Microbiology
Bacteria and Pathogens Flashcards
34 bacteria and pathogen terms every pre-nursing microbiology course expects you to define
34 cards~9 min
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All 34 Microbiology Bacteria and Pathogens flashcards
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- Acid-Fast Stain
- A staining method for bacteria whose waxy mycolic-acid cell wall resists ordinary dyes; these organisms hold the red carbol fuchsin even after an acid-alcohol wash.For example: The Ziehl-Neelsen stain reveals Mycobacterium tuberculosis in a sputum sample.
- Bacillus (Rod)
- A bacterium with an elongated rod or cylinder shape, in contrast to spherical cocci, and one of the basic morphologies reported on a Gram stain.For example: Escherichia coli and Bacillus anthracis are both rod-shaped.
- Capsule
- A sticky outer layer, usually of polysaccharide, surrounding some bacteria that resists being engulfed by immune cells, making it a major virulence factor rather than a structural essential.For example: The capsule of Streptococcus pneumoniae lets it evade phagocytes; vaccines target it.
- Catalase
- A bacterial enzyme that breaks hydrogen peroxide into water and oxygen; the bubbling test using it separates the staphylococci, which are positive, from the streptococci, which are negative.For example: Adding peroxide to a Staphylococcus colony makes it fizz.
- Clostridioides Difficile
- A gram-positive, spore-forming, obligate anaerobe that overgrows the colon after antibiotics wipe out normal flora, producing toxins that cause severe diarrhea and pseudomembranous colitis.For example: It commonly flares in hospitalized patients after broad-spectrum antibiotics.
- Coagulase
- An enzyme that clots blood plasma; the test for it identifies Staphylococcus aureus, which is positive, and separates it from the coagulase-negative staphylococci like S. epidermidis.For example: A positive result on a suspicious skin isolate points to Staphylococcus aureus.
- Coccus
- A bacterium with a spherical or roughly round shape, named for the arrangement it forms after division, such as pairs, chains, or grape-like clusters.For example: Staphylococci sit in clusters while streptococci line up in chains.
- Endospore
- A dormant, tough survival structure that certain gram-positive bacteria form inside themselves, resisting heat, drying, and disinfectants until conditions improve and the cell resumes growing.For example: Clostridium and Bacillus species form endospores that survive boiling.
- Endotoxin
- The lipid A part of gram-negative lipopolysaccharide, a toxin released when the cell wall breaks apart, provoking fever, inflammation, and in large amounts life-threatening shock.For example: Rapid killing of gram-negative bacteria can release enough of it to trigger septic shock.
- Escherichia Coli
- A gram-negative rod and facultative anaerobe that is a normal gut resident, yet the leading cause of urinary tract infections and, in certain strains, foodborne illness.For example: Strain O157:H7 causes bloody diarrhea from undercooked beef.
- Exotoxin
- A toxic protein actively secreted by living bacteria, often highly potent and targeted at a specific tissue, and frequently the direct cause of a disease's symptoms.For example: The botulinum exotoxin blocks nerve signaling and causes paralysis.
- Facultative Anaerobe
- A bacterium that uses oxygen for respiration when it is present but can switch to fermentation and grow without it, thriving across a wide range of conditions.For example: Escherichia coli grows with or without oxygen, which is why it colonizes the gut so successfully.
- Flagellum
- A long, whip-like protein appendage that rotates to propel a bacterium through liquid, giving it directed motility toward nutrients or away from harm.For example: Escherichia coli swims using several of these rotating filaments.
- Gram Stain
- A differential staining technique that sorts most bacteria into two groups by how their cell wall holds the crystal violet dye after an alcohol wash, guiding early identification.For example: A clinician orders it first on cerebrospinal fluid because the result narrows the likely organism within minutes.
- Gram-Negative
- A bacterium with a thin peptidoglycan layer sandwiched under an outer membrane, so alcohol strips the crystal violet and the safranin counterstain leaves it pink or red.For example: Escherichia coli and Neisseria both appear pink after the counterstain.
- Gram-Positive
- A bacterium whose thick peptidoglycan layer traps the crystal violet–iodine complex during decolorization, so the cell appears purple under the microscope after Gram staining.For example: Staphylococcus and Streptococcus both stain deep purple.
