Microbiology- Part 3 (p59-70- Endocarditis, viruses, wound, bone + joint, UTIs, anti-microbials, paeds, CNS + vaccines) Flashcards
Key features of infective endocarditis history?
Fever
Non-specific- anorexia, weight loss, malaise, fatigue, rigors, night sweats
Acute- SOB, chest tightness, embolic complications
Dental Hx- Route of infection
PMH for RF- RhF, congenital heart disease, valve replacementi
Which criteria is used for diagnosing infective endocarditis?
Dukes
Signs of infective endocarditis?
Heart murmurs that change
Subacute- clubbing, splinter haemorrhages, Osler’s nodes, Janeway lesions, Roth spots, splenomegaly, haematuria
Infective agents in infective endocarditis?
Subacute bacterial endocarditis- low virulence strep (viridians)
Acute- s.aureus (metastatic infection)- most cases of prosthetic valve endocarditis
Treatment of infective endocarditis?
Blood cultures vital for guiding treatment
Prosthetic valve- van + gent + Rifampicin
Native valve:
acute- flucloxacillin
Indolent- Pen + gent
Strep viridians- benzylpenicillin + gent
MRSA- vancomycin
What are the different flus that affect humans throughout the year?
Influenza A (H1)- beginning of Jan Influenza A (H1N1)- (end of Dec) Influenza B- peaks March
Which animal is the natural reservoir of influenza A?
Ducks
What RNA segments are influential in flu transmission and what do they do?
Neuraminidase- cleaves sialic acid residues exposing receptors on host cells and disrupts the mucin barrier
Haemogglutinin- binds sialic acid receptors and allows viral entry
What are flu virus strains e.g. H5N1 named after?
Structure of haemoglobin and neuraminidase
What antivirals are used for influenza?
Amantadine (Influenza A only)- targets M2 ion channel but single mutation leads to resistance
Neuraminidase inhibitors- Oseltamivir (Tamiflu), zanamivir (Relenza), sialic acid- effective only <48h
How does aciclovir work against HSV?
Guanosine analogue which blocks viral DNA extension through activation by viral thymidine kinase (TK)
Why does aciclovir not work against CMV?
CMV doesn’t have viral thymidine kinase
What treatment is used for CMV?
Ganciclovir- nucleoside analogue
What is the main side effect of ganciclovir?
BM suppression
What does CMV lead to?
RCHEP Retinitis Colitis Hepatitis Encephalitis Pneumonia
What is the key feature of CMV cells?
Owls eye inclusions
What do you use in CMV if ganciclovir doesn’t work or severe SE?
Foscarnet
How does foscarnet work?
Pyrophosphate analogue- inhibits nucleic acid synthesis without requiring activation
What is especially used to treat CMV retinitis?
Cidofovir- nucleoside phosphonate (also used in opportunistic post-transplant viral treatment)
What is a good way to remember how to treat herpes?
If you get herpes, you need to Act Very Fast- Aciclovir, Valaciclovir, Famciclovir
How do you treat resistant Herpes?
Foscarnet/cidofovir
How is CMV treated in BMT?
- Preemptive therapy- monitor CMV viral load in blood
- Acute therapy- reduce immunosuppression
a. 1st line- ganciclovir
b. 2nd line- foscarnet
c. 3rd line- cidofovir
Important side effect of foscarnet and cidofovir?
Nephrotoxicity
How do you decide when to treat HBV?
- Serum HBV DNA levels (>2000IU/ml)
- Serum aminotransferase levels (>normal UL)
- Liver biopsy histological grade + stage: Moderate-severe active necroinflammation and/or fibrosis
What is the treatment goal of HBV?
Prevent progression to cirrhosis + HCC
Maintain serum HBV DNA level as low as possible
Treatment options for HBV?
Pegylated interferon alpha 2a- Direct antiviral effect + upregulates expression of MHC on cell surfaces
Nucleos/tide analogues-
a. Inhibitors of viral polymerase- lamivudine, adefovir dipivoxil, entecavir, telbivudine
b. Inhibitor of reverse transcriptase- tenofovir
1st line treatment for HBV?
Entecavir, PegINF alpha 2a and tenofovir
Treatment goal for HCV?
Sustained virologic response- persistent absence of HCV RNA in serum >6/12 after completing antiviral treatment
Prevent progression to cirrhosis, HCC or decompensated liver disease
Treatment for HCV?
PegINFa 2b/2a
Ribavirin (RNA nucleoside analogue)
New options such as sofosbuvir or ledipasavir
- can cure but v expensive
How are respiratory viruses diagnosed?
