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basic bacteriology Flashcards

1
Q

Identify the chemical composition and the two main functions of the peptidoglycan layer in bacteria.

A

It has a sugar backbone with cross-linked peptide side chains, and provides rigid support and protection against osmotic damage

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2
Q

A hospitalized 86-year-old has S. pneumoniae. His roommate has an E. coli UTI. Which structures do these bacteria have in common?

A

Gram positives (S. pneumoniae) and negatives (E. coli) both have a flagellum, pilus, capsule, peptidoglycan, and cytoplasmic membrane

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3
Q

The two main gram-positive cocci are ____ and ____; the major gram-negative coccus is ____.

A

Staphylococcus and Streptococcus; Neisseria

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4
Q

Name the unique component in the cell membrane of Mycoplasma.

A

The Mycoplasma cell membrane has sterols—there is no cell wall

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5
Q

Name six organisms that do not Gram stain well.

A

Treponema, Mycobacterium, Mycoplasma, Legionella pneumophila, Rickettsia, Chlamydia (these microbesmay lack real color

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6
Q

Which five organisms can be visualized on Giemsa stain?

A

Chlamydia, Borrelia, ricketsiae, trypanosomes, and Plasmodium—remember certain bugs really try my patience)

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7
Q

An unimmunized 1-year-old boy is irritable and sluggish and has a fever and stiff neck. How will you culture the causative organism?

A

He likely has Haemophilus influenzae meningitis, which is cultured on chocolate agar with factors V (NAD+) and X (hematin)

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8
Q

Name three obligate aerobes.

A

Nocardia, Pseudomonas aeruginosa, and Mycobacterium tuberculosis (nagging pests must breathe)

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9
Q

Clostridium, Bacteroides, and Actinomyces all lack ____ and/or ____ ____, making them susceptible to oxidative damage.

A

Catalase; superoxide dismutase (these obligate anaerobes cannot breathe air)

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10
Q

Which organisms are obligate intracellular pathogens? Why?

A

Rickettsia and Chlamydia are intracellular, as they cannot make their own ATP (stay inside [cells] when it is really cold)

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11
Q

Name seven examples of encapsulated bacteria.

A

S. pneumoniae, H. influenzae type B, N. meningitidis, E. coli, Salmonella, K. pneumoniae, & group B Strep (shine skis)

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12
Q

A 16-year-old girl has recurrent S. aureus, Pseudomonas, and Candida infections. What enzyme deficiency is responsible?

A

NADPH oxidase deficiency (chronic granulomatous disease)—these bugs are catalase positive, and they degrade the limited H2O2

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13
Q

For vaccine synthesis against encapsulated bacteria, ____ and ____ are conjugated to promote a ____ (T/B) response.

A

Protein; polysaccharide antigen; T-cell

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14
Q

Which eight bacteria are urease positive?

A

Cryptococcus,H. pylori, Proteus, Ureaplasma, Nocardia,Klebsiella, S. epidermidis, S.saprophyticus (Chuck Norris hates punkss)

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15
Q

Whic four bacteria are pigment-producing? What color pigment does each of them produce?

A

Actinomyces israelii has yellow; S. aureus, yellow; P. aeruginosa, blue-green; and Serratia marcescens, red

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16
Q

A 16-year-old boy has warm red swelling at the site of a cut on his foot. You suspect S. aureus. What protein promotes its virulence?

A

Protein A prevents opsonization and phagocytosis of S. aureus by binding the Fc region of immunoglobulins

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17
Q

Endotoxins are found in gram-____ (positive/negative) bacteria or ____ ; exotoxins are found in gram-____ (positive/negative) bacteria or ____

A

Negative (in the outer membrane); both; negative; both

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18
Q

Name six organisms that have ADP-ribosylating AB toxin.

A

Corynebacterium diphtheriae, Vibrio cholerae, Shigella, E. coli (ETEC and EHEC), Pseudomonas aeruginosa, and Bordetella pertussis

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19
Q

What is the chemical composition of endotoxin and where is it found?

A

Lipopolysaccharide; cell walls of gram negatives (endotoxin is an integral part of the cell wall of gram-negative bacteria)

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20
Q

Transfer of plasmids from one bacterium to another is called ____; the phage-mediated transfer of DNA between prokaryotes is called ____.

A

Conjugation; transduction

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21
Q

The ____ (cell wall/outer membrane) is the main gram-positive surface antigen; the ____ (cell wall/outer membrane) is gram negative.

