Haemophilus influenzae invasive disease in Portugal, 2017-2018 - what have been changing after Hib vaccine implementation?

Bettencourt, Célia; Bajanca Lavado, Maria Paula; The Portuguese Group for the “Study of Haemophilus influenzae invasive infection”

http://hdl.handle.net/10400.18/6788

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Authors

Bettencourt, Célia

Bajanca Lavado, Maria Paula

The Portuguese Group for the “Study of Haemophilus influenzae invasive infection”

Abstract(s)

Introduction and Aims: Haemophilus influenzae is a frequent colonizer of the upper airways that can easily spread through respiratory tract leading to invasive infections in both children and adults. H. influenzae serotype b (Hib) has been prevented by vaccination, in Portugal, since 2000, but the emergence of non-typeable isolates (NTHi), as well as non-b serotypes responsible for invasive disease have been documented.1,2 We aim to characterize H. influenzae invasive isolates recovered in Portugal, during the last two years and compare results from previous studies. 1,2 Materials and Methods: As part of a laboratory-based surveillance system, 108 invasive H. influenzae were received at the National Reference Laboratory for Haemophilus influenzae for characterization. Capsular status was identified by PCR with primers and conditions described in the literature.3 Antibiotic susceptibility was determined by microdilution, according to EUCAST guidelines. 4 β-lactamase production was assessed with nitrocefin. Genetic relatedness among the isolates was examined by MLST as previously described.5 Sequences were analysed and submitted to the MLST website (https://pubmlst.org/hinfluenzae/) for assignment of the sequence type (ST). goeBURST analysis was performed using the PHYLOViZ platform.6 Results: Among 108 H. influenzae isolates, 90% were from blood, and 66% were from adults. Serotyping revealed that 74% were NTHi (80/108) and 26% (28/108) were capsulated isolates. Among capsulated isolates, 10.7% were Hia, 60.7% Hib, 10.7% Hie and 7.1% Hif. Most of the isolates were susceptible to the antibiotics studied, with the exception of 12.9% (14/108) ampicillin resistant by β-lactamase producing and 9.6% (9/94) that correlates with BLNAR phenotype (MIC≥1 to ampicillin and co-amoxiclave). MLST profiles revealed, as expected, high genetic variability (74.1%), with 23 different STs among 31 NTHi isolates tested. In opposition, encapsulated isolates were clonal with all Hia assigned to CC23, Hib assigned to CC6, (ST6 and ST1231), Hie to CC18, and Hif to CC124. Conclusion: After vaccine implementation and the great decline observed in Hib invasive disease (from 81% in 1989-2001 to 13% in 2002-2010),1,2 we are now concerned about Hib isolates (16%) that still in circulation in our country, affecting mostly children (88%), and accounting for 47% of vaccine failures. In addition, Hia increased, from 2% in the last period of five years (2012-2016) to 3% in this two years period (2017-2018), with all isolates from infants, up to two years old. It is important to continue the surveillance of H. influenzae invasive disease to monitor the true magnitude of these problems and develop public health prevention strategies.