Microbiology Flashcards
Purple gram stain
Gram positive (wall/membrane)
Pink gram stain
Gram negative (membrane/wall/membrane)
Classes of antibiotics which inhibit cell wall synthesis
Beta lactams (penicillins, cephalosporins, carbapenems) Glycopeptides
Benzylpenicillin
Beta lactam - penicillin (inhibits cell wall synthesis)
Ceftriaxone
Beta lactam - cephalosporin (inhibits cell wall synthesis)
Meropenem
Beta lactam - carbapenem (inhibits cell wall synthesis)
Vancomycin and teicoplanin
Glycopeptides (inhibit cell wall synthesis); gram +ves only
Classes of antibiotics which inhibit protein synthesis
Aminoglycosides Tetracyclines MSL group - macrolides, lincosamides, streptogramins Chloramphenicol Oxazolidinones
Gentamicin, amikacin and tobramycin
Aminoglycosides (inhibits protein synthesis)
Doxycycline
Tetracycline (inhibits protein synthesis)
Erythromycin
Macrolide (inhibits protein synthesis)
Synercid
Streptogramin (inhibits protein synthesis)
Clindamycin
Lincosamide (inhibits protein synthesis)
Chloramphenicol
Eye drops for bacterial conjunctivitis (inhibits protein synthesis)
Linezolid
Oxazolidinones
Antibiotics which inhibit DNA synthesis
Fluoroquinolones
Nitroimidazoles
Ciprofloxacin, levofloxacin, moxifloxacin
Fluoroquinolones (inhibit DNA synthesis)
Metronidazole
Nitroimidazole (inhibit DNA synthesis)
Antibiotics which inhibit RNA synthesis
Rifamycin
Rifampicin
Rifamycin (inhibits RNA synthesis)
Antibiotics which produce cell membrane toxin
Polymyxin e.g. colistin
Cyclic lipopeptide e.g. daptomycin
Colistin
Polymyxin (cell membrane toxin)
Daptomycin
Cyclic lipopeptide (cell membrane toxin)
Antibiotics which inhibit folate metabolism
Sulfonamides
Diaminopyrimidines
Sulphamethoxazole
Sulfonamide (inhibits folate metabolism)
Trimethoprim
Diaminopyrimidine (inhibits folate metabolism)
Antibiotic for gram negative sepsis
Aminoglycosides e.g. Gentamicin
3rd generation cephalosporins e.g. ceftriaxone
Carbapenems e.g. meropenem
Antibiotic for intracellular organisms e.g. chlamydia
Tetracyclines e.g. doxycycline
Treatment of gram positive infections
Penicillins or macrolides
Antibiotic for anaerobes and protozoa
Metronidazole
Treatment of PCP
Co-trimoxazole (trimethoprim + sulphamethoxazole)
Penicillins are ineffective against which bacteria?
Bacteria which lack cell walls e.g. Mycoplasma or Chlamydia
1st generation cephalosporin
Cephalexin
2nd generation cephalosporin
Cefuroxime
3rd generation cephalosporin
Cefotaxime
Ceftriaxone
Ceftazidime
How do beta-lactams work?
Weakened cell wall –> bactericidal against rapidly dividing bacteria
Mechanism of action of aminoglycosides e.g. gentamicin
Bind to 30S ribosomal subunit –> prevents elongation of peptide cahin and causes misreading of codons along mRNA –> bactericidal
Side effects of ototoxicity and nephrotoxicity
Aminoglycosides e.g. gentamicin
Mechanism of action of tetracyclines e.g. doxycycline
Binds reversibly to ribosomal 30S subunit –> bacteriostatic
Side effects of photosensitive rash and teeth discolouration of unborn children
Tetracyclines e.g. doxycycline
Mechanism of action of macrolides e.g. erythromycin
Binds to ribosomal 50S subunit –> interferes with translocation –> bacteriostatic
Chloramphenicol mechanism of action
Binds to 50S subunit of irbosome, inhibits peptide bond formation during translocation –> bacteriostatic
Side effects of aplastic anaemia and grey baby syndrome
Chloramphenicol
Side effect of orange secretions
Rifampicin
Mechanism of resistance to beta-lactam antibiotics in Staph. aureus and Gram negative bacilli (coliforms)
Inactivation: Beta lactamases
Mechanism of resistance to beta-lactam antibiotics in MRSA
Altered target: mecA gene encodes a novel PBP (2a). Low affinity for binding beta-lactams.