A

Cell wall; outer membrane

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22
Q

A hospitalized 86-year-old has gram-positive pneumonia; roommate has gram-negative UTI. Which cell structures are unique to these bacteria?

A

Gram positives have lipoteichoic acid; gram negatives have periplasm and an outer membrane formed by endotoxin/lipopolysaccharide

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23
Q

List the six gram-positive bacilli.

A

Clostridium, Corynebacterium, Bacillus, Listeria, Mycobacterium (acid fast and weakly gram positive), and Gardnerella (gram variable)

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24
Q

Mycobacteria have what two distinguishing components in their outer layer?

A

Mycolic acid and high lipid content

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25
Q

A 30-year-old has a painless penile chancre. Why does the causative organism not Gram stain? What two methods can you use to visualize it?

A

Treponema is too thin to be visualized by Gram stain; can be seen by dark-field microscopy and fluorescent antibody staining

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26
Q

Periodic acid–Schiff (PAS) staining is used to stain what types of metabolic substances? What disease can be diagnosed with PAS?

A

Glycogen and mucopolysaccharides (pass the sugar): Whipple disease (Tropheryma whipplei)

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27
Q

A 25-year-old man with multiple sex partners develops dysuria and purulent penile discharge. How is the causative organism cultured? Why?

A

N. gonorrhoeae grows on VPN (nystatin kills fungi.vancomycin kills gram positives, polymyxin kills gram negatives except Neisseria)

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28
Q

Chest x-ray of a patient with reactivated tuberculosis shows apical infiltrates in both lungs. Explain the location of these findings.

A

Lung apices have highest partial pressure of oxygen, and Mycobacterium tuberculosis (and all obligate aerobes) require oxygen to make ATP

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29
Q

Where are anaerobes part of the normal flora? And where are they pathogenic?

A

They are normal flora of the gastrointestinal tract but are pathogenic in all other tissues

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30
Q

Which bacteria are facultative intracellular organisms?

A

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis (some nasty bugs may live facultatively)

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31
Q

A 30-year-old man recently underwent splenectomy and then received a pneumonia vaccine. What is the antigen in the vaccine?

A

The capsular antigen that is conjugated to a protein serves as the antigen

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32
Q

Catalase degrades H2O2 before it is converted to microbicidal products by myeloperoxidase (enzyme). Name seven catalase-positive organisms.

A

Pseudomonas, Listeria, Aspergillus, Candida, E. coli, S. aureus, Serratia (you need placess for your cats [catalase])

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33
Q

Name four vaccines that have been prepared to protect against encapsulated bacteria.

A

Pneumonia (PCV with conjugate, Pneumovax without) and Haemophilus influenzae type B (conjugate) and meningococcal (conjugate) vaccines

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34
Q

____ produces yellow ““sulfur granules.”” What are the granules made of?

A

Actinomyces israelii (Israel has yellow sand); granules composed of filaments of bacteria

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35
Q

Immunoglobulin A protease is secreted by which three bacterial species to help them colonize which part of the body? How does it work?

A

S. pneumoniae, H. influenzae type B, Neisseria (shin), which colonize the respiratory mucosa—IgA protease cleaves IgA

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36
Q

Exotoxins ____ (are/are not) secreted and ____ (mildly/very) toxic; endotoxins ____ (are/are not) secreted and ____ (mildly/very) toxic.

A

are; very (1 µg can be fatal); are not secreted; mildly (hundreds of µg needed for death)

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37
Q

Name three ADP-ribosylating AB toxins whose primary action is overactivation of adenylate cyclase.

A

Vibrio cholerae, enterotoxigenic E. coli (ETEC), and Bordetella pertussis

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38
Q

What is the primary active component of an endotoxin? Which components of the immune response does this agent directly activate?

A

Lipid A; macrophages, which complement (C3a, C5a) tissue factor

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39
Q

What kind of DNA is transferred during transformation: chromosomal, plasmid, or both?

A

Both

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40
Q

_____ (Lipid A/Lipoteichoic acid) on gram-positive cells and _____ (Lipid A/Lipoteichoic acid) on gram-positive cells induce TNF.

A

Lipoteichoic acid; lipid A (lipid A in bacteria lacking a gram-positive stain)—these also induce interleukin-1

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41
Q

What are the components of lipoteichoic acid?

