Microbiology Flashcards
What type of organism is neisseria gonorrhoea
Intracellular gram neg diplococcus
Treatment of gonorrhoea
IM Ceftriaxone single dose 1g
Name of chlamydia bacteria
Chlamydia trachomatis
What bacteria is chlamydia trachomatis
Obligate intracellular gram-ve that can not be cultured on agar
Typical presentation of chlamydia
Asymptomatic especially in women (80%)
Men get dysuria and discharge
Women get vaginal discharge and bleeding
How are chlamydia infections classified
By serovars
A-K
Division of chlamydia serovars and where they affect
A-C- trachoma
D-K- genital chlamydia
What is trachoma
The keratoconjunctivitis cause by chlamydia trachomatis- most common infective cause of blindness worldwide
What happens in trachoma
Keratoconjunctivits and then can get downward curling of eyelashes into the eye
Treatment for chlamydia
Doxycycline
2nd line azithromycin
What is lymphogranular venereum
Infection of the lymphatics by chlamydia trochomatis L1-3
Which people does LGV occur in
Typically those in endemic regions by more recently MSM
Complications of chlamydia PID
Tubal factor infertility
Ectopic pregnancy
Chronic pelvic pain
Disease course of LGV
Primary stage (3-12 days)- painless ulcers, proctitis, balanitis and cervicitis
Secondary stage (2wks-6mths)- painful inguinal buboes, fever, malaise
Late LGV- inguinal lymphadenopathy, genital elephantiasis. frozen pelvis, perianal ulcers
Diagnosis of LGV
NAAT to detect L1-3
What bacteria causes syphillis
Treponema pallidum- obligate gram negative spirochaete
What are the stages of syphillis infection
Primary
Secondary
Latent
Tertiary
Primary syphillis
Painless solitary genital ulcer that developed from a macule -> papule
Regional adenopathy
How long after transmission do you get ulcer in syphillis
1-12 weeks
What is a chancre
Ulcer seen in primary syphillis
Secondary syphillis
Disseminated syphilis
Get systemic bacteraemia after syphilis reaches the lymphatics
Fever, malaise, lymphadenopathy
Maculopapular rash on trunk -> limbs -> soles and palms
Genital warts (condyloma acuminate)
How do condyloma acuminate appear
Smooth white and painless
What happens in latent syphillis
Asymptomatic but still a serological infection
3 types of tertiary syphillis
Gummatous- skin/bone/mucosa granulomas (gumma = granuloma) BARELY ANY SPIROCHAETES here
Cardiovascular- aortic dilation and aortitis
Neurosyphilis- tabes dorsalis, argyll-robertson pupil, dementia/any focal neurology
What is tabes dorsales
Degeneration of the posterior spinal chord
Get loss of proprioception and vibration
What is argylles robertson pupil
Lose light reflex but not the accommodation reflex
What is investigation for neurosyphilis
CSF spirochaetes
How is syphilis diagnosed
Spirochaetes seen in primary lesions using dark microscopy
Confirmed using serology
Non-treponemal
- RPR
- VDRL
- anti-cardiolipin
BUT CAN GET FALSE POSITIVE SO NEED TO CONFIRM WITH….
