Microbiology Flashcards
1
Q
what is virulence based on?
A
the genetics of the organism
2
Q
what is virulence?
A
the capacity of a microbe to cause damage to the host
3
Q
what is adhesin?
A
enables binding of the organism to host tissue
4
Q
what is invasin?
A
enables the organism to invade a host cell/tissue
5
Q
what is impedin?
A
enables the organism to avoid host defenses i.e. barriers
6
Q
what is aggressio?
A
causes damage to the host directly
7
Q
what is modulin?
A
induces damage to the host indirectly i.e. induces host’s own immunity system to turn on the host
8
Q
name the virulence factors
A
adhesin invasin impedin aggressin modulin
9
Q
where is Staph. aureus found on the body as a commensal organism?
A
anterior nares & perineum
10
Q
what is a virulence factor?
A
an ability of the organism which enables it to survive
11
Q
what is the pathogenicity of staph. aureus?
A
can cause:
superficial lesions
systeimic problems
toxinoses
12
Q
name two types of adhesins
A
fibrinogen-binding
collagen-binding
13
Q
name an impedin
A
being a superantigen
PVL
14
Q
what is a Panton-Valentine Leukocidin (PVL)?
A
a specific toxin for leukocytes associated with severe skin infections
assoc. with CA-MRSA
15
Q
what two main conditions is PVL responsible for?
A
necrotising pneumonia & contagious severe skin infections
16
Q
what are the clinical features of necrotising pneumonia?
A
necrotising haemorrhagic pneumonia
acute respiratory distress
refractory hypoxaemia
multi-organ failure
17
Q
what type of symptoms usually precede necrotising pneumonia?
A
influenza like syndrome
18
Q
how does narcotising pneumonia progress?
A
rapidly
19
Q
name a suprantigen
A
TSST-1, causes a massive release of cytokines & an inappropriate immune response
20
Q
what is the diagnostic criteria for toxic shock?
A
fever
diffuse macular rash & desquamation
hypotension
3+ organ systems involved
21
Q
what does streptococcus pyogenes cause?
A
GAS
22
Q
which skin infections does streptococcus pyogenes cause?
A
impetigo
cellulitis
necrotising faciitis
23
Q
what is Lancefeild grouping?
A
a method of grouping catalase-negative, coagulase-negative bacteria based on the carbohydrate composition of bacterial antigens found on their cell walls
24
Q
which Lancefeild group are streptococcus pyogenes in?
A
group A
25
how is group A of the lance field system further divided?
by the M protein antigens
26
what are the M1 & M3 protein antigens on streptococcus pyogenes?
the major serotype
27
what are the M3 & M18 protein antigens on streptococcus pyogenes?
severe invasive disease
28
what is impetigo?
usually found on the face, is an infection immediately below the surface (in the stratum corneum). highly contagious through contact with discharge on the face.
29
what is cellulitis?
a general term for infection deeper in the skin, in the dermis, not associated with necrosis
30
what is erysipelas?
a localised range of spreading subcutaenous skin infections with fever, rigours and nausea
31
how does necrotising fasciitis come about?
invasive strep. A strains penetrate mucous membranes & develop in lesions which rapidly destroy connective tissue
32
name a toxin responsible for tissue/cell destruction?
```
hemolysins
streptolysin S (SLS)
```
33
how is SLS toxic to cells?
is a pore forming cytolysin
34
how does toxic shock like syndrome come about?
through pyrogenic exotoxins as a complication of invasive infections which can be caused by Strep. pyogenes
35
explain what transient flora are?
harmless organisms that live on the skin until it is washed & tired effectively
36
where are S. epidermidis found?
100% colonisation on skin & mucous membrane
37
when will S. epidermidis cause an infection?
in the immunocompromised, associated with foreign devices like catheters
38
what does a coagulase do?
promotes the formation of clots
39
what does fibrinolysin do?
promotes the dissolution of clots
40
what skin conditions can Staph. aureus cause?