A

It is a combination of lipids and teichoic acids

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42
Q

A 6-year-old has abdominal pain and intense vomiting. You suspect a gram-negative enteric bacteria. Name the 13 possibilities.

A

E. coli/Shigella/Salmonella/Yersinia/Klebsiella/Proteus/Enterobacter/Serratia/Vibrio/Campylobacter/Helicobacter/Pseudomonas

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43
Q

Name three intracellular bacteria that do not Gram stain well. Which lacks muramic acid in its cell wall? Which is seen with silver stain?

A

Rickettsia, Legionella, and Chlamydia; Chlamydia lacks muramic acid in its cell wall; Legionella pneumophila is seen on silver staining

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44
Q

What organisms can be visualized with a Ziehl-Neelsen stain? What is the main component of this stain?

A

Acid-fast bacteria (Nocardia, Mycobacterium); carbolfuchsin

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45
Q

A 10-year-old girl is diagnosed with whooping cough. How was the causative organism cultured?

A

Bordetella pertussis grows on Bordet-Gengou (potato) agar (Bordet for Bordetella)

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46
Q

Which aerobe is commonly associated with burn wounds, nosocomial pneumonia, and pneumonias in patients with cystic fibrosis?

A

Pseudomonas aeruginosa (P. aeruginosa is an aerobe)

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47
Q

A 56-year-old diabetic man has a foul-smelling foot ulcer with palpable crepitus. Which antibiotic should you not use to treat it? Why?

A

He has an anaerobic skin infection—aminoglycosides require oxygen to enter a bacterial cell and are therefore ineffective against anaerobes

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48
Q

A 20-year-old man recently had a splenectomy. Explain why he should receive S. pneumoniae, H. influenzae, and N. meningitis vaccines.

A

Encapsulated bacteria are opsonized then cleared by the spleen; asplenics have decreased opsonizing ability and are at risk for infection

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49
Q

Why does catalase make organisms more pathogenic?

A

Catalase degrades H2O2 before myeloperoxidase converts it to microbicidal products

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50
Q

Explain why a vaccine against a polysaccharide antigen alone would result in a weaker immune response.

A

Polysaccharide antigens alone would not be recognized/presented by T cells

51
Q

What protein from group A Streptococcus prevents phagocytosis by the body’s immune cells?

A

M protein

52
Q

Exotoxin genes are located in a(n) ____, whereas endotoxin genes are located in a(n) ____.

A

Plasmid or bacteriophage; bacterial chromosome

53
Q

A boy with pharyngitis has a pseudomembrane in his throat. What organism is likely responsible, and what is its toxin’s mechanism of action?

A

Corynebacterium diphtheriae; its toxin ADP ribosylates elongation factor 2 to inactivate it

54
Q

Endotoxins activate complement via C3a and C5a. ____ (C3a/C5a) causes hypotension/edema; ____ (C3a/C5a) triggers neutrophil chemotaxis.

A

C3a; C5a

55
Q

____, the ability to take up naked DNA from the environment, is a feature of many bacteria, especially which three bacteria?

A

Transformation (competence); shin = Streptococcus pneumoniae, Haemophilus influenzae, Neisseria

56
Q

Where is endotoxin (lipopolysaccharide) located in gram-negative bacteria? Which component serves as the antigen?

A

Outer membrane; O polysaccharide

57
Q

Many guests in a hotel with central air conditioning develop a high fever & pneumonia. What is the Gram stain/shape of the causative agent?

A

Legionella, a gram-negative bacillus

58
Q

What characteristic of Mycobacterium makes it visible with an acid-fast stain?

A

The high lipid content in the cell wall is detected by the carbolfuchsin in acid-fast stain (acid-fat [fast] stain)

59
Q

India ink and mucicarmine can be used to visualize what pathogen? What part of the organism does it stain? What color?

A

Cryptococcus neoformans; mucicarmine stains the thick polysaccharide capsule red

60
Q

An unimmunized 7-year-old has sore throat and fever. Exam reveals gray pseudomembranes in his throat. What type of culture must be done?

A

He likely has Corynebacterium diphtheriae, which grows on a tellurite plate with Löffler medium

61
Q

Exotoxins are composed of ____ (polypeptides/lipopolysaccharides), whereas endotoxins are made of____ (polypeptides/lipopolysaccharides).

