Nasopharyngeal carriage of Haemophilus influenzae among adults with co-morbidities

Maria Giufrè; Maria Dorrucci; Alessandra Lo Presti; Francesca Farchi; Rita Cardines; Romina Camilli; Fernanda Pimentel de Araujo; Fabiola Mancini; Alessandra Ciervo; Maria Corongiu; Annalisa Pantosti; Marina Cerquetti; Catia Valdarchi; FIMMG Group

doi:10.1016/j.vaccine.2021.12.030

Nasopharyngeal carriage of Haemophilus influenzae among adults with co-morbidities

Vaccine. 2022 Jan 31;40(5):826-832. doi: 10.1016/j.vaccine.2021.12.030. Epub 2021 Dec 21.

Affiliations

¹ Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy. Electronic address: maria.giufre@iss.it.
² Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
³ Italian Federation of General Practitioners (Federazione Italiana Medici di Medicina Generale, FIMMG), Rome, Italy.
⁴ Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy; Italian Federation of General Practitioners (Federazione Italiana Medici di Medicina Generale, FIMMG), Rome, Italy.

PMID: 34952754
DOI: 10.1016/j.vaccine.2021.12.030

Abstract

After the widespread use of Haemophilus influenzae type b (Hib) vaccine, H. influenzae invasive disease is now commonly due to non-encapsulated (NTHi), affecting mostly the youngest and the elderly. The objective of this study was to investigate H. influenzae nasopharyngeal carriage rate in adults with co-morbidities and possible associated risk factors.

Methods: Patients aged >50 years with co-morbidities attending medical centres were examined. A nasopharyngeal swab was analysed for H. influenzae presence by cultural and molecular methods (RT-PCR). Univariable and multivariable analysis of risk factors for H. influenzae carriage were performed. Serotype of isolates was determined by PCR capsular genotyping. Minimum inhibitory concentration (MIC) was determined by MIC gradient test and β-lactamase production was detected by the nitrocephin test. Genotyping was performed by Multilocus sequence typing (MLST). Phylogenetic relationships among carriage and invasive NTHi strains were assessed.

Results: Among 248 enrolled patients (median age: 73 years), the carriage rate was 5.6% and 10.5% by cultural method or RT-PCR, respectively. Colonization with H. influenzae was significantly associated with the presence of acute respiratory symptoms (adjusted OR = 12.16, 95% CI: 3.05-48.58, p < 0.001). All colonizing isolates were NTHi. Three isolates (3/14, 21.4%) were resistant to ampicillin and beta-lactamase positive. MLST revealed a high degree of genetic diversity, with 11 different STs from 14 isolates. Eight out of the 11 (72.7%) STs were shared among carriage and invasive isolates.

Conclusions: Adults ≥50 years old with co-morbidities are occasionally colonized by H. influenzae, even if the presence of co-morbidities is not a risk factor for colonization. The presence of acute respiratory symptoms is the only factor associated with H. influenzae colonization. Colonizing H. influenzae are all NTHi. Colonizing H. influenzae often belong to the same STs of invasive disease isolates.

Keywords: Ampicillin; Carriage; Elderly; Haemophilus influenzae; MLST.

MeSH terms

Adult
Aged
Haemophilus Infections* / epidemiology
Haemophilus influenzae* / genetics
Humans
Infant
Middle Aged
Morbidity
Multilocus Sequence Typing
Nasopharynx
Phylogeny