Haemophilus
Disease: 
The non-encapsulated strain of H. influenzae is present in the nasopharynx of approximately 75 percent of healthy children and adults. Disease is usually caused by encapsulated strains that get into the upper respiratory tract. This may be followed by ear or sinus infections, leading to pneumonia. Encapsulated organisms can resist phagocytosis by white blood cells, and spread through out the respiratory system. Symptoms are similar to streptococcal pneumonia: shaking chills, high fever; cough with pink productive sputum and chest pain.
Diagnosis:
A gram smear of sputum and clinical symptoms are typically sufficient to diagnose Haemophilus infection. Cells may then be cultured on chocolate agar (they do not grow on blood agar).
Characteristics:
H. influenzae are small, non-motile, Gram (-) coccobacilli, 0.5 um x 1.0 um in size. Non-encapsulated organisms from sputum are pleomorphic and often exhibit long threads and filaments. The organism may appear Gram-positive unless the Gram stain procedure is very carefully carried out. (Arrow shows bacterial cells)
Related bacteria:
Taxonomically, Haemophilus influenzae is Gamma Proteobacterial lineage, in the family Pasteurellaceae, which includes Pasteurella and Actinobacillus, two other genera of bacteria that are parasites of animals.
Legionella
Disease:
Legionella pneumophilia causes Legionnaires' disease, a severe infection which causes pneumonia. The name comes from the first recognized outbreak of the disease, which was transmitted through the air conditioning unit at an American Legion convention. Legionella is commonly found in water systems and is spread through aerosols, rather than host-to-host contact. Elderly people, or those with compromised immune systems, are most affected. Patients with Legionnaires' disease have fever, chills, and a severe cough. Patients may also have muscle aches, headache, tiredness, loss of appetite, and, occasionally, diarrhea.
Diagnosis:
While chest X-rays often show pneumonia, it is difficult to distinguish Legionnaires' disease from other types of pneumonia by symptoms alone. The most useful diagnostic tests detect the bacteria in sputum, find Legionella antigens in urine samples, or compare antibody levels to Legionella in two blood samples obtained 3 to 6 weeks apart.
Characteristics:
Legionella pneumophilia is a thin, pleomorphic rod that stains weakly Gram (-). In vitro it appears as a short rod, 0.5 um wide by 2-3 um long; in culture it can grow as long filamentous rods up to 10 um long. It has polar flagella and does not form spores. (Arrow shows bacterial cells)
Related bacteria:
Taxonomically, Legionella is in the Gamma group of the Proteobacterial lineage, in the family Legionellales. Strains are classified by different surface antigens and DNA homology.
Moraxella
 Disease:
Taxonomically, Moraxella catarrhalis is a member of the Gamma Proteobacterial lineage, in the family Moraxellaceae. Moxarella catarrhalis infections typically cause Otitis media (middle ear infection) in children and can lead to pneumonia or other respiratory track infections. M. catarrhalis’ produces an endotoxin (the lipopolysaccharide layer, located on the outer membrane of the cell envelope). This endotoxin is similar to Neisseria, which is one of many organisms that can cause bacterial meningitis
Diagnosis:
A Gram smear of sputum and the oxidase test are both used in identifying M. catarrhalis. M. catarrhalis is oxidase positive, indicating that it uses cytochrome c as an electron acceptor. It can be readily grown on either chocolate or blood agar.
Characteristics:
M. catarrhalis is a Gram (-), coccus shaped bacteria (sometimes appears as dipplococci)
Pseudomonas
Disease:
Pseudomonas aeruginosa is an opportunistic pathogen of humans. Pseudomonal pneumonia usually occurs in patients with other complicating factors, and can be quite severe. It is a common cause of fatal pneumonia in cystic fibrosis patients. Once attached to surface cells, Pseudomonas creates a biofilms in the tissue, which make phagocytosis difficult and which makes the infection difficult to treat with antibiotics. Symptoms include: malaise, fever, with “bed-shaking” chills.
Diagnosis:
Pseudomonas is generally diagnosed by culturing bacteria from a deep lung sputum sample, and by microscopic identification for Gram (-) rods.
Characteristics: Taxonomically, Pseudomonas are found in the Alpha and Beta group of Proteobacteria. These Gram (-), rods are generally 1um x 3 um. They have peritrichous flagella and are highly motile. The do not form spores.
Related bacteria:
Pseudomonas are related to other Gram (-), respiratory rods in the Gamma Proteobacterial lineage. They are an extremely diverse group of bacteria, found in many different branches of this group.
 Staphylococcus
Disease:
While Staphylococcus aureus infection is one of the most common causes of skin infections, it can also cause pneumonia, usually as a secondary infection or in patients with compromised immune systems (such as elderly, diabetics or alcoholic). If untreated, abscesses can develop in lung tissue. Symptoms of staphylococcal abscesses include: persistent fever, cough with productive, bloody, foul-smelling sputum.
Diagnosis:
It is difficult to diagnose Staphylococcus pneumonia because many people carry Staphylococcus in their normal nasal-pharynx flora. If appropriate samples are taken, bacteria can be cultured from the blood or sputum, and Gram stains of sputum show Gram(+) cocci in clusters.
Characteristics:
Staphylococcus are Gram(+) spherical bacteria that are about 1 um in diameter, and grow in grape-like clusters. Staphylococcus can grow at a temperature range of 15 to 45 degrees and at NaCl concentrations as high as 15 percent. (Arrow shows bacterial cells)
Related bacteria:
Taxonomically, Staphylococcus is in the in the low G+C Gram (+) lineage. On the basis of 16s RNA analysis, the genus Staphylococcus belongs to the broad Bacillus-Lactobacillus-Streptococcus cluster. However, these respiratory bacteria are not closely related to other genera in the family.
Streptococcus
Disease:
Streptococcus pneumoniae
is the most frequent cause of bacterial pneumonia in humans, causing shaking chills, high fever; cough with
pink productive sputum and chest pain. Streptococcus
is spread through host-to-host contact, via inhalation of infectious
droplets or hand-to-mouth contact. Streptococcus colonizes
the naso-pharynx area (causing strep throat) and from there, can
move into the ears (causing otitis media) or into the lungs (pneumonia). Virulent Streptococcus pneumoniae
have a capsule, which makes phagocytosis by white blood cells difficult.
Thus, encapsulated strains are able to invade the lung and cause
disease.
Diagnosis:
Streptococcus is commonly identified through standard culture techniques or Gram stains of sputum. Various commercial serological tests are also available. When plated on blood agar, S. pnuemoniae demonstrates alpha-hemolysis (partial breakdown of red blood cells).
Characteristics:
Streptococcus
are spherical Gram (+) cells that grow in long chains. Cells are
approximately 0.5–1.0 um in diameter. These non-motile cells
do not form spores. Some strains of Streptococcus pneumoniae
have capsules. (Arrow shows bacterial cells)
Related bacteria:
Taxonomically, Streptococcus is
in the low G+C Gram (+) lineage. These strictly fermentative bacteria
are part of the lactic acid bacteria group. Strains are differentiated
by specific carbohydrate antigens.
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