11 M•-S.:il, J.1 ..C F IGUR E 12 -5 . Bacterial cells showing resistance to antibiotics. CHAPTER 12 • Infectious Diseases Fungi Molds , andYeasts . ' b b c d f 1 orgamc mar - Fungi are organisms chat a sor roo ron ter. About 50 of the many thousands of fungi types_ cause . l d ' k' d ' se lung di sease , disease in humans , me u mg s 111 isea ' d ' and di seases in mucous membranes. Fungi , incl~ '.~g molds and yeasts, have a cellular structure ve~y s1m1 ar to a human cell, making them harder to recogmze by the M Id nd yeasts differ from human immune system. o s a fungi in their method of reproduction , a process cal~ed budding . Fungal spores are inhaled from soil or deca_rmg plants , or are tran s mitted from animals , bi rd droppmg_s, or ot her hum ans. Inh aled fungal spores cause pneumonia and lung infections , a nd are most prevalent in tropical regions. A fungus transmitted from a noth~r h~man can develop on the skin , nails, and hair , causmg rmgworm and athlete 's foot , both of which are easy to treat . Under certain conditions , yeasts normally found in the mouth and gut of humans can overgrow, often in response ro antibiotic treatment , causing thrush in the mouth or vaginal yeast infec tions . Although over - the-counter drug tr ea tments are available for vaginal ye ast infection s, the product may not be effective against che type of yeast chat has proliferated, possibly causing che infection to become more severe. Only a medical practition er can accurately diagnose che infection and prescribe the proper me dicati o n. Fungal infection s are particularl y harmful for chose with immune deficiency diseases, which make them more susceptible to opportunistic inf ectio ns. One fungu s, coccidioidomycosis, causes valley fever, a systemic disease that may be severe, even life threatening. IJ Though some may be ha rmful, ther e are benefi cial use s for yeasts and molds . One type of yeast converts sugars into carbon dioxide under aerobic conditions , allowing bread to ri se prior to baking . The same yeast und er anaerobic conditions allows s ugar to be converted to alcohol , th e basis for making alcoholic beverages. Yeasts are also u se d to help make vaccines, notably the hepatiti s B vaccine , as well as the first antibiotic drug penicillin , which was originally made from rhe mold J>enicill i um notatum . Protozoa Proto zo a are singl e-ce ll organisms ch at can live either exte rnally or int e rnally in humans . Musr ar e not harmful to humans , bur rhe frw path oge ni c protozoa arc diHicult for the immune sy stem to recognize and co mbar. Pound
~ I Infect ious Diseases • CHAPTER 12 http: //imageofhea Ith. haydenmcneil .com mostly in rhe trop ics , protozoa can be found in water and are tran smitted by insects. The mo st common in sec t- borne pathogeni c protozoa are Plasmodium, w hich infect and spread malaria to humans. Ther e are four types of Plasmod ium, and depending on the type , the se Plasmo- dium cause a variet y of illnesses , from flu-like sy mptom s and fever to brain and organ failure and death . The most common water - born e pathogenic
You've reached the end of your free preview.
Want to read all 25 pages?