Respiratory tract infections Flashcards
Pneumonia When how frequent background
significant proportion of workload in the community and hospital, especially in Winter (UK GPs 10-20% of patients; Hospital 30,000 admissions/yr & 30% of HAI) •Also contributes to lost working days •Pneumonia is a major contributor to death in patients with debilitating diseases
main bacterial pathogens in the respiratory tract
•Gram positive cocci:
–Streptococcus pneumoniae (‘pneumococcus’) – sinusitis, OM, exacerbation COPD, pneumonia
–Staphylococcus aureus – sinusitis, OM, post-influenza pneumonia, lung abscess
– Strep pyogenes (=Group A Strep) Sore throat
•Gram positive rods:
–Corynebacterium diphtheriae - Diphtheria
•Gram negative rods:
–Haemophilus influenzae - sinusitis, OM, exac.COPD, pneumonia
–anaerobes e.g. Bacteroides - sinusitis, lung abscess, dental
–Legionella pneumophila - Legionnaires’ disease
–Coliforms & Pseudomonas – ‘Opportunist’ & hospital-acquired pneumonia
•Acid fast bacilli:
–Mycobacterium tuberculosis (TB)
Other bacteria in the respiratory tract
- Gram positive cocci: viridans streptococci (commensals);
- Gram positive rods: ‘diphtheroids’ (commensals);
- Gram negative cocci: Moraxella (occ. pathogen), Neisseria spp (commensal but NB N. meningitidis)
- Gram negative rods: Bordetella pertussis (whooping cough);
- Acid fast bacilli: Mycobacterium avium complex (MAC), Mycobacterium kansasii
- Other species: Mycoplasma pneumoniae, Chlamydophila (Chlamydia) pneumoniae, Chlamydia psittaci
Fungi in the resp tract
- Yeast – Candida (oral candidosis)
- Yeast – Cryptococcus (occ. pneumonia [+meningitis] in AIDS)
- Aspergillus (sinusitis, invasive aspergillosis disease in leukaemics)
- Mucor (mucormycosis - destructive sinusitis)
- Histoplasma (histoplasmosis - tropical)
- Pneumocystis (pneumonia in AIDS)
rare respiratory pathogens
Nocardia (lung & CNS abscesses)
- Bacillus anthracis (skin & pulmonary anthrax)
- Actinomyces (oral/lung/uterine actinomycosis)
- Others: Coxiella burnetii (Q fever), Melioidosis, coccidioidomycosis etc
Causes of PHARYNGITIS
Cause by: ** Viruses (70+%) Bacteria (10-30%)**
streptococcal sore throat
- Caused by Streptococcus pyogenes (Gp A strep, ß-haemolytic s) [Strep types C & G - sore throat]
- Carriers 1 to 5% esp children; causes 15 - 30% of sore throats
- Difficult to distinguish from viral, clinically but can be more severe, with lymphadenopathy, feels generally unwell
- Penicillin V often given, or amoxicillin – may reduce duration and the complications (glomerulonephritis, rheumatic fever, scarlet fever)
•NO resistance to penicillin
•Erythromycin or clarithromycin an alternative – but NB 10% resistance
Rheumatic fever
•Strep pyogenes pharyngitis, any type, 5 - 16 y old up to 30 y. 2-3 w after.
- Major manifestations: arthritis (flitting polyarthritis, larger joints), carditis, chorea, rash (erythema marginatum), nodules.
- Minor: fever, previous episode, raised ESR/CRP, ECG abnormalities, arthralgia
- Aschoff bodies in heart (10% carditis), prolonged P-R interval, murmurs
- ASO ASB titres, throat swab, ECHO (may be nodules on valves)
Glomerulonephritis
•Strep pyogenes pharyngitis or skin infeciton, 1-5 y old. 10-14 days after. Certain Griffiths types
•Abrupt fever malaise loin pain, oedema of feet & face, haematuria & proteinuria , oliguria
- Impaired renal function
- Almost always resolves without specific treatment
•Immune complexes in glomerular basement membrane
•Other causes: hepatitis, EBV, atypical pneumonias etc; drugs
Scarlet fever
•Mostly secondary to pharyngitis (can be ‘surgical scarlet fever’ – wound; due to erythrogenic toxin A B or C (Streptococcal Pyrogenic Exotoxins). Probably synergy with other strep toxins. 10% GAS produce them
•Incubation 2 to 4 d.
- Onset: sudden fever; rash follows 12-48 hours after the fever
- Prodrome: sore throat, fever, headache, vomiting, abdominal pain, myalgia, tachycardia with the fever. Rash neck first, chest & scapular regions. Trunk and legs later.