PCR of BAL/throat swab or NPA
Who do opportunistic infections affect?
Immunodeficient pts- innate (primary) or acquired (malignancy, HIV, steroids, chemotherapy)
What are the three stages of PCR?
Denature
Primer annealing
Chain elongation (with Taq polymerase)
Name three origins of opportunistic viral infections post-transplant?
Reactivation of latent infection- Herpes
Graft brought infection with it- Hep B
Exogenous opportunistic infection post-transplant e.g. measles
Varicella has a high risk of which complications in immunocompromised?
Pneumonitis
Hepatitis
What does EBV cause in HIV pts?
Oral hairy leukoplakia
Lymphomas
Which virus is responsible for KS in AIDS patients?
HHV8
What is seen on biopsy of KS?
Presence of spindle cells
KSHV proteins
Which bugs are commonly responsible for surgical site infections?
STAPH AUREUS
E. coli
Pseudomonas
Haemolytic strep
Treatment for wound infection with staph aureus?
Flucloxacillin
Aetiology of septic arthritis?
Abnormal joint (RA) or immunosuppression + bacteraemia (diabetes or IVDU)
Which bugs cause septic arthritis?
STAPH AUREUS, STREP, some gram negatives
How does septic arthritis present?
Unwell febrile pt with red hot swollen joint (50% knee)
How is septic arthritis diagnosed?
Blood culture before Abx, joint aspirate (>50k cells/mm^3), inflammatory markers
Treatment of septic arthritis?
IV antibiotics (cephalosporin or flucloxacillin) + drain joint
What is the aetiology of osteomyelitis?
Local or haematogenous spread- brodie abscess -> frank osteomyelitis
What bug causes osteomyelitis?
Staph aureus
Presentation of osteomyelitis?
Pain, fever, local swelling
How is osteomyelitis diagnosed?
MRI best imaging, bone biopsy for culture/histology
Treatment of osteomyelitis?
Abx treat most cases- if not, debridement
Why are UTIs more common in women?
Short urethras
What bugs commonly cause UTIs?
E. COLI, proteus, klebsiella, staph saprophyticus
How do UTIs present?
Frequency, dysuria, abdo/flank pain
How are UTIs diagnosed?
Clinical, dipstick (nitrite, leucocytes +ve, MSU M,C+S
How are UTIs treated?
Trimethoprim or nitrofurantoin
Which antimicrobials inhibit cell wall synthesis?
Beta-lactams (penicillins, cephalosporins and carbapenems)
Glycopeptides (e.g. vancomycin)
Which antimicrobials inhibit protein synthesis?
Aminoglycosides (gentamicin), tetracyclines (doxycline), macrolides (erythromycin)
Which antimicrobials inhibit DNA synthesis?
Fluoroquinolones (cipro)
Nitroimidazoles (metronidazole)
Which antimicrobials inhibit RNA synthesis?
Rifamycin (rifampicin)
Which antimicrobials use a cell membrane toxin?
Polymyxin (colistin) Cyclic lipopeptide (daptomycin)
Which antimicrobials inhibit folate metabolism?
Sulfonamides
Diaminopyrimidines (Trimethoprim)
What are penicillins used to treat?
Gram-positive bacteria
What is vancomycin used to treat?
MRSA
What is gentamicin used to treat?
Gram negative sepsis
What is doxycycline used to treat?
Chlamydia
What is erythromycin used to treat?
Gram +ve (Penicillin allergy)
What is chloramphenicol used to treat?
Bacterial conjunctivitis
What is ciprofloxacin used to treat?
Gram -ve
What is rifampicin used to treat?
TB
What is trimethoprim used to treat?
UTIs
Give examples of antibiotics which are considered broad spectrum?
Co-amoxiclav, tazocin, ciprofloxacin, meropenem
What are the four ‘BEAT’ mechanisms of antibiotic resistance?
- Bypass antibiotic-sensitive step in pathway e.g. MRSA
- Enzyme-mediated drug inactivation e.g. beta-lactamases
- Impairment of Accumulation of drug e.g. tetracycline resistance
- Modification of drug’s Target in the microbe e.g. quinolone resistance
What antibiotic is used to combat staph skin infection?
Topical flucloxacillin
Which antibiotic is used to treat pharyngitis caused by beta-haemolytic strep?
Benzylpenicillin
Which antibiotic is used to treat a mild CAP?
Amoxicillin
Which antibiotics are used to treat severe CAP?
Co-amoxiclav + clarithromycin (covers atypicals)
Which antibiotics are used to treat HAP?
