Microbiology- Part 3 (p59-70- Endocarditis, viruses, wound, bone + joint, UTIs, anti-microbials, paeds, CNS + vaccines) Flashcards by Greg Poyser

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

How well did you know this?

Not at all

Perfectly

Which criteria is used for diagnosing infective endocarditis?

Dukes

How well did you know this?

Not at all

Perfectly

Signs of infective endocarditis?

Heart murmurs that change

Subacute- clubbing, splinter haemorrhages, Osler’s nodes, Janeway lesions, Roth spots, splenomegaly, haematuria

How well did you know this?

Not at all

Perfectly

Infective agents in infective endocarditis?

Subacute bacterial endocarditis- low virulence strep (viridians)
Acute- s.aureus (metastatic infection)- most cases of prosthetic valve endocarditis

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Which animal is the natural reservoir of influenza A?

Ducks

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

What are flu virus strains e.g. H5N1 named after?

Structure of haemoglobin and neuraminidase

How well did you know this?

Not at all

Perfectly

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 well did you know this?

Not at all

Perfectly

How does aciclovir work against HSV?

Guanosine analogue which blocks viral DNA extension through activation by viral thymidine kinase (TK)

How well did you know this?

Not at all

Perfectly

Why does aciclovir not work against CMV?

CMV doesn’t have viral thymidine kinase

How well did you know this?

Not at all

Perfectly

What treatment is used for CMV?

Ganciclovir- nucleoside analogue

How well did you know this?

Not at all

Perfectly

What is the main side effect of ganciclovir?

BM suppression

How well did you know this?

Not at all

Perfectly

What does CMV lead to?

RCHEP
Retinitis 
Colitis
Hepatitis
Encephalitis
Pneumonia

How well did you know this?

Not at all

Perfectly

What is the key feature of CMV cells?

Owls eye inclusions

How well did you know this?

Not at all

Perfectly

What do you use in CMV if ganciclovir doesn’t work or severe SE?

Foscarnet

How well did you know this?

Not at all

Perfectly

How does foscarnet work?

Pyrophosphate analogue- inhibits nucleic acid synthesis without requiring activation

How well did you know this?

Not at all

Perfectly

What is especially used to treat CMV retinitis?

Cidofovir- nucleoside phosphonate (also used in opportunistic post-transplant viral treatment)

How well did you know this?

Not at all

Perfectly

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 well did you know this?

Not at all

Perfectly

How do you treat resistant Herpes?

Foscarnet/cidofovir

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Important side effect of foscarnet and cidofovir?

Nephrotoxicity

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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?

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?

1. Bypass antibiotic-sensitive step in pathway e.g. MRSA 2. Enzyme-mediated drug inactivation e.g. beta-lactamases 3. Impairment of Accumulation of drug e.g. tetracycline resistance 4. 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 ```