Microbiology Flashcards
(260 cards)
1
Q
Why do we culture blood?
A
to look for bacteraemia - it is normally bacteria free without bacteria flora
2
Q
How can blood be contaminated?
A
patient’s skin, surface of the items used to take the culture, fingers of the person taking the blood, laboratory
3
Q
How long does it take for a blood culture to identify an organism?
A
1 day to do gram stain and coccsu/bacillus
2-3 days to identify organism and assess whether this is likely to be a contaminant
4
Q
Why are contaminants a problem?
A
give wrong treatment, waste of money, side effects for patients, unnecessary equipment, increased length of stay, mislead clinicians, not always able to identify whether it is a contaminant or not, don’t meet contamination targets
5
Q
What organism is resistant to all B lactams?
A
MRSA
6
Q
Disadvantage of using B lactam antibiotics?
A
can predispose to C.difficile and colonization with resistant bacteria e.g. MRSA, many people report allergies to this group, especially penicillin
7
Q
What is the most widely used class of antibiotics and how do they work?
A
B lactams which includes penicillins, cephalosporins, carbapenems and combinations - bind to cell wall and inhibit cells wall sunthesis
8
Q
Two main types of penicillins?
A
amoxicillin, flucloxacillin
9
Q
What antibiotic is used for enterococci and H.influenzae?
A
amoxcillin - but most enterobacteria are resistant to it
10
Q
What is flucloxacillin used for?
A
anti staphylococcal agent as stability to penicillinase
11
Q
What are B lactamase inhibitors used for?
A
bacteria resistance is through B lactamase production, so these antibiotics prevent this resistance, so use combinations e.g. co-amoxiclav, tazocin
12
Q
What are monobactams used for?
A
e.g. Aztreonam, for gram negative bacilli, including pseudomonas and preferably aerobes, safer for C.diff
13
Q
What are carbapenems used for?
A
e.g. imipenem for very broad spectrum hospital acquired infections
14
Q
Disadvantages of carbapenems e.g. imipenem?
A
expensive, CI in CNS disorders and can predispose to C.diff
15
Q
What are cephalosporins used for?
A
e.g. cefotaxime, ceftazidime for gram negative activity, good CNS penetration and good anti pseudomonal
16
Q
What are glycopeptides used for?
A
e.g. vancomycin for gram positive only and reserved for serious, resistant ones e.g. MRSA (Iv only and toxic)
17
Q
What are macrolides used for?
A
e.g. erythromysin, clarithromycin for staph and strep activity, used to soft tissue and throat infections if allergic to penicillins (no gram negative cover)
18
Q
What are lincosamindes used for?
A
e.g. clindamycin for staph, strep and anaerobes and C.diff and PMC good bone concentrations and well absorbed orally
19
Q
What are tetracyclines used for?
A
mild MRSA infections and chlamydias
20
Q
What are aminoglycosides used for and how do they work?
A
e.g. gentamicin for enterobacteriaceae, pseudomonas and staphylococci, synergy with cell wall antibiotics against streptococci and enterococci - inhibit ribosomal activity and protein synthesis
21
Q
Disadvantages of aminoglycosides?
A
more toxic than glycoproteins so nephro and oto toic levels must be monitored carefullly
22
Q
What is fusidic acid used for?
A
serious anti staphylococcal agents e.g. osteomyelitis, only used in combination
23
Q
What is oxazolidinone used for and how does it work?
A
grampositive including MRSA and VRE - inhibits bacterial protein synthesis and blocks initiatio complex formation
24
Q
Disadvantages of oxazolidinone?
A
only 1 class e.g. linezolid and are expensive and can cause bone marrow suppression if used for >2 weeks
25
What are nuclei acids/quinolones used for and how do they work?
e.g. ciprofloxacin - UTIs, enterobacteriacease pseudomonas and staph - inhibitt DNA gyrase
26
What is rifampicin used for and how do they work?
