MODULE 5 – PUBLIC HEALTH MICROBIOLOGY

This is the aspect of microbiology that deals with the identifying and characterizing microorganisms that directly affect the health and wellness of communities. The research they conduct is used to aid in the control and prevention of communicable diseases by making the environment safe.

MICROORGANISMS OF PUBLIC HEALTH IMPORTANCE

When only a few organisms are present on or in a tissue, an infection will not necessarily develop. However, when a critical number is exceeded, it is very likely that the tissue will become infected. For every type of microorganism, the minimal infective dose can be determined; this is the lowest number of bacteria, viruses, or fungi that cause the Þrst clinical signs of infection in a healthy individual. For most causative agents of nosocomial infections, the minimal infective dose is relatively high. For Klebsiella and Serratia spp. and other Enterobacteriaceae, for example, it is more than 100 000, but for hepatitis B virus it is less than 10.

Disease causing organisms (pathogens) can be classified into 4 groups – conventional pathogens, conditional pathogens, opportunistic pathogens and emerging pathogens.