```
rash
folliculitis
abscess
carbuncles
impetigo
scalded skin syndrome
```
41
what is a carbuncle?
a multi-follicle abscess
42
what is community acquired Staph. aureus likely to cause?
rash
abscesses
carbuncles
43
what does the presence of collagen-binding protein in an organism mean?
that it is likely to affect specific sites such as bone
44
do most staph. aurues in the community have fibrinogen or collagen-binding properties?
fibrinogen-binding properties
45
what is a toxin?
a single protein component that has a specific affect on the body
46
why can't necrotising pneumonia be supplemented with oxygen?
as the tissue needed to absorb the oxygen has already been destroyed
47
how does menstrual toss shock syndrome come about?
from the tampon becoming infected with S. aureus from the perineum being inserted into the body and then travelling into the bloodstream causing massive infection. S. aureus presumably got into the body via the perineum.
48
if an organism is very encapsulated, what would you expect to see in terms of virulence?
the organism to be very virulent
49
what does staphylococcus look like on gram stain?
gram positive cocci in clusters
50
which 2 types of staphylococcus are important?
staph. aureus
| coagulase negative staph
51
how is staph aureus distinguished from all other staph. species?
is coagulase positive
| i.e. produces enzymes including coagulase, an enzyme that clots plasma
52
where does staph. aureus cause infections?
can cause infections anywhere but specifically:
- wound
- skin
- joints
53
which antibiotic should be given in an staph. aureus infection?
flucloxacillin
54
which toxins do some strains of staph. aureus produce?
enterottoxin
SSSST
PVL
55
what does enterotoxin do to the body?
causes food poisoning
56
what is SSSST?
staph. scalded skin syndrome toxin
57
how does PVL work?
punches holes in the membranes of leukocytes
58
what does PVL usually cause in the UK?
abscesses
59
what are coagulase negative staphs usually?
skin commensals
60
what factor makes it difficult for white cells to attack coagulase negative staph?
they produce a slime
61
what does staph. saprophyticus cause?
urinary tract infection in women of child-bearing age
62
what do streptococcus species look like on gram stain?
gram positive cocci in chains
63
how are streptococcus species classified?
by hamolysis on blood agar
64
what is beta-haemolysis?
complete haemolysis
65
what is alpha-haemolysis?
partial haemolysis
66
what is gamma-hamolysis?
no haemolysis
67
are beta-haemolytic strep. pathogenic or not?
pathogenic organisms
68
name a toxin that beta-haemolytic strep. produce that damages tissue?
haemolysin
69
how are beta-haemolytic strep. further classified?
by antigenic structure on surface (serological grouping) - group A or B
70
give examples of infections caused by group a strep.
throat infections
| severe skin infections
71
give an example of an infection caused by group b strep.
meningitis in neonates
72
wha are the 2 important categories of alpha-haemolytic strep?
strep. pneumoniae
| strep. viridans
73
what is strep. pneumoniae?
a pathogen
| the commonest cause of pneumonia
74
what are strep. viridans?
commensals of the mouth, throat & vagina
| rarely cause infection
75
name a non-haemolytic strep species
enterococcus species
76
what do enterococcus species do?
commensal of bowel
| common cause of UTIs
77
what does dry skin mean in terms of defence against infection?
causes desiccation of micro-organisms
78
what does sebum do in terms of defence against infection?
inhibits bacterial growth
79
what do gram positive organisms have which mean they are unlikely to dry up?
a very thick cell wall
80
what competitive bacterial flora are present on the skin?
staphylococcus epidermidis
corynebacterium sp.
proprionbacterium sp.
81
what bacterial skin infections are caused by staph aureus?
```
boils & carbuncles
minor skin sepsis
cellulitis
infected eczema
impetigo
wound infection
staphyloccal scalded skin syndrome
```
82
which of boils & carbuncles need antibiotics?
carbuncles need antibiotics, boils don't
83
what bacterial skin infections are caused by strep pyogenes (group A strep)?
```
infected eczema
impetigo
cellulitis
erysipelas
necrotising fasciitis
```
84
how are bacterial skin infections diagnosed?
using a swab of the lesion if the surface is broken
by pus or tissue if deeper lesion
+/- blood cultures, if aprorpriate
85
what is first line treatment of strep. pyogenes?
penicillin
86
what is treatment of necrotising fasciitis?
life-threatening condition, requires immediate surgical debridement & antibiotics
87
how does necrotising fasciitis spread?
along fascial planes below skin surface causing rapid tissue destruction
88
what would you see on the skin surface in necrotising fasciitis?
very little to see on skin surface but severe pain
89
what are the two types of necrotising fascitiis?
type 1 - mixed anaerobe & coliforms
| type 2 - group A strep infection
90
when is type 1 necrotising fasciitis usually found?