TB and general Staph's and meningitis prophylaxis - must be used in combination - interfere with nuclei acid synthesis or function
27
What is metronidazole used for?
anti anaerobic for bacteria and protozoa
28
What likely organisms are seen in UTIs?
e coli, staph sparophyticus, enterococci
29
Antibiotics for UTIs?
trimethoprim, amoxicillin, clavulanate, cephalosporin
30
Likely organisms to cause COPD?
Hinfluenzae, pneumococcus, Moraxella catarrhalis
31
Treatment of COPD infection?
amoxicillin with clavulanate, tetracycline, trimethoprim
32
Likely organisms to cause pneumonia?
pneumococus
33
Treatment of pneumonia?
B lactams, erythromycin
34
Likely organisms in a wound?
staph aureus, strep pyogenes, anaerobes
35
Treatment of a wound?
flucloxacillin, erythromycin, co-amoxiclav
36
How can antibiotics be misused?
use broad spectrum when narrow are just as effective, treat for too long, treating with IV when oral is as effective, using combination when one is a effective, failure to use a dose appropriate for renal and hepatic function, using antibiotics for highly unlikely organisms, failure to step down organism once known
37
Dangers of antibiotic misuse?
adverse drug reactions which increases with multiple drug prescribing, harmful drug interactions, errors in prescribing monitoring, can cause super infection and antibiotic resistance
38
What is the difference between bacteriostatic and bactericidal?
bacteriostatic - prevents bacteria growth by inhibiting protein synthesis, DNA replication or metabolism, reduces toxin production
bactericidal - kills bacteria by inhibiting cell wall synthesis, good if poor penetration
39
Why do antimicrobials want a large MIC?
minimum inhibitory conc - to attach to more binding sites to inhibit bacteria
40
What factors must be considered in drug administration choice?
will it penetrate, pH of the site, is antimicrobial lipid soluble
41
How do bacteria resist antimicrobials?
change antimicrobial site by changing binding site configuration, destroy or inactivate the antimicrobal, prevent antimicrobial etery by modifying bacterial membrane porin channel site, numbers or selectivity, remove antimicrobial from bacterium using export pumps
42
How does bacterial resistance develop?
intrinsically naturally resistant so subpopulations can develop it too
acquired - not all subpopulations are equally resistant
43
Gram positive antimicrobial resistant bacteria?
MRSA, VRE
44
Gram negative antimicrobial resistant bacteria?
B lactamases, ESBL, carbapenenases, AmpC B lactamase resistant
45
What methods can be used to test antimicrobial resistance?
antimicrobial sensitivity testing, chromogenic plates, mechanism specific tests, genotypic methods, breakpoint plates
46
What is a pathogen?
an organism that is capable of causing disease
47
What is a commensal?
an organism which colonises the host but causes disease in normal circumsatnces
48
What is an opportunist pathogen?
only causes disease if host defences are compromiseed
49
What is pathogenicity?
the degree to which an organism is pathogenic
50
What is asymptomatic carnage?
when a pathogen is carried harmlessly at a tissue site where it causes no disease
51
Components to a bacteria?
capsule, cell wall, outer and inner membrane, pili, chromosome, may also have plasmids
52
What is the function of a capsule on bacteria?
super coated so difficult for phagocytes to ingest
53
What is used to stain acid fast bacilli?
Ziehl Neelsen stain
54
What colour is a gram positive stain?
purple/blue
55
What colour is a gram negative stain?
pink
56
What is the difference in gram positive and negative cell wall composition?
n = more lipopolysaccharide, with lipoprotein, less peptidoglycan with inner and out membrane
p = more peptidoglucan with lipoteichoic acid and cytoplasmic membrane
57
What is the idea bacterial environment?
temperature
58
What are the 4 stages of bacterial life?
lag, exponential (log), stationary, death
59
What is endotoxin?
component of outer membrane of bacteria produced by lipopolysaccharide gram negative, has non specific action, stable effect of heat, weak antigenicity and not convertable to toxoid
60
What is exotoxin?
secreted by gram positive (and negative), can be converted to toxoid, strong antigenicity, liable effect of heat and specific action
61
What is involved in a gram stain?
