Week 6&7 - Clinical microbiology/Infection Flashcards
What is a bacterostatic antibiotic?
Suppresses growth, doesn’t produce sterilisation of infected site. requires additional factors. Immune mediated killing
What is antibiotic spectrum?
The range of bacterial species effectively treated by an antibiotic
What are Beta-lactamases?
Enzymes that lyse and inactivate beta-lactam drugs. secreted by gram - ve or S.aureus
How do beta-lactamase inhibitors work?
They have weak antibacterial activity, but they bind beta-lactamase allowing beta-lactam to work
What are some mechanisms of horizontal gene transfer/Extrinsic mechanisms of resistance?
Conjugation (pilus)
Tranformation (short, fragmented, naked DNA)
Tranduction (bacteriophage)
What are some non-genetic mechanisms of resistance?
Change cell wall permeability
Produce active enzymes to destroy drug
Infect sites where antibiotics cant act
Alter structural target
What might cause Red man syndrome?
Injecting Vancomycin too quickly
What are the antibiotics C.diff is resistant to?
4 C's Clindamycin Cephalosporins Ciprofloxacin Co-amoxiclav
Define Sepsis.
Life threatening organ dysfunction due to a dysregulated host response to infection
What does Clindamycin do?
Protein synthesis inhibitor. 50s ribosome
Effective at stopping exotoxin production. Given in addition in gram +ve toxic mediated infections
What is antimicrobial resistance?
Occurs when microorganisms such as bacteria, viruses, fungi or parasites change in such a way that renders the medication used to clear the infection the microbe causes, ineffective
What is intrinsic resistance?
Innate ability of the bacteria to resist the activity of a antimicrobial agent, through inherent structural or functional characteristics allowing tolerance.
What is antibiotic stewardship?
Systemic approach to safe and effective use of antibiotic. to optimise outcome and minimise harm
What may tetracycline cause if used in pregnancy?
Bone and teeth abnormalities
What may Trimethoprim cause if used in pregnancy?
Neural tube defect
What may nitrofurantoin cause if used in pregnancy?
Haemolytic anaemia
What may aminoglycosides cause if used in pregnancy?
Otoxicity
What Signs might make you think its an infection?
Shiver, sweats, fever
How would you tell if the pharyngitis is bacterial or viral?
Viral has nasal symtoms bacterial doesn’t.
Bacteria has a swollen uvula, white spots on tonsils and a grey furry tongue
How is Norovirus most commonly spread?
Contaminated hands
Why can’s viruses like norovirus be cultured?
Immunity from them only lasts 6-14 weeks
What virus commonly causes outbreaks in paediatric hospital ward?
Rotavirus (incubation 1-3days)
Via respiratory droplets
What type of vaccine is the rotavirus vaccine?
Live attenuated vaccine
What is Community acquired pneumonia?
A result of lung infection by microorganisms and the immune system’s response to the infection
Strep. pneumonia, haemphilus influenza
Mycoplasma pneumonia, legoniella pneumonia
What clinical assessment is used in pneumonia?
CURB65
Confusion, urea >7, resp >30, BP d<60, s<90, age > 65
To determine if septic - SIRS and qSOFA
What is the clinical triad in Meningitis?
Fever
Nuchal rigidity
Altered mental status
Photophobia, headache, purpuric rash (non-blanching)
What prophylaxis is used in meningitis?
Ciprofloxacin or Rifampicin
What treatment would you use for mycobacterium tuberculosis infection?
Rifampicin (6 months) - orange- red urine
Isoniazid (6 months). - Neuropathy
Ethambutol (2 months) - optic neuritis
Pyrazinamide (2months) - gout
How would you treat Syphilis?
Benzathine penicillin
What is the criteria for SIRS? (2 or more)
Temp >38 or <36
WCC >12 or <4 x10^9/L
Tachycardia >90
Tachyopnoea >20
Give examples of alpha-haemolytic strep.
Strep pneumonia, strep viridans
Give examples of Beta haemolytic strep
Group A strep (strep pyogens)
Group B strep (strep agalactiae)
Group D strep (enterococcus)
What does breakpoint mean?
Concentration of antibiotic which defines a species as sensitive or resistant
What is the clinical definition of resistance?
When infection is highly unlikely to respond, even to the maximum dose of antibiotics
Give an example of a Extended spectrum beta lactamase.
Cefotaximase
How would you treat extended spectrum beta lactamase?
Carbapenems
What types of infection does Carbapenemase resistant enterobactericeae cause?
(CRE is gram -ve)
Pneumonia, UTI, bacteaemia, wound infection
What is the key difference between clindamycin and Macrolides.
Clindamycin has no action agains aerobic gram -ve or atypical. It has excellent activity against anaerobes
What are the toxic effects of Chloramphenicol?
Bone marrow suppression, aplastic anaemia, optic neuritis
What is the first choice of antibiotic used in streptococcus infection?
Benzylpenicllin
What is pneomocystitis Jiroveci pneumonia?
Opportunistic infection, caused by a fungal infection in immunocompromised individuals.
An EC pathogen causing interstitial plasma cell pneumonia with foamy exudate in alveoli.
SoB, fever, dry cough, failure to respond to antibiotics
Co-trimoxazole and steroid therapy
What is HIV viral load?
Measure of HIV RNA In the plasma.
Can use it to monitor response to antiretrovirals
What treatment is available for influenza?
Neuraminidase inhibitors - Oseltamivir (PO) or Zanamivir (INH) 2X daily for 5 days
M2 inhibitors - amantadine, Rimantadine
What bacteria causes Syphilis?