usually post-abdominal surgery
91
when would you swab a leg ulcer?
if signs of cellulitis or infection are present
92
which organisms are worth treating in leg ulcers?
strep. pyogenes (group A), staph. aureus, other beta-haemolytic strep, anaerobes especially in diabetics
93
what does tinea mean?
ringworm
94
where is tinea capitis found?
scalp
95
where is tinea barbae found?
beard
96
where is tinea corporis found?
body
97
where is tinea manuum found?
hand
98
where is tinea unguium found?
nails
99
where is tinea cruris found?
groin
100
where is tinea pedis found?
foot
101
are males or females more commonly affected by dermatophyte infections?
males
102
which age group does tinea capitis affect?
children (scalp ringworm)
103
which sex do foot & groin ringworm mainly affect?
men
104
where does anthropophilic fungi come from?
from other infected humans
105
where does zoophilic fungi come from?
animals
106
where does geophilic fungi come from?
soil
107
how is trichophyton rubrum transmitted & how often is it seen in the lab?
human-human
| accounts for majority of dermatophyte lab isolates
108
how is trichophyton mentagraphytes transmitted & how often is it seen in the lab?
human-human
| next most common dermatophyte lab isolate
109
how is microsporum canis transmitted & how often is it seen in the lab?
cats/dogs-humans
| only an occasional lab isolate
110
how are dermatophyte infections diagnosed?
clinical appearance
woods light
skin scrapings, nail clippings, hair
111
how do you treat dermatophyte infections in small areas?
clotrimazole cream or similar
| topical nail paint
112
how do you treat dermatophyte infections on the scalp?
terbinafine oraly
| itraconazole orally
113
where does candida infect on the skin?
skin folds where area is warm & moist
| under breasts, groin areas, abdominal skin folds, nappy areas
114
how is candida skin infection diagnosed?
swab for culture
115
how is candida infection treated?
clotrimazole cream
| oral fluconazole
116
what organism causes scabies?
sarcoptes scabiei
117
what is the incubation period of scabies?
up to 6 weeks
118
what does scabies feel & look like?
intensely itchy rash affecting finger webs, wrists & genital area
119
how do you treat scabies?
malathion lotion applied overnight to whole body & washed off next day
benzyl benzoate
120
what age group should benzyl benzoate be avoided in?
children
121
what organism causes head lice?
pediculus capitis
122
what organism causes body louse?
pediculus corporis
123
what name is given to body louse
Vagabond's disease
124
what organism causes pubic louse?
phthirus pubis
125
what symptom are lice associated with?
intense itch
126
how are lice treated?
malathion
127
what organism are chickenpox & shingles due to?
both due to varicella zoster virus
128
who gets chickenpox?
children
129
what happens in chickenpox?
generalised rash & fever
130
what does the chickenpox virus do after the symptoms are gone?
virus establishes latency in sensory nerve roots
131
when chickenpox is reactivated what does it come back as?
shingles
132
when does shingles occur?
typically in old age
133
how does the singles rash appear on the body?
dermatomal
134
how does chickenpox appear & disappear?
macules -> papules -> vesicles -> scabs -> recovery
135
what are the symptoms of chickenpox?
fever
itch
rash
136
what complications can occur in chickenpox?
- secondary bacterial infection
- pneumonitis
- haemorrhagic
- scarring, absent or minor
- encephalitis
137
what are the predictors of severity in chickenpox?
extremes of age
| depressed cell mediated immunity
138
when does neonatal VZV occur?
secondary to chickenpox in mother in late pregnancy
139
what risk is associated with neonatal VZV?
higher mortality
140
how is neonatal VZV prevented in susceptible women?
prevention with varicella zoster immune globulin
141
who does shingles occur in?
elderly & immunocompressed
142
what does shingles feel & look like?
tingling pain -> erythema -> vesicles -> crusts
143
in which age group is the pain of shingles worse?
greater with increasing age
144
what does the pain in shingles feel like?
neuralgic in character
145
is scarring common in shingles?
no
146
which nerve does shingles affect?
trigeminal
147
what can occur after ophthalmic zoster?
scarring & red eye
148
when can ophthalmic zoster occur in children?
if chickenpox in utero or if they become immunocompromised
149
which dermatome does shingles occur in adults?
thoracic & lumbar
150
which dermatome does shingles occur in children?
sacral & cervical
151
what is Ramsay-Hunt syndrome?
vesicles & pain in auditory canal & throat
| facial palsy
152
what is ramsay-hunt syndrome due to?
irritation of the 8th cranial nerve
153
what symptoms are associated with irritation of the 8th cranial nerve?
deafness
vertigo
tinnitus
154
what is in the chickenpox vaccination?
live attenuated vaccine
155
what is used as a vaccination for shingles?
