Basic Concepts of Epidemiology and Microbial Pathogenesis, Infectious Diseases and Pathogens: Key Concepts and Treatments, Microorganism Identification & Classification: Key Concepts for Microbiology

What is an endemic disease?

A disease that is constantly present in a population or geographic area, e.g., the common cold in the United States.

Define sporadic disease.

Diseases that occur infrequently and irregularly with no predictable pattern, e.g., Creutzfeldt-Jakob Disease (CJD) from 2007-2020.

What characterizes an epidemic?

An unusually large number of cases above what is expected in a specific area or population, e.g., the 2009 H1N1 Influenza.

What is the difference between an outbreak and an epidemic?

An outbreak is similar to an epidemic but typically refers to a more limited geographic area or smaller number of cases.

What is a pandemic?

An epidemic that has spread over multiple countries or continents, usually affecting a large number of people, e.g., COVID-19.

Why are epidemiologists more concerned with rates than absolute numbers?

Rates provide a better understanding of the impact of disease relative to the population size.

What is the attack rate?

The percentage of people who become ill in a population after exposure to an infectious agent.

What does the basic reproductive number (R0) indicate?

It indicates the potential for spread of an infectious disease; if R0 > 1, the infection can spread; if R0 < 1, it will likely die out.

Define incidence in epidemiology.

The number of new cases of a disease in a specific time and population, measuring the risk of developing the disease.

What is prevalence?

The total number of cases of a disease at any time or for a specific time in a specific population, providing a snapshot of disease spread.

What is morbidity?

The incidence of disease in a population.

Define mortality.

The overall death rate in a population.

What is the case-fatality rate?

The percentage of a population that dies from a specific disease.

What is vertical transmission?

Transmission of a disease from a pregnant woman to her fetus or from mother to infant during childbirth or breastfeeding.

What is horizontal transmission?

Transmission of a disease by any method other than vertical transmission, e.g., person to person via air or contact.

What is direct transmission?

Immediate transfer of an infectious agent to a portal of entry, e.g., through direct contact or droplet transmission.

What are fomites?

Inanimate objects that can transmit pathogens, such as clothing, keyboards, and doorknobs.

What is herd immunity?

Protection of non-immune individuals in a population when a sufficient percentage (typically >90%) are immune.

What are prokaryotic cells?

Cells that do not have a membrane-bound nucleus.

What are eukaryotic cells?

Cells that have a membrane-bound nucleus and organelles.

What is the binomial system of nomenclature?

A system for naming organisms using two words: the genus (capitalized) and the specific epithet (not capitalized), both italicized.

What are proteins composed of?

One or more chains of subunits called amino acids, which fold into complex three-dimensional shapes.

What is the role of nucleic acids?

They store genetic information needed to build and maintain a cell; DNA is double-stranded, while RNA is single-stranded.

What is the structure of the cytoplasmic membrane in prokaryotic cells?

A phospholipid bilayer embedded with proteins, where hydrophobic tails face inward and hydrophilic heads face outward.

What is peptidoglycan?

A mesh-like network made up of sugars and amino acids that forms the cell wall of bacteria.

What distinguishes Gram-positive from Gram-negative bacteria?

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer with an outer membrane made of lipopolysaccharide.

What is considered an endotoxin?

Lipid A, a component of lipopolysaccharides (LPS), is considered an endotoxin.

What severe immune response can large quantities of LPS cause?

Septic shock (endotoxic shock).

What happens when treating gram-negative bacterial infections?

It can release Lipid A into the bloodstream, leading to septic shock.

What does the immune system recognize in gram-negative bacteria?

The Lipid A portion of lipopolysaccharides (LPS).

What are some symptoms of septic shock?

Fever, hypotension, tachycardia, respiratory distress, and organ failure.

What are biofilms?

Polysaccharide-encased communities of microorganisms that enhance survival in diverse environments.

What is quorum sensing?

A chemical signaling process for coordinated, collective behavior among microorganisms.

What are the five distinct stages of the growth curve in a closed system?

