Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Dermatology > Microbiology > Flashcards

Microbiology Flashcards

You may prefer our related Brainscape-certified flashcards:
Dermatology Board Prep flashcards
1
Q

Name five virulence factors

A
  • adhesin
  • invasin
  • impedin
  • aggressin
  • modulin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is adhesin?

A

Enables binding of the organism to host tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is invasin?

A

Enables the organism to invade a host cell / tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is impedin?

A

Enables the organism to avoid host defence mechanisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is aggressin?

A

Causes damage to the host directly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is modulin?

A

Induces damage to the host directly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are virulence factors?

A

The factors responsible for the variation in virulence within and between species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe staph aureus skin infections

A
  • anterior nares and perineum
  • nosocomial and community
  • coagulase positive
  • nasal strain can protect
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe staph epidermidis skin infections

A
  • 100% colonisation
  • skin and mucous membranes
  • coagulase negative
  • nosocomial infection / immunocomprimised
  • associated with foreign devices eg. catheters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe MRSA

A
  • defined by flucloxacillin resistance
  • mainly nosocomial
  • elderly and immunocomprimised
  • intensive care units
  • burns patients
  • surgical patients
  • intravenous lines
  • dialysis patients
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name presentations of staph aureus skin infections

A
  • rash
  • folliculitis
  • abscess
  • carbuncle (multiocular abscess)
  • impetigo
  • scalded skin syndrome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the pathogenicity of staph aureus

A
  • superficial lesions; boil to abscesses
  • systemic; life threatening
  • toxinoses; toxic shock, scalded skin syndrome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is TSST-1?

A
  • toxinose

- rapid progression (48hrs) high fever, vomiting, diarrhoea, sore throat, muscle pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is staphylococcal food poisoning?

A
  • toxinose
  • enterotoxin SeA, SeB and SeC
  • intoxication, 1-5hrs, vomiting, diarrhoea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is scalded skin syndrome?

A
  • toxinose
  • exfoliatin toxins, often neonatal, face, axilla and groin
  • ETA and ETB toxin target desminogen (DG-1)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe superantigens

A
  • activate 1 in 5 T cells
  • TSST-1 in particular associated with toxic shock
  • antigen is not processed by PMN bonds directly to MHC11 complex ie. outside conventional binding groove
  • massive release of cytokines and inappropriate immune response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe the diagnostic criteria of toxic shock syndrome

A
  • fever; 39 degrees
  • diffuse macular rash and desquamation; diffuse macular erythroderma
  • hypotension
  • 3 or more organ systems involved; liver, blood, renal, mucous membrane, GI , muscular, CNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe adhesins

A
  • attachment and colonisation

- extra cellular matrix are present on epithelial, endothelial surfaces as well as a component of blood clots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe panton-valentine leukocidin

A
  • PVL bicomponent toxin
  • specificity toxicity for leukocytes
  • present in 1-2% clinical strains
  • PVL associated with sever skin infections eg recurrent furunculosis, sepsis or necrotising fasciitis
  • PVL and alpha toxin linked with CA-MRSA responsible for necrotising pneumonia and contagious severe skin infections
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe necrotising pneumonia

A
  • preceding influenza like syndrome
  • necrotising haemorrhagic pneumonia
  • rapid progression
  • acute respiratory distress
  • deterioration in pulmonary function
  • refractory hypoxaemia
  • multi-organ failure despite antibiotic therapy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Name the skin infections caused by streptococcus pyogenes

A
  • impetigo
  • cellulitis
  • necrotising fasciitis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the lancefield system

A
  • serotyping of cell wall carbohydrate
  • major serotypes A-H and K-V (20)
  • C polysaccharides extracted from cell wall
  • group A further subdivided according to M protein antigens
  • M1 and M3 major serotype
  • M3 and M18 severe invasive disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe impetigo

A
  • usually face
  • highly contagious through contact with discharge on the face
  • infection immediately below the surface
  • GAS skin disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe cellulitis

A
  • GAS skin disease
  • deeper skin infection in the dermis that is not associated with necrosis
  • erysipelas (localised) fever, rigours and nausea
  • range of spreading subcutaneous skin infections
  • trauma or primary infection associated with organism spreading through blood and seeding cellulitis
25
Q

Describe necrotising fasciitis

A
  • invasive group A streptococci
  • type 1, clostridia spp
  • invasive step a strains penetrate mucous membrane and develop in lesion
  • rapidly destroys connective tissue
26
Q

What is virulence and virulence factors?

A
  • the molecular / genetic basis of pathogenesis that characterises species, sub-species and strains
27
Q

Where is staph pyogenes usually found?

A

In the pharynx but also adheres to the skin

28
Q

Name some competitive bacterial flora (commensals)

A
  • staphylococcus epidermidis
  • corynebacterium sp (diphtheroids)
  • propionibacterium sp
29
Q

What is a carbuncle?

A

A series of abscesses connected by sinuses

30
Q

What colour of sample bottle is used for aerobic blood cultures?

A

Green

31
Q

What colour of sample bottle is used for anaerobic blood cultures?

