Infections and Diseases of Skin and CNS

Flashcards covering key concepts, diseases, symptoms, causes, and treatments related to skin and central nervous system infections from the lecture notes.

What are the three main layers of the skin?

Epidermis, dermis, and hypodermis.

What is the primary function of the keratin layer in the skin?

It provides a protective, water-repellent layer that sheds off and can withstand UV damage.

Name two skin conditions that Stapylococcus and Streptococcus can cause when they grow in population, even though they are normal flora.

Potentially pathogenic conditions, such as folliculitis or infections related to broken skin.

What bacterium is specifically known to cause acne?

Propionibacterium acnes.

What are the key characteristics of Staphylococcus aureus?

It is a Gram-positive, grape-like shaped bacterium that is non-motile and very resilient, able to withstand high salt, extreme pH, and high temperatures. It is not spore-forming.

What does MRSA stand for and why is it a concern?

MRSA stands for Methicillin-Resistant Staphylococcus aureus, and it is a concern because it is resistant not only to methicillin but also to multiple other antibiotics, making it harder to treat.

How can MRSA primarily spread in a hospital setting?

It can spread through punctured areas from procedures like catheterization or blood draws if health workers do not clean their hands properly.

What are the three key enzymes produced by Staphylococcus aureus and their functions?

Coagulase (coagulates plasma), Hyaluronidase (digests hyaluronic acid/collagen, breaking down tissues), and Catalase (breaks down hydrogen peroxide).

What laboratory test is used to differentiate Staphylococcus from Streptococcus?

The catalase test.

What is the first-line antibiotic treatment for MRSA infections?

Vancomycin.

What is impetigo and what is its characteristic appearance?

Impetigo is a superficial skin infection primarily seen in children, characterized by a dry, crusty, golden crust.

What toxins produced by Staphylococcus aureus are responsible for impetigo's flaking and blistering symptoms?

Exfoliative toxin A and B.

Where is Streptococcus pyogenes commonly found and what serious conditions can it cause?

It is mostly found in the throat/tonsils and can lead to scarlet fever, heart problems, pneumonia, necrotizing fasciitis, sepsis, and rheumatic fever.

How do scarlet fever and rheumatic fever differ in presentation?

Scarlet fever presents as red dots all over the body, mainly the trunk, as a sign of strep infection, while rheumatic fever describes heart valvular problems.

What is the key distinguishing feature between impetigo and cellulitis?

Cellulitis is a lot deeper infection than impetigo, causing more pain, swelling, and tenderness, and it spreads very quickly.

What is Staphylococcal Scalded Skin Syndrome (SSSS)?

SSSS is a severe form of impetigo, mainly seen in newborns and infants, where the skin literally sheds off and peels, described as 'crumpled piece of paper'.

What is the causative agent of gas gangrene and what is a key characteristic of this bacterium?

Gas gangrene is caused by Clostridium perfringens, which is a spore-forming, anaerobic bacterium.

Why does Clostridium perfringens cause gas even though it is anaerobic?

It causes gas due to fermentation, a process it uses instead of oxygen, producing byproducts like methane.

What is the alpha toxin produced by Clostridium perfringens responsible for?

It causes red blood cell rupture, edema, tissue destruction, and the breakdown of collagen and DNA.

What treatment is specifically effective against anaerobic bacteria like Clostridium perfringens in gas gangrene?

Oxygen therapy, as oxygen actually kills anaerobic bacteria.

Define bullum, cyst, and Macula as skin lesions.

Bullum is a very big blister (e.g., in gas gangrene); Cyst is much smaller and semi-solid (e.g., cystic acne); Macula is a very flat lesion with color changes (e.g., freckles).

How does a maculopapular lesion differ from a macula?

A maculopapular lesion is slightly raised with a little bump and has a more vibrant color (reddish, pinkish, purplish), while a macula is flat with varying color changes (darker/lighter pigmentations).

What is the difference between pustules and vesicles?

Pustules are small, elevated, fluid-filled lesions containing pus (e.g., acnes), whereas vesicles are elevated, fluid-filled lesions with clear fluid (e.g., chickenpox).

What virus causes chickenpox and what is its associated vaccine?

Chickenpox is caused by Human Herpes Virus type 3 (HHV-3), and the vaccine is called Varicella.

What is the relationship between chickenpox and shingles?

Shingles is a reactivation of the HHV-3 virus that lies dormant in the nerves after a person has had chickenpox; it presents as asymmetrical lesions along a dermatome.

What disease is characterized by red blisters on the palms, soles, buttocks, knees, and elbows, primarily in young children?

Hand-Foot-Mouth disease, caused by an Enterovirus (Coxsackievirus).

What are the common clinical signs of measles (rubeola)?

