October 2000
NEW ORLEANS - New vaccines and antibiotics are increasingly affecting treatment strategies for bacterial meningitis in children, according to an interactive session during the 38th Annual Meeting of the Infectious Diseases Society of America held here.
George H. McCracken Jr., MD, and Richard F. Jacobs, MD, led the session, which reviewed various patient cases and discussed their management in today's clinical environment.
The first case involved an irritable 5-month-old from Dallas who was evaluated for fever, lethargy and poor feeding in August. Cerebrospinal fluid (CSF) testing revealed a white blood cell (WBC) count of almost 900 cells/mm3 (88% polymorphonuclear leukocytes), glucose of 36 mg/dL and protein of 96 mg/dL. "The stain smear is negative and the patient is up-to-date on his immunizations, including Prevnar [pneumococcal vaccine, Wyeth Lederle Vaccines]," said McCracken, professor of pediatrics at the University of Texas Southwestern Medical Center in Dallas.
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The three likely diagnostic choices are amebic meningitis, bacterial meningitis and aseptic meningitis.
"Statistically, the most likely diagnosis is aseptic meningitis," McCracken said. "In Dallas in August, there are from 30 to 50 cases of aseptic meningitis for each case of bacterial meningitis."
Amebic meningitis is also a possibility. "Particularly in the Southwest, where it is hot and dry during the summer. When the water becomes warm, amebic meningitis can result from children diving in lakes, etc.," he said.
Assuming the diagnosis is aseptic meningitis in this particular clinical scenario, polymerase chain reaction (PCR) testing and hospital admittance for 48 hours of antibiotic therapy is considered appropriate. However, PCR testing "cannot be performed on a timely basis in most centers," McCracken cautioned. In addition, if the infant had received one dose of ceftriaxone (Rocephin, Roche) 24 hours before arriving at the hospital, McCracken said he would have waited for PCR results before allowing the patient to go home. Home therapy once the infant is stable is also a possibility. In any event, "I would estimate that 70% of our children with meningitis now are diagnosed after having received a dose of ceftriaxone," McCracken said.
For pneumococcal meningitis,
vancomycin and a cephalosporin (cefotaxime [Claforan, Aventis] or ceftriaxone)
are considered standard initial treatment before knowing the susceptibility of
the organism. However, "vancomycin can be a difficult agent to use in some
senses," McCracken noted. "It doesn't have great penetration, but even with
steroids it penetrates well enough to be effective as long as the physician
monitors serum values. You want to achieve concentrations in the 30 mg/mL
range. Then you know you have good concentrations in CSF," he said.
There have been some concerns with toxicity, but McCracken assured that it is rare today. "I have not encountered a documented case of vancomycin toxicity in the past 10 years."
McCracken said he is hopeful that within the next few years, one of the newer fluoroquinolones will be available, "so that we have a single agent to use for treatment of meningitis. They are very effective."
If the CSF isolate of Streptococcus pneumoniae is resistant to the cephalosporins, you should perform a repeat lumbar puncture (LP) at 24 to 30 hours.
"With gram negatives, there is no question that the longer the positive cultures, the worse the outcome. This was clear with Haemophilus is well," McCracken said. "But I don't know if that is true with gram-positive pathogens in CSF. No one has ever shown that having a positive culture at 24 hours with pneumococcus renders a worse prognosis. I still feel better, though, to know that we've achieved the endpoint that we desire: a sterile CSF."
Another scenario involved a patient pretreated with ceftriaxone, who has a WBC count of 2,400/mm3 with no left shift and a glucose level <10 mg/dL. However, the tests come back negative. The physician still believes the child has a bacterial etiology and has been administering vancomycin. He believed vancomycin should be administered at this time, although in the future, pneumococcal immunization may make this unnecessary. Should the physician discontinue the vancomycin?
A repeat spinal tap "might show you a few organisms, especially if it is resistant," McCracken said. In any event, "you hope that the other doctor will send the spinal fluid with the patient; however, frequently this does not occur."
In the child who has not received an antibiotic in the emergency department, dexamethasone therapy along with antibiotic therapy is often used. However, "It has never been shown clearly in the prospective studies that this regimen works for pneumococcal meningitis in children, yet in animals it seems to. And for Haemophilus, no one questions steroid therapy in children, but one rarely encounters Haemophilus in developed nations that use routine Haemophilus immunization," McCracken said.
The interactive session also addressed the impact of the newly licensed pneumococcal conjugate vaccine. Will it change the way one manages a fully immunized child with a suspicion of bacterial meningitis?
"My guess is that it would impact therapy," McCracken said. "Not that it might not be pneumococcal disease, but I think the chances of a resistant pneumococcus are very small. Prevnar is such an effective vaccine for invasive disease, although I don't know if it will do much for otitis and sinusitis. Because the vaccine affects colonization and the potential for herd immunity, I probably would choose not to use vancomycin in the fully immunized infant. Resistance will not be gone, but I anticipate it will be a lot lower."
For more information:
- Jacobs RF, McCracken GH. Challenging pediatric cases: new and controversial antibiotic management. Presented at the 38th Annual Meeting of the Infectious Diseases Society of America. Session 77. Sept. 7-10, 2000. New Orleans.
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