Pirkanmaa Hospital District, M building, Small auditorium, address: Teiskontie 35.
Doctoral defence of Lic.Med. Saara Sillanpää
The field of science of the dissertation is Otorhinolaryngology.
The opponent is professor Anne Pitkäranta (University of Helsinki). Professor Markus Rautiainen acts as the custos.
The language of the dissertation defence is Finnish.
Microbes causing acute otitis media in Finnish children
Acute otitis media is often a mixed infection caused by viruses and bacteria. Bacterial culture is the traditional method to detect bacteria causing acute otitis media, however, all bacteria do not grow very well in cultures. Bacteria can also be studied with sensitive DNA-based methods, such as PCR, in which the pathogens are targeted with specific primers. Next generation sequencing (NGS) is an unbiased method to detect all possible bacteria present in a clinical sample.
Acute otitis media caused by bacteria is recommended to be treated with antibiotics and the circulating bacteria can be modified i.e. with vaccinations. Therefore study on bacteria causing acute otitis media and their antibiotic resistance profile is important.
The dissertation study included children under 3.5 years from Tampere city region and pathogens causing acute otitis media were studied with traditional bacterial culture and modern DNA-based detection techniques (PCR and NGS). The resistance profile of cultivable pathogens was also characterised. In addition, the role of human parechoviruses in acute otitis media was studied.
For the first time an unbiased NGS technique was used in this study to detect bacterial pathogens in acute otitis media. Results showed that the three previously well-known bacteria, Streptococcus pneumoniae, Haemofilus influenzae and Moraxella catarrhalis cause most of the acute otitis media episodes and previously unknown bacterial pathogens were not detected. With NGS bacteria were found in 84%, with PCR in 77% and with culture in 45% of acute otitis media episodes. M. catarrhalis was the most common pathogen – with PCR it was detected in 47% of acute otitis media episodes. It was also common in multi-bacterial infections but often detected in only minute quantities in the samples. Human parechoviruses were found in only 4% of the episodes.
Non-susceptibility to one or more antibiotics was detected in 63% of the cultivated bacteria. Antibiotic resistance or diminished susceptibility was most common for erythromycin (35%), amoxicillin (28%), trimethoprim-sulfamethoxazole (23%) and for penicillin (7%). From a clinical point of view, the non-susceptibility of amoxicillin and trimethoprim-sulfamethoxazole is important, since these antibiotics are commonly used in the treatment of acute otitis media. In this study, the percentage of resistant bacteria was slightly increased when compared to results reported from earlier studies in Finland. However, multi-resistant or otherwise problematic bacteria were rare in the study.
The most important finding of this study was that the previously well-known S. pneumoniae, H. influenzae and M. catarrhalis are still the most common bacteria causing acute otitis media. New important bacteria or problematic multi-resistant bacteria were not detected. M. catarrhalis was the most common pathogen and often detected with other bacteria. For the clinician this is important information, since M. catarrhalis produces beta-lactamase and is therefore resistant to amoxicillin which is the nationally recommended first line antibiotic in the treatment of acute otitis media. When planning the optimal antibiotic therapy for acute otitis media, the results of this study should be kept in mind.
The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2302, Tampere University Press, Tampere 2017. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1806, Tampere University Press 2017.