC/Q-TOF. We showed the presence of 199 VOCs and tentatively identified 53 VOCs. More than 40% of the tentatively identified VOCs are known for their antimicrobial activity. Here, six VOCs were confirmed by analyzing pure compounds namely acetophenone, 1,3-benzothiazole, 1-decanal, 2-decanone, 1-tetradecene, and docosane and for five of these compounds the antimicrobial activity were proven. The nest and web volatilomes had many VOCs in common, whereas the spider volatilomes were more differentiated. Clear differences were identified between the volatilomes from the different sampling sites which is likely justified by differences in the microbiomes of the spiders and nests, the plants, and the different climatic conditions. The results indicate the potential relevance of the volatilomes for the ecological success of S. dumicola.