Characterisation of a collection of Streptococcus pneumoniae isolates from patients suffering from acute exacerbations of chronic bronchitis: In vitro susceptibility to antibiotics and biofilm formation in relation to antibiotic efflux and serotypes/serogroups

Abstract

a b s t r a c tThe correlation between Streptococcus pneumoniae serotypes, biofilm production, antibiotic susceptibility and drug efflux in isolates from patients suffering from acute exacerbations of chronic bronchitis (AECB) remains largely unexplored. Using 101 isolates collected from AECB patients for whom partial (n = 51) or full (n = 50) medical details were available, we determined serotypes (ST)/serogroups (SG) (Quellung reaction), antibiotic susceptibility patterns [MIC (microdilution) using EUCAST and CLSI criteria] and ability to produce biofilm in vitro (10-day model; crystal violet staining). The majority of patients were 55-75 years old and <5% were vaccinated against S. pneumoniae. Moreover, 54% showed high severity scores (GOLD 3-4), and comorbidities were frequent including hypertension (60%), cancer (24%) and diabetes (20%). Alcohol and/or tobacco dependence was >30%. Isolates of SG6-11-15-23, known for large biofilm production and causing chronic infections, were the most prevalent (>15% each), but other isolates also produced biofilm (SG9-18-22-27 and ST8-20 being most productive), except SG7, SG29 and ST5 (<2% of isolates each). Resistance (EUCAST breakpoints) was 8-13% for amoxicillin and cefuroxime, 35-39% for macrolides, 2-8% for fluoroquinolones and 2% for telithromycin. ST19A isolates showed resistance to all antibiotics, ST14 to all except moxifloxacin, and SG9 and SG19 to all except telithromycin, moxifloxacin and ceftriaxone (SG19 only). Solithromycin and telithromycin MICs were similar. No correlation was observed between biofilm production and MIC or efflux (macrolides, fluoroquinolones). S. pneumoniae serotyping may improve AECB treatment by avoiding antibiotics with predictable low activity, but it is not predictive of biofilm production.

Characterization of Streptococcus pneumoniae clones from paediatric patients with cystic fibrosis

“…In this regard, the serotypes we tested might differ for biofilm amount and architecture under different experimental settings, as observed previously by Allegrucci et al (2006) using a continuous-flow biofilm reactor system. Similarly to Vandevelde et al (2014), no significant correlation was also seen between biofilm amount and susceptibility to antibiotics among the isolates investigated. Further studies focusing on these topics are needed to understand better the role of biofilm formation in pneumococcal pathogenicity.…”

Clinical Relevance and Molecular Pathogenesis of the Emerging Serotypes 22F and 33F of Streptococcus pneumoniae in Spain

“…Biofilm formation is a critical aspect from the pathogenesis perspective because S. pneumoniae has been reported to form biofilms in the upper respiratory tract (Wu et al, 2017;Iverson et al, 2019;Silva and Sillankorva, 2019) and nasopharyngeal colonization is the initial step in this process and the prerequisite for developing IPD (Bogaert et al, 2004). Interestingly, active infection is also associated to pneumococcal biofilms in meningitis by binding to brain microvascular endothelial cells and in persistent respiratory infection affecting patients with cystic fibrosis or chronic obstructive pulmonary disease (COPD) (Orihuela et al, 2009;Vidal et al, 2013;Vandevelde et al, 2014;Dennis et al, 2018). In the biofilm state, pneumococcal cells express the PspC protein in a higher extent, and this protein is the bacterial ligand associated to the recruitment of factor H and therefore to the cleavage of the C3 complement system protein deposited on the bacterial surface (Domenech et al, 2013).…”

Biofilm Formation Under In Vitro Conditions

“…The observed reduction of biomass was even lower, ranging from 50% on young biofilms to 20% or less on old biofilms [45]. In follow-up work, the same group, working on a large strain collection, found that there was no correlation between biofilm formation and intrinsic susceptibility or expression of resistance determinants in pneumococci [46]. Interestingly, this work compiled a table with the activities of the antibiotics on biofilms at concentrations found in epithelial lining fluid with the specific aim of providing indications for the clinical relevance of the pharmacodynamic data obtained [45].…”