Microbiology Flashcards
When does Rubella infection not cause infection?
Rubella infection that occurs after 16 weeks gestation does not typically cause fetal abnormalities.
When should the rubella vaccine be given to a pregnant woman?
Rubella vaccine is live and should not be given during pregnancy. The mother should be offered vaccination after giving birth.
Is the MMR vaccine safe in breastfeeding?
Yes
Rubella key facts
Caused by rubella virus - a togavirus.
Single stranded RNA genome
Transmission primarily via the respiratory route.
Infection in children and adults usually mild
Where does rubella viral replication occur?
In the nasopharynx and lymph nodes
What is the incubation period of Rubella?
12-23 days (average 14 days)
Congenital rubella infection symptoms?
Congenital rubella infection teratogenic with poor prognosis and significant complications:
Sensorineural deafness
Cataracts
Cardiac abnormalities - most common.
Treatment for rubella congenital infection?
No specific treatment. Key prevention through vaccination programme.
Rubella vaccination in pregnancy?
Vaccination is via live attenuated virus so cannot be given to pregnant women who are found to be non-immune.
What percentage of infants with congenital CMV infection are symptomatic?
10-15% at birth, 10-15% will develop symptoms in later life.
Features of congenital CMV infection
Sensorineural Hearing loss
Visual impairment
Microcephaly
Low birth weight
Seizures
Cerebral palsy
Hepatosplenomegaly with jaundice
Thrombocytopenia with petechial rash
Cytomegalovirus (CMV) Key points
> 50% women seropositive
Congenital CMV infection refers to infection during the perinatal period and tends to effect mothers who have their first CMV infection during pregnancy.
Risk of congenital infection with primary infection of CMV during pregnancy?
30-40%
Risk of congenital infection with recurrent CMV infection during pregnancy?
1-2%
Can CMV be transmitted in breastmilk? T/F
True
What is the incubation period for CMV>
3-12 weeks.
How is fetal CMV infection diagnosed?
Via amniocentesis
When should amniocentesis be performed in fetal CMV infection?
Amniocentesis should be not be performed for at least 6 weeks after maternal infection and not until the 21st week of gestation.
What is the mortality rate of treated disseminated neonatal herpes?
30%
Herpes simplex in pregnancy key facts
- Type 1 and 2 (type 2 accounts for 70% of genital herpes infections)
- Double stranded DNA virus
How is herpes simplex virus transmitted?
HSV infection may be transmitted to neonates. Transmission is typically due to the neonate coming into contact with infected maternal secretions during delivery (transplacental infection reported but very rare).
When is the risk of primary herpes infection highest?
Highest risk with primary herpes infection within 6 weeks of delivery. Viral shedding can continue after lesions have healed.
How common is neonatal herpes?
Rare - UK incidence 3/100,000 live births
What are the 3 types of neonatal herpes?
- Restricted to skin/superficial infection (eye/mouth) - least severe.
- CNS infection (mortality with antiviral treatment 6% neurological sequelae 70%)
- Disseminated infection (mortality with antiviral treatment 30% neurological sequelae 17%)
- 70% of cases are disseminated or CNS involvement
Management 1st or 2nd trimester acquisition of genital herpes (Joint BASHH/RCOG guidance Oct 2014)
- Initial episode treated aciclovir 400mg TDS for 5 days.
- Following 1st or 2nd trimester acquisition, daily suppressive aciclovir 400mg TDS from 36 weeks of gestation reduces HSV lesions at term and hence the need for delivery by c-section
Management of 3rd trimester acquisition of genital herpes (from 28 weeks)
- Initiate aciclovir 400mg TDS and continue until delivery
- C-section delivery is advised for these patients in whom this is a 1st episode of HSV.
Anogenital wart contraindicated treatment in pregnancy?
Podophylline paint and 5-fluorouracil- teratogenic.
HPV Vaccine
Gardasil - is quadrivalent vaccine against HPV types 6,11,16 and 18
What types of HPV is responsible for HPV related cancers?
HPV types 16 and 18 are responsible for 70% of cases of HPV related cancers.
What types of cancers are HPV types 16 and 18 responsible for?
Cervical cancer and oropharynx and anogenital region
How does HPV cause cancer?
HPV is thought to induce cancer via onco-proteins. The primary onco-proteins are E6 and E7 which inactivate two tumour suppressor proteins, p53 (inactivated by E6) and pRb (inactivated by E7).
How does HPV cause cancer?
HPV is thought to induce cancer via onco-proteins. The primary onco-proteins are E6 and E7 which inactivate two tumour suppressor proteins, p53 (inactivated by E6) and pRb (inactivated by E7).
