MDRO Prevention Program Elements: The CDC Tier 1/Tier 2 Framework

A multidrug-resistant organism (MDRO) prevention program is not a single intervention like Enhanced Barrier Precautions or a hand hygiene policy — it is a structured set of routine and, when needed, intensified controls that a facility runs continuously and escalates deliberately. CDC/HICPAC’s Management of Multidrug-Resistant Organisms in Healthcare Settings guideline organizes this into a two-tier framework that still structures CDC’s current MDRO prevention guidance: Tier 1 measures that apply to every healthcare setting regardless of MDRO prevalence, and Tier 2 measures that a facility adds when Tier 1 alone is not controlling transmission.

This page walks through what belongs in each tier, what actually triggers the move from Tier 1 to Tier 2, and how a program builds the organism-specific surveillance that both tiers depend on. For the nursing-home-specific precaution category built on top of this framework, see Enhanced Barrier Precautions; for the broader precaution categories EBP sits alongside, see Transmission-Based Precautions.

Tier 1: routine prevention, every setting, regardless of prevalence

Tier 1 is the baseline every acute-care hospital, long-term care facility, and ambulatory setting is expected to run continuously, independent of whether the facility currently has an MDRO problem. CDC frames the first Tier 1 element as administrative: making MDRO prevention an explicit organizational patient-safety priority with real fiscal and staffing support behind it, not an unfunded expectation placed on frontline infection prevention staff. A facility without in-house epidemiologic expertise — a small or rural hospital, a rehabilitation center, a freestanding ambulatory center — is expected to identify outside consultation rather than skip the analysis.

Built on that administrative foundation, Tier 1 routine measures cluster into a few functional groups:

• Standard infection prevention practice — hand hygiene compliance, and Contact Precautions applied per facility policy for patients known or suspected to be colonized or infected with a target MDRO. See Transmission-Based Precautions for what Contact Precautions specifically requires versus Droplet and Airborne categories.
• Device and antimicrobial stewardship — minimizing unnecessary invasive device days (central lines, urinary catheters) and running a structured antimicrobial stewardship program, since selective antibiotic pressure is a direct driver of MDRO emergence. See Antimicrobial Stewardship Program: CDC Core Elements and Requirements for the program structure CDC expects.
• Environmental cleaning and disinfection — routine terminal and daily cleaning of high-touch surfaces and shared equipment, since several CDC-targeted organisms (notably Candida auris and carbapenem-resistant organisms) persist on environmental surfaces well beyond what routine cleaning protocols were originally designed around.
• Laboratory-based alert and notification systems — the microbiology lab flags a target-organism result to infection prevention promptly enough for precautions and contact-tracing to start immediately, and inter-facility transfer communication so a receiving facility knows a patient’s MDRO status before admission.
• Education — for clinical staff on precaution rationale and technique, and for patients/families on what a positive result does and does not mean for their care.
• Baseline surveillance — tracking MDRO incidence and prevalence routinely, not only during an outbreak, since Tier 1-to-Tier 2 escalation is a data-driven decision, not a subjective one. See the surveillance section below.

What actually triggers escalation to Tier 2

CDC’s own escalation language is specific and worth stating precisely, because “things seem bad” is not the trigger: Tier 2 interventions are indicated when facility MDRO incidence or prevalence is not decreasing despite consistent Tier 1 implementation, or as soon as the first case of a facility outbreak is identified. That second trigger point matters operationally — a program that waits for a defined outbreak threshold (a specific case count or attack rate) before escalating is already behind the guideline’s own definition of when to act.

This is also where surveillance data becomes a decision input rather than a retrospective report: a program that only reviews its MDRO numbers quarterly cannot detect a “not decreasing” trend or a first case in time to escalate promptly. Real-time or near-real-time review of surveillance data against a facility’s own baseline is what makes the trigger usable rather than theoretical.

Tier 2: intensified interventions

Tier 2 is not a single new precaution — published evaluations of successful MDRO control programs report a median of seven to eight distinct interventions implemented concurrently or in sequence, which is itself an argument against treating any one Tier 2 measure as sufficient on its own. The interventions most consistently associated with successful control include:

• Active surveillance testing (AST) — culturing patients for a target organism specifically to detect colonization that clinical cultures alone would miss, typically on admission to a unit and at defined intervals thereafter. Where AST is used, Contact Precautions are typically applied pending a negative admission result for the target organism, not withheld until a result returns.
• Enhanced environmental cleaning and disinfection — going beyond routine terminal cleaning, often with verification (fluorescent marker checks, ATP testing, or UV/hydrogen-peroxide-vapor terminal disinfection for specific high-risk rooms).
• Chlorhexidine or other antiseptic bathing protocols for at-risk patient populations, where indicated. See Chlorhexidine (CHG) Bathing Protocol for concentration, frequency, and the application errors that most often cut its real-world efficacy.
• Cohorting of colonized or infected patients, and dedicated staffing where feasible, to reduce cross-transmission opportunities beyond what Contact Precautions alone provides.
• Reinforced hand hygiene auditing and feedback, and reinforced device/antimicrobial stewardship review specifically for the affected unit.
• Point prevalence surveys during an active outbreak investigation — a facility-wide or unit-wide screening snapshot used both as an infection-control intervention in its own right and as data for the epidemiologic investigation.

The evidence base behind this tiered structure includes the 2021 HICPAC white paper on Enhanced Barrier Precautions in skilled nursing facilities, which found that more than half of nursing home residents may be colonized with an MDRO at any given time — the reason EBP exists as a facility-wide, Tier-2-adjacent baseline for that setting rather than a response reserved for confirmed outbreaks. See Enhanced Barrier Precautions for how that specific nursing-home program is structured, including the eight high-contact care activities it governs and where CDC and CMS guidance diverge on implementation details.

CDC-targeted organisms versus locally important organisms

A program’s surveillance and Tier 2 escalation decisions should distinguish between two organism categories, because they don’t carry the same expectation:

• CDC-targeted MDROs — pan-resistant organisms, carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE), carbapenemase-producing carbapenem-resistant Pseudomonas species, carbapenemase-producing carbapenem-resistant Acinetobacter baumannii, and Candida auris. These warrant escalated response essentially regardless of local prevalence, given their resistance profile and outbreak potential.
• Locally epidemiologically important organisms — examples CDC cites include MRSA, ESBL-producing Enterobacterales, VRE, multidrug-resistant Pseudomonas aeruginosa, and drug-resistant Streptococcus pneumoniae. Whether these warrant Tier 2 response is a facility- and jurisdiction-specific judgment based on local incidence trends, not a blanket national trigger.

Building organism-specific surveillance

A program can’t apply the “not decreasing” trigger without a defined surveillance mechanism producing comparable numbers over time. For US hospitals, that mechanism is typically the NHSN MDRO and C. difficile Infection (CDI) Module, one of the surveillance components in the NHSN Patient Safety Component — see Navigating the NHSN Patient Safety Component Manual for where that module sits relative to the device-associated and procedure-associated modules most infection preventionists work in first.

Building organism-specific surveillance inside that structure means defining, in writing and in advance:

• The target organism(s) and case definition — a LabID event definition (specimen source, organism, and, where relevant, resistance phenotype) rather than a clinical diagnosis, so two reviewers reach the same count from the same lab data.
• The denominator — patient-days or admissions for the unit or facility being tracked, so a raw case count converts into a rate that’s comparable across time periods and, cautiously, across facilities.
• Community-onset versus healthcare-onset attribution — typically split by a specimen-collection-day cutoff (commonly day 3 of admission), since a program can’t meaningfully judge its own control efforts against cases the patient likely brought in from outside.
• A standardized comparison metric once enough data accumulates — the Standardized Infection Ratio (SIR) is the risk-adjusted comparison NHSN uses for several HAI categories and is the right frame for judging whether an MDRO rate is meaningfully “not decreasing” versus normal period-to-period noise.
• A review cadence frequent enough to catch a first outbreak case promptly — the whole point of the Tier 1/Tier 2 trigger logic above collapses if surveillance data sits unreviewed for weeks.

Program elements that exist on paper but aren’t backed by a working surveillance definition, denominator, and review cadence can’t actually support the escalation decision the tiered framework depends on — which is why surveillance design belongs in the program’s foundational documentation, not as an afterthought once a suspected outbreak is already underway.

Frequently asked questions

Is Enhanced Barrier Precautions the same thing as an MDRO prevention program?

No. EBP is one specific, nursing-home-focused precaution category built on top of this broader framework — it’s a Tier-2-adjacent baseline measure for a setting where MDRO colonization prevalence is unusually high. An MDRO prevention program is the full Tier 1/Tier 2 structure across surveillance, stewardship, environmental control, and precautions that applies to any healthcare setting, not just nursing homes. See Enhanced Barrier Precautions for the EBP-specific detail.

What actually triggers moving from Tier 1 to Tier 2?

Two triggers: facility MDRO incidence or prevalence that is not decreasing despite consistent Tier 1 implementation, or the first case of a facility outbreak — whichever comes first. Neither requires waiting for a defined outbreak case-count threshold.

Does every MDRO get the same level of response?

No. CDC-targeted MDROs (pan-resistant organisms, carbapenemase-producing CRE/CRPA/CRAB, and Candida auris) generally warrant an escalated response regardless of local prevalence. Locally epidemiologically important organisms such as MRSA, ESBL-producing Enterobacterales, and VRE are judged against a facility’s own baseline trend.

What surveillance system do US hospitals typically use for MDRO tracking?

The NHSN MDRO and CDI Module, part of the NHSN Patient Safety Component. See Navigating the NHSN Patient Safety Component Manual for how that module relates to NHSN’s other surveillance components.