Transcript Respiratory tract infections2013

Upper respiratory tract infections
Lower respiratory tract infections
At the end of this lesson
 You should be able to list :
 the microorganisms responsible from
-upper and lower respiratory tract infections
 The laboratory tests used in the diagnosis
Upper respiratory tract infections
• THE COMMON COLD
• Rhinoviruses and
• Coronaviruses together cause more than 50% of colds
Upper respiratory tract infections
• PHARYNGITIS AND TONSILLITIS:
• About 70% of acute sore throats are caused by viruses
• Bacterial infections:
S. pyogenes (group A β-hemolytic) the commonest and
most important to diagnose because it can lead to
complications , but can be readily treated with
penicillin
Beta-hemolytic colonies
S.pyogenes:-small
A grubu
-great zone of
hemolysis
S. Agalatiae:-büyük koloni
B grubu -küçük zon
Bacteria responsible for pharyngitis
• Strep. pyogenes (group A β-hemolytic)
• Corynebacterium diphtheriae
• Haemophilus influenzae (type B), which occasionally
causes severe epiglottitis with obstruction of the
airways, especially in young children
• Borrelia vincentii together with certain fusiform bacilli,
which can cause throat or gingival ulcers
• Neisseria gonorrhoeae
Complications of S. pyogenes
 Quinsy ( Peritonsillar abscess)
 scarlet fever,
 rheumatic fever,
 rheumatic heart disease and glomerulonephritis
• It is especially important to diagnose Strep. pyogenes
infection by culture because of the possible
complications
• It remains susceptible to penicillin.
• Resistance to erythromycin and tetracycline, however,
is increasing.
• Although during the winter months up to 16% of
schoolchildren carry group A streptococci in the throat
without symptoms, treatment is recommended.
A groubstreptococci
 Rapid antigen test
 Culture
Sample:Throat
 Two swabs
 Convinient transport medium
Rapid antigen test
 Group specific carbohydrate antigen detection
Aglutinasyon negatif
Aglutinasyon pozitif
Rapid antigen test
 Duyarlılık(sensitivite):58-96%
 Özgüllük (spesifisite):63-100%
Throat culture
 Gold standart (Culture)
+
 Antigen test(rapid)
Therefore applied together
Serologic tests
 Streptococcal antibodies:
Poststreptococsic diseases
Antistreptolizin O (ASO)
 In 3-6 weeks the maximum titre
Anti-DNaz B
 In 6- 8 weeks maximum
 In Rheumatic fever in only 80-85% ASO titre is high
 anti-Dnase B should be tested
OTITIS AND SINUSITIS
• Otitis and sinusitis can be caused by many viruses and
a range of secondary bacterial invaders
• Common causes of acute otitis media are viruses,
Strep. pneumoniae and H. influenzae
• This condition is extremely common in infants and
small children, partly because the eustachian
(auditory) tube is open more widely at this age.
Otitis externa
 Staph. aureus,
 Candida albicans and
 Gram-negative opportunists
Acute sinusitis
• The etiology and pathogenesis of acute sinusitis are
similar to those of otitis media.
• It may be possible to identify the causative bacteria by
microscopy and culture of pus aspirated from the
sinus, but sinus puncture is not often carried out.
• In addition, as is the case for otitis media, the patient
can be treated empirically with ampicillin or
amoxicillin, or with the newer oral cephalosporins (e.g.
cefixime) to deal with beta-lactamase-producing
organisms.
ACUTE EPIGLOTTITIS
• generally due to H. influenzae capsular type B
infection
• Acute epiglottitis is most often seen in young children.
• Acute epiglottitis is an emergency and necessitates
intubation and treatment with antibiotics
• The H. influenzae type B (Hib) vaccine greatly reduces
the frequency of this and other infections due to H.
influenzae type B.
ORAL CAVITY
• Saliva flushes the mouth and contains a variety of
antibacterial substances
• Changes in the oral flora produced by broad spectrum
antibiotics and impaired immunity predispose to
thrush
• In the USA and Western Europe, 80-90% of people are
colonized by Streptococcus mutans, which causes
dental caries
• Actinomyces viscosus, Actinobacillus and Bacteroides
spp. are commonly involved in periodontal disease
Lower respiratory tract infections
• Although the respiratory tract is continuous from the nose
•
•
•
-
to the alveoli,
It is convenient to distinguish between infections of the
upper and lower respiratory tract,
even though the same microorganisms might be implicated
in infections of both.
