Skip to main page content

• HOME
• Current Issue
• Archive
• Alerts
• About ASM
• Contact us
• Tech Support
• Journals.ASM.org

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chaves, F. Articles by Otero, J. R. Search for Related Content PubMed PubMed Citation Articles by Chaves, F. Articles by Otero, J. R.

 Previous Article  |  Next Article 

Journal of Clinical Microbiology, January 2003, p. 512-513, Vol. 41, No. 1
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.1.512-513.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

CASE REPORT

Meningitis Due to Mixed Infection with Penicillin-Resistant and Penicillin-Susceptible Strains of Streptococcus pneumoniae

Fernando Chaves,^* Carolina Campelo, Francisca Sanz, and Joaquin R. Otero

Servicio de Microbiología, Hospital Universitario Doce de Octubre, 28041 Madrid, Spain

Received 27 August 2002/ Returned for modification 24 September 2002/ Accepted 14 October 2002

Top Abstract Case report References

 
Streptococcus pneumoniae is the major cause of bacterial meningitis. We report a case of meningitis due to a mixed infection with two distinct strains of S. pneumoniae: one penicillin-resistant strain of serotype 9V and one penicillin-susceptible strain of serotype 7. The two strains exhibited different pulsed-field gel electrophoresis profiles.

Top Abstract Case report References

 
A 60-year-old male patient with a medical history of arterial hypertension, diabetes mellitus, alcohol abuse, and heavy smoking presented to the emergency service with dizziness, fever, and signs of meningism. One week prior to this, he had been diagnosed with acute otitis media and received therapy with oral amoxicillin-clavulanate. At the time of admission to the intensive care unit the patient was acutely ill. A lumbar puncture yielded a cloudy cerebrospinal fluid (CSF) sample, and laboratory analysis revealed a white blood cell count of 3,600 cells/ml (97% polymorphonuclear cells), a protein level of 224 mg/dl, and a glucose level of 144 mg/dl (blood glucose level, 276 mg/dl). Gram staining of the CSF showed gram-positive cocci in pairs and chains. The patient was treated empirically with ceftriaxone, vancomycin, and ampicillin. Two days after admission, a central nervous system computed tomography scan showed evidence of mastoiditis, and the area was drained surgically. Cultures of CSF and blood yielded Streptococcus pneumoniae. Susceptibility testing of the CSF isolate was performed by the E-test strip method (AB Biodisk, Solna, Sweden). The ellipse of organism growth inhibition intercepted the penicillin strip at 0.012 µg/ml, but due to the growth of discrete colonies with identical morphology within the zone of inhibition up to a MIC of 2 µg/ml, the isolate was reported as resistant to penicillin (4). The penicillin-resistant isolate was also found to be susceptible to cefotaxime, vancomycin, erythromycin, and clindamycin. On days 3 and 4 of hospitalization, treatment with ampicillin and vancomycin, respectively, was discontinued. The patient completed a course of antimicrobial treatment with ceftriaxone over a period of 14 days and was discharged in good health.

We decided to investigate the intriguing presence of colonies within the zone of inhibition of penicillin. Two possible explanations were considered: selection of chromosomally mediated mutations of the penicillin-binding proteins within a single strain of S. pneumoniae or, alternatively, a mixed infection with two or more different strains of the organism, at least one of which was resistant to penicillin. Colonies from the zone close to the 2-µg/ml mark on the penicillin strip and from the confluent zone of growth were subcultured, retested by the broth microdilution method, and serotyped. Colonies exhibiting resistance to penicillin (isolate 1; MIC, 2 µg/ml) were identified as serogroup 9V and showed intermediate resistance to cefotaxime (MIC, 1 µg/ml) and erythromycin (MIC, 0.5 µg/ml) and susceptibility to vancomycin (MIC, 0.5 µg/ml), tetracycline (MIC, 0.5 µg/ml), and chloramphenicol (MIC, 2 µg/ml). Colonies that exhibited full susceptibility to penicillin (isolate 2; MIC, 0.012 µg/ml) were identified as serogroup 7 and were susceptible to cefotaxime (MIC, 0.015 µg/ml), erythromycin (MIC, 0.12 µg/ml), vancomycin (MIC, 0.5 µg/ml), tetracycline (MIC, 0.25 µg/ml), and chloramphenicol (MIC, 2 µg/ml).

