Microbiology Flashcards

Question

Bacterial vaginosis

Answer 1

Polymicrobial condition characterized by: - depletion of protective lactobacillus species - increase in other organisms esp anaerobes, eg G.vaginalis, mobincullus, atopobium vaginale 60% asymptomatic More common in black women Aetiology unknown Assoc with mid-trimester miscarriage, pre-term birth, ROM, endometritis Treat with metronidazole 400mg BD for 7days

Answer 2

AMSEL For diagnosis of BV, need 3/4: - vaginal discharge - clue cells - pH>4.5 - fishy odour with alkali on wet mount HAY/ISON based on gram stain - Grade 1 = normal flora, mostly lactobacilli - Grade 2 = mixed flora - Grade 3 = BV, absent lactobacilli Typically fishy white/grey vaginal discharge worse after intercourse

Answer 3

Gram -ve spirochaete Treponema pallidum Cannot be cultured in lab Serology indistinguishable from yaw and pinta Treatment - penicillin G, doxycycline - watch for Jarisch-Herxheimer reaction (due to release of cytokines when antibiotics kills bacteria)

Answer 4

PRIMARY - chancre (painLESS ulcer) - appears 10-90days post exposure, persists 4-6weeks before disappearing SECONDARY - 1-6months after primary infection - symmetrical non-itchy rash on trunk, condylomata latum (white/grey lesions), mucous patches around genitals or mouth TERTIARY - 1-10years after initial infection - gummas (soft rubbery growth, granuloma with necrotic centre), neurosyphilis, de Musset's sign (head nod in time with heart beat) Can -> endarteritis obliterans

Answer 5

Hard to distinguish between active, and treated past infection Non-specific tests - Veneral disease research laboratory (VDRL), rapid plasma reagin, Wasserman's reaction, Hinton's test Specific tests - fluorescent treponemal antibody-absorption test (FTA-ABS), and treponema pallidum agglutination assay (TPPA) False +ve with non-specific tests in viral infections, lymphoma, TB, malaria, pregnancy

Answer 6

In 20% of sexually active women Can either be a primary or co-pathogen in PID Can cause postpartum pyrexia Can be co-pathogen in chorioamnionitis Treat - doxycycline / clindamycin

Answer 7

Obligate intracellular grame -ve organism 3 subgroups: - A-C (follicular conjunctivitis) - D-K (genital) - L1-L3 (lymphogranuloma venereum) Contains DNA and RNA 72hr lifecycle, elementary body -> reticular body -> inclusion body Treatment - doxycycline / azithromycin / erythromycin / ofloxacin Test of cure only in pregnant or breastfeeding women

Answer 8

Foreign body (commonest) Strep pyogenes Haem influenza Shigella sonei Pinworms Chlamydia N gonorrhoeae

Answer 9

Usually staph aureus - give fluclox Typically require 10^5 organisms to establish If foreign body present, only need 10^3

Answer 10

Type 1 - assoc with surgery, diabetes - due to polymicrobial infection, anaerobes facultative or obligate Type 2 - due to group A strep Treatment - surgical debridement - antibiotic combination of Benpen 1.2g IV QDS, clindamycin, ciprofloxacin - surgical re-exploration of wound

Answer 11

Pelvic / abdominal pain Dyspareunia Post-coital bleeding Discharge Cervical tenderness Fever Complications - ectopic pregnancy - tubal infertility (12% 1st episode, 20% 2nd, 50% 3rd) - chronic pelvic pain - Fitz-Hugh-Curtis syndrome (adhesions causing RUQ pain and perihepatitis)

Answer 12

Organisms - chlamydia, neisseria (gonorrhoea), mycoplasma hominis/ureaplasma, gardnerella, trichomonas vaginalis, GBS Treatment: OP - ofloxacin 400mg BD + metronidazole 400mg BD for 14 days OR - IM ceftriazone 250mg then PO doxy 100mg BD + metro 400mg BD for 14 days

Answer 13

Reactive arthritis caused by bacterial infection Can't pee, see, climb a tree: Urethritis, uveitis, arthritis Causative organisms - salmonella, yersinia, shigella, campylobacter, chlamydia, gonorrhoea

Answer 14

Multicellular eukaryotic (membrane-bound organelles) Aerobic Cell walls have no peptidoglycans but contain ergosterol Contain - fibrils, chitins, mannan, glucan Asexual and sexual reproduction Secrete keratinase MOULDS - multicellular, branching filament (hyphae/mycelia), reproduce by spores, eg aspergillus TRUE YEASTS - unicellular, reproduce by budding, eg cryptococcus YEAST LIKE - eg candida DIMORPHIC - grows as yeast at 37degrees, as mycelia at 20degrees, eg histoplasma

