MICRO LAB Week 7: Control of Microbial Growth

It seems that the new infection has a different form of the transpeptidase enzyme that penicillin can't buy into what is one other way suggested by the theory by which a previously sensitive bacterial strain can become resistant to penicillin?

Bacteria can express an enzyme capable of inactivating penicillin before it can bind to transpeptidase

Is there anything else that might help them?

Chlorhexidine is an effective anti-septic at the right concentration, maybe they could try this as a mouthwash?

Too bad, it doesn't look like that drug worked tetracycline. Even if resistance was not an issue, antimicrobials would only have a discrete range of bacteria that they can exert their effects on. Why do you think this is?

Microbial components very over different species and strains. If the organism naturally doesn't express the target component, the drug will be able to exert an effect on it.

According to the theory how does penicillin kill bacteria?

Penicillin targets a cross linking reaction and so will manufacture by blocking the enzyme responsible, penicillin stops the bacteria from producing new peptidoglycan.

Why do you think penicillin has failed to destroy the bacteria we have culture from the patient sample?

Perhaps a few cells from the old infection developed resistance so weren't cleared by the previous treatment. They could've gone on to develop the second abscess.

Based on your explorations and theory reading in the lab today? Which sterilization method do you think would be best for these items?

Steam and high pressure will kill everything, let's use the auto clave

Based on your exploration and the theory, what do you think the difference is between decontamination and sterilization?

Sterilization is a type of decontamination, but not all decontamination techniques result in true sterilization.

What do we highlight when we talk about antimicrobial resistance?

The ability of a microbial stain to withstand the effects of a previously effective anti-microbial agent

When we say an antimicrobial agent exhibits selective toxicity, what do we mean?

The agent is only toxic to microbial cells because it targets a cell component only found in microbes and not present in the host organism

Why do we need a positive control in this experiment?

The hypochorite is known to cause inhibition, so shows inhibition can occur in the current experiment and what it looks like, this is the positive control.

On this plate the penicillin desk is at the top of the plate, with the positive control below on the left and the negative control the low on the right. What tentative interpretation can you make from what you observe?

The penicillin has failed to make a zone despite the positive control success. The bacteria may be resistant to penicillin.

How does wet heat sterilization, such as an autoclave, work to inactivate bacteria and other infectious pathogens?

The sustained heat and pressure denatures proteins, without protein nothing can replicate or remain infectious.

How did you get on with the tools? How did you process them?

We cleaned them with biological detergent then rinsed and dried everything before autoclaving

Did you learn anything about bacteria causing the infection?

We conducted a diffusion disc assay the new infection was not inhibited by penicillin challenge. Maybe the new infection is penicillin resistant

Now that you've explored the lab and found what you've got on hand to work with, what do you think the first step should be for decontaminating these tools?

We should remove loose soil and debris by washing using a biological detergent

The drug you added seemed to prevent cell growth much quicker, but the cells didn't burst like before. According to the theory, why do you think clindamycin and metronidazole Produce a different effect to penicillin?

metronidazole targets the DNA of microbial cells and clindamycin targets the ribosome, neither of which create a lytic effect like penicillin