A

Polypeptides; lipopolysaccharides (structural part of bacteria—released when lysed)

62
Q

A girl has rice-water diarrhea and is dehydrated. What organism is responsible, and what is its toxin’s mechanism of action?

A

Vibrio cholerae; AB toxin activates Gs protein and stimulates adenylate cyclase, which increases Cl¯ (therefore, water) secreted in gut

63
Q

Endotoxins activate the coagulation cascade via which factor? What pathology can result from excess stimulation of this pathway?

A

Tissue factor; disseminated intravascular coagulation

64
Q

In F+ to F¯ conjugation, ___ (chromosomes/plasmids/both) transfer ___ (to/from) the F+ cell through a ___. Are chromosomes transferred?

A

Plasmids; from; pilus; chromosomes are not transferred

65
Q

What is the chemical composition of the bacterial plasma membrane, and what are its two main functions?

A

It is made up of a phospholipid bilayer, and it functions as the site of oxidative and transport enzymes

66
Q

A 7-year-old girl has had a cough with whooping on inspiration for 2 months. What is the Gram stain/shape of the causative agent?

A

Bordetella pertussis, a gram-negative bacillus

67
Q

Why does Mycoplasma not Gram stain well?

A

It does not have a cell wall

68
Q

Silver stain is used to stain which organisms?

A

Fungi (e.g., Pneumocystis), Legionella, Helicobacter pylori

69
Q

A homeless man is febrile and coughing up blood. A cavitary lesion is seen on chest x-ray. How should you culture the causative organism?

A

He likely has Mycobacterium tuberculosis, which grows on Löwenstein-Jensen agar

70
Q

A febrile patient with septic shock has bacteria with poorly antigenic toxins in his blood. What two mediators caused this pathology?

A

Fever and shock due to induction of tumor necrosis factor and interleukin-1

71
Q

What are the mechanisms of the heat-labile and heat-stable toxins of enterotoxigenic E. coli (ETEC)?

A

Heat-labile overactivates adenylate cyclase (more Cl¯, H2O secretion); heat-stable activates guanylate cyclase (less NaCl, H2O resorption)

72
Q

Endotoxin activation of macrophages causes release of three cytokines. Name the cytokines. Do they cause fever, hypotension, or both?

A

Interleukin-1 causes fever; tumor necrosis factor causes fever and hypotension; nitric oxide causes hypotension

73
Q

Segments of DNA are transferred between ____ (chromosomes/plasmids/both) within the same cell in a process called ____.

A

Both; transposition

74
Q

Bacterial ribosomes synthesize ____ and consist of these two subunits

A

Proteins; 30S and 50S subunits

75
Q

A farmer develops fever, weakness, and muscle pain after drinking unpasteurized milk. What is the Gram stain/shape of the causative agent?

A

He likely has brucellosis; Brucella is a gram-negative bacillus

76
Q

Unlabeled bacterial colonies with a pink hue are noted to be acidic. What kind of bacteria are they? What medium was used to identify them?

A

Lactose-fermenting enterics; MacConkey agar; E. coli is also grown on eosin–methylene blue agar

77
Q

Which bacterial toxin (endotoxin or exotoxin) can be used as a vaccine? Against which antigen are antibodies formed?

A

Exotoxin toxoid is used as a vaccine against exotoxin-producing organisms; antibodies form against antigens called antitoxins

78
Q

A 10-year-old girl has 2 months of coughing fits, after which she fights to catch her breath. What is the mechanism of the offending toxin?

A

B. pertussis disables the Gi protein (overactivates adenylate cyclase), which impairs phagocytosis, allowing bacterial survival

79
Q

A(n) ____ cell incorporates a F+ plasmid into its own chromosomes. These cells transfer ____ (chromosomes/plasmids/both).

A

High-frequency recombination; both

80
Q

What is the periplasm, and what kinds of enzymes does it contain in its space?

A

Space between the cytoplasmic membrane and the outer membrane in gram negatives; contains hydrolytic enzymes (e.g., β-lactamases)

81
Q

A 40-year-old develops pain, redness, swelling at the site of a bite from her cat. What is the Gram stain/shape of the causative agent?

A

She likely has cellulitis caused by Pasteurella multocida, a common pathogen in cats; Pasteurella is a gram-negative bacillus

82
Q

Many guests in a hotel with central air conditioning develop a high fever and pneumonia. How will you culture the causative organism?

