Mycoplasma pneumoniae: A Potentially Severe Infection

Mycoplasma pneumoniae infections remain one of the most common etiologies of community-acquired pneumonia (CAP). The clinical presentation and manifestations vary widely and can affect all organs of the body. Diagnosis is challenging because there are no constant findings in physical exams or laboratory or radiological assessments that indicate Mycoplasma pneumoniae pneumonia, and specific diagnostic tools are not readily available. Extrapulmonary manifestations and severe pulmonary manifestations can lead to long-term sequelae. The increasing emergence of Mycoplasma pneumoniae that is resistant to macrolides in some areas of the world and increased world travel could add to the difficulty of controlling and treating Mycoplasma pneumoniae infections. We present a concise and up-to-date review of the current knowledge of Mycoplasma pneumoniae pneumonia.

Development of macrolide resistance-associated mutations after macrolide treatment in children infected with Mycoplasma pneumoniae

PURPOSE

To determine the timing of the emergence of macrolide-resistant mutations after macrolide treatment in individuals with Mycoplasma pneumoniae infections.

METHODOLOGY

Between October 2011 and December 2013, serial pharyngeal swab specimens were collected before and after macrolide treatment from 21 otherwise healthy children infected with M. pneumoniae without macrolide-resistant mutations. The copy numbers of a M. pneumoniae gene and the proportion of clones showing macrolide-resistance mutations were determined for each specimen.

RESULTS

After macrolide treatment (10-15 mg kg^-1 day^-1 clarithromycin for 5-10 days or 10 mg kg^-1 day^-1 azithromycin for 3 days), fever resolved in 19 (90 %) of 21 children within 1 to 2 days, and the M. pneumoniae gene copy number decreased in all but one specimen in the second set of specimens relative to the number in the corresponding initial specimens. None of the second specimens, which were collected 2-4 days after initiation of macrolide treatment, showed mutations in the 23S rRNA gene. However, the proportion of mutant clones with A2063G and A2064G mutations in the specimens collected 7-24 days after initiation of treatment increased to 100 %. We identified a family in which three members had M. pneumoniae infections. The analysis of transmission in this household indicated that the M. pneumoniae harbouring a macrolide-resistant mutation that developed in the index patient after macrolide treatment was not transmitted to the family members.

CONCLUSION

A macrolide-resistant population might develop in individual patients up to 24 days after initiation of macrolide treatment. However, the decrease in M. pneumoniae load after macrolide administration effectively reduces interpersonal transmission.

Mycoplasma pneumoniae from the Respiratory Tract and Beyond

Mycoplasma pneumoniae is an important cause of respiratory tract infections in children as well as adults that can range in severity from mild to life-threatening. Over the past several years there has been much new information published concerning infections caused by this organism. New molecular-based tests for M. pneumoniae detection are now commercially available in the United States, and advances in molecular typing systems have enhanced understanding of the epidemiology of infections. More strains have had their entire genome sequences published, providing additional insights into pathogenic mechanisms. Clinically significant acquired macrolide resistance has emerged worldwide and is now complicating treatment. In vitro susceptibility testing methods have been standardized, and several new drugs that may be effective against this organism are undergoing development. This review focuses on the many new developments that have occurred over the past several years that enhance our understanding of this microbe, which is among the smallest bacterial pathogens but one of great clinical importance.

Clonal Spread of a Unique Strain of Macrolide-Resistant Mycoplasma Pneumoniae Within a Single Family in Italy

Macrolide-resistant Mycoplasma pneumoniae (MR-MP) is an increasing problem worldwide. This study describes the clonal spread of a unique strain of MR-MP within a single family. On January 23, 2015, nasopharyngeal swabs and sputum samples were collected from the index case (a 9-year-old girl) in southern Italy. The patient had pneumonia and was initially treated with clarithromycin. MR-MP infection was suspected due to prolonged symptoms despite appropriate antibiotic therapy. Two further cases of pneumonia occurred in relatives (a 7-year-old cousin and the 36-year-old mother of the index case); therefore, respiratory samples were also collected from other family members. Sequence analysis identified mutations associated with resistance to macrolides. Both P1 major adhesion protein typing and multiple loci variable-number tandem repeat analysis (MLVA) typing were performed to assess the relatedness of the strains. The index case, the cousin, the mother, and another 4 family members (twin siblings of the index case, a 3-year-old cousin, and the grandmother) were positive for MR-MP. All strains harbored the mutation A2063G, had the same P1 subtype (1), and were MLVA (7/4/5/7/2) type Z. In addition, the index case's aunt (31 years of age and the probable source of infection) harbored an M pneumoniae strain with the same molecular profile; however, this strain was susceptible to macrolides. This cluster of MR-MP infection/carriage caused by a clonal strain suggests a high transmission rate within this family and highlights the need for increased awareness among clinicians regarding the circulation of MR-MP. Novel strategies for the treatment and prevention of M pneumoniae infections are required.

