Basic Bacteria Flashcards
(99 cards)
1
Q
Bacteroides fragilis
Gram stain
Growth conditions
A
Gram negative
Anaerobic
2
Q
Clostridium
Gram
Growth conditions
A
Gram positive bacilli
Anaerobic
3
Q
What bacteria look like safety pins on gram stain?
A
Burkholderia pseudomallei
Burkholderia mallei (glanders)
Pasturella
Yersinia pestis
4
Q
Is proteus lactose fermenting?
A
Proteus is NON LF
5
Q
Is proteus catalase positive
A
Yes
6
Q
What test differentiates salmonella from proteus
A
Proteus is urease positive
Salmonella is negative
7
Q
TSI tubes
What is alkaline / alkaline (red/red)
What is yellow top / red bottom
What is yellow /yellow
A
Red red = pseudomonas or acinetobacter
Yellow / red bottom / no gas bubbles = shigella, serratia
Yellow / red bottom / gas bubbles = salmonella proteus
Yellow /yelow = E. coli, enterobacter, klebsiella
8
Q
What prevents toxo going across placenta?
What is first line treatment for treating toxoplasmosis? With dosing
What if allergic reaction?
A
Spiramycin
Pyrimethamine 200mg loading dose then 50–70mg daily, plus sulfadiazine 1-1.5g QDS, and folinic acid (calcium folinate) 10-15mg daily
Allergy likely to sulphur, so give pyrimethamine folinic acid and clindamycin
9
Q
What two things are diagnostic of UTI in kids?
A
Isolating same organism in two different samples
Greater than or equal to 10^5 CFU per mL of pure growth (but sometimes 10^4 or 10^3 could be suggestive too)
10
Q
What is CLED used for, what’s the indicator
A
Cystine lactose electrolyte deficient agar.
Electrolyte deficient stops proteus swarming.
Bromothymol blue is the indicator
11
Q
What antibiotics is proteus resistant to?
A
Colistin
Nitrofurantoin
Tigecycline
Polymyxin B
Imipenem
12
Q
What are the birds on a wire microconidia suggestive of?
A
Trichophyton rubrum
13
Q
How to you define mild, moderate, severe, life threatening c diff?
A
Mild <3 loose stools, no raised WBC
Moderate 3-5 loose stools, <15 WBC
severe, >15 WBC, acute increase serum creatinine greater than 50% baseline, fever >38c
Life threatening signs of colitis, hypotension, partial or complete ileus, toxic megacolon
14
Q
What is the mechanism of action and dose of fidaxomicin
A
Inhibits bacterial RNA polymerase
Macrocylic antibiotic
200mg BD fidaxomicin
15
Q
What is XLD agar and what is the indicator
A
Xylose lysine deoxycholate
Good for salmonella vs shigella
Phenol red
16
Q
What should you do if ceftolozane/tazobactam mic >2 in pseudomonas
A
Send to ref lab
17
Q
What is acid fast (pink) oval shaped oocyst , causes watery diarrhoea in immunosuppressed pts and can be treated with CoT?
A
Cystoisospora belli
Oocysts in stool are acid fast
Tropical
18
Q
Three risk factors for GBS in pregnancy
A
Previous GBS
preTERM baby
Fever
PROM
Discovery of maternal GBS carriage in pregnancy
Suspected intrapartum infection
19
Q
What is the treatment and dosing for GBS in pregnancy?
A
Intrapartum antibiotics IAP
IV benzylpenicillin (pen G) 3g asap once labour starts, followed by top up doses of 1.5g every 4 hours until birth
No need if C-section as will get broad spectrum antibiotics anyway
20
Q
Empirical treatment for aspergillus abscess drug and dosing
A
Voriconazole 6mg/kg BD, for first two doses, then 4 mg/kg BD
21
Q
Gram positive long rods, grows in both aerobic and anaerobic bottles, alpha haemolytic on BA,
What is it
What’s it intrinsically resistant to ?
Is it cat pos or cat neg?
A
Lactobacillus
Vancomycin
Catalase negative
22
Q
What disease does rickettsia prowazekii cause?
How is it transmitted?
A
Gram neg obligate intracellular
Epidemic typhus
Faeces of body lice
23
Q
What is the cause of trench fever?
A
Bartonella quintana
Transmitted by human body louse
24
Q
Who gets prophylaxis due to significant contact with iGAS?