Treponemal
- T pallidum haemoaglutinin test
Which tests can be used to monitor syphilis treatment
Non-treponemal tests. RPR in particular
Ideally will see a 4 fold decrease
Treatment for syphilis
- if penicillin allergic
Single dose IM benzathine penicllin
Doxycycline if allergic
What is common reaction to syphilis treatment
Jarisch herxheimer reaction
Get flu like reaction which will clear in 24 hrs
What is congenital syphilis
Where baby gets syphilis infection from birth or pregnancy
Presents with symptoms over first couple of years
- rash
- fever
- neurosyphilis
- pneumonitis
What is chancroid caused by
Haemophilus ducreyi- gram neg coccobacilis
Symptoms of chancroid
Mutliple painful ulcers
Inguinal lymphadenopathy
How is chancroid diagnosed
Culture on chocolate agar, PCR
What causes donovanosis
Klebsiella granulomatis- gram negative bacillus
Typically seen in African, Indian, aborigenese populations
What are beefy red ulcers seen in
Donovanosis
How is donovanosis diagnosed
Giemsa stain of biopsy
See Donovan bodies
Treatment for donovanosis
Azithromycin
What causes trichomoniasis
Flagellated protozoa- trichomoniasis vaginalis
Problem with trichomoniasis
Increased risk of HIV infection
How is bacterial vaginsosi diagnosed
Amsel criteria- must have at least 3/4
- white discharge
- pH above 4.5
- clue cells on microscopy
- positive whiff test
What are clue cells
Vaginal epithelial cells with bacterial rods on the cell membrane
What is the whiff test
Done in bafcterial vaginosis
Add potassium hydroxide to discharge- if positive will get fishy odour
What happens if get molloscum contagiosum if immunosuppressed
Widespread lesions
What are condylomata acuminate
Genital warts
Seen in secondary syphilis
HPV 6 or 11
How are viral warts diagnosed
Clinical diagnosis
How are viral warts treated
Hyperkeratotic- cryotherapy
Soft non-hyperkeratotic- podophyllotoxin
Who is podophyllotoxin contraindicated in
Pregnant women
CXR of HIV child with diffuse changes but is well
Lyphoid interstitial pneumonitis
What proportion of children will get HIV from untreated mothers
1/3
How can HIV be transmitted vertically
Breastfeeding
In utero
Intra partum
What is main predictor of vertical transmission of HIV
Viral load after primary infection settles
What is miliary TB
Disseminated haematogenous spread of TB
Initial investigations for TB
CXR- see upper lobe cavitation
3 sputum samples- if cant get sputum do BAL
Do NAAT to look for resistance
What is gold standard for TB
Culture myobcaterium for 6 weeks on lowenstein jensen medium then do ziehl neelson stain
What type of bacteria are mycobacteria
ROd shaped gram positive non motile
What is treatment for TB
RIPE for 2 months
Rifampicin and isoniazad for 2 more months
When do you treat TB for longer
Subacute meningitis
Potts disease
What is prophylaxis for TB
Isoniazid monotherapy
Side effects of each TB medication
Rifampicin-orange secretions
Isoniazad- peripheral neuropathy
Pyrazinamide- hepatoxic, gout
Ethambutol- optic neuritis
Second line for TB
Amikacin
Kanamycin
Quinoloines
What is hansens disease
Leprosy
What is the organism which causes leprosy
Mycobacterium leprae
Presentation of leprosy
Skin depigmentation
Nodules
Trophic ulcers
Nerve thickness- causes sensory and motor defects
What are lower resp tract infections
Broad term for lung infection- includes pneumonia, bronchitis, empyema, abscess
Tend to not have CXR changes
What is bronchitis versus pneumonia
Bronchitis- nflammation of medium sized airways- mainly in smokers
Pneumonia is infection of lung alveoli
Most common cause of HAP
Pseudomonas aeruginosa
What causes rusty coloured sputum CAP
S pneuominae
What type of organism is s pneumoniae
+ve diplococci
What type of organism is h influenzae
-ve cocco-bacilli
What bacteria causes grape bunch clusters
Staph aureus
What CAP seen in alcoholics
Klebsiella pneumonia
Often see haemoptysis
What type of organism is klebsiella
-ve rod, enterococcus
What organism associated with cavity in CAP
S aureus
