Biofilm formation by Scottish clinical isolates of Staphylococcus aureus

Abstract

The biofilm-forming capacity of 972 clinical isolates of Staphylococcus aureus was tested using a high-throughput polystyrene 96-peg plate format. Isolates of S. aureus were collected from patients in hospitals throughout Scotland from 2004 to 2006; 763 of these were meticillinresistant S. aureus (MRSA) and 209 were meticillin-sensitive S. aureus (MSSA). The biomass of each biofilm was quantified using a crystal violet staining technique. Isolates were divided into those that formed fully established biofilms, moderately attached biofilms and weakly adherent biofilms by comparison with a known biofilm-forming strain. The majority of MRSA (53.8 %) and MSSA (43.5 %) isolates formed moderately attached biofilms. Fully established biofilms were formed by 20.5 % of MRSA isolates and 28.0 % of MSSA isolates, whilst 25.7 % of MRSA isolates and 28.5 % of MSSA isolates formed negligible biofilms. There was no significant correlation between susceptibility to meticillin and biofilm formation (P50.77). MRSA isolates were divided into clonal types (EMRSA-15, EMRSA-16 and sporadic isolates) based on PFGE genotyping results. EMRSA-15 isolates formed significantly more moderately and fully established biofilms than EMRSA-16 isolates (P,0.001). S. aureus strains isolated from the skin of patients had a significantly greater capacity to form biofilms than isolates from other body sites, including the blood. Microscopic examination of biofilms by scanning electron microscopy (SEM) revealed that poorly adherent biofilm formers failed to colonize the entire surface of the peg, whilst moderately adherent biofilm formers grew in uniform monolayers but failed to develop a mature three-dimensional structure. SEM analysis of an isolate representative of the group that formed fully established biofilms confirmed that this isolate developed a dense biofilm with a textured, multi-layered, three-dimensional structure.

Several Virulence Factors of Multidrug-Resistant Staphylococcus aureus Isolates From Hospitalized Patients in Tehran

“…In this study, methicillin resistant isolates harbored higher rate of icaADBC genes compared to MSSA, but no significant difference was confirmed, similar to two other studies (27,28). Moreover, Smith determined no significant relation between susceptibility to methicillin and biofilm formation (29). Likewise, Rasha detected the icaAD genes in 32% of blood and catheter isolates (37 (35).…”

Biofilm formation in invasive Staphylococcus aureus isolates is associated with the clonal lineage

“…(Kwon et al, 2008). Other studies showed no difference in biofilm formation between MRSA and MSSA isolates (Smith et al, 2008;Indrawattana et al, 2013). In our study there was also no difference in biofilm formation between MRSA and MSSA isolates, although the mean optical density for MSSA was higher.…”

“…Isolates from blood cultures showed a higher frequency of biofilm formation compared to isolates from other sites (Kwon et al, 2008). In the study by Smith et al, the isolates derived from skin had a greater ability to form fully established biofilms (Smith et al, 2008). In our study, the source of bacteraemia as established by clinical data for S. aureus blood-stream infections was not a predictor of biofilm formation.…”

“…Furthermore, the Brazilian clone (also MLST CC8) was shown to have increased adherence (Amaral et al, 2005). The EMRSA-15 clone in Scotland was found to form stronger biofilms than EMRSA-16 isolates (Smith et al, 2008).…”

Virulence Factors in Methicillin-Resistant <i>Staphylococcus aureus</i> Isolated from ICU Units in Brazil

“…There are few studies in the literature about the biofilm production of staphylococci isolates recovered from hospital environments. Smith et al [22] studied MRSA isolates from a hospital and found that 25.7% were low biofilm producers, 53.8% were moderate and 20.5% were biofilm producers. In the same study, compared to MSSA isolates, 28.5% were non-biofilm producers, 43.5% were moderate and 28.0% were biofilm producers.…”