Mechanism of resistance to beta-lactam antibiotics in Strep. pneumoniae
Altered target: Acquisition of a series of stepwise mutations in PBP genes
Mechanism of resistance to cephalosporins in E.coli and Klebsiella
ESBLs
Mechanism of resistance to macrolides
Altered targets: modification of 23s RNA redues binding of antbiotics
Broad spectrum antibiotics
Co-amoxiclav, Tazocin, Ciprofloxacin, Meropenem
Narrow spectrum antibiotics
Flucloxacillin, Metronidazole, Gentamicin
Four mechanisms of antibiotic resistance
BEAT:
Bypass antibiotic-sensitive step in pathway e.g. MRSA
Enzyme-mediated drug inactivation e.g. beta-lactamases
Impairment of Accumulation of the drug e.g. tetracycline resistance
Modification of the drug’s Target in the microbe e.g. quinolone resistance
Antibiotic for skin infections
Flucloxacillin (S. aureus)
Antibiotic for pharyngitis
Benzylpenicillin 10 days (group A beta haemolytic strep aka Strep. pyogemes)
Antibiotic for invasive Group A Strep.
Clindamycin + early debridement + IVIG
Antibiotic for mild CAP
Amoxicillin
Antibiotic for severe CAP
Co-amoxiclav + clarithromycin
Antibiotic for HAP
Cephalosporin e.g. cefurozime
Antibiotic for bacterial meningitis
Ceftriaxone
Add amoxicillin if Listeria likely (young/old)
Antibiotic for meningitis
Cefotaxime + Amoxicillin
Antibiotic for simple community cystitis
Trimethoprim 3 days
Antibiotic for hospital acquired UTI
Cephalexin or augmentin
Antibiotic for severe sepsis
Cefuroxime, metronidazole +/- gentamicin
Antibiotic for neutropenic sepsis
Tazocin + gentamicin
Antibiotic for C. diff
PO Metronidazole first line
PO Vancomycin second line
Organisms causing UTI
E. coli
Proteus mirabilis
Klebsiella
Staphylococcus saprophyticus
Treatment of pyelonephritis
IV cefuroxime +/- gentamicin
IV co-amoxiclav +/- gentamicin
Infection indicated by what amount of bacteria in urine?
> 10^5 cfu/mL
Acid fast, non-motile, bacilli
Mycobacteria
Auramine or Ziehl-Neelsen staining
Mycobacteria
Swimming pool granuloma
Mycobacteria marinum
Chronic progressive painless ulcer
Mycobacteria ulcerans
Slow-growing non-tuberculous (atypical) mycobacteria
Mycobacterium avium intracellulare
M. marinum
M. ulcerans
Fast-growing non-tuberculous (atypical) mycobacteria
M. abscessus
M. chelonae
M. fortuitum
Multifocal bronchiectasis with multiple small nodules
Mycobacterium avium intracellulare
Culture medium for TB
Lowenstein Jensen
TB treatment regime
RIPE for 2 months: rifampicin, isoniazid (+ pyridoxine), pyrazinamide, ethambutol
RI for 4 months: rifampicin + isoniazid
Rifampicin side effects
Orange secretions
Raised transaminases
Induces cytochrome P450
Isoniazid side effects
Peripheral neuropathy (give B6 pyridoxine) Hepatotoxicity
Pyrazinamide side effects
Hepatotoxicity, hyperuricaemia
Ethambutol side effects
Visual disturbance
Treatment of TB meningitis
Continue rifampicin and isoniazid for additional 2-4 months
Latent TB treatment
6 months isoniazid
What is BCG vaccine?
