PNEUMONIA
http://www.medicinenet.com/pneumonia/page3.htm
What are some of the organisms that cause pneumonia, and how are they treated?
Klebsiella pneumoniae and Hemophilus influenzae
Legionella pneumoniae
Mycoplasma pneumoniae
Pneumocystis carinii pneumonia
methicillin-resistant Staph aureus pneumonia
Streptococcus pneumoniae.
Viral pneumonias
The most common cause of a bacterial pneumonia is Streptococcus pneumoniae. In this form
of pneumonia, there is usually an abrupt onset of the illness with shaking chills, fever, and
production of a rust-colored sputum. The infection spreads into the blood in 20%-30% of
cases (known as sepsis), and if this occurs, 20%-30% of these patients die.
Two vaccines are available to prevent pneumococcal disease: the pneumococcal conjugate
vaccine (PCV7; Prevnar) and the pneumococcal polysaccharide vaccine (PPV23;
Pneumovax). The pneumococcal conjugate vaccine is part of the routine infant immunization
schedule in the U.S. and is recommended for all children < 2 years of age and children 2-4
years of age who have certain medical conditions. The pneumococcal polysaccharide vaccine
is recommended for adults at increased risk for developing pneumococcal pneumonia
including the elderly, people who have diabetes, chronic heart, lung, or kidney disease, those
with alcoholism, cigarette smokers, and in those people who have had their spleen removed.
This vaccination should be repeated every five to seven years, whereas the flu vaccine is
given annually.
Antibiotics often used in the treatment of this type of pneumonia include penicillin, amoxicillin
and clavulanic acid (Augmentin, Augmentin XR), and macrolide antibiotics including
erythromycin, azithromycin (Zithromax, Zmax), and clarithromycin (Biaxin). Penicillin was
formerly the antibiotic of choice in treating this infection. With the advent and widespread use
of broader-spectrum antibiotics, significant drug resistance has developed. Penicillin may still
be effective in treatment of pneumococcal pneumonia, but it should only be used after cultures
of the bacteria confirm their sensitivity to this antibiotic.
Klebsiella pneumoniae and Hemophilus influenzae are bacteria that often cause pneumonia in
people suffering from chronic obstructive pulmonary disease (COPD) or alcoholism. Useful
antibiotics in this case are the second- and third-generation cephalosporins, amoxicillin and
clavulanic acid, fluoroquinolones (levofloxacin [Levaquin], moxifloxacin-oral [Avelox], and
sulfamethoxazole/trimethoprim [Bactrim, Septra]).
Mycoplasma pneumoniae is a type of bacteria that often causes a slowly developing infection.
Symptoms include fever, chills, muscle aches, diarrhea, and rash. This bacterium is the
principal cause of many pneumonias in the summer and fall months, and the condition often
referred to as "atypical pneumonia." Macrolides (erythromycin, clarithromycin, azithromycin,
and fluoroquinolones) are antibiotics commonly prescribed to treat Mycoplasma pneumonia.
Legionnaire's disease is caused by the bacterium Legionella pneumoniae that is most often
found in contaminated water supplies and air conditioners. It is a potentially fatal infection if not
accurately diagnosed. Pneumonia is part of the overall infection, and symptoms include high
fever, a relatively slow heart rate, diarrhea, nausea, vomiting, and chest pain. Older men,
smokers, and people whose immune systems are suppressed are at higher risk of developing
Legionnaire's disease. Fluoroquinolones are the treatment of choice in this infection. This
infection is often diagnosed by a special urine test looking for specific antibodies to the
specific organism.
Mycoplasma, Legionnaire's, and another infection, Chlamydia pneumoniae, all cause a
syndrome known as "atypical pneumonia." In this syndrome, the chest X-ray shows diffuse
abnormalities, yet the patient does not appear severely ill. These infections are very difficult to
distinguish clinically and often require laboratory evidence for confirmation.
Pneumocystis carinii pneumonia is another form of pneumonia that usually involves both
lungs. It is seen in patients with a compromised immune system, either from chemotherapy for
cancer, HIV/AIDS, and those treated with TNF (tumor necrosis factor), such as for rheumatoid
arthritis. Once diagnosed, it usually responds well to sulfa-containing antibiotics. Steroids are
often additionally used in more severe cases.
Viral pneumonias do not typically respond to antibiotic treatment. These infections can be
caused by adenoviruses, rhinovirus, influenza virus (flu), respiratory syncytial virus (RSV), and
parainfluenza virus (that also causes croup). These pneumonias usually resolve over time with
the body's immune system fighting off the infection. It is important to make sure that a bacterial
pneumonia does not secondarily develop. If it does, then the bacterial pneumonia is treated
with appropriate antibiotics. In some situations, antiviral therapy is helpful in treating these
conditions.
Fungal infections that can lead to pneumonia include histoplasmosis, coccidiomycosis,
blastomycosis, aspergillosis, and cryptococcosis. These are responsible for a relatively small
percentage of pneumonias in the United States. Each fungus has specific antibiotic
treatments, among which are amphotericin B, fluconazole (Diflucan), penicillin, and
sulfonamides.
Major concerns have developed in the medical community regarding the overuse of antibiotics.
Most sore throats and upper respiratory infections are caused by viruses rather than bacteria.
Though antibiotics are ineffective against viruses, they are often prescribed. This excessive
use has resulted in a variety of bacteria that have become resistant to many antibiotics. These
resistant organisms are commonly seen in hospitals and nursing homes. In fact, physicians
must consider the location when prescribing antibiotics (community-acquired pneumonia, or
CAP, versus hospital-acquired pneumonia, or HAP).
The more virulent organisms often come from the health-care environment, either the hospital
or nursing homes. These organisms have been exposed to a variety of the strongest
antibiotics that we have available. They tend to develop resistance to some of these
antibiotics. These organisms are referred to as nosocomial bacteria and can cause what is
known as nosocomial pneumonia when the lungs become infected.
Recently, one of these resistant organisms from the hospital has become quite common in the
community. In some communities, up to 50% of Staph aureus infections are due to organisms
resistant to the antibiotic methicillin. This organism is referred to as MRSA (methicillin-resistant
Staph aureus) and requires special antibiotics when it causes infection. It can cause
pneumonia but also frequently causes skin infections. In many hospitals, patients with this
infection are placed in contact isolation. Their visitors are often asked to wear gloves, masks,
and gowns. This is done to help prevent the spread of this bacteria to other surfaces where
they can inadvertently contaminate whatever touches that surface. It is therefore very
important to wash your hands thoroughly and frequently to limit further spread of this resistant
organism. The situation with MRSA continues to evolve. The community-acquired strain of
MRSA tends to be responsive to some of the more commonly used antibiotics whereas the
hospital-acquired strains require stronger, more aggressive antibiotic therapies. As this
evolution occurs, patients are arriving in the hospital with the community-acquired strains as
well as a previous hospital-acquired strain. This further necessitates performing bacterial
cultures to determine the best course of action.