Microbiology and Infectious Disease
Core concepts
Understand the structure and classification of bacteria, viruses, fungi, and parasites, including the difference between gram-positive and gram-negative cell walls, the role of capsules and pili, and the nature of viral replication. Know the chain of infection, modes of transmission, portals of entry, and the principles of asepsis and sterilization. Be able to distinguish colonization from infection, and understand antibiotic mechanisms and the basis of resistance.
Traps
A frequent error is treating viruses as susceptible to antibiotics; antibiotics target bacterial structures such as cell walls, ribosomes, or DNA gyrase, which viruses lack. Another trap is confusing sterilization with disinfection: sterilization kills all microorganisms including spores, while disinfection reduces pathogens on inanimate surfaces. Questions may also test whether a disease is spread by droplets, airborne particles, or vectors; know that airborne precautions require N95 respirators and negative-pressure rooms.
Worked example
A patient with suspected pulmonary tuberculosis requires airborne precautions. Rule of thumb: if the pathogen can remain infectious in small particles over long distances, use airborne precautions; if it spreads by large droplets, use droplet precautions.
Study tip
For each organism, learn one virulence factor, one transmission route, and one prevention measure; exam items usually hinge on one of these three.