Introduction to Skin Infections:microbiology

thank u for participation brother Khaled..
what I wrote in green is the q and its answer

Most skin infections are?
A) contracted from animals:somecomes from bites of animals but not most of them..
B) spread by the respiratory route:Noneare spread through the respiratory route...
C) contracted from doctors and nurses:some,indeed but not most..
D) endogenous infections contracted from bacteria colonizing the skin and nasopharynx:Staphylococcus aureus is carried by many individuals in the anterior nares and also on the skin and Streptococcus often colonizes the pharynx and the skin. So most skin infections are caused by an individual's own flora. Not all, of course.

question2:
What is the causative agent of impetigo?
A) Staphylococcus aureus:yes it is one of them but not the best answer...
B) Staphylococcus epidermidis:this usually lives in skin with no problems...
C) Streptococcus pyogenes:yes it is one of them but not the best answer...
D) E.coli:that does not cause impetigo..
E) more than one of the above:yes, either Staphylococcus aureus, Streptococcus pyogenes (the most common) or a mixture of the two can cause impetigo

Question3":
Which of the following is a predisposing factor for infection of the deeper layers of the skin?
A) trauma
B) surgery
C) diabetes:this is definitely one, but there is a better answer. Diabetes can compromise both the nerves and the small blood vessels, leading to inadvertent injuries and poor wound healing.
D) alcoholism:this is definitely one, but there is a better answer. This is likely a predisposing factor due to inadvertent injury
E) all of the above:yes, anything that causes a break in the skin and/or compromises the blood flow to the skin will predispose to skin infections

A patient has progressive warmth, redness, swelling, and tenderness of an extremity, but only appears mildly ill. He or she likely has?
A) impetigo:no, this presents with pustules or vesicles that can open and crust over

B) cellulitis:yes, a key here is the progressive nature of the disease
C) abscess:no, an abscess is a confined infection
D) gas gangrene:no, this presents with symptoms of necrotizing fasciitis; severe pain, bullous lesions, purplish skin, evidence of gas in tissues, and crepitance
E) toxic shock:well, actually the patient could develop toxic shock or toxic shock-like syndrome if he/she were infected with Staphylococcus aureus or Streptococcus pyogenes, respectively. But not all strains of Staph or Strep can lead to this complication. They must carry the gene for the toxin.

question5:
Features that distinguish necrotizing fasciitis from cellulitis include?
A) redness and swelling:no, this can be found in both necrotizing fasciitis and cellulitis
B) elevated WBC:no, this is found in both necrotizing fasciitis and cellulitis, although the count may be higher in necrotizing fasciitis .
C) severe pain in the absence of cutaneous findings:yes, this can be a sign of necrotizing fasciitis.another is bullous skin lesions and dark reddish-purple skin
D) crusty vesicles:no, these are characteristic of impetigo, a very superficial infection
E) fever:no, this is found in both necrotizing fasciitis and cellulitis, although the fever could be higher in the case of necrotizing fasciitis

Actually I also hadn't known most of them until I saw the answers...I mean it is very normal to make mistakes here but not to make them infront of the patient..the most important is the benefit

here are the others :

Question 6 - Single Best Answer

Antibiotic ointment applied to the anterior nares is used for which of the following?

A) clear carriage of Staphylococcus aureus
B) impetigo
C) facial cellulitis caused by Haemophilus influenzae
D) sinus infection
E) clenched fist injury

Question 7 - Single Best Answer

A skin abscess or boil is most often caused by?

A) Staphylococcus aureus
B) Staphylococcus epidermidis
C) Streptococcus pyogenes
D) Pseudomonas aeruginosa
E) Clostridium tetani

Question 8 - Single Best Answer

Clostridium tetani is extremely dangerous because?

A) it can grow in the absence of air
B) it can cause gangrene
C) it produces a neurotoxin
D) it is resistant to antibiotics
E) it is a spore forming organism

Question 9 - Single Best Answer

Infections of dog and cat bites are likely to be caused by?

A) Staphylococcus aureus
B) Staphylococcus epidermidis
C) Streptococcus pyogenes
D) Eikenella corrodons
E) Pasteurella sp

So dear Qusei u've got 3 out of 4 ...excellent
Q AND THEIR ANSWERS IN GREEN

Question 6 - Single Best Answer

Antibiotic ointment applied to the anterior nares is used for which of the following?

A) clear carriage of Staphylococcus aureus:yes, this is very important in a hospital setting where personnel can spread Staph infections, and also in individuals with recurring Staph folliculitis or abscesses
B) impetigo:it wouldn't help this much
C) facial cellulitis caused by Haemophilus influenzae:no, this would require systemic antibiotics
D) sinus infection:no, topical antibiotics in the nose wouldn't help this
E) clenched fist injury:this usually occurs when someone punches someone else in the mouth. Teeth cause injury to the fist of the puncher and the wound gets contaminated with saliva (puncheeÕs revenge?). As with human bites, the most common causative organism is Eikenella corrodens. Nasally applied antibiotics would not help, they would have to be applied to the site of the injury.

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Question 7 - Single Best Answer:
A skin abscess or boil is most often caused by?

A) Staphylococcus aureus:Yes. Some people think that the coagulase helps to cause to the formation of an abscess
B) Staphylococcus epidermidis:this doesnÕt cause abscesses. It does not make coagulase which is one reason that some people think that coagulase contributes to the pathogenesis of an abscess
C) Streptococcus pyogenes:This is more likely to cause spreading infections, rather than "walled off" infections
D) Pseudomonas aeruginosa:This doesnÕt cause abscesses. In an abscess there may be a low oxygen tension as the blood supply has been cut off. Pseudomonas aeruginosa is a strict aerobe with no fermentative metabolism, so wouldn"t grow well in an abscess
E) Clostridium tetani:no, often this causes no signs of infecting the skin at all

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Question 8 - Single Best Answer:
Clostridium tetani is extremely dangerous because?

A) it can grow in the absence of air:it can, but this is not what makes it dangerous
B) it can cause gangrene:no, that is a different Clostridium>
C) it produces a neurotoxin:yes, the toxin causes inhibition of release of an inhibitory neurotransmitter, resulting in tetanic spasms (contraction of opposing muscles at the same time). This is usually prevented by inhibitory interneurons in the spinal chord.

D) it is resistant to antibiotics:no, antibiotics can kill the organism but if the toxin is already in the system, the antibiotics don't help much
E) it is a spore forming organism:it is, but this is not what makes it so dangerous. The fact that it can form spores does figure in the pathogenesis of tetanus, however.

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Question 9 - Single Best Answer

Infections of dog and cat bites are likely to be caused by?
A) Staphylococcus aureus
B) Staphylococcus epidermidis
C) Streptococcus pyogenes
D) Eikenella corrodons:This causes infections of human bites (more common than you would think !) but not animal bites
E) Pasteurella sp:yes, Pasteurella multocida is especially common in cat bites.

bassam says:ha ha ha!!! ..As if someone cares or give a damn .........