Que Pasa People,
I want to talk again on some course-specific materials this week, in particular that of the Medical Microbiology module. A number of modules in the HESAS department share this module – Medical Sciences, Human Biology, Biology and Forensic Biology, all on the Glyntaff Campus.
In this module we cover all things from pathogenesis of bacteria to the transmission of such pathogens, but also individual bacterial species such as Measles (helps with the recent outbreak) and ‘Clostridium Difficile’. These lectures are accompanied by a number of small classroom tests, as well as two written assignments based on research papers/current topics/course content; then there are the practicals. All of these add up to a total module mark of 50% (the other 50% coming from the exam).
There are two practical pieces that take place over the course of the year each taking a number of weeks to complete due to the nature of inoculating samples, culturing them and carrying out further tests and cultures. I want to talk about the one I found particularly interesting this year and that was the bacterial examination of water samples.
For this experiment we worked in groups of two and each group took a small amount of two different samples: pure tap water and either water that had been inoculated with a strain of E. Coli or a sample of water from the local river. Everyone was eager to get their mits on the local river sample so some of us had to choose the already “infected” water.
The aim of this experiment was to detect, using various presumptive and confirmatory tests, whether samples of drinking water have been contaminated with sewage or faecal materials, from either a human or animal origin.
In particular we were looking at bacteria present in the human digestive system, known collectively as the coliforms – the genera we were testing for were members of the enterobacteriacae family (E. Coli, Shigella, Enterobacter, Klebsiella). These crafty little blighters have the ability to utilise lactose within the digestive tract as a source of carbon and carry on surviving where many other bacteria can’t.
Anyway, we inoculated some tubes with a type of lactose broth and our water samples which acted as a presumptive test for these crafty coliforms to see if any were actually present in the next session. These were incubated and left to grow and develop. If coliforms were present then acid and gas would be produced by these bacteria, affecting the colour and composition of the tubes.
A week later we came back and used any positive results for coliforms for the next piece – a confirmatory test for the coliforms; also checking for the presence of faecal streptococci (common in the human intestine) – this type of streptococci in water indicates faecal pollution.
The tap water samples were negative – no coliforms present, thank God – carry on drinking it you’re fine. The positive water samples were then cultured further for some indicative tests on the types of coliform present in the later weeks.
We also streaked some of the samples on to a specialised agar plate to test for any faecal streptococci. If present, this would present itself on the agar plate as a black/brown colouration of the agar, and smell foul. Just to warn you, the local river sample that we all had came up positive (probably from animals like rats!), so go careful where you choose to take a splash on warm summers day or take a drink, if at all haha! Not all rivers appear to be as fresh as they look!!
This really opened my eyes as to how much pollution (in the non-chemical side of things) actually goes on! It was a long-winded process with culturing so many different samples but well worth it in the end and strangely fun to do.
Until next time, remember, there may be something in the water.