Which are the low risk HPV genotypes?
6 and 11 are low risk and cause anogenital warts
What percentage of HPV infections are cleared?
Typically 70% of HPV infections are cleared within 1 year and 90% are cleared within 2 years.
What is chancre?
A hallmark of primary syphillis.
Chancres are painless ulcers that typically develop around 3 weeks after sexual contact with an infected individual. They range from 3mm to 3cm in size.
What is Syphillis?
Caused by the bacteria Traponema pallidum
Primary syphilis facts:
Time from primary infection: 3-90 days.
Symptoms: Chancre and lymphadenopathy
Secondary syphilis facts:
Time from primary infection: 4-10weeks
Symptoms: Widespread rash typically affecting hands and soles of feet. Wart lesions (condyloma latum) mucus membranes.
Latent syphilis facts:
Time from primary infection: Early <1year after secondary stage. Late >2 yrs after secondary stage.
Asymptomatic
Tertiary syphilis facts:
3+ years after primary infection
Symptoms: Gummas OR Neurosyphilis OR Cardiovascular syphilis
Chicken pox incubation period (days)
14 (10-21)
Rubella incubation period (days)
14 (12-23)
Influenza incubation period (days)
1-3
Parvovirus (fifth disease) incubation period (days)
4-20
Streptococcus pyogenes (Scarlet fever) incubation period (days)
1-7
When may congenital fetal varicella syndrome occur?
If there is maternal varicella infection (chickenpox) during the 1st 20 weeks of gestation.
What is the risk of fetal varicella syndrome?
To mothers who have chickenpox during the first 20 weeks gestation is 0.4% (1-12 weeks) - 2.0% (13-20weeks)
When is there a risk of neonatal varicella infection?
If a mother has chickenpox in late pregnancy (5 days prior to delivery). Risk may be severe.
What abnormalities can fetal varicella syndrome cause?
Hypoplasia of one limb
Cicatricial lesions with a dermatomal distribution
CNS abnormalities
Eye abnormalities
What virus causes chicken pox and shingles?
Varicella Zoster
Should VZIG be used in pregnant women who developed a chickenpox rash?
No - no therapeutic benefit (Green top guidelines)
Who should be given intravenous aciclovir?
All pregnant women with severe chickenpox
When should oral aciclovir be given to pregnant women?
If they present within 24 hours of the onset of the rash and if they are 20+0 weeks of gestation or beyond. Use of aciclovir before 20+0 weeks should also be considered.
According to NICE what should be used for wound cleaning for the first 48 hours postoperatively?
Sterile saline
When may patients shower after surgery?
After 48 hours.
What should be used to clean a wound if the surgical wound has separated/has been surgically opened to drain pus after 48 hours?
Tap water
Antimicrobial agents and surgical wounds
Do not use antimicrobial agents for wounds that are healing by primary intention to reduce the risk of surgical site infection.
What is recognised as the most frequent cause of severe early onset infection in newborns?
Group B streptococcus (streptococcus agalactiae) - early onset (<7 days old)
How should women with a previous baby with neonatal GBS disease be treated?
Intrapartum antibiotics should be offered (even if current swabs are negative for GBS).
IV benzylpenicillin is 1st line. A cephalosporin or vancomycin is advised if penicillin allergic.
Listeriosis key points
Listeria monocytogenes causative organism
Source usually food, typically soft cheeses or cold meats.
Fetus can be infected via transplacental or ascending spread
Typically mild illness in adults unless immunocompromised
Incidence of listeriosis?
Incidence in pregnancy is around 12 per 100,000
20x more likely in pregnancy than in general population 0.7 per 100,000
Listeriosis side effects in pregnancy?
Causes chorioamnioitis and placental necrosis and granuloma formation.
Miscarriage, still birth and meningitis can result from listeria infection during pregnancy
What is fetal mortality rate in listeriosis?
Quoted at 20-30%. (up to 50%)
How is listeriosis treated?
Typically with amoxicillin for 2-3 weeks.
Gram positive obligate anaerobe?
Clostridium
Gram negative obligate anaerobe?
Bacteroides (also called prevotella)
Other obligate anaerobes? (less clinically relevant)?
- Porphyromonas gingivalis causes gingivitis
-Peptostreotococcus typically commensal - Actinomyces mostly facultative, one strain is an obligate anaerobe
Gram positive cocci?
- Staphylococcus facultative anaerobes
- Streptococcus facultative anaerobes
Gram positive bacilli OR rods?