Amoxi+Gent or Tazocin
Which antibiotic is used to treat bacterial meningitis?
Ceftriaxone
Which antibiotics are used to treat community UTIs?
Trimethoprim or nitrofurantoin
Which antibiotics are used to treat nosocomial UTIs?
Co-amoxiclav or cephalexin
Which antibiotics are used to treat severe sepsis?
Tazocin/ceftriaxone
Metronidazole +/- Gent
Which antibiotic is used to treat c diff?
Metronidazole
Common congenital infections that are screened for?
TORCH: Toxoplasmosis Other (HIV, HBV) Rubella CMV HSV
How do congenital infections present?
TORCH: Thrombocytopenia Other (ears, eyes) Rash Cerebral abnormality e.g. microcephaly Hepatosplenomegaly
Which organisms can cause early onset sepsis?
GROUP B STREP, E. coli, listeria
How is neonatal sepsis diagnosed?
Septic screen- FBC, CRP, blood culture, deep ear swab, CSF, surface swab, CXR
How is neonatal sepsis treated?
ABC approach
Supportive
Nutrition
Abx- BenPen + Gent
What sort of rash is seen in neisseria meningitidis?
Non blanching petechial
Which type of meningitis commonly presents acutely?
Bacterial
Which type of meningitis presents in chronic fashion- headaches for months?
TB or cryptococcus
Which type of meningitis commonly presents aseptically?
Viral
Which bacteria commonly cause meningitis?
Neisseria meningitidis
Strep pneumoniae
What RFs are there for bacterial meningitis?
Complement deficiency, hyposplenism, hypogammaglobulinaemia, immune defect (alcoholic), infection (pneumonia), entry fracture
How does bacterial meningitis present?
Headache, vomiting, photophobia, irritable, fever, focal neuro signs, rash
How is bacterial meningitis diagnosed?
Clinical + blood cultures, serum-Ag, EDTA-PCR, throat swab, CSF- WCC (polymorphs) and protein raised, glucose decreased
How is bacterial meningitis treated?
Resuscitate! Ceftriaxone and corticosteroids (cover listeria with ampicillin)
If consciousness affected, consider IV acyclovir to cover encephalitis
What would you suspect if the CSF had low glucose, high WCC with polymorphs?
Bacterial infection
If glucose normal but still polymorphs, could be partially treated
What would you suspect if the CSF had normal glucose, high WCC with mononuclear cells?
Viral meningitis/encephalitis
What would you suspect if the CSF had high protein, high WCC with mononuclear cells?
Mycobacterium TB or cryptococcus
How is Hep A transmitted?
Faecal-oral
How is Hep A diagnosed?
Acute- Anti-HAV IgM
Which one of Hep A, B and C isn’t an RNA virus?
Hep B- dsDNA virus
How is Hep B transmitted?
Sexual
Vertical
Horizontal
Blood products
How is Hep B diagnosed?
Raised ALT and AST
HBsAg (Infection or vaccine)
HBeAg (Infectivity)
HBcAb (Acute IgM chronic IgG)
How is Hep B treated?
PegIFNalpha 2a
Lamivudine
Tenofovir
Which condition is associated with polyarteritis nodosa?
Hep B
How is Hep C transmitted?
Blood products
How is Hep C diagnosed?
ALT
Anti-HCV
How is Hep C treated?
PegIFNa2b
Ribavirin
Who can Hep D infect?
Hep B pts
How is Hep E transmitted?
Faeco-oral
How is Parvovirus B19 transmitted?
Resp/Blood-borne
What are the symptoms of parvovirus B19?
Fever, malaise, erythema infectiosum, ‘slapped cheek’, transient aplastic crisis
How does Rubella present?
Flu like symptoms followed by pinpoint maculopapular rash and lymphadenopathy (adults)
How is Rubella diagnosed?
Serology of saliva swabs
Which vaccines do you not give during pregnancy?
Live attenuated- MMR, VZV, Yellow fever
Which bacteria is gram positive cocci clusters + coagulase positive?
Staph aureus
Which bacteria is gram positive cocci clusters + coagulase negative?
Staph epidermis
Which bacteria are gram positive rods?
ABCDL Actinomyces Bacillus (cereus/anthracis) Clostridium Diptheria Listeria
Which bacteria are gram negative cocci?
Neisseria meningitidis/gonnorhoeae
Moraxella
Which bacteria are gram negative rods?
EESY Enterobacteriaceae E. Coli, Salmonella Shigella, Klebsiella Yersinia