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400621 Lecture Notes - Lecture 2: Respiratory Tract, Methicillin, Oxacillin

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School
UWS
Department
University of Western Sydney
Course
400621
Professor
mark jones

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Document Summary

Methicillin-resistant staphylococcus aureus (mrsa) refers to a group of gram-positive bacteria that are genetically distinct from other strains of staphylococcus aureus. Mrsa is responsible for several difficult-to-treat infections in humans. Mrsa is any strain of s. aureus that has developed, through horizontal gene transfer and natural selection, multi drug resistance to beta-lactam antibiotics. Lactam antibiotics are a broad-spectrum group that include some penams penicillin derivatives such as methicillin and oxacillin and cephems such as the cephalosporins . In humans, staphylococcus aureus is part of the normal microbiota present in the upper respiratory tract, and on skin and in the gut mucosa. S. aureus, along with similar bacterial species that can colonize and act symbiotically but can cause disease if they begin to take over the tissues they have colonized or invade other tissues, has been called a pathobiont. After 72 hours, mrsa can take hold in human tissues and eventually become resistant to treatment.

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Related Questions

1) What clinical manifestation do Staphylococcus aureus and Staphylococcus epidermidis share? A) nosocomial infections B) protein A antiphagocytic factor C) hyaluronidase enzyme D) enterotoxins E) staphylokinase 2) Which of the following has been historically classified as Gram-negative bacteria but is genetically more similar to low G + C Gram-positive bacteria? A) mycoplasmas B) Mycobacterium C) Clostridium D) Propionibacterium E) Nocardia 3) What is one virulence factor that differentiates Staphylococcus aureus from other species of staphylococci? A) It has a capsule. B) It can produce coagulase. C) It produces catalase. D) It can live on the surface of the skin and in cutaneous oil glands. E) It produces lipase. 4) Over 90% of Staphylococcus aureus isolates are penicillin-resistant. Why? A) They have loosely organized polysaccharide slime layers. B) They produce coagulase. C) Cell division occurs in successively different planes, and the daughter cells remain attached to one another. D) They produce β-lactamase. E) They produce staphylokinase, which dissolves fibrin threads in blood clots. 5) A woman comes to the emergency department with fever and vomiting. She soon develops a red rash all over her body, and her blood pressure begins to drop. What is one possible diagnosis? A) erysipelas C) scarlet fever B) endocarditis D) toxic shock syndrome E) staphylococcal food poisoning 6) Bacteria collected from a severely inflamed wound are sent to the lab for analysis. The results come back as follows: Gram-positive cocci in irregular clusters, kinase and coagulase positive, and able to grow in the presence of most antibiotics except vancomycin. The bacteria in the wound are most likely _______ A) Enterococcus. C) Staphylococcus aureus. B) Staphylococcus epidermidis. D) methicillin-resistant Staphylococcus aureus (MRSA). E) Streptococcus pyogenes (group A streptococcus). 7) Which of the following statements about "flesh-eating" streptococci is FALSE? A) It is caused by a group A streptococcus. B) It is also known as necrotizing fasciitis because it travels along the fascia. C) It causes death in over 50% of cases. D) It is considered a common complication of pyoderma. E) It involves toxemia. 8) Streptococcus agalactiae is associated with which of the following diseases? A) neonatal bacteremia B) neonatal meningitis C) neonatal pneumonia D) both neonatal bacteremia and neonatal meningitis E) neonatal bacteremia, neonatal meningitis, and neonatal pneumonia 9) What differentiates virulent strains of Streptococcus pneumoniae from nonvirulent strains? A) the species-specific teichoic acid present in its cell wall B) the type of Lancefield antigen it produces C) the presence of a polysaccharide capsule that protects it from digestion after endocytosis D) the type of toxins it produces E) the extent of the hemolytic zone it produces when it is grown on blood agar 10) Otitis media may lead to dangerous meningitis in children due to infection with _____ A) Streptococcus agalactiae. B) Streptococcus pneumoniae. C) Streptococcus mutans. D) Enterococcus. E) Mycoplasma pneumoniae. 11) Which of the following streptococci is associated with dental caries? A) viridans streptococci B) Streptococcus pyogenes C) Streptococcus pneumoniae D) Streptococcus equisimilis E) Streptococcus arginosus 12) Anthrax, which means "charcoal" in Greek, derives its name from _____ A) the airborne endospores it produces. B) the staining properties of the bacillus under the microscope. C) the black eschars it produces on human skin. D) its ability to invade the bloodstream and produce toxemia. E) the high mortality it causes in infected individuals. 13) Which of the following bacteria produce one of the most deadly bacterial toxins known? A) Clostridium perfringens C) Clostridium tetani B) Clostridium difficile D) Clostridium botulinum E) Corynebacterium species 14) Which of the following bacteria can cause life-threatening pseudomembranous colitis? A) Clostridium difficile B) Staphylococcus aureus C) Streptococcus pyogenes D) Enterococcus species E) Clostridium botulinum 15) How does the toxin from Clostridium tetani produce its action? A) It fuses irreversibly to neuronal cytoplasmic membranes, blocking release of acetylcholine at synaptic clefts. B) The smaller polypeptide of its toxin can block the release of inhibitory neurotransmitters by inhibitory neurons in the central nervous system, causing simultaneous contraction of both muscles in an antagonistic pair. C) It is a pyrogenic toxin, which triggers a diffused rash and, later, sloughing of skin. D) It destroys tissues, including muscle and fat. E) It produces antibodies that attack the neuromuscular junctions in skeletal muscle and prevent them from relaxing. 16) Listeria virulence is directly related to its ability to ______ A) produce powerful toxins. B) form very resistant endospores. C) live within cells and thus avoid exposure to the immune system of its host. D) easily become a pathogen in humans. E) resist most antimicrobial agents. 17) The pus from an abscess in a patient's jaw contains microbes that form yellowish grainy masses and appear filamentous under the microscope. Neither antifungal medication nor a normal course of antibiotics has been effective in treating the infection. The abscess is likely the result of infection with A) Actinomyces. B) Mycobacterium. C) Nocardia. D) Propionibacterium. E) Streptococcus. 18) What is the most common disease caused by Propionibacterium? A) acne B) food poisoning C) pneumonitis D) folliculitis 19) Streptococcus pneumoniae is a leading cause of ______ A) acne. C) pharyngitis B) furuncles. D) primary atypical pneumonia. E) otitis media. 20) The soil bacterium Nocardia asteroides can establish opportunistic infections of the _____ A) skin C) central nervous system B) lungs D) cardiovascular system. E) skin, lungs, and central nervous system

The most commonly isolated gram-positive cocci are best differentiated by their:

Gram stain morphology.

catalase reaction.

hemolytic reaction.

both a and b.

both b and c.

ANSWER:

(Level 1, Objective 1)

The novobiocin resistance test is used to

determine treatment options for Staphylococcus saprophyticus.

identify S. saprophyticus.

differentiate S. saprophyticus and S. hominis ssp. novobiosepticus.

both a and b.

ANSWER:

(Level 1, Objective 2)

The slide coagulase and the Staphylococcus latex agglutination tests are similar in that both test for the presence of

protein A.

free coagulase.

clumping factor.

thermonuclease.

ANSWER:

(Level 2, Objective 2)

The esculin/PYR disk test can be used to rapidly identify

Enterococcus spp.

Streptococcus pneumoniae.

Streptococcus pyogenes.

both a and b.

both a and c.

ANSWER:

(Level 1, Objective 2)

The optochin disk test is incubated at/in _____________________.

35°C, ambient air.

35°C, CO2.

42°C, CO2.

25°C, a capnophilic atmosphere.

ANSWER:

(Level 1, Objective 2)

A catalase-positive, gram-positive coccus that agglutinates in a slide coagulase test as well as in saline should be

reported as Staphylococcus aureus.

reported as Staphylococcus not S. aureus.

retested using another method.

retested for the catalase reaction.

ANSWER:

(Level 2, Objectives 2 and 3)

A positive rapid esculin test appears

dark.

pink.

red after the addition of the reagent.

blue.

ANSWER:

(Level 1, Objective 3)

Yellow colonies on mannitol salt agar indicate the definitive presence of

methicillin-resistant Staphylococcus aureus.

Staphylococcus aureus.

Staphylococcus not S. aureus.

unable to definitively identify.

ANSWER:

(Level 2, Objective 4)

A catalase-negative, gram-positive coccus that is bile esculin positive and 6.5% NaCl broth positive belongs to the Lancefield antigenic group

D.

C.

B.

A.

ANSWER:

(Level 2, Objective 5)

10. A leg wound isolate presents as a yellow pigmented, beta-hemolytic, catalase-positive, gram-positive cocci in clusters. Which of the following tests would you expect to be positive for this isolate?

Novobiocin resistance

Heat-stable thermonuclease

PYR

b and c

a and b

ANSWER:

(Level 2, Objective 5)

11. A catalase-negative coccus in pairs and short chains that is susceptible to ethyl hydrocupreine will also

a. require CO2 for growth.

b. be alpha hemolytic.

c. be bile soluble.

d. all of the above.

e. b and c.

ANSWER:

(Level 2, Objective 5)

12. The PBP2a latex agglutination test is used to detect catalase-positive, coagulase-positive, gram-positive cocci that are resistant to

a. vancomycin.

b. novobiocin.

c. oxacillin.

d. penicillin.

ANSWER:

(Level 2, Objective 6)

13. A catalase-negative, gram-positive coccus in chains that is positive for esculin and PYR hydrolysis is also vancomycin resistant. What additional antibiotic resistance can this organism exhibit?

a. high level aminoglycosides.

b. ampicillin and penicillin.

c. beta-lactamase production.

d. all of the above.

e. b and c.

ANSWER:

(Level 2, Objective 6)

14. An alpha-hemolytic, catalase-negative, gram-positive coccus that is susceptible to optochin can cause all of the following diseases except

a. pneumonia.

b. sinusitis.

c. meningitis.

d. pharyngitis.

ANSWER:

(Level 2, Objective 7)

15. The catalase-negative, gram-positive coccus that is the most common cause of neonatal sepsis and meningitis

a. has the potential to be vancomycin resistant.

b. hydrolyzes hippurate.

c. is susceptible to bacitracin.

d. is bile soluble.

ANSWER:

(Level 2, Objective 7)

16. Necrotizing fasciitis is caused by a

a. catalase-negative, gram-positive coccus that is susceptible to bacitracin.

b. catalase-negative, gram-positive coccus that produces CAMP factor.

c. catalase-positive, gram-positive coccus that produces coagulase.

d. catalase-positive, gram-positive coccus that is resistant to novobiocin.

ANSWER:

(Level 2, Objective 7)

17. Infections of indwelling devices, such as intravenous catheters, are often caused by catalase-positive, gram-positive cocci that are

a. coagulase positive and thermonuclease negative.

b. coagulase negative and novobiocin resistant.

c. caogulase positive and thermonuclease positive.

d. coagulase negative and novobiocin susceptible.

ANSWER:

(Level 2, Objective 7)

18. Which of the following factors accounts for the virulence of Streptococcus pyogenes?

a. “C” substance

b. Protein A

c. M protein

d. mecA gene

ANSWER:

(Level 1, Objective 7)

19. The virulence factor most often associated with catalase-negative, gram-positive cocci that are bile soluble is

a. capsule production.

b. vancomycin resistance.

c. hyaluronidase.

d. streptolysin S.

ANSWER:

(Level 2, Objective 7)

20. A catalase-negative, alpha-hemolytic, gram-positive coccus that is resistant to ethyl hydrocupriene is usually considered

a. a member of the normal upper respiratory flora.

b. a pathogen in an expectorated sputum specimen.

c. the causative agent of non-suppurative sequelae.

d. a common urinary pathogen.

ANSWER:

(Level 2, Objective 8)

21. A catalase-positive, coagulase-negative, gram-positive coccus in clusters is isolated from the urine of a 24-year-old female. This isolate will require

a. additional testing to identify.

b. no further testing.

c. a screen for vancomycin resistance.

d. Lancefield grouping.

ANSWER:

(Level 2, Objective 10)

22. A blood culture yields yellow-pigmented, beta-hemolytic, catalase-positive, gram-positive cocci in clusters. The department is out of Staphylococcus latex agglutination reagent. The microbiologist sets up a tube coagulase and mannitol salt agar. She incubates both at 35°C in CO2 overnight. The next day the coagulase test is negative and the mannitol salt agar displays yellow colonies. How will you proceed with these results?

a. Report this organism as Staphylococcus aureus

b. Report this organism as Staphylococcus not S. aureus

c. Repeat the tests due to invalid results

d. Test the organism for novobiocin resistance

ANSWER:

(Level 3, Objective 10)

24. A patient, suspected to have bacterial endocarditis, had two sets of blood cultures drawn. All four bottles are positive with gram-positive cocci in pairs and chains. On sheep blood agar, the gray, transparent, alpha-hemolytic colonies are catalase negative, optochin resistant, ESC negative and PYR negative. Which of the following patient histories correlates with the presence of this organism?

a. 78-year-old male with bacterial pneumonia

b. 47-year-old female with a heart murmur and a history of dental surgery

c. 16-year-old female with a history of untreated pharyngitis

d. 3-day-old premature male

ANSWER:

(Level 3, Objective 10)

25. A translucent colony displaying subtle beta hemolysis is isolated from a placenta culture. The Gram stain revealed gram-positive cocci in pairs. The microbiologist drops 3% catalase reagent onto a colony on sheep blood agar, and it produces bubbles. He then performs a Staphyloccocus latex agglutination and the suspension remains smooth. The next step is to

a. report the organism as Staphylococcus not S. aureus.

b. report the organism as Staphylococcus aureus.

c. repeat the catalase test due to an invalid result.

d. perform a thermonuclease test due to an invalid latex agglutination result.