- It has a coarse texture like sandpaper, punctate on a diffuse erythematous base
- Circumoral pallor
- Rash for several days; may appear more prominent in skin creases with confluent petechiae esp axillae and groin “Pastia’s lines”.
- Skin desquamation
DIPHTERIA
Caused by Corynebacterium diphtheriae var gravis, intermedius or mitis
Laryngeal, pharyngeal, rare – nasal, skin
Resp tract obstruction, myocarditis, neuropathy (cranial nerves, peripheral)
Clinical diagnosis first, then swabs
C. diphtheriae causes disease by producing diphtheria toxin
Treatment: Airway, anti-toxin, penicillin or erythromycin
QUINSY (peritonsilar abscess)
Mixed organisms esp. anaerobes, Staphylococcus aureus & oral flora.
Presents as increasing discomfort on swallowing, unilaterally enlarged tonsil. Clinical diagnosis only.
Treatment: Antibiotics e.g. co-amoxiclav (‘Augmentin’) and stick the point of a taped scalpel in it (after a bit of anaesthetic spray).
other infections presenting with pharyngitis
Haemophilus influenzae capsulate type b causes very rapid, life-threatening epiglottitis in young children. Respiratory obstruction occurs in hours. Rare now because of Hib vaccine.
Treat cefotaxime or ceftriaxone stat, or chloramphenicol, plus call an anaesthetist
RARE causes of pharyngitis
- LEMIERRE’S DISEASE (anaerobic pharyngitis plus septicaemia in adolescents);
- RETROPHARYNGEAL ABSCESS;
- VINCENT’S ANGINA (acute necrotising ulcerative gingivitis);
- GONOCOCCAL PHARYNGITIS;
- CHLAMYDIAS & MYCOPLASMAS & YERSINIA.
- Candida NB non-infectious causes e.g neutropenia, Bechet’s disease, SLE.
INFECTIONS AT SITES ASSOCIATED WITH THE URT
sinusitis
- Viral URTI leads to temporary cilial defect or direct mucous membrane damage. Blockage of ostium esp. maxillary sinuses. Diving & allergy also lead to sinusitis.
- Pain headache purulent discharge; occasional facial cellulitis as well, in children.
- Organisms: Haemophilus influenzae, pneumococcus, anaerobic streptococci, Moraxella catarrhalis
- Diagnosis – mostly clinical
- Treat – amoxicillin or Augmentin or Erythro
- Complications: Frontal sinusitis leading to cerebral abscess - often a strep (e.g. Strep milleri) +/- anaerobes
otitis media
Fluid in middle ear, with symptoms (pain, hearing loss, fever, lethargy, irritability; red and bulging tympanic membrane).
20% of all children under 5 y have an episode of middle ear infection. Less common in adults.
Risk of recurrence; repeated attacks may lead to permanent hearing loss.
- Organisms: mainly Haemophilus influenzae and Streptococcus pneumoniae, also Moraxella, Streptococcus pyogenes (group A streptococcus), Staph aureus.
- Diagnosis – mostly clinical
- Treat – amoxicillin or Augmentin or Erythro
•Complications… meningitis esp. pneumococcal
Otitis externa
Irritation and suppuration of the external auditory meatus, sometimes with pain
•Organisms: mainly Staph aureus; also Group A strep; occasionally Pseudomonas (swimmers) and fungi.
–If pneumococcus & haemophilus isolated – probable tympanic membrane rupture from otitis media
- Diagnosis – mostly clinical, plus a swab
- Treat – cleansing & ear drops, flucloxacillin if Staph aureus
- ‘Malignant otitis externa’ Pseudomonas – rare severe invasive otitis, necrotising, can spread to temporal bone, life threatening: mainly diabetics, immunocompromised.
MAstoidits
- Now quite rare in the post-antibitoic era
- Severe infection of mastoid follows otitis media
- Hearing loss pain and fever then swelling redness and tenderness over the mastoid bone
- May be associated with tympanic membrane perforation and discharge of pus
- X-ray
- Same organisms and treatment as for otitis media but always antibiotics
- If a prolonged course- may be Gram negs e.g. coliforms
Laryngitis to bronchits and things inbetween
•Acute exacerbation of chronic bronchitis
Often in wintertime, may progress to pneumonia
Streptococcus pneumoniae, Haemophilus, Mycoplasma
Sputum colonised long-term, becomes purulent
GPs use amoxicillin, tetracycline, Augmentin, erythro
• Bordetella pertussis - whooping cough – NB lung damage, early erythromycin, prophylaxis for sibling, vaccine
Bordetella pertusis
- The incubation period is on average 7-10 days (range from 5-21 days) and the infectious period is for 21 days after the onset of symptoms.
