Atypical pneumonia Flashcards
What are the causative microbes of Atypical pneumonia?
- Pneumocystis jirovecii
- Chlamydia pneumoniae
- Chlamydia psittaci
- Legionella pneumophila
- Mycoplasma pneumoniae
Lung abscess
What is ATYPICAL pneumonia?
A clinically ‘atypical’ form of pneumonia, which lacks the classic signs and symptoms of pneumonia
It lacks symptoms like e.g lobar consolidation, bronchial breathing.
It causes an interstitial picture on chest x-ray
Atypical pneumonia is pneumonia not caused by one of the more traditional pathogens.
Discuss Typical Pneumonia
Typical pneumonia caused by eg Streptococcus pneumoniae
Cannot use a b-lactam antibiotic to treat it as the organisms are resistant, therefore use azithrothromycin or quinolone eg ciprofloxacin.
Why won’t routine cultures isolate the microbes that cause atypical pneumonia?
Microbes causing atypical pneumoniae are not easily cultured and therefore routine cultures will not isolate them.
What are the most common causative organisms of bacteria? (often intracellular living)
- Chlamydophilia pneumoniae
- Causes a mild form of pneumonia with relatively mild symptoms. - Chlamydophila psittaci
- Causes psittacosis. - Legionella pneumophila ( gram negative bacilli )
- Causes a severe form of pneumonia with a relatively high mortality rate, known as legionellosis or Legionnaires’ disease. - Mycoplasma pneumoniae
- Usually occurs in younger age groups and may be associated with neurological and systemic (e.g. rashes) symptoms.
- No cell wall
What is the Chlamydophila pneumoniae?
Obligate intracelluar bacteria
Has a cell wall that does not have peptidoglycan
Bacteria can’t produce its own ATP(adenosine triphosphate), it is an energy parasite
What is Chlamydophila psittaci?
Strains of C. psittaci that are most virulent for humans tend to be those associated with psittacine birds
psittacine from the Latin Psittacus, or parrot e.g parrots, parakeets, macaws, cockatoos
Humans who develop psittacosis are commonly:
- bird fanciers
- work in poultry farms
- Abattoirs that process birds
- pet shops, or veterinarians’ offices.
The organism is usually acquired by inhalation
Humans who develop psittacosis are commonly involved in what?
Humans who develop psittacosis are commonly:
- bird fanciers
- work in poultry farms
- Abattoirs that process birds
- pet shops, or veterinarians’ offices
What is legionellae?
Legionella pneumophila is the species that causes 90 % of infections compared to other legionella species.
Gram negative bacillus
Requires special media to grow, will not grow on standard blood plate as it requires cysteine
**Transmitted by infected aerosols
What are the environmental sources of Legionella?
- Warm water
- Saunas
- Water cooling towers
- Geyers
- Reservoirs
- Usually found in water
What is Mycoplasma pneumoniae?
- Smallest free-living bacteria
- Has a cell membrane containing sterols but no cell wall
- Lack of cell wall means that it is resistant to beta –Lactams eg penicillin, cephalosporin antibiotics
- Causes mild disease – “walking pneumonia”
- Laboratory diagnosis – serology – done on serum looking at a fourfold increase in titre
- Organism is difficult to stain or culture
What is pneumocystis jiroveci pneumonia (PCP)?
Pneumocystis is a fungal organism that causes pneumonia predominantly in immunocompromised patients. Eg HIV positive patients
Prior to its discovery as a human-specific pathogen, P. jirovecii was known as P. carinii. (PCP)
What is the Epidemiology of pneumocystis jiroveci pneumonia?
-Common in immunocompromised patients esp HIV positive patients ( with AIDS CD4+ <200 cells/μL)
-Also solid organ transplant patients
• Transmission – airborne droplet
What is the Microbiology of pneumocystis jiroveci pneumonia?
> Classified as a fungus because RNA is homologous to fungal RNA
> Pneumocystis carinii was classified as a protozoan until late 1980s. The reasons that led to this classification were its morphologic features that were similar to those of protozoa, the lack of ergosterol in its cell membrane and the inability to grow this microorganism on routine laboratory media.
> Four morphological forms – trophozoites, cysts, precysts, sporozoites
> Cyst is diagnostic form and stains with Giemsa and methenamine silver stains
Formerly known as Pneumocystis carinii.
What are the four morphological forms of Pneumocystis jiroveci?
Four morphological forms – trophozoites, cysts, precysts, sporozoites
What is Pneumocystis jiroveci formerly known as?
Formerly known as Pneumocystis carinii.
Why was Pneumocystis carinii classified as a protozoa?
Pneumocystis carinii was classified as a protozoan until late 1980s. The reasons that led to this classification were its morphologic features that were similar to those of protozoa, the lack of ergosterol in its cell membrane and the inability to grow this microorganism on routine laboratory media.
What is the Pathophysiology of pneumocystis jiroveci?
Infection in the lung starts with the multiplication of the organism in the alveoli.
As infection progresses, alveoli fill with exudates and inflammatory cells
Desquamation of the alveolar lining cells creates increased permeability of the alveolar capillary membrane and pulmonary oedema.
The inflammatory exudate interferes with gas exchange through the alveolus in the lung
What is the clinical presentation of Pneumocystis jiroveci?
- Subacute to acute onset pneumonia
- Dyspnea, tachypnea, cyanosis, nonproductive cough, fever
- Hypoxemia
How do we diagnose (or come to a diagnosis) pneumocystis jiroveci pneumonia?
Laboratory Testing is carried out.
- Fluorescent antibody staining using monoclonal antibodies on induced sputum or bronchoalveolar lavage
Cyst is diagnostic form and also stains with Giemsa and methenamine silver stains
- PCR ( polymerase chain reaction )– more sensitive than fluorescent antibody staining may be particularly useful on the non-HIV infected immunocompromised host, ( most sensitive test )
( Not available in KZN )
What is the prevention and treatment of pneumocystis jiroveci pneumonia?
- Prevention
Prophylactic use of oral Tri-metho-prim-Sulfa-methox-azole - Treatment
Tri-metho-prim-Sulfa-methox-azole
What is a lung abscess?
Lung abscess is necrosis of the pulmonary tissue and formation of cavities containing necrotic debris or fluid caused by microbial infection.
This pus-filled cavity is often caused by aspiration, which may occur during altered consciousness.
During aspiration, bacteria ( usually from mouth) passes past the vocal cords and enters in to the lung causing infection
Alcoholism is the most common condition predisposing to aspiration and lung abscesses.
Problems with swallowing in patients with stroke also predispose to aspiration
How does the bacteria get into the lung?
During aspiration, bacteria ( usually from mouth) passes past the vocal cords and enters in to the lung causing infection
Alcoholism is the most common condition predisposing to aspiration and lung abscesses.
What is the most common condition predisposing to aspiration and lung abscesses?
Alcoholism
