LE 3 - Micro Flashcards
- Which of the following structures do not contribute to the virulence of N. gonorrhea?
a. Lipooligosaccharide
b. IgA protease
c. Pili
d. Axial filaments
d. Axial filaments
Axial filaments are associated with spirochete bacteria like Treponema pallidum, which causes syphilis, not with Neisseria gonorrhoeae. The other structures listed (Lipooligosaccharide, IgA protease, and Pili) all contribute to the virulence of N. gonorrhoeae.
One of the following conditions is not caused by S. aureus. Which one?
a. Cellulitis
b. Impetigo
c. Scarlet fever
d. Toxic shock syndrome
c. Scarlet fever (S.pyogenes)
Scarlet fever is caused by Streptococcus pyogenes (Group A Streptococcus). The other conditions (Cellulitis, Impetigo, and Toxic shock syndrome) can be caused by Staphylococcus aureus.
The most common etiologic agent of pneumonitis with microabscesses is
a. Streptococcus pneumoniae
b. Mycoplasma pneumonia
c. Staphylococcus aureus
d. Klebsiella pneumonia
c. Staphylococcus aureus
Staphylococcus aureus is commonly associated with pneumonitis characterized by microabscesses.
The following are superantigens of S. aureus, except
a. Coagulase
b. Enterotoxin
c. TSST-1
d. Exfoliative toxin
a. Coagulase
Examples of superantigens include:
1. Toxic Shock Syndrome Toxin-1 (TSST-1) produced by Staphylococcus aureus. 2. Staphylococcal enterotoxins (SEs) produced by Staphylococcus aureus. 3. Streptococcal pyrogenic exotoxins (SPEs) produced by Streptococcus pyogenes.
Which of the following is the most common cause of UTI in females?
a. Staphylococcus aureus
b. Escherichia coli
c. Staphylococcus saprophyticus
d. Klebsiella pneumonia
c. Staphylococcus saprophyticus
A quick laboratory test that differentiates Staphylococcus from Streptococcus is
a. Optochin test
b. Coagulase test
c. Catalase test
d. Hemolysis
c. Catalase test
Rationale:
- Optochin test: Used primarily to differentiate Streptococcus pneumoniae (sensitive) from other viridans streptococci (resistant).
- Coagulase test: Identifies Staphylococcus aureus by its ability to clot plasma. Not used to differentiate between the genera Staphylococcus and Streptococcus.
- Catalase test: The key test to differentiate Staphylococcus (catalase-positive) from Streptococcus (catalase-negative).
- Hemolysis: Refers to the lysis of red blood cells on blood agar. Both Staphylococcus and Streptococcus species can show different patterns of hemolysis, so it’s not definitive for differentiating between the two genera.
Most common cause of septic arthritis:
a. S. aureus
b. N. gonorrhea
c. S. pyogenes
d. S. epidermidis
a. S. aureus
Keywords:
• S. aureus: Most common, all age groups • N. gonorrhea: Sexually active, young adults • S. pyogenes: Less common cause • S. epidermidis: Prosthetic joint infections
The principal habitat of N. meningitidis in carriers is:
a. Meninges
b. Nasopharynx
c. Lungs
d. Nasal mucosa
b. Nasopharynx
The most common cause of bacterial meningitis in the newborn:
a. N. meningitidis
b. E. coli
c. S. pneumonia
d. S. aureus
b. E. coli
A 25-yo sexually active female students presents with dysuria and purulent vaginal discharge a week after having unprotected sex with a former highschool classmate during a reunion. What is the most sensitive diagnostic method for determining the most likely etiologic agent?
a. Gram stain
b. Bacterial culture on selective media
c. Nucleic acid amplification test
d. serology
c. Nucleic acid amplification test
Nucleic acid amplification tests (NAATs) are highly sensitive and specific for detecting sexually transmitted infections, including those causing symptoms like dysuria and purulent vaginal discharge. This method can help identify the most likely etiologic agent, such as Chlamydia trachomatis or Neisseria gonorrhoeae, in a case like this.
A notorious actor presented with septic arthritis which he experienced repeatedly during the last few years. Knee fluid aspirate culture on chocolate agar was positive for N. gonorrhea. The patient should be evaluated for?
a. A polymorphonuclear cell chemotactic factor
b. Myeloperoxidase deficiency
c. Selective IgA deficiency
d. Deficiency of a late acting complement C5, C6, C7, C8
d. Deficiency of a late acting complement C5, C6, C7, C8
A 40 y/o carpenter was diagnosed to have osteomyelitis. He underwent surgery where bone debridement and drainage of pus was done. Culture yielded S. aureus. Based on this information, you know the organism is:
a. beta lactamase
b. susceptible to nafcillin
c. encapsulated
d. catalase positive
d. Catalase positive
Staphylococcus aureus is catalase positive, which means it produces the enzyme catalase, allowing it to convert hydrogen peroxide into water and oxygen. This characteristic is used in the laboratory to help differentiate it from other bacteria.
