This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Winchell, J. M.
Right arrow Articles by Fields, B. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Winchell, J. M.
Right arrow Articles by Fields, B. S.

 Previous Article  |  Next Article 

Journal of Clinical Microbiology, September 2008, p. 3116-3118, Vol. 46, No. 9
0095-1137/08/$08.00+0     doi:10.1128/JCM.00440-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Evaluation of Three Real-Time PCR Assays for Detection of Mycoplasma pneumoniae in an Outbreak Investigation{triangledown}

Jonas M. Winchell,* Kathleen A. Thurman, Stephanie L. Mitchell, W. Lanier Thacker, and Barry S. Fields

Respiratory Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia

Received 5 March 2008/ Returned for modification 4 May 2008/ Accepted 24 June 2008


arrow
ABSTRACT
 
We compared the performances of three recently optimized real-time PCR assays derived from distinct genomic regions of Mycoplasma pneumoniae during an outbreak. Comprehensive evaluation established that a newly described toxin gene represents a superior target for detecting M. pneumoniae DNA in clinical specimens, although use of multiple targets may increase testing confidence.


arrow
TEXT
 
Mycoplasma pneumoniae accounts for approximately 15% to 20% of all community-acquired pneumonia cases and is a common cause of outbreaks (10, 16, 18). Outbreaks have been reported to occur in 3- to 7-year intervals, and although all age groups are susceptible, incidence rates vary with age and may occur more frequently in certain settings (10, 16, 17). M. pneumoniae infection spreads efficiently within households and close living quarters, with incubation periods as long as 3 weeks (17). The insidious nature of this infection and its protracted disease course make this agent a predominant cause of "walking pneumonia" that can persist within the population and cause community or institutional outbreaks. Upper- and lower-respiratory-tract symptoms are often mild, resulting in tracheobronchitis, headache, and cough. Occasionally, severe cases with extrapulmonary involvement can result in hospitalization and death due to neurological disease, such as encephalitis (1, 2, 4, 15, 17). The high rate of morbidity and the occasional mortality reinforces the need for timely diagnosis for administering proper antibiotic treatment (7, 9).

Conventional tests for detecting M. pneumoniae are fraught with limitations (3). M. pneumoniae culture can often take several weeks, requires special media and expertise, and is insensitive and prone to contaminants and inhibitors. Serological assays such as complement fixation and commercially available immunoglobulin detection kits are by nature retrospective, requiring paired serum samples from both acute and convalescent phases, and provide questionable specificity and sensitivity results. In sum, these approaches are impractical for a rapid diagnosis. A variety of nucleic acid-based tests based upon PCR have been developed for the rapid and sensitive detection of M. pneumoniae (5, 11, 13, 14, 16). The range of variables within each PCR study (specimen type, nucleic acid extraction and amplification procedures, target selection, definitions used in calculating data, etc.) makes it difficult to compare results and draw a single, comprehensive approach for reliable detection.

Recent community outbreaks of M. pneumoniae infection underscore a need among public health departments and local hospitals for a rapid and reliable diagnostic assay (1, 10, 12, 17, 18). Moreover, this test should be highly specific and sensitive and should be evaluated in an outbreak setting. The aim of the current study was to evaluate the use of three recently optimized real-time PCR assays for the detection of M. pneumoniae in respiratory samples from a recent outbreak. To our knowledge, this is the first prospective and comparative study of real-time PCR targets used to identify cases during an outbreak investigation of M. pneumoniae and the first report of a study targeting the recently identified ADP-ribosylating toxin gene encoding the CARDS (community-acquired respiratory distress syndrome) toxin for real-time PCR detection.

