Pneumonia

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Pneumonia

Dr. Raafat Abd-Rabow

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Primary bronchus Secon bronchus Tertia Alveoli enlarged Termin al Chi

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Pneumonia is inflamed or swollen lung tissue due to infection with a germ

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Symptoms & signs: fever, malaise, cough, dyspnea and grunting……Tachypnea, retractions & X-ray chest abnormalities.

Normal X- ray chest

Pneumonia

abstract

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Pneumonia may be

1- Community-acquired pneumonia (CAP): pneumonia in a previously healthy person who acquired the infection outside a hospital (or a longterm care facility). 2- Hospital-acquired pneumonia (HAP): patients live in long-term care facilities or have recently visited a hospital.

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Community-acquired pneumonia

Disease may be “typical” or “atypical.” “Typical” pneumonia: is characterized by shaking chills, purulent sputum, and x-ray abnormalities that are proportional to the physical signs. “Atypical” pneumonia is characterized by insidious onset, scant sputum and x-ray abnormalities greater than predicted by physical signs.

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"Typical" versus "Atypical" pneumonia Typical Pneumonia: (virulent bacteria) • Sudden onset. • Productive cough with purulent sputum. • Pleuritic chest pain. • leukocytosis (high no. of WBC) or leukopenia (low no. of WBC). Atypical Pneumonia: (viral, M. pneumoniae, others) • Gradual onset. • Nonproductive cough. • Substernal chest pain. • White blood count normal.

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Typical vs. Atypical Pneumonia Historical Classification Typical Pneumonia S pneumoniae. H innuenzae, Detectable on gram stain. grows on standard media Abrupt onset Fever. pleuritic chest pain. cough producbve Of purulent. sometimes blocd•tinged sputum Often lobar inntrate • Elevated Count Atypical Pneumonia Chlamydia. viral Not detectable on gram stain or cultivatable on standard bacteriomc media May begin as mild URI followed later by ryostly dry cough and dyspnea Infiltrates to patchy than bhar exception) Categ«ies to presentation but is rot

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Strept pneumoniae Morphology: Gram positive cocci Ovoid or lancet shape, arranged in pairs ( diplococci ), Capsulated.

GP diplococci, S. pneumoniae

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Cultural characters: They grow on blood agar producing α - haemolysis or greenish discolouration similar to viridans streptococci from which they are differentiated by the following tests:

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Pneumocoeci Viridaris Streptococci Solubility in bile Soluble Not soluble Fermentation of inulin Fermented Not fermented Sensitivity to optochin Sensitive Not sensitive Pathogenicity to mice Pathogenic Not pathogenic Quellung test Positive Negative

Streptococcus mitis not lysed by bile Negative Streptococcus pneumoniae lysed by bile Positive Bile solubilitytest

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Quellung test

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Antigenic structure and virulence factors: 1-Capsule: There are at least 91 serotypes of pneumococci based on the chemical specificity of the capsular polysaccharide. Types 1-8 are responsible for 75% of cases of pneumococcal pneumonia in adults and for more than half of the fatalities in pneumococcal bacteraemia in children. 2- IgA1 Protease. 3- Peptidoglycan and teichoic acid. 4- Autolysin, pneumolysin and pilli .

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Diseases caused by pneumococci. It is exclusively a human pathogen that spreads by droplet. Pneumococci cause pneumonia, meningitis, otitis media, sinusitis, conjunctivitis, endocarditis and other pyogenic infections.

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Diagnosis of pneumonia: 1-Film : Direct microscopic examination of gram stained sputum smears will show the prevalent organism to be pneumococci among pus cells. 2-Culture : Sputum is cultured on blood agar in 5-10% . Alpha haemolytic colonies should be differentiated from viridans streptococci by (see table)

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3-Quellung reaction: Fresh emulsified sputum (or CSF deposit in meningitis) mixed with polyvalent anti-pneumococcal serum and methylene blue and examined under the microscope, reveals swollen capsules i.e. a positive ‘ quellung reaction”. This can be done for rapid identification. 4-Intraperitoneal injection of sputum into mice. Animals die in 24-48 hrs. the organism can be seen in tissue smears, and pure culture can be obtained from heart blood . 5-Blood cultures are positive in 15-25% of pneumococcal infections.

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Treatment: Most pneumococci are sensitive to penicillin . Erythromycin or azithromycin are used for penicillin allergic patients. Ceftriaxone and Vancomycin is used for treatment of penicillin resistant pneumococci.

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Prophylaxis: 1-A polyvalent (23 types) Polysaccharide vaccine (PPV-23). It is safe, fairly effective and provides long lasting (at least 5 years) protection. It is recommended for susceptible immunosuppressed individuals e.g. the elderly, debilitated, asplenic patients, HIV patients or those under immunosuppressive therapy. 2-A pneumococcal conjugate vaccine(PCV 13). containing the capsular Polysaccharide of the 13 most common pneumococcal serotypes coupled to a carrier protein. This vaccine is recommended for all children at 2, 4 and 6 months and at 12-15 months.

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Atypical pneumonia

With atypical pneumonia → the infection is caused by different bacteria other than the more common ones that cause pneumonia. This causative agent cannot be isolated on ordinary laboratory media and cannot stained by Gram stain. Also the clinical picture of atypical pneumonia does not resemble that of typical pneumonia.

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C∕P

It presents with → History of upper respiratory tract infection. Gradual onset. Dry cough with scanty sputum. Low grade fever. Sub sternal chest pain. Extra pulmonary manifestations. White blood count normal.