These infections tend to be:
more severe than infections of the upper respiratory tract,
and
the choice of appropriate antimicrobial therapy is
important and
may be life saving.
LARYNGITIS AND TRACHEITIS
• Parainfluenza viruses
• RSV, influenza virus or an adenovirus.
• Diphtheria
-hoarseness and a burning retrosternal pain.
-The larynx and trachea have non-expandable rings of
cartilage in the wall, and are easily obstructed in children
because of their narrowness. Swelling of the mucous
membrane may lead to a dry cough and inspiratory stridor
('crowing') known as croup. Difficulty with respiration may
lead to hospital admission.
• Bacteria such as group A streptococci, Haemophilus
influenzae and Staphylococcus aureus are less common
causes of laryngitis and tracheitis.
DIPHTHERIA
• caused by toxin-producing strains of Corynebacterium
diphtheriae and can cause life-threatening respiratory
obstruction
• now rare in resource-rich countries due to widespread
immunization with toxoid
DIPHTHERIA
• They can colonize the pharynx (especially the tonsillar regions),
the larynx, the nose and occasionally the genital tract.
• The toxin destroys epithelial cells and polymorphs, and an ulcer
forms, which is covered with a necrotic exudate forming a 'false
membrane'. This soon becomes dark and malodorous, and
bleeding occurs on attempting to remove it.
• Nasopharyngeal diphtheria is the most severe form of the
disease. When the larynx is involved, it can result in lifethreatening respiratory obstruction.
• Anterior nasal diphtheria is a mild form of the disease if it occurs
on its own, because the toxin is less well absorbed from this site,
and a nasal discharge may be the main symptom. The patient
will, however, be highly infectious.
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DIPHTHERIA
• Diphtheria toxin can cause fatal heart failure and a
polyneuritis
• Diphtheria is managed by immediate treatment with
antitoxin and antibiotic
• Diphtheria is a life-threatening disease, and clinical
diagnosis is a matter of urgency. As soon as the
diagnosis is suspected clinically, the patient is isolated
to reduce the risk of the toxigenic strain spreading to
other susceptible individuals, and treatment is begun
with antitoxin.
DIPHTHERIA
• The antitoxin is produced in horses, and tests for
hypersensitivity to horse serum should be carried out.
Penicillin or erythromycin is given as an adjunct.
Laryngeal diphtheria may require a tracheotomy to
assist with respiration
• The diagnosis is confirmed in the laboratory by
isolation and identification of the organism
• and demonstrating toxin production by a gel-diffusion
precipitin reaction (Elek test).
Diphtheria toxin
• The genes encoding toxin production are carried by a
temperate bacteriophage which, during the lysogenic
phase, is integrated into the bacterial chromosome.
The toxin is synthesized as a single polypeptide
consisting of: fragment B (binding) at the carboxy
terminal end, which attaches the toxin to the host cells
(or to any eukaryotic cell)
• fragment A (active) at the amino terminal end, which
is the toxic fragment.
WHOOPING COUGH
 Bordetella pertussis
 Pertussis is a severe disease of childhood.
 Bordetella pertussis is confined to humans and is
spread from person to person by air-borne droplets.
 B. pertussis infection is associated with the production
of a variety of toxic factors
WHOOPING COUGH
 B. pertussis infection is characterized by paroxysms of
coughs followed by a 'whoop’
 Whooping cough is managed with supportive care and
erythromycin
 Whooping cough can be prevented by active
immunization
ACUTE BRONCHITIS
• rhinoviruses
• coronaviruses,
• influenza virus,
• Adenoviruses
• Mycoplasma pneumoniae.
• Secondary bacterial infection with Streptococcus
pneumoniae and Haemophilus influenzae may also
play a role in pathogenesis
BRONCHIOLITIS
• Some 75% of bronchiolitis infections are caused by
respiratory syncytial virus
• Bronchiolitis is a disease restricted to childhood, and
usually to children under 2 years of age.
• As many as 75% of these infections are caused by
respiratory syncytial virus (RSV) and most of the
remaining 25% are also of viral etiology, although
Mycoplasma pneumoniae is implicated occasionally.