apply crystal violet stain to fix bacteria, add iodide to bind to crystal violet and help fix it to cell wall, decolourize with ethanol and counter stain with safranin (pink)
in gram negative, the decolourizze interacts with lipids and cells lose their lipopolysaccharide membrane and the crystal violet complex so appears pink
in positive, the decolourize dehydrate the cell wall and crustal violet is trapped in the multilayed peptidoglycan
62
Methods for infection control?
decontaminate medical equipment, single used items, manage peripheral and central IV lines, manage short term catheters, outbreak control plan, specific antimicrobial prescribing policies, personal protective equipment worn by all staff, dispose sharps into sharps bin, never res heath or bend needles or overfill sharps bin, hand hygeiene
63
What is an endogenous infection?
infection of a patient by their own flora, especially in hospitalised patients with invasive devices and surgical aptients
64
Prevention of endogenous infection?
good nutrition and hydration, antispepsis/skin prep where indicated, control underlying disease, remove linses and catheters as soon as clinically possible, reduce antibitotic pressue as much as clinically possible
65
What are protozoa?
eukaryotic organisms that consume bacteria, algae and microfungi
66
What are the 5 main protozoa?
flagellates - allows movement, reproduce by binary fision
amoebae - flow through cytoplasma, produced by pseudopodia
sporozoans - no locomotory extensions, most intracellular parasites and reproduce by multiple fission
ciliates - cilia beat rhythmically with macro and micro nuclei
microsporida - makes resistant spores, unique polar filament, coiled inside spore
67
What has malaria incidence increased?
parasite resistance, climate changes, increased travel to area
68
How do viruses cause disease?
virus causes invagination of the cell membrane and attaches to cell receptors and released into cell cytoplasm, carry nuclei acids and replicate using cells proteins and forms a defense mechanism
virus moves in vacuole and acidification causes a change in surface proteins of virus to release products, this replicates until the cell lysis or exocytosis so it can spread to other cells, budding causes parts of the virus to be pinched off
69
How does a virus cause damage?
direct destruction of host cells e.g. polio, modification of host cell structure or function e.g. rotavirus and HIV, damage through overreactivity of host in response to infection e.g. hepatitis B and C, damage through cell proliferation and immortalisation e.g. HPV, virus evasion of the host defences
70
What makes up a cell wall of fungi?
polysaccharides and chitin, most don't have a capsule, and the cell wall is the sterol rich cytoplasmic membrane
71
What are the different forms of fungi?
moulds, yeasts, dimorphic
72
Who are most at risk of getting a fungal infection?
immunocompromised, especially neutrophil deficient (those who are healthy only get superficial infections e.g. athletes foot)
73
What does the fungal cell wall stain with?
Gomorra methernamine silver of periodic acid schiff reagent as it is too weak for gram stain, KOH
74
How do yeasts and moulds repoduce?
yeasts - asexual budding
| moulds - spore formation
75
Shape of yeasts and moulds?
yeasts - round/oval
| moulds - tubular
76
How do yeasts and moulds grow?
yeasts - grow in tissue and bud as tubular forms as a pseudohyphae
moulds - grow by longitudinal extension and branch to form interwoven mycelium
77
What are the 3 types of fungal infection?
superficial mycoses - in skin, hair, nails, mucus membranes with yeast and ringworm
subcutaneous mycoses - pigmented fungi with septate dark brown cells singly or in clusters e.g. madura foot
systemic mycoses - primary or opportunist pathogens
78
Treatment of fungal infections?
drugs to target sterols in cell membrane, topical or systemic
antifungal therapy binds to serols in cell walls, destabalising it and inhibits RNA and DNA synthesis and inhibits ergosterol biosynthesis and mircotubule assembly
79
Examples of fungal infections?
candidasis - on mucous membranes of mouth and vagina, a commensal yeast that causes disease when microflora disturbed
ringworm - direct or indirect transfer of infection keratin e.g. athelets foot
aspergillois - spores in soils and ducts can be invasive, allergic or asperfillomia
cryptococcosis - capsulate yeast in immunosuppressed
80
Is microbacteria gram positive or negative?
weak gram positive with a high lipid ontent
81
How can mycobacteria cause infection
survive a long time in macrophages and are slow growing, so immunodeficient are susceptible
82
How does leprosy cause damage?
has granulomas formed as a response to try and contain mycobacteria, these can cause damage to nerves which means risk of tumour and burns and the nose can collapse
83
How do mycobacteria appear in a Ziehl Neelson stain?
turns red then destained to be blue
84
How long does it take to culture TB?
