Pneumococcal infections

[Greta]

Pneumococcal infections are caused by the gram-positive, sphere-shaped (coccal) bacteria (see figure How Bacteria Shape Up) Streptococcus pneumoniae (pneumococci). These bacteria commonly cause pneumonia, meningitis, sinusitis, and middle ear infection.

Pneumococcal bacteria are dispersed in the air when infected people cough or sneeze.
Pneumococcal infections usually cause fever and a general feeling of illness, with other symptoms depending on which part of the body is infected.
Diagnosis may be based on symptoms or identification of the bacteria in samples of infected material.
Young children are routinely vaccinated against these infections, and vaccination is recommended for all people at high risk.
Penicillin or another antibiotic is usually effective treatment.

(See also Overview of Bacteria.)
There are more than 90 types of pneumococci. However, most serious infections are caused by only a few types.
Pneumococci commonly reside in the upper respiratory tract of healthy people, their natural host, particularly during the winter and early spring. The bacteria spread to other people when they do the following:

Inhale infected droplets dispersed by sneezing or coughing
Come in close contact with an infected person

Spread is more likely among self-contained groups of people, such as people who live, stay, or work in nursing homes, prisons, military bases, shelters for the homeless, or day care centers.

[Luis Fok]

Streptococcus pneumoniae (pneumococci) are gram-positive, alpha-hemolytic, aerobic, encapsulated diplococci. In the US, pneumococcal infection annually causes about 7 million cases of otitis media, 500,000 cases of pneumonia, 50,000 cases of sepsis, 3,000 cases of meningitis, and 40,000 deaths. Diagnosis is by Gram stain and culture. Treatment depends on the resistance profile and includes either a beta-lactam, a macrolide, a respiratory fluoroquinolone, or sometimes vancomycin .
Pneumococci are fastidious microorganisms that require catalase to grow on agar plates. In the laboratory, pneumococci are identified by

Gram-positive lancet-shaped diplococci
Catalase-negative
Alpha-hemolysis on blood agar
Sensitivity to optochin
Lysis by bile salts

Pneumococci commonly colonize the human respiratory tract, particularly in winter and early spring. Spread is via airborne droplets.
True epidemics of pneumococcal infections are rare; however, some serotypes seem to be associated with outbreaks in certain (eg, military, institutional) populations.