Antibiotics are an antimicrobial agent defined as “a chemical substance produced by a microorganism that kills or inhibits the growth of another microorganism” (1). Since the introduction of the first effective antimicrobial in 1937 (2), there has been persistent growth and spread of drug-resistant bacteria, broadly referred to as antimicrobial resistance (AMR). AMR is defined as the phenomenon where infection-causing microorganisms, such as bacteria, have the ability to survive exposure to medicine which would normally inhibit their growth or kill them (3). The health implications of AMR are extensive, affecting not only the treatment of a primary bacterial infection, but also the prophylactic use of antibiotics in routine surgical procedures, such as caesareans and hip replacements (3, 4). O’Neill (2016) estimates that, unchecked, the growth of AMR will result in 10 million preventable deaths per year by 2050. In addition to the human cost, the increase in AMR is associated with significant economic consequences (5). AMR is associated with increased expenditure on health services, with greater resource utilisation and higher levels of routine health care costs (6, 7, 8). The additional impact of AMR has downstream effects on health service productivity (9). Unfettered, it is estimated that by 2050, AMR will have impacted world global production by $US100 trillion (3).
From an evolutionary standpoint, AMR is unavoidable (10) due to bacteria’s inherent ability to survive, mutate and adapt, following stress and greater exposure to antimicrobials (4). Given that AMR cannot be reversed or eradicated (11), actions to slow and contain the development of resistance are imperative (12). The rate of AMR development is widely understood to be facilitated by indiscriminate and unnecessary antibiotic use (3, 13-16). The World Health Organisation (WHO) Global Strategy for Containment of Antimicrobial Resistance (2001) defines appropriate antimicrobial use as the “cost effective use of antimicrobials which maximises clinical therapeutic effect whilst minimising drug-related toxicity and development of antimicrobial resistance” (17).
Existing literature highlights consumer or patient demand and behaviour, as a driving force behind antibiotic misuse (18-20). Understanding the extent of global trends in consumer demand for, and knowledge about, antibiotics is therefore an important component in the battle to curtail the growth of AMR and has precipitated multinational surveys. For example, a survey carried out by the TNS Opinion and Social for the European Commission (2010) gathered information from 26,761 individuals across the (then) 27 member states of the European Union. The survey found that 40% of respondents had taken antibiotics in the previous 12 months, with 95% reporting that they (appropriately) obtained them from a medical practitioner. However, the survey also reported that only 20% of respondents were able to correctly answer four knowledge statements regarding antibiotics, including 53% who believed that antibiotics kill viruses, and 47% who believed antibiotics were effective against colds and influenza. These results suggest that while Europeans report obtaining antibiotics through appropriate means (doctors), their intended use is often inappropriate (21).
A subsequent survey conducted by the WHO (2015) questioned 9,772 individuals across two member states in the six WHO regions. In this survey it was found that 65% of respondents had used antibiotics in the previous 6 months, with 81% (range 56%-93%) indicating that they had obtained them from a medical professional. The WHO survey reported that 25% of respondents believed it acceptable to use antibiotics given to them by a friend or family member, 43% thought it acceptable to buy antibiotics or seek them from a doctor if they were sick with symptoms that they believed were effectively treated by antibiotics in the past, and 64% incorrectly believed viruses such as colds and influenza could be treated by antibiotics (15).
According to Wise et al., (1998), 20% of human antibiotic use occurs within the hospital sector, whilst 80% is within the community sector. Within this community portion, 20-50% may be questionable and unnecessary (22). Within Australia specifically, antibiotic consumption rate exceeds the Organisation for Economic Cooperation and Development (OECD) average (23). Thus, an understanding of the drivers of Australian consumer antibiotic seeking and use is warranted.
Both the TNS Opinion & Social (2010) and WHO (2015) surveys had numerous limitations, including various sampling techniques, bias toward more educated responders, and an absence of checks upon socially desirable responding. Furthermore, neither survey was theory informed in order to enable prediction of consumer antibiotic use, other than the potential impact of poor knowledge about antibiotics and AMR, and neither reported detailed psychometric properties of the questionnaires. They do, however, confirm previous research which has identified a range of key factors contributing to patient behaviour with respect to antibiotic use, including attitudes and beliefs, subjective norms, self-efficacy and knowledge (6, 24).
