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Microbiology (BIO 51): Pneumonia

The topic of Pneumonia, taught by Dr. Lopez at Kingsborough Community College. Microbiology, BIO 51, Kingsborough Community College, Summer 2011.
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Pneumonococcal pneumonia (A.K.A-Streptococcus pneumoniae)
This type of pneumonia is the most common identifiable cause of bacteria pneumonia and accounts for 2/3 of bacteremic community-acquired pneumonias.
S. pneumoniae Occurrence
This pneumonia generally occurs sporadically but most frequently in winter. It occurs most commonly in persons at age extremes. There are more than 80 different serotypes.
S. pneumoniae Pathogenesis
This pneumonia usually reach the lungs by inhalation or aspiration. They lodge in bronchioles, proliferate, and initiate an inflammatory process that begins in the alveolar spaces with an outpouring of protein-rich fluid. This fluid acts as a culture medium for the bacteria and helps them spread to neighboring alveoli, typically resulting in lobar pneumonia. (consolidation)
Four Stages of Lobar Pneumonia
These are:
1. Congestion
2. Red hepatization
3. Gray hepatization
4. Resolution
Congestion
This is the earliest stage of lobar pneumonia and is characterized by extensive serous exudation, vascular engorgement and bacterial proliferation.
Red hepatization
This reflects the liver-like appearance of the consolidated lung. Airspaces are filled with polymorphonuclear cells (neutrophils), vascular congestion occurs, and extravasation of RBCs causes a reddish discoloration on gross examination.
Gray hepatization
This is is characterized by an accumulation of fibrin and inflammation. WBCs and RBCs are seen at various stages of disintegration. The alveolar spaces are packed with inflammatory exudate.
Resolution
This is characterized by resorption of the exudate.
Pneumonococcal pneumonia SNS
This is often preceded by an upper respiratory infection. The onset is often sudden, with an episode of chills. The chill is ordinarily followed by fever, pain with breathing on the effected side (pleurisy), cough, dyspnea, and sputum production. The temperature rises rapidly (100.4 F - 105 F).
- The respiration rate rises to 20-45 breaths per minute. The cough may be dry initially but usually becomes productive with purulent, blood-streaked or RUSTY SPUTUM. (<---KEY TO DIFFERENTIATE)
Pneumonococcal pneumonia Diagnosis
This pneumonia should be suspected in anyone with an acute febrile illness associated with chest pain, dyspnea, and cough. A definitive diagnosis requires the demonstration of S. pneumoniae in pleural fluid, blood, lung tissue, or transtracheal aspirate. At least half of sputum cultures are falsely negatively.
Pneumonococcal pneumonia Blood Tests
This usually show leukocytosis. Positive blood cultures are definitive evidence of this infection.
Pneumonococcal pneumonia Gram Stain
This performed on the sputum typically shows gram-positive lancet-shape diplococci.
Pneumonococcal pneumonia Chest X-Ray
This shows a pulmonary infiltrate; although findings may be minimal. Dense consolidation to a single lobe (lobar pneumonia) is quite specific for this type of pneumonia.
Pneumonococcal pneumonia Prognosis
The overall mortality rate is about 10%. Factors which herald a poor prognosis include the following:
1. Age extremes: less than one year; greater than 60 years.
2. Positive blood cultures
3. Involvement of more than one lobe
4. A peripheral WBC count less than 500/uL
5. Immunosupression
6. Development of extrapulmonary complication (meningitis or endocarditis).
Pneumonococcal pneumonia Prophylaxis
Vaccine containing 23 specific polysaccharide antigens is available
Pneumonococcal pneumonia Treatment
Penicillin G or V 250 to 500mg po q 6 h is the preferred treatment for patients not severely ill.
Vancomycin has been preferred for severely ill patients.
Staphylococcal pneumonia
This pneumonia accounts for about 2% of community-acquired pneumonias and 10 to 15% of nosocomial pneumonia.
Staphylococcal pneumonia Risks
Persons at particular risk include infants and the elderly; hospitalized and debilitated patients, especially those with tracheostomy, endotracheal intubation, immunosupression, or recent surgery.