```
solid = 3-8weeks
liquid = 1-3 weeks - then can used mycobacteria growth indicator tube using flurometric detection
```
85
What does PCR do in TB culturing?
amplifies nucleic acids, purifies and concetratesTB, sonicates to release henomic material and performs PCR, rapid result and detects rifampicin resistance using fluorensence
86
What test is used to detect re-activity of T cells for TB
tuberculin skin test looks for cell mediated immune defense
87
Difference between lepromatous and tuberculoid leprosy?
LL - lesions full of bacilli, poorly formed granulomatus, extensive skin lesions, Th2 response
TL - tissue hypersensitivity and granulomatas, causing tissue damage, immune reaction, Th1 response and CD4+ T cell response, producing IFN-Y and TNF-a
88
4 drugs for TB treatment?
rifampicin, isoniazid, pyrazinamid, ethambutol for 2 months followed by INH and RIF for 4 months
89
Examples of gram positive cocci?
staphylococci, streptococci, enterococci
90
Examples of gram negative cocci?
neisseria and moraxella
91
Examples of gram positive bacilli?
actinomyces, bacillus, clostridia, diptheria, listeria monocytogenes
92
Examples of gram negative bacilli?
E coli, campylobacter, pseudomonas, salmonella, shigella, proteus
93
What is the catalase test?
to see if the microbe has catalase which destroys H2O2 and produces O2, if O2 is produced it is positive and is staphlococcus and it has catalase, it no O2 it is negative and streptococcus
94
Purpose of catalase test?
distinguishes between staphylococcus and streptococcus
95
What test is used on gram positive cocci?
catalase test
96
What test is used on staphylococci?
coagulase test
97
What is the coagulase test?
coagulase converts fibrinogen to fibrin and differentiates between staphylococcus aureus and staphylococcus epidemidis (positive is s.aureus and appears cream/yellow, negative is white)
98
How does s.aureus appear?
pigmented clusters, coagulated (solid), had DNAase
99
How does s.aureus cause disease?
high disease potential, pore forming toxin proteases. toxic shock syndrome toxin, spread by aerosal and touch and can colonize skin wounds
100
Treatment of s.aureus?
flucloxacillin (MRSA is resistant to B lactams though so needs vancomycin)
101
How does s.epidemidis appear?
non pigmented clusters, non coagulated, no DNAase
102
How does s.epidimidis causes disease?
low disease potential and s opportunistic and forms persistent biofilms
103
What test is done to distinguish streptococci?
haemolysis on blood agar
104
What are the 3 outcomes of haemolysis on blood agar and how do they appear?
beta haemolytic strep - clearing of agar around colonies due to strepolysin O and S production
alpha haemolytic strep (viridans strep) - greening of agar around the colonies due to H2O2 production
gamma haemolysis - no lysis
105
What test is done on beta haemolytic strep and how does it work?
The Lancefield test - serogroups antigenic gorup, differentiates according to surface antigens and their properties and the non coagulated one is the one to classify properties, producing A, B, C G
106
What is the likely diagnosis of group A Lancefield test?
s.pyogenes - causes tonsillitis, impetigo, scarlet fever, cellulitis
107
What test is done on alpha haemolytic strep?
optochin test
108
What are the results of the optochin test?