Multiple TaqMan primer-probe sets targeting the ATPase gene (GenBank accession no. U43738) and the CARDS toxin gene (GenBank accession no. DQ447750) of M. pneumoniae were designed using Primer Express version 3.0 (Applied Biosystems, Foster City, CA) (8). The real-time PCR mixture was prepared in a total volume of 25 µl. Each PCR mixture contained the following per reaction: 12.5 µl of Platinum quantitative PCR SuperMix-UDG (catalog no. 11730-025; Invitrogen), 1.5 µl of 50 mM MgCl2, 0.5 uM final concentrations of each primer, a 0.1 uM final concentration of the probe, 1.25 U of Platinum Taq DNA polymerase (catalog no. 10966-034; Invitrogen) (5 U/µl), 1 µl of 10 mM PCR nucleotide mix (catalog no. C1141; Promega), 5 µl of extracted nucleic acid from each specimen, and nuclease-free water (catalog no. P1193; Promega) to achieve a 25-µl final volume. Real-time PCR for each target was performed using an ABI 7500 system (Applied Biosystems) under the following conditions: initial activation of 95°C for 2 min, followed by 45 cycles of 95°C for 10 s and 60°C for 30 s. After thorough analysis and evaluation of the primer-probe sets, which involved BLAST searches, one toxin (Mp181) and two ATPase (Mp3 and Mp7) gene targets were selected based upon specificity and sensitivity performance and optimized to achieve maximum efficiency (Table 1). Each assay demonstrated >99% efficiency, as calculated using a standardized dilution series of quantitated DNA samples of M. pneumoniae tested using six replicates over six logs (100 pg to 1 fg). The average from these data is reported as the square of the coefficient of regression values (efficiency) in Table 1. The sensitivity of each assay was determined by extracting a series of dilutions from quantitated stocks of both prototypical strains of M. pneumoniae (M129 [type I] and FH [type 2]) by use of a ChargeSwitch gDNA Mini Bacteria kit (catalog no. CS11301; Invitrogen) following the manufacturer's instructions. The CFU value per milliliter of each dilution was determined using a hemolytic plaque formation procedure as previously described (6). Each dilution was then tested with each assay in six replicates; values are reported in Table 1 as total CFU detected within each real-time PCR. Use of Mp181 consistently detected between 1 and 5 CFU, while assays using both Mp3 and Mp7 were slightly less sensitive, detecting 5 to 50 CFU. Each assay was also tested for specificity with at least 15 ng of nucleic acid and showed no cross-reactivity with an extensive bacterial and viral pathogen panel consisting of the following targets: Mycoplasma faecium, Mycoplasma lipophilum, Mycoplasma salivarium, Mycoplasma pirum, Mycoplasma orale, Mycoplasma penetrans, Mycoplasma genitalium, Mycoplasma hominis, Mycoplasma fermentans, Mycoplasma buccale, Mycoplasma arginini, Mycoplasma hyorhinis, Mycoplasma amphoriforme, Lactobacillus planitarium, Staphylococcus epidermidis, Coxiella burnetii, Streptococcus salivarius, Bordetella pertussis, Legionella pneumophila, Legionella longbeachae, Streptococcus pneumoniae, Ureaplasma urealyticum, Neisseria meningitidis, Chlamydia trachomatis, Chlamydophila psittaci, Chlamydophila pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Neisseria elongata, Pseudomonas aeruginosa, Moraxella catarrhalis, Mycobacterium tuberculosis, Candida albicans, Escherichia coli, Staphylococcus aureus, Ureaplasma parvum, human DNA, human coronavirus, human rhinovirus, human parainfluenza virus 2, human parainfluenza virus 3, human adenovirus, influenza virus A, influenza virus B, respiratory syncytial virus A, and respiratory syncytial virus B.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Primers and probes for real-time amplification of M. pneumoniae targets

These assays were used to identify a recent M. pneumoniae outbreak within a college setting. A total of 54 respiratory samples (oropharyngeal and nasopharyngeal swabs) from patients (n = 35) and negative controls (n = 19) 18 to 35 years of age (mean, 21.7) were tested in triplicate with each M. pneumoniae-specific assay (Mp3, Mp7, and Mp181) along with an RNase P internal control to ensure proper nucleic acid extraction and integrity. The data in Table 2 demonstrate that 18 of 35 pneumonia cases (~51%), where a pneumonia case is defined as exhibiting fever (≥100.4°F) and cough or pneumonia diagnosed by chest X-ray or clinical examination during a 12-week outbreak period, were positive with all three signature sequences. Of note, the Mp181 assay routinely exhibited crossing-threshold values earlier than both the Mp7 and the Mp3 assays (P < 0.0001 and P = 0.06, respectively, following Student's t test), which is concordant with the sensitivity data of Table 1. The crossing-threshold values ranged from ~26 to ~39, depending on the target, and displayed a typical sigmoidal curve similar to that seen with the positive controls, as did all RNase P assays (data not shown). All negative controls (defined as age-matched asymptomatic subjects within the same population) and samples from 16 patients demonstrated no reactivity with any of the M. pneumoniae-specific markers but gave positive RNase P signals (data not shown). The lack of PCR reactivity in the 16 cases may reflect the presence of an infection with a different pathogen or poor sample quality. Serum samples were collected from a limited number of subjects and proved to be of little value for diagnosis. Serological assays are often unreliable due to specificity and sensitivity limitations and the documented persistence of antibodies in patients (3).