Although clinical isolates of S. pneumoniae within a clonal group typically share the same serotype, capsular switching within a well-defined S. pneumoniae clone has been described elsewhere (5, 8). For this reason and to determine whether the two isolates belonged to the same clonal group, both were characterized by standard pulsed-field gel electrophoresis (PFGE) (7) with the restriction endonuclease SmaI. PFGE analysis of the DNA revealed that the S. pneumoniae isolates exhibited more than eight band differences, which clearly qualifies them for their designation at two separate strains (Fig. 1, lanes 3 and 4). We interpreted these results to indicate that the patient's meningitis was due to a mixed infection with two entirely distinct strains: one penicillin resistant, of serotype 9V, and the other penicillin susceptible, of serotype 7.

View larger version (95K): [in this window] [in a new window]

FIG. 1. PFGE of clinical isolates of S. pneumoniae. Lane 1, isolate from blood (serotype 14); lane 2, isolate from catheter (serotype 3). Both were unrelated strains from other patients. Lanes 3 and 4, isolates from CSF (see text); lane M, molecular size marker.

Bacterial meningitis is the most severe and frequent infection of the central nervous system, with a mortality rate of up to 20% and an adverse neurological outcome in up to 50% of survivors. S. pneumoniae has come to be recognized as the major cause of bacterial meningitis in developed countries (3). In Spain, 43% of pneumococci recovered from CSF express intermediate or full resistance to penicillin, presenting serious problems for treatment (2). Twenty-five percent of these cases are due to the more prevalent serotypes with resistance to penicillin (23F, 9V, and 6B) (1). Notably, the prevalence of penicillin-susceptible strains of serogroup 7 has recently shown evidence of a decline, from 6% of all isolates in 1990 to 1% in 1996 (2).

To the best of our knowledge, this is the first time that a case of meningitis due to a mixed infection with different strains of S. pneumoniae has been described. Recently, Tsai et al. reported a case of bacteremic pneumonia caused by a single clone of S. pneumoniae, individual colonies from which exhibited different optochin susceptibilities (9). Pikis et al. also described three isolates of S. pneumoniae obtained from the CSF, blood, and nasopharynx of three different patients. These were all shown to contain mixed populations of optochin-susceptible and -resistant organisms, although the two variants exhibited the same antibiogram, serotype, and PFGE profiles (6). The frequency with which mixed pneumococcal infections occur is unknown. This phenomenon might easily be underreported because discrete colonies within the zone of inhibition of an antimicrobial agent are typically considered to represent a minor subpopulation of resistant mutants of the same strain. Full identification and characterization of these organisms are therefore not routinely performed. Furthermore, in cases of meningitis involving fully susceptible S. pneumoniae, the possibility of mixed infection with different serotypes or genotypes is not usually considered. The clinical implications of infection with a mixture of susceptible and resistant strains of S. pneumoniae are serious if the condition is not recognized in a timely manner and the appropriate therapy is not provided. The administration of inappropriate treatment might lead to selective growth of the resistant population and severe complications for the patient. Our observations highlight the importance of the recommendation of the National Committee for Clinical Laboratory Standards for testing a mixture of several pneumococcal colonies instead of analysis of individual colonies of S. pneumoniae, in order to obtain an accurate susceptibility report.

Whenever there is evidence of a mixture of susceptible and resistant organisms in a population, it is important to consider the possible clinical implications. Enhanced surveillance is necessary in order to determine the frequency with which infections due to mixed populations occur and to track the emergence of serotypes with enhanced virulence.

 
We thank "Laboratorio de Referencia de Neumococos" (Centro Nacional de Microbiología, Madrid, Spain) for serotyping the clinical isolates of S. pneumoniae included in this study and Tobin Hellyer and Fernando Dronda for their suggestions and comments.

 
* Corresponding author. Mailing address: Servicio de Microbiología, Hospital Universitario Doce de Octubre, Avenida de Cordoba sn, Madrid 28041, Spain. Phone: (34) 91-3908239. Fax: (34) 91-5652765. E-mail: fchaves.hdoc{at}salud.madrid.org.

