- LOS ANGELES -- Streptococcus
pneumoniae, bacteria that can cause life-threatening infections in adults
and especially children, are rapidly becoming resistant to penicillin and
cephalosporins such as ceftriaxone, the most widely used antibiotics currently
available to treat bacterial infections, according to Moshe Arditi, M.D.,
author of an article in the November issue of Pediatrics and director of
Cedars-Sinai Medical Center's Division of Pediatric Infectious Diseases.
- Dr. Arditi said that while the bacteria are becoming
resistant to antibiotics at "an astonishing rate," the penicillin-resistant
strains of Streptococcus pneumoniae, or pneumococci, obtained from children
with meningitis do not appear to be more virulent, or severe, than those
that are susceptible to penicillin -- at least for now.
- The Pediatrics article describes a three-year study of
children suffering from pneumococcal meningitis. Researchers reviewed the
charts of 180 children who were admitted to eight different children's
hospitals between September 1, 1993 and August 31, 1996. Because one child
had two episodes of infection, 181 episodes were documented in the findings.
Dr. Arditi said the study looked at the clinical presentation, hospital
course and outcome, taking into consideration the antibiotic resistance
patterns of the pneumococci causing the infection. Researchers then determined
whether there was a difference in outcome if the infecting organism was
an antibiotic-resistant strain of pneumococcus.
- "If you look at each year of the three-year study
and look at the percentages, you see a dramatic increase in antibiotic
resistance between the second year, for example, and the third year,"
said Dr. Arditi. "In the second year, the penicillin non-susceptible
rate (intermediate susceptible and resistant organisms) was 13 percent.
In the third year of the study, it jumped to 27 percent. For ceftriaxone,
resistance in the first year was 1.7 percent. In the second year, it became
5 percent. In the third year, it jumped to 15 percent. In other words,
resistance to ceftriaxone tripled between the second and the third year
of the study."
- The rapid increase in resistance is also obvious when
looking at the recent history of penicillin use. For example, 27 percent
of the pneumococci were not susceptible to penicillin in the final year
of this study, 1996. That compares to 0.02 percent reported less than a
decade ago, according to Dr. Arditi.
- Many "varieties," or serological types, of
pneumococci exist. The bacteria can cause pneumonia and many other infections,
such as sinusitis and infection of the middle ear. In fact, they are the
most common cause of acute middle ear infections and invasive bacterial
infections -- including pneumonia and meningitis -- in children, according
to Dr.Arditi. They also cause more than 500,000 cases of pneumonia in adults
and children each year, and are one of the most common causes of bacterial
meningitis in young children, resulting in approximately 5,000 cases of
meningitis each year.
- This study focused specifically on children with pneumococcal
meningitis and is likely the largest study of its kind. Bacterial meningitis
-- a bacterial infection of the meninges, the membranes that envelop the
brain and spinal cord -- can cause death or permanent neurologic damage.
In fact, of the 180 children in this study, 14 died. Of those who survived,
25 percent developed neurologic problems and 32 percent suffered moderate
to severe hearing loss.
- The study of pneumococcal meningitis was part of a larger
study of pneumococcal infections among children in general. Those results
were published in the September 1998 issue of Pediatrics. The research
was conducted at eight children's hospitals in the United States and looked
at 1,291 episodes of invasive pneumococcal infection in 1,255 children.
- "In the past several years in the United States
as well as worldwide, the pneumococcal isolates that are resistant to antibiotics
have been increasing in frequency -- dramatically. Not only the frequency
is increasing but the degree of resistance also is consistently becoming
greater," according to Dr. Arditi. He said there is concern that clinical
outcomes may decline as more strains of bacteria become increasingly resistant.
- But there is hope in the near future, in the form of
new vaccines against pneumococcus, said Dr. Arditi. In fact, pneumococcal
polysaccharide vaccines -- which use a carbohydrate from the cells of the
bacteria to provide immunity -- have been developed and are in use. However,
while safe and effective for adult use, they have not worked well in protecting
young children, especially those younger than two years of age. But newer
vaccines -- multivalent pneumococcal conjugate vaccines -- combine vaccines
against several strains of pneumococcus and attach a carrier protein.
- "Infants and young children respond much better
to these vaccines because of the carrier protein attached to the polysaccharide,"
said Dr. Arditi. He said details of the latest stages of clinical trials
have started to become available and will probably be completed early in
1999. Preliminary reports indicate that the vaccines will be highly efficient
in protecting those who are most vulnerable to these infections: infants
and young children. A vaccine introduced 10 years ago had a major impact
on what was then the most common cause of bacterial meningitis, Haemophilus
influenzae type B (Hib). "Since the Hib vaccine was introduced in
1989 and led to a dramatic decline in the incidence of Haemophilus influenzae
meningitis, proportionally, Streptococcus pneumoniae has become the most
common cause of morbidity and mortality resulting from bacterial meningitis.
It also has become the most common cause of bacterial meningitis in children
1 to 23 months of age in the United States."
- "It's absolutely necessary to educate the public
and practitioners regarding this problem and the contributing factors,"
Dr. Arditi said. "I think controlling antibiotic usage in an outpatient
setting to prevent further increases in the rate of antibiotic resistance
is now a national priority."