Laboratory Diagnosis, Prevention and Treatment of bacterial Infection Xiao-Kui guo
Laboratory Diagnosis, Prevention and Treatment of Bacterial Infection Xiao-Kui Guo
Manifestations of Infection: Signs and symptoms vary according to the site and severity of infection Diagnosis requires a composite of information, including history physical examination, radiographic findings, and laboratory data a Microbial Causes of Infection: Infections may be caused by bacteria, viruses, fungi, and parasites. The pathogen may be exogenous (acquired from environmental or animal sources or from other persons or endogenous (from the normal flora)
Manifestations of Infection: Signs and symptoms vary according to the site and severity of infection. Diagnosis requires a composite of information, including history, physical examination, radiographic findings, and laboratory data. Microbial Causes of Infection: Infections may be caused by bacteria, viruses, fungi, and parasites. The pathogen may be exogenous (acquired from environmental or animal sources or from other persons) or endogenous (from the normal flora)
Specimen Selection, Collection, and Processing I The quantity material must be adequate I Specimens are selected on the basis of signs and symptoms, should be representative of the disease p rocess I Contamination of the specimen must be avoided by using only sterile equipment and aseptic precautions The specimen must be taken to the laboratory and examined promptly. special transport media may be helpful. I Meaningful specimens to diagnose bacterial infections must be secured before antimicrobial drugs are administered
Specimen Selection, Collection, and Processing The quantity material must be adequate Specimens are selected on the basis of signs and symptoms, should be representative of the disease process Contamination of the specimen must be avoided by using only sterile equipment and aseptic precautions The specimen must be taken to the laboratory and examined promptly. Special transport media may be helpful. Meaningful specimens to diagnose bacterial infections must be secured before antimicrobial drugs are administered
Microbiologic Examination Culture: Isolation of infectious agents frequently requires specialized media Nonselective(noninhibitory) media permit the growth of many microorganisms Selective media contain inhibitory substances that permit the isolation of specific types of microorganisms Microbial Identification: Colony and cellular morphology may permit preliminary identification Growth characteristics under various conditions utilization of carbohydrates and other substrates, enzymatic activity, immunoassays, and genetic probes are also used Antimicrobial Susceptibility: Microorganisms, particularly bacteria, are tested in vitro to determine whether they are susceptible to antimicrobial agents Serodiagnosis: A high or rising titer of specific IgG antibodies or the presence of specific IgM antibodies may suggest or confirm a diagnosis 1 Direct Examination and Techniques: Direct examination of specimens reveals gross pathology. Microscopy may identify microorganisms. Immunofluorescence immuno-peroxidase staining, and other immunoassays may detect specific microbial antigens. Genetic probes identify genus-or species-specific DNA or RNA sequences
Microbiologic Examination Culture:Isolation of infectious agents frequently requires specialized media. Nonselective (noninhibitory) media permit the growth of many microorganisms. Selective media contain inhibitory substances that permit the isolation of specific types of microorganisms. Microbial Identification: Colony and cellular morphology may permit preliminary identification. Growth characteristics under various conditions, utilization of carbohydrates and other substrates, enzymatic activity, immunoassays, and genetic probes are also used. Antimicrobial Susceptibility: Microorganisms, particularly bacteria, are tested in vitro to determine whether they are susceptible to antimicrobial agents. Serodiagnosis:A high or rising titer of specific IgG antibodies or the presence of specific IgM antibodies may suggest or confirm a diagnosis. Direct Examination and Techniques: Direct examination of specimens reveals gross pathology. Microscopy may identify microorganisms. Immunofluorescence, immuno-peroxidase staining, and other immunoassays may detect specific microbial antigens. Genetic probes identify genus- or species-specific DNA or RNA sequences
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Antibiotic susceptibility tests Minimum inhibitory concentration test Disk diffusion test ④ ··" ",", Susceptible organism ∵∴ 0 2 4 8 B 4垂 Resistant organism 0 2 ug/ml antibiotic 10 ug antibiotic in discs
Artificial active immunity Vaccines are antigens prepared from pathogens that can raise a protective immune response, yet do not cause illness. These prepared antigens will stimulate both b cells and T cells and help to create memory cells that can later mount a vigorous immune response to an encounter with the real pathogen. Toxoids: a modified form of the toxin that preserves its antigenicity but has lost its toxicity. This has been spectacularly successful with tetanus and diphtheria I Inactivated vaccines: The production of protective antibodies is stimulated by using the killed (inactivated)organisms This is done as a routine with vaccines against pertussis(whooping cough), typhoid and influenza. There is also an inactivated polio vaccine Attenuated live vaccines The approach is to use suspensions of living organisms that are reduced in their virulence(attenuated) but still immunogenic. This strategy has yielded: BCG, mumps, measles, and rubella vaccines(now combined); the live virus polio vaccine Special vaccines: polysaccharide vaccine, subunit vaccine, conjugate vaccine bio-engineered vaccine, chemical vaccine, synthetic vaccine ) nucleic acid vaccine idiotype vaccine, autovaccine, etc
Artificial active immunity Toxoids: a modified form of the toxin that preserves its antigenicity but has lost its toxicity. This has been spectacularly successful with tetanus and diphtheria. Inactivated vaccines: The production of protective antibodies is stimulated by using the killed (inactivated) organisms This is done as a routine with vaccines against pertussis (whooping cough) , typhoid and influenza. There is also an inactivated polio vaccine. Attenuated live vaccines : The approach is to use suspensions of living organisms that are reduced in their virulence (attenuated) but still immunogenic. This strategy has yielded: BCG, mumps, measles , and rubella vaccines (now combined); the live virus polio vaccine. Special vaccines: polysaccharide vaccine, subunit vaccine, ( conjugate vaccine, bio-engineered vaccine, chemical vaccine, synthetic vaccine ), nucleic acid vaccine, idiotype vaccine, autovaccine, etc. Vaccines are antigens prepared from pathogens that can raise a protective immune response, yet do not cause illness. These prepared antigens will stimulate both B cells and T cells and help to create memory cells that can later mount a vigorous immune response to an encounter with the real pathogen
Artificial passive immunity Antitoxin: e.g. Tetanus antitoxin and diphtheria antitoxin. It is raised in the horse It is most important to give an intented recipient of equine serum a prior test dose to exclude hypersensitivity subjects who may have been sensitized by a previous dose of equine serum Pooled immunoglobulin: It contains the normal repertoire of antibodies for an adult, and can protect against hepatitis A, and measles Specific immunoglobulin: Preparations of specific immunoglobulin are available for passive immunization against tetanus, hepatitis B, rabies, varicella-zoster Cytokine
Artificial passive immunity Antitoxin: e.g. Tetanus antitoxin and diphtheria antitoxin. It is raised in the horse .It is most important to give an intented recipient of equine serum a prior test dose to exclude hypersensitivity subjects who may have been sensitized by a previous dose of equine serum. Pooled immunoglobulin: It contains the normal repertoire of antibodies for an adult, and can protect against hepatitis A, and measles. Specific immunoglobulin: Preparations of specific immunoglobulin are available for passive immunization against tetanus, hepatitis B, rabies, varicella-zoster. Cytokine
Active-passive immunity involves giving both a vaccine to provide long-term protection(preventive infection) and immune globulin to provide immediate protection(therapeutic and preventive infectious disease)
Active-passive immunity involves giving both a vaccine to provide long-term protection (preventive infection) and immune globulin to provide immediate protection (therapeutic and preventive infectious disease)
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