A
High risk contacts only get phenoxymethylpenicillin (penV) 10d course (if allergy, macrolide, Azithromycin 5d)
- 75+ yrs old
- > = 37 weeks gestation
- within 28 days of giving birth
- within first 28 days of life
- if you have chicken pox in the 7d before index case iGAS diagnosis up to 48 hrs after iGAS case has antibiotics
25
Mechanism of action of tigecycline
Glycylcycline antibiotic
Target 30s
Inhibits protein synthesis
26
Daptomycin mechanism of action
Cyclic lipopeptide
Binds to bacterial cell membranes causing rapid depolarisation , creates holes.
27
What organisms can cause mucormycosis
Lichtheimia corymbifera (zygomycota phylum)
Rhizopus oryzae
Mucor
(Rhizopus and Mucor are both distinct genera within the order Mucorales)
28
Gram stain fusobacterium necrophorum
Disease it causes
Anaerobic nonspore gram negative pleomorphic rod
Causes Lemierres syndrome (oropharyngeal infection, can be fatal) typically in previously healthy young adults
Should drain collection where possible
29
Empirical treatment for candida abscess
Liposomal ampho B 3mg/kg/day
Or
Caspofungin 70mg IV OD, followed by 50 mg IV OD daily after
30
Empirical treatment for mucormycosis
Liposomal ampho B
5-10mg/kg/day
31
Should you attempt to aspirate a cerebral abscess if you are suspicious of toxoplasma?
No
32
Empirical treatment for community acquired brain abscess
If no pen allergy
If pen allergy
If anaphylaxis
If concerned about pseud
If no pen allergy:
Ceftriaxone 2g BD
Metronidazole IV 500 mg TDS
IV vancomycin 15-20mg/kg BD, (aiming for 15-20 mg/L serum levels)
If pen allergy but not anaphylaxis
Meropenem 2g TDS
Vanc 15-20 BD
If pen anaphylaxis
Cipro IV 400mg BD
Metro 500 mg TDS IV
Vanc 15-20 BD
If pseudomonas is of concern (post op, post neurosurgery, otogenic)
Ceftazidime 2g TDS and metro and vanc
Or
Mero 2g TDS and vanc
33
What organism can cause brain abscess post near drowning
Scedosporium apiospermum
Scedosporium boydii
34
What organism should you consider in a patient from SE Asia with liver abscess?
What are particular risk factors and genes?
Hypervirulent hypermucoviscous klebsiella pneumoniae (serotype K1 and k2)
Particularly in diabetic patients
Can spread and cause endopthalmitus and brain abscess
magA is a gene for K1 capsular serotype which is more resistant to phagocytosis
rmpA regulates hypermucoviscocity
Can do ‘string test’, touch colony on plate does it stretch from plate 5mm or more like a string attached to the agar?
35
What gram stain is rhodococcus
Rhodococcus equi is a gram positive coccobacillus, found in dry dusty soil. Can cause pneumonia in foals.
36
What is the most common organism to cause brain abscess?
Strep viridans (strep anginosus, mitis, sanguinus, saivarius, mutans)
Mainly anginosus (which includes S anginosus, S intermedius, S constellatus)
2nd most common is anaerobes like bacteroides, prevotella, fusobacterium
Or S aureus (post trauma)
Pseud
Enterobacterales (post ear infection)
37
First line treatment for chlamydia
Ideal swab
7d doxycycline 100mg BD
Test of cure only for rectal infection
Vulvovaginal swab for women
First catch urine for men
38
First line treatment gonorrhoea
Swab type
Ceftriaxone 1g OD IM single dose
(Or if known to be sensitive then could give 500mg oral cipro one dose only)
Vulvovaginal swab
First catch urine
39
What can chronic infection with schistosomia haematobium lead to?
Bladder cancer
40
How do viridans strep look on BA?
Alpha haemolytic
41
What is the treatment for neurocysticercosis?
Albendazole 15 mg/kg/day in 2 divided doses for 10-14 days
With corticosteroids
dexamethasone 0.1 mg/kg/day
Or prednisolone 1mg/kg/day
Or
Praziquantel 50 mg/kg in three divided doses 10-14 days
42
What is the treatment for cryptococcus brain abscess?
