Microbiology Flashcards
what type of organism causes gonorrhoea?
Neisseria gonorrhoea - obligate intracellular gram - diplococcus
what does gonorrhoea develop into if left untreated when transferred to child from the birth canal?
Opthlmia neonatorum - neonatal conjunctivitis
25 year old male with complement deficiency presents with tenosynovitis, dermatitis and polyarthralgia - likely diagnosis?
disseminated gonococcal infection (from Neisseria gonorrhoea)
what is the gold standard for diagnosing Gonorrhoea?
Culture from smears - Rectal or urethral
what is the difference in sensitivity when diagnosing gonorrhoea from either urethral or rectal smears?
urethral - 95%
rectal - 20%
What is the treatment for gonorrhoea?
- ceftriaxone IM - 250mg single dose
OR
cefixime PO 400mg single dose
How does symptomatic gonorrhoea infection manifest in women?
vaginal pruritus +/- mucopurulent discharge
What % of gonorrhoea infections become complicated?
10%
How does complicated gonorrhoea infection manifest?
prostitis in men
pelvic inflammatory disease (PID)/Salpingitis
What is he most common cause of female infertility in europe?
Ascending complicated gonnorhoea infection resulting in PID / salpingitis
What % of chlamydia is unsymptomatic?
80% female
50% men
What organism causes chlamydia?
Chlamydia trachomatis - gram negative
what are the complications of chlamydia?
PID, tubal factor infertility (TFI), risk of ectopic, risk of endometriosis, chronic pelvic pain, epidydimitis, reiters syndrome, adult conjunctivitis
What serovars of chlamydia cause genital infection?
D-K
How do you diagnose Chlamydia?
NAATs (nucleic acid amplification tests)
Whats the Tx for uncomplicated chlamydia?
Azithromycin (1g) stat
doxycycline 100 mg BD 7/7
what is the name for lymphatic infection with Chlamydia trachomatis?
lympho-granuloma venereum (LGV)
What is the likely diagnosis when you see: painless genital ulcer, non-indurated, balanitis, proctitis (cerivcitis)?
Early LGV - 1st stage
Which serovars are responsible for LGV?
L1 L2 L3 Chalmydia trachomatis
What is the infectious agent causing syphilis?
Treponema pallidum - an obligate gram negative spirochaete
Name the nontreponemal tests for syphilis
VDRL slide test - detects lipoidal antibody on both host and treponemal cells
RPR (modified VDRL)
What are the 2 types of test for syphilis
Non-treponemal (RDR)
Treponemal (detects Abs from specific Treponema antigens - e.g. TPPA)
Tx for syphilis
IM benzathine penicillin (or doxycycline if allergic)
What tests must you do to diagnose Trichomonas vaginalis?
Wet prep microscopy, PCR
Tx for trichomoniasis vaginalis?
Metronidazole
How is BV diagnosed?
- microscopy of gram stain
- whiff test
- raised pH (more alkaline as vagina is naturally quite acidic)
- clue cells (epithelial cells coated with bacteria)
What is the Tx for Hep B infection?
- vaccine
- antivirals = interferon alpha
direct acting antivirals (DAAs)
tenofivir, entecavir,emtrictabine (esp with HIV infection)
What 5 tests would you do if you suspect hep C infection/.
Hep C antibodies (via immunoassay or recombinant immunoassay (RIBA) NAATs LFTs - ALT probably raised viral genotype transient elastography
Tx for Hep C?
- may have spontanous eradication (45% patients)
- sofosbuvir therapy + velpatasvir
what is the difference between bacteriuria and cystitis?
bacteriuria = presence of bacteria in the urine - not necessarily a problem!
cystitis = inflammation of the bladder, often caused by infection
what are the proper terms for lower and upper urinary tract infections?
upper = pyelonephritis lower = cystitis
what is the prevalence of women experiencing a UTI in their lifetime?
40-50%
What is the most common organism causing UTI?
E. coli (95%)
what is the 2nd most common cause of UTIs in young women?
Staph. saprophyticus
Which organism is commonly present in UTIs involving calculi/stones?
Proteus mirabilis
What are the 3 host defences against UTIs?