Attenuated M. bovis
Causative organism of leprosy
Mycobacterium leprae
Mycobacterium lepromatosis
Infective cause of flaccid paralysis
Clostridium botulinum
Causes of meningitis in neonates
Group B Strep.
E. coli
Listeria monocytogenes
Cause of meningitis
Haemophilus influenza B
Causes of meningitis >5 yo
Neisseria meningitidis Streptococcus pneumoniae (leading cause in adults in UK)
Causes of aseptic meningitis
Coxsackie group B
Echoviruses
India ink stain
Cryptococcus neoformans
Encephalitis with gram +ve rod
Listeria
ARVs for pregnant & BF women
Tenofovir
Lamivudine
Efavirenz
ARVs for BF infants
Nevirapine
ARV for untreated women with HIV at childbirth
Nevirapine
Treatment for hep. B
Interferon alpha 2a
Lamivudine
Tenofovir
Used to prevent RSV in children with heart and lung disease
Ribavirin (guanosine analogue)
Treatment of CMV
Gancyclovir
Treatment of influenza A
Amantadine
Treatment of influenza A and B
Zanamivir
Nucleoside analogue which inhibits reverse transcriptase
Zidovudine
Rusty coloured sputum
Streptococcus pneumoniae
Atypical pneumonia + cold agglutinins
Mycoplasma pneumoniae
Rose spots in pneumonia
Chlamydia psittaci
Most common triggers of erythema multiforme
- HSV
2. Mycoplasma pneumoniae
GI infection + descending paralysis
Clostridia botulinum (give antitoxin)
Vacuum packed / canned foods –> GI infection
Clostridia botulinum
Watery diarrhoea and cramps, systemic illness, 8-16 hours after eating reheated meat.
Clostridia perfringens
Gas gangrene
Clostridia perfringens
Reheated rice –> sudden vomiting (4 hrs) +/- watery diarrhoea
Bacillus cereus
Prominent vomiting + watery diarrhoea. Virulence factor protein A. Catalse, coagulase +ve. Tetrads, clusters on gram stain. Beta haemolytic on blood agar. Enterotoxin –> IL-1 and IL-2.
Staph. aureus
Gram -ve, toxigenic, travellers diarrhoea acting on jejunum and ileum
Enterotoxigenic E. coli (ETEC)
Gram -ve, invasive dysentery
Enteroinvasive E. coli (EIEC)
Gram -ve, haemorrhagic dysentery, caused by verotoxin
EHEC
Anaemia, thrombocytopenia and renal failure
HUS
HUS
E. coli 0157:H7
Gram -ve, infantile diarrhoea
EPEC (E. coli)
Treatment of E. coli
Self-limiting but can treat with ciprofloxacin
Facultative anaerobes, oxidase negative
E. coli
Slow onset fever + constipation + relative bradycardia. Splenomegaly, rose spots, anaemia and leukopenia.
Salmonella typhi / paratyphi
Treatment of Salmonella
Ceftriaxone or ciprofloxacin
Self-limiting diarrhoea after poultry, eggs, meat
Salmonella enteritides
Painful bloody diarrhoea, mucosal inflammation and fever, distal ileum and colon
Shigella (shiga enterotoxin)
Entercolitis, mesenteric adenitis w/ necrotising granulomas, reactive arthritis and erythema nodosum.
Yersinia enterocolitis
4C cold enrichment
Yersinia enterocolitis
Poo from domestic animals
Yersinia enterocolitis
Rice water stool
Vibrio cholerae
Shellfish
Vibrio cholerae
Comma shaped, late lactose fementers, oxidase positive
Vibriosis
Massive diarrhoea without inflammation. Cl- efflux.