- Corynebacterium facultative anaerobe
- Listeria non-spore forming FA
- Bacillus spore forming FA
- Clostridium spore forming obligate anaerobe
- Actinomyces spore forming FA
Gram negative cocci
Nisseria gonorrhoeae Obligate aerobes
Neisseria meningitidis Obligate aerobes
Moraxella catarrhalis Obligate aerobes
What is meant by obligate anaerobe?
Organisms that can grow and survive only in the absence of oxygen.
What is meant by an obligate aerobe?
Organisms that require oxygen to grow
What is a facultative anaerobic organism?
An organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent
Gram negative Bacilli OR Rods?
Bacteroides Obligate anaerobes
Hemophilus influenzae FA
Klebsiella pneumoniae FA
Legionella pneumonniae obligate aerobes
Pseudomonas aeruginosa obligate aerobes
Escherichia coli FA
Proteus mirabilis FA
Enterobacter cloacae FA
Helicobacter/compylobacter (spiral rod) FA
Salmonella FA
Intracellular gram negative?
Chlamydia obligate aerobe
Gram negative Spirochaetes OR spiral shaped?
Treponema pallidum
Borrelia burgdorferi
HIV genetic material?
Retrovirus - uses DNA during replication.
RNA single stranded viruses?
Hepatitis A, C, D, E
Rubella
HIV
Double stranded RNA virus?
Rotavirus
Single stranded DNA virus?
Parvovirus B19
Double stranded DNA virus?
Hepatitis B
CMV
VZV
Herpes Simplex 1 and 2
Human papilloma virus
Epstein-Barr
Group B strep treatment (Greentop guidelines)?
3g BenPen ASAP - after onset of labour and 1.5g 4hrly until delivery.
If pen allergic - if not severely allergic can use a cephalosporin (Cefuroxime 1.5g loading then 750mg every 8hrs). If severe allergy - use vancomycin (1g every 12hrs).
What is the causative organism of gas gangrene?
Clostridia perfringens (soil borne - occurs following contamination of open wound).
Most common causative organism of necrotizing fasciitis?
Group A streptococcus (streptococcus pyogenes)
What causes tetanus?
Clostridia tetani
What causes soft tissue infections e.g. cellulitis, wound infections?
Staphylococcus aureus
What type of vaccine is HPV vaccine Gardasil?
Recombinant vaccine of virus-like particles (VLPs)
What are TORCH congenital infections?
Toxoplasmosis
Other organisms
Rubella
Cytomegalovirus
Herpes simplex
Rubella clinical features
Sensorineural deafness
Ophthalmic defects (retinopathy, glaucoma, cataracts, micropthalmia)
Cardiovascular defects (PDA, VSD, pulmonary stenosis)
CNS (neurodevelopmental delay, microcephaly, meningoencephalitis)
Others (thrombocytopenia, hepatosplenomegaly)
Late onset: Diabetes, GH deficiency, thyroiditis
Toxoplasmosis key points
Protazoan infection
Treatment with spiramycin
Neonatal sequelae worse if infection during first 10 weeks of pregnancy
Toxoplasmosis clinical features
Hydrocephalus
Microcephaly
Intracranial calcifications
Ophthalmic defects (chorioretinitis, strabismus, blindness
Epilepsy
Neurodevelopmental delay
Thrombocytopenia
Anaemia
Herpes simplex key points
Genital HSV infection occurring in early pregnancy is associated:
increased risk of spontaneous abortion
IUGR
Preterm labour and congenital herpes (rare - 2 per 100,000 births)
Neonatal herpes clinical feautures?
Severe neurological impairment
Death
Treatment of suspected toxoplasmosis?
There are 2 treatment options:
- Spiramycin ASAP if fetus not infected or status of the fetus not known. This reduces risk of transplacental infection. This is continued until term, or until fetal infection is documented.
- Pyrimethamine, sulfadiazine and folinic acid where fetal infection is known e.g. positive amniotic fluid PCR. Monitoring for haemotoxicity required. Pyrimethamine should be avoided in the 1st trimester as teratogenic
What are the 2 main types of necrotising fasciitis?
Type 1: Polymicrobial (65% of cases)
Type 2: Monomicrobial (35% of cases)
Management of necrotising fasciitis?
Surgical debridement and antibiotic therapy
Is GBS antibiotic prophylaxis required for elective c-section?
No.
What organism is the leading cause of surgical site infections?
Staphylococcus aureus
What type of rash is seen in congenital rubella syndrome?
blueberry muffin rash
Congenital cytomegalovirus infection effects how many pregnancies?
