DNA fingerprinting analysis of coagulase negative staphylococci implicated in catheter related bloodstream infections

Abstract

Aims: The epidemiological assessment of cases of coagulase negative staphylococcal catheter related bloodstream infection. Methods: Two hundred and thirty patients with suspected catheter related bloodstream infection were evaluated over a two year period. Central venous catheters were cultured both endoluminally and extraluminally. Peripheral blood, catheter hubs, skin entry, and skin control sites were also cultured. Pulsed field gel electrophoresis (PFGE) was used to DNA fingerprint coagulase negative staphylococci isolated from patients with presumptive catheter related bloodstream infection. Results: Sixty cases of catheter related bloodstream infection were identified, 21 of which were attributed to coagulase negative staphylococci. Two hundred and ninety four separate isolates of coagulase negative staphylococci from the 21 cases of catheter related bloodstream infection were subjected to PFGE (mean of 14 for each case). Catheter related bloodstream infection was only confirmed by PFGE analysis in 16 of the 21 cases because in the remaining five cases peripheral blood and central venous catheter coagulase negative staphylococci isolates were different. Skin entry, control skin, and central venous catheter hub isolates matched peripheral blood isolates in six, four, and seven cases, respectively. Coagulase negative staphylococci isolates could not be cultured from the patients' own skin in seven cases of catheter related bloodstream infection. Central venous catheter lumens were colonised in all cases of catheter related bloodstream infection compared with 44-81% of cases that had positive external surface catheter tip cultures, depending on the threshold used to define significant growth. Conclusions: Catheter related bloodstream infection as a result of coagulase negative staphylococci may be over stated in about a quarter of cases, unless a discriminatory technique is used to fingerprint isolates. No single, simplistic route of bacterial contamination of central venous catheters was identified, but endoluminal catheter colonisation is invariably present in cases of catheter related bloodstream infection.

Central venous catheter-related bloodstream infection caused by Staphylococcus aureus: microbiology and risk factors

“…More recent studies confirm these findings [28,35]. In our investigation, CoNs frequently colonized the tip was (60%), while S. aureus was found in 30%; in the blood we saw a higher percentage of S. aureus (38%).…”

Comparison of Phenotypic with Genotypic Procedures for Confirmation of Coagulase-Negative Staphylococcus Catheter-Related Bloodstream Infections

“…Another difficulty in phenotypic microbiological characterization of CNS CR-BSI is the differentiation of morphotypes after incubation periods shorter than 48 h. Different morphotypes are frequently observed after only 72 h of incubation and frequently reflect differences at the genotypic level (11,12,17,23,25,29,33). The possibility of a sampling error in phenotypic diagnosis when a single colony of the culture is being studied may be high (24).…”

“…The correlation between species identification, even including biotypes with typing characterization by genotypic methods (e.g., PFGE), is largely imprecise (15). At the same time, the determination of the sensitivity pattern as a typing method is also inaccurate (13,17,22,23,31).Another difficulty in phenotypic microbiological characterization of CNS CR-BSI is the differentiation of morphotypes after incubation periods shorter than 48 h. Different morphotypes are frequently observed after only 72 h of incubation and frequently reflect differences at the genotypic level (11,12,17,23,25,29,33). The possibility of a sampling error in phenotypic diagnosis when a single colony of the culture is being studied may be high (24).…”

Guidelines for the Prevention of Intravascular Catheter-related Infections: Recommendations Relevant to Interventional Radiology for Venous Catheter Placement and Maintenance

“…There are four recognized routes for contamination of catheters: 1) migration of skin organisms at the insertion site into the cutaneous catheter tract and along the surface of the catheter with colonization of the catheter tip (the most common route of infection for short-term catheters) (17–19); 2) direct contamination of the catheter or catheter hub by contact with hands or contaminated fluids or devices (20, 21); 3) hematogenous seeding from another focus of infection (less common) (22); and 4) infusate contamination (rare) (23). …”