9

Laboratory-identified Multidrug-Resistant Organism
(MDRO) & Clostridium difficile Infection (CDI) Events for
Long-term Care Facilities
Background: Clostridium difficile infections (CDI), methicillin-resistant Staphylococcus aureus
(MRSA), vancomycin-resistant Enterococcus spp. (VRE) and certain multidrug-resistant gramnegative bacilli (e.g. carbapenem-resistant Klebsiella spp.) have increased in prevalence in U.S.
healthcare settings over the last three decades and have important implications for residents of
long-term care facilities (LTCF). Studies have demonstrated a large proportion of residents are at
risk for carrying or acquiring these multidrug-resistant organisms (MDRO) in LTCF. MDRO
infections are associated with increased lengths of stay, hospitalizations and readmissions,
increased healthcare costs, and mortality due to more severe illnesses and limited treatment
options. CDI can present a variety of ways including uncomplicated diarrhea,
pseudomembranous colitis, and toxic megacolon which can, in some instances, lead to sepsis and
even death. Infections from C. difficile represent a subset of gastroenteritis and gastrointestinal
tract infections. Standard definitions for CDI should be incorporated into infection surveillance
programs to obtain a more complete understanding of how C. difficile can manifest and be
transmitted in LTCFs.
The Laboratory-identified (LabID) Event Module of the NHSN LTCF Component is a tool
designed for use in certified skilled nursing facilities/nursing homes (LTC:SKILLNURS) and
intermediate/chronic care facilities for the developmentally disabled (LTC:DEVDIS) to help
meet criteria outlined in guidelines for the prevention, control and surveillance of MDRO & CDI
1-5
. As outlined in these guidelines, these pathogens may require specialized monitoring to
evaluate if intensified infection control efforts are required to reduce the occurrence of these
organisms and related infections. The goal of this module is to provide a mechanism for facilities
to collect, report, and analyze data that will inform infection control staff of the impact of
prevention efforts. This module contains two options, one focused on CDI and the second on
MDROs.

1: Smith et al. SHEA/APIC Guideline: Infection Prevention and Control in the Long-Term Care Facility. Infection
Control and Hospital Epidemiology 2008;29:785-814.
2: Healthcare Infection Control Practices Advisory Committee (HICPAC) approved guidelines for the control of
multidrug resistant organism (MDRO). Available at www.cdc.gov/hicpac/pdf/ MDRO/ MDROGuideline2006. .pdf
3: Cohen et al. Clinical Practice Guideline for Clostridium difficile infection in Adults: 2010 Update by SHEA and
IDSA. Infection Control and Hospital Epidemiology 2010;31:431-55.
4: Simor et al. Clostridium difficile in Long-Term Care Facilities for the Elderly. SHEA Position Paper. Infection
Control and Hospital Epidemiology 2002;23:696-703.
5: Cohen et al. Recommendations for Metrics for Multidrug-Resistant Organisms in Healthcare Settings:
SHEA/HICPAC Position Paper. Infection Control and Hospital Epidemiology 2008;29:901-13.

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I. Clostridium difficile Infection (CDI) Surveillance by Laboratory-identified (LabID) Event
Methods: The CDI surveillance option allows laboratory testing data to be used without clinical
evaluation of the resident, allowing for a less labor intensive method to track C. difficile. This
method provides proxy measures of C. difficile healthcare acquisition, exposure burden, and
infection burden based solely on laboratory data and limited resident admission/transfer data.
The data collected will enable participating facilities and CDC to calculate several infection
surveillance metrics (listed below). NHSN forms should be used to collect all required data,
using the definitions of each data field as indicated in the Tables of Instructions.
Settings: CDI LabID Event reporting is currently available for certified skilled nursing
facilities/nursing homes (LTC:SKILLNURS) and intermediate/chronic care facilities for the
developmentally disabled (LTC:DEVDIS). Events reported should include C. difficile positive
laboratory assays obtained from any resident who is receiving care at the facility. Laboratory
results available from other healthcare facilities before the resident was admitted to your
facility should not be reported as LabID Events.
Requirements: Facilities must report LabID Events and denominators (number of resident
admissions and number of resident-days) for the entire facility (FacWideIN) each month for at
least 6 consecutive months, which allows for the most easily obtainable complete data
acquisition. C. difficile laboratory testing should be performed only on liquid or watery stool
samples (i.e., conforming to the shape of the specimen collection container).
Facilities must indicate their reporting for the calendar month in the Monthly Reporting Plan for
LTCF (CDC 57.141).
Definitions:
C. difficile -positive laboratory assay: A positive result for a laboratory test for C. difficile toxin
A and/or B (e.g., enzyme immunoassay, or EIA test), OR a toxin-producing C. difficile organism
detected in the stool specimen by culture or other laboratory means (e.g., nucleic acid
amplification testing by polymerase-chain reaction, or PCR).
Duplicate C. difficile-positive laboratory assay: Any C. difficile positive laboratory test
from the same resident following a previous C. difficile positive test within the past two
weeks
CDI Laboratory-identified (LabID) Event: All non-duplicate C. difficile positive
laboratory assays obtained while a resident is receiving care in the long-term care
facility. (See Figure 1 - C. difficile Test Result Algorithm for Laboratory-identified
(LabID) Events.)
NOTE: Laboratory results obtained from outside facilities, before a resident’s
admission, should not be entered as LabID Events.