1 in 150
Most common cause of UTI?
E.coli
Most common cause of skin/superficial wound/ iv line?
Staph aureus
Most common cause of cellulitis/erysipelas?
Streptococcus pyogenes (Group A strep)
Main common cause of bacterial vaginosis?
Gardnerella vaginalis (polymicrobial)
Main common cause of endometritis?
polymicrobial
What does it mean if rubella IgG and IgM positive?
Acute Rubella Infection
What genetic code is used in zika virus?
Single stranded positive-sense RNA virus
Zika virus key facts?
Virus family: Flaviviridae
Genus: Flavivirus
Single stranded RNA virus
Transmitted primarily by Aedes mosquitos
Can be transmitted sexually but risk is low
Zika virus incubation period?
Incubation period 3-12 days
Zika virus symptoms?
Fever, maculopapular rash, arthralgia or conjunctivitis. Many asymptomatic.
How long does a zika virus rash last for?
Usually resolves within 2 days but may persist up to 1 week.
What is the primary host for toxoplasma gondii?
Cats - excreted in cat faeces.
Toxoplasmosis key points
Toxoplasma gondii is an intracellular protozoan parasite.
Fetal consequences more severe if infection takes place within 10 weeks of conception.
Maternal-fetal transmission risk increases as the pregnancy proceeds but the consequences become less severe.
Toxoplasmosis side effects in pregnancy?
May cause miscarriage or fetal abnormalities such as microcephaly, hydrocephalus, cerebral calcifications, cerebral palsy, epilepsy choroidetinitis and thrombocytopenia.
How is toxoplasmosis diagnosed?
Diagnosis via PCR or immunoglobulins (IgM, IgG and IgA). MRI/CT may show ring enhancing lesions in CNS tissues.
Treatment of toxoplasmosis?
Not usually required in the immunocompetent
In pregnancy treatment is indicated if recent infection suspected
treatment varies depending on local protocols (spiromycin or combination of pyrimethamine, sulfadiaxzine, and folinic acid).
Pathogen causing chicken pox?
Varicella zoster
What does MCV 1 pox virus cause?
Molluscum
What does sterptococcus pyogenes cause?
Scarlet fever
What does parvovirus cuase?
Slapped cheek
Which group of beta haemolytic streptococci is associated with liver abscess formation?
F (streptococcus anginosus)
Give examples of alpha haemolytic streptococci?
Strep pneumoniae and viridans
Give examples of beta haemolytic streptococcus?
Sub classified into A, B, C, D, F, G, H
Beta haemolytic streptococcus group A name?
Steptococcus pyogenes
Beta haemolytic streptococcus group A causes?
Scarlet fever
Rheumatic fever
Tonsillitis/pharyngitis
Glomerulonephritis
Toxic shock
Necrotising fasciitis
Beta haemolytic streptococcus group B name?
Streptococcus agalactia
Beta haemolytic streptococcus group B causes?
GBS disease of newborn
Chrorioamniotis
Endometritis
Beta haemolytic streptococcus group C name?
Streptococcis dysgalactiae
Beta haemolytic streptococcus group C causes?
Pharyngitis
Endocarditis
Toxic Shock
Necrotising Fasciitis
Beta haemolytic streptococcus group D name?
Reclassified as Enterococcus
Beta haemolytic streptococcus group D causes?
Colitis
Endocarditis
Beta haemolytic streptococcus group F name?
Streptococcus anginosus
Beta haemolytic streptococcus group F causes?
Liver abscess
Beta haemolytic streptococcus group G name?
Group G streptococcus
Beta haemolytic streptococcus group G causes?
Toxic shock
Necrotising fasciitis
Vaginitis
What are the risk factors for endometritis?
C-section (biggest risk factor)
PROM
Mother’s age at extremes of reproductive span.
What commonly causes endometritis?
2-3 organisms (polymicrobial).
Species include:
Staphylococcus, spreptococcus, E. coli, klebsiella, chlamydia trachomatis, proteus, enterobacter, gardnerella vaginalis, neisseria, bacteroids, peptostreptococcus spp, mycoplasma spp, ureaplasma spp, tuberculosis.
Prevalence of HIV in UK obstetric population?
2 per 1000
HIV in pregnancy key points
HIV is a lentivirus (retrovirus)
Primarily infects CD4+ T-helper cells.
Rate of HIV mother to child transmission?
Was 25% in 1993. With retroviral therapy is 1.2% in 2006
What effect on HIV vertical transmission can the use of combined antiretroviral therapy have?