Put the disc on the bacteria and if bacteria moves away from the disc then it is sensitive (s.pneumoniae) and if it doesn't it is resistant (s.viridans)
109
What does strep viridans cause and where does it occur?
in oral dental canes and deep organ abscess, caused infective endocarditis
110
Where does strep. pneumoniae act on and what does it cause?
in oropaharynx, it has capsule, inflammatory wall constituents and cytotoxins causing impaired mucus trapping, causes hypomnaglobinaemia and is dependent on antibody to capsule
111
What infections does step. pneumoniae cause?
pneumonia, sinusitis and meningitis
112
Where are the sterile parts of the body?
blood, peritoneal cavity, CSF, joint, pleural fluid, urinary tract, lower resp tract
113
Where can norma flora culture?
mouth, skin, urethra, large intestine, vagina
114
What test is used on gram negative bacillus?
the appearance on MacConkey or CLED or XLD
115
What are the outcomes of appearance on MacConkey agar?
white (non lactose fermenting - shigella, salmonella, pseudomonas, proteus)
pink (lactose fermenting - enterobacteriacae (coliforms)
116
What are the outcomes on XLD agar?
red with black dots (fermenting xylose)
red (non fermenting xylose)
yellow (salmonella)
117
What test is done on non lactose fermenting bacteria?
oxidase test using a redox indicator
118
What are the results of an oxidase test?
blue as produces cytochrome c oxidase from bacterial ECT (positive - pseudomonas aeruginosa)
no colour change (enterobacteriaceae - proteus and shigella)
119
What test is done on oxidase positive pseudomonas sp.?
anti pseudomonal sensitivity test
120
What is the treatment of pseudomonas sp?
beta lactams
121
What tests are done on oxidase negative enterobacteriacae?
biochemical identification (API strip) and sensitivity strips
122
What test is done on lactose fermenting bacteria?
biochemical identification (API strip) and sensitivity strips
123
Which is the least selective agar?
blood agar so good for many bacteria
124
What is chocolate agar?
blood agar heated to 80c for 5 minutes to release nutrients into agar - means certain organisms dont grow as well
125
What is MacConkey agar used for?
to grow and differentiate gram negative bacilli with bile salts to inhibit positive, contains lactose and neutral red dye to strain fermenting and non fermenting
126
What is gonococcus agar used for?
contains growth factors to promote Neisseria and has antibiotics and antifungal agents to inhibit other growth
127
What is CLED agar used for?
non inhibitory growth medium to differentiate microoganisms in urine, classifying fermenting and non fermenting
128
What is Sabouraud's agar used for?
cultures fungi and uses bacteria with antibiotics
129
What is XLD agar used for?
very selective for salmonella and shigella with phenol red indicator so bright red at pH 7.4 and then turns yello
130
How can pathogens be distinguished from norma flora?
restrict it using plates in different atmospheres and temperatures with range of nutrients and using selective media
131
What does shigella cause?
4 types that lead to diarrhea
132
What does salmonella cause?
gastroenteritis and enteric fever and bacteraemia
133
What is the most common faculative anaerobe in the gut?
E.coli
134
What does E.coli cause?
cystitis, UTI, wounds infections
135
What the main forms of Neisseria?
Neisseria meningitidis and Neisseria gonorrhoea
136
What are the main bacteria that cause UTI?
E coli, klebsiella, pseudomonas
137
What is a common gram positive bacilli that is in neonates and elderly?
Listeria monocytogenes
138
Are staphylococci and streptococci chains or clusters?
```
staph = clusters
strep = chains
```
139
What is another name for s.pyogenes?
group A streptococci
140
What organism is oxidase test negative and causes dysentry?
shigellosis
141
What are the 2 methods of viral diagnosis?
virus detection or serology
142
What methods are used for virus detection?
electron microscopy, cytopathic effect and PCR (preferred)
143
What is and advantage and disadvantage of ECM and cytopathic effect for virus detection?
time consuming and a lot of effort and cannot be be used in modern labs, but are good for new viruses
144
What happens in PCR?
enzymes unzip DNA and RNA chains, make complementary copies with flourescent tags, and is then replicated and then the DNA can be measured by the flourescence which is only activated when bound to the chain
145
Advantages and disadvantages of PCR in virus detection?
very sensitive and quick, but liable to contamination and false positives, so you must have suspected the virus in the first place, making it difficult for novel viruses
146
What is serology?
the study and detection of antibody responses in the serum
147
What antibodies are seen after an acute infection??
