Abstract
BackgroundFluoroquinolone-resistant Haemophilus influenzae (FRHI) has been reported worldwide but remain unclear in China.MethodsA total of 402 H. influenzae isolates collected from 2016 to 2017 were included. Antimicrobial susceptibility on 10 antibiotics was performed, and minimum inhibitory concentration of ciprofloxacin- and nalidixic acid-resistant strains were further determined by E-test strips, with risk factors also evaluated. Strains with resistance or reduced susceptibility to ciprofloxacin were subjected to sequencing of the quinolone resistance-determining regions (QRDR) and plasmid-mediated quinolone resistance genes by sequencing, with multi-locus sequence typing.Results2.2% of H. influenzae strains were non-susceptible (7/402, 1.7%) or susceptible (2/402, 0.5%) to ciprofloxacin but NAL-resistant by E-test, and multidrug resistance was more common in fluoroquinolones non-susceptible H. influenzae group (p = 0.000). Infection risk factors included invasive procedure (p = 0.011), catching cold/previous contact with someone who had a cold (p = 0.019), fluoroquinolones use during previous 3 months (p = 0.003). With none of mutations obtained in gyrB, parE and other plasmid-mediated quinolone resistance genes, 7 and 4 strains were found for Ser-84-Leu substitutions in gyrA and one amino acid substitution in the QRDR of gyrA linked with one amino acid substitution in the QRDR of parC, respectively. In addition, five sequence types (ST) were identified, with ST1719 firstly found.ConclusionsFor the first time, this study has reported the incidence, risk factors, molecular determinants on fluoroquinolones resistance and ST of FRHI strains in mainland China, representing the first evidence of mutation of gyrA and parC in China and the new ST1719 worldwide.
Highlights
Fluoroquinolone-resistant Haemophilus influenzae (FRHI) has been reported worldwide but remain unclear in China
The bacterial suspensions were heated to 100 °C in a boiling water bath for 10 min and centrifuged at 10,000×g for 10 min, DNA was used as template and amplified with the following polymerase chain reactions (PCR) procedure: denaturation at 95 °C for 5 min, followed by 30 cycles of 95 °C for 30 s, 55 °C for 30 s, and 72 °C for 90 s
Bacterial isolates As clinical data of the studied 402 nonduplicate H. influenzae strains was concerned, male patients accounted for 63.7% (n = 256), and 130 (32.3%), 110 (27.4%) and 162 (40.3%) patients were ≥ 60, 15–59 and < 15 years old, respectively
Summary
Fluoroquinolone-resistant Haemophilus influenzae (FRHI) has been reported worldwide but remain unclear in China. After the first report of FQs-resistant H. influenzae (FRHI) in 1993, this pathogen has spread worldwide and increased. In Taiwan, resistance rate of fluoroquinolone has increased rapidly over recent years [4, 7], and levofloxacin-resistance H. influenzae has been found to spread in the nursing home residents [7, 11] and was related to regional predominance of certain STs [4, 12]. Despite a regional cross-sectional study recently from Shanghai which reported an 8% H. influenzae carriage in healthy children (aged 12–18 months) and sensitivity to all tested antimicrobials except 12.2% ampicillin resistance to ampicillin (with none of FRHI found) [10], surveillance on FRHI still remains significantly limited in mainland China
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