25th Lecture: 19/12/14

Topic: Microbial control method (part 2) and Antimicrobial Chemotherapy

Notes:
1) There are three types of physical control method which are heat, filtration and radiation.
2) Thermal Death point is the lowest temperature at which all cells in a culture are killed in 10min.
3) Thermal Death time is the time to kill all cells in a culture.
4) Decimal Duration time is the time in minutes to kill 90% cells at a given temperature.
5) Moist heat able to destroy viruses, fungi and bacteria in autoclave steam. The approximate conditions for moist heat killing is 15 minutes at 121 degree celcius in 5 psi. Moist heat will not destroys spores and does not sterilize.
6) Steam sterilization must be carried out above 100 degree celcius which requires saturated steam under pressure. This method carry out in aotuclave and it is more effective compare to moist heat because it can destroys all types of microorganisms including spores.
7) Pasteurization reduces spoilage organisms and pathogens but not all microbes in the medium.
8) Dry heat sterilization kills by oxidation and it it less effective than moist heat sterilization.
9) Filtration is used to reduce microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms.
10) Radiation is oftenly used for sterilization and pasteurization of plastic disposable supplie, food, antibiotics and hormone because radiation damages DNA. The ionizing radiation include X rays, gamma rays, electron beams. Non--ionizing radiation include UV.
11) Wavelength of 260 is most bactericidal because it can causes thymine dimers preventing replication and transcription.
12) UV limited to surface sterilization because it does not penetrate glass, dirt, films and other substances but gamma radiation penetrates deep into objects.
13) There are three types of chemical control methods which are disinfection, antisepsis and sterilization.
14) Principles of effective disinfection are concentration of disinfectant, organic matter, pH and ime.
15) Overuse of antiseptics such as triclosan has selected for triclosan resistant bacteria and possibly antibiotic resistant.
16) We can evaluating a disinfectant by using:

• Use-dilution test - Metal ring dipped in test bacteria are dried. Dried cultures are places in disinfectant for 10 min at 20 degree celcius. Rings are transferred tp culture media to determine whether bacteria survived treatment.
• Disk-dilution test - The wider of the inhibition zone, the lesser the bacteria able to resist to the disinfectant.

17) The types of disinfectant:

• Phenol
• Iodine
• Chlorine
• Alcohol
• Heavy metal - Zn, Cu, Hg
• Surfactants - soap, cationic detergents
• Chemical food preservatives
• Aldehydes

18) Microbes that have the most resistance to disinfectant is prions and the have the least resistance to disinfectant is viruses with lipid envelopes.
19) Biological control of microorganisms involve other organisms and their metabolites to control the growth of microbes. For example, viral mediated lysis using pathogen.
20) Chemotherapeutic agents are chemical agents that used to treat pathogens. Most of the chemotherapeutic agents are antibiotics.
21) Paul Ehrlich deeveloped the concept of selective toxicity at 1904.
22) Penicillin is the first discovered by Ernest Duchesne, but discovery lost and accidentiallt discovered by Alexander Fleming.
23) Selective toxicity is the ability of drug to kill pathogen while damaging the host as little as possible.
24) Therapeutic dose is the drug level required for clinical treatment.
25) Toxic dose is the toxic level at which drug becomes too toxic for patient.
26) Therapeutic index is the ratio of toxic dose to therapeutic dose.
27) The effectiveness of antimicrobial drugs expressed in two ways:

• Minimal inhibitory concentration - lowest concentration of drugs that inhibits the growth of pathogen
• Maximum inhibitory concentration - lowest concentration of drugs that kills pathogen

28) The level of antimicrobial activity can be determined by dilution susceptibility tests for MIC, Kirby Bauer and E-test MIC.

29) Dilution susceptibility test involves inoculating media containing different concentration of drug.

30) Kirby-Bauer Method standardized method for carrying out disk diffusion test where the sensitivity and resistance determined using tables that relate zone diameter to degree of microbial resistance.

31) E test similar to disk diffusion method, but uses strip rather than disk.

32) Inhibitor of cell wall synthesis includes penicillin ,cephaloporin, vancomycin and teicoplanin.

33) Protein synthesis inhibitors includes aminoglycoside antibiotic, tetracyclines, macrolides, chloraphenicol.

34) Inhibitor of nucleic acid includes quinolones.

35) Antifungal drugs easier to treat superficial mycoses than systemic infections.

36) Antiviral drugs is developed slowly because it is difficult to specifically target viral replication.

37) Anti-HIV drugs includes reverse transcriptase inhibitors, protease inhibitor and fusion inhibitors.

38) Tamiflu is an anti-influenza agent which has been shown to shorten course of illness.

39) Drug resistant 'superbug' means bacteria that have developed resistance to vancomycin such as Stapylococcus aureus.

Activity: Each group create quizzes of different topics.

My own Explorace:

1) We can use indicator to know whether the microbes are being sterilised in autoclave. There is a form of masking tape with white stripe on it. Put the tape on the water than only put into autoclave. After being sterilised, the tape will turn black which shows the microbes are fully sterilised. 

2) Buffer and antibiotic solution cannot sterilise using autoclave.

3) Toxic shock syndrome is a potentially fatal illness caused by a bacterial toxin. Different bacterial toxins may cause toxic shock syndrome, depending on the situation. The causative bacteria include Staphylococcus aureus.

4) Vancomycin is antibiotics that can treat most of the microbes but it will gives very bad effects to patient.

Reflection:

This is the last lecture of BMY 3101, my e-portfolio finally comes to the end. I admit I really struggling when doing e-portfolio because I almost spent hours for each lecture of e-portfolio. I refresh what I have learnt in class, explore more about the notes in Internet, look for the pictures and videos of the topic, able to memorise the microbes easily because I kept repeated the microbes' names when I did my e-portfolio. The benefit of e-portfolio are a lot. It it worth for me to struggle few hours a week for e-portfolio. I believe the efforts that I have done to my e-portfolio will later reflect out on my result. Again, thanks to Dr. Wan for teaching us this 14 weeks. What you have thought really make me feel more interested to microbes. Thank you so much!!!