medicale microbiolojy

Medical bacteriology

The study of bacteria that cause human disease. The field encompasses the detection and identification of bacterial pathogens, determination of the sensitivity and mechanisms of resistance of bacteria to antibiotics, the mechanisms of virulence, and some aspects of immunity to infection.
See Virulence The clinical bacteriology laboratory identifies bacterial pathogens present in specimens such as sputum, pus, blood, and spinal fluid, or from swabs of skin, throat, rectal, or urogenital surfaces. Identification involves direct staining and microscopic examination of these materials, and isolation of bacteria present in the material by growth in appropriate media. The laboratory must differentiate bacterial pathogens from harmless bacteria that colonize humans. Species and virulent strains of bacteria can be identified on the basis of growth properties, metabolic and biochemical tests, and reactivity with specific antibodies.
Recent advances in the field of diagnostic bacteriology have involved automation of biochemical testing; the development of rapid antibody-based detection methods, and the application of molecular biology techniques.
Once a bacterial pathogen has been identified, a major responsibility of the diagnostic bacteriology laboratory is the determination of the sensitivity of the pathogen to antibiotics. This involves observation of the growth of the bacteria in the presence of various concentrations of antibiotics. The process has been made more efficient by the development of automated instrumentation. An increasingly serious problem in the therapy of infectious diseases is the emergence of antibiotic-resistant strains of bacteria. An important area of research is the mechanisms of acquisition of antibiotic resistance and the application of this knowledge to the development of more effective antibiotics.
Beneficial Bacteria

Most bacteria do not directly influence humans. However, a small number of bacterial species can cause human or animal diseases and are a major focus of scientific study. Other bacteria can be beneficial to humans by contributing to human nutrition and protecting the body from pathogens. The E. coli bacteria in our colons are an example. Bacterial cells such as E. coli are widely used in laboratories as factories to produce commercially or medically important proteins through the use of genetic engineering or recombinant DNA technologies. Other bacteria are important for agriculture since they take nitrogen from the air and replace it in the soil (nitrogen fixation). Bacteria are used to clean up oil spills and toxic chemicals in the environment. There are as many beneficial bacteria as there are destructive germs .

Structure.
The bacteria are approximately ten times the size of viruses, ranging from 0.4 um to 2.0 um in size. They assume one of three morphological forms, spheres cocci, rods ,bacilli or spirals although there is much variation in each group. The morphology of a bacterium is maintained by a rigid cell wall and it is the nature of this cell wall that allows us to divide bacteria into two basic groups, Gram-positive bacteria and Gram-negative bacteria .