1) Assume that you are viewing a Gram stained sample of vaginal discharge. Large (10 μm) nucleated red cells are coated with small (0.5 μm wide by 1.5 μm long) blue cells on their surfaces. What is the most likely explanation for the red and blue cells?
2) Clostridium botulinum is a strict anaerobe; that is, it is killed by the molecular oxygen (O2) present in the air. Humans can die of botulism from eating foods in which C. botulinum is growing. How does this bacterium survive on plants picked for human consumption? Why are home-canned foods most often the source of botulism?
- Gram-Stained Sample Interpretation
The presence of large (10 μm) nucleated red cells coated with small (0.5 μm wide by 1.5 μm long) blue cells on their surfaces likely indicates the presence of Vaginal Trichomoniasis. The large red cells are likely to be human erythrocytes, and the small blue cells are indicative of Trichomonas vaginalis, a protozoan parasite. T. vaginalis often appears as a small, motile organism in vaginal discharge samples, and in some cases, it can be seen adhering to the surface of epithelial cells or red blood cells. The blue staining of these cells is due to the Gram stain, where the protozoa can appear as small, blue-stained entities.
- Clostridium botulinum and Survival in Foods
Clostridium botulinum is a strict anaerobe, meaning it thrives in environments without oxygen. It can survive in foods, especially in conditions where oxygen is absent or minimal. Here’s how it survives and why home-canned foods are often the source of botulism:
- Survival in Foods: C. botulinum forms spores that are highly resistant to environmental stresses, including heat and desiccation. These spores can survive on plants and in soil. When foods are processed or preserved, such as through canning, the spores may remain viable if the processing is not thorough enough to kill them. The spores can then germinate and produce toxins in the anaerobic conditions inside the sealed containers.
- Home-Canned Foods: Home-canned foods are often the source of botulism because they might not be processed under conditions that are adequate to destroy C. botulinum spores. Home canning often lacks the precise temperature control and pressure required to effectively kill the spores. The ideal conditions for C. botulinum growth (anaerobic and low-acid environments) are present in improperly processed home-canned foods, making them a common source of botulism. Properly pressure-canning at high temperatures is crucial to eliminate these spores and prevent botulism.