Vibrio cholerae
Cellulitis in shellfish handlers. Fatal septicaemia wiht D&V in HIV pts.
Vibrio vulnificus (treat with doxycycline)
Ingestion of raw undercooked seafood (Japan). 3 days of diarrhoea. Often self-limiting.
Vibrio parahaemolyticus (treat with doxycycline)
Unpasteurised milk
Campylobacter jejuni
Headache and fever, abdo cramps, bloody (foul smelling) diarrhoea
Campylobacter jejuni
Curved, s-shaped, microaerophilic, oxidase +ve, motile, sensitive to nalidixic acid
Campylobacter jejuni
Associated with Guillain Barre and Reiter’s
Campylobacter jejuni
Treatment of Campylobacter jejuni
Erythromycin or cipro if first 4-5 days
GI watery diarrhoea, cramps, headache, fever, little vomiting
Listeria monocytogenes
Refrigerated food (veg) and unpasteurised dairy
Listeria monocytogenes
Treatment of Listeria monocytogenes
Ampicillin, Ceftriaxone, Cotrimoxazole
V or L shaped, beta haemolytic, aesculin +ve, tumbling motility
Listeria monocytogenes
Mobile trophozoite in diarrhoea (protozoa)
Entamoeba histolytica
Flask-shaped ulcer on histology
Entamoeba histolytica
MSM, RUQ pain (liver abscess), chronic weight loss
Entamoeba histolytica
Treatment of entamoeba histolytica
Metronidazole + paromomycin if luminal disease
Pear-shaped trophozoite (protozoa)
Giardia lamblia
Travellers, hikers, MSM, with foul smelling non-bloody diarrhoea
Giardia lamblia
Treatment of Giardia
Metronidazole
Severe diarrhoea in immunocompromised, infects jejunum
Cryptosporidium parvum
Oocysts seen in stool by modified Kinyoun acid fast stain
Cryptosporidium parvum
Treatment of Cryptosporidium parvum
Paramomycin
Anaerobic GI infection
Clostridia
Aerobic GI infecion
B. cereus
S. aureus
Lactose fermenters
E. coli
Non-lactose fermenters
Salmonella
Shigella
Yersinia
Protozoa
Entamoeba histolytica Giardia lamblia Cryptospordium Malaria Trpyanosomiasis Leishmaniasis
Causes of secretory diarrhoea (no fever, no WBC in stool sample)
Vibrio cholerae ETEC EAEC EPEC EHEC
Causes of inflammatory diarrhoea (fever, neutrophils in stool sample)
Campylobacter jejuni
Shigella spp.
Salmonella
EIEC
Causes of enteric fever (fever, mononculear cells in stool sample)
Salmonella typhi
Yersinia
Brucella
Cleaves sialic acid residues, allows virion to exit host cell
Neuraminidase activity
Binds sialic acid receptors, membrane fusion and virus entry. Endosomal-viral envelope fusion = release.
Haemogluttinin activity
Mutation of HA/NA to give new strains
Antigenic drift
Complete change of HA/NA (can only occur with influenza A)
Antigenic shift
Cleavage of influenza HA by what causes extended tropism / growth for H5 and H7
Clara tryptase
Antiviral for influenza A
Amantadine (targets M2 ion channel)
Neuraminidase inhibitors (for influenza A and B)
Oseltamivir (Tamiflu)
Zanamivir (Relenza)
Sialic acid
Split or subunit flu vaccine. High risk groups. Short term strain-specific immunity.
Inactivated flu vaccine
Cold adapted virus limited to URT given to children. Broader more cross reactive immunity.
Live attenuated flu vaccine
Treatment for hepatitis C
Interferon alpha 2b
Ribavirin
Hepatitis causing raised AST and ALT
Hepatitis B
Hepatitis causing raised ALT
Hepatitis C
HBsAg
Indicates viral replication in the liver. Active infection (acute or chronic).
