Common infections Flashcards
Classical presentation of acute pneumonia
Fever - due to inflammation Shortness of breath Increased sputum production Pleuretic chest pain Dullness to percussion Bronchial breathing
CURB65
Used for estimating prognosis of pneumonia. Score over 2 = hospital, over 3=ITU
Confusion
Urea >7mmol/l
Respiratory rate >30/min
Blood pressure SBP>90 or DBP <60
Age over 65
Organisms that cause acute pneumonia
Typical:
Streptococcus pneumoniae
Haemophilus influenzae
Staphylococcus aureus
Atypical:
Mycoplasma pneumoniae
Chlamydophila pneumoniae
Legionella sp.
Respiratory viruses
TB
Atypical pneumonia
Pneumonia caused by organisms which do not respond to penicillin or are non-culturable e.g. leigionella, M. pneumoniae, viruses.
Can’t differentiate clinically
Detect with serology (rising Ab levels or urine antigen detection)
What investigations would you carry out in a patient with suspected pneumonia
Blood cultures, sputum if productive cough
Serology (2 samples, 7 days apart, may confirm atypical infection, useful in outbreaks)
Antigen testing (urine)
Pleural fluid sampling (to differentiate other causes of lung disease)
Why would you test a sputum sample in a patient with suspected pneumonia?
If the suspected cause was not a normal commensal of the body e.g. M. pneumoniae, Mtb, Pneumocytis,
Parapneumonic effusion
Pleural effusion associated with bacterial pneumonia, lung abscesses or trauma which introduces organisms into the chest wall.
Pleural inflammation results in exudate forming in the pleural cavity. This has a high neutrophil content.
Pleural effusions are normally sterile but if the bacteria invade the pleural space, inflamation and fibrogenesis result in abscess formation.
Fluid is resorbed and fibroblasts proliferate forming a scar.
Treatment of acute pneumonia
Increased survival if antibiotics given <4hrs
Amoxycillin for mild infection
Clarithromycin for atypical/hospital infection
Severe pneumonia broad spectrum (co-amoxiclav) + clarithromycin
Oxygen, IV fluids (treatment for sepsis)
Gastroenteritis
Inflammation of the stomach and intestinal epithelium
Diarrhoea
passage of liquid stool or frequent passage of normal stool
Food poisioning
vomiting/diarrhoea caused by eating food contaminated with bacteria, bacterial toxins or other substances
Dysentery
Bloody diarrhoea with mucus, tenesmus, pain and fever
Signs of hypovolemia
thirst, dry mucus membranes
low venous pressure
tachcardia
hypotension
Signs of colitis
Abdominal tenderness
bowel sounds
distension
In what patients would investigation of diarrhoea be indicated?
Bloody diarrhoea
Dehydrated patients
If diarrhoea is persistent
Abdominal pain
Fever
Immunocompromised
Risk of C.diff (>60, recent admission, antibiotics)
What investigations would you do in a patient with diarrhoea?
Blood tests
Stool sample (selective agar, grown in selective conditions)
Causes of non-inflammatory diarrhoea
Enteroadherent E. coli
Staph aureus
Bacillus cereus
Clostridium perfringens
Cholera
normally due to the relsease of toxin, rapid onset
Causes of inflammatory diarrhoea
Clostridium difficile (antibiotic related)
Shigella
E. coli
Salmonella
Campylobacter
Common food-borne causes of diarrhoea
Salmonella (poulty/eggs)
Campylobacter (poultry)
E.coli (faecall contaminated food)
Characteristic of cholera
Rice water stool
Rapid loss of fluid
Common causes of viral gastroenteritis
Norovirus
Rotavirus
Detected by EM, Elisa or PCR
Giardia
Caused by giardia lamblia
Causes diarrhoea due to fat malabsorption, atrophy of intestinal villi and loss of disaccharides
Diagnosis my microscopy for cysts or immunoassay
Treat with metronidazole
Subacute endocarditis
Slow progressing endocarditis caused by bacteria from the mouth and GI tract
Progression is subtle
Vasculitic lesions are normally first indication e.g. splinter haemorrhages
Acute endocarditis
Caused by S. aureus
Rapid deterioration, results in valve failure
Investigations for a patient with endocarditis
Blood culture
Echocardiogram (valve lesion or vegetation)
Duke criteria for assessing severity