- urine (pH, osmolality)
- urine flow
- urinary tract mucosa
What is a specific risk factor for bacterial infection of the bladder in children resulting in pyelonephritis and possibly renal scarring?
urinary tract defects such as vesicoureteral reflux (retrograde flow of urine from bladder into kidneys)
what are 4 examples of neurogenic causes of bladder outflow obstruction?
diabetic neuropathy
polio
spinal cord injury
tabes dorsalis (untreated syphilis)
what is an organism which can cause UTIs and abscesses via the haematogenous route? (ie bacteraemia & seeding in the kidneys)
Staph. aureus
what are the classic features of UTI infection?
abdominal / flank pain
dysuria
frequency
what type of organism are rigors typically associated with?
gram negative bacteria
What investigations should you do for a suspected UTI?
- urine dipstick
- MSU for urine microscopy, culture and sensitivities
- Bloods - FBC, UE, CRP (inflammatory markers and renal function) if suspect pyelonephritis or more severe
COMPLICATED
- Renal USS
- IV urography
- to look at structure/flow of urine
What positive test in a urine dispstick indicates the likely presence of coliform bacteria?
Nitrites (coliform bacteria have an enzyme that converts nitrates to nitrites)
why are pregnant women particularly vulnerable to UTIs?
outflow obstruction due to gravid uterus
what are squamous epithelial cells on a urine microscopy usually indicative of?
contamination.
what does a urine sample with <10^5 cfu/mL indicate?
No infection
What is the general threshold for cfu/mL in the bladder for indicating a urine infection?
> 10^5 cfu/mL (colony forming unit)
what is the empirical therapy for UTIs in the community?
Trimethoprim
What is the resitance level of trimethoprim?
40%
what is the common empirical treatment for UTIs in hospitals?
NOT trimethoprim due to resistance
SO cefalexin
What is the Tx for catheter associated UTIs?
- remove the catheter (due to biofilm buildup and intro of organisms)
- gentamycin
What is the Tx for pyelonephritis?
antibiotics:
co-amoxiclav + aminoglycoside (gentamycin
In men, what investigation should be done in pyelonephtitis?
USS - to look for structural problems perhaps causing obstruction
What are 4 complications of UTIs?
- perinephric abscess
- chronic pyelonephritis due to scarring
- septic shock
- acute papillary necrosis
why would you never use nitrofurantoin in catheter patients?
because it concentrates in the patient’s bladder - catheter drains continuously.
When should you advise patients to take nitorfurantoin tablets to Tx a UTI?
after they have just voided their bladder - it concs in thebladder so no point taking and then emptying bladder - wont clear
The presence of what would indicate a poorly taken urine sample
squamous epithelial cells
what is the difference between treponemal and non trepoemal tests for syphilis?
non-treponemal = detect biomarkers that are released during the cellular damage occuring from syphilis’ spirochete - Ab that reacto to cardiolipin
treponemal = antibodies: IgG IgM and IgA
What is the drawback of nontreponemal tests?
decreased sensitivity in early primary syphilis and late latent - and false positive reactions due to other infections
What is the likely cause of diarrhoea when the symptoms develop within 2-7 hours?
Staph aureus
What is the likely causative organism in a patient who had a chicken bbq at the weekend and has florrid diarrhoea at the end of the week?
campylobacter
What is the likey causative organism in a pt who presents with diarrhoea symptoms 24h after eating some prawns?
Vibrio parahaemolytics
what does a staphylococcal enterotoxin (SE) superantigen bind to?
directly to T cell receptrs ad MHC molecules (outside the peptide binding site)
what organism produces enterotoxin which can act as a superantigen in the GI tract
Staph. aureus
what does Staph aureus enterotoxin in the GI tract cause the release of, and what symptoms does this cause
IL1 and IL2
vomiting watery diarrhouea (non bloody)
how do you trea Staph aureus food poisoning?
Fluid resus
not Abx as its a pre formed toxin!
what organism is assocated with food poisoning from reheated fried rice?
Bacillus cereus
Why does heating rice not kill B. cereus?
very heat stable emetic toxin
What symptoms does Bacillus cereus infection cause (including 2 serious complications?)
watery non bloody diarrhoea - self limited
bacteraemia
cerebral abcess
What organism is associated with honey and infants?
Clostridium botulinum - which is a preformed toxin which causes botulism
where organism is normal flora of the colon but not the small bowel, resulting in food poisoning from reheated meat?
Clostridium pefringens
which bacteria causes pseudomembranous colitis after cephalosporin treatment?
Clostridium Difficile
What is the treatment plan for a patient with active diarrhoea C. diff
side room
stop offending antibiotics
metronidazole and vancomycin
what is a beta haemolytic organism which is aesculin positive and has tumbling motility?