HBeAg
Secreted protein. Indicates high level of viral replication and infectivity.
HBcAg
Found only in infected liver cells. Not in blood.
Anti-HBs
Indicates immunity (previous infection or vaccination). Not found in chronic carriers.
Anti-HBe
Indicates low infectivity and reduced viral load
Anti-HBc IgM
Indicates recent infection
Anti-HBc IgG
Indicates previous exposure to HBV (chronic carriers and those who clear it)
Most reliable marker of infectivity in hepatitis B
HBV viral load
Pneumococcal vaccine given to babies
Pneumococcal conjugate vaccine (Prevenar 13)
Pneumococcal vaccine given to 65yo
Purified polysaccharide vaccine (Pneumovax)
Triad of measles presentation
Cough/coryza, conjunctivitis and rash
Koplik’s spots
Measles
Complications of measles
Pnuemonitis Otitis media Severe diarrhoea Convulsions Encephalitis Subacute sclerosing panencephalitis (after 7 yrs)
Measles virus
Morbillivirus
Mumps virus
Paramyxovirus
Complications of mumps
Pancreatitis 4%
Oophoritis 5%
Orchitis 25% of post-pubertal men
Meningitis and deafness
Rubella virus
Togavirus
Rubella presentation
Mild illness, swollen lymph glands, low grade fever, malaise and conjunctivitis. Maculo-papular discreet rash on face/neck/body. Swollen joints and arthritis.
Congenital rubella syndrome triad (first trimester)
Sensorineural deafness, eye abnormalities and congenital heart disease
Guanosine analogue
Aciclovir
Aciclovir used to treat
HSV1 HSV2 VZV
Causes of aciclovir resistance
Mutations in thymidine kinase 95% (Aciclovir not phosphorylated)
Mutations in DNA polymerase 5%
Treatment for ACV-resistant HSV
Foscarnet or Cidofovir
Cause of interstitial pneumonia, retinal exudate and haemorrhage, and owl’s eye inclusions
CMV
Congenital CMV
RCHEP: retinitis, colitis, hepatitis, encephalitis, pneumonitis
Treatment of CMV
IV ganciclovir
IV foscarnet
Cidofovir
Ganciclovir side effect
BM suppression
Foscarnet (pyrophosphate analogue) side effects
Renal impairment and electrolyte disturbance
Cidofovir (nucleoside analogue) side effects
Nephrotoxic
HHV6 causes?
Sixth disease aka exanthem subitum; v. high fever, coryza, sudden rash
HHV8 causes?
Kaposi’s sarcoma and Castleman’s disease
Oseltamivir
Neuraminidase inhibitor (oral)
Zanamivir
Neuroaminidase inhibitor (dry powder inhaler)
Antiviral for influenza A and B
Neuraminidase inhibitors
Amantidine
Inhibits influenza A matrix protein M2
First line treatment regime for Hep B
Peginterferon 2alpha, entecavir, and tenofovir
Entecavir and lamivudine
Inhibitors of viral polymerase (nucleotide analogues)
Tenofovir
Inhibitor of reverse transcriptase (nucleotide analogue)
‘Flying saucer’ shaped cysts on microscopy with Gomori’s methanimine silver stain
PCP
Fever, non-productive cough, weight loss, night sweats. Widespread pulmonary infiltrates.
PCP
Alpha haemolytic gram +ve cocci arranged in pairs
Strep. pneumoniae
Optochin sensitive
Strep. pneumoniae
Optochin insensitive
Strep. viridans
Beta haemolytic gram positive cocci arranged in grape-like clusters. Catalase positive.
Staph. aureus
Headache, myalgia, confusion, rhabdomyolysis, abdominal pain, hyponatraemia, hypophosphataemia, deranged LFTs
Legionella pneumophila
COPD infective exacerbation organism; aerobic gram -ve diplococci.