- Highest incidence - infants. Young infants: severe complications, hospitalisation and death. Adults and older children can be source of infection.
- Protection not life-long, individuals can get re-infected and spread infection to others.
- After whooping cough vaccination, infection in fully vaccinated individuals is normally very mild.
Early stage – like a cold. 1-2 weeks
- Paroxysmal stage - intense bouts of coughing, thick sputum
- a ‘whoop’ sound with each sharp intake of breath after coughing; vomiting after coughing, especially in infants and young children
- tiredness and redness in the face from the effort of coughing
•Diagnosis: clinical + pernasal swab; PCR; serology
isolating bordatella pertusis for culture
A fastidious, gram-negative bacterium requiring special media for isolation.
•B. pertussis produces multiple antigenic and biologically active products including:
- Pertussis toxin
- Filamentous hemagglutinin (FHA)
- Agglutinogens
- Adenylate cyclase
- Pertactin
- Tracheal cytotoxin
The bacteria attach to the cilia of the respiratory epithelial cells, produce toxins that paralyse the cilia, and cause inflammation of the respiratory tract, which interferes with the clearing of pulmonary secretions.
•Until recently, it was thought that B. pertussis did not invade the tissues; however, recent studies have suggested that the bacteria are present in alveolar macrophages.
Tx of B. pertussis
vaccines
Treatment & prophylaxis: macrolides e.g. erythromycin, clarithromycin, azithromycin
•Vaccine: older whole-cell, newer subunit ‘acellular’ combined with other vaccines
UK immunisation schedule
•2 months
5-in-1 (DTaP/IPV/Hib) vaccine –diphtheria, tetanus, whooping cough (pertussis), polio and H. influenzae type b; Pneumococcal conjugate vaccine (PCV) ; Rotavirus vaccine.
•3 months
DTaP/IPV/Hib – 2; Meningitis C, Rota – 2
•4 months
DTaP/IPV/Hib – 3; PCV-2
•Between 12 and 13 months
Hib/Men C booster; Measles, mumps and rubella (MMR) vaccine; PCV-3
- Later years: various boosters
- 65 and over
Flu (every year); Pneumococcal (PPV: not conjugate) vaccine
•70 years
Shingles vaccine
TReatment of CA pneumonia
Home or admitted to hospital (but not severe, social/other admission with CAP, or no previous therapy)
Amoxicillin 0.5g-1.0g tds
OR Erythromycin
OR Clarithromycin
OR Doxycycline
TReatment of CA pneumonia NOT SEVERE
IN HOSPITAL
Amoxicillin AND [Erythromycin OR Clarithromycin OR Doxycycline]
Note: Hospitals tend to use amox + doxycyline because macrolides promote MRSA by selection. Modify therapy if blood cultures etc positive.
SEVERE CAP treated in HOSPITAL
•Co-amox 1.2g tds… IV AND Doxycycline orally OR Erythromycin OR Clarithromycin IV
Can ADD Rifampicin if severe Legionnaires’ disease OR Levofloxacin 0.5 g od plus Ben Pen 1.2 g qds
•Early HAP or Aspiration pneumonia e.g. post-op chest infection/pneumonia
AS FOR CAP
Late HAP or Late Aspiration pneumonia
Piperacillin-tazobactam [‘Tazocin’], plus dose of gentamicin if severe sepsis/shock
•Severely compromised patients - case by case management
When bacteria idnetified.. ABX:
- Pneumococcus -
- Staph aureus -
- Haemophilus -
- Anaerobes –
- Coliforms, Pseudomonas –
- Legionella –
- ‘Atypicals’ Mycoplamsa, chlamydia -
- TB –
- Aspergillus –
- Pneumococcus - Penicillin (NB can be Pen-R)
- Staph aureus - Flucloxacillin (NB MRSA)
- Haemophilus - Amoxicillin [or co-amoxiclav or cephalosporin]
- Anaerobes – Metronidazole
- Coliforms, Pseudomonas – check sens
- Legionella – Erythromycin plus rifampicin OR cipro
- ‘Atypicals’ Mycoplamsa, chlamydia - tetracycline
- TB – RIPE - rifampicin, isoniazid, pyrazinamide & ethambutol (NB MDR strains)
- Aspergillus – Amphotericin B
common bacteria for pneumonia
Streptococcus pneumoniae (pyogenes)
–Haemophilus influenzae
–Staphylococcus
–Anaerobes (aspiration)
uncommon bacteria for pneumonia
–Gram negative bacilli
(from the bowel: Klebsiella pneumoniae, E. coli, Pseudomonas aeruginosa, Acinetobacter)
–Nocardia asteroides/brasiliensis
–Actinomyces –Moraxella catarrhalis