RESPIRATORY SYNCYTIAL VIRUS
INFECTION
 RSV is the most important cause of bronchiolitis and
pneumonia in infants
 RSV infection can be particularly severe in young
infants
RESPIRATORY SYNCYTIAL VIRUS
INFECTION
• In most children, treatment is supportive, involving hydration,
bronchodilators and, if needing admission to hospital, oxygen.
• The antiviral agent ribavirin, given as an aerosol, has been used
successfully in a number of clinical settings, including children
with severe infection and immunosuppressed individuals at risk
of severe disease.
• A monoclonal antibody, palivizumab, can be used as prophylaxis
to prevent RSV infection in under-2-year-old infants at risk of
severe disease such as those with chronic lung disease,
congenital heart disease or those born at <32 weeks of age.
• At present, there is no vaccine available.
HANTAVIRUS CARDIOPULMONARY
SYNDROME (HCPS)
• The reservoir host for Sin Nombre virus (SNV), a New World
hantavirus, is the deer mouse found commonly in North
America. In 1993, individuals were infected in south-west USA
and developed severe cardiopulmonary disease. HCPS followed
flu-like symptoms as viral invasion of the pulmonary capillary
endothelium led to fluid pouring into the lungs due to increased
vascular permeability, and at least 26 deaths were reported
secondary to pulmonary edema, hypotension and cardiogenic
shock. The route of transmission is by inhaling SNV-infected
rodent feces, saliva or urine. The Old World hantaviruses cause
hemorrhagic fever with renal syndrome. The pathogenesis of
both diseases is thought to involve aberrant immune responses
by SNV-infected endothelial cells that are also involved in
regulating vascular permeability. By 2005, around 380
individuals with HCPS had been reported in the USA, with a
38% mortality rate.
PNEUMONIA
• Pneumonia has long been known as 'the old man's
friend' as it is the most common cause of infectionrelated death in the USA and Europe. It is caused by a
wide range of microorganisms giving rise to
indistinguishable symptoms. The challenge lies not in
the clinical diagnosis of pneumonia - except perhaps
in children, in whom it may be more difficult to
diagnose - but in the laboratory identification of the
microbial cause.
• Microorganisms reach the lungs by inhalation,
aspiration or via the blood
Four types of pneumonia.
• (A) Pneumococcal lobar pneumonia, showing
consolidated alveoli filled with neutrophils and fibrin.
• (B) Mycoplasma bronchopneumonia, with patchy
consolidation in several areas of both lungs.
• (C) Interstitial pneumonia due to influenza virus.
• (D) Lung abscess, showing an abscess cavity in the
lower lobe of the right lung.
Causes of pneumonia related to
age
 Children
 Mainly viral (e.g. respiratory syncytial virus,
parainfluenza) or bacterial secondary to viral
respiratory infection (e.g. after measles)
 Neonates may develop interstitial pneumonitis caused
by Chlamydia trachomatis acquired from the mother
at birth
Causes of pneumonia related to
age
 Adults
 Bacterial causes more common than viral
 Etiology varies with age, underlying disease,
occupational and geographic risk factors
BACTERIAL PNEUMONIA
• Streptococcus pneumoniae is the classic bacterial cause
of acute community-acquired pneumonia
• In the past, 50-90% of pneumonias were caused by
Streptococcus pneumoniae (the 'pneumococcus'), but
the relative importance of this pathogen has decreased
and it now causes only 25-60% of cases Haemophilus
influenzae is estimated to be the cause of 5-15% of
cases, but the true incidence is difficult to determine
because this organism frequently colonizes the upper
respiratory tract of bronchitic patients
BACTERIAL PNEUMONIA
 Streptococcus pneumoniae
 Legionella pneumophila
 Mycoplasma and Chlamydia
 Haemophilus influenzae
 Moraxella catarrhalis
 Staphylococcus aureus
BACTERIAL PNEUMONIA
• Patients with pneumonia usually present feeling
unwell and with a fever
• Pneumonia is the most common cause of death from
infection in the elderly
• Sputum samples are best collected in the morning and
before breakfast
• It is important that the specimen submitted for
examination is truly sputum and not simply saliva.
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The usual laboratory procedures
on sputum
• Gram stain and culture
• a host response in the form of abundant polymorphs and
the putative pathogen, e.g. Gram-positive diplococci
characteristic of Streptococcus pneumoniae .
