Blood culture contamination: having your cake and eating it
Post on 05-Sep-2016
sequencers using primers homologous to those used for the PCR
Hoscreening (Sequiserve, Vaterstetten, Germany). Plasmid profileanalysis was performed using an alkaline lysis method aspreviously described.1 Pulsed-field gel electrophoresis (PFGE)was performed following enzymatic restriction of genomic DNAusing XbaI restriction endonuclease (Roche, Basel, Switzerland)according to the standardized PulseNet protocol.6
Based on CLSI susceptibility breakpoints, both isolates hadmultidrug-resistant phenotypes including non-susceptibility tomost b-lactams, aminoglycosides, ciprofloxacin and trimetho-primesulfamethoxazole. PCR and sequencing confirmed thepresence of the ESBL blaCTx-M-15 along with narrow-spectrumb-lactamases blaTEM-1 and blaOxA-1 in both isolates, respec-tively. Both isolates carried identical numbers and sizes ofplasmids (Table I). The isolates were indistinguishable on PFGEby both enzymes.
Healthcare workers, like patients, can be at increased risk ofacquisition of multidrug-resistant organisms such as ESBL-producing Gram-negative bacteria. To our knowledge, few, ifany, centres provide specific guidelines pertaining to empiricaltreatment of severe infections for their local healthcareworkers in the event of hospitalization. The local resistancepatterns of pathogens in individual centres may inform thenecessity of such a guideline.
Transmission of ESBL-producing Enterobacteriaceae frompatients to household members is well described, with carriagerates in household contacts ranging from 23.8% to 50.3%.3 Mostof the household contacts who acquired ESBL-producingorganisms were colonized asymptomatically. As also reportedin the case above, serious infections can occasionally developin some of the contacts.2
We highlight the potential for occupational risk of acquisitionof ESBL-producing Enterobacteriaceae in healthcare workers, thepossibility of cross-transmission to household contacts, and thepotential therapeutic implications for treating serious infectionsin suchpersons.This also servesasa reminderof the importanceofinfection prevention and control measures such as hand hygieneand aseptic techniques in minimizing such risks. A more compre-hensive study is required to assess accurately the level of occu-pational risk to healthcare workers in the acquisition and onwardtransmission to household contacts of ESBL-producing organisms.
Conflict of interestNone declared.
1. Boyle F, Morris D, OConnor J, et al. First report of extended-spectrum-beta-lactamase-producing Salmonella enterica serovarKentucky isolated from poultry in Ireland. Antimicrob AgentsChemother 2010;54:551e553.that of her husbands isolate (Table I). She made an uneventfulrecovery following 14 days of treatment with meropenem.
Polymerase chain reaction (PCR) screening of both isolates forblaTEM, blaSHV, blaCTx-M and blaOxA was performed using specificprimers and protocols as reported previously.4,5 Sequencing ofamplicons was performed in both directions on ABI3730 capillary
Letters to the Editor / Journal of2. Ender PT, Gajanana D, Johnston B, et al. Transmission of anextended-spectrum-beta-lactamase-producing Escherichia coli(sequence type ST131) strain between a father and daughterresulting in septic shock and emphysematous pyelonephritis. J ClinMicrobiol 2009;47:3780e3782.
3. Lo WU, Ho PL, Chow KH, et al. Fecal carriage of CTXM typeextended-spectrum beta-lactamase-producing organisms bychildren and their household contacts. J Infect 2010;60:286e292.
4. Lee S, Park YJ, Kim M, et al. Prevalence of Ambler class A and Dbeta-lactamases among clinical isolates of Pseudomonas aerugi-nosa in Korea. J Antimicrob Chemother 2005;56:122e127.
5. Woodford N, Fagan EJ, Ellington MJ. Multiplex PCR for rapiddetection of genes encoding CTX-M extended-spectrum (beta)-lactamases. J Antimicrob Chemother 2006;57:154e155.
6. Swaminathan B, Barrett TJ, Hunter SB, et al. PulseNet: themolecular subtyping network for foodborne bacterial diseasesurveillance, United States. Emerg Infect Dis 2001;7:382e389.
M. Cottera,*F. Boyleb
B. OConnellaaDepartment of Clinical Microbiology, St Jamess Hospital,
bDepartment of Bacteriology, National University of IrelandGalway, Galway, Ireland
* Corresponding author. Address: Department of ClinicalMicrobiology, Mater Misericordiae University Hospital,
Eccles Street, Dublin 7, Ireland.Tel.:353 87 9684002; fax: 353 1 8034781.