A

Legionella grows on charcoal yeast extract agar buffered with cysteine and iron

83
Q

____ (Endotoxins/Exotoxins) are heat stable; ____ (endotoxins/exotoxins) are not heat stable (except for ____ enterotoxins).

A

Endotoxins (stable at 100°C for 1 hour); exotoxins (destroyed rapidly at 60°C); staphylococcal

84
Q

The toxin tetanospasmin (Clostridium tetani) causes which symptoms by decreasing the level of which neurotransmitters? How?

A

Muscle rigidity, lockjaw; this toxin blocks release of inhibitory neurotransmitters (glycine, GABA) by cleaving SNARE protein

85
Q

Describe generalized transduction.

A

Lytic phage infects bacteria, cleaves bacterial DNA/makes viral DNA, and repackages bacterial DNA in viral capsids to infect other bacteria

86
Q

What is the typical composition of the bacterial capsule, and what is its main function?

A

Polysaccharides; protection from phagocytosis

87
Q

Francisella is a ____ (gram-positive/gram-negative) ____ (coccus/bacillus).

A

Gram-negative; bacillus

88
Q

Sabouraud agar is best for growing which pathogens?

A

Fungi

89
Q

____ (Endotoxin/Exotoxin) causes tetanus, botulism, diphtheria; gram-negative rod ____ (endotoxin/exotoxin) causes sepsis, meningococcemia.

A

Exotoxin; endotoxin

90
Q

A boy with a sweet tooth develops flaccid paralysis, mainly facial. What food did he likely ingest, and what is the disease mechanism?

A

Clostridium botulinum in honey (also canned foods); inhibits release of stimulatory Ach at neuromuscular junction by cleaving SNARE protein

91
Q

Describe specialized transduction.

A

Lysogenic phage infects bacteria, inserts viral DNA into chromosomes; viral (and bacterial) DNA excised into capsid infects other bacteria

92
Q

What is a plasmid, and what information does it carry?

A

A segment of bacterial DNA; contains genes for antibiotic resistance, enzymes, or toxin production

93
Q

Bartonella is a ____ (gram-positive/gram-negative) ____ (coccus/bacillus).

A

Gram-negative; bacillus

94
Q

In what medium can Mycoplasma pneumoniae grow?

A

Eaton agar, as it requires cholesterol

95
Q

Shigella and enterohemorrhagic E. coli (EHEC) release toxins causing GI mucosal damage and dysentery. Name the mechanism.

A

Both Shiga toxin and Shiga-like toxin cleave host cell rRNA, inactivating the 60S ribosomal subunit

96
Q

Chromosomal DNA is not transferred during ____ (transduction/F+ × F¯ conjugation/transposition)

A

F+ × F¯ conjugation

97
Q

A 56-year-old goat herder develops a painless black ulcer on his arm. What is special about the capsule of the causative agent?

A

Bacillus anthracis is the only bacterium with a capsule containing D-glutamate

98
Q

A young woman has excessive white foul-smelling vaginal discharge. You see clue cells on wet mount. Name the Gram stain/shape of the cause.

A

She likely has bacterial vaginosis caused by Gardnerella vaginalis, a gram-negative bacillus

99
Q

Two plates grow the same lactose-fermenting bacteria. One is pink, the other has a green metallic sheen. Identify the bacterium and the medium.

A

E. coli turns MacConkey agar pink, and it grows green metallic colonies on eosin–methylene blue agar

100
Q

At a cookout, a girl becomes ill. Labs show elevated levels of Shiga toxin. What is the disease, pathogen, and toxin mechanism of action?

A

Hemolytic-uremic syndrome (HUS); Shigella toxin; elevated cytokine release (Shiga-like toxin also causes HUS)

101
Q

During lysogeny, which is a ____ form of transduction, the genes for a bacterial toxin are encoded in a lysogenic ____.

A

Specialized; phage

102
Q

The glycoprotein-derived ____ allow bacterial adherence to host cells. A variant, the ____ ____, attaches two bacteria during conjugation.

A

Fimbria (pilus); sex pilus

103
Q

Which of the following is not an enteric bacillus: E. coli , Vibrio, Bordetella, Helicobacter, Serratia, Enterobacter?

A

Bordetella, which is a respiratory gram-negative bacillus

104
Q

56-year-old goat herder develops a painless black ulcer on his arm. What organism is responsible and what is the mechanism of its toxin?