IgM for up to 12 weeks after, then IgG later and is responsible for immunity
148
What different serology techniques are there?
complement fixation test, haemagglutination (inhibition), enzyme linked immunosorbent assay (ELISA), radioimmuo assay, immunofluoresence
149
Common enteroviruses?
rhinovirus, echovirus, coxsackie a and b
150
Common respiratory viruses?
influenza A/B, parainfluenza, RSV, coronavirus, rhinovirus, measle, rubella, metapneumonvirus, parvovirus, adenovirus
151
What samples can be used for diagnosis?
green viral swab, black charcoal swab, CSF, stool
152
What tests count WCC quickly?
CSF
153
What blood tests can be done?
FBC, blood film and yellow top for EBV serology
154
How long does it take for blood results to be available?
film - hours
pcr - next day
acute EBV serology - 1-2 days
155
Management of glandular fever?
supportive therapy, avoid contact sport for 6 weeks to avoid splenic rupture
156
What 3 markers can HIV tests detect in the blood?
antibody, antigen p24, HIV RNA
157
What happens if HIV test is negative?
may not be in window period, so screen again after window period
158
What happens in HIV test is positive?
confirm test inn the lab with a different assay
159
Treatment of CMV?
IV gangciclovir
160
Causes of UTI?
sexual intercourse, catheterisation, enlarged prostate, renal tract tumours, renal stones
161
What investigations are need in UTI?
mid stream urine, direct microscopy for pyuria, culture (which can show significant bacteriuria, doubtful significance or a contaminant), sensitivity testing (to find appropriate antibiotics)
162
What is a skin organisms that can colonise the perineium and seen in UTI?
staphylococcus saprophyticus (gram positive cocci)
163
What do leucocytes and nitrates in urine sample suggest?
UTI
164
How can gram negative bacilli appear on a CLED agar?
yellow (lactose fermenting)
| white (non lactose fermenting)
165
What antibitoics is E.coli pyelonephritis resistant and sensitive to?
```
r = amoxicillin
s = co amoxiclav
```
166
Why can't catheter bag urine be used for urinalysis results?
because all catheters have bacteria and white cells in, even without an infection
167
Benefits of CLED agar?
promotes UTI pathogens
distinguished lactose and non lactose fermenting
prevents proteus swarming
168
When should you treat asymptomatic bactriuria?
in pregnant women
169
What is erysipela?
intradermal skin infection
170
What causes erysipela?
group A beta haemolytic streptococcus and staphylococcus aureus
171
What is cellulitis?
a subcutaneous skin infection
172
What causes cellulitis?
group A beta haemolytic streptococcus (occasionally B, C, G) and staphylococcus aureus
173
In who are atypical organisms causing skin infections common?
IV drug users and immunocompromised
174
What organisms commonly cause skin soft tissue abscess?
staphylococcus aureus
175
What organisms commonly causes lung abscesses?
staphylococcus aureus, kelbiella pneumoniae, anaerobic organisms, mycobacterium tuberculosis
176
What organisms commonly cause liver abscesses?
gram negative, strep.milleri, anaerobes, entamoeba histolytica in tropic
177
What organisms commonly cause kidney abscesses?
e.coli and klebsiella
178
What organisms commonly cause bowel abscesses?
gram negative, anaerobes, strep.milleri
179
How does impetigo present?
itchy, growing in size spot on the face, it weeps and crusts
180
Treatment of impetigo?
flucloxacillin
181
What swab is most appropriate for impetigo?
black charcoal swab
182
What is impetigo commonly caused by?
staphylococcus aureus
183
How does celluilitis present?
erythematous, hot and tender skin, commonly of leg, fever, painful
184
What investigations should be done for cellulitis?