There are few measures which currently exist in this area. Many are specific to population sub-groups, including physicians, parents (6, 25-27), medical students (28) and pharmacists (29-30). To our knowledge, there exists no sufficiently validated measure which aims to investigate factors influencing antibiotic use within the general populace (31).
The current study sought to develop a questionnaire that predicts the factors influencing a consumer’s intentions to indiscriminately obtain and use antibiotics. Given that attitudes and beliefs (32), the opinions of others within a person’s social or professional network (33-35), and the self-perceived (and actual) ability to obtain antibiotics (36-38) have all been independently associated with the use of antibiotics, the current study aimed to construct a questionnaire informed by the Theory of Planned Behaviour (TpB) (39), a respected and highly cited model which predicts health related behaviours (40-43). The TpB, which has yet to be used in the context of antibiotic use for consumers, would suggest that a person’s actual use of antibiotics is best predicted by their intentions, which are influenced by three major components (see Figure 1): (a) attitudes, referring to one’s positive or negative evaluation of indiscriminate antibiotic use, (e.g. ‘the negatives of taking antibiotics outweigh the positives’); (b) subjective norm, involving their perception of the social expectations of indiscriminate antibiotic use, (e.g. ‘my friends and family would follow recommendations for antibiotic use’); and (c) perceived behavioural control (PBC), reflecting the beliefs regarding the ease or difficulty in accessing antibiotics, (e.g. ‘I would easily be able to get antibiotics if I wanted them’). PBC was the only control measure as actual behavioural control (added to later TpB models (44) was unable to be measured within this study protocol. A condition of the strength of this PBC-behaviour relationship is that ‘perceptions of behavioural control must reflect actual control in the situation with some degree of accuracy’. When perceptions of control are accurate, PBC is expected to predict behaviour (45-47).
One of the most extensive TpB reviews, focusing on prospective behaviours across 237 studies, was conducted by McEachan, Conner, Taylor and Lawton, (48), who found that the TpB could explain 19.3% of variance in behaviour and 44.3% of the variance in intention to behave. McEachan and colleagues further demonstrated that the TpB provides strong predictions of intention and behaviour across a range of health behaviours, with the attitude component being the strongest behavioural intention predictor. Further, Ajzen, (1991) suggests that the TpB is highly adaptive, possessing the ability to incorporate additional predictors where required, providing that they maintain the ability to capture a significant proportion of variance in intention or behaviour, and also given that the initial variables have been considered. Given previous research, knowledge about antimicrobials, and AMR specifically, would be expected to influence attitudes (32).
Limitations surrounding the TpB include its sole reliance upon self-reported behaviour, potentially inspiring socially desirable and less accurate predictions of objective behaviour (47). Armitage and Conner undertook a meta-analysis of 161 articles containing 185 independent empirical tests of the TpB, concluding that the use of the model is effective in predicting intention and behaviour, more so in the context of subjective self-reported behaviour over observed behaviour (R-squared 0.31 and 0.20 respective) (40). This is not a limitation specific to the TpB, but broadly to the area of social psychology, and is not a large cause for concern given the model still capably measures a good amount of variance in prospective measures of actual behaviour (40). Moreover, the TpB showcases high consistency between intention and behaviour, even in contexts of differing emotional states (47). None-the-less, attention to social desirability would enhance the predictive validity of the TpB as applied to consumer antibiotic use.
Thus, the aim of the current study is to develop and investigate the psychometric properties of an original, novel and multiple-item quantitative questionnaire, aiming to identify factors contributing to antibiotic use within the community, informed by the TpB. Considering the adaptive nature of the TpB (39), knowledge was added as a variable of interest within the current study, due to the array of literature which indicates a relationship between knowledge and antibiotic-use behaviour (31).