Understanding the Clinical Understanding the Clinical Microbiology LaboratoryMicrobiology Laboratory

Carol R. Quinter Ph.D.Carol R. Quinter Ph.D.

January, 2007January, 2007

Is This Possible?!!Is This Possible?!!

The Role of the Clinical Microbiology LaboratoryThe Role of the Clinical Microbiology Laboratory

Clarify the presence of infectionClarify the presence of infection Specify the etiologySpecify the etiology Motivate the appropriate selection of antimicrobicMotivate the appropriate selection of antimicrobic Promote the appropriateness of use of antimicrobicPromote the appropriateness of use of antimicrobic Assist in the identification, control, and prevention of Assist in the identification, control, and prevention of

nosocomial infectionsnosocomial infections Assist in the identification, control, and prevention of Assist in the identification, control, and prevention of

infections in the communityinfections in the community

The quality microbiology laboratory will lead a physician to a The quality microbiology laboratory will lead a physician to a specific diagnosis by requiring quality specimens which specific diagnosis by requiring quality specimens which

result in relevant information which when communicated in result in relevant information which when communicated in a timely manner results in appropriate therapy.a timely manner results in appropriate therapy.

ResponsibilityResponsibility

Accurate, Accurate, Clinically Relevant, Clinically Relevant, Timely DataTimely Data

Garbage In—Garbage OutGarbage In—Garbage Out

250 million annually is wasted by the 250 million annually is wasted by the processing of processing of improperly obtained improperly obtained and and clinically irrelevant clinically irrelevant specimens, specimens, which results in:which results in:

Bad InformationBad Information

Becomes part of a patient’s Becomes part of a patient’s medical recordmedical record

Has little value in patient careHas little value in patient care Perpetuates the misuse and Perpetuates the misuse and

overuse of antimicrobialsoveruse of antimicrobials Contributes to the morbidity Contributes to the morbidity

and mortality of nosocomial and mortality of nosocomial infectionsinfections

Has an adverse effect on Has an adverse effect on length of staylength of stay

Has a negative effect on Has a negative effect on quality of care and patient quality of care and patient outcomeoutcome

Function of the Microbiology LaboratoyFunction of the Microbiology Laboratoy

Determine the Etiology of the Infectious ProcessDetermine the Etiology of the Infectious Process Microscopic ExaminationMicroscopic Examination CultureCulture ImmunochemicalImmunochemical MolecularMolecular

Microscopic ExaminationMicroscopic Examination

Gram-stained Smear:Gram-stained Smear: TimelyTimely Presumptive identification of etiologyPresumptive identification of etiology Drives empiric therapyDrives empiric therapy Assesses quality of specimen and predicts clinical Assesses quality of specimen and predicts clinical

relevance of culture resultsrelevance of culture results Guide to the determination of colonization vs. Guide to the determination of colonization vs.

infectioninfection

Interpretation of Gram-stained SmearInterpretation of Gram-stained Smear

Adequacy of specimen measured by presence of Adequacy of specimen measured by presence of inflammation (WBC, RBC, Necrotic Debris)inflammation (WBC, RBC, Necrotic Debris)

Presence of epithelial elements may indicate Presence of epithelial elements may indicate specimen inadequacy. Look for ratio of 2:1, specimen inadequacy. Look for ratio of 2:1, WBC:EpiWBC:Epi

Morphologic diversity of organisms present and Morphologic diversity of organisms present and their relative numbers is important and can their relative numbers is important and can provide important clinical cluesprovide important clinical clues

Focus on predominant morphologic type(s)Focus on predominant morphologic type(s) Alert to unusual pathogenAlert to unusual pathogen

Normal FloraNormal Flora

Specimens which are obtained from or through areas where Specimens which are obtained from or through areas where normal flora exists, will grow normal flora.normal flora exists, will grow normal flora.

Normal flora is predictable and changes within 24 hours of Normal flora is predictable and changes within 24 hours of hospitalization to hospital flora.hospitalization to hospital flora.

All infectious agents establish themselves at portals of entry, All infectious agents establish themselves at portals of entry, prior to producing infection, hence become:prior to producing infection, hence become:

““normal flora”normal flora”

Accessible sites to culture usually have large numbers of Accessible sites to culture usually have large numbers of normal flora.normal flora.

Dilemma of Colonization vs. InfectionDilemma of Colonization vs. Infection

All data All data must be must be interpreted clinically.interpreted clinically.

CultureCulture

Historic, remains gold standardHistoric, remains gold standard Not timelyNot timely Laboratory is adverse environmentLaboratory is adverse environment Host is adverse environmentHost is adverse environment Depends on the laboratory’s ability to provide the Depends on the laboratory’s ability to provide the

organism with favorable conditions to groworganism with favorable conditions to grow

ImmunochemicalImmunochemical

Monoclonal AntibodiesMonoclonal Antibodies Substances (antigens) Substances (antigens)

foreign to the body invoke foreign to the body invoke the production of the production of antibodies which are highly antibodies which are highly specific.specific.

Monoclonal antibody Monoclonal antibody technology allows us to technology allows us to produce large amounts of produce large amounts of pure antibody which reacts pure antibody which reacts to a specific antigen.to a specific antigen.

Principal ToolsPrincipal Tools

Direct Fluorescent AntibodyDirect Fluorescent Antibody Indirect Fluorescent AntibodyIndirect Fluorescent Antibody ELISAELISA

Sensitivity—The ability to detectSensitivity—The ability to detect Specificity—The ability to detect preciselySpecificity—The ability to detect precisely

How Does It Work?How Does It Work?

PearlsPearls

A positive is a postiveA positive is a postive

A negative means further testingA negative means further testing

MolecularMolecular

ProbesProbes

Amplification—Gene or SignalAmplification—Gene or Signal

Pulse GelPulse Gel

Usefulness of Molecular TechnologyUsefulness of Molecular Technology

Rapid diagnosis of infection, particularly in sterile Rapid diagnosis of infection, particularly in sterile body sites and particularly where numbers of body sites and particularly where numbers of organisms may be low and culture difficult organisms may be low and culture difficult

Characterization of strains for epidemiologic Characterization of strains for epidemiologic purposespurposes

Rapid identification of isolates which otherwise Rapid identification of isolates which otherwise require complex procedures which are costly and require complex procedures which are costly and take too much timetake too much time

Appropriate designation of genus and species of Appropriate designation of genus and species of organismsorganisms

Detection of resistanceDetection of resistance

Susceptibility TestingSusceptibility Testing

Minimum Inhibitory ConcentrationMinimum Inhibitory ConcentrationMICMIC - -Lowest Concentration of antimicrobic which Lowest Concentration of antimicrobic which will inhibit will inhibit in vitro in vitro growth of microorganism. growth of microorganism.

Minimum Bacteriocidal ConcentrationMinimum Bacteriocidal ConcentrationMBC -Lowest Concentration of antimicrobic which MBC -Lowest Concentration of antimicrobic which will kill a microorganism will kill a microorganism in vitro.in vitro.

ToleranceTolerance

The relationship of MIC to The relationship of MIC to MBC in any drug/bug MBC in any drug/bug combination.combination.

Interpretation of MICInterpretation of MIC

Based on achievable concentration of antimicrobic Based on achievable concentration of antimicrobic following IM injection in healthy subjects.following IM injection in healthy subjects.

In general, the achievable In general, the achievable in vivo concentration in vivo concentration should be 2 to 4 times the MIC for an organism to should be 2 to 4 times the MIC for an organism to test susceptible to the antimicrobic.test susceptible to the antimicrobic.

The The Therapeutic Index Therapeutic Index is the relationship of MIC is the relationship of MIC to antimicrobic level.to antimicrobic level.

The FutureThe Future

Infectious diseases continue to Infectious diseases continue to impose a huge global public health impose a huge global public health burden, accounting for more than burden, accounting for more than one-quarter of all deaths annually one-quarter of all deaths annually and similar fraction of morbidity.and similar fraction of morbidity.

ChallengesChallenges

New and changing pathogensNew and changing pathogens Global eradication of old pathogensGlobal eradication of old pathogens Developing diagnosticsDeveloping diagnostics Developing treatments and preventions and managing Developing treatments and preventions and managing

resistanceresistance Control of infections within institutions and other closed Control of infections within institutions and other closed

settings and designing effective surveillance strategiessettings and designing effective surveillance strategies Control of infectious disease outbreaksControl of infectious disease outbreaks Understanding the role of animal and insect reservoirsUnderstanding the role of animal and insect reservoirs Prevention of bioterrorismPrevention of bioterrorism