BIO 171 Microbiology Module 5. Portage Learning

BIO 171 Microbiology Module 5. Portage Learning.Module 5.1: Human Pathogens - Assessing Unknown Pathogens • When an unknown biological sample arrives in the lab for assessment and further characterization, the lab must take universal precautions. This means all handlers must treat all samples, known or unknown, as potentially hazardous (or pathogenic) materials. Thus, the appropriate personal protective equipment (PPE) should always be used. During the process of analyzing a microbial sample, a lab researcher would be certain to note: - (1) the morphological characteristics (size and shape) and - (2) the presence of any observable motility when viewed under a microscope • Then, if possible, they should capture images of any of the characteristics described above or at the very least manually draw the aforementioned observations. • Once differential testing has concluded, the technician should also document: - (1) whether the organism was Gram-positive or Gram-negative, - (2) the presence of any chemical reactions such as gas production (bubbling), fermentation, etc. - (3) any distinct changes in color localized to the organism itself or its surrounding media (e.g. Staph aureus on MSA agar). - 5 Steps to Infection • Infection occurs when a pathogen gains access to the body’s tissues disrupting their normal physiology. There are 5 steps of the infection process: 1 Tuesday, September 14, 2021 - Entry: Pathogens use portals of entry, mucus membranes or parenteral entry, to gain access to host tissues. - Attachment: The pathogen attaches and binds to specific tissue surues by using its adhesin factors. - Invasion: The pathogen invades deeper into the host’s tissues and secures nutrients for growth and multiplication. - Evasion: To successfully multiply, the pathogen must evade immune system defenses. Pathogens can • a) “hide” from immune cells by entering the host’s cells (intracellular pathogen), masking its antigens, producing surface molecules similar to the host’s (antigen mimicry), or changing its antigens over time (antigen variation) • b) undermine the host’s immune response by avoiding phagocytosis or causing immune suppression. 2 Tuesday, September 14, 2021 - Exit and transmission: Pathogens use a portal of exit to leave the host and be transmitted to a new host. Modes of transmission can be direct or indirect (Figure 5.1). Depending on the mode of transmission, transmission precautions should be followed in addition to standard precautions (Figure 5.2)