Microbial Ingress Testing is the evaluation of the ability of a medical device to resist or inhibit the transfer of infectious microorganisms under repeated simulated use conditions.  Many medical devices have features that could potentially allow microorganisms a point of entry directly into a patient or into sterile fluids during the course of clinical or home use, increasing the risk of infection.  This is especially true with repeated use, product misuse, or in the event of product failure.  Additionally, because surfaces can become contaminated during the course of normal device use, effective disinfection of devices and injection sites is critical to assure that patient safety is maintained. Microbