MasteringMicro Activity #12

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.

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.

How are patients typically infected with listeriosis?

Contaminated food or drink

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.

Which condition is associated with bacterial infection of the bladder?

cystitis

Some strains of E. coli have __________ allowing them to bind and then enter into epithelial cells of the urethra.

fimbriae

A characteristic symptom of necrotizing fasciitis is that the pain __________.

is disproportionate to the appearance of the infection

How might an infected patient transmit listeriosis to another human?

During pregnancy.

Why is necrotizing fasciitis so difficult to prevent?

It is part of the normal microbiota.

If ampicillin is the prescribed treatment for listeriosis, why might a physician instead prescribe trimethoprim-sulfamethoxazole

Patients may be allergic to penicillins.

One of the primary reasons the disease is able to evade the body's immunity is that it __________.

resists digestion by phagocytes

In approximately 10% of patients tubercles rupture and reactivate infection. This is known as _____ tuberculosis.

secondary

One of the virulence factors produced by Group A Streptococcus is __________, which can kill neutrophils, the immune system's first responders.

streptolysin S

Which practice would NOT be a good way to prevent foodborne botulism?

Storing canned foods at room temperature.

Which of the following bacteria is the primary cause of necrotizing fasciitis?

Streptococcus pyogenes

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.

Why does tuberculosis involve months of antibiotic treatment?

The bacteria grow very slowly.

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.

What is the primary source of infection for UTIs?

Fecal contamination

Which demographic is most likely to develop a urinary tract infection?

Females

Visualize It! Figure 1

Figure 20.9 (pg. 585)

__________ are the primary means by which Neisseria gonorrhoeae attaches to the mucous membranes of the reproductive tract.

Fimbriae

To diagnose meningitis due to Listeria infection, physicians will first examine a patient's ___.

cerebrospinal fluid

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.

What percent of patients are estimated to die from the disease? (Necrotizing Fasciitis)

20%

It is estimated that _____ of the world's population may be infected with tuberculosis.

33%

What is listeriolysin O?

An enzyme breaks the bacteria free from the phagosome.

Which of the following habits will best prevent infection due to listerosis?

Avoid eating raw fruits and vegetables

What is the name of the vaccine given to prevent TB in countries where it is endemic?

BCG vaccine

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.

Acute inflammation is an initial, nearly immediate response to microbial invasion. The acute inflammatory response can be beneficial and is frequently successful in containing and defeating bacterial infection. Scenario: an open cut is infected with Gram-negative bacteria. Place the events of acute inflammation in the most likely order from beginning of infection to fully developed inflammation.

Earliest -> Latest 1. Complement cascade initiated by lectin pathway. 2. MAC formation damages bacteria. 3. Endotoxin triggers complement cascade by alternate pathway. 4. Vasodilation of nearby arterioles and capillaries. 5. Phagocytes enter tissue and attack bacteria. 6. Tissue around infection site becomes swollen, red, and warm to the touch.

Various types of damage can lead to acute inflammation, including cuts and abrasions, heat, and microbial damage. Some microbes have structures which can trigger the acute inflammatory response when they invade tissues. What structural characteristics common to Gram-negative bacteria may trigger the acute inflammatory response?

External polysaccharides & Lipid A

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.

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.

What might a clinician expect to observe in the urinalysis of a patient with a UTI?

Leukocytes

Gram-negative bacteria are responsible for the majority of Healthcare Associated Infections (HAI's, also known as nosocomial infections). Serious disease may result when Gram-negative bacteria establish opportunistic infection of nearly all body systems. These HAI's have several signs in common. The signs of opportunistic HAI's with Gram-negative bacteria typically include high fever, inflammation, tissue edema, low blood pressure and DIC. What common structural characteristic of Gram-negative bacteria is directly or indirectly responsible for these signs?

Lipid A

The outer membrane of Gram-negative bacteria contributes to their ability to cause disease (pathogenicity). One of the components of the outer membrane is called an "endotoxin". Match the following terms with their description as part of the Gram-negative bacterium.

Lipid A is released when the outer membrane disintegrates The lack of a thick Cell wall causes Gram-negative bacteria to stain pink, in contrast with Gram-positive bacteria staining purple. Porin(s) allow monosaccharides to move across the membrane. Periplasm contains water, nutrients, and enzymes necessary for bacterial survival.

Bacteria are grouped into two categories reflecting structural features of their cells. Bacteria are classified as Gram-positive or Gram-negative based on whether or not they retain the crystal violet dye used in the Gram stain procedure. Cell wall structure determines the ability to retain the dye, thus cell wall structure is the basis of categorization into Gram-positive (G+) and Gram-negative (G-). Which of the following occurs only in Gram-negative bacteria?

Lipopolysaccharide

__________ is an antiphagocytic factor and helps S. pyogenes attach to nose and throat cells.

M protein

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.

Match the genera of pathogens to their appearance in stained smears. Drag the appropriate labels to their respective targets.

Pages 576 & A-3 in textbook

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.

The polymerization of actin filaments allows Listeria to form pseudopods extending from the host cell. How does this aid the bacteria during infection?

They are able to spread to neighboring cells sheltered from detection by the host immune system.

How do clinicians primarily screen for tuberculosis in patients?

Tuberculin skin test

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.

Which of the following measures would be most effective in preventing a UTI?

Wiping front to back after defecation

Mycobacterium tuberculosis is considered a(n) __________

aerobe