A 25 year old housewife was diagnosed to have a tubo-ovarian abscess after consulting at the OPD of a hospital. She presented with moderately high grade fever accompanied by left lower quadrant pain and tenderness upon palpation of her uterus. History is positive for unprotected sex. Secretions from her endocervix yielded gonorrhoeae. What might be the common sequelae of the condition.
a. infertility
b. cervical ca
c. urethral stricture
d. uterine fibroid tumor
a. Infertility
Tubo-ovarian abscesses can lead to damage and scarring of the fallopian tubes and ovaries, which can result in infertility due to impaired function of these reproductive organs. It’s essential for the patient to receive prompt treatment to minimize the risk of long-term complications like infertility.
Antimicrobial resistance has become a significant problem. Which one of the following is of major concern worldwide regarding resistance?
a. Penicillin in N. gonorrhea
b. Penicillin in S. pneumonia
c. Nafcillin in S. aureus
d. Vancomycin in S. aureus
d. Vancomycin in S. aureus
Coagulase is not thought to be an important virulence factor of Staphylococcus aureus.
a. TRUE
b. FALSE
b. FALSE
Coagulase is considered an important virulence factor of Staphylococcus aureus. It allows the bacteria to clot plasma, which can help protect the bacteria from phagocytosis and the immune system. Coagulase-positive strains of Staphylococcus aureus are typically more virulent than coagulase-negative strains.
Staphylococcus have positive catalase tests.
a. TRUE
b. FALSE
a. TRUE
S. epidermidis does not have coagulase.
a. TRUE
b. FALSE
a. TRUE
Staphylococcus aureus causes Toxic shock syndrome because of its enterotoxins which are heat stable and resistant to gut enzymes.
a. TRUE
b. FALSE
b. FALSE
While Staphylococcus aureus does produce enterotoxins, it is the Toxic Shock Syndrome Toxin-1 (TSST-1) that is primarily responsible for causing Toxic Shock Syndrome (TSS). TSST-1 is a superantigen, not an enterotoxin. The enterotoxins produced by Staphylococcus aureus are associated with food poisoning due to their heat stability and resistance to gut enzymes, but they are not the primary cause of TSS.
Neisseria species are best identified with coagulase tests.
a. TRUE
b. FALSE
b. FALSE
A 40 y/o carpenter was diagnosed to have osteomyelitis. He underwent surgery where bone debridement and drainage of pus was done. Culture yielded S. aureus. Based on this information, you know the organism is:
a. catalase positive
b. Beta-lactamase negative
c. Coagulase negative
d. Oxidase positive
a. catalase positive
- Which of the following characteristics differentiates S. aureus from the non-pathogenic species of staphylococcus?
a. Pigment production
b. Catalase positive
c. Coagulase positive
d. All of the choices are correct
c. Coagulase positive
Staphylococcus aureus is coagulase positive, which means it produces the enzyme coagulase that can cause the blood to clot. This is a key distinguishing feature of S. aureus compared to other Staphylococcus species, and it is often used in the laboratory to differentiate pathogenic S. aureus from non-pathogenic Staphylococcus species. Pigment production (choice a) and catalase positivity (choice b) are not unique to S. aureus and can also be found in other Staphylococcus species.
Characteristics of Streptococcus pneumoniae
a. Not inhibited by optochin on solid media
b. Gram positive diplococci
c. Arranged in clusters
d. Autolysis is decreased by surface acting agents
b. Gram positive diplococci
There are many diseases attributable to invasion of S.pyogenes. What is the most serious sequelae of S.pyogenes infection?
a. Sub Acute nasopharyngitis
b. Acute Glomerulonephritis
c. Rheumatic Fever
d. Streptococcal pyoderma
c. Rheumatic Fever
Considered to be the drug of choice for Streptococcus pneumoniae
a. Penicillin G
b. Vancomycin
c. Erythromycin
d. Tetracycline
a. Penicillin G
Rheumatic fever is most commonly caused by
a. Streptococcus viridans
b. Streptococcus pyogenes
c. Staph aureus
d. Strep pneumoniae
b. Streptococcus pyogenes
Penicillin is drug of choice of
a. Scarlet fever
b. Whooping cough
c. brucellosis
d. syphillis
d. Syphilis
Penicillin has long been the primary treatment for syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum. It is highly effective in treating and curing syphilis at various stages of the disease. The other conditions listed have different preferred treatments.