Treponema pallidum (gram -ve spirochete) Tx - Benzathine penicillin
What is HIV brain disease?
Consequence of unrecognised, untreated infection and marked immunodeficiency
What is Neutropenic fever?
Single oral temp of 38.3 or a temp of >38, sustained for more than 1 hour in a neutropenic patient
What infections might occur after a solid organ transplant?
Community acquired pathogen - Penumococcus, salmonella, influenza, RSV
Opportunistic - aspergillus, pneumocystis
Donor derived- salmonella, HIV, TB, E.coli, syphilis
Nosocomical infection - CDAD
Reactivaton of infections - HSV, CMV, M.TB
What are the different populations of cells in TB?
Actively growing - Isoniazid
Semi-dormant killed by acid environment - Pyrazinamide
Semi-dormant with spurts of active metabolism - Rifampicin
Completely dormant
What are some clinical complications of infection with the gram -ve bacilli, vibrio cholera?
Profound fluid loss and dehydration:
Hypokalaemia, metabolic acidosis. hypovolaemic shock, cardiac failure
What type of anaerobic, spore forming gram positive bacilli produces a heat labile protein neurotoxin?
Clostridium botulinum
Foodborne botulism: pre-formed toxin in food.
absorbed toxins spread via blood stream and enter peripheral nerves
What gram positive coccobacilli might affect pregnant women?
Listeria monocytogenes
Present with severe infection - meningitis or septicaemia
What are complications of the common cold?
(Viral infection of the upper respiratory tract- Rhinovirus or coronavirus)
Otitis media or sinusitis
What antibiotic is used in treating Gonorrhoea (Nesseria gonorrhoea)
Ceftriaxone IM
What antibiotic would you use after a positive NAAT test for Chlamydia trachomatis?
Doxycycline
What treatment would you start if someone had multi-drug resistant TB?
Pyrazinamide + 4 2nd line Fluoroquinolone Injectable - Amikacin or kanamycin Ethionamide Cycloserine
Define septic arthritis
Inflammation of the synovial membrane of the joint, with effusion into the joint capsule due to infection.
What are the 4 causes of malaria?
Plasmodium falciparum (severe malaria)
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
List some AIDS defining Illnesses
Penumocystic jiriveci pneumonia, invasive cervical cancer, CMV, PML caused by JC virus, lymphoma, PCP, TB
What would you use first line to treat MRSA?
IV vancomycin
If cant try Teicoplanin
What are some adverse effects of beta lactamases?
Hypersensitivity, haemolysis, seizures, infection
What are some SE of trimethoprim?
Hyperkalaemia, raised serum creatinine, rash
What antibiotic might you give if you have a gram positive toxin mediated disease like NF or Toxic shock syndrome?
Clindamycin
What antibiotic could you use for multidrug resistant bacteria?
Carbapenem
If SIRS is confirmed, what test could you perform to confirm sepsis?
qSOFA - quick sequential organ failure assessment
Confusion, hypotension, tachypnoea
What might long term use to Metronidazole cause?
Peripheral neuropathy
What are some causes of pneumonia?
Typical - strep pneumonia. Haemophilus influenza, moraxella catarrhalis
Atypical (malaise, myalgia, headache) - Legionella pneumonia (neurological Sx, urinary antigen test), mycoplasma pneumonia, chlamydophila pneumonia
What test can you perform to examine for nuchal rigidity?
Brudzinski sign - spontaneous flexion of the hips when the neck is flexed passively
Also Kernig sign which is reluctance to allow full extension of the knee when hip flexed at 90
List some risk factors for Strep pneumonia Bacterial meningitis?
head injury, middle ear disease, 70% have an underlying disorder, neurosurgery, alcohol, immunosuppression
Give some contra-indications for a lumbar puncture
Infection at the LP site Reduced GCS Coagulopathy Seizures, sepsis Papilloedema
What might the JC virus cause?
Progressive multifocal leukencaphalopathy
- progressive motor dysfunction
What might toxoplasma gondii cause?
intra-cerebral toxoplasmosis
headache, seizures, focal CNS signs
What are some triggers for meningitis?
Infection - HSV, N. meningitis
AI disease e.g. lupus
Adverse drug reactions
What may be present on a TB histology?
Ceaseating granuloma
Constitutional Sx are really important in the presentation of TB, list some.
Night sweats, fever and chills, fatigue, lymphadenopathy, loss of appetite, weight loss
What tests might you perform to test for TB?
m.tb - mycolic acids, mannose-capped LAM is a major immune stimulator during infection
Mantoux- tuberculin skin test
Interfernon gamma release assay
sputum >/= 3 with one early morning sample
Acid fast bacilli on Ziehl-Neelsen stain
What clinical signs may indicate malaria?
Jaundice, anaemia, renal impairment, hepatosplenomagely
Severe malaria - shock, acidosis, pulmonary oedema, seizures
How would you treat Enteric fever?
Quinolones, cephalosporins, azithromycin
Campylobacter can cause inflammation, ulceration and bleeding of the small and large bowel due to bacteria invasion. how would you treat?
- Fluid replacement
- Macrolides - severe and persistent
- Ciprofloxacin or gentamicin for invasive
Where does shigella act?
S. sonnei, S. boydii, S. flexneri, S. dysenteriae
initially watery diarrhoea - bloody
Attaches to and colonises the mucosal epithelium of the terminal ileum and colon. Produces a protein exotoxin (shiva toxin) damaging intestinal ep and glomerular endothelium - renal failure - HUS