- Helicobacter Pylori
- A curved, helical gram-negative bacterium that colonizes the stomach lining and produces urease to neutralize acid, and is the main cause of peptic ulcers and chronic gastritis.For example: Its discovery overturned the belief that ulcers came only from stress and acid.
- Lipopolysaccharide (LPS)
- The large molecule making up the outer membrane of gram-negative bacteria, whose toxic lipid A portion is the endotoxin that triggers fever and shock when the cell dies.For example: A flood of it released during a gram-negative bloodstream infection can drive septic shock.
- MRSA
- Methicillin-resistant Staphylococcus aureus, a strain carrying the mecA gene that makes it resistant to methicillin and most beta-lactam antibiotics, complicating treatment of its infections.For example: Hospital and community outbreaks of hard-to-treat skin and wound infections.
- Mycobacterium Tuberculosis
- A slow-growing, acid-fast bacterium with a waxy mycolic-acid wall that causes tuberculosis, spreading through inhaled droplets and typically attacking the lungs.For example: It is detected on an acid-fast stain of sputum.
- Normal Flora (Microbiota)
- The community of microorganisms that routinely live on and inside a healthy body without causing harm, often competing with pathogens and aiding functions like digestion.For example: The bacteria of the large intestine help produce vitamin K.
- Nosocomial Infection
- An infection acquired in a healthcare setting during treatment for another condition, also called a hospital-acquired infection, often involving drug-resistant organisms and devices like catheters.For example: A catheter-associated urinary tract infection picked up during a hospital stay.
- Obligate Aerobe
- A bacterium that requires oxygen to grow because it depends on aerobic respiration and cannot generate enough energy without it.For example: Mycobacterium tuberculosis favors the oxygen-rich upper lungs.
- Obligate Anaerobe
- A bacterium that grows only without oxygen, because oxygen produces toxic byproducts it lacks the enzymes to neutralize, so exposure to air kills it.For example: Clostridioides difficile thrives in the low-oxygen colon.
- Opportunistic Pathogen
- A microbe that is usually harmless but causes disease when it reaches an unusual site or when a host's defenses are weakened by illness, injury, or immune suppression.For example: Candida and some staphylococci turn dangerous in immunocompromised patients.
- Pathogen
- A microorganism capable of causing disease in a host, distinguished from the harmless or beneficial microbes that make up most of the microbial world.For example: Salmonella is a pathogen, while most gut bacteria are not.
- Peptidoglycan
- The mesh-like polymer of sugar chains cross-linked by short peptides that forms the bacterial cell wall, giving the cell its shape and resistance to bursting under osmotic pressure.For example: Penicillin works by blocking the cross-links that hold this mesh together.
- Pilus (Fimbria)
- A short hair-like surface projection that lets a bacterium stick to host cells or surfaces; a specialized longer sex pilus instead pulls two cells together for gene transfer.For example: Neisseria gonorrhoeae uses pili to anchor to the urethral lining.
- Spirochete
- A slender, spiral or corkscrew-shaped bacterium that moves by internal axial filaments running along its length, producing a distinctive twisting motility hard to see on a standard Gram stain.For example: Treponema pallidum, the cause of syphilis, is a spirochete.
- Staphylococcus Aureus
- A gram-positive coccus growing in grape-like clusters that is catalase-positive and coagulase-positive, causing skin abscesses, food poisoning, and more serious bloodstream and heart-valve infections.For example: It is a leading cause of boils, wound infections, and endocarditis.
- Streptococcus Pneumoniae
- A gram-positive, lancet-shaped diplococcus with a protective polysaccharide capsule, the most common cause of community-acquired pneumonia and a frequent cause of meningitis and ear infections.For example: Its capsule is the target of the pneumococcal vaccine.
- Streptococcus Pyogenes
- A gram-positive coccus arranged in chains, the Group A beta-hemolytic streptococcus, responsible for strep throat, impetigo, scarlet fever, and post-infectious rheumatic fever.For example: It is the organism behind classic strep throat.
- Virulence Factor
- Any bacterial trait or molecule, such as a capsule, toxin, or adhesin, that helps an organism colonize a host, evade defenses, or cause damage and thereby produce disease.For example: A capsule, a secreted toxin, and surface pili are all virulence factors.
- Zoonosis
- An infectious disease that spreads from animals to humans, whether by direct contact, bites, contaminated food, or an insect vector carrying the organism between species.For example: Rabies and Lyme disease are zoonoses.