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Causes of atypical pneumonia

1- Mycoplasma pneumoniae 2- Legionella pneumophilia 3- C. pneumoniae 4- C. psittaci 5- Coxiella burnetii 6- Viral pneumonia 7- Fungal pneumonia

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Three specific infectious bacteria cause the majority of atypical pneumonia cases: Mycoplasma pneumoniae usually infects people under 40 with mild pneumonia symptoms. It commonly causes earaches, headaches, and a sore throat, as well. Chlamydophila pneumoniae is common in school-aged children and young adults. Legionella pneumophila is more severe, generally, and seen most often in older adults, people who smoke, and those with weakened immune systems. It is also called Legionnaires' disease.

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Im portant human pathogens are

1- M.pneumoniae causes atypical pneumonia. 2- Ureaplasima urealyticum is urease positive. It causes 20% of non- gonococcal urethritis and neonatal sepsis in premature infants. 3- M hominis is associated with postpartum fever and pelvic inflammatory disease e.g. salpingitis . 4- M. genitalium is associated with non- gonococcal urethritis. - All may be the cause of septic arthritis in immunocompromised persons

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Morphology and cultural characters of M. pneumoniae

Mycoplasma are the smallest free living organisms. They lack cell wall → وعشان كده they are pleomorphic , stain poorly with gram but can be stained by Geimsa stain. They are the only bacteria that contain cholesterol in their cell membrane. They require special enriched media for growth

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Disease

atypical pneumonia

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Diagnosis of atypical pneumonia

1- Direct detection in sputum or nasopharyngeal aspirates of: a-Antigens by immunofluoiescence using specific antisera. b-Specific nucleotide sequence using DNA probes orPCR .

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2- Serology is most useful in diagnosis : a-Detection of M. pneurnoniae IgM ( rising titre of IgG by ELISA or complement fixation. b-Detection of cold agglutinin at a titre of 1∕128 or higher indicates recent infection. These are autoantibodies against type O red cells that agglutinate these cells at 4°C but not at 37°C. It is positive in 50% of cases. It is non-specific and may be positive in other diseases including viral infections, malaria and acquired haemolytic anaemia . 3- Isolation from sputum is difficult and time consuming

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Treatment

They are treated by tetracyclines , erythromycin or azithromycin

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LEGIONELLA

There are about 40 species of Legionella found in soil and water. L. pneumophila is the major cause of disease in man. It causes outbreaks of Atypical pneumonia “ Legionnaire’s disease ”. It also causes Pontiac fever characterized by fever, malaise, headache, muscle pains and cough (flulike condition)

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Morphology and cultural characters

Motile weakly gram negative rods. They are fastidious and require for growth media containing L-cysteine, iron, and α - ketoglutarate as in buffered charcoal yeast extract (BCYE) agar. They are catalase and oxidase positive

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Pathogenesis

Infection occurs by inhalation of water aerosols contaminated by these organisms. It can be community-acquired or nosocomial. Risk groups include alcoholics, diabetics, AIDS, cancer and transplant patients

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L. pneumophila can survive intracellularly in alveolar macrophages, as they inhibit phagosomal lysosomal granules fusion. They produce proteases that cause patchy infiltrations in the lungs. Bacteraemia may occur in severe cases. accompanied by damage to the vascular endothelium in organs like the brain and kidney. Cell mediated immunity is the most important defense mechanism, because of the intracellular growth of the organism

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Treatment

Erythromycin alone or in combination with rifampicin is the treatment of choice

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Chlamydia

Characters: - Similar to bacteria in: 1. cell wall→ typical of Gram-negative bacteria. 2. cytoplasm →both RNA , DNA , ribosome 3. Multiplication→by simple binary fission. 4.Morphology→pleomorphic coccobacilli 5. treated by antibiotics - Similar to viruses in: 1. Obligate intracellular (cannot cultivated on inanimate media as it is unable to synthetize ATP) 2. Culture→ cell culture, embryonated eggs, susceptible animals.

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3 species: 1- C. trachomatis 2- C. psittaci & 3- C pneumoniae

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Developmental cycle of chlamydia 2 forms : 1. Elementary body (EB): infectious non replicating form, 0.25 - 0.3 μm in diameter released from ruptured infected cells and can be transmitted from one individual to another. 2. Reticulate body (RB): intracytoplasmic replicating form, 0.5 - 0.6 μm in diameter. EB enters the cell by endocytosis and develops into RB within a cytoplasmic vacuole with no cell wall & divides by binary fission to form particles which after synthesis of the outer cell wall, develop into new infectious EB & released from the cell to infect other cells.

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Chlamydiae that infect humans are divided into three species

1-Chlamydia trachomatis → causes ocular. genital and respiratory infections. 2-Chlamydia psittaci → causes psittacosis in birds that may be transmitted to man. 3-Chlamydia pneumoniae → causes atypical pneumonia

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Diagnosis

1- Sample → sputum 2. Direct smear → Inclusion bodies in scraped tissue cells detected by staining with Giemsa or with fluorescent monoclonal antibodies 3. Culture: on - McCoy cells. - yolk sac of embryonated egg: 4. Serological tests: - Antigen detection → directly in specimens by using specific immunofluorescent antibodies - Antibodies detection →in sera from infected humans by the complement fixation or immunofluorescence tests. 5. Molecular techniques DNA probes & PCR.

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Treatment → Tetracycline & erythromycin & Penicillin is not effective. Control No vaccine

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COXIELLA and Q FEVER

Q fever – caused by Coxiella burnetii . The infection is acquired by inhalation of infectious material. After an incubation of 14-26 days there is a sudden onset of fever, chills, and headache, but no rash. The disease is characteristically an atypical pneumonia lasting 5-14 days with a low mortality rate. Hepatitis is frequent enough that the combination of pneumonia and hepatitis should suggest Q fever. Treatment: Doxycycline with ciprofloxacin or rifampicin. Prevention: A formalin-killed whole cell vaccine is available for those occupationally at risk. Proper pasteurization of milk