exam 3
Based on its Gram status, why are penicillin and other beta-lactam antibiotics effective against Streptococcus pneumoniae?
Beta lactam antibiotics are effective against Streptococcus pneumoniae because it is a Gram positive organism and does not have an outer membrane.
for a peptide comprised of the amino acids leucine-threonine, the corresponding anticodons are GAC, UGA, UGC respectively. the codons are therefore___
CUG,ACU,ACG
____ are the primary means by which Neisseria gonorrhoeae attaches to the mucous membranes of the reproductive tract.
Fimbriae
Helicobacter pylori can survive in the acidic environment of the stomach but is actually considered to be a neutrophile. How can this be?
Helicobacter pylori can survive in the acidic environment of the stomach because it can neutralize the pH in the local area of infection.
Streptococcus pneumoniae is found as part of the normal microbiota of the mouth and pharynx and yet can cause disease in some people when it is inhaled into lungs. Why do you think this is
If Streptococcus pneumoniae is inhaled from the nasopharynx into lungs damaged by a previous viral infection or in an immune compromised person, it can flourish.
In STD chlamydioses this is least related to infections
arthropod vector
A genetic mutation causing valine, an amino acid, to be replaced with glutamic acid, is a __ event.
base-pair substitution
a genetic mutation causing valine, an amino acid, to be replaced with glutamic acid, is a ___ event
base-pair substitution
Helicobacter pylori resists phagocyte activity due to its production of which of the following?
catalase
Salmonella typhi
causes diarrhea, fever and possible septicemia.
Disease research and epidemiology bring together many different facets to help us better understand disease pathology and spread. Which of the following statements are true?
*The interactions that occur between a microbe and host influence the evolution of both. *Bacterial exotoxins can be altered to create toxoids, which can be used to produce protective immunity in a host. *Some pathogens are able to cause disease within a host without penetrating the body.
The ability of Vibrio cholerae to cause disease depends on a number of factors. Which of the following are general requirements for any organism to cause disease within a host?
*adherence to host tissues *Evasion of host defenses *gaining access to the host via a portal of entry
Cephalosporins
*inhibit cell wall synthesis *are resistant against penicillinase producing bacteria *have a b-lactam ring
Treponema pallidum is a spirochete. How does this morphology contribute to the pathogenesis of this organism?
Spirochetes like Treponema pallidum have a tightly coiled, helical morphology, which allows them to move by rotation and burrow into tissues.
Some studies have indicated that the ID50 for Vibrio cholerae can be as high as 108 organisms. Which of the following most likely explains the requirement for this relatively high ID50?
To establish infection, V. cholerae must survive the host immune response and the acidic environment of the stomac
Which of the following symptoms is LEAST characteristic of Clostridium perfringens food poisoning?
moderate vomiting and fever
Tetracycline
*inhibits protein synthesis *is a broad spectrum antibiotic
the genetic code for a single amino acid consists of
3 nucleotides
In which of the following cases would you suspect wound botulism?
A person injures herself while gardening. Four days later she begins to feel weak and dizzy, with blurred vision and progressive paralysis.
Rickettsia rickettsii is a gram-negative, obligate intracellular pathogen. Which of the following statements about the R. rickettsii life cycle is FALSE?
After entering a host, R. rickettsii multiplies to levels high enough to successfully invade cells and establish an infection.
Although cholera can be treated with antibiotics, data suggest that antibiotic treatment alone is NOT the most effective therapy. Which of the following statements describes the most likely reason for supplementing antibiotic therapy?
Antibiotic therapy addresses only the growth of V. cholerae; it doesn't address the extreme dehydration suffered by a person infected with V. cholerae.
Who do you think would be more likely NOT to recognize the symptoms of gonorrhea: a man or a woman? Why?
Because of her particular anatomy, the normal discharge associated with the female reproductive tract, plus the fact that more women are asymptomatic for gonorrhea, a woman would be less likely to recognize the symptoms as being gonorrhea and seek treatment.
All of the following are directly involved in translation except?
DNA
The name Propionibacterium is derived from the fact that the organism produces propionic acid during fermentative metabolism. Which of the following statements about fermentative metabolism is true?
Fermentation produces significantly less ATP than aerobic respiration; however it generates NAD+, which can be used in glycolysis.
Enterobacteriaceae characteristics
Gram-negative, non spore-forming rods Amotile or peritrichously flagellated Facultative anaerobes Simple growth requirements Ferment glucose, reduce nitrate
The pneumococcal vaccine was made using the purified capsular material from 23 common strains of Streptococcus pneumoniae, but it is not effective against all strains. Why is this?
It cannot cover all the strains of Streptococcus pneumoniae because not all strains have the same antigens on their surface.
The LPS, or endotoxin, of Neisseria gonorrhoeae is slightly different from most Gram-negative organisms because of the absence of repeating O-antigens; hence, it is called LOS instead of LPS. How could LOS be a major virulence factor for Neisseria gonorrhoeae?
LOS is a major virulence factor for Neisseria gonorrhoeae because during the course of the infection, the LOS is released by autolysis. The release of LOS (endotoxin) and the damage it causes to host cells is the major cause of most of the symptoms of gonorrhea.
Gonorrhea is usually a sexually transmitted disease caused by the organism Neisseria gonorrhoeae. Which of the following statements regarding the transmission of Neisseria gonorrhoeae is FALSE?
Neisseria gonorrhoeae is commonly transmitted through the sharing of needles during drug use or by contaminated blood products.
Are Clostridium botulinum vegetative cells required to be present for foodborne botulism to occur?
No, foodborne botulism is caused by the botulinum toxin produced by the bacteria, not the bacteria themselves.
the problem of replicating in the 3'--->5' direction is that it results in a lagging strand which is made in bits and pieces which is called
Okazaki fragments
Which of the following is a characteristic of biological transmission from Dermacentor to a human host?
R. rickettsii is transmitted to the human host during a bite, when tick saliva enters the wound.
The enzyme that catalyze the elongation of mRNA is called
RNA polymerase
the enzyme that catalyzes the elongation of mRNA is called
RNA polymerase
A man comes to the clinic with an oozing wound he got while preparing dinner. The doctors at the clinic suspect infection with E. coli and treat him with an antibiotic. The man goes home and his symptoms improve, so he discontinues the antibiotic. Within a few days he becomes gravely ill with shocklike symptoms such as fever, hypotension, high heart rate and fatigue/mental confusion. Why did the man become so sick after taking the antibiotic that was supposed to make him better?
The antibiotic given to the man and the man's own immune response caused the lysis of the E. coli cells and release of endotoxin (LPS). This caused his secondary symptoms of endotoxic shock.
Strains of Streptococcus pneumoniae can cause disease only when a capsule is present. Why is the presence of a capsule considered a virulence factor?
The capsule prevents the bacterium from being digested after endocytosis in the cells of the host.
Of the pathogenic forms of Escherichia coli, the strain O157:H7 is the primary cause of hemorrhagic colitis, or bloody diarrhea, and can progress to the often fatal hemolytic uremic syndrome (HUS). What is the main reason for the severity of illness from this strain of E. coli?
The main reason for the severity of illness comes from the ability of this particular strain of E. coli to produce Shiga-like toxin, which causes an intense inflammatory response in the gut.
Streptococcus pneumoniae was originally named Diplococcus pneumoniae. Why was the genus name Diplococcus originally given to this organism?
The prefix di- means "two", and these organisms are usually found in pairs under the microscope.
A clinical sample from a patient's mouth reveals the presence of spirochetes. Which of the following is the most accurate interpretation of this result?
The spirochetes may or may not be involved in a pathogenic process.
Even though Escherichia coli can cause, on occasion, severe human disease, there is no vaccine developed for it. Why do you think this is?
There is no vaccine developed for Escherichia coli because it is an advantageous part of our normal intestinal flora.
Over 90% of urinary tract infections (UTIs) are caused by Escherichia coli strains. UTIs are 14 times more common in women than in men. Why do you think this is?
UTIs caused by E. coli are 14 times more common in women than in men because women have a shorter urethra than men and the proximity of the urethra to the anus is much closer in women.
Until very recently, it was thought that peptic ulcers were caused by stress, spicy foods, alcohol consumption, and excess stomach acid production. Why was it controversial to suggest that a bacterium could be a root cause for peptic ulcers?
Until recently, scientists did not believe that bacteria could survive and reproduce in the harsh, acidic environment of the stomach.
Which of the following are properties of exotoxins?
Very small amounts of exotoxin can be lethal.Exotoxins target specific cellular structures or molecules.Exotoxins are protein molecules.
A positive Mantoux test reading is based upon
a wheal measuring 10mm or ore
Which of the following is the result of the action of cell wall inhibiting drugs?
cells become more susceptible to osmotic pressure
the structural form of the DNA molecule is commonly called
double helix
All of the following are caused by Staphylococcus aureus except:
erysipelas
for people who are allergic to penicillins the drug of choice is
erythromycin
what molecule aids in separating the double helix DNA
helicase
Which of the following is NOT an expected transmission pattern of Yersinia pestis?
humans - fleas - humans
cephalosporins
inhibit cell wall synthesis are resistant against penicillinase producing bacteria have b-lactam ring
Treponema pallidum is transmitted almost solely by sexual contact because _____
it is extremely fastidious and sensitive
What codes for proteins?
jgenes
which of the following is the drug of choice for ringworm?
miconazole
Which of the following streptococcal infections is usually fatal?
necrotizing fasciitis
these all hold true of quinine except
nontoxic quinine is chloroquine parent, antimalarial standard
which is the correct order for the folding or organization of the DNA molecule
nucleosome, chromatin fiber, looped domain, metaphase chromosome
The major sign of pertussis occurs during which of the following phases of the disease?
paroxysmal phase
The beta lactam ring is a molecular component of:
penicillin
Which of the following is NOT a suitable antibiotic for the treatment of Rocky Mountain spotted fever?
penicillin
syphillis can be transmitted by
sexual contact & transplacental infection
All of the following methods of food storage or preparation except which of the following can help prevent foodborne botulism?
storing canned foods at room temperature
The combination of trimethoprim and sulfonamide achieves __ and thus lowers the lone dose of each.
synergism
What is an anticodon part of?
tRNA
All of the following drugs work by competitive inhibition EXCEPT for
tetracycline
Which of the following is NOT a virulence factor for Helicobacter pylori?
the ability of H. pylori to enter cells for protection
staphylococcal food poisoning can be avoided by heating ____ for at least ___ minutes
too 100 c, 30
The creation of mRNA from the DNA is called
transcription
A student was bitten by a tick and fears that she may be at risk for contracting tularemia. She removed the tick a very short time after it had bitten her. Is she at risk for tularemia?
yes, because Francisella is one of the most infectious of all bacteria