[Gene Mutations Associated with Macrolide-resistance and p1 Gene Typing of Mycoplasma pneumoniae Isolated in Yamagata, Japan, between 2004 and 2013]

To clarify the epidemiologic features of Mycoplasma pneumoniae, we examined 358 M. pneumoniae strains isolated between 2004 and 2013 in Yamagata, Japan. Analysis of macrolide-resistance-associated 23S ribosomal RNA (rRNA) domain V mutations revealed 6 kinds of mutants (81 A2063G, 43 A2063T, 1 A2063C, 1 A2064C, 4 C2617G and 1 C2617 mutation). There were only two mutants before 2009, but mutants A2063T and A2063G increased in 2009 and from 2010, respectively. The annual ratio of mutants varied from 20.4% to 76.4% between 2009 and 2013. Typing of the p1 gene revealed 4 types; 278 type 1, and 3 kinds of type 2 variant strains (10 type 2a, 5 type 2b and 65 type 2c). Type 1 strains accounted for between 85.2% and 100% of isolates from 2004 to 2011, whereas type 2 variant strains increased by 26.5% and 66.1% in 2012 and 2013, respectively. These results indicate that type 1 strains may have been replaced by type 2 variant strains in 2013. Furthermore, the ratio of type 1 strains with a 23S rRNA mutation was 65.1% in 2012 and 95.2% in 2013, but none of the type 2 variant strains had this mutation. In conclusion, type 1 strains with macrolide-resistant mutations appeared in 2006 and increased from 2009. In contrast, type 2 variant strains, which increased in 2012 and became predominant in 2013, showed no mutations.

An iterative type I polyketide synthase initiates the biosynthesis of the antimycoplasma agent micacocidin

Micacocidin is a thiazoline-containing natural product from the bacterium Ralstonia solanacearum that shows significant activity against Mycoplasma pneumoniae. The presence of a pentylphenol moiety distinguishes micacocidin from the structurally related siderophore yersiniabactin, and this residue also contributes to the potent antimycoplasma effects. The biosynthesis of the pentylphenol moiety, as deduced from bioinformatic analysis and stable isotope feeding experiments, involves an iterative type I polyketide synthase (iPKS), which generates a linear tetraketide intermediate from acyl carrier protein-tethered hexanoic acid by three consecutive, decarboxylative Claisen condensations with malonyl-coenzyme A. The final conversion into 6-pentylsalicylic acid depends on a ketoreductase domain within the iPKS, as demonstrated by heterologous expression in E. coli and subsequent site-directed mutagenesis experiments. Our results unveil the early steps in micacocidin biosynthesis and illuminate a bacterial enzyme that functionally resembles fungal polyketide synthases.

Treating paediatric community-acquired pneumonia in the era of antimicrobial resistance

Increasing levels of paediatric community-acquired pneumonia (CAP), caused by drug-resistant bacteria and antimicrobial resistance, vary with age and countries and, in some cases, serotypes. When empirical first-line treatment administration fails, paediatricians should consider second-line treatments based on the prevalence of local resistance. A more judicious use of antimicrobial agents is also required.

CONCLUSION

Knowledge of local epidemiology and an appropriate use of antimicrobial drugs are necessary to treat CAP in this era of antimicrobial resistance.

Comparison of pyrosequencing, Sanger sequencing, and melting curve analysis for detection of low-frequency macrolide-resistant mycoplasma pneumoniae quasispecies in respiratory specimens

Macrolide-resistant Mycoplasma pneumoniae (MRMP) is emerging worldwide and has been associated with treatment failure. In this study, we used pyrosequencing to detect low-frequency MRMP quasispecies in respiratory specimens, and we compared the findings with those obtained by Sanger sequencing and SimpleProbe PCR coupled with a melting curve analysis (SimpleProbe PCR). Sanger sequencing, SimpleProbe PCR, and pyrosequencing were successfully performed for 96.7% (88/91), 96.7% (88/91), and 93.4% (85/91) of the M. pneumoniae-positive specimens, respectively. The A-to-G transition at position 2063 was the only mutation identified. Pyrosequencing identified A2063G MRMP quasispecies populations in 78.8% (67/88) of the specimens. Only 38.8% (26/67) of these specimens with the A2063G quasispecies detected by pyrosequencing were found to be A2063G quasispecies by Sanger sequencing or SimpleProbe PCR. The specimens that could be detected by SimpleProbe PCR and Sanger sequencing had higher frequencies of MRMP quasispecies (51% to 100%) than those that could not be detected by those two methods (1% to 44%). SimpleProbe PCR correctly categorized all specimens that were identified as wild type or mutant by Sanger sequencing. The clinical characteristics of the patients were not significantly different when they were grouped by the presence or absence of MRMP quasispecies, while patients with MRMP identified by Sanger sequencing more often required a switch from macrolides to an alternative M. pneumoniae-targeted therapy. The clinical significance of mutant quasispecies should be investigated further with larger patient populations and with specimens obtained before and after macrolide therapy.