JAC Advance Access originally published online on May 31, 2007
Journal of Antimicrobial Chemotherapy 2007 60(1):197-199; doi:10.1093/jac/dkm181
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Correspondence |
Acinetobacter baumannii meningitis in post-neurosurgical patients: clinical outcome and impact of carbapenem resistance
1 Department of Infectious Diseases and Clinical Microbiology, Erciyes University School of Medicine, Kayseri, Turkey 2 Department of Microbiology and Clinical Microbiology, Erciyes University School of Medicine, Kayseri, Turkey
* Corresponding author. Tel: +90-352-4374937/21050; Fax: +90-352-4375273; E-mail: gokhanmetan{at}gmail.com or gokhanmetan{at}hotmail.com
Keywords: A. baumannii , meningitis , carbapenem-resistant
Acinetobacter baumannii is responsible for a wide range of nosocomial infections including post-neurosurgical meningitis. In this study, we aimed to evaluate the factors that influenced the outcomes in patients with post-neurosurgical meningitis because of A. baumannii at Erciyes University Gevher Nesibe Hospital, a 1300-bed tertiary referral centre. To identify patients, the records of the infection control committee were reviewed for post-neurosurgical meningitis from January 1998 to February 2007, retrospectively. Patients older than 16 years of age were included in the analysis. A. baumannii meningitis was defined as described previously.1
The demographic information was extracted from the charts of the patients (Table 1). Appropriate therapy was defined as one or more agents active against A. baumannii, given adequate dose and route of administration, not later than 2 h after the CSF culture was obtained. Aminoglycoside monotherapy was considered inappropriate because of low penetration into CSF.
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All statistical analyses were performed using SPSS software (version 11.0; SPSS, Chicago, IL, USA). The comparison of the distribution of variables in compared groups was performed with
2 test or Fisher's exact test for categorical variables and Mann–Whitney test for continuous variables. Thirty-seven patients with post-neurosurgical A. baumannii meningitis were identified. Nine cases were excluded from the study because of missing data. The median patient age was 39.5 years and 15 patients were male. Mortality was higher in the group of patients who were older. As for other serious infections in the aged, the case-fatality ratio of meningitis is higher than that in younger individuals. Although mortality was higher in the female patients, this could be a result of older age. The mean age of female patients was 57.1 years.
The overall mortality rate was 71.4% in this study. The mean time to death was 16.8 days. Mortality rates from 12% to 70% were reported from studies that evaluated Gram-negative bacillary meningitis (GNBM).2–4 The cause of high mortality rate in this group of patients is complex because of the preceding neurosurgical events. In a recent study evaluating the predictors of mortality in nosocomial meningitis, Pseudomonas aeruginosa and A. baumannii meningitis were significantly related to inferior outcome.5 Third-generation cephalosporins have been widely used in the treatment of GNBM, but an increasing rate of resistance to these agents made carbapenems the first choice for empirical treatment of GNBM after neurosurgery.1 However, carbapenem resistance has become a candidate as a significant clinical problem due to reduction in available treatment options.6 The initial treatment was a carbapenem (either monotherapy or in combination) in 96.7% of the patients. This was concordant with the recommendations for empirical therapy of nosocomial meningitis suspected to be caused by Gram-negative bacilli.1,2 Nine out of 28 (32.1%) of the patients were infected with a carbapenem-resistant strain. Inappropriate therapy and meningitis due to carbapenem-resistant A. baumannii were significantly frequent in the cases with poor outcome (Table 1). Appropriate empirical treatment of A. baumannii infections was associated with improved survival. Besides the inappropriate antimicrobial therapy, these patients are frequently associated with severe neurological deficits, and the underlying neurological state is a confounding factor for fatality.
The mortality rates were lower in previous reports of Acinetobacter meningitis, but in those studies the isolates were susceptible to carbapenems, which gave an effective therapeutic alternative.4,7
The emergence of multidrug-resistant (MDR) Gram-negative bacteria in CNS infections led to the intrathecal or intraventricular use of polymyxins as a favourable treatment choice.8 Although there was a high rate of carbapenem resistance, our experience with intrathecal colistin is limited to one female patient. After a week of intravenous therapy with meropenem and removal of external ventricular drainage catheter, CSF culture was not sterile, and glucose, protein and cell count did not improve. Intrathecal colistin 10 mg/day was added to the therapy. She received this regimen for 3 weeks. Neither CSF sterilization nor clinical cure was achieved during the therapy. Unfortunately, in vitro susceptibility of the infecting strain to colistin was unavailable. Colistin is not commercially present in our country and routine antibiogram tests do not include polymyxins. The recently approved tigecycline is a therapeutic option for adults with complicated skin and skin structure infections caused by MDR A. baumannii; however, it is unavailable in many countries and effectiveness for meningitis has not been studied yet.
In conclusion, we present a high rate of mortality for carbapenem-resistant A. baumannii meningitis. There is no viable alternative for the treatment of MDR A. baumannii infections. Colistin has been reported as a highly active antimicrobial agent against MDR Gram-negative bacilli infections in different studies. Prospective trials with intrathecal and/or intravenous colistin could help to define an appropriate therapy for MDR A. baumannii meningitis.
None to declare.
Acknowledgements
We thank Bilge K
ran for her assistance in reviewing the infection control committee records and Ahmet Ozturk for statistical analysis.
References
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