Same attenuated VZV used in chickenpox vaccine can be used in high titre preparation in elderly to reduce impact of shingles
156
what does herpes simplex virus cause?
primary gingivostomatitis
| extensive ulceration in & around the mouth
157
who does herpes simplex virus affect?
pre-school children
158
how long does herpes simplex virus last?
around a week
159
what happens in recurrence of herpes simplex virus?
a blistering rash at the vermillion border which can spread
160
what does herpes simplex virus type 1 cause?
main cause of oral lesions, causes half of genital herpes & causes encephalitis
161
what does herpes simplex virus type 2 cause?
is a rare cause of oral lesions, causes half of genital cases & causes encephalitis/disseminated infection
162
which antiviral is used in VSV & HSV?
aciclovir
163
which lab tests are done to confirm VSV & HSV?
- swab with viral transport medium
| - antibody tests
164
what does erythema multiforme look like?
target lesions with erythema
165
what can trigger erythema multiforme?
many triggers including drug reactions & some infections (HSV & mycoplasma pneumoniae bacterium)
166
what does molluscum contagiosum look like?
fleshy, firm, umbilicated pearlescent nodules 1-2mm diameter
167
how long does molluscum contagiosum last?
self-limiting but take moths to disappear
168
which age group is molluscum contagiosum common in?
common in children
169
how can molluscum contagiosum be treated?
with local application of liquid nitrogen
170
which virus causes warts?
human papilloma virus
171
which age group are warts commonest in?
children
172
how long do warts last?
self-limiting & uncomplicated
173
what other disease does HPV cause?
genital warts
cervical cancer
head & neck cancer
174
what does herpangina cause?
blistering rash at back of mouth
175
what is herpangina caused by?
enterovirus e.g. cocksackie virus & echovirus
176
how long does herpangina last?
self-limiting
177
how is herpangina diagnosed?
swab of lesion & sample of stool for enterovirus for PCR
178
who is hand, foot & mouth disease common in?
in children, usually family outbreaks
179
what causes hand, foot & mouth disease?
enteroviruses
180
what does erythema infectiosum look like?
a slapped cheek
181
what happens as the facial rash fades in erythema infectiosum?
a lacy macular rash on the body appears
182
what complications can occur in parvovirus B?
spontaneous abortion
aplastic crises
chronic anaemia
183
what is an aplastic crisis?
sudden drop in haemoglobin seen in patens with short red cell like span
184
how is parvovirus B confirmed in the lab?
by antibody testing
185
what is orf?
a virus of sheep, "scabby mouth"
186
what does orf look like?
firm, fleshy nodule on hands
187
who is orf found in?
farmers
188
how long does orf last?
self-limiting
189
how orf confirmed, clinically or by the lab?
clinically
190
how many phases of infection are there of syphilis?
3
191
describe the primary phase of infection of syphilis
chancre - painless ulcers at site of entry
192
describe the secondary phase of infection of syphilis
- red rash over body
- prominent on soles of feet & palms of hands
- "snail track" ulcers on mucous membranes
193
describe the tertiary phase of infection of syphilis
affects the CNS, CVS etc
194
what is syphillis due to?
sexually transmitted infection with bacterium treponema pallidum
195
how is syphilis diagnosed?
by blood tests or swab of chancre for PCR
196
how is syphilis treated?
using injections of penicillin
197
what is the vector used in lyme disease?
ticks
198
what causes lyme disease?
borrelia burgdoferi
199
how does lyme disease present early on?
erythema migrans
200
how does lyme disease present later on?
heart block
nerve palsies
arthritis
201
how do you treat lyme disease?
doxycycline or amoxicillin
202
when is lab confirmation of lyme disease used?
mainly for late presentations
203
what is the lab confirmation for lyme disease?
blood test for antibody to organisms
204
what is the pathogenic feature of lyme disease?
the rash; erythema migrans
