Molecular Analysis of Coagulase‐Negative<i>Staphylococcus</i>Isolates from Blood Cultures: Prevalence of Genotypic Variation and Polyclonal Bacteremia

Sharma, Mamta; Riederer, Kathleen; Johnson, Leonard B.; Khatib, Riad

doi:10.1086/322673

Cited by 35 publications

(32 citation statements)

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“…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).…”

Section: Discussionmentioning

confidence: 99%

“…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).…”

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confidence: 99%

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

et al. 2006

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We sought here to review the present definition of catheter-related bloodstream infections (CR-BSI) due to coagulase-negative staphylococci (CNS) by comparing the routine phenotypic methods with a genotypic procedure that considers different morphotypes. Our phenotypic characterization of CNS isolates included routine identification with biotype and antibiotype. The genotypic diagnosis was based on longer incubation periods with the consideration of all morphotypes and molecular typing by pulsed-field gel electrophoresis techniques. We prospectively selected 61 episodes of suspected CR-BSI by CNS occurring during 1 year, based on the presence of a compatible clinical setting and the isolation of one or more CNS from blood and catheter tip. Of these episodes, 47 (77%) were identified as true episodes of CR-BSI based on the presence of microorganisms of the same genotype in the blood and on the catheter tip. The sensitivity, specificity, positive predictive, negative predictive, accuracy, positive likelihood ratio, and negative likelihood ratio values obtained by different phenotypic microbiological approaches to establish the diagnosis of CR-BSI were as follows: identity at species level (78. Catheter-related bloodstream infections (CR-BSI) are the main cause of documented sepsis (4, 5) in modern hospitals (2,20,27) and are mainly produced by coagulase-negative staphylococci (CNS) (6,26,32). The confirmed definition of a CR-BSI requires the isolation of one or more identical microorganism/s from blood and the catheter tip (19). However, present definitions are far from clear regarding the demonstration of such identity, particularly in the case of CNS. Most CNS colonies look alike after 24-h incubation, and laboratory routine involves taking a single colony for identification and antimicrobial susceptibility tests from those CNS growing in blood and on catheter tip cultures. The identity of both isolates is usually established on a phenotypic basis when the same genus, species, and antibiotype of the isolates in both samples are present. It is well known, however, that CNS growing on catheter tips may be frequently polyclonal (6, 12), especially when colonies are observed after longer periods of incubation. Moreover, biotype and antibiotype may have a weak correlation with genotype in CNS (22,30,34).7%We compare here the yields of two procedures for the characterization of CNS CR-BSI: "phenotypic" characterization, carried out in microbiology laboratories on a daily basis, and a procedure by which the different morphotypes are obtained after prolonged incubation and the application of genotyping with molecular techniques. MATERIALS AND METHODS Selection of Patients with CR-BSI.During a one-year period, we prospectively selected all consecutive patients fulfilling the following criteria: (i) age of Ն18 years; (ii) clinical signs of nosocomial sepsis (patients who had been in the hospital for more than 48 h when the first episode of fever was recorded and with one or more of the following signs or symptoms: tempera...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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

et al. 2006

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“…PFGE analysis has been used by several researchers to assess strain relatedness and to determine the significance of CoNS isolated from multiple blood cultures (9,21). Two recent studies have shown that fewer than half of the patients with two or more blood cultures positive for CoNS had the same strain (8,20).…”

Section: Discussionmentioning

confidence: 99%

Bloodstream Infection in Neutropenic Cancer Patients Related to Short-Term Nontunnelled Catheters Determined by Quantitative Blood Cultures, Differential Time to Positivity, and Molecular Epidemiological Typing with Pulsed-Field Gel Electrophoresis

et al. 2003

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To determine the rate of catheter-related bloodstream infection (CRBSI) among cases of primary bloodstream infection (BSI) in febrile neutropenic cancer patients with short-term nontunnelled catheters, quantitative paired blood cultures (Isolator) from the central venous catheter (CVC) and peripheral vein were obtained between November 1999 and January 2001. Bactec blood culture bottles were obtained to determine the differential time to positivity (DTP). CRBSI was defined as a quantitative blood culture ratio of >5:1 (CVC versus peripheral) with proven identity of isolates from positive peripheral and CVC blood cultures as confirmed by pulsed-field gel electrophoresis. Forty-nine episodes of primary BSI were detected among 235 cancer patients with febrile neutropenia. Of these, 18 episodes (37%) were CRBSI and 31 (63%) were BSI with an unknown portal of entry. Coagulase-negative staphylococci were present in nine cases of CRBSI (50%). The identity of isolates from peripheral and CVC blood cultures was confirmed in all cases. Earlier positivity (>2 h) of CVC-drawn versus peripheral blood cultures was observed in 18 of 22 CRBSI-associated blood cultures (sensitivity, 82%; specificity, 88%; positive predictive value, 75%; negative predictive value, 92%). In summary, CRBSI accounted for 37% of cases of primary BSI in this population of neutropenic cancer patients. DTP compares favourably with quantitative blood cultures for the diagnosis of CRBSI and may be particularly useful for patients in whom catheter salvage is highly desirable.

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“…However, it has been reported that 6 to 21% of true bacteremia cases represent polymicrobial infections (17,35). None of the current methods used to determine species or strain identity are capable of direct identification of polymicrobial infections; subculture of the clinical sample is necessary.…”

Section: Discussionmentioning

confidence: 99%

Staph ID/R: a Rapid Method for Determining Staphylococcus Species Identity and Detecting the mecA Gene Directly from Positive Blood Culture

Pasko¹,

Hicke²,

Dunn³

et al. 2012

J Clin Microbiol

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Rapid diagnosis of staphylococcal bacteremia directs appropriate antimicrobial therapy, leading to improved patient outcome. We describe herein a rapid test (<75 min) that can identify the major pathogenic strains of Staphylococcus to the species level as well as the presence or absence of the methicillin resistance determinant gene, mecA. The test, Staph ID/R, combines a rapid isothermal nucleic acid amplification method, helicase-dependent amplification (HDA), with a chip-based array that produces unambiguous visible results. The analytic sensitivity was 1 CFU per reaction for the mecA gene and was 1 to 250 CFU per reaction depending on the staphylococcal species present in the positive blood culture. Staph ID/R has excellent specificity as well, with no cross-reactivity observed. We validated the performance of Staph ID/R by testing 104 frozen clinical positive blood cultures and comparing the results with rpoB gene or 16S rRNA gene sequencing for species identity determinations and mecA gene PCR to confirm mecA gene results. Staph ID/R agreed with mecA gene PCR for all samples and agreed with rpoB/16S rRNA gene sequencing in all cases except for one sample that contained a mixture of two staphylococcal species, one of which Staph ID/R correctly identified, for an overall agreement of 99.0% (P < 0.01). Staph ID/R could potentially be used to positively affect patient management for Staphylococcus-mediated bacteremia.

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Molecular Analysis of Coagulase‐NegativeStaphylococcusIsolates from Blood Cultures: Prevalence of Genotypic Variation and Polyclonal Bacteremia

Cited by 35 publications

References 25 publications

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

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

Bloodstream Infection in Neutropenic Cancer Patients Related to Short-Term Nontunnelled Catheters Determined by Quantitative Blood Cultures, Differential Time to Positivity, and Molecular Epidemiological Typing with Pulsed-Field Gel Electrophoresis

Staph ID/R: a Rapid Method for Determining Staphylococcus Species Identity and Detecting the mecA Gene Directly from Positive Blood Culture

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