• The presence of organisms in the absence of polymorphs is
suggestive of contamination of the specimen rather than
infection, but it is important to remember that
immunocompromised patients may not be able to mount a
polymorph leukocyte response. Also, remember that the
causative agents of atypical pneumonia, with the exception
of Legionella pneumophila , will not be seen in Gramstained smears.
Standard culture techniques
• will allow the growth of the bacterial pathogens such as
Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus
influenzae and Klebsiella pneumoniae and other non-fastidious
Gram-negative rods.
• Special media or conditions are required for the causative agents
of atypical pneumonia, including Legionella
• Rapid non-cultural techniques have been applied successfully to
the diagnosis of pneumococcal pneumonia. Detection of
pneumococcal antigen by agglutination of antibody-coated latex
particles can be used with both sputum and urine specimens, as
antigen is excreted in the urine. Use of this technique means the
result is available within 1 h of receipt of the specimen, but
antibiotic susceptibility tests cannot be performed unless the
organisms are isolated.
Microbiologic diagnosis of atypical
pneumonia is usually confirmed
by serology or PCR:
• Mycoplasma pneumoniae:ELISA:IgM
• Legionella pneumophila: Urinary antigen test
• Chlamydophila pneumoniae
Chlamydophila psittaci :Microimmunofluorescence or
ELISA using species-specific antigens
• Coxiella burnetii:ELISA IgM
 Pneumonia is treated with appropriate antimicrobial
therapy
 Prevention of pneumonia involves measures to
minimize exposure, and pneumococcal immunization
post-splenectomy and for those with sickle cell disease
Viral pneumonia
 Influenza A or B
 Parainfluenza (types 1-4)
 Measles
 Respiratory syncytial virus
 Adenovirus
 Adenovirus
 Varicella-zoster virus
PARAINFLUENZA VIRUS INFECTION
 There are four types of parainfluenza viruses with
differing clinical effects
 Adenoviruses cause about 5% of acute respiratory tract
illness overall
NEW viruses:
 HUMAN METAPNEUMOVIRUS
 HUMAN BOCAVIRUS
CYTOMEGALOVIRUS INFECTION
 CMV infection can cause an interstitial pneumonitis in
immunocompromised patients
INFLUENZA VIRUS INFECTION
 Influenza viruses are classic respiratory viruses and
cause endemic, epidemic and pandemic influenza
 There are three types of influenza virus: A, B and C
 There are three types of influenza virus: A, B and C
SEVERE ACUTE RESPIRATORY
SYNDROME-ASSOCIATED
CORONAVIRUS INFECTION
 SARS
Middle East respiratory
syndrome coronavirus (MERSCoV)!
 New virus strain (September 2012): severe acute
respiratory illness occurring in the Arabian
Peninsula, some of whom were transferred for
care to hospitals in Europe.
 This coronavirus differs from the previously
identified coronaviruses such as the SARS
coronavirus (SARS-CoV), which caused the 2003
SARS outbreaks.
 There is still much to be investigated, but it is
considered likely that this virus originated from
an animal source.
Respiratory infection
 Viral detection:
 Antigen detection(RSV/Influenza/Adenovirus)
 Multiplex PCR
CYSTIC FIBROSIS
 Individuals with cystic fibrosis are predisposed to
develop lower respiratory tract infections
 The disease is characterized by pancreatic
insufficiency, abnormal sweat electrolyte
concentrations and production of very viscid bronchial
secretions
 P. aeruginosa colonizes the lungs of almost all 15-20year-olds with cystic fibrosis
LUNG ABSCESS
• Lung abscesses usually contain a mixture of bacteria
including anaerobes (Bacteroides and Fusobacterium )
• Treatment of lung abscess should include an antianaerobic drug and last 2-4 months
• Pleural effusion and empyema :Aspiration of pleural
fluid provides material for microbiologic examination,
and Staph. aureus, Gram-negative rods and anaerobes
are commonly involved.
FUNGAL INFECTIONS
 most commonly seen in patients with defective
immunity
 Aspergillus fumigatus
 Pneumocystis jiroveci (formerly P. carinii)
PARASITIC INFECTIONS
 A variety of parasites localize to the lung or involve the
lung at some stage in their development :
 Nematodes such as Ascaris and the hookworms
 Schistosome larvae
 Echinococcus granulosus
 Paragonimus westermani