ANSWER:

(Level 3, Objective 10)


Class 6: Viruses (and Cells, continued)


Making connections: viruses and microbes Match the cell biology concept (on page 1) with an important application of that concept (on page 2). Then answer the follow-up questions at the bottom of page 2.


Cell Biology concepts
1. Bacteria that cannot construct new cell wall material become fragile and break down.
2. During influenza infection, the viral enzyme neuraminidase is required to release new viruses from the host cell in which they were made. Once released, the new viruses can infect many additional cells.
3. Thermus aquaticus is a bacterium found in hot springs and can live at temperatures up to ~80°C (175°F). It has adapted so that its enzymes are most functional at the elevated temperatures, compared with many organisms’ enzymes that function best ~37°C (98°F).
4. Until the isolation and investigation of retroviruses, scientists thought that RNA could be copied from DNA, but DNA could not be copied from RNA. Research on this class of viruses led to an update to this “Central Dogma” of biology.
5. Some bacteria have adapted, so that the enzymes involved in making cell wall materials have a slightly different shape and can no longer be bound by certain drugs.
6. Rhizobia are bacteria that colonize the roots of certain plants (legumes, including beans and peas). The host plant benefits from the prokaryotes’ ability to “fix” nitrogen, converting N2 from the atmosphere into a form that is usable by the plant.
7. Many species of bacteria contain the enzyme cellulase. More than 10 billion such bacteria and other symbiotic microbes may be found in a single milliliter of material from inside the digestive system of ruminant mammals.
8. Fungi, including those that cause athlete’s foot, use ergosterol to maintain healthy membranes. Animal cells do not make ergosterol, they use a similar lipid – cholesterol.
9. During retrovirus infection, a DNA copy is made of the virus’s RNA genome. A cut is made in the host cell’s DNA and the DNA copy of the viral genome is pasted into the host chromosome by a viral enzyme called integrase.
10. Prokaryotic cells contain smaller ribosomes (“70S” ribosomes) than eukaryotic cells (“80S” ribosomes). Both types of ribosomes synthesize proteins, but the macromolecules they use to do it are somewhat different.



2
Applications
_______ Oseltamivir, also called Tamiflu, binds and inhibits the viral protein neuraminidase.
_______ Clotrimazole is a drug that is used to treat certain infections. It interferes with synthesis of ergosterol, a lipid involved in phospholipid membranes.
_______ Penicillin is a drug that interferes with synthesis of peptidoglycans (these are biological molecules that are part protein and part carbohydrate) that are present in certain cell walls.
_______ HIV is often treated with several drugs that inhibit different parts of the viral replicative cycle. Raltegravir is an example of a drug that interferes with the integration of viral genes into the host cell’s chromosome.
_______ Cows, like other vertebrates, lack the ability to breakdown cellulose. Yet they are able to live on a diet of grass and other vegetation high in cellulose.
_______ Enzymes isolated from extremophiles have been very useful in laboratory research. For example, Taq polymerase facilitates PCR, a revolutionary technique for production of DNAs of particular sequences, which requires cycling reactions through high temperatures.
_______ Plants and animals require nitrogen to make biological macromolecules, however they’re unable to convert atmospheric nitrogen (N2) into a biologically useful form.
_______ Azithromycin is a drug that binds to 70S ribosomes and blocks synthesis of any new proteins.
_______ Methicillin-Resistant Staphylococcus aureus (MRSA) can cause life-threatening infections of the skin and bloodstream. One of the reasons MRSA infections are so serious is that they are resistant to treatment by many antibiotics, including methicillin and penicillin.
_______ The enzyme reverse transcriptase, isolated from retroviruses, is an important tool in molecular biology research. Scientists interested in learning what genes are turned on in particular cells use it to make DNA copies of RNAs they are studying (The DNA copies are useful because they are more stable).


When you have completed the matching activity, answer these follow-up questions:
• What types of infections can be treated with the following drugs?
o Penicillin
o Clotrimazole
o Azithromycin
o Tamiflu
o Raltegravir
• Why are these drugs (above) safe for you to take? That is, why don’t they kill your cells?
• Cancer cells are your own human cells that have become deregulated so that they divide and pile up in an uncontrolled way. Many chemotherapy drugs treat cancer by interfering with cell division and other cell processes.
o Why are there so many more side effects for individuals undergoing chemotherapy than for individuals taking antibiotics?