Emergence of Macrolide-Resistant Mycoplasma pneumoniae in Hong Kong Is Linked to Increasing Macrolide Resistance in Multilocus Variable-Number Tandem-Repeat Analysis Type 4-5-7-2

Abstract

Macrolide-resistant Mycoplasma pneumoniae (MRMP) is rapidly emerging in Asia, but information on the temporal relationship between the increase in macrolide resistance and changes in strain types is scarce. Between 2011 and 2014, M. pneumoniae infection was diagnosed by PCR as part of routine care in a health care region in Hong Kong. Testing was initiated by clinicians, mainly in patients with suspected M. pneumoniae pneumonia. Specimens positive for M. pneumoniae were retrospectively investigated by macrolide resistance genotyping and a four-locus (Mpn13 to -16) multilocus variable-number tandem-repeat analysis (MLVA) scheme. The overall percentage of M. pneumoniae-positive specimens was 17.9%, with annual rates ranging from 9.8% to 27.2%. The prevalence of MRMP had rapidly increased from 13.6% in 2011 to 30.7% in 2012, 36.6% in 2013, and 47.1% in 2014 (P = 0.038). Two major MLVA types, 4-5-7-2 and 3-5-6-2, accounted for 75% to 85% of the infections each year. MLVA types 4-5-7-2 and 3-5-6-2 predominated among macrolide-resistant and macrolide-sensitive groups, respectively. The increase in MRMP was mainly caused by increasing macrolide resistance in the prevalent MLVA type 4-5-7-2, changing from 25.0% in 2011 to 59.1% in 2012, to 89.7% in 2013, and to 100% in 2014 (P < 0.001). In conclusion, increasing MRMP in Hong Kong was linked to a single MLVA type, which was both prevalent and increasingly resistant to macrolides.

FIG 1

M. pneumoniae-positive rate in respiratory specimens by date of request for a health care region in Hong Kong, January 2011 to December 2014. The histogram shows the monthly number of specimens tested. The dotted line shows the percentage of specimens positive for M. pneumoniae in each month. The horizontal line shows the average positive percentage for the entire period. Only one specimen per patient was included.

FIG 2

MLVA type in M. pneumoniae specimens in a health care region in Hong Kong, 2011 to 2014. The percentage of each MLVA type for each year is shown. The number of patients in each year is shown within parentheses.

FIG 3

Macrolide resistance in M. pneumoniae specimens in a health care region in Hong Kong, 2011 to 2014. (A) MLVA type according to macrolide resistance genotype. The proportions of MLVA types for MRMP (n = 67) and MSMP (n = 138) groups are shown in the outer and inner rings, respectively. Others in the MRMP group included types 4-6-7-3 and 5-5-7-2. Others in the MSMP group included types 3-6-6-2 and 4-4-7-3. (B) Changes in macrolide resistance rate of MLVA type 4-5-7-2 during 2011 to 2014. The number of patients in each year is shown within parentheses.