E-mail address: email@example.com (M. Cotter).
Accepted by J.A. ChildAvailable online 25 November 2011
2011 The Healthcare Infection Society. Published by Elsevier Ltd.All rights reserved.doi:10.1016/j.jhin.2011.10.007
Blood culture contamination: having yourcake and eating it
Thomas et al. saw a decrease in blood culture contaminantsfollowing introduction of a collection kit, but noted a fall in thenumber of both blood culture sets received and Gram-negativebacteraemias detected.1 We too brought in measures in autumn2007 to reduce blood culture contaminants, but our experiencehas been rather different. Like Thomas et al., we introduceda blood culture collection kit, consisting of the bottles, a Safety-Lok blood collection set with pre-attached holder (BectonDickinson, Franklin Lakes, NJ, USA), a detailed guidance leafletwith photographs, and disposable disinfection wipe with 2%chlorhexidine in 70% isopropyl alcohol (PDI, Flint, UK). TheSafety-Lok blood collection set with pre-attached holder whenused with the BACTEC blood culture sets (Becton Dickinson,Sparks, MD, USA) negates the requirement to fill a syringe, attachaneedle, and inoculate thebottles.Wealso produced a video and
spital Infection 80 (2012) 92e102 101trained phlebotomists to train and continually educate clinical
t or s
Sets with significant isolates Sets wiLinear Linear (Sets with significant isolates)
Letters to the Editor / Journal of102staff in blood culture techniques, particularly junior hospitaldoctors. Where circumstances allow, clinical staff are encour-aged to use phlebotomists to take blood cultures. All Staphylo-coccus aureus bacteraemias are subject to a root cause analysisand any staff member found to be responsible for sucha contaminant bacteraemia is subject to interview by a panel ofsenior medical staff. Blood culture contamination rates are fedback to each clinical directorate each three months.
Figure 1 shows that the number of blood culture setshas steadily increased over the last three years, as hasthe number of significant bacteraemias (those assessed as notbeing due to contaminants at contemporaneous and subsequentreview by a consultant microbiologist). Blood culture contami-nants have decreased over the same period, both in terms ofabsolute numbers and in set contamination rate, from anaverage of 6% of sets received prior to the introduction of theinterventions to an average of 2.7% in the current calendar year.From October 2007 to January 2010, all phlebotomist-takenblood cultures were marked as such, allowing us to comparecontamination rates with non-phlebotomist-taken specimens.Over that period, phlebotomist-taken cultures had a contami-nation rate of 0.8%, and non-phlebotomist-taken cultures 4.3%.Although part of this difference may be explained bydoctors taking relatively more cultures from restless andnon-cooperativepatients, this is strongly suggestive that a small,highly trained, motivated and monitored team, perhaps underless time pressure, can achieve very low rates of contamination.
A package of measures taken to reduce blood culturecontamination can be successful while the overall number ofspecimens taken is rising.
Figure 1. Numbers of blood cultures received each quarter from Januisolates, and sets yielding contaminants. Trend lines (dashed) are sho1200
ontaminants Sets receivedLinear (Sets received)ts with contaminants)
spital Infection 80 (2012) 92e102Conflict of interest statementNone.
1. Thomas S, Cheesbrough J, Plumb S, et al. Impact of a blood culturecollection kit on the quality of blood culture sampling: fear and thelaw of unintended consequences. J Hosp Infect 2011;78:256e259.
N.C. Weightman*K.G. Kerr
Department of Microbiology, Harrogate and District NHSFoundation Trust, Harrogate, UK
* Corresponding author. Address: Department of Microbiology,Harrogate and District NHS Foundation Trust, Lancaster Park
Road, Harrogate HG2 7SX, UK.Tel.: 44 1423 555663; fax: 44 1423 555673.E-mail address: firstname.lastname@example.org
Accepted by J.A. ChildAvailable online 25 November 2011
2011 The Healthcare Infection Society. Published by Elsevier Ltd.All rights reserved.doi:10.1016/j.jhin.2011.08.023
ary 2007 to June 2011: total sets received, sets yielding significantwn for each category.
Blood culture contamination: having your cake and eating itConflict of interest statementFunding sourcesReference