Difference between revisions of "Team:Sheffield/Human Practices"

The Global Antimicrobial Resistance Issue

When choosing an issue to tackle with our diagnostic hardware, we decided to focus on the growing issue of antimicrobial resistance (AMR). AMR infections are thought to claim as many as 700,000 lives per year, a figure that is expected to rise to 10 million by 2050 if current trends continue (Figure 1) (1). The World Health Organisation (WHO) has therefore described AMR as one of the major concerns of modern healthcare (2), and it is critical that we take action now.

The use of antibiotics is the leading cause of antimicrobial resistance around the world, and in 50% of cases, antibiotic treatment is either not needed or not optimally effective for the infection (3). Doses of antibiotic that are not lethal to bacteria leads to the development of antibiotic resistance by supporting genetic change and acting as a selection pressure (4) (Figure 2). Therefore, one way clinicians can combat AMR is to conduct antimicrobial susceptibility tests (ASTs), to identify any drug resistance in pathogens and ensure effective drugs are chosen for treatments (5).

Advice from Microbiologist Consultants

To gain a better understanding of what ASTs are most commonly used in the clinic, we spoke to microbiologist consultants in Poland and Cyprus. They informed us of the Vitek 2 System, that is commonly used for ASTs.

Vitek2 is a highly automated system, in which a bacterial suspension, grown from a patient sample, is distributed into compact cards containing antibiotics (figure 3). A sensitive optical density system then measures changes in bacterial growth in the presence of the antibiotics in the cards. If there is no bacterial growth, then the organism is sensitive to the drug and it would therefore be an appropriate treatment option.

However, the Vitek 2 system is hugely expensive, costing close to $100,000 (7). The clinicians in Poland and Cyprus expressed to us that this cost was the major drawback of Vitek 2, and means that often smaller hospitals and clinics are unable to afford this state of the art machinery, and therefore miss out on the ASTs that could be crucial to prevent the spread of AMR.

Repurposing the BrightBiotics system as an affordable, automated AST device

Following our research on the Vitek 2 system, we noticed that our device could have many of the same features. It detects bacterial growth as a measure of optical density, and so may therefore detect changes in growth at rates similar to Vitek 2. In addition, we could emulate the Vitek 2 cards by putting antibiotics in the well plate, and seeing how various antibiotics affect growth of a bacterial inoculum.

Firstly, we made sure we could detect differences in growth of antibiotic resistant and sensitive strains in the presence of the appropriate antibiotic, as Vitek 2 can. We engineered antibiotic resistant strains by transforming with biobricks encoding chloramphenicol, kanamycin, carbenicillin and ampicillin resistance. Then used a laboratory automated plate reader to compare their growth with that of of antibiotic sensitive strains, in the presence of antibiotics. We found that with the laboratory plate reader we could see a difference within just a few hours at bacterial concentrations as low as 10^3 CFU/ml (equivalent to 1x10-3 OD) (figure 4). This showed us that it would be possible to differentiate between antibiotic sensitive and insensitive strains, in a time frame that could be clinically relevant.

Next, we confirmed that our device could also differentiate between antibiotic resistant and sensitive strains. …. NEW GROWTH CURVE

medicine

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teaching

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