Use of different approaches for the culture-independent typing of Mycoplasma pneumoniae from two geographically distinct regions

The Association between Mycoplasma pneumoniae Genotype and Cutaneous Disease

Mycoplasma pneumoniae (Mp) can cause several extrapulmonary manifestations, most frequently dermatological ones. It is largely unknown whether Mp genotype determines Mp-induced cutaneous disease. The aim of our study was to assess the association between Mp genotype and this clinical outcome. We performed a retrospective study of children referred with signs of acute Mp infection from 1 January 2014 to 31 December 2014. We compared the characteristics of children presenting as cutaneous disease, upper (URTI) and lower respiratory tract infection (LRTI). In addition, we separately analyzed the data of patients presenting with Mp-induced cutaneous disease. We evaluated data from 435 patients (mean age 7.3 years, SD 3.4 years; 52.0% boys) who had Mp PCR-positive pharyngeal swab, P1 genotype and/or multilocus variable-number tandem-repeat analysis (MLVA) genotype defined and no viral co-detection, presenting as cutaneous disease (38/435), URTI (46/435) or LRTI (351/435). The majority of patients had urticarial (55%, 21/38) or maculopapular eruptions (37%, 14/38). We found no association between Mp genotype and clinical outcome of cutaneous disease, nor any specific dermatological presentation. In the group with cutaneous disease, 18% (7/38) required hospital admission because of rash. We found that infection with MLVA-3,6,6,2 strains was more common in admitted patients than in outpatients (40% vs. 4%, p = 0.017) and significantly affected the likelihood of hospital admission in a logistic regression model. The results of our cohort study suggest that Mp genotype does not determine Mp-induced cutaneous disease or a specific dermatological presentation. Nevertheless, infections with certain MLVA strains could induce more severe cutaneous disease requiring hospitalization.

Mycoplasma pneumoniae multilocus variable-number tandem-repeat analysis genotypes are associated with inflammatory biomarker levels in children with lower respiratory tract infections

The multilocus variable-number tandem-repeat analysis (MLVA) typing method is commonly used in Mycoplasma pneumoniae (M. pneumoniae) epidemiology. It remains unknown if clinical manifestations of lower respiratory tract infections (LRTI) in children differ between different MLVA genotypes. We aimed to determine if specific M. pneumoniae MLVA genotypes indicate the severity of LRTI in children. We performed a retrospective study of children younger than 18 years with signs of acute M. pneumoniae LRTI from January 1, 2009, to December 31, 2014. All patients who were PCR-positive for M. pneumoniae from pharyngeal swabs and had MLVA genotype successfully defined were included in the study. We compared the epidemiological and clinical data of children infected with different MLVA genotypes. In total, 429 patients (mean age 7.4 years, SD 3.4 years; 54% boys) met the study inclusion criteria. We compared the data of patients infected with the three most common MLVA types: MLVA-3,5,6,2 (86/429), MLVA-3,6,6,2 (71/429) and MLVA-4,5,7,2 (256/429). MLVA-3,5,6,2-infected patients over 5 years of age presented with a significantly higher median C-reactive protein level (34 vs 23 vs 19 mg/L, p = .008) and a higher median white blood cell count (9.4 vs 7.9 vs 8.5 × 10⁹/L, p = .040) compared to MLVA-3,6,6,2- and MLVA-4,5,7,2-infected patients. No such difference was observed in the group of younger than 5 years. The results from our large cohort indicate that different MLVA genotypes may have different pathogenic potential and that children with MLVA-3,5,6,2 LRTI may present with higher inflammatory marker levels in comparison with other MLVA types.

Molecular Tools for Typing Mycoplasma pneumoniae and Mycoplasma genitalium

Mycoplasma pneumoniae and Mycoplasma genitalium are cell wall-less bacteria with strongly reduced genome content and close phylogenetic relatedness. In humans, the only known natural host, the microorganisms colonize the respiratory or genitourinary mucosa and may cause a broad range of clinical presentations. Besides fundamental differences in their tissue specificity, transmission route, and ability to cause prevalence peaks, both species share similarities such as the occurrence of asymptomatic carriers, preferred populations for infection, and problems with high rates of antimicrobial resistance. To further understand the epidemiology of these practically challenging bacteria, typing of strains is necessary. Since the cultivation of both pathogens is difficult and not performed outside of specialized laboratories, molecular typing methods with adequate discriminatory power, stability, and reproducibility have been developed. These include the characterization of genes containing repetitive sequences, of variable genome regions without the presence of repetitive sequences, determination of single and multi-locus variable-number tandem repeats, and detection of single nucleotide polymorphisms in different genes, respectively. The current repertoire of procedures allows reliable differentiation of strains circulating in different populations and in different time periods as well as comparison of strains occurring subsequently in individual patients. In this review, the methods for typing M. pneumoniae and M. genitalium, including the results of their application in different studies, are summarized and current knowledge regarding the association of typing data with the clinical characteristics of infections is presented.