Virulence factor for streptococcus pneumoniae
a. Capsular polysaccharide
b. Vi antigen
c. Specific soluble substance
d. F antigen
a. Capsular polysaccharide
- Conjunctivitis in a newborn is caused by
a. streptococcus
b. meningococci
c. pneumococcus
d. E coli
a. streptococcus
- Thayer Martin agar contains antibiotics which make it a selective medium for
A. Staphylococcus aureus
B. Streptococcus pyogenes
C. Neisseriae gonorrhea
D. Esheichia coli
C. Neisseriae gonorrhea
- Drug of choice for Streptococcus pneumoniae
A. Erythromycin
B. Penicillin G
C. Vancomycin
D. Cefotaxime
B. Penicillin G
- This disease usually follows an acute infection and is commonly preceded by skin infection.
A.Streptococcal shock syndrome
B. Rheumatic fever
C. Scarlet fever
D.Glomerulonephritis
D. Glomerulonephritis
Specifically, post-streptococcal glomerulonephritis can develop after an infection with certain strains of streptococcus bacteria, often following a throat or skin infection (like impetigo).
- A 28 year old nurse was brought to the ER because of hypotension, headache, muscle ache, abdominal cramps, and diarrhea. PE revealed the presence of an erythematous rash and an intact tampon as she was menstruating at that time. Her kidney function test were normal indicative of mild renal failure. Her illness is likely to be caused by which of the following?
A. a toxin that degrades sphingomyelin
B. a toxin that blocks elongation factor (EF2)
C. a toxin that results in greatly increased levels of intracellular CAMP
D. a toxin that stimulates up to 10% T cells to be non-specifically activated
D. a toxin that stimulates up to 10% T cells to be non-specifically activated
- A quick laboratory test that differentiates Staphylococcus from Streptococcus is
A. Catalase test
B. Coagulase test
C. Hemolysis
D. Optochin test
A. Catalase test
- This organism produces dextrans and levans from sucrose contributing to dental caries formation
A. Streptococcus N
B. Streptococcus C and G
C. Streptococcus angionosus
D. Streptococcus mutans
D. Streptococcus mutans
- One of the following conditions is not caused by S. aureus. Which one?
A. Cellulitis
B. Toxic shock syndrome
C. Scarlet fever
D. Impetigo
C. Scarlet fever
- Produces dome shaped colonies later forming a central plateau with an elevated rim
A. Streptococcus N
B. Streptococcus bovis
C. Viridans streptococcus
D. Streptococcus pneumoniae
D. Streptococcus pneumoniae
10 . A notorious actor presented with septic arthritis which he rexperienced repeatedly during the last few years. Knee fluid aspirate culture on chocolate agar was positive for N. gonorrhea. The patient should be evaluated for?
A. A polymorphonuclear cell chemotactic factor
B. Myeloperoxidase deficiency
C. Selective IgA deficiency
D. Deficiency of a late acting complement C5, C6, C7, C8
D. Deficiency of a late acting complement C5, C6, C7, C8
- This is the component of diptheria toxin responsible for the arrest of protein synthesis producing the necrotizing and neurotoxic effects
a. fragment b
b fragment c
c fragmend d
d fragment a
d fragment a
- Non- enterococcal group D streptococci and part of the enteric flora
a. streptococcus bovis
b non of the choices are correct
c. streptococcus group c and d
d strepotococcus agalactiae
a. streptococcus bovis
Streptococcus bovis is a non-enterococcal group D streptococcus and is part of the enteric (intestinal) flora.
- Most prevalent members of normal flora of the upper respiratory tract and is important for the mucus memebrane
A. Streptococcus C and G
B. Viridans Streptococcus
C. Streptococcus milleri
D. Streptococcus N
B. Viridans Streptococcus
14.Diagnostic laboratory test used to identify C. diphtheriae
a. none of the above
b. blood agar
c. dacron swabs
d. Thayer martin agar
b. blood agar
- what antigenic structure of S. aureus important to bacterial attachment to host cells has become an important reagent in immunology (coaglutinnation)
a. peptidoglycan
b. polysaccharide capsule
c. Protein A
d. teichoic acid
c. Protein A