View this table:
[in this window]
[in a new window]

  		TABLE 2. Average crossing-threshold values for Mp181, Mp3, and Mp7 gene targets from clinically defined cases of pneumonia with positive real-time PCR dataa

This study evaluated three real-time PCR assays targeting the ATPase and newly described CARDS toxin genes during a recent outbreak for the purpose of assessing its utility in such instances. Although other real-time PCR assays for the detection of M. pneumoniae have been reported, none have been applied to an investigation involving an outbreak. Interestingly, the assay targeting the CARDS toxin gene (Mp181) proved to be the most sensitive in identifying positive specimens during this outbreak and has been subsequently used to positively identify M. pneumoniae DNA in other specimens (respiratory and cerebrospinal fluid) in sporadic cases. These data support the use of the Mp181 assay as an initial screening marker for detecting the presence of M. pneumoniae DNA in respiratory clinical specimens, although the inclusion of Mp3 and Mp7 may provide an increased level of confidence for the reporting of results. The use of these assays may allow the rapid identification of an M. pneumoniae outbreak at the local and state levels when testing is implemented in a timely manner. Further investigation of each assay may be warranted for possible use in clinical practice.


arrow
ACKNOWLEDGMENTS
 
We thank Lauri Hicks, Nick Walter, Gavin Grant, and Utpala Bandy for providing specimens and helpful discussions surrounding this report. We also thank Lauri Hicks for critical review of the manuscript and Bernard J. Wolff for assistance with statistical analysis.


arrow
FOOTNOTES
 
* Corresponding author. Mailing address: Centers for Disease Control and Prevention, 1600 Clifton Rd. N.E., MS G-03, Atlanta, GA 30333. Phone: (404) 639-4921. Fax: (404) 639-4215. E-mail: jwinchell{at}cdc.gov Back

