Comparison of the molecular characteristics of Mycoplasma pneumoniae from children across different regions of China

Abstract

Previous molecular characterization of Mycoplasma pneumoniae in China focused only on one or two cities. In this study, we characterized 835 samples from patients suspected to be infected with M. pneumoniae; these samples were collected in 2016 from pediatric patients from different regions of China. Multiple locus variable number tandem repeat analysis (MLVA), P1-restriction fragment length polymorphism (RFLP) analysis, and sequencing of the domain V of 23S rRNA were performed to compare genotype distribution across different locations. Two-hundred-and-thirteen samples tested positive for M. pneumoniae by PCR. P1 types were identified in 154 samples: 78.6% were type I and 21.4% were type II. Type I was the most prevalent genotype in five locations, except Nanjing where type II was the most common type (p < 0.01). Five distinct MLVA types were identified in the 172 samples. Genotype M4-5-7-2 was predominant at all locations, except Nanjing where type 3-5-6-2 was the most common (p < 0.01). Macrolide resistance-associated mutations were identified in 186 (76.3%) samples. The resistance rate differed with the location. This study showed that genotypes and macrolide resistance rate differed across China. The most prevalent genotype in China remains M4-5-7-2/P1-1. The resistance rate decreased, along with changes to the M4-5-7-2 genotype.

Fig 1. Locality map of different cities included in this study.

A total of 835 samples from pediatric patients presenting with the symptoms of respiratory tract infection (RTI) belonging to five different geographical locations in China were collected from January to December 2016. Two-hundred-and-forty-three samples were from Beijing, which is located in mid-north China; 100, from Shanghai, located in the east; 275, from Kunming, Yunnan province, located in the south; 140, from Harbin, Heilongjiang province, located in the north; and 72, from Urumqi, Xinjiang province, located in the west. Ten M. pneumoniae-positive DNA samples isolated from 10 clinical specimens were collected from pediatric patients in Nanjing, which is close to Shanghai.

Fig 2. Genotype distribution across different sites.

Different colors are used to represent the genotypes observed at different sites.

Fig 3. Sequence comparison of the locus Mpn 15.

M129, M. pneumoniae reference strain; KM-Mpn15, the special sequence of Mpn15 from Kunming; BJ-Mpn15, the normal sequence of Mpn15 from Beijing; all repeat sequences in Mpn15 were 21-bp-long, except repeat 3, which was a 14-bp-long truncated sequence.

Fig 4. Different genotypes observed in macrolide-resistant and macrolide-sensitive specimens obtained from different sites in China.

R, resistant; S, sensitive; Undetectable, the repeat number of the four loci could not be fully determined because of low DNA concentration.