Answer 15

Unicellular, eukaryotic, free-living organisms Include trichomonas vaginalis, toxoplasma gondii, giardia, cryptosporidium, plasmodium Asexual or sexual reproduction True protozoa and helminths (fluke = trematode, tape = cessatode, ring = nematode)

Answer 16

Flagellate protozoon Venereal transmission (STI) Diagnose - wet prep, PCR, culture Symptoms - discharge, intense itching and irritation, strawberry cervix, preterm delivery Treatment - metronidazole or tinidazole

Answer 17

Zoonotic infection - mainly cats Diagnosis - IgA/M avidity, serial samples taken 3weeks apart Affects muscle, neural tissue, placenta Transmission via placenta in primary infection, greatest risk at 26-40weeks BUT the earlier the infection occurs the more severe the disease in the newborn Maternal risk of chorioretinitis and encephalitis Congenital infection - stillbirth, cerebral calcification, microcephaly/hydrocephalus, choroidoretinitis, cerebral palsy, epilepsy, hepatosplenomegaly, thrombocytopenia Toxoplasma IgM persists for 3years after eradications

Answer 18

From female Anopheles mosquito vector Infects RBCs Plasmodium falciparum / vivax / ovale / malariae / knowlesi Severe malaria if parasitaemia >2% Clinical features - fever, resp distress/pulm oedema, arthralgia, retinal damage, splenomegaly, hepatomegaly, haemoglobinuria and renal failure, coma, convulsions, 20% mortality in non-pregnant but 50% in pregnant Biochemical abnormalities -hypoglycaemia, anaemia, thrombocytopenia, acidosis, hyperlacatataemia Fetal effects - miscarriage, stillbirth, prem, placental parasitaemia

Answer 19

Diagnosis via thin and thick blood films Management: - vector control - insecticides, mosquito nets, skin repellents - chemo-prophylaxis - mefloquine, doxycycline, malarone, quinine - treatment - quinine, chloroquinine, artermisinin

Answer 20

No organelles Depend on host for energy metabolism and protein synthesis Genetic material is either RNA or DNA Viral coat = capsid Fetal transmission rate increases with gestational age Incubation period usually 21days ish

Answer 21

Part of herpes family 50-80% women are seropositive Feto-maternal transmission 40%, symptomatic in 10% Maternal infection diagnosed with IgG avidity (high = old infection) Congenital defects - sensorineural hearing loss, retinitis, cerebral palsy, hepatosplenomegaly, hyperbilirubinaemia, intracranial calcification, thrombocytopenia, FGR, microcephaly CMV IgM persists for months/years

Answer 22

Type 1 - 30% genital infections in UK Type 2 - 70% Fetal transmission >30% if primary infection in 3rdT - 2% if secondary episode during labour High fetal mortality, so relative indication for caesarean if maternal lesions present within 6 weeks of birth, as long as no ROM 21 day incubation Affects skin, eyes, mouth, CNS If first episode in 1st or 2nd T - treat with normal 5 day course aciclovir 400mg TDS, then give prophylactically again from 36w-delivery If first episode in 3rdT give until delivery, and recommend caesarean

Answer 23

Part of herpes family - contagious 48hr pre rash, incubates 10-21 days Fetal transmission (congenital fetal varicella syndrome) only in first 20weeks - overall rate 1%, higher at 13-20weeks - CNS anomaly (microcephaly, cortical atrophy), limb hypoplasia, cicatricial scarring, eye defects (microphthalmia, cataracts, chorioretinitis) Risk of neonatal varicella if maternal infection within 10days of delivery Maternal complications - pneumonitis, encephalitis, hepatitis Treatment - maternal infection -> aciclovir - exposed to VZV -> prevention of disease with VZIgG

Answer 24

RNA virus aka German measles Togavirus Single-stranded RNA genome enclosed in capsid Spreads via droplets Congenital - eye (cataracts, glaucoma), heart (PDA, VSD, pulm stenosis), sensorineural hearing loss, haematological (thrombocytopenic purpura, haem anaemia, lymphadenopathy), 'blueberry muffin' rash Feto-maternal transmission rate 90% in 1stT, 30% in 2ndT In 1stT, 90% of those infected develop defects. >20 weeks no increased risk to fetus.