1. Lag phase, 2. Log phase, 3. Stationary phase, 4. Death phase, 5. Phase of prolonged decline.

What characterizes the lag phase of microbial growth?

Microorganisms are adapting and not dividing.

What is the optimal temperature range for mesophiles?

77°F to 113°F, with pathogens typically growing at 95°F to 104°F.

What temperature range do psychrophiles thrive in?

23°F to 59°F, typically found in Arctic and Antarctic regions.

What is the significance of the term 'psychrotrophs'?

They spoil refrigerated foods and thrive at temperatures from 23°F to 86°F.

What is the temperature range for thermophiles?

77°F to 158°F, commonly found in hot springs and compost heaps.

What defines hyperthermophiles?

Organisms that thrive at temperatures of 158°F or greater, usually archaea found in hydrothermal vents.

What is the pH range for neutrophiles?

A range of pH 5-8, with an optimum near pH 7.

What is the optimal pH for acidophiles?

They grow at pH below 5.5, with some like Picrophilus oshimae thriving at less than pH 1.

How do bacteria maintain their internal pH?

They typically maintain a constant internal pH near pH 7 and can pump out or bring in H+ ions as needed.

What is the role of urease produced by Helicobacter pylori?

It splits urea into CO2 and ammonia, decreasing acidity around itself.

What is the method to determine oxygen requirements in microorganisms?

Using a shake tube method where solidified agar slows gas diffusion.

What are obligate aerobes?

Microorganisms that require oxygen to survive, such as Micrococcus luteus.

What defines obligate anaerobes?

They cannot use oxygen for growth, such as Clostridium botulinum.

What are facultative aerobes?

Organisms that can use oxygen but do not require it, like E. coli.

What are aerotolerant anaerobes?

Obligate fermenters that can grow in oxygen but do not use it, such as Streptococcus pyogenes.

What are microaerophiles?

Organisms that require small amounts of oxygen for growth, such as Helicobacter pylori.

What is the pH range for alkaliphiles?

Alkaliphiles grow at pH above 8.5.

What is the typical pH range for Vibrio cholerae?

Vibrio cholerae has a pH range of 6.0 - 11.0.

What are halotolerant organisms?

Halotolerant organisms can withstand up to 10% NaCl.

What is the difference between halophiles and extreme halophiles?

Halophiles require high salt (3% for some marine bacteria), while extreme halophiles need more than 9% salt.

What is nitrogen fixation?

Nitrogen fixation is the conversion of N2 gas to ammonia and its incorporation into organic compounds.

What are the major elements needed for microbial growth?

Carbon, oxygen, hydrogen, and nitrogen.

What distinguishes heterotrophs from autotrophs?

Heterotrophs use organic carbon, while autotrophs use inorganic carbon as CO2.

What is the role of phosphorus and iron in microbial growth?

Phosphorus and iron are often limiting nutrients that dictate the maximum level of microbial growth.

What is sterilization?

Sterilization is the removal or destruction of all microorganisms and viruses.

What is the purpose of disinfection?

Disinfection eliminates most or all pathogens, but some viable microbes may remain.

What is the commercial canning process designed to destroy?

The commercial canning process is designed to destroy Clostridium botulinum endospores.

What is the primary function of the electron transport chain in respiration?

The electron transport chain generates a proton motive force that drives ATP synthesis.

What is the central dogma of molecular biology?

The central dogma is DNA → RNA → Protein.

What happens during the initiation of DNA replication?

Helicases unzip DNA strands, revealing template sequences.

What is a frameshift mutation?

A frameshift mutation occurs due to the addition or deletion of one or two nucleotides, leading to a different set of codons translated.

What are enterics?

Enterics are Gram-negative rods found in the intestinal tract of humans and other animals.

What is the significance of coliforms?

Coliforms, like E. coli, are lactose fermenters and indicators of possible fecal pollution.

What are bacteriophages?

Bacteriophages are viruses that infect bacteria and are important for horizontal gene transfer.

What is the structure of a virion?