Conjunctivitis, fever, and distinctive Koplik spots (maculopapular rash inside the mouth).

What is the most severe and rare complication of measles?

Subacute sclerosing panencephalitis, a progressive neurodegeneration of the white matter and brain stem with a very high mortality rate.

How is measles transmitted?

Through droplet contact, not skin-to-skin contact.

Why is German measles (rubella) a significant concern, especially for pregnant women?

While the rash is minor, rubella causes serious damage to the fetus, leading to miscarriage, birth defects (e.g., deafness, cardiac abnormalities, mental/physical retardation), known as Congenital Rubella Syndrome.

What is the characteristic appearance of Fifth Disease and what virus causes it?

Fifth Disease (Erythema Infectiosum) is characterized by a 'slapped cheek' appearance and is caused by Parvovirus B19.

What is Roseola (Sixth Disease) primarily known for in young children?

It is known for a very high-grade fever lasting about three days, often without a rash, and can lead to febrile seizures due to the high fever.

What type of virus causes Roseola?

Human Herpes Virus Type 6 (HHV-6).

What medical conditions are associated with Human Papillomavirus (HPV)?

Warts (including genital warts) and cervical cancer in women.

What prevents Leishmaniasis and how is it transmitted?

Leishmaniasis is caused by the parasite Leishmania donovani and is transmitted as a zoonosis by female sandflies.

What is the distinctive skin lesion caused by Bacillus anthracis (Anthrax)?

A black eschar, which is a black, dry lesion where the entire tissue is typically dead.

What does 'tinea' refer to in skin infections, and how are these infections categorized?

'Tinea' refers to ringworm (a fungal infection), and these infections are categorized by their anatomical location, such as tinea capitis (head), tinea pedis (foot), or tinea unguium (nail).

What fungal infection causes tinea versicolor and what is its appearance?

Malassezia furfur causes tinea versicolor, appearing as cafe au lait or depigmentation patches.

What are azole drugs used to treat?

Fungal infections.

What protective structures surround the brain and spinal cord, and what is their primary function?

The meninges (dura mater, arachnoid mater, pia mater) surround them, providing protection, and the cerebral spinal fluid (CSF) provides nutrition, protection, and cushions the brain.

At which lumbar levels is CSF typically extracted and why?

CSF is typically extracted at L3-L4 to avoid hitting the spinal cord, which usually ends around L1-L2.

What is the initial empiric treatment for bacterial meningitis?

Ceftriaxone, a third-generation cephalosporin, due to its broad-spectrum activity.

How does the blood-brain barrier protect the central nervous system?

It acts as a filter, allowing very few molecules to pass from the blood to the brain, thereby protecting the CNS from microorganisms and maintaining its sterile environment.

What are the classic signs and symptoms of meningitis?

Photophobia (light sensitivity), headache, neck stiffness/pain (nuchal rigidity), high fever, and increased WBC count in CSF.

What is the most common bacterial cause of meningitis, especially in young adults?

Neisseria meningitidis, a Gram-negative diplococci.

What are the common causes of viral meningitis?

Mainly enteroviruses (accounting for 90% of cases) and human herpes viruses (herpes simplex).

What is the common name for Coccidioides infection, and where is it endemic?

It is commonly known as Valley Fever and is endemic in areas like Nevada, Arizona, New Mexico, Southern Texas, and Southern California, commonly associated with disturbed soil after events like earthquakes.

What is Naegleria fowleri commonly known as, and how is it acquired?

It is known as the 'brain-eating amoeba,' acquired when contaminated water (stagnant or fresh) enters the nose and travels to the brain.

How do HSV-1 and HSV-2 infections typically differ in their primary location?

HSV-1 is predominantly found in the mouth (cold sores), while HSV-2 is predominantly found in the genital area, though cross-infection can occur.

What parasite causes toxoplasmosis, and what animal is a primary source of transmission?

Toxoplasma gondii causes toxoplasmosis, and it is primarily transmitted through contact with felines (cats), particularly from their feces.

What neurological effect is caused by the poliovirus?

It causes neuromuscular paralysis by destroying the anterior horn of the spinal cord.

How is poliovirus transmitted?

By oral ingestion, typically through the fecal-oral route.

What type of paralysis does tetanus cause, and why?

Tetanus causes spastic paralysis (uncontrollable muscle contraction) because its neurotoxin destroys inhibitory neurons in the spinal cord, preventing muscles from relaxing.

What type of paralysis does botulism cause and how does it achieve this?

Botulism causes flaccid paralysis (muscle weakness/relaxation) by inhibiting the binding of acetylcholine at the presynaptic junction, preventing muscle contraction.

Why is it advised not to give honey to children under one year old?

Honey can contain Clostridium botulinum spores, which can lead to infant botulism due to their undeveloped immune systems.