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Incident CDI LabID Event: The first LabID Event ever entered or a subsequent LabID Event
entered > 8 weeks after the most recent LabID Event reported for an individual resident.
Recurrent CDI LabID Event: Any LabID Event entered > 2 weeks and ≤ 8 weeks after the most
recent LabID Event reported for an individual resident.
All incident or recurrent LabID Events will be further categorized by NHSN into
Community-onset vs. LTCF-onset based on date of current admission to facility and date
of specimen collected. Because of variability in documenting time of admission to the
LTCF, calendar days are used to categorize LabID Events.
Community-onset (CO) LabID Event: Date specimen collected ≤ 3 calendar days from date of
current admission to the facility (i.e., days 1, 2, or 3 of admission).
Long-term Care Facility-onset (LO) LabID Event: Date specimen collected > 3 calendar days
after current admission to the facility (i.e., on or after day 4).
LO can be further sub-classified as;
Acute Care Transfer-Long-term Care Facility-onset (ACT-LO): LTCF-onset (LO) LabID
Event with date specimen collected ≤ 4 weeks following date of last transfer from an
Acute Care Facility (Hospital, Long-term acute care hospital, or acute inpatient
rehabilitation facility only).
Example: NHSN Classification of Lab ID Events as Community-onset or LTCF-onset
Admission date
June 4th

June 5th

June 6th

June 7th

June 8th

day 1

day 2

day 3

day 4

day 5

Community-onset (CO)

Long-term Care Facility-onset (LO)

Numerator and Denominator Data:
Numerator: Data on each CDI LabID Event will be reported using the Laboratory-identified
MDRO or CDI Event for LTCF form (CDC 57.138). (See Tables of Instructions for information
on how to complete this form.)
Denominator: Monthly totals for resident-days and resident admissions are collected using the
Denominators for LTCF form (CDC 57.142). (See Tables of Instructions for information on how
to complete this form.)

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CDI Data Analysis:
Data are stratified by time (e.g., month, quarter, etc.), whether an episode is incident or recurrent,
community-onset or LTCF-onset and aggregated across the entire facility.
Calculated CDI Rates and Metrics:
Line lists of CDI LabID Events will be available as part of the analysis within the NHSN LTCF
component. Below are measures and calculations which will be incorporated into the analytics
output that will be available for use in 2013.
Total CDI Rate/10,000 resident-days = Number of CDI LabID Events per month regardless of
time spent in the facility (i.e., CO + LO) / Number of resident-days per month x 10,000.
CDI Long-term Care Facility-onset Incidence Rate/10,000 resident-days = Number of all
incident LO CDI LabID Events per month / Number of resident-days x 10,000.
This formula excludes recurrent CDI events.
Percent that is Community-onset = Number of CDI LabID Events that are CO / Total number of
CDI LabID Events x 100.
Percent that is Long-term Care Facility-onset = Number of CDI LabID Events that are LO /
Total number of CDI LabID Events x 100.
Percent of LO that is Acute Care Transfer-Long-term Care Facility-onset = Number of
ACT-LO CDI LabID Events / Total number of LO CDI LabID Events x 100.
Percent that is Recurrent CDI = Number of CDI LabID Events that are recurrent / Total number
of CDI LabID Events x 100.

