HTC-15 - Abstract

Abstract Title: Detection of bacteriologically produced hydrogen sulphide using SHS-MCC-GC-IMS
Abstract Type: Seminar
Presenter Name: Prof John Dean
Co-authors:Mr Ryan Thompson
Prof Stephen Stanforth
Prof John Perry
Company/Organisation: Northumbria University
Session Choice: Clinical Hyphenations

Abstract Information :

Hydrogen sulphide (H2S) is a volatile airborne compound with the characteristic rotten egg odour at low concentrations, and is commonly associated with bacterial contamination of food and water sources. Current tests employed for the detection of bacterial H2S rely on specialised growth mediums that are rich in sulphur, usually in the form of sodium thiosulphate, cysteine, or cystine, to induce significant production of H2S. These mediums are also combined with a visible colour change following incubation; usually facilitated via ferric ammonium citrate or lead acetate, both of which form a black precipitate upon contact with H2S.

One of the primary drawbacks of current methods are the subjective nature of the results interpretation, which essentially ask the question 'how black is black?' We propose a new method for rapid and sensitive detection of H2S using static headspace - multi capillary column - gas chromatography - ion mobility spectrometry (SHS-MCC-GC-IMS). Our new method allows for sensitive detection and quantification of H2S evolved into the gaseous headspace above a bacterial suspension. Fresh colonies taken from day old Tryptone Soy Agar plates were suspended in nitrate broth and adjusted to an inoculum of 105 CFU/ml, which were then sealed in headspace vials and incubated overnight at 37°C. Following incubation, 2.5 mL of the gaseous headspace above the suspension was extracted and analysed via SHS-MCC-GC-IMS. Nitrate broth (potassium nitrate 1 g/L, peptone 5 g/L, meat extract 2.4 g/L, pH 7.4)3 was the chosen medium due to its non-selective nature and inexpensive constituents, thereby removing the need for expensive specialised growth media.

Hydrogen sulphide detection via MCC-SHS-GC-IMS was found to be extremely sensitive, allowing for quantification as low as 5 ppb. A diverse range of bacteria were tested, many of which the H2S production status was undefined by current methods, such as B. cereus and E. cloacae. Interestingly, this method also detected consistent H2S production in 2 of 6 tested E. coli strains, a species which is largely classified as H2S negative according to standard testing procedures4.This method shows great promise for a rapid and extremely sensitive analytical technique for the detection and quantification of H2S. Future applications could include detection of bacterial contamination in food and water sources, and bacteria in various human clinical samples e.g. blood from suspected sepsis patients.