Drugs and dosing
Liposomal ampho b
AND
flucytosine 150 mg/kg/day orally in divided doses every 6 hours
OR
fluconazole 400 mg once daily IV
Treat 6-8 weeks with serial neuroimaging
You don’t have to but it’s good practice to test for dihydropyrimidine dehydrogenase deficiency before giving flucytosine (risk of life threatening drug toxicity)
43
What is the treatment for brain abscess caused by nocardia
Cotrimoxazole 5mg/kg IV BD
and meropenem 2g TDS
+ amikacin 15 mg/kg/day
(Amikacin achieves poor cns conc so good to give in addition to mero and cot as triple therapy just in case)
Linezolid is another option instead of amikacin…
Usually use at least two drugs as infection has a high tendency to reoccur.
Maintenance therapy should be continued if pt remains immunosuppressed
Multiple abscesses are more common in nocardia sis rather than bacterial abscesses …
44
What are the different routes of infection with tænia solium
Ingestion of eggs, can lead to neurocysticercosis
Ingestion of cysticerci (larval form in meat) can lead to adult tapeworm forming in small intestine
45
What is the main pathogen of nocardia?
What’s the gram stain show?
What’s the one that is R to a lot?
Nocardia asteroides complex
Gram positive branching beaded filaments
Slow growing culture can take up to 6 weeks
Species ID is important, as a newer emerging one called N farcinica which is associated with disseminated infection and CNS inf and is R to 3rd gen cephalosporins
46
What ate the risk factors for nocardia brain abscess
Solid organ transplant pts (especially lung transplants)
HSCT pts
HIV
Cancer
Diabetes, Copd, etoh etc
47
Are nocardia catalase positive
Yes
48
Nocardia are oxidase…
Négative
49
Are nocardia urease pos?
Yes
50
What stain is good for weakly acid fast organisms
Modified Kinyoun stain
It uses a weaker acid decolouriser, like sulphuric acid (instead of stronger hydrochloric acid in the original Kinyoun stain).
This allows ID of weak acid fast
Nocardia
Cryptosporidium
Nocardia and cryptosporidium do not readily hold carbol fuschin stain when exposed to strong acids, but will retain if exposed to weaker acids
51
What is the treatment for CNS toxoplasmosis?
Pyrimethamine 200 mg once on the first day, followed by 75 mg orally once a day after
Plus
Sulfadiaxine 1500 mg QDS
plus
Folinic acid (calcium folinate)
Or
Cotrimoxazole 5 mg/kg oral BD
52
Side effects of cotrimoxazole
Can significantly increase serum potassium levels leading to hyperkalaemia
Can cause muscle cramps, irregular heart beat etc
Mainly due to trimethoprims action on the kidneys, impairing elimination of potassium
53
Main species of cryptococcus
Fungus
Cryptococcus neoformans (more common in immunosuppressed)
Cryptococcus gattii (more common in tropics, can infect healthy humans and animals)
54
What is the cause of valley fever
Dimorphic fungi, soil
Coccidiodies immitis (California)
Coccidiodies posadasii (other locations)
55
Main side effect of fluconazole
Hepatotoxicity
Can raise transaminases and rarely even cause liver failure
Can also prolong QT interval
56
Main side effects of flucytosine
Monitor FBC and LFTS to check for bone marrow suppression, hepatotoxicity, renal toxicity
Excreted renally so if kidneys are impaired, the risk of toxicity increases
Need to dose adjust in renal impairment
57
Mechanism of action and
Side effects of amphotericin b
Binds to ergosterol which leads to formation of pores and ion leakage, fungal cell death
Polyene
Can cause kidney failure (nephrotoxic), liposomal form is slightly less nephrotoxic
Monitor hepatic function, renal function, serum electrolytes.
Can cause electrolyte imbalance by increasing renal tubular permeability leading to potassium and magnesium wasting through the kidneys (hypokalaemia and hypomagnesemia)
58
What is a possible side effect of pyrimethamine
It is a folic acid antagonist and so can cause bone marrow suppression.
Pyrimethamine inhibits the dihydrofolate reductase (part of the folate acid synthesis pathway)
That’s why you give it with folinic acid (calcium folinate) (aka leucovorin calcium)
59
Why is imipenem given with cilastatin?
Imipenem is rapidly deactivated by human renal dehydropeptidase.
Cilastatin inhibits the dehydropeptidase to increase half life of imipenem
60
What class of antibiotics can cause cardiotoxicity?
Macrolides
They can block potassium channels in the heart
Prolong QT interval and lead to sudden cardiac death?!