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Figure 1. C. difficile Test Result Algorithm for Laboratory-identified (LabID) Events.
Positive C. difficile
test result
NO

Prior Positive < 2
weeks

Duplicate – Not
a Lab ID Event

Report as Lab
ID Event

Incident if no
previous positive,
or prior positive
>8 weeks

YES

Recurrent if
prior positive
>2 and < 8
weeks

II. MDRO Surveillance by Laboratory-identified (LabID) Event
Methods: Facilities may choose to monitor one or more of the following MDROs:
Staphylococcus aureus, both methicillin-resistant (MRSA) and methicillin-susceptible
(MSSA), vancomycin-resistant Enterococcus spp. (VRE), cephalosporin-resistant Klebsiella
spp., carbapenem-resistant Klebsiella spp., carbapenem-resistant E. coli, and multidrugresistant Acinetobacter spp.
Laboratory-identified (LabID) Event reporting is the surveillance method for LTCF and allows
laboratory testing data to be used without clinical evaluation of the resident, creating a less labor
intensive method to track MDROs. This method provides proxy measures of MDRO infections,
healthcare acquisition, exposure burden, and infection burden based solely on laboratory data
and limited resident admission/transfer data.
LabID Event reporting is ONLY for collecting and tracking isolates from positive cultures that
are taken for "clinical" purposes (i.e., for diagnosis and treatment), which means that Active
Surveillance Culture/Testing (e.g., nasal swabs for MRSA or perirectal swabs for VRE) results
are not reported as LabID Events. Laboratory results available from other healthcare facilities
before the resident was admitted to your facility should not be reported as LabID Events.
The data collected will enable participating facilities and CDC to calculate several measures,
depending on which MDROs the facility chooses to track. NHSN forms should be used to collect
all required data, using the definitions of each data field as indicated in the Tables of
Instructions.

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Setting: MDRO LabID Event reporting is currently available for certified skilled nursing
facilities/nursing homes (LTC:SKILLNURS) and intermediate/chronic care facilities for the
developmentally disabled (LTC:DEVDIS). Events reported should include MDRO positive
laboratory cultures obtained from any resident who is receiving care at the facility.
Requirements: Facilities must report LabID Events and denominators (number of resident
admission and number of resident-days) for the entire facility (FacWideIN) each month for at
least 6 consecutive months, which allows for the most easily obtainable complete data
acquisition. Report only one LabID Event organism (positive isolate) per form.
Facilities must indicate their reporting for the calendar month in the Monthly Reporting Plan for
LTCF (CDC 57.141).
Definitions: The following MDROs can be selected for tracking in the LabID Event module:
Gram-stain positive organisms:
•

MRSA: Includes S. aureus cultured from any specimen that tests oxacillin-resistant,
cefoxitin-resistant, or methicillin-resistant by standard susceptibility testing methods, these
methods may also include a positive result by any FDA-approved test for direct MRSA
detection from that specimen source.

•

MSSA: S. aureus cultured from any specimen testing intermediate or susceptible to oxacillin,
cefoxitin, or methicillin by standard susceptibility testing methods; a positive result from any
FDA-approved test for direct MSSA detection from that specimen source; or a negative result
from a test that is FDA-approved for direct MRSA detection from a specimen source.

•

VRE: Any Enterococcus spp. (regardless of whether identified to the species level), that is
resistant to vancomycin, by standard susceptibility testing methods or by a positive result
from any FDA-approved test for VRE detection from that specimen source.

Gram-stain negative organisms:
•

CephR-Klebsiella: Any Klebsiella spp. testing non-susceptible (i.e., resistant or intermediate)
to cephalosporin antibiotics like ceftazidime, cefotaxime, ceftriaxone, or cefepime.

•

CRE-Ecoli: Any E. coli testing non-susceptible (i.e., resistant or intermediate) to carbapenem
antibiotics like imipenem, meropenem, or doripenem, by standard susceptibility testing
methods or by a positive result by from a FDA-approved test for carbapenemase detection
from that specimen source.

•

CRE-Klebsiella: Any Klebsiella spp. testing non-susceptible (i.e., resistant or intermediate)
to carbapenem antibiotics like imipenem, meropenem, or doripenem, by standard
susceptibility testing methods or by a positive result for any method FDA-approved for
carbapenemase detection from that specimen source.

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•

MDR-Acinetobacter: Any Acinetobacter spp. testing non-susceptible (i.e., resistant or
intermediate) to at least one agent in at least 3 antimicrobial classes of the following 6
antimicrobial classes:

