Assessment of biofilm‐forming ability of coagulase‐negative staphylococci isolated from contaminated platelet preparations in Canada

Abstract

BACKGROUND: Coagulase-negative staphylococci (CoNS) are the most prevalent bacterial contaminants of platelet (PLT) preparations and have been implicated in adverse transfusion reactions worldwide. The most frequently identified contaminant is Staphylococcus epidermidis, which is noted for its ability to maintain chronic hospital-acquired infections by forming biofilms as a chief virulence mechanism. STUDY DESIGN AND METHODS: Strains of S. epidermidis isolated from contaminated PLT preparations in Canada were distinguished via gene-specific polymerase chain reaction (PCR) with divIVA as a marker. Biofilm-forming ability was assessed by the presence of the gene icaD, slime production on Congo red agar, and biofilm formation on polystyrene surfaces. Production of polysaccharide intercellular adhesin (PIA) was resolved by immunofluorescence. RESULTS: Eight of the 13 (62%) CoNS isolates under study were identified as S. epidermidis. Of these, four strains (50%) were classified as strong biofilm producers. Three of the four biofilm-positive strains (75%) produced slime, harbored the icaD gene, and had positive expression of PIA. CONCLUSIONS: Despite the presumable commensal origin of the CoNS isolates, a large proportion of S. epidermidis strains demonstrated a potential for enhanced virulence. Identification of contaminant staphylococci as biofilm producers is thus relevant and informative with regard to treatment approach in the circumstance of inadvertent infection of a PLT recipient. ABBREVIATIONS: ATCC = American Type Culture Collection; ATR(s) = adverse transfusion reaction(s); CoNS = coagulasenegative staphylococci; PIA = polysaccharide intercellular adhesin; TSB(g) = trypticase soy broth (+0.5% glucose). TRANSFUSION 2008;48:969-977. Volume 48, May 2008 TRANSFUSION 969 * Percent confidence of species identification from initial test with the API Staph database (bioMérieux, Marcy L'Etoile, France). † Reidentified as S. epidermidis based on the presence of divIVA and ribotyping analysis. BC = whole blood-derived PLTs prepared by the buffy-coat method; Aph = single-donor apheresis PLTs; PRP = whole blood-derived PLTs prepared by the PLT-rich plasma method; ND = not determined. GRECO ET AL. 970 TRANSFUSION Volume 48, May 2008 Fig. 4. Production of PIA by PLT contaminant isolates. Indirect immunofluorescence was performed with primary antibody a-PIA and FITC-conjugated secondary antibody. S. epidermidis ATCC 35984 (A, B) and ATCC 12228 (C, D) were included as biofilm-positive and biofilm-negative controls, respectively. Contaminant strains that were positive for PIA production are

Bacterial culture of apheresis platelets: a mathematical model of the residual rate of contamination based on unconfirmed positive results

“…Greco et al . show that some platelet contaminants are able to rapidly adhere to surfaces and form mattes of biological material that entrap bacteria, preventing detection by BacT/ALERT™ sampling and posing a risk should these bacteria proliferate and subsequently be released into suspension . In our protocol, platelet collections are well mixed before sampling, but the efficiency of this process in dislodging adherent bacteria is unknown.…”

“…Low concentrations of bacteria at the time of sampling may be caused by a prolonged lag phase (i.e. dormant bacteria), slow log phase growth or the presence of adherent biofilms that reduce the number of bacteria in solution available for sampling . US blood centres wait 24–36 h after collecting the platelet donation to allow bacteria to enter the log phase of growth and to reach sufficient concentrations to allow detection .…”

Clinical implications of icaA and icaD genes in coagulase negative staphylococci and Staphylococcus aureus bacteremia in febrile neutropenic pediatric cancer patients

“…In addition, other possible sources of CoNS infection have to be taken into consideration. One recent study identified platelet preparation as a source of ica‐positive CoNS isolates which were strong biofilm producers 19.…”

Enhanced pathogenicity of biofilm‐negative Staphylococcus epidermidis isolated from platelet preparations

“…An OD 492 of not more than 0.1 is considered to be biofilm negative as established using the negative control strain S. epidermidis ATCC 12228 in TSBg (Fig. ) . Significant differences were found when biofilm‐positive strains ATCC 35984 and 9142 were compared to the biofilm‐negative control ATCC 12228 strain in TSBg (p < 0.05).…”

“…Transfusions with fatal outcomes due to PCs contaminated with S. epidermidis have been reported in Canada, the United States, and Europe . Missed detection of S. epidermidis during routine PLT screening is attributed to low initial concentration, characteristic slow growth under PLT storage conditions, and ability to form bacterial aggregates attached to the PLT containers known as biofilms …”