A

Bacillus anthracis; edema factor toxin mimics adenylate cyclase enzyme (increases cAMP) and causes the edematous borders of black eschar

105
Q

Name five bacterial toxins coded for in a lysogenic phage.

A

ABCDE = shiga-like toxin, botulinum toxin, cholera toxin, diphtheria toxin, erythrogenic toxin of S. pyogenes)

106
Q

____ are bacterial structures that provide motility and are composed of protein.

A

Flagella

107
Q

Which of the following is not an enteric bacillus: Pasteurella, Shigella, Pseudomonas, Yersinia, Proteus, Bacteroides?

A

Pasteurella, which is a zoonotic gram-negative bacillus

108
Q

Certain bacteria, such as Corynebacterium diphtheriae, have ADP-ribosylating AB toxins. Name the function of the A and B components.

A

B component binds host cell surface receptor, enabling endocytosis; A component disrupts host cell proteins by attaching ADP-ribose moieties

109
Q

A 6-month-old infant accidentally eats honey. What bacterial infection is the pediatrician worried about? Why does it survive in honey?

A

Clostridium botulinum forms spores (dipicolinic acid with a keratin-like coat) that can survive dehydration, heat, and chemicals

110
Q

Name the two gram-positive, branching, filamentous bacteria. Which one can be identified with acid-fast staining?

A

Actinomyces and Nocardia—Nocardia, which is weakly acid fast

111
Q

The binding of superantigens to ____ and ____ receptors results in the widespread release of which two factors, ultimately causing what?

A

Major histocompatibility complex class II molecules; T-cell; release interferon-γ and interleukin-2, eventually causing shock

112
Q

A man has a catheter for a week and develops sepsis. Bacteria are found on the catheter. Which bacterial structure lets them adhere there?

A

Glycocalyx, made up of polysaccharide

113
Q

Name three types of spirochetes. Which can be identified via a Giemsa stain?

A

Leptospira, Borrelia (identifiable via Giemsa stain), and Treponema

114
Q

A patient has fever and rash and goes into shock. Name the two most likely causative bacteria and their associated toxins.

A

Staphylococcus aureus (toxic shock syndrome toxin [TSST-1]) and Streptococcus pyogenes (exotoxin A)

115
Q

Both ____ and ____ are highly pleomorphic gram-negative bacteria that are readily identified with ____ stain.

A

Rickettsiae and Chlamydiae; Giemsa

116
Q

A 16y/o with shock is admitted due to Staphylococcus aureus. Name the 3 toxins produced by this bug and the respective associated symptoms.

A

Toxic shock syndrome toxin (TSST-1)—fever, rash, and shock; exfoliative toxin—scalded skin syndrome; and enterotoxin—food poisoning

117
Q

A 24-year-old man has headache, cough, fever. Chest x-ray shows diffuse interstitial pneumonia; Gram stain is inconclusive. Likely cause?

A

Atypical pneumonia caused by Mycoplasma; this bacterium has no cell well and does not Gram stain

118
Q

A patient with scarlet fever has erythrogenic toxins in her blood. What is the pathogen and what is the name of the toxin?

A

Streptococcus pyogenes; exotoxin A, causing toxic shock syndrome (fever, rash, shock)

119
Q

A patient has a Haemophilus infection. Via what route was it likely acquired, and name an interesting trait of this particular bacterium.

A

Acquired via respiratory tract; it is pleomorphic

120
Q

A man recovering from trauma has a foul-smelling necrotic skin lesion; crepitus is noted. How does the infecting agent appear on blood agar?

A

Clostridium perfringens α-toxin forms a double zone of hemolysis on blood agar

121
Q

A man presents with a new heart murmur after recent streptococcal pharyngitis infection. Name his diagnosis and the diagnostic test.

A

Rheumatic fever; presence of anti–streptolysin O antibodies

122
Q

A man recovering from trauma has a foul-smelling, necrotic skin lesion, crepitus. Explain the mechanism of action of the causative toxin.

A

Clostridium perfringens α-toxin is a phospholipase; degrades phospholipid C, causing tissue and cell membrane necrosis (myonecrosis)

123
Q

A toddler presents with impetigo. Tests confirm Streptococcus pyogenes. Name the offending toxin and explain its mechanism.

A

Streptolysin O degrades cell membranes and lyses RBCs, contributing to β-hemolysis

microbiology (2 decks)

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