Abstract
An efficient technique was developed to monitor the emission of hydrogen and carbon dioxide from bacteria cultures by headspace gas chromatography and to investigate the efficacy of chemical antibiotics and of natural compounds with antimicrobial properties. Facultative anaerobes emit hydrogen and carbon dioxide from cultures in the closed headspace vials and obligate anaerobes too, if the air above the cultures in the vials is replaced by nitrogen. Antibiotics added to the sample cultures are apparently effective if the emission of hydrogen and carbon dioxide is suppressed. If not, either they are ineffective or the related bacteria are even resistant. The headspace technique can detect bacterial contamination in various samples, and examples are presented for food purchased from supermarkets and for medical specimens, including recognition of antibiotic resistance. However, the described technique cannot identify the related bacteria at a species or genus level, but is well suited for example for screening the bulk of food in supermarkets for microbe contamination or for the search of natural antibiotics. The samples are incubated with the proper nutrient medium in closed septum vials which remain closed during the whole process. The personnel in the lab never come into contact with pathogens, and thus, safety regulations are warranted. The described technique can be carried out with all commercially available gas chromatographs, even including simple low-cost instruments, equipped with a standard packed column and a thermal conductivity detector, up to expensive and fully automated instruments, such as used for forensic blood alcohol analysis.
Highlights
Bacteria emit volatile compounds, which are amenable to analysis by gas chromatography
Static headspace gas chromatography (HS-Gas chromatography (GC)) is well suited to analyze volatile compounds (VOCs) from bacterial cultures enclosed in septum vials
VOCs were the class of compounds that received the most study, free fatty acids emitted from bacterial cultures [4], even non-volatile organic acids are found amenable to static HS-GC after derivatization [5]
Summary
Bacteria emit volatile compounds, which are amenable to analysis by gas chromatography. Static headspace gas chromatography (HS-GC) is well suited to analyze volatile compounds (VOCs) from bacterial cultures enclosed in septum vials. VOCs were the class of compounds that received the most study, free fatty acids emitted from bacterial cultures [4], even non-volatile organic acids are found amenable to static HS-GC after derivatization [5]. The study presented here is focused on the determination of emitted hydrogen (H2) and carbon dioxide (CO2) to recognize bacterial contamination in various samples and to study the activity of chemical and natural antibiotics. For each of such applications, a typical example is presented
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