61
What is the mechanism of action of atovaquone
Inhibits the mitochondrial electron transport chain in parasites
62
What is Romana sign?
Trypanosoma cruzi
Eyelid swelling
Chagas disease
63
How do you diagnose chronic Chagas’ disease?
The WHO recommends serology testing on two separate assays that are based on different formats or antigens.
64
What is first line treatment for chagas and when is treatment recommended
Benznidazole is first line, 60 days, a complete blood count is recommended after 21 days to monitor for leukopenia
2nd line is nifurtimox
Treatment is recommended for
- acute infection regardless of pt age
- infants with congenital inf
- women of child bearing age (to prevent vertical transmission, but shouldn’t treat during pregnancy)
- all cases of reactivation during immunosuppression
65
66
What is loefflers syndrome
A transient lung condition where eosinophils accumulate in the lungs in response to a parasitic infection.
It’s self limiting
Pulmonary eosinophilia mimics CAP and asthma
Can see transient radiographic infiltrates
Ascaris lumbricoides
Strongyloides stercoralis
Dirofliaria
67
What is the name of the itchy skin condition caused by strongyloides
Larva currens
Distinctive form of creeping eruption, resulting from rapid migration of larvae in subcutaneous tissue
Commonly affects perianal region or thighs
It’s distinguished from larva migrans (which is caused by hookworm larvae) as currens strongyloides moves quickly 5-10cm a day, whereas migrans 1-2 cm per day
68
What is the treatment for strongyloides and when is it contraindicated?
Ivermectin
0.2 mg/kg orally as a single dose for 1-2 days
Can’t give if pt also has loaloa infection (as it can cause encephalopathy)
River blindness is caused by onchocerciasis (ivermectin is also used to treat river blindness)
Loa loa causes microfilariasis (if you have high loa loa burden, ivermectin can cause a big bad reaction so best avoided in areas with both loa loa and river blindness…?)
69
How do you report clindamycin and enterococcus?
And enterococcus and cotrimoxazole
Report clindamycin as resistant or do not report it at all.
Even if it appears sensitive.
Resistance is usually due to LinB gene.
There are no EUCAST breakpoints
EUCAST also has no breakpoints for CoT and enterococci, it says it’s unable to predict susceptibility of enterococci and trimethoprim or cot
70
Why do enterococci have a reduced affinity for beta lactams?
They have a modified PBP5 which confers low affinity for most beta lactams.
Cephalosporins are completely resistant for all enterococci!
However amox still works for ent faecalis.
71
What does ertapenem NOT cover?
Enterococci
Staph epi
MRSA
Pseudomonas
Acinetobacter
72
What does papilloedema mean
Swelling of the optic disc at the back of the eye, typically due to increased intracranial pressure
73
How do azoles work
Inhibit ergosterol synthesis by inhibiting 14 a demethylase enzyme which converts lanosterol to ergosterol
74
Biochemical tests for h pylori
Catalase positive
Oxidase positive
Urease positive
Motile
Produces h2s
75
Ideal pre trough teicoplanin levels for SSTI/CAP and bone/joint infections and IE
15-30 mg/L ssti
20-40 mg/L bone joint
30-40 mg/L endocarditis
76
What is candidozyma auris intrinsically resistant to?
Fluconazole
(And most strains are resistant to amphotericin b)
77
What IPC precautions are needed for c auris
Contact (gloves and apron)
Side room
Hand hygiene soap and alcohol gel
(Long sleeve gown if prolonged pt contact)
Review use of medical devices (reduce risk of invasive disease)
Use single use equipment where possible
Clean 1000 ppm chlorine which is effective
Conduct retrospective and prospective lab surveillance for confirmed or suspected c auris, look back 4 weeks to check any weird fungi isolates, and ID all candida to species level for next 4 weeks
Use dedicated staff to care for pt, particularly in outbreak settings
78
What is first line treatment for plague?
Which type of plague is a HCID
Ciprofloxacin 750mg BD 10-14 days
(Or gentamicin)
Pneumonic plague is HCID
Fleas on rats bite humans GNR safety pin HG3
79
Define HCID
Acute
High fatality
May not be effective tx
Difficult to detect
Able to spread easily
Can be either respiratory HCID or contact HCID
80
What genes carry linezolid resistance and are they transmissible?