Staphylococcal pneumonia SNS
These SNS generally parallel those of pneumococcal pneumonia.
Staphylococcal pneumonia Prognosis
This mortality rate is generally 30 to 40 % in part due to the serious associated conditions the patients have. However, fulminant courses with lethal outcomes have occasionally occur in previously healthy adults.
Staphylococcal pneumonia Treatment
Recommended therapy is penicillinase-resistant penicillin.
- The major alternative is a cephalosporin, preferably cephalothin or cefamandole.
- Vancomycin is preferred when methicillin resistance is suspected.
Klebsiella pneumoniae
This is the most significant pathogen that is a Gram negative bacilli. This causes Friedlander's pneumonia.
Additional usual Gram negative pneumonia Pathogens:
1.) Pseudomonas aeruginosa
2.) Escherichia coli
3.) Enterobacter sp
4.) Proteus sp
5.) Serratia marcescens
6.) Acinetobacter sp
Gram negative bacillary Pneumonias common hosts
These are rare in healthy hosts and usually occur in infants, the elderly, ALCOHOLICS, and debilitated or immunocompromised hosts.
Friedlanders pneumonia Pathogenesis
This frequently affects the upper lobes and produces sputum that looks like CURRANT JELLY, tissue necrosis with early abscess formation, and a fulminant course.
Gram negative pneumonia Diagnosis
These should be suspected in a patient with pneumonia with risks factors discussed. Positive cultures from blood, pleural fluid, or a transtracheal aspirate obtained before treatment are considered diagnostic.
Gram negative pneumonia Prognosis & Treatment
The mortality of this pneumonia is about 25 to 50% despite the availability of effective antibiotics. The most preferred drug regimen includes a cephalosporin. (cefotaxime)
Haemophilus Influenzae
This is a relatively common cause of bacterial pneumonia, second only to Streptococcus pneumoniae.
Type B (Hib)
Strains containing this polysaccharide capsule are the mos virulent and most likely to cause serious disease, including meningitis, and epiglottitis. These infections have nearly disappeared in the United States because of the use of a vaccine for this.
H. influenzae (noncapsulated)
Strains of H. influenzae that commonly colonize the upper airways of adults are usually this type. These strains may colonize the lower respiratory tract of patients with chronic bronchitis and are often implicated in exacerbation of chronic bronchitis.
Hib SNS
This usually occurs in children (average age one year).
- Coryza preceded most cases, and early pleural effusions occur in about 50%.
- Gram stain of expectorated sputum shows numerous, small, gram-negative coccobacilli.
Hib type B Prophylaxis
The vaccine for this is advocated for all children to be given in three doses at 2, 4, and 6 months of age.
H. Influenzae Treatment
The preferred treatment is trimethoprim-sulfamethoxazole (TMX-SMX).
Legionella pneumophilia discovery
The discovery of this came from an Investigation of an outbreak of acute febrile respiratory illness among members of the American Legion in Philadelphia in 1976. This strain is the most common agent.
L. pneumophilia Spectrum of Disease
This includes:
1. A self-limited, flu-like illness without pneumonia sometimes called Pontiac fever.
2. Legionaires disease, the most serious form, characterized by pneumonia.
3. Rare localized soft tissue infections
L. pneumophilia
Predominately in the summer months, this is found especially in hospitals and hotels, or in certain geographic areas when a water supply becomes contaminated and aerosolized organisms are spread from evaporative condensers of air conditioner systems or contaminated shower heads.
Legionaires Disease Age Occurrence
This may occur at any age, but most patients are middle-aged men. (40 Year old, smoker, drinker). Identified risk factors include smoking, alcohol abuse, and immunosupression, especially from corticosteroids.
L. pneumophilia SNS
For this, the usual incubation period is 2 to 10 days. Most patients have a prodromal phase, which may resemble influenza, malaise, fever, headache, and myalgias; they develop cough that is initially nonproductive and subsequently productive of mucoid sputum. A characteristic is high fever, sometimes with relative bradycardia, and DIAREHHA is common.