Answer 25

Single stranded DNA virus aka fifth disease / slapped cheek syndrome / erythema infectiosum Incubation 4-14 days 60% women are immune Causes miscarriage (10%), hydrops fetalis NO congenital defects Fetal transmission 30% in 1stT Treat with intrauterine fetal blood transfusion Virus attacks P blood group antigen (globiside) on RBCs and fetal heart

Answer 26

Lentivirus (RNA retrovirus) Primarily infects Th cells (CD4 esp), macrophages, dendritic cells, via gp120 glycoprotein AIDS is when CD4 count <200. Complications include Kaposi's sarcoma, pneumocystis carinii pneumonia, Non-Hodgkin's lymphoma, dementia Transmission is sexual, blood products, perinatal + possibly from saliva, tears or urine - negligible risk 0.17% of UK antenatal population are +ve Fetal transmission rate is 15% without treatment, <1% with - increased vertical transmission if high maternal viral load, low CD4 count, PROM, chorioamnionitis, co-morbid viral infection, breastfeeding, pre-term - ALL mothers advised not to breastfeed - increased risk miscarriage, preterm, IUGR

Answer 27

120nm diameter 2 copies of single-stranded RNA enclosed by capsid Capsid is viral protein p24 and matrix of viral protein p17 Viral envelope surrounds the matrix, composed of phospholipids and glycoprotein Glycoprotein enables virus to attach to and fuse with target cells

Answer 28

5 groups: α / β / γ / Nu / Mu-papillomaviruses α-papillomaviruses have 2 subtypes: - low-risk 6 and 11 -> non-malignant change - high-risk 16, 18, 31, 33, 45 (via E6 and E7 oncogenes) -> malignant change Only infect epithelial cells Structure is 75 capsomeres, each consist of 5 molecules of L1 co-protein, containing circular DNA (double stranded) - genome of early and late proteins - causes inactivation of p53 and pRB - incubation period 2-8months - regresses spontaneously via cell-mediated immunity (70% within 1 year) - treatment - podophyllotoxin, imiquimod, cryotherapy

Answer 29

Hep A - maternal-fetal transmission rare Hep B - incubation 6w-6mo - antigen detection with time progresses surface -> core -> eAntigen - antibody production (IgM) core -> eAntigen -> surface - immunity confirmed with anti-surface IgM - vertical transmission via pregnancy, labour and lactation. Rates depend on viral load and antigen profile - if e-antigen +ve then 90% transmission, if surface-antigen +ve then 20% - mostly in 3rdT - can treat with Interferon α or Lamivudine - give neonate propyhlactic hepB vaccine and IgG Hep C - increased risk obstetric cholestasis, 3-5% vertical transmission Hep E - 5% maternal mortality, fulminant hepatic failure in pregnancy 20%

Answer 30

HBsAg (surface antigen) +ve in acute and chronic infection, -ve if immune or post vaccination HBeAG (e antigen) +ve in acute early infection, -ve in chronic/immune/post vaccination IgM anti-core antibody +ve in acute infection, -ve in chronic /immun/post vaccination IgG anti-core antibody +ve in acute, chronic and immune, negative post vaccination HepB virus DNA +ve in acute early and chronic (high infectivity) but -ve in acute resolving, chronic (low infectivity), immune or post vaccination Anti-HBe Ab -ve in acute early and post vaccination, can be +ve or -ve otherwise Anti-HBs Ab -ve in acute and chronic infection, +ve post vaccination

Answer 31

= human T-lymphotropic virus 0.25% in UK Feto-maternal transmission via breast milk Manifestations of congenital infections occur after 10-30 years with T-cell leukaemia, or tropical spastic paraparesis

Answer 32

Penicillins - Beta-Lactam inhibit peptidoglycan cross-links in bacterial cell wall - Amoxicillin, Phenoxymethylpenicillin, Flucloxacillin Cephalosporins - Beta-Lactam inhibit peptidoglycan cross-links in bacterial cell wall - Cefalexin, Ceftriaxone, Cefuroxime Macrolides - Peptidyltransferase Inhibitor - Erythromycin, Clarithromycin, Azithromycin Quinolones - DNA Gyrase Inhibitor - Ciprofloxacin, Levofloxacin, Moxifloxacin Tetracyclines - Bind to 30S subunit of microbial ribosomes blocking attachment of aminoacyl-tRNA to the A site on the ribosome - Lymecycline, Oxytetracyline, Doxycycline Nitrofurantoin - Damages bacterial DNA via multiple reactive intermediaries Trimethoprim - Dihydrofolate Reductase Inhibitor