A virion is composed of nucleic acid surrounded by a capsid, which protects it from enzymes and toxic chemicals.

What is the function of spikes on viruses?

Spikes attach to receptor sites on host cells, facilitating viral entry.

What is the lytic cycle of phage infections?

The lytic cycle involves attachment, genome entry, synthesis, assembly, and release of new phages.

What is the role of DNA ligase in DNA replication?

DNA ligase seals gaps between Okazaki fragments during DNA replication.

What is the significance of the Krebs cycle?

The Krebs cycle completes the oxidation of glucose, producing ATP, NADH, and FADH2.

What is oxidative phosphorylation?

Oxidative phosphorylation is the process of synthesizing ATP from ADP using the energy from the electron transport chain.

What is the primary difference between aerobic and anaerobic respiration?

Aerobic respiration uses O2 as the terminal electron acceptor, while anaerobic respiration uses a molecule other than O2.

What is the function of compatible solutes in halotolerant organisms?

Compatible solutes help halotolerant organisms withstand increased osmotic pressure.

What is the significance of the 12 D process in commercial canning?

The 12 D process reduces 10^12 endospores to only 1, ensuring safety against botulinum toxin in canned foods.

What is the role of lysozyme in the immune response?

Lysozyme digests the cell wall of bacteria, leading to cell lysis and the release of phages.

What type of viruses are retroviruses, and how do they replicate?

Retroviruses are (+) ssRNA viruses that use reverse transcriptase to synthesize DNA from RNA.

What is innate immunity?

Innate immunity is the non-specific routine protection present at birth.

How does adaptive immunity develop?

Adaptive immunity develops throughout life as the body is exposed to microbes or foreign materials.

What is the function of antibodies in the immune response?

Antibodies bind to antigens, targeting them for destruction.

What are the first-line defenses in the immune system?

First-line defenses include barriers that block entry, such as skin and mucous membranes.

What are sentinel cells and their role in the immune system?

Sentinel cells use pattern recognition receptors (PRRs) to identify unique microbial components.

What is the complement system?

The complement system is a part of the immune system that enhances the ability to clear microbes and damaged cells.

What is the function of phagocytes?

Phagocytes engulf and destroy microbes or cell debris through phagocytosis.

What is the role of interferon (IFN) during a viral infection?

Interferon is a protein secreted during viral infections that helps inhibit viral replication.

What are antimicrobial peptides (AMPs)?

Antimicrobial peptides, like defensins, form pores in microbial membranes to kill pathogens.

What are the main types of granulocytes and their functions?

Neutrophils destroy bacteria, eosinophils fight parasitic worms, and basophils are involved in allergic reactions.

What is the mononuclear phagocyte system (MPS)?

The MPS comprises monocytes that can differentiate into macrophages and dendritic cells.

What is the role of B cells in the adaptive immune response?

B cells produce antibodies that target specific antigens.

What are T cells responsible for in the immune system?

T cells are responsible for cell-mediated immunity and help eliminate infected or corrupt 'self' cells.

What is the difference between cytotoxic T-cells and helper T-cells?

Cytotoxic T-cells induce apoptosis in infected cells, while helper T-cells assist in activating other immune cells.

What are cytokines and their groups?

Cytokines are signaling proteins; groups include chemokines, CSFs, interferons, interleukins, and TNF.

What is a cytokine storm?

A cytokine storm is an overproduction of cytokines that can be deadly during an immune response.

What is humoral immunity?

Humoral immunity eliminates microbial invaders and toxins in the blood or tissue fluids, involving B cells.

What are epitopes?

Epitopes are distinct regions of antigens recognized by the adaptive immune system.

What are the five classes of immunoglobulins (Ig)?

IgM, IgG, IgA, IgD, and IgE, each with specific functions in the immune response.

What is the function of IgM?

IgM is the first antibody produced during the primary immune response and is effective in agglutinating pathogens.

What is the role of IgG in immunity?

IgG is the most abundant antibody, providing long-term immunity and can cross the placenta.