Moraxella catarrhalis
Chocolate agar
Haemophilus influenzae
Tumbling motility
Listeria
Profuse watery diarrhoea + enterotoxin. cAMP activation.
Vibrio cholerae
Rose spots in gastroenteritis
Salmonella typhi
GI infection, multiples in Peyer’s patches
Salmonella typhi
Meningitis after contact with animals
Leptospirosis (Weil’s syndrome)
Microscopic agglutination test +ve
Leptospirosis
Lymphogranuloma venereum causative organism
Chlamydia trachomatis
Gummatous lesions
Tertiary syphilis
Donovan bodies
Klebsiella granulomatis
Treatment of MRSA
Vancomycin
Treatment for infective exacerbation of COPD
Doxycycline
Spaghetti with meatballs appearance
Pityriasis versicolore
Aspergillosis / aflatoxin cancer association
HCC
Rose gardener’s disease
Sporothrix schenkii (sporotrichosis)
Rocky mountain fever
Rickettsia
Cerebral negri bodies
Rabies
Treatment of EBV-related post-transplant lymphoproliferative disease
Reduce immunosupression
Rituxmab (anti-CD20; B cells)
Spindle cells on biopsy
Kaposi’s sarcoma (HHV8)
Progressive multifocal leukoencephalopthy virus
JC virus
Giant cell pneumoniae
Measles in immunocompromised pt
Serious infections in pregnancy
TORCH: Toxoplasmosis Other: syphilis, parvovirus B19, VZV, influenza Rubella CMV HSV
12 week booking infection screening
Syphilis, Hep B, HIV, rubella
Commonest infectious cause of developmental delay and congenital abnormalities
CMV
Congenital varicella syndrome
VZV limb hypoplasia, microcephaly, scarring
Cf. neonatal varicella (around parturition) - severe disseminated infection
Management of infant of HBsAg +ve mother
HBV vaccine within 12 hours of delivery
Management of infant of HBeAg +ve mother
HBV vaccine within 12 hours of delivery + HBIG at birth
Management of mother with HBV viral load >10^6 copies
Antenatal antiviral therapy (lamivudine or tenofovir) for 6-8 weeks prior to delivery + HBV vaccine for infant within 12 hours of delivery and HBIG at birth
Parvovirus B19 in first 20 weeks
3% risk hydrops fetalis
3 biggest Abx leading to C. diff
3C’s: Clindmycin, Cephalosporins, Ciprofloxacin
Brodies abscess
Subacute osteomyelitis
Definitive host of parasite
Where sexual reproduction takes place
Intermediate host
Parasite in asexual stage
Protozoa
Malaria
Trypanosomiasis
Leishmaniasis
Chagas disease
Trypanosoma cruzi (protozoan)
Treatment for oral thrush
Nystatin
Lobar pneumonia organism
Strep. pneumoniae
Mantoux test >5mm +ve in:
Patients with HIV
A recent contact of a person with TB disease
People with fibrotic changes on chest radiograph consistent with prior TB
Patients with organ transplants
People who are immunosuppressed for other reasons (for example taking the equivalent of >15 mg/day of prednisone for 1 month or longer)
Mantoux test >10mm +ve in:
Recent immigrants (
Mantoux test >10mm +ve in:
Anyone
Pneumonia + red-currant jelly sputum
Klebsiella
Cystic pneumonia following influenza
Staph. aureus
Boat-shaped organisms, silver stain
PCP
Bat’s wings appearance
PCP
UTI in catheterised pt
Klebsiella
Septic arthritis in young person
Neisseria gonorrhoeae
Threadworm treatment
NB: –> pruritis ani
Mebendazole
Negri bodies
Pathognomonic of rabies
Treatment of typhoid
IV ceftriaxone +/- gentamicin
Myalgia, ‘breakbone fever’, retro-orbital pain, sunburn-like rash
Dengue