What precedes staph aureus CAP
influenza infection
What is treatment for atypical pneumonias
Clarithomycin
Which pneumonia causes hepatitis and hyponatraemia
Legionella pneumophilia
Presentation of mycoplasma pneumoniae
Dry cough
Arthralgia
Erythema multiforme
Which pneumonia is associated with uni students/ boarding schools
Mycoplasma pneumoniae
Tests for mycoplasma
Cold agglutin test
What pneumonia is associated with birds
Chlamydia psitticae
Pneumonia in patient who just had bone marrow transplant
CMV
What pneumonia in patients who have neutropenia
Aspergillus
Which type of bacteria are splenectomy patinets at risk for pneumonia
Encapsulated bacteria
- H.influenzae
- S.pneumoniae
- N.meniningitidis
What bacteria are worried about in cystic fibrosis
Pseudomonas aeruginosa
Burkholderia cepacia
Investigations for pneumonia
CXR
Sputum MC&S- consider BAL if non-productive
Work out CURB-65
Investiations if atypical pneumonia
Legionella urine antigen
Serum antibody tests
Crtieria for CURB-65
Confusion
Urea- >7
RR- >30
BP- <90/60
65- aged older than 65
Treatment for CURB 65 0-1
Oral amoxicillin 5 days
Allergic to penicillin- clarithomycin
Treatment for CURB65 2
Oral amoxicillin and oral clarithomycin
Consider admission
Treatment for CURB65 3-5
IV co-amoxiclav
IV clarithomycin
Admission
1st line for HAP
Ciprofloxacin and vancomycin
2nd line for HAP
Tazocin and vancomycin
Aspiration pneumonia treatment
Tazocin and metronidazole
What are some causes of HAP
Pseudomonas
Haemophilus
S aureus
Klebsiella
Best treatment if confirmed pseudomonas
Tazocin and gentamicin
What organism is common causative agent in young females UTI- not most common though
Staphylococcus saphrophyticus
Which antibiotics inhibtis cell wall synthesis
Beta lactams
Glycopeptides
What are the beta lactams
Penicillin
Cephalosporin
Carbapenems
How do beta lactams work
Inactivate the enzymes involved in cell wall synthesis (transpeptidases)
Only work when bacteria dividing
Bactericidal
Why dont beta lactams work against mycoplasma and chlamydia
Lack peptidoglycan cell wall
Why dont beta lactams work on abscesses
Bacteria arent dividing
Also not divinding in biofilms
How can s aureus defend against penicillin
Produce beta lactamases
Coverage of each methicillin antibiotics
Penicillin- gram positive, streptococci, clostridia
Amoxicillin- quite a broad spectrum- covers more gram negatives
Flucloxacillin- produced to replace penicillin. More stable to beta lactamse
How does clavlulanic acid and tazobactam work
Beta lactamase inhibitor- given with penicillins
What is tazocin
Combination of piperacillin and tazobactam
What is different between different gen cephalosporins
Increasing generations increases cover against gram negative and pseudomonas
All are stable to beta lactamase
What are extended spectrum beta lactamases
Enzymes which can act agaisnts cephalosporins
Increasingly common in E coli and klebsiella
Advantage of carbapenems
Stable to ESBL enzymes
What is used by bacteria against carbapenems
Carbapenemase produced
Key features of beta lactams
Non toxic
Renally excreted
Short half life
Dont cross BBB- but can if meninges inflammed
What are glycoppetides active against
Gram positive- c diff, MRSA
Cant do gram neg as too large to pass through cell wall
Disadvantage of vancomycin
Nephrotoxic
Must monitor
MOA of glycopeptide
Inhibit transpeptidase and transglycoside enzymes in cell wall cross links
Abx which inhibit protein synthesis
Tetracyclines
Aminoglycoside
Macrolides
Chloramphenicol
Oxazolidinines
Problems of aminoglycoside
Nephrotoxic and ototoxic
Indication of aminoglycosides
Gram negative
Indication of tetracycline
Intracellular pathogens- chlamydia and mycoplasma
Who cant you give tetracyclines to
Children
Pregnant women
Indication of macrolides
Gram+ in penicillin allergy
Atypical penumonia
Campylobacter
Indication of chloramphenicol
Eye drops- bacterial conjunctivitis
INdications of oxalizininoes
Gram+ve
MRSA
Which Abx inhibit DNA synthesis
Fluoroquinolones
Nitroimidazole
