Colonisation of fluoroquinolone-resistant Haemophilus influenzae among nursing home residents in southern Taiwan.

ABSTRACT

Fluoroquinolones have been widely used to treat respiratory tract infections, but fluoroquinolone resistance in Haemophilus influenzae has remained rare. In 2007, prospective surveillance cultures of throat swabs and sputum were conducted every two months on 150 residents of four nursing homes in southern Taiwan. Forty-eight H. influenzae isolates were obtained from 30 (20%) residents. All isolates were non-b serotype and 27 (56.3%) possessed beta-lactamases. Resistance to levofloxacin [minimum inhibitory concentration (MIC) >2 microg/mL] and moxifloxacin (MIC >1 microg/mL) was found in 20 (41.7%) and 21 (43.8%) isolates, respectively. High level levofloxacin and moxifloxacin resistance (MIC >32 microg/mL) was detected in 19 (39.6%) and 15 (31.3%) isolates, respectively. Among 150 residents, those with urinary catheterisation (P=0.018) and tracheostomy tubes (P=0.029) were independently associated with airway colonisation by moxifloxacin-resistant H. influenzae. Among 30 residents with carriage of H. influenzae, no factor was significantly associated with moxifloxacin resistance. Pulsed-field gel electrophoresis of the isolates revealed 14 distinct types. Two major clones accounted for 29 isolates, 27 of which were obtained from 13 residents in one nursing home. All but two of the fluoroquinolone-resistant isolates belonged to these two major clones. This study highlights the emergence of fluoroquinolone-resistant H. influenzae and its clonal spread among nursing home residents in southern Taiwan. Further studies on clinical implications and the extent of fluoroquinolone non-susceptibility and resistance are needed.