Microbiology
- Name two quality-control methods/indicators used to determine if something has been autoclaved properly. (Hint: Watch the video on Central Processing)
There is the use of the color change method. Use a biological indicator control and test, place them in the autoclave, sterilize and incubate, and then observe what happens if the control changes color towards yellow, the autoclave is working, the biological indicator test should retain its color which shows sterilization is successful. If the test changes color to or towards yellow, then sterilization has failed.
Second, you can use soil on cloth as control then autoclave it. Grow the soil in a medium; if it gives growth, then autoclave is not working properly. If it does not give growth, then autoclave is working.
- A simple example of controlling microbial growth is based on how we handle our food products. Name three food preparation methods that counter microbial growth. Be sure to discuss the mode of action for each method.
Boiling is effective in controlling microbial growth. Boiling ensures all the microorganisms are killed. One should note that some microbes can survive in boiling, so boiling for a longer duration is encouraged to kill organisms.
Refrigeration and freezing. Low temperatures are effective in ensuring the slow growth of microorganisms and inhibiting microorganism metabolism. Freezing kills microorganisms and slowers the rate of microbial growth.
Drying. Food is stored through drying, which controls microbial growth because there is no water, and most microbes rely on water for growth.
- What are some factors that alter the effectiveness of a disinfectant
Physical and chemical factors; temperature, relative humidity, and water hardness.
Organic and inorganic matter, duration of exposure, and biofilms (Ledwoch, & Maillard, 2019).
- Infections among hospitalized patients are often related to the presence of a medical device in the patient. Which conditions favor the formation of biofilms on indwelling catheters and prostheses?
The conditions that favor the formation of biofilms on- dwelling catheters and prostheses include; cellular recognition of specific and non-specific attachments sites on a surface, nutritional cues, and planktonic cells’ exposure to a sub-inhibitory concentration of antibiotics (Sen, & Yadav, 2019).
- Why are some obligate anaerobes able to grow in tissues (e.g., gum pockets) that are not completely free of oxygen?
Because they cannot ferment or respire anaerobically.
- What is the role of Bacteroides in the human gut, and what are the effects of antibiotic use on them?
It leads to the production of volatile fatty acids that are reabsorbed into the body by large intestines and utilized by the host as an energy source. The effects of antibiotics use on them include; reduction of microbial diversity in the gut, it leads to pathogens that were earlier fought by Bacteroides to colonize the gut and reduce the body immunity, and the protective species in the gut drastically reduce ( Bhidé, Datar, & Stebbins, 2019).
- When scientists first proposed that Helicobacter pylori might be associated with stomach ulcers, other scientists were very skeptical of their conclusions. One of the researchers eventually consumed a sample and documented the effects, dramatically showing that the bacterium could cause gastrointestinal symptoms. Why do you think scientists were initially skeptical that a bacterium, rather than stress and lifestyle factors, could be responsible for gastritis, ulcers, and stomach cancer?
Initially, it was challenging to detect ulcers, therefore, making it difficult to prove the link between the bacterium and ulcers. With the lack of germ infection link to ulcers and the other diseases, studies resulted in the study of psychic and the environment, and stress and smoking were assigned as the causes of ulcers (Golombos, Ayangbesan, O’Malley, Lewicki, Barlow, Barbieri, & Scherr, 2018). This, therefore, made scientists to greatly reject the bacterial theory as a causative agent of ulcers, stomach cancer, and gastritis.
- What is a biofilm, and how is it different from a regular colony of bacteria? Name ONE type of HAI that can be caused by biofilms.
Biofilm refers to the accumulation of microorganisms of mono-or polymicrobial aggregates on surfaces, urethra catheters, among others (Rumbaugh, & Sauer, 2020). There are different from the regular colony of bacteria because planktonic cells are single- cells that may either float or swim in a liquid medium. The regular type of HAI caused by biofilms is urinary tract infections.
- A 65-year-old woman has been hospitalized for 3 weeks for chronic obstructive pulmonary disease (COPD) when she develops lung pain and exacerbation of her shortness of breath. A CT scan shows a clouded region, indicating a mass in the left lung. Broad-spectrum antibacterial agents fail to resolve the infection. Which organism is a probable cause? What is the treatment?
The cause was bacteria, and the treatment could be done by using narrow-spectrum antibacterial agents.