Fluroquinolones indications (ciprofloxacin)
Gram negative
Indications of nitroimidazole
Anaerobes and protozoa
Which antibiotic is nitrofurantoin similar to
Metronidazole
MOA of rifamycins
Inhibit RNA synthesis
Indications for rifamycins
Mycoplasma
Chlamydia
TB
Which antibiotics target cell membrane through toxins
Polymyxin
Cyclic lipopeptide
Example of polymyxin
Colistin- gram negative
Example of cyclic lipopeptide
daptomycin- gram +ve, MRSA, vancomycin resistant enterococcus
Which antibiotics inhibit folate metabolism
Sulfonamides
Diaminopyrimidines
What is indication of sulphonamides
PCP
Combine sulphamethoxazole and trimethopin
Mechanisms of resitance
Bypass antibiotic sensitive step
Enzyme mediated drug inactivation
Impair accumulation of the drug
Modify the target of the drugs
BEAT
Give an example of bacteria inactivating the antibiotic
Beta lactamases
Give an example of alered target
MRSA
Encodes gene (mecA) which produces a novel penicillin binding protein which cant bind to the antibiotic
How is strep penumoniae resistant
Stepwise mutations in PBP- if low resistance increase the dose
Is an issue in meningitis as not many beta lactams can cross the BBB
Mechanism of macrolide resistance
Altered target by methylating ribosome- reduces the bindnig
Encoded by erythromycin ribosome methylation gnes
Most common reaction to antimicrobial agents
GI upset
Factors which affect prescribing abx for a patient
CHAOS
Host characteristics
Antimicrobial susceptibilities
Organism itself
Site of infection
What is MIC
Minimum amount of antibiotic needed to stop growth in a bacteria in vitro
When must specimens for cultures be taken
Before start Abx
First investigation done on culture
Gram stain
Other than gram stain what tests will be done on bacteria in microbiology
Immunofluorescence
PCR
When do you do gram stain
CSF
Joint aspirate
Pus
How long is N meningitidis treated for
10 days
How long is Acute osteomyelitis treated for
6 weeks
How long is Infective endocarditis treated for
6 weeks
If patient hasnt responded in 48 hours to abx what could be cause
Actually have infection
Catheter
Infective endocardiitis
Most narrow spectrum for e coli
Amoxicillin
What is an opportunistic infection
Organism which does not normally cause disease or where symptomology becomes worsened based off the patients immune system
Can be endogenous- reactivated
Exogenous
What causes oral thrush and CMV retinitis
HIV
Sources of infection in SAT
Virus from graft
Viral reactivation in host
Infection from social contact
Order of greatest relative risk of opportunistic viral infection
Steroids
Cytotoxic chemo
Monoclonal AB therapy
Solid organ transplant
HIV
Allogenic stem cell transplant
What does JC virus cause
Progressive multifocal leukoencephalopathy
What does PML cause
Get demyelination of white matter leading to personality changes, cognitive dysfunction and focal neurology
What causees haemorrhagic UTI post stem cell transplant
BK virus
Prophylaxis for monkeypox
Small pox vaccine
Treatment for monkey pox
Analgesia
Tecovirimat if very severe
Where is natural resevoir for influenza A
Ducks- any water bird
What are 2 types of influenza
A and B
What are 2 spike proteins in influenza
Haemaglutinin
Neuraminidase
Risks of aminoglycosides
Ototoxic
Nephrotoxic
Side effect of tetracyclines
Light-sensitive rash
Why dont use chloramphenicol in neonates
Risk of aplastic anaemia
Get grey baby syndrome in neonates as cant metabolise the drug
Risks of oxazolidinones
Thrombocytopenia
Optic neuritis
MOA of fluoroquinolones
Binds to alpha subunit of DNA gyrase
Bactericidial
MOA of nitroimidazoles
Rapidly bactericidal
MOA of rifampicin
DNA dependant RNA polymerase is target
Bactericidal
Why is rifampicin so susceptible to resistance
Get rapid resistance as chromosomal mutations lead altered target in the beta subunit of RNA polymerase
When is only time give rifampicin alone
Prophylaxis in meningococcal infection
Which bacteria use beta lactamases as their major mechanism of resistance to Beta lactams
