Chapter 1 : Outbreaks and Cases Emphasizing Concepts in Basic Microbiology

Abstract:

This section talks about the outbreaks and cases emphasizing concepts in basic microbiology. The outbreaks and cases in this section have been chosen as examples of how basic microbial features enable pathogens to cause disease. Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has a waxy cell wall. In general, gram-negative cells are more resistant to antiseptics and disinfectants than are gram-positive bacteria because the outer membrane provides an additional barrier to diffusion. In addition, Pseudomonas aeruginosa, a common hospital-acquired gram-negative pathogen, has very small porins, which further restrict diffusion, allowing it to survive some chemical treatments that effectively kill other pathogens. Neisseria gonorrhoeae has adhesins at the ends of pili. These can attach to cells of the reproductive epithelium, leading to gonorrhea, a sexually transmitted disease (STD). In addition, influenza A virus can undergo antigenic shifts when it recombines with an influenza virus from birds or swine. These genetically unique viruses are able to cause worldwide epidemics, since no one is immune. Other pathogens, such as human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome (AIDS), and measles virus survive by overcoming host defenses. Various strains of Staphylococcus aureus and Streptococcus pyogenes produce a host of tissue-damaging enzymes: hemolysin, leukocidin, hyaluronidase, coagulase, streptokinase, and collagenase. The understanding of the general microbiology concepts has led to the development of new drugs and vaccines and changes in the way we treat and prevent the spread of certain microbes.