Introduction
Pneumonia remains an important disease with significant morbidity and mortality in children across both developed and developing countries worldwide. It is estimated to be responsible for nearly 20% of all paediatric admissions in the developed world [1-3].
M. pneumoniae has been reported to cause up to 40% of community-acquired pneumonia (CAP) in children and about 18% of infections in patients requiring hospitalization.[4]
The current international recommended antibiotic treatment for children with CAP is to use macrolide to cover atypical bacterial pathogens if there is no response to first-line empirical beta-lactam antibiotics, or if the causative agent is compatible to atypical pathogens.[5,6]
Macrolide resistance has been increasingly observed in a number of countries across several continents since the first report in Japan in 2001 [7]. Yet there has been a wide variation in the resistant rate among different regions worldwide. In Europe and North America, the resistance rate is relatively lower with rates ranging from 2% to 23% in Germany and Italy, to 12% in Canada. In Asian countries, recent studies reported 30% in Japan to an alarmingly high rate of 90% in China. [7-15]
There is currently no territory wide surveillance of Mycoplasma in Hong Kong and hence the true epidemiology of M. pneumoniae remain unknown. Previous local publication in Hong Kong has shown up to a high 75% resistance rate in Hong Kong. However, the studied group was of a highly selective population, which involved patients not responsive to first line treatment previously. [16]
Although the use of antibiotic treatment of M. pneumoniaeassociated respiratory diseases is questioned by some physicians, most experts suggest that antibiotics should be systematically used, especially those involving the lower respiratory tract[17].
Beta-lactam antibiotics are generally considered the drugs of choice for treating respiratory diseases because they are active against most respiratory bacterial pathogens, but are ineffective against M. pneumoniae because they target the cell wall, which is lacking inM. pneumoniae .
In contrast, macrolides and tetracyclines which act as protein synthesis inhibitors, and quinolones which inhibit DNA synthesis and replication, are usually highly effective against M. pneumoniae, and are the drugs of choice for the treatment of infections due to atypical bacteria. Although macrolides are generally considered to be the first line of treatment, with recent emerging resistant strains of Mycoplasma, alternative antibiotics such doxycycline and levofloxacin has become increasingly used. However, doxycycline and levofloxacin have limited paediatric use due to their respective potential adverse effects such as teeth staining, enamel hypoplasia, depressed bone growth and articular problems, and considered for treatment when benefits appear to outweigh risks. Therefore we aim to look for clinical indicators to identify cases with likelihood of resistance, as molecular methods are not widely available in public hospitals in Hong Kong. This can guide the clinical decision of early treatment with doxycycline and therefore shorten the length of hospitalization and the overall burden on the health care system.
This study looks at a larger sample of patients beyond the previously published selected group of patients admitted with M. pnuemoniaeto a large regional hospital in Hong Kong. The aim is to extend the data surveillance for a clearer perspective on the resistance rate in our local community and to compare characteristics of macrolide resistant strains of Mycoplasma to look for any associated clinical parameters predicting resistance with implications in guiding treatment with antibiotics alternative to those in the macrolide group.