Answer 33

- viral infection of the skin and occasionally mucous membranes - most on trunk, arms, groin, and legs - DNA poxvirus MCV, has no non human reservoir - spread from person to person by touching the affected skin - RFs - sexually active, immunodeficient - contagious until the bumps are gone. Some growths may remain for up to 4 years if not treated - lesions are flesh-colored, dome-shaped, and pearly in appearance, 1–5 mm in diameter, with a dimpled center, generally not painful, but they may itch or become irritated - treatment is supportive

Answer 34

Rare, life-threatening sudden inflammatory response syndrome with fever, rash, hypotension, multi-organ involvement - assoc with tampons - usually Staphylococcus aureus -> exotoxin TSST-1 - also streptococcus pyogenes exotoxin A (SPEA) and S pyogenes exotoxin B (SPEB) by group A beta-hemolytic streptococci - toxins activate production of cytokines, such as tumor necrosis factor, interleukin-1, M protein, and gamma-interferon and induction of nitric oxide production which contributes to hypotension

Answer 35

Best responds to vancomycin or teicoplanin Resistant to penicillins Controlled by chlorhexadine wash and mupirocin ointments

Answer 36

eg penicillins and cephalosporins (cefalexin, ceftriaxone) - inhibit bacterial cell wall synthesis by interfering with linking of soluble peptidoglycan precursors - analogues of d-alanyl-d-alanine - effective against all gram positive bacteria and gram negative cocci - excreted by the kidneys - resistance mainly via beta-lactamase production

Answer 37

Vancomycin and teicoplanin - inhibit bacterial cell wall synthesis by binding to d-alanyl-d-alanine at the end of a pentapeptide chain, preventing the incorporation of new subunits - cannot penetrate gram negative cell wall, only work against gram positive bacteria - not absorbed from the GI tract. Oral administration used to treat Clostridium difficile diarrhoea - potentially ototoxic and nephrotoxic - vancomycin should be administered slowly to prevent 'red-man' syndrome. Teicoplanin is less toxic and can be given bolus

Answer 38

Gentamicin, tobramycin, netilmicin by 30s subunit - not absorbed from the GI tract. Do not cross the blood-brain barrier - not active against streptococci. Active against gram negative bacteria - excreted via the kidneys - potentially ototoxic and nephrotoxic - production of aminoglycoside modifying enzymes is the most important mechanism of acquired bacterial resistance - usually plasmid mediated

Answer 39

Doxycycline - inhibit bacterial protein synthesis by 30s subunit - absorbed from the gut - penetrate tissues well and are active against intracellular bacteria - effective against chlamydial, mycoplasma and rickettsiae infections - cross placenta - interferes with bone development and cause brown discolouration of teeth - contraindicated in pregnancy and children - widespread resistance as a result of their use as growth promoters in animal feed - resistance gene carried on a transposon

Answer 40

- inhibits bacterial protein synthesis by blocking peptidyl transferase, 50s ribosome - well absorbed from the gut - active against a wide range of bacteria. Main indication is the treatment of Salmonella typhi - causes REVERSIBLE dose-dependent bone marrow suppression

Answer 41

Erythromycin, azithromycin, clarithromycin and spiramycin - inhibit bacterial protein synthesis by binding to 23S rRNA (on 50s) - well absorbed from the gut; penetrate tissues well and are active against intracellular organisms - erythromycin is concentrated in the liver and excreted via bile

Answer 42

In group of Lincosamides - binds to 50S ribosomal subunit - similar antibiotic spectrum to erythromycin, excreted by the liver, active in faeces for up to 5 days after a dose - more active against anaerobes than erythromycin. Clostridium difficile is resistant and may be selected, causing pseudomembranous colitis

Answer 43

- excellent activity against gram positive and most gram negative bacteria - excellent activity against TB, viruses - good activity against fungi - poorer activity against endospores and markedly affected by organic matter - not suitable for use as surgical scrub but can be used for skin prep. Can burn skin so should be removed after several minutes - not suitable for use on mucous membranes - iodine may be absorbed by the neonate and affect thyroid function

Answer 44

- excellent activity against gram positive bacteria but less effective against most gram negative bacteria - excellent activity against viruses - poor activity against TB and fungi, no activity against endospores - only slightly affected by organic matter - useful as surgical scrub and skin prep – has high persistent activity - suitable for use on mucous membranes - toxic to ears and eyes - combination with detergents highly effective for hand disinfection.

Answer 45

Clostridium - gram positive Bacteroides - (also called Prevotella) gram negative