OptrA
poxtA
cfr and cfrB
Transmissible linezolid resistance genes, can be seen in enterococci
Plasmid
81
How do you treat NVE enterococcus (nonHLAR)
6 weeks amox and Ceftriaxone
Or
2 weeks amox and gent
82
Who gets VZIG
Neonates exposed to chickenpox within one week of delivery, either in utero (maternal infection) or post delivery
(Or if oral antivirals are contraindicated due to malabsorption or renal toxicity, or because the pt is less than 4 weeks of age)
Exposed Neonates 7 d before to 7 d after also get Aciclovir as PEP up to 21d post delivery
83
What is the infectious period for VZV
Chickenpox
24 hrs before rash to 5d after rash appears
If immunosuppressed it’s until all lesions have crusted over
Shingles
Is from the onset of rash until all crusted over
Shingles is only considered infectious is
- disseminated shingles
- immunocompetent with exposed shingles
- immunosuppressed with localised shingles anywhere on the body (as viral shedding may be higher)
Immunocompetent person with covered shingles is not considered infectious.
84
What counts as close contact for chickenpox
Face to face conversation
Those in same small room for 15+ mins
Immunosuppressed contacts on large open wards where airborne transmission at a distance can occur
85
Appropriate aciclovir and valaciclovir dosing for ages (PEP VZV)
Neonate
Oral Aciclovir 20mg/kg QDS given asap
<2 years
Oral Aciclovir 10mg/kg QDS d7 - d14
<18 years
Oral Aciclovir 10mg/kg QDS (max 800 mg) d7 - d14
Or
Oral Valaciclovir 20mg/kg TDS (max 1000mg) d7 - d14
Adults
Oral Aciclovir 800mg QDS d7 - d14
Or
Oral valaciclovir 1000mg TDS d7 - d14
86
Mechanism of action Aciclovir and valaciclovir
Aciclovir is prodrug.
It’s phosphorylated first by viral thymidine kinase (found in herpesviridae)
Then phosphorylated twice more by cellular kinases
To become aciclovir triphosphate
Which is a guanosine nucleoside analog.
It competes with deoxyguanosine triphosphate to be incorporated into the growing viral DNA chain by viral DNA polymerase.
Aciclovir triphosphate lacks 5’ hydroxyl group so it causes chain termination.
Valaciclovir is prodrug form and eventually becomes Aciclovir triphosphate too
87
What is the name for varicella zoster immunoglobulin for I.v. administration and when do you give it
Varitect CP
You give it as a SINGLE dose for neonates exposed to VZV either 7 days before (via maternal inf) or 7 days after birth.
The product should be given as a slow infusion.
Give asap and no longer than 10 days after exposure
neonates also get Aciclovir
(Valaciclovir is not licensed for neonates)
You get it by contacting UKHSA rigs (rabies and immunoglobulin service)
If there are delays, you can give IVIG instead
88
What is the risk of chickenpox in pregnancy
In first 20 weeks - fetal varicella syndrome (microcephaly, cataracts, growth retardation)
In later pregnancy; can cause severe maternal disease
89
Mechanism of action of echinocandins
Inhibit b-d-glucan synthase enzyme
90
What should you consider in a patient with encephalitis symptoms and temporal lobe enhancement
HSV
Meningoencephalitis / encephalitis
Temporal lobe enhancement, bilateral but asymmetrical
91
What should you think of in encephalitis <3 years old
Enterovirus
Parechovirus
92
Polio vaccine
Sabin - oral, attenuated poliovaccine (OPV) in endemic areas
Salk - inactivated poliovirus vaccine (IPV) in areas where the risk of vaccine derived polio is greater than the risk of natural infection…
93
What are SCVs (s aureus)
Small colony variants
Sub pop of staph aureus
Resistant to meticillin and aminoglycosides
94
Gram positive cocci in clusters
Staphylococcus (except staph saprophyticus)
Micrococcus
Rothia
95
Treatment listeria meningitis
21 days amoxicillin
2g every four hours IV
NO ORAL
96
97
How to clean blood spill from anthrax patient in bacteraemic phase
Clean with sodium dichloroisocyanurate granules to prevent subsequent sporulation on contact with air / soil
98
what ppe/ipc for E. coli O157
Side room ensuite
No resp mask needed
99
Ppe ipc for influenza
Side room ensuite
Fluid resistant surgical face mask for normal care
Ffp3 for AGP