- In 2001, endospores of Bacillus anthracis, the causative agent of anthrax, were sent to government officials and news agencies via the mail? In response, the US Postal Service began to irradiate mail with UV light. Was this an effective strategy? Explain
Obsoletely an effective strategy because Bacillus anthracis, when inhaled, may make people sick. Mail irradiation kills any germs because of the heat, which then ensures the spread of anthrax is contained.
What are some possible reasons why intravenous chemotherapy failed to completely cure the patient despite laboratory tests showing the bacterial strain was susceptible to the prescribed antibiotic?
There is a high possibility of the area around the infection where the catheter was acted as a medium of the bacteria to develop. It led to biofilm formation in the area of infection. The surfaces of the catheter can become coated with host matrix proteins. The bacteria express numerous surface proteins that can bind with the host matrix proteins.
Why might the second round of antibiotic therapy have been more successful?
Because no catheter infection medium could allow the formation of biofilm by the bacteria; hence the oral antibiotics were successful.
Justify your answers.
The intravenous chemotherapy failed because the bacteria formed a biofilm, which was hard to treat. The intravascular catheter points were coated with host matrix proteins, which then become difficult to treat. In the second round, it was successful because the catheter was removed, and the bacteria had no hiding place or place to thrive.
- What items and/or surfaces in the kiosk were probably sampled, and why were they selected for sampling?
The alcohol-based hand sanitizer bottle, antiseptic bottle, kiosk counter, the manual tool used for piercing ears, and the earing studs in the kiosk.
- The kiosk workers claimed they couldn’t have transferred the pathogen from their hands to the customers because they wore gloves. Is this a valid conclusion? What are other ways P. aeruginosa could have been transferred to the customers during their piercing experience?
No, it is not a valid reason. The gloves worn by the workers could have caused carried the pathogen if they came into contact with tools that were contaminated; therefore, they become a pathogen carrier.
- Initially, Elise was concerned that the causative agent could have been Staphylococcus aureus, a Gram-positive bacterium, or aeruginosa, a Gram-negative bacterium; both are common culprits in piercing infections. What culture methods would allow for isolation and differentiation of these two bacteria? Would an anaerobic culture condition be needed? Be sure to explain your reasoning for all answers.
The use of a solid culture medium was necessary to distinguish them. Staphylococcus aureus should be streak in onto mannitol salt agar if under aerobic conditions it will incubate. P. aeruginous should be streak into eosin methylene blue agar; it will incubate under aerobic conditions (Momin, Bean, Hendriksen, Haenni, Phee, & Wareham, 2017).
- What role (if any) could the antiseptic have played in pathogen transmission?
The antiseptic could have been a tool of pathogen transmission if it was contaminated.
- Which tier would the piercing tool be classified for decontamination purposes? What precautions/protocols would the health authorities likely have recommended to limit future infections from piercings at the kiosk?
Top tier because it is the one that directly gets into contact with the ears of the patients. The piercing tool should be treated with great care and be highly disinfected every moment; a very strong, effective disinfectant should be used.
- What is the most likely explanation for why the girl who had her lower earlobe pierced six months ago did not develop a P. aeruginosa infection?
There is a high probability that P. aeruginosa contamination occurred between the six months. Earlier, there was no contamination, so the girl could not develop the infection.
References
Bhidé, A., Datar, S., & Stebbins, K. (2019). Case Histories of Significant Medical Advances: Eradicating Helicobacter Pylori Infections to Treat Ulcers. Harvard Business School Accounting & Management Unit Working Paper, (20-006).
Golombos, D. M., Ayangbesan, A., O’Malley, P., Lewicki, P., Barlow, L., Barbieri, C. E., … & Scherr, D. S. (2018). The role of gut microbiome in the pathogenesis of prostate cancer: a prospective, pilot study. Urology, 111, 122-128.
Ledwoch, K., & Maillard, J. Y. (2019). Candida auris dry surface biofilm (DSB) for disinfectant efficacy testing. Materials, 12(1), 18.
Momin, M. H. F. A., Bean, D. C., Hendriksen, R. S., Haenni, M., Phee, L. M., & Wareham, D. W. (2017). CHROMagar COL-APSE: a selective bacterial culture medium for the isolation and differentiation of colistin-resistant Gram-negative pathogens. Journal of Medical Microbiology, 66(11), 1554-1561.
Rumbaugh, K. P., & Sauer, K. (2020). Biofilm dispersion. Nature Reviews Microbiology, 1-16.
Sen, M., & Yadav, P. (2019). Modern Methods in Microscopy for the Assessment of Biofilms. In Biofilms in Human Diseases: Treatment and Control (pp. 59-69). Springer, Cham.