Staph aureus
Gram negative bacili- E coli and pseudomonas
NOT MRSA and streptococci
How is MRSA resitant to beta lactams
Encodes gene (mecA) which produces a novel penicillin binding protein which cant bind to the antibiotic
How are e.coli and klebsiella becoming resistant to Cef
ESBL
What is bacteriuria
Presence of bacteriuria
Not necessarily pathogenic as common in elderly in particular
Get commensal bacteria in urethra
What is a complicated UTI
This occurs in people with structurally abnormal urinary tracts- catheters, calculi
Normally occurs in men and patients with catheters
Most common infective organism in UTI
E.coli but this is done by a select group of serovars
Organism if getting recurrent UTIs
Pseudomonas
Which bacteria is associated in presence of renal stones
Proteus mirabilis
Antibacterial host defence in Urinary tract
Urine- pH, organic acids, osmolality
Urine flow
Musoca has cytokines
What increases risk of UTI structurally
Literally anything which interferes with urine flow or abnormalities
Neurogenic dysfunction too
What increases risk of UTI in children
Vesicoureteral reflux
What is common cause of abscesses in kidney
If haematogenous then staph aureus- IE
Rarely see gram negative bacilli abscesses from haematogenous route- typically ascending
How treat abscess in kidney caused by s aureus
IV flucloxacillin
How does UTI present in elderly patients
Tend to be non-specific
Abdo pain
Change in mental status
Which patients dont you do urine dip in
Those over 65 as often have bacteria in tract anyway
When is only time treat asymptomatic bacteriuria
Pregnancy
What does mixed growth suggest on urinary MCS report
Poorly taken sample
Only reports it 1 orgnaism predominate
What are squamous cells indicative of on urine dip
Contamination
What can sterile pyuria suggest
Prior treatment with abx
Calculi
TB
Bladder neoplasm
STI
Which is main risk factor for candida UTI
Catheter
Treatment for catheter UTI
Can give stat aminoglycoside and then remove it
Complications of pyelonephritis
Abscess
Chronic
Septic shock
Acute papillary necrosis
UTI guidelines for women under 65 for investigations
Once ruled out pyelo and other vaginal/sexual health causes of symptoms
Does have
- dysuria
- new nocturia
- cloudy urine
If has 2 or more do urine culture
If has 1 do urine dipstick
Urine dip guidelines for women under 65 urine dip
If nitrite positive or leukocyte and RBC positive UTI likely- send for culture and give consider abx or back
If neg nitrite and pos leukocyte UTI equally likely as other diagnoses- send for culture and give consider abx or back
If all neg isnt UTI
What should be interpreted as positive UTI on urine culture
Culture of over 10^4/5 colony forming units unless E.coli or staphylococcus saprophyticus where 10^3 colony forming units
10^5 colony forming units mixed growth with 1 orgnaism predominating
ALWAYS IN CONJUNCTION WITH SYMPTOMS
Treatment for pyelonephritis
IV co-amoxiclav and gentamicin
Treatment for uncomplicated female UTI
Cephalexin PO 3 days or nitro oral 7 days
Treatment for uti if female or breastfeeding
1st line cefalexin oral 7 days
2nd line co-amoxiclav
If allergic consult micro
Treatment for UTI if male
Cephalexin for 7 days
If suspect prostatis ciprofloxacin 14 days
Treatment for UTI chronic prostatitis
Oral cipro for 4-6 weeks
Treatment for urosepsis
Aminoglycoside
Treatment for catheter associated UTI
Give macrolide before removal
What tests cant you use in an immunocompromised patient
Serology
What is done if immunosuppressed patient becomes unwell
Screening based on syndromes
- csf
- resp
- gut biopsy
- blood
How does HSV present in immunocompromised
Mouth ulcers
Oesophagitis
Pneumonitis
Hepatitis
DOES NOT INCREASE RISK OF ENCEPHALITIS
Where does herpes lie latent
Sensory neurones
How can varicella present in immunocompromised
Pneumonitis
Encephalitis
Hepatitis
Progressive outer retinal necrosis- PORN
Acute retinal necrosis
How can varicella present in immunocompromised in neo-nates
Purpura fulminans