Pneumonia (cont.)
What are some of the organisms that cause pneumonia, and how are they treated?
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, 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.
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], gatifloxacin-oral
[Tequin], and sulfamethoxazole and 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.
Next: Conclusions »
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