Top Abstract Case report References

 

1
1. Enright, M. C., A. Fenoll, D. Griffiths, and B. G. Spratt. 1999. The three major Spanish clones of penicillin-resistant Streptococcus pneumoniae are the most common clones recovered in recent cases of meningitis in Spain. J. Clin. Microbiol. 37:3210-3216.[Abstract/Free Full Text]
2
2. Fenoll, A., I. Jado, D. Vicioso, A. Pérez, and J. Casal. 1998. Evolution of Streptococcus pneumoniae serotypes and antibiotic resistance in Spain: update (1990 to 1996). J. Clin. Microbiol. 36:3447-3454.[Free Full Text]
3
3. Meli, D. N., S. Christen, S. L. Leib, and M. G. Tauber. 2002. Current concepts in the pathogenesis of meningitis caused by Streptococcus pneumoniae. Curr. Opin. Infect. Dis. 15:253-257.[Medline]
4
4. National Committee for Clinical Laboratory Standards. 2002. Performance standards for antimicrobial susceptibility testing. Twelfth informational supplement M100-S12. National Committee for Clinical Laboratory Standards, Wayne, Pa.
5
5. Nesin, M., M. Ramirez, and A. Tomasz. 1998. Capsular transformation of a multidrug-resistant Streptococcus pneumoniae in vivo. J. Infect. Dis. 177:707-713.[Medline]
6
6. Pikis, A., J. M. Campos, W. J. Rodriguez, and J. M. Keith. 2001. Optochin resistance in Streptococcus pneumoniae: mechanism, significance and clinical implications. J. Infect. Dis. 184:582-590.[CrossRef][Medline]
7
7. Quale, J. M., D. Landman, C. Flores, and J. Ravishankar. 2001. Comparison of automated ribotyping to pulsed-field gel electrophoresis for genetic fingerprinting of Streptococcus pneumoniae. J. Clin. Microbiol. 39:4175-4177.[Abstract/Free Full Text]
8
8. Richter, S. S., K. P. Heilmann, S. L. Coffman, H. K. Huynh, A. B. Brueggemann, M. A. Pfaller, and G. V. Doern. 2002. The molecular epidemiology of penicillin-resistant Streptococcus pneumoniae in the United States, 1994-2000. Clin. Infect. Dis. 34:330-339.[CrossRef][Medline]
9
9. Tsai, H.-T., P.-R. Hsueh, L.-J. Teng, P.-I. Lee, L.-M. Huang, C.-Y. Lee, and K.-T. Luh. 2000. Bacteremic pneumonia caused by a single clone of Streptococcus pneumoniae with different optochin susceptibilities. J. Clin. Microbiol. 38:458-459.[Abstract/Free Full Text]

---

Journal of Clinical Microbiology, January 2003, p. 512-513, Vol. 41, No. 1
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.1.512-513.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Clarke, S. C. (2006). Control of pneumococcal disease in the United Kingdom - the start of a new era.. J Med Microbiol 55: 975-980 [Abstract] [Full Text]  
• Clarke, S. C., Jefferies, J. M. C., Smith, A. J., McMenamin, J., Mitchell, T. J., Edwards, G. F. S. (2006). Pneumococci causing invasive disease in children prior to the introduction of pneumococcal conjugate vaccine in Scotland.. J Med Microbiol 55: 1079-1084 [Abstract] [Full Text]  
• Clarke, S. C., Jefferies, J. M., Smith, A. J., McMenamin, J., Mitchell, T. J., Edwards, G. F. S. (2006). Potential Impact of Conjugate Vaccine on the Incidence of Invasive Pneumococcal Disease among Children in Scotland. J. Clin. Microbiol. 44: 1224-1228 [Abstract] [Full Text]  
• Marchandin, H., Ventura, V., Alonso, J.-M., Van de Perre, P. (2005). Mixed Bacterial Meningitis Due to Streptococcus pneumoniae and Neisseria meningitidis in an 18-Month-Old Child. J. Clin. Microbiol. 43: 1477-1479 [Abstract] [Full Text]  
• de Andrade, A. L. S. S., Pimenta, F. C., Laval, C. A. B., de Andrade, J. G., Guerra, M. L., Brandileone, M. C. C. (2004). Invasive Pneumococcal Infection in a Healthy Infant Caused by Two Different Serotypes. J. Clin. Microbiol. 42: 2345-2346 [Abstract] [Full Text]  
• Drancourt, M., Roux, V., Fournier, P.-E., Raoult, D. (2004). rpoB Gene Sequence-Based Identification of Aerobic Gram-Positive Cocci of the Genera Streptococcus, Enterococcus, Gemella, Abiotrophia, and Granulicatella. J. Clin. Microbiol. 42: 497-504 [Abstract] [Full Text]  

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chaves, F. Articles by Otero, J. R. Search for Related Content PubMed PubMed Citation Articles by Chaves, F. Articles by Otero, J. R.