{triangledown} Published ahead of print on 9 July 2008. Back


arrow
REFERENCES
 
    1
  1. Alexander, N. E., H. Jordan, J. Sejvar, J. Winchell, K. Thurman, N. D. Walter, L. Hicks, U. Bandy, and P. Dennehy. 2007. Mycoplasma pneumoniae neurological disease associated with a community respiratory outbreak—Rhode Island, 2006-2007. Abstr. 45th Infect. Dis. Soc. Am. Annu. Conf., abstr. 213.
    2. 2
  2. Cunha, B. A. 2006. The atypical pneumonias: clinical diagnosis and importance. Clin. Microbiol. Infect. 12:12-24.[Medline]
    3. 3
  3. Daxboeck, F., R. Krause, and C. Wenisch. 2003. Laboratory diagnosis of Mycoplasma pneumoniae infection. Clin. Microbiol. Infect. 9:263-273.[CrossRef][Medline]
    4. 4
  4. Dorigo-Zetsma, J. W., R. P. Verkooyen, H. P. van Helden, H. van der Nat, and J. M. van den Bosch. 2001. Molecular detection of Mycoplasma pneumoniae in adults with community-acquired pneumonia requiring hospitalization. J. Clin. Microbiol. 39:1184-1186.[Abstract/Free Full Text]
    5. 5
  5. Gullsby, K., M. Storm, and K. Bondeson. 2008. Simultaneous detection of Chlamydophila pneumoniae and Mycoplasma pneumoniae by use of molecular beacons in a duplex real-time PCR. J. Clin. Microbiol. 46:727-731.[Abstract/Free Full Text]
    6. 6
  6. Hedreyda, C. T., and D. C. Krause. 1995. Identification of a possible cytadherence regulatory locus in Mycoplasma pneumoniae. Infect. Immun. 63:3479-3483.[Abstract]
    7. 7
  7. Hyde, T. B., M. Gilbert, S. Schwartz, R. Zell, J. Watt, W. L. Thacker, D. F. Talkington, and R. Besser. 2001. Azithromycin prophylaxis during a hospital outbreak of Mycoplasma pneumoniae pneumonia. J. Infect. Dis. 183:907-912.[CrossRef][Medline]
    8. 8
  8. Kannan, T. R., and J. B. Baseman. 2006. ADP-ribosylating and vacuolating cytotoxin of Mycoplasma pneumoniae represents unique virulence determinant among bacterial pathogens. Proc. Natl. Acad. Sci. USA 103:6724-6729.[Abstract/Free Full Text]
    9. 9
  9. Klausner, J. D., D. Passaro, J. Rosenberg, W. L. Thacker, D. F. Talkington, S. B. Werner, and D. J. Vugia. 1998. Enhanced control of an outbreak of Mycoplasma pneumoniae pneumonia with azithromycin prophylaxis. J. Infect. Dis. 177:161-166.[Medline]
    10. 10
  10. Klement, E., D. F. Talkington, O. Wasserzug, R. Kayouf, N. Davidovitch, R. Dumke, Y. Bar-Zeev, R. Merav, J. Boxman, W. L. Thacker, D. Wolf, T. Lazarovich, Y. Shemer-Avni, D. Glikman, E. Jacobs, I. Grotto, C. Block, and R. Nir-Paz. 2006. Identification of risk factors for infection in an outbreak of Mycoplasma pneumoniae respiratory tract disease. Clin. Infect. Dis. 43:1239-1245.[CrossRef][Medline]
    11. 11
  11. Loens, K., D. Ursi, H. Goossens, and M. Ieven. 2003. Molecular diagnosis of Mycoplasma pneumoniae respiratory tract infections. J. Clin. Microbiol. 41:4915-4923.[Free Full Text]
    12. 12
  12. Mezarina, K. B., A. Huffmire, J. Downing, N. Core, K. Gershman, and R. Hoffman. 2001. Outbreak of community-acquired pneumonia caused by Mycoplasma pneumoniae—Colorado 2000. MMWR Morb. Mortal. Wkly. Rep. 50:227-230.[Medline]
    13. 13
  13. Pitcher, D., V. J. Chalker, C. Sheppard, R. C. George, and T. G. Harrison. 2006. Real-time detection of Mycoplasma pneumoniae in respiratory samples with an internal processing control. J. Med. Microbiol. 55:149-155.[Abstract/Free Full Text]
    14. 14
  14. Saito, R., Y. Misawa, K. Moriya, K. Koike, K. Ubukata, and N. Okamura. 2005. Development and evaluation of a loop-mediated isothermal amplification assay for rapid detection of Mycoplasma pneumoniae. J. Med. Microbiol. 54:1037-1041.[Abstract/Free Full Text]
    15. 15
  15. Tsiodras, S., I. Kelesidis, T. Kelesidis, E. Stamboulis, and H. Giamarellou. 2005. Central nervous system manifestations of Mycoplasma pneumoniae infections. J. Infect. 51:343-354.[CrossRef][Medline]
    16. 16
  16. Waites, K. B., and D. F. Talkington. 2004. Mycoplasma pneumoniae and its role as a human pathogen. Clin. Microbiol. Rev. 17:697-728.[Abstract/Free Full Text]
    17. 17
  17. Walter, N. D., G. Grant, J. Winchell, S. Schwartz, N. Alexander, U. Bandy, and M. Moore. 2007. Community outbreak of Mycoplasma pneumoniae—Rhode Island, 2006. Abstr. 45th Infect. Dis. Soc. Am. Annu. Conf., abstr. 753.
    18. 18
  18. Waring, A. L., T. A. Halse, C. K. Csiza, C. J. Carlyn, K. A. Musser, and R. J. Limberger. 2001. Development of a genomics-based PCR assay for detection of Mycoplasma pneumoniae in a large outbreak in New York State. J. Clin. Microbiol. 39:1385-1390.[Abstract/Free Full Text]

Journal of Clinical Microbiology, September 2008, p. 3116-3118, Vol. 46, No. 9
0095-1137/08/$08.00+0     doi:10.1128/JCM.00440-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Touati, A., Benard, A., Hassen, A. B., Bebear, C. M., Pereyre, S. (2009). Evaluation of Five Commercial Real-Time PCR Assays for Detection of Mycoplasma pneumoniae in Respiratory Tract Specimens. J. Clin. Microbiol. 47: 2269-2271 [Abstract] [Full Text]  
  • Dumke, R., Jacobs, E. (2009). Comparison of Commercial and In-House Real-Time PCR Assays Used for Detection of Mycoplasma pneumoniae. J. Clin. Microbiol. 47: 441-444 [Abstract] [Full Text]  
  • Wolff, B. J., Thacker, W. L., Schwartz, S. B., Winchell, J. M. (2008). Detection of Macrolide Resistance in Mycoplasma pneumoniae by Real-Time PCR and High-Resolution Melt Analysis. Antimicrob. Agents Chemother. 52: 3542-3549 [Abstract] [Full Text]  

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Winchell, J. M.
Right arrow Articles by Fields, B. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Winchell, J. M.
Right arrow Articles by Fields, B. S.

Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»