Infectious Disease Flashcards
Pneumonia general notion
Pneumococci multiply rapidly in alveolar spaces and induce extensive oedema.
Incite acute inflammatory response in which neutrophils and congestion are prominent.
Alveoli are packed with an exudate composed of neutrophils - O2 cannot get into the alveoli and across into the blood stream.
Present with fever, malaise, tachypnea and tachycardia.
Can present with shock (due to a large drop in blood pressure as the circulation fails resulting in multi-organ failure).
Productive cough (purulent sputum due to dead neutrophils).
Clinical - The patient needs to be assessed urgently by studying their respiratory rate and the oxygen saturation of their blood.
Community acquired pneumonia (CAP)
develops outside the hospital.
Who - primary disease occurring in an otherwise healthy patient or
secondary to a predisposing factor such as chronic lung disease, diabetes mellitus, or malignancy.
Common causes:
Streptococcus pneumoniae Haemophilus influenzae Staphylococcus aureus
The atypicals- Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae
Primary viral pneumonia: Influenza, Parainfluenza, Respiratory syncytial
virus
Other classifications
Hospital acquired pneumonia. Opportunistic pneumonia affects people whose immune status is defective
X-ray PATTERNS of pneumonia
3:
Lobar pneumonia is pulmonary consolidation demarcated by border of lung segment or lobe.
Bronchopneumonia is seen as patchy consolidation around the larger airways.
Interstitial pneumonia is demonstrated by areas of shadowing in the
lung fields and there is usually no sputum production at presentation - mycoplasma, legionella, and viral pneumonia.
Meningitis what is it
inflammation of the meningeal lining of the brain and spine.
plasma is filtered from the blood by the epithelial cells to produce CSF (clear, glucose, few WBCs, protein).
Meningitis causes
BACTERIA
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
VIRUSES
Enteroviruses -Coxsackie viruses A and B, Poliovirus, Echovirus
Herpes simplex virus 1 and 2
FUNGI
Crytococcus neoformans (HIV)
CLINICAL FEATURES OF MENINGITIS
fever, increased pulse rate
a) headache
b) photophobia (difficulty looking at bright lights)
c) vomiting
d) neck stiffness on flexion of the neck system is affected.
e) irritable (progressing to reduced level of consciousness)
Neisseria meningitidis
Who:
young children + YA
Features:
causes meningitis - headaches, photophobia, vomiting
and septicaemia - bacteria in the blood - fever, rash, sepsis (reduced level of
consciousness, tachycardia, low blood pressure, poor peripheral circulation, reduced urine output), DIC.
DIC:
Many small clots so anticoagulants used up so bleeding.
Platelets used up so bleeding into skin so petechiae.
Rash:
Petechiae- 1-2mm, bigger and bluer than thrombocytopenia, tumbler test shows it’s non-blanching
found on lower body, trunk, sclera, mucus membranes
Ecchymoses - subcutaneous haemorrhage, 10mm
Necrosis - less perfusion to peripheries, vascular damage, haemorrhage so amputation of digits
Management:
IV Ceftriaxone
Adenovirus and norovirus
Epidemiology - agents of respiratory disease, which are transmitted via the respiratory route. Also direct contact causes ocular disease.
Clinical significance- replicate well in epithelial cells.
Respiratory tract diseases - pharyngitis in children. Symptoms are cough, sore throat, conjunctivitis
Identification- direct test of stool specimens by ELISA to detect viral antigens.
Norovirus is a small, non-enveloped single stranded RNA virus
cause of acute gastroenteritis outbreaks.
There is no specific treatment available
Transmission is mainly faecal-oral. Can be spread following ingestion of contaminated food, direct person-to-person contact or through contact with contaminated surfaces.
Clostridioides difficile mechanism
Gram-positive anaerobic spore forming bacilli.
Causes - antibiotic associated diarrhoea and colitis
Mechanism - forms spores which are transmitted by contact or faecal-oral route.
After reaching the intestine, bile acids induction of C. difficile spore germination.
production of bacterial cells in the intestine.
When the balance of gut microorganisms is disrupted, C. difficile starts to dominate and colonize the large intestine.
Collagenase and toxins damage the epithelial cells - toxin A (enterotoxin) causes excessive fluid secretion + inflammation and B (cytotoxin) damages protein synthesis and cell.
C diff treatment and prevent spread
Mild - Cessation of antibiotic
Metronidazole (broad-spectrum antibiotic used to treat anaerobic infections - inhibiting bacterial nucleic acid synthesis but does not affect spores) or oral vancomycin (does not cross in the bowel from blood so only give oral to directly act at site of infection)
Severe - IV metronidazole / oral fidaxomicin (inhibits bacterial nucleic acid synthesis and does not affect bacteria that resist C. difficile, only oral) and oral vancomycin
Hand hygiene- soap and water as alcohol does not kill spores.
Disinfect equipment and surfaces
Isolate patient
Use antibiotics judiciously
C diff risk factors + CLINICAL FEATURES + diagnosis
Antibiotic exposure eg cephalosporins, amoxicillin, clindamycin.
older age - over 60
hospitalisation - sharing a room with infected patient
immune suppression
gastric acid suppression
IBD
Mild - diarrhoea, blood in stool, fever, abdominal pain
Severe - Leukocytosis, elevated creatinine, Pseudomembranous colitis
Severe + complicated - ileus, sepsis, perforation, death
Diagnosis -
Stool sample
enzyme immunoassay for glutamate dehydrogenase - produced by C diff and for detecting toxins.
PCR for toxin gene.
MRSA what, where, spread, symptoms, antibiotics
MRSA is a type of Staphylococcus aureus that is resistant to most beta-lactam antibiotics and cephalosporins. Produces penicillin binding protein 2a, which confers resistance to all β lactam antibiotics.
Where - anterior nares are the main ecological niche for S.aureus. Also axillae, groin, and GI tract.
Spread - direct contact with infected person or surfaces
Problems - cause problems if it’s able to enter the body or it infects someone in poor health. MRSA infections can include syndromes of bacteraemia, pneumonia, endocarditis, joint infections, and skin or soft-tissue infections.
Treatment - oral doxycycline then oral co-trimaxozole
MRSA prevention
Active screening of high risk patients and exposed healthcare workers for carriage.
Strict implementation of transmission based precautions - mainly better hand hygiene
Treatment of carriage using topical applications of mupirocin nasal cream (a topical antibiotic) and washing with disinfectant agent, such as Stellisept® or chlorhexidine.
