Antimicrobial Effect of Fluoroquinolones for the Eradication of Nontypeable Haemophilus Influenzae Isolates within Biofilms

Abstract

Biofi lms can be defi ned as communities of microorganisms attached to a surface. Those bacterial biofi lms cause serious problems, such as antibiotic resistance and medical devicerelated infections. Nontypeable Haemophilus infl uenzae (NTHi) is an important pathogen in respiratory infections, as it forms biofi lms both in vitro and in vivo such as human middle ear. Recent reports indicate that otitis media, paranasal sinusitis and lower respiratory tract infections caused by Haemophilus infl uenzae have become more diffi cult to treat with oral antibiotic therapy. However, there has been no attention given to antibiotic eradication of NTHi biofi lm. To investigate the antimicrobial effect of various antibiotics against NTHi biofi lm formation, we conducted the following comparative study using both β -lactamase-negative ampicillin (AMP)-susceptible (BLNAS) and AMP-resistant (BLNAR) NTHi strains. In a microtiter biofi lm assay, both levofl oxacin and gatifl oxacin, of the fl uoroquinolone antibiotic group, signifi cantly inhibited biofi lm formation by BLNAS and BLNAR NTHi in a dose-dependent fashion compared to ampicillin of the penicillin antibiotic group, cefotaxime of the cephalosporin antibiotic group, and both erythromycin and clarithromycin of the macrolide antibiotic group. Furthermore, in fl ow cell chamber studies, confocal laser scanning microscopy counted survival bacteria in mature biofi lm had been treated with gatifl oxacin, ampicillin, cefotaxime and erythromycin. Only gatifl oxacin completely killed the BLNAR NTHi isolates within biofi lms without regard to the thickness of biofi lm formation. The results of this study suggest that fl uoroquinolones potentially have a role in therapy against diseases caused by both BLNAS and BLNAR NTHi isolates within biofi lms.

Improvement Rate of Acute Otitis Media Caused by Haemophilus influenzae at 1 Week Is Significantly Associated with Time to Recovery

“…A biofilm is a structured community of bacteria enveloped in a self-produced extrapolymeric matrix that adheres to a surface, and biofilm production is a common cause of persistent and chronic bacterial infections (4). Recently, Torretta et al investigated nasopharyngeal biofilm-producing pathogens in children with a history of recurrent mild/moderate AOM.…”

“…Biofilm formation by all H. influenzae isolates was assessed using 96-well microplates as described previously (4). The culture medium containing planktonic cells was stained with 1% crystal violet at room temperature.…”

“…We previously reported that Haemophilus influenzae can form a biofilm both in vitro (3) and in vivo (4). Bacterial biofilms are recognized as having an important role in various human infections, and the bacteria in a biofilm are more resistant to antibiotic therapy than are planktonic microorganisms, suggesting that biofilms might play an important role in the pathogenesis and chronicity of otitis media (3).…”

Biofilms in pediatric respiratory and related infections

“…In vitro, fl uoroquinolones have been shown to be more effective against OM from nontypeable H. infl uenzae than β-lactams, cephalosporin, and macrolides [57]; however, in vivo data are lacking. Subinhibitory concentrations of macrolide clarithromycin inhibit biofi lm formation by interfering with the twitching mobility of P. aeruginosa [58].…”

Innate Immunity and the Role of Defensins in Otitis Media

“…In cases of chronic OM and recurrent acute OM, biofilms containing SP, NTHI, coagulase-negative staphylococci, or Staphylococcus aureus appear to be common [11]. Biofilm formation may protect the bacteria from the adaptive and innate immune systems of the host and increase resistance to some antibiotics up to 1,000-fold [12]. Pseudomonas aeruginosa is not a common pathogen in acute OM but is the most common organism isolated in chronic suppurative otitis and in cholesteatomatous otitis [13, 14•, 15].…”