9 research outputs found
DNA fingerprinting analysis of coagulase negative staphylococci implicated in catheter related bloodstream infections
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.
The use of central venous catheters as a means of access for
monitoring and as a route of administration of drugs has
become almost mandatory in patients with serious
illnesses. Infections of central venous catheters are common
and coagulase negative staphylococci remain the most
frequent pathogens—for example, 37% of 1267 isolates in one
meta-analysis.Controversy remains over the source of, and
route of access by, these bacteria to the central venous
catheters. Recent developments, such as catheters with
antimicrobial properties, are an important advance,
but
until such issues are resolved it remains unclear how best to
reduce the risk of catheter related bloodstream infection.
“Pulsed field gel electrophoresis is well recognised as the
gold standard for fingerprinting coagulase negative staphylococci”
Because there are at least 33 distinct coagulase negative
staphylococci species that have been identified, and because
methods that use phenotyping alone cannot accurately
distinguish between strains of coagulase negative staphylococci,
DNA fingerprinting is required to clarify the epidemiology
of coagulase negative staphylococci catheter related bacterial
bloodstream infection. Despite the accepted difficulties in
determining the relatedness of coagulase negative staphylococci,
diagnostic laboratories routinely rely on limited
information from phenotypic tests to compare isolates fro