take blood from more than one sire on more than one occasion
185
Treatment of s.pyogenes?
penicillin/benzyl penicillin
186
What organism commonly causes cellulitis?
s. pyogenes
187
What does MRSA stand for?
methicillin resistant staphylococcus aureus
188
How is MRSA carriage identified?
chromogenic MRSA plate on swabs from the axillae and groin
189
What kind of antibiotic is vancomycin?
glycopeptide
190
Treatment of community acquired pneumonia?
amoxcillin
191
What pathogens atypically cause community acquired pneumonia?
chlamydophilia psittaci/pneumoniae
mycoplasma pneumoniae
coxiella burnetti
legionella penumophilia
192
How does pneumonia present?
increased HR and RR but low BP, cough, confusion
193
Treatment of legionella pneumophilia and why?
clarithrimycin or ciprofloxacin as atypical pathogens that cause pneumonia are not sensitive to amoxicillin
194
What investigation in done in chronic bronchitis?
sputum
195
What does gram negative with white colonies of chocolate agar suggest?
H.influenzae
196
What is the treatment of H.influenzae
amoxicillin and doxycycline
197
What agars is H.influenzae testing on?
blood agar and chocolate agar
198
Why is chocolate agar needed for H.influenzae?
the heating of the agar causes release of nutrients that H.influenzae needs for its fastiduous growth, X and V plates have been added too and it only colonies around the XV disc as both are needed, confirming H.influenzae
199
What 2 stains are used to detect mycobacteria?
ziehl neelsen stain and auramine phenol flourescent stains
200
Why does TB not show anything on gram stain?
has a different cell wall from other bacteria
201
What culture medium is used in TB and why?
Lowenstein Jensen Slope - as MTB divides very slow and may take up to 6 weeks to grow
202
What is seen on TB biopsy?
caseating granulomata
203
How can sputum be obtained?
induced or bronchoalveolar lavage
204
What will sputum show in HIV?
cysts of P.jiroveci
205
Treatment of P.jireoveci?
co-trimoxazole
| prednisolone if significant type 1 resp failure
206
CD4 count in HIV?
207
Treatment of pseudomonas in bronchietasis exacerbatio?
antipseudomonal beta lactam or fluroquinolone
208
What medium are fungus grown on?
Sabourad's agar
209
Examples of fungus infections?
aspergillus fumigatus and candida albicans
210
What are the main bacterial causes of meningitis in neonates?
e.coli, group b streptococcus and listeria monocytogenes
211
What are the main bacterial causes of meningitis in infants?
neisseria mengitidis, H.influenzae, Streptococcus pneumoniae
212
What are the main bacterial causes of meningitis in young adults?
neisseria meningitidis, streptococcus pneumoniae
213
What are the main bacterial causes of meningitis in elderly?
streptococcus pneumoniae, neisseria meningitidis and listeria
214
What are the main viral causes of meningitis?
mumps, echo, coxsackie, enteroviruses, HSV, lymphocytic chorio meningitis virus, poliovirus
215
Symptoms of meningitis?
stiff neck, photophobia, headache, rash
216
Investigations in meningitis?
CSF, bloods, nose and throat swabs, stool, serology
217
Symptoms of encephalitis?
lethargy, fatigue, decreased consciousness, fever
218
Main viruses that cause encephalitis?
HSV, varicella zoster virus, parvovirus, HIV, mumps, measles
219
Investigations in encephalitis?
CSF, PCR, serology of blood to detect antibodies
220
Treatment of H.influenzae in babies?
IV cefotaxime or ceftrixone
221
What are 25% of women at childbearing age asymptomatically carrying in their genital tract?
group b streptococcus
222
Who is at risk of listeria monocytogenes (group B strep)?
pregnant women, neonates, elderly, immunodeficient, chronic glucocorticosteroid use, DM
223
If at risk of listeria monocytogenes, what additional antibiotic therapy should be used with cefotaxime in meningitis treatment?
IV amoxicillin
224
Which organism that causes meningitis grows better on chocolate agar than blood agar?
