Sensors and Actuators B 109 (2005) 355–362 Identification of Staphylococcus aureus infections in hospital environment: electronic nose based approach Ritaban Dutta a, ∗ , David Morgan b , Nicky Baker b , Julian W. Gardner a , Evor L. Hines a a School of Engineering, University of Warwick, Coventry CV47AL, UK b Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B95SS, UK Received 5 September 2004; received in revised form 5 January 2005; accepted 6 January 2005 Available online 17 February 2005 Abstract An electronic nose (e-nose), the Cyrano Sciences’ Cyranose 320 (C-320), comprising an array of 32 polymer carbon black composite sensors has been used to identify two species of Staphylococcus aureus bacteria, namely methicillin-resistant S. aureus (MRSA) and methicillin- susceptible S. aureus (MSSA) responsible for ear nose and throat (ENT) infections when present in standard agar solution in the hospital environment. C-320 e-nose has also been used to identify coagulase-negative staphylococci (C-NS) in the hospital environment. Swab samples were collected from the infected areas of the ENT patients’ ear, nose and throat regions. Gathered data were a very complex mixture of different chemical compounds. An innovative object-oriented data clustering approach was investigated for these groups of S.aureus data by combining the principal component analysis (PCA) based three-dimensional scatter plot, Fuzzy C Means (FCM) and self-organizing map (SOM) network. Using these three data clustering algorithms simultaneously better ‘classification’ of three bacteria subclasses were represented. Then three supervised classifiers, namely multi-layer perceptron (MLP), probabilistic neural network (PNN) and radial basis function network (RBF), were used to classify the three classes. A comparative evaluation of the classifiers was conducted for this application. The best results suggest that we are able to identify three bacteria subclasses with up to 99.69% accuracy with the application of the RBF network along with C-320. This type of bacteria data analysis and feature extraction is very difficult. But we can conclude that this preliminary study proves that e-nose based approach can provide very strong solution for identifying S. aureus infections in hospital environment and early detection. © 2005 Elsevier B.V. All rights reserved. Keywords: Electronic nose (e-nose); Cyrano Sciences’ Cyranose 320 (C-320); Staphylococcus aureus; Methicillin-resistant S. aureus (MRSA); Methicillin- susceptible S. aureus (MSSA); Coagulase-negative staphylococci (C-NS); Principal component analysis (PCA); Fuzzy C Means (FCM); Self-organizing map (SOM); Multi-layer perceptron (MLP); Probabilistic neural network (PNN); Radial basis function network (RBF) 1. Bacterial subclasses for this study Methicillin-resistant Staphylococcus aureus (MRSA) are a subgroup within a group of organisms known as S.aureus. MRSA are characterized by their resistance to treatment with commonly used antibiotics, in contrast to the remainder of the Staphyloccocus aureus group which are referred to as methicillin-susceptible S. aureus (MSSA). Both MRSA and MSSA can cause infection but individuals may also carry the organism without being infected by it. An individual, ∗ Corresponding author. Tel.: +44 2476 575952; fax: +44 2476 418922. E-mail addresses: dwmorganfrcs@btopenworld.com (D. Morgan), r.dutta@warwick.ac.uk, ritaban.dutta@warwick.ac.uk (R. Dutta). who carries the organism, but is not infected, is said to be a ‘carrier’ or ‘colonized’. At any one time up to 33% of healthy individuals carry Staphyloccocus aureus, including MRSA, predominantly in their noses and also at other sites (Fig. 1). Staphyloccocus aureus can give rise to infections varying from mild, e.g. boils and infected cuts, to severe, e.g. infec- tions of bones, lungs, heart and blood stream. The difficulty in treating MRSA with antibiotics has led to concern about this particular group of staphylococcal infections. All strains of Staphyloccocus aureus, including MSSA and MRSA, are capable of causing hospital-acquired infection. Organisms can be passed to patients from contact with hands or directly from the environment. The latter includes 0925-4005/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2005.01.013