Number of positive blood cultures, biofilm formation, and adhesin genes in differentiating true coagulase-negative staphylococci bacteremia from contamination

Abstract

The significance of the number of coagulase-negative staphylococci (CNS)-positive blood cultures remains obscure in regards to determining true bacteremia versus contamination. The goal of this study was to determine the predictors of real CNS bloodstream infection among intensive care unit (ICU) patients. ICU patients with at least one CNS-positive blood culture were identified from the microbiology database. Biofilm formation was tested by glass tube and microtiter plate assay. mecA gene, ica operon genes (icaA, icaB, icaD), and adhesin genes (aap, bap, atlE, fbe, fnbA) were detected by polymerase chain reaction (PCR). CNS were recovered from 120 septic episodes, 20 of which were true CNS bacteremias, whereas from the remaining 100 episodes, the isolated CNS were characterized as contaminants. The number of positive blood cultures was significantly associated with true CNS bacteremia. Nineteen true bacteremic Staphylococcus epidermidis strains were compared to 38 contaminants. Biofilm synthesis was documented in 37 isolates associated with the presence of the ica operon (p = 0.048). There were 39, 26, 38, 21, and 10 strains positive for the presence of atlE, bap, fbe, aap, and fnbA genes, respectively. Rifampicin resistance, absence of severe sepsis, number of S. epidermidis-positive blood cultures, and absence of the bap gene were independently associated with true S. epidermidis bacteremia as compared to contaminant strains. The number of positive blood cultures is associated with true CNS bacteremia. The presence of adhesin genes may play a role in differentiating true infection from contamination, whereas absence of the bap gene is associated with true S. epidermidis bacteremia.

Gut Dysbiosis With Bacilli Dominance and Accumulation of Fermentation Products Precedes Late-onset Sepsis in Preterm Infants

“…To overcome the risk of contaminations, we only counted CoNS infection as "true", when infants additionally had clinical signs of infection and an elevated laboratory marker [42].…”

Virulence Factors in Coagulase-Negative Staphylococci

“…Based on several studies, it was observed that commensal strains seem to be more susceptible to antibiotics [496], often positive to the genes aap and fdh and the ACME element [154,[496][497][498] and repeatedly negative to the biofilm-associated genes icaA and bhp and the IS256 [499,500]. In the case of clinical isolates, it has been often linked to higher antibiotic resistance and the presence of the genes icaA and bhp, as well as the carriage of the IS256 and SCCmec elements [496][497][498][501][502][503].…”

The Epidemiology of Bloodstream Infections and Antimicrobial Susceptibility Patterns: A Nine-Year Retrospective Study at St. Dominic Hospital, Akwatia, Ghana

“…These microorganisms may include Gram-negative bacteria such as Escherichia coli , Pseudomonas aeruginosa , Klebsiella species , Neisseria meningitidis , and Haemophilus influenzae , and Gram-positive bacteria such as coagulase-negative staphylococci (CoNS), Staphylococcus aureus , Streptococcus pneumoniae , Streptococcus pyogenes , Streptococcus agalactiae , and Enterococcus faecium [12]. The incidence of bloodstream infection is attributed to ageing of patients on admission, increasing number of patients with compromised immunity, and the acquisition of virulence factors by bloodstream pathogens [13, 14] as well as factors linked to infection prevention and control measures and implementation [15]. Bloodstream infections can be categorized into three groups based on its mode of occurrence: in immunocompetent host with intact defenses, in patients at the extremes of life, and in patients affected by pathological conditions putting them at risk to the infections [11].…”