Neisseria meningitidis
225
Who needs to be informed of a meningitis outbreak?
public health england, close contacts for prophylaxis
226
What is used for meningitis prophylaxis?
single dose of oral ciporflaxcin or 2 day course of oral rifampicin
227
What does a predominantly lymphocytic CSF suggest in CNS diagnosis?
viral meningitis or encephalitis
VIRUS
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Treatment of herpes simplex encephalitis?
IV antibiotics and IV acyclovir
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What is the most common cause of encephalitis?
herpes simplex virus
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How can you confirm a herpes simplex virus?
PCR
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Bacterial causes of diarrhea?
e.coli, v.cholerae, s.sonnei (dysenteriae)
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Organisms from food poisoning causing diarrhea?
salmonella, campylobacter, cl.perfringens, B.cereus, St.aureus
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Antibiotic causes of diarrhea?
cl.difficile, st.aureua, c.albicans
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Viral causes of diarrhea?
rotavirus, SRSV
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Systemic infections causing diarrhea?
s.typhi, s.paratyphi, h.pylori
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How can salmonella be further classified?
presence of different O (oligosaccharide) and H (flagellar) surface antigens, using agglutination tests and are classified using the Kauffman White scheme
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What investigations are done on stool samples for persistent diarrhea?
wet prep and staining with fluorescent antibodies
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What organism are young children and immunocompromised at risk of that causes watery diarrhea?
c.parvum (detected in stool sample)
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What pathogens can be detected in a stool sample?
c.parvum, entamoeba histolytica, giardia lamblia, helminths
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Treatment of rota virus gastroenteritis?
supportive, and isolation
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How do antibiotics cause diarrhea?
increased risk of infection from PPI acid suppression
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Treatment of antibiotic associated diarrhea caused by C.diff?
stop the antibiotics, oral vancomycin or metronidazole, isolationg
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Antibiotics for ruptured appendicitis?
CoAmoxiclav or cefuroxime and metronidazole
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What is the purpose of an Mz disc?
it contains metronidazole which confirms the presence of anaerobic bacteria if it prevents growth
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Antibiotics for anaerobic bacterioides?
metronidazole
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Antibiotics for ascending cholangitis?
co amoxiclav
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What is dysentery?
inflammatory disorder of GI tract with blood and pus in the faeces with pain, fever, abdominal cramps, usually caused from disease of the large intestine
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Gram negative bacilli organisms in the GI tract?
salmonella, shigella, e.coli, campylobacter jejuni, helicobacter pylori
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What is infectivity?
the ability to become established in a host
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What is virulence?
the ability to cause disease
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What is invasiveness?
capacity to penetrate mucosal surface to reach normally sterile sites
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What is a microbiome?
the totality of microorganisms, gentic elements and enviromental interactions
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metagenomomics?
the use of genetics to describe microoragnisms diversity
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What are the different types of adhesions that help bacteria bind to mucosal surfaces?
fimbriae, non fimbrial proteins, lipid, glycosaminoglycans, lectins of viruses and parasites, miscellaneous viral capsids
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Virulent factors in bacteria?
pili for adherance to mucosal surface
motility to reach mucosal surfaces
IgA protease for IgA cleavage
iron binding proteins to trap iron
capsule to prevent phagocytosis and complement deposition
antigenic variation for evasion of antibodies
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Types of toxins?
ADP ribosylating, adenylate cyclase, RNA gangliosidase, metalloproteiniase, cholesterol dependent
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What are superantigens?
bacteria and viruses can produce antigens that bind outside the peptide groove of the T cell receptor to stimulate a large number of T cells e.g. EBV
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Where are the 2 places that toxins can be?
chromosomal or on plasmids
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What is C.diphtheriae?
a toxin spread by droples that inhibits protein synthesis and toxin recognition on Elek plate, preventing with vaccination
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S.pneumoniae virulence factors?
polysaccharide capsule, polyvalent vaccine with 23 types, inflammatory wall constituents with teichoic acid and peptidoglycan, releases the cytotoxin pneumolysin