A

Red

32
Q

Describe staphylococcus species

A
  • gram positive cocci in clusters
  • aerobic and facultatively anaerobic (grows best aerobically, but also grows anaerobically)
  • 2 important types; staph aureus and coagulase negative staph
33
Q

Describe the features of staph aureus

A
  • common human pathogen
  • produces enzymes, including coagulase, an enzyme that clots plasma
  • causes wound, skin, bone and joint infections
  • resistant strains (MRSA)
  • some strains produce toxins
34
Q

Describe staph aureus skin infections

A
  • 30% of hospital staff are carriers
  • boils and carbuncles
  • other minor skin sepsis (infected cuts etc)
  • cellulitis
  • infected eczema
  • impetigo
  • wound infection
  • staphylococcal scalded skin syndrome
35
Q

Name the strains of staph aureus

A
  • enterotoxin (food poisoning)
  • SSSST (staphylococcal scaled skin syndrome toxin)
  • PVL (panton valentine leucocidin, more often in systemic disease)
36
Q

Name the antibiotics of choice for staph aureus

A
  • flucloxacillin
37
Q

Name MRSA treatment options

A
  • doxycycline (bacteriostatic)
  • co-trimoxazole
  • clindamycin
  • vancomycin

NOT FLUCLOXACILLIN

38
Q

Describe the features of coagulase negative staphs (eg staph epidermidis)

A
  • skin commensals - not usually pathogenic
  • may cause infection in association with implanted artificial joints, artificial heart valves, IV catheters
  • staph saprophyticus causes urinary tract infection in women of child bearing age
39
Q

Describe the features of streptococcus species

A
  • gram positive cocci in chains
  • aerobic (and facultatively anaerobic)
  • classified initially by haemolysis on blood agar
40
Q

Describe beta haemolytic streptococci

A
  • pathogenic organisms
  • haemolysin is one of many toxins (enzymes) produced that damage tissues
  • further classified by antigenic structure on surface (serological grouping)
  • group A (throat, severe skin infections)
  • group B (meningitis in neonates)
41
Q

Describe alpha haemolytic streptococci

A
  • 2 important categories - strep pneumoniae; commonest cause of pneumonia
  • strep viridans; commensals of mouth, throat, vagina - cause infection endocarditis
42
Q

Describe non-haemolytic streptococci

A
  • enterococcus (e faecalis, e faecium)
  • commensals of bowel
  • common cause of UTI
43
Q

Describe the diseases strep pyogenes is involved with / causes (group a strep)

A
  • infected eczema
  • impetigo
  • cellulitis
  • erysipelas
  • necrotising fasciitis
44
Q

Describe the treatment of staphylococcal and streptococcal infections

A
  • minor skin sepsis may not require antibiotics
  • staph aureus - flucloxacillin
  • group a step - penicillin (not flucloxacillin)
  • necrotising fasciitis - life threatening, requires surgical debridement as well as antibiotics
45
Q

Describe necrotising fasciitis

A
  • bacterial infection spreading along fascial planes below skin surface > rapid tissue destruction
  • little to see on skin but severe pain
  • 2 types
  • urgent surgical debridement and opinion required
  • antibiotic treatment depends on organisms isolated form tissue taken at operation
46
Q

Describe the two types of necrotising fasciitis

A
  • type 1; mixed anaerobes and coliforms, usually post abdominal surgery
  • type 2; group a strep infection
47
Q

When would you take a swab of a leg ulcer?

A

Only is signs of cellulitis or infection are present

48
Q

Name the different dermatophyte (fungal) infections (ringworm)

A
  • tinea capitis; scalp
  • tinea barbae; beard
  • tinea corporis; body
  • tinea manuum; hand
  • tinea unguium; nails
  • tinea cruris; groin
  • tinea pedis; foot (athletes foot)
49
Q

Describe the pathogenesis of dermatophyte

A
  • fungus enters abraded or soggy skin
  • hyphae spread in stratum corneum
  • infects keratinised tissues only (skin, hair, nails)
  • increased epidermal turnover causes scaling
  • inflammatory response provoked (dermis)
  • hair follicles and shafts invaded
  • lesion grows outward and heals in centre, giving a ring appearance
50
Q

Who is more commonly affected by dermatophyte infections?

A

Males

51
Q

Scalp ringworm usually affects who?

A

Children

52
Q

Name some sources of infection of dermatophyte infections

A
  • other infected humans; the most likely source
  • animals - zoophilic fungi
  • soil (less common in UK)
53
Q

Name some casual organisms of dermatophyte infection

A
  • trichophyton rubrum (>70% of lab isolates)
  • trichophyton mentagraphytes
  • microsporum canis (occasional isolate, cats / dogs to humans)
54
Q

Describe the diagnosis of dermatophyte infection

A
  • clinical appearance
  • woods light (fluorescence)
  • skin scrapings, nail clippings, hair
  • send to laboratory in a dermapak for microscopy and culture
  • culture takes 2 weeks +
55
Q

Describe the treatment of dermatophyte infections

A
  • small areas of infected skin, nails
  • clotrimazole (canestan) cream or similar
  • topical nail paint (amorolfine)
  • extensive skin infections
  • nail infections
  • scalp infections
  • terbinafine orally (topically for athletes foot and on occasion with cellulitis)
  • itraconazole orally
56
Q

Describe candida skin infection

A
  • candida causes infection in skin folds where area is warm and moist
  • seen under the breasts in females, groin areas, abdominal skin folds etc, nappy area in babies
  • diagnosis; swab for culture
  • treatment; clotrimazole cream, oral fluconazole
57
Q

Describe scabies

A
  • caused by sacroptes scabiei
  • chronic crusted form is termed norweigan scabies (highly infectious)
  • incubation period up to 6 weeks
  • intensely itchy rash affecting finger webs, wrists and genital area
  • treatment; malathion lotion, applied overnight to whole body and washed off the next day
  • benzyl benzoate (avoid in children)
58
Q

Describe lice (pediculosis)

A
  • pediculus captitis (head louse)
  • pediculus corporis (body louse)
  • phthirus pubis (pubic louse)
  • associated with intense itch
  • treatment; malathion
59
Q

Describe infection control in dermatology

A
  • gloves and plastic aprons required for dressing changes
  • patients who need single room isolation and contact precautions;
  • patients with group a strep infection
  • MRSA patients
  • patients with scabies (long sleeved gowns also required for norweigan scabies)

Dermatology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions