Clinical Diagnosis, Clinical Study and Epidemiology

What is the aim of clinical microbiology?

To provide accurate and timely information about microbes involved in patients’ disease processes, perform antibody testing, and provide information on antimicrobial susceptibility of isolated bacteria.

What must be ensured for meaningful lab testing?

Correct specimen type, collected correctly, at the correct time, and sent to the lab quickly using correct transport conditions.

What factors should be considered during specimen collection?

Specimens should be taken from the actual site of infection, collected during the acute phase of disease, before antimicrobial therapy, and without contamination from normal flora or non-sterile equipment.

Why do some bacteria not take up Gram stain?

Due to their waxy mycolic cell wall.

What is the primary stain used in the acid-fast stain process?

Carbolfuchsin.

What is the purpose of acid-fast staining (Ziehl-Neelsen stain)?

To identify bacteria, particularly mycobacteria, that do not take up Gram stain due to their waxy mycolic cell wall.

What does the fluorescence staining technique involve?

Detecting labeled antibodies binding to antigens of pathogens.

What is the role of an electron microscope in clinical microbiology?

It allows for direct identification of virus particles and detection of viruses in specimens.

Why is culture considered the gold standard in microbiology?

It enables antibiotic or antifungal sensitivity testing.

What are the challenges of culturing microorganisms?

It is labor-intensive, slow, and fastidious microbes may not grow in artificial media.

What is ELISA primarily used for?

To detect specific antibodies or antigens.

It binds antigens to a solid phase, adds unknown antibodies, and detects bound antibodies using labeled anti-antibodies.

What types of antibodies are typically detected in clinical diagnostics?

IgM antibodies indicate active infection, while IgG antibodies indicate past exposure to a pathogen.

What is the hemagglutination inhibition assay used for?

It is primarily used for diagnosing influenza by observing reactions between viruses and red blood cells.

How do molecular methods like qPCR enhance diagnostic capabilities in clinical microbiology?

They allow for rapid detection of specific pathogens and can identify antibiotic resistance genes efficiently.

Methods for detecting antibodies

Hemaglutination inhibition assay, class switching recombination, ELISA, western blotting, immunochromatographic test

What does the term 'incidence' refer to in epidemiology?

The number of new cases occurring in a population during a specific period of time.

What is the difference between prevalence and incidence?

Prevalence is the number of existing cases at a given point in time, while incidence is the number of new cases over time.

What does the epidemiological triangle illustrate?

The interconnectedness of the susceptible host, vehicles, and sources in the study of disease epidemiology.

What does R0 represent in infectious disease epidemiology?

R0 is the average number of secondary cases produced by each infectious case in a totally susceptible population, calculated as R0=c×d×p, where c is the number of contacts per unit time, d is the duration of infectiousness, and p is the transmission probability

How does the effective reproduction number (Rt) differ from R0?

Rt represents the average number of secondary cases in a population where not all individuals are susceptible; it reflects current transmission dynamics based on immunity levels in the population

Interpret Rt values: what do they indicate about an outbreak?

• Rt>1: The outbreak will increase exponentially.

• Rt=1: The outbreak is stable; the number of cases remains constant.

• Rt<1: The outbreak will slow down over time.

What is herd immunity?

Protection for susceptible individuals that occurs when a significant proportion of the population becomes immune to an infectious disease through vaccination or prior infection.

What is the purpose of a case-control study?

identifies individuals with an outcome (cases) and compares them to a representative group without the outcome (controls) regarding their past exposures

What does an odds ratio indicate in case-control studies?

It represents the odds of disease in the exposed group compared to the odds of disease in the unexposed group.

What is a cohort study?

A study that compares groups with or without exposure to identify risk factors.

They are used to identify risk factors, quantify odds ratios between diseased and non-diseased groups, but are not suitable for rare diseases due to low incidence rates.

What does a cross-sectional study measure?

The frequency of an outcome and/or exposure in a defined population at a given time frame.

They are used to identify the prevalence of diseases and associated risk factor.

What are some ways to diagnose infections?

Direct visualization, culture, nucleic acid detection, and antigen detection.

What is the definition of epidemiology?

The study of distribution and determinants of health-related states or events in specified populations.

What type of study provides descriptive data about emerging infectious diseases?

Case report or case series.

What is the incubation period?

infected individual being able to transmit infectious agent

What does the term 'latent period' refer to?

The time between infection and the individual becoming infectious.

What does 'class switching recombination' refer to?

A process by which B cells change the class of antibody they produce.

Window period

Time between infection and when diagnostic tests first become positive.

Incubation period

Time from infection until symptoms develop.