Baylor University Medical Center Proceedings October 2017 - 396

documented for blood culture collection, Gram stain, BC-GN
result, conventional identiﬁcation and susceptibilities, and the
ﬁrst dose of appropriate antibiotic. For this study, we chose a
subset of GN organisms-Citrobacter spp., Enterobacter spp.,
Klebsiella spp. and Escherichia coli-as the recommended change
in antibiotics was most diﬀerent from empiric therapy and was
predicted to have a maximum impact upon change in antibiotics in response to stewardship recommendations. Other
GN bacteria such as Pseudomonas aeruginosa, Proteus spp., and
Acinetobacter spp. were also detected in the assay but were not
considered because of the likelihood of minimal impact on
empirical antibiotic usage. Appropriate adjustment was deﬁned
as deescalation of empiric therapy (vancomycin and piperacillin/
tazobactam) to the appropriate targeted coverage such as thirdor fourth-generation cephalosporins within 24 hours in response
to the stewardship recommendations on the Verigene report
(Table 1). Antibiotics were documented based on the date and
time that the dose was given as recorded in the EHR. Patients
who died during their hospital admission or were discharged
before Verigene results were available were excluded.
Blood was collected at individual sites and transported via
courier to med fusion. Upon arrival at med fusion, bottles were
incubated on the BacT/ALERT automated blood culture system
for up to 5 days. When the aerobic or anaerobic bottle was
identiﬁed as positive for bacterial growth, a Gram stain was
performed, with inoculation on appropriate solid agar media.
Plates were read after approximately 24 hours of incubation.
Identiﬁcation and susceptibility testing were performed using
Table 1. Targets detected on Verigene Blood Culture Gramnegative panel and associated stewardship comments
Verigene target
Citrobacter spp.,
Enterobacter spp.

Stewardship comments added to the
Verigene report
* Consider discontinuing empiric Gram-positive
coverage if appropriate.
* Consider a fourth-generation cephalosporin if
appropriate.
* Deescalate further when susceptibility results
are available.

Klebsiella pneumoniae, * Consider discontinuing empiric Gram-positive
Klebsiella oxytoca,
coverage if appropriate.
Escherichia coli
* Consider a third-generation cephalosporin if
appropriate.
* Deescalate further when susceptibility results
are available.
ESBL producer
(CTX-M)
Carbapenemase
producer (KPC, OXA,
VIM, IMP, NDM)

* Recommend use of meropenem.
* Deescalate when susceptibility results are
available.
* Initiate contact precautions.
* Consider infectious disease consult.

CTX-M indicates class A extended-spectrum beta-lactamases (Cefotaxime); IMP, imipenem-resistant metallo-beta-lactamase; KPC, K. pneumoniae carbapenemases; NDM, New
Delhi metallo-β-lactamase; OXA, OXA-type beta-lactamases/class D beta-lactamases/
oxacillinases; VIM, Verona integron-encoded metallo-beta-lactamase.

396

conventional phenotypic methods, MALDI-TOF and the
VITEK®2 (bioMérieux, Durham, NC). The ﬁrst bottle per
bacteremic episode that showed a GN organism on Gram stain
was tested using the BC-GN. The BC-GN was also run if the
Gram stain showed mixed organisms with Gram-positive or
other Gram stain morphologies.
The BC-GN results were called as a critical value to the
ﬂoor and were released in the EHR. For Citrobacter spp. and
Enterobacter spp., the Verigene report was accompanied by an
interpretive comment suggesting the appropriate antimicrobials were fourth-generation cephalosporins and recommending
discontinuation of empiric coverage. For Klebsiella spp. and
E. coli, appropriate antimicrobials included third-generation
cephalosporins and discontinuation of empiric coverage. The
stewardship recommendations were developed by a collaborative
team of ASP, infectious disease physicians, and laboratory staﬀ.
Student's t test was used to determine statistical signiﬁcance
in cases where intervention was made in response to the rapid
Verigene result vs. the availability of the ﬁnal report based on
conventional methods.
RESULTS
The patient demographic and laboratory data are summarized in Table 2. Overall, there was a slight predominance of
women (61.2%) in the study cohort. The mean age of women
was 56.6 ± 19.4 years, signiﬁcantly lower (P < 0.001) than the
mean age of the men (63.6 ± 15.9 years) at the time of the septic
episode. This was unlikely to have any clinical signiﬁcance. From
the time of the blood collection, the Gram stain was reported
within an average of 20.0 ± 10.4 hours and the BC-GN result
was reported within 2.5 ± 1.3 hours of the Gram stain. The time
between Gram stain and ﬁnal identiﬁcation and susceptibilities
using conventional methods was 73.6 ± 40.0 hours.
The distribution of the GN bacterial targets across the three
sites evaluated within the Baylor network is shown in Table 3.
Across the three sites evaluated, E. coli was the predominant
isolate (72.5%), 14.4% of which harbored extended spectrum
beta-lactamases (ESBLs). This was followed by Klebsiella spp.,

Table 2. Demographic and laboratory parameters for result
reporting (n = 899)
Parameter
Females: Males

Value

P value

550: 349

Age (years), mean ± SD
Overall

59.3 ± 18.5

Male

63.6 ± 15.9

Female

56.6 ± 19.4

<0.001

Time (hours), mean ± SD
Between draw and Gram stain result
Between Gram stain and Gram-negative blood
culture result
Between Gram stain and final report

Baylor University Medical Center Proceedings

20.0 ± 10.4
2.5 ± 1.3
73.6 ± 40.0

Volume 30, Number 4

Table of Contents for the Digital Edition of Baylor University Medical Center Proceedings October 2017