Day 1: Coffee Breaks and Culture Media

Minutes after finishing our last finals and saying goodbye to friends, we headed to the microbiology lab to celebrate the start of summer. Seven hours of lab sounded daunting, but going over the syllabus at a sunny picnic table was a great way to start. After getting coffee and a few cookies, we headed inside to begin.

Washing Effectiveness

Materials: agar plate, hands, soap and water, paper towels

Procedure: As we walked in the door, we poked the inside of a Petri dish with our unwashed fingers then lined up to wash our hands before re-touching what we learned to call an agar plate. These dishes are now incubating - bacterial growth results coming soon. Hygeine is essential for health professionals, so hopefully the 'after' fingerprints will grow less bacteria.

Next we went over lab safety rules (bunsen burners and hair don't play nicely together) and discussed the ways that bacteria usually found in vivo can be observed in vitro. This brought us to our first experiment...

Preparing Culture Media

Materials: dehydrated agar and beef extract, scale, weigh boats, spatula, distilled water, large flasks, sterilized test tubes, test tube rack, Petri plates (with covers), bunsen burner, autoclave

Procedure: after learning that bacteria can be grown in vitro via agar plates, broth, agar slant tubes, or agar deep tubes, we began preparing some broth and agar for future use. We mixed 1.6 grams of [dehydrated broth medium] with 200 mL of water in one large flask, and 4.6 grams of [agar medium] with 200 mL of water in another. Both flasks were then autoclaved for 20 minutes for sterilization.

Results: After letting the flasks cool, we poured the nutrient broth solution into sterile test tubes (10 mL in each). The agar solution was heated over a bunsen burner until it was viscous enough to pour into Petri dishes. Both the broth tubes and the agar plates can be used later to cultivate bacteria.

Autoclaving is a procedure we will be using as nurses to sterilize pieces of surgical, routine, and other medical equipment. To prevent the spread of any pathogens from one patient to another, all reusable instruments and contaminated objects that can withstand autoclave temperatures are steamed to inactivate all bacteria, viruses, and spores.  

Environmental Samples

While the agar and nutrient broth solutions were cooling, we took a fieldtrip to the cafeteria for our next experiment (materials: agar plates, nutrient broth, sterile swabs, cafeteria table). Procedure: We found an allegedly clean table and took a sample by dipping our sterile swab in nutrient broth, rubbing it on the table, and gently rubbing the swab on our agar plate. The sample was placed in an incubator so we can check for bacteria growth later.

At this point we had covered two weeks' worth of lab material over the course of a few hours and decided that a snack break was in order. Dr. P's sandwich might have gotten a few extra nutrients from some spilled broth...

As nurses we will become very familiar with the practice of swabbing. We won't necessarily be swabbing cafeteria tables, but throats will be right up our alley. Swabbing infected areas of the body to culture, analyze, and identify the bacteria in order to treat a patient's symptoms is common practice for nurses!

Aseptic Technique Practice

Materials: inoculating loop, bunsen burner, lighter, two sample test tubes with caps, test tube rack

Procedure: Back in the lab, we talked about the importance of transferring cultures without inadvertently contaminating anything. Because this is so crucial, we practiced our aseptic technique several times. This meant running an inoculating loop through a bunsen burner's flame so that its entire length became red-hot and therefore sterile, then uncapping a test tube (without setting the cap down) and running the mouth of the tube through the flame to sterilize it. After letting the inoculating loop cool a bit (which includes tapping it against the inside of the test tube), we dipped it into the liquid in the tube and pulled it out with a thin film of the sample. The first test tube was then sterilized in the flame and re-capped, and the second test tube was uncapped and sterilized so that the inoculating loop could be inserted. Finally, the second tube and inoculating loop were sterilized again and the cap was put back on the tube.

Results and conclusions: since these were just sample tubes there won't be any bacteria growth to show that our transfer was successful, but we know what we're doing now and can soon use this technique with bacteria samples.

Outside of the lab, "aseptic technique" refers to anything that removes or kills microorganisms, creates sterile instruments, or reduces a patient's risk of exposure to microorganisms. In a nursing situation this could refer to anything from washing your hands between patients to maintaining a sterile environment in the operating room. Especially with the recent Ebola epidemic, it's obvious how important maintaining proper aseptic technique in all situations is to everybody's health. We have to recognize that there are bacteria everywhere, and it is especially important to be careful around patients with fragile immune systems.