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. 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. Bacterial physiology and metabolism
The study of bacterial pathogenesis involves the fields of molecular genetics, biochemistry, cell biology, and immunology. In cases where the disease is not serious and easily treated, research may involve the deliberate infection of human volunteers. Otherwise, various models of human disease must be utilized. These involve experimental infection of animals and the use of tissue cell culture systems. Modern molecular approaches to the study of bacterial pathogenesis frequently involve the specific mutation or elimination of a bacterial gene thought to encode a virulence property, followed by observation of the mutant bacteria in a model system of human disease. In this way, relative contributions of specific bacterial traits to different stages of the disease process can be determined. This knowledge permits the design of effective strategies for intervention that will prevent or cure the disease. Bacterial genetics
The presence of specific antibodies is frequently useful in the diagnosis of bacterial diseases in which the pathogen is otherwise difficult to detect. An example is the sexually transmitted disease syphilis; the diagnosis must be confirmed by the demonstration of antibodies specific for T. pallidum.
Immunity to some bacteria that survive intracellularly is not mediated by antibodies but by immune effector cells, known as T cells, that activate infected cells to kill the bacteria that they contain. An active area of research is how bacterial components are presented to the immune system in a way that will induce effective cell-mediated immunity. This research may lead to the development of T-cell vaccines effective against intracellular bacterial pathogens.
For disease entities caused by specific bacteria Anthrax Botulism Brucellosis Cholera Diphtheria Glanders Gonorrhea Johne's disease Listeriosis Plague Tetanus Tuberculosis Tularemia . For disease entities caused by more than one microorganism Food poisoning Infant diarrhea Meningitis Pneumonia . For groups of disease-producing bacteria Medical bacteriology Pneumococcus Streptococcus