Discussion
CAP is a frequent cause of admission and disease burden in children
worldwide and M. pneumoniae has been shown to be an important
causative agent. Macrolides are generally considered an effective first
choice antibacterial treatment for this condition. With a large
variation in resistance rates worldwide, it is of our interest to look
at the resistance rate of our local population of children comparably to
nearby regions.
According to our series of patients, the resistance rate is around 43%.
This is not as high as the 75% previously published group of patients
from 2010 to 2013, when Mycoplasma PCR and genotype testing for point
mutations were limited to selected ill patients not responding to first
line treatment. Our observed resistance rate is more representative of
the pattern in our local population as the sample size has increased,
and patients admitted with pneumonia were more readily tested for
Mycoplasma PCR and resistant strains.
Although the observed resistance rate is more representative of the
local population, there are several limitations of this study. The
sample population is limited to hospitalized patients with Mycoplasma
associated pneumonia, and to one regional hospital of Hong Kong. With
the diagnosis of CAP, the subsequent testing for atypical pathogens such
as M. pneumoniae was based on the attending doctor’s clinical
decision and suspicion. Therefore collaborating with other hospitals for
territory-wide and routine testing would produce more comprehensive
results and further accuracy in the local resistance rates with the
larger data samples. Another technical limitation in identifying
resistance strains is that all our patients were tested for specific
resistance genotype (A2063G) by real time PCR, the position relevant to
most cases of macrolide resistance since gene sequencing would be too
time consuming.
A number of prior studies have shown that it is not possible to predict
the presence of M. pneumoniae resistance solely on the basis of
presenting manifestations or routine laboratory investigations.
Similarly, chest radiography cannot be used to predict atypical
bacterial infection, limited in terms of sensitivity, specificity and
inter-observer variability. It is well known that a comprehensive
overview of world-wide resistance is hampered by the difficulty of
cultivating M. pneumoniae strains. Previously, serology remained
the only available means to confirm mycoplasma infection.
Currently, the use of molecular methods such as real-time PCR offers the
possible rapid identification of M. pneumoniae strains
independent of serological studies. Information on resistance can guide
appropriate treatment improving the clinical outcome, preventing
complications and improving the length of stay. Although informative,
genotype sequencing for identifying resistance is offered in selective
laboratories. Therefore , we aim to identify clinical parameters or
patient characteristics to guide the decision in optimizing and using
alternative antibiotic therapies.
Use of alternative antibiotics as tetracyclines and quinolones for the
treatment of Mycoplasma associated pneumonia have not been favoured
particularly in younger age groups of children due to their potential
bone growth suppression, teeth staining and enamel hypoplasia effects
during tooth development or cartilage erosion in some animal studies.
Our results have shown a clinical parameter facilitating early
recognition of likely MRMP to prompt earlier change in antibiotic
choice. Clinically and practically on a daily basis, the use of ‘72
hours non-defervescence’ can be used as a cut off tool to facilitate
recognition of likely MRMP and to support the clinical decision for
earlier change of antibiotic therapy during the course of admission.
Patients with MRMP treated with doxycycline achieved rapid defervescence
within 24 hours. This is valuable information to avoid development of
potential complications and shorten the length of stay. This could be
particularly useful in clinical decisions for younger groups of
patients, balancing the risks of the disease and treatment side effects
when considering the use of doxycycline.
Previous literature has mentioned that children with M.
pneumoniae treated with ineffective antibiotics have similar outcomes
to those observed in patients infected by susceptible strains. This may
indicate that mycoplasma pneumonia itself may be a self-limiting
disease. [14] This seems to indicate that there
may not be a need to change current macrolide use systematically in the
case of mild to moderate disease, but alternatives should be considered
if for persistent symptoms , clinical deterioration or evolving
complications. In our study, 4 patients with MRMP developed pleural
effusion. This suggests there may a difference in the rate of developing
complications in mycoplasma pneumonia, particularly if the strain is
macrolide resistant, as an ineffective antibiotic treatment may lead to
a prolonged clinical course.
According to our data, by 72 hours, 96% of MSMP patients achieved
defervescence.