L. pneumophilia: Chest X-Rays
Chest X-rays early in the course generally shows a unilateral patchy segmental or lobar alveolar infiltrate. As the disease progresses many patients develop bilateral involvement.
L. pneumophilia: Prognosis & Treatment
Even with appropriate treatment, mortality is about 15% or greater in community acquired cases and is higher among immunosuppressed or hospitalized patients.
- Erythromycin is usually the drug of choice. Others prefer ciprofloxacin or azithromycin. Treatment should be continued for at least 3 weeks to prevent relapses.
Mycoplasma pneumoniae
A.K.A, Walking pneumonia. This is a common pathogen of lung infection in persons 5 to 35 years of age. This agent may be responsible for epidemics that spread slowly because it has an incubation period of 10-14 days. Spread may involve close contacts or closed populations in schools, the military, and families. Another name is Primary atypical pneumonia.
Mycoplasma pneumoniae: SNS
This disease processes gradually. Initial symptoms resemble influenza, with malaise, sore throat, and dry cough, which increase in severity as the disease progresses. Acute symptoms usually persist for 1 to 2 weeks followed by gradual recovery. The disease is generally mild, and spontaneous recovery is the rule. However, some patients have severe pneumonia, sometimes causing adult respiratory distress.
Mycoplasma pneumoniae Findings
In this pneumonia, findings during physical examination tend to be unimpressive in contrast with the patients' complaints and x-ray changes.
Mycoplasma pneumoniae Prognosis & Treatment
In this, nearly all patients recover with or without treatment. Because mycoplasmas do not have a cell wall, they do not respond to antibiotics that interfere with cell wall structure.
- The preferred drugs are tetracycline or erythromycin for adults or erythromycin for children.
- Antibiotic treatment reduces the period of fever and pulmonary infiltrates and hastens recovery.
Psittacosis
This is is an infectious atypical pneumonia caused by Chlamydia psittaci and transmitted to humans by certain birds. In humans, psittacosis (ornithosis, parrot fever) is usually caused by inhaling dust from feathers or excreta of infected birds or by being bitten by an infected bird.
Psittacosis SNS
After a 1 to 3 week incubation period, onset may be insidious or abrupt, with fever, chills, malaise, and anorexia. The temperature rises gradually rises, and cough develops, initially dry but at times mucopurulent.
- During the second week, pneumonia and frank consolidation may occur with secondary purulent lung infection. The temperature remains elevated for 2 to 3 weeks then falls slowly. The course may be mild or severe, depending on the patient's age and the extent of pneumonia.
Psittacosis Mortality Rate
This mortality may reach 30% in severe untreated cases.
Psittacosis Diagnosis
This is suggested by a history of exposure to birds and is confirmed by recovery of the agent or by serology.
Psittacosis Prophylaxis & Treatment
Infected pigeons in breeders' lofts, other sick birds, and dust from feathers and cage contents must be avoided
- Because other persons may become infected by inhaling cough droplets and sputum, strict patient isolation should be instituted when the diagnosis is suspected on clinical and epidemiologic grounds.
- Tetracycline
Pneumocystis carinii
This is considered a fungus and causes disease only when defenses are compromised, most commonly when there are defects in cell-mediated immunity. (AIDS, Hematologic maalignancies, Cancer chemotherapy)
Pneumocystis carinii HIV Risk
Patients with HIV infection become vulnerable to this pneumonia when their CD4 cell count is less than 200/u/L.
Pneumocystis carinii SNS
Most patients have fever, dyspnea, and a dry, nonproductive cough.
Pneumocystis carinii Diagnosis
The chest x-ray characteristically shows diffuse bilateral perihilar infiltrates, but 20 to 30% of patients have normal X-rays.
- Arterial blood gases show hypoxemia and pulmonary function test show altered diffusing capacity.
Pneumocystis carinii
The drug of choice for this pneumoina is trimethoprim-sulfamethoxazole (TMP-SMX). If this treatment is not tolerated, (sensitive to sulfur drugs) dapsone or aerosolized pentamidine can be used.