Reduce it to <1%
HIV can be transmitted during breastfeeding T/F?
True - therefore breastfeeding should be avoided.
When should HIV viral load be checked in pregnancy?
Should be checked at 36 weeks and then delivery planned.
If HIV viral load at 36 weeks is <50 HIV RNA copies/mL how should the baby be delivered?
Vaginal delivery
If HIV viral load at 36 weeks is 50-399 HIV RNA copies/mL how should the baby be delivered?
PLCS considered
Take into account the actual viral load, trajectory of viral load, length of time on treatment, adherence issues, obstetric factors and the womans views.
If HIV viral load at 36 weeks is ≥400 RNA copies/mL how should the baby be delivered?
PLCS
What mode of delivery is recommended for women taking zidovudine mono therapy in HIV?
Rarely used now - delivery via PLCS irrespective of viral load at time of delivery.
When is a zidovidine infusion indicated in HIV?
- For women with a viral load of >1000 HIV RNA copies/mL who present in labour or with ruptured membranes or who are admitted for planned CS.
- Indicated for women presenting in labour or with ruptured membranes in whom the current viral load is not known
- Women taking zidovudine monotherapy
What is considered very low risk category when considering infant antiretroviral therapy (ART)?
Mother has been on cART for longer than 10 weeks AND two documented maternal viral load <50 HIV RNA copies/mL during pregnancy at least 4 weeks apart AND maternal HIV viral load <50 HIV RNA copies/mL at or after 36 weeks.
What is treatment for very low risk category when considering infant antiretroviral therapy (ART)?
2 weeks zidovudine monotherapy
What is considered low risk category when considering infant antiretroviral therapy (ART)?
Maternal viral load <50 HIV RNA copies/mL at 36 weeks OR maternal viral load <50 HIV RNA at time of delivery if born prematurely
What is treatment for low risk category when considering infant antiretroviral therapy (ART)?
4 weeks zidovudine monotherapy
What is considered High risk category when considering infant antiretroviral therapy (ART)?
Does not meet low risk criteria
What is treatment for high risk category when considering infant antiretroviral therapy (ART)?
combination PEP
Infant testing in HIV - formula fed infants?
- During the first 48 hours and prior to hospital discharge
- If HIGH RISK, at 2 weeks of age
- at 6 weeks (at least 2 weeks post cessation of infant prophylaxis)
- at 12 weeks (at least 8 weeks post cessation of infant prophylaxis)
- On other occasions if additional risk
- HIV antibody testing for seroreversion should be checked at age 18-24 months
Infant testing in HIV - Breastfed infants?
Same as formula fed PLUS
- At 2 weeks of age
- Monthly for the duration of breastfeeding
- At 4 and 8 weeks after cessation of breastfeeding
Campylobacter jejuni causes?
bacterial gastroenteritis (primary cause in the developed world). Typically food borne and half the cases are related to poultry
HPV genotypes 6 and 11 are associated with what?
Low grade squamous intraepithelial lesions of the cervix (LSIL) (CN1 cytology) and genital warts
When does IgM rise?
In acute infection
What causes IgG to rise?
infection (later than IgM) and in response to vaccination
What does it mean if an individual is IgG and IgM negative to rubella?
susceptible to infection
IgG positive and IgM negative to rubella?
Patient should be considered immune
If IgM positive to rubella?
Acute infection
What is seen in actinomyces israelii?
Rare - but if mentions sulphur in exam think Actinomyces!
How does pelvic actinomycosis present?
Associated with intrauterine contraceptive devices (IUCDs)
History of prolonged use (>2yrs) and symptoms of fever, vaginal discharge, pelvic or abdominal pain and weight loss.
Most likely causative organism of odourus vaginal discharge?
Gardnerella vaginalis
Most likely causative organism of odourus vaginal discharge?
Gardnerella vaginalis
Approximate risk of HIV transmission during a single episode of receptive vaginal unprotected sex with known HIV positive person?
0.1%
Approximate risk of HIV transmission during a receptive anal unprotected sex with known HIV positive person?
1.11%
Most common cause in a 23 year old of cervicitis?
Chlamydia trachomatis
Major onco-proteins associated with high risk HPV?
E6 and E7 - inactivate tumour suppressor genes p53 and pRb respectively.
What percentage of HPV infections will be cleared by the host within 1 year?
70% and 90% within 2 years
Male circumcision increases the risk of HIV acquisition T/F?
False - it doe not increase the risk.
What percentage of women develop antibodies to HPV following infection?
Only 50-60% of female patients