Listeria monocytogenes
Treatment for Listeria infection?
ampicillin
which parts of the colon does E. coli eterotoxins act on?
ileum and jejunum but not on large bowel
Give the 4 types of E. coli
- ETEC (E. coli enterotoxigenic)
- EPEC (pathogenic)
- EIEC (invasive)
- EHEC 0157 (haemorrhagic)
which type of E. coli can cause HUS?
EHEC - E. coli 0157
What are the 3 antigens found on Salmonellae species?
O = cell wall H = flagellum Vi = capsular, virulence, antiphagocytic
give the 3 species of salmonellae
- S. Typhi
- S. enteriditis
- S. cholerasuis
What kind of bacteria are non lactose fermenters, H2S producers
Salmonellae
give 2 characteristics of S. typhi
constipation, splenomegaly, rose spots, Blood culture positive, anaemia, leucopenia
what organisms causes dysentry and is the most effective enteric pathogen - only needing an infective dose of 50
Shigellae
which group of vibrios causes epidemics?
group 01
what organism is transmitted by contaminated water and human faeces - shellfish, oysters, shrimp, and causes massive volume of rice water stool
Vibrio cholerae
what type of agar is required to grow Vibrio parahaemolyticus
Salty 8.5% NaCl
What organism causes cellulitis in shellfish handlers?
Vibrio vulnificus
How do you treat Vibrio vulnificus?
doxycycline
what organisms do you need special oxygen deplete jars to grow?
Campylobacter - microaerophilic
when would you treat campylobacter and how?
If immunocompromised - with a macrolide
how is campylobacter transmitted?
contaminated food & water with animal faeces
classic signs of campylobacter infection
watery foul smelling diarrhoea bloody stool, severe abdo pain
What are 3 complications of campylobacter infection?
Guillan Barre Syndrome (GBS)
Reiters
Reactive arthritis
what organism is known to cause acute diarrhoea, enterocolitis, mesenteric adenitis, and transmitted via food contaminated with domestic animal faeces
Yersinia enterelytica
name a protozoan organisms that causes infections on camping holidays when water isnt boiled
entamoeba histolytica
how do you treat entamoeba histolytica infection?
metronidazole + paromomycin in luminal disease
How does one become infected with Giardia lamblia?
ingestion of cysts from faecally contaminated water/food
how is Giardia lamblia diagnosed
stool micro
ELISA
string test
what 3 groups tend to be a risk of Giardia lamblia?
MSM
Mental patients
travellers/hikers
What type of microorganism is Giardia lamblia?
Protozoa
Why is norovirus so prone to outbreaks?
Very low infectious dose (18-1000)
Robust environmental resilience (0-60 deg.C)
No immunity long term
What viruses cause diarrhoea?
Norovirus Rotavirus Adenovirus Poliovirus Enteroviruses (coxsackie, ECHO) Hep A
Which strains of adenovirus can cause non bloody diarrhoea in children <2 years?
types 40 + 41
which types of cholera can you vaccinate against?
01 and 0139
What vaccinations vs rotavirus are there?
Rotarix - live attenuated (2 doses)
Rotateq
give 4 viruses we worry about when thinking about intrauterine viral infection?
Rubella, CMV, Parvovirus B19, VZV (also HSV, HIV, Hep B)
which 2 viral infections are we concerned about perinatally?
Herpes, VZV
What is the classic presentation of a child with parvovirus B19 at the end of infection?
slapped cheek syndrome - erythema infectiosum
why is screening for Rubella not offered in pregnancy?
- vey rare now in UK due to MMR vaccine
- also if there is infection, not much you can do as cannot offer vaccine - as it is a live vaccine - little intervention
what is the incubation period of CMV?
4-8 weeks
main transmission route of CMV?
saliva
what is the main congenital infectious cause of profound sensorineural hearing loss?
CMV (accounts for 10-15%)
Give some factors which can increase the risk of perinatal HSV infection?
- recent maternal infection
- mode of delivery
- use of scalp monitors during delivery
a what point is HSV most commonly acquired periatally?
75-85% at delivery during birth canal exposure
What are the 3 clinical presentations of neonatal herpes?
- SEM disease –> limited to skin, eyes, mouth
- CNS disease - encepalopathy
- Disseminated disease - Sepsis, organ involvement, vesicular rash
What is the Tx of neonatal herpes infection?
IV aciclovir
what is the infectious period for Chicken pox?
2 days before appearance of rash –> when vesicles have crusted / are dry
what is the worry if a mother contracts VSV duringthe 1st 20 weeks of pregancy?
risk of congenital varicella syndrome
which infection do you get koplik spots?
Measles