Antimicrobial Class

Agents

β-lactams and βlactam/β-lactamase
inhibitor combinations

Piperacillin, Piperacillin/tazobactam

Sulbactam

Ampicillin/sulbactam,

Cephalosporins

Cefepime, Ceftazidime, Ceftriaxone, Cefotaxime

Carbapenems

Imipenem, Meropenem, Doripenem

Aminoglycosides

Amikacin, Gentamicin, Tobramycin

Fluoroquinolones

Ciprofloxacin, Levofloxacin

MDRO positive laboratory isolate: Any laboratory specimen source, from which a MDRO
is identified, obtained for clinical decision making (as defined above) while a resident is
receiving care in the facility.
Duplicate MDRO laboratory isolate: Any MDRO isolate from the same resident after an initial
isolation of the same organism during a calendar month, regardless of the specimen source
except when a unique blood source is identified (see definition below and Figure 2).
NOTE: A duplicate MDRO laboratory isolate should not be reported as a LabID Event.
Unique blood source MDRO laboratory isolate: A MDRO isolate identified in a blood culture
from a resident with no prior isolation of the MDRO in blood in the past 2 weeks, even across
calendar months. A unique blood source isolate should be reported even if the resident had this
same MDRO previously isolated in a non-blood specimen earlier during the same calendar
month (See Figure 2).
NOTE: As a general rule, at a maximum, there should be no more than 2 blood isolates (which
would be very rare) and 1 other specimen source isolate per MDRO type reported for the same
resident during a calendar month.

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MDRO Laboratory-identified (LabID) Event: All non-duplicate MDRO positive laboratory
isolates from any culture specimen, regardless of specimen source or MDRO unique blood
source isolates obtained while a resident is receiving care in the facility.
NOTE: Laboratory data available from outside facilities, before a resident’s admission, should
not be entered as LabID Events.
All MDRO LabID Events will be further categorized by NHSN into Community-onset vs.
LTCF-onset based on date of current admission to facility and date of specimen collected.
Because of variability in documenting time of admission to the LTCF, calendar days are used to
categorize LabID Events.
Community-onset (CO) LabID Event: Date specimen collected ≤ 3 calendar days after resident
admission to the facility (i.e., days 1, 2, or 3 of admission).
Long-term Care Facility-onset (LO) LabID Event: Date specimen collected > 3 calendar days
after admission to the facility (i.e., on or after day 4).
LO can be further sub-classified as:
Acute Care Transfer-Long-term Care Facility-onset (ACT-LO): LTCF-onset (LO) LabID
Event with date specimen collected ≤ 4 weeks following date of last transfer from an
Acute Care Facility (Hospital, Long-term acute care hospital, or acute inpatient
rehabilitation facility only).
Example: NHSN Classification of Lab ID Events as Community-onset or LTCF-onset
Admission date
June 4th

June 5th

June 6th

June 7th

June 8th

day 1

day 2

day 3

day 4

day 5

Community-onset (CO)

Long-term Care Facility-onset (LO)

Numerator and Denominator Data:
Numerator: Data on each MDRO LabID Event will be reported using the Laboratory identified
MDRO or CDI Event for LTCF form (CDC 57.138). (See Tables of Instructions for information
on how to complete this form.)
Denominator: Monthly totals for resident admissions and resident-days are collected using the
Denominators for LTCF (CDC 57.142). (See Tables of Instructions for information on how to
complete this form.)
MDRO Data Analysis:
Data are stratified by time (e.g., month, quarter, etc.), whether an episode is community-onset or
LTCF-onset and aggregated across the entire facility.

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Calculated MDRO Rates and Metrics*:
Line lists of MDRO LabID Events will be available as part of the analysis within the NHSN
LTCF component. Below are measures and calculations which will be incorporated into the
analytics output that will be available for use in 2013.
*Note: These calculations will be performed for each specific MDRO included in the reporting
plan during a month (e.g., MRSA, VRE, etc.)
Total MDRO Rate/1,000 resident-days = Number of MDRO LabID Events per month
(regardless of time spent in the facility i.e., CO + LO ) / Number of resident-days per month x
1,000.
MDRO Long-term Care Facility-onset Incidence Rate/ 1,000 resident-days = Number of all LO
MDRO LabID Events per month / Number of resident-days x 1,000.
Percent of MDRO LabID Events that is Community-onset = Number of MDRO LabID Events
that are CO / Total number of MDRO LabID Events x 100.
Percent of MDRO LabID Events that is Long-term Care Facility-onset = Number of MDRO
LabID Events that are LO / Total number of MDRO LabID Events x 100.
Percent of LO LabID Events that is Acute Care-Transfer-Long-term Care Facility-onset
= Number of ACT-LO MDRO LabID Events / Total number of LO MDRO LabID
Events x 100.
Figure 2. MDRO Test Result Algorithm for Laboratory-identified (LabID) Events.
MDRO isolate from
any specimen
source

YES

Report as
Lab ID Event

1st in calendar
month

NO
Duplicate
MDRO isolate

Source =
BLOOD

NO

Duplicate - Not
a Lab ID Event

YES

Duplicate - Not
a Lab ID Event

YES
Prior positive with same
MDRO from blood in < 2
weeks (including across
calendar months)
NO
Unique blood source MDRO
- Report as Lab ID Event
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