Microbiology

Microbiology Study Guide

Local and Systemic Diseases When the infection or disease is originated and restricted to only one human organ or body area, it is said to be a localized disease. For instance, an ankle sprain or a boil on the hand are examples of localized diseases. In contrast, when the disease originates in one organ or body tissue but spreads to other areas on the body, tissue, or organ, it is referred to as systemic disease. Nosocomial Diseases Nosocomial diseases are infections acquired under medical care. The word nosocomial is popularly known as “hospital-acquired.” These infections are caused by antibiotic-resistant organisms during a patient’s hospital stay. The patient must be admitted to the hospital or health care facility for any reason other than a nosocomial infection. The major cause of nosocomial diarrhea is the bacterium Clostridium difficile . Another common staph bacterium, generally acquired at the hospital, is Methicillin-resistant Staphylococcus aureus . Symptoms include inflammation, discharge, fever, and abscesses. The treatment of the nosocomial disease depends on the type of infection. Establishment of Disease Transmission When the disease is confined to a defined population, the infection from the pathogens also remains intact within that population. This reservoir can be either living or non-living (soil, food, water, or air). When the reservoir of infection is humans and they continue to shed the organisms containing infections, they are known as carriers . If the reservoir of infections is animals and they shed and spread their infections among humans, it is termed as zoonoses . Diseases are transmitted from one organism to another through different modes, such as contact, vehicles, and vectors. Transmission from contact can either be direct or indirect. When the transmission happens through physical contact, like human touch or sexual intercourse, the transmission is said to occur directly. When physical contact is not direct and is invaded by a non- living object, the transmission is said to be indirect. The non-living agent or object is often known as fomite. Some instances of the lifeless object can be towels and utensils. Transmission is also possible through nuclei droplets, mucus, or saliva that travels between two or more human beings. Transmission through vectors is associated with spreading pathogens by living beings like flies, mosquitoes, and ticks, as they carry the infectious pathogens on their bodies. Such vectors are characterized as mechanical. When these arthropods are already infected and the infections are transmitted by them through their saliva or feces, the vectors are regarded as biological vectors. The third mode of transmission is vehicles that constitute lifeless things like soil, water, air or food. This mode of transmission may be contaminated by human feces, pathogens from soil, or infections that are transmitted through airborne droplets. For instance, water may contain human feces and can cause diarrhea, while droplet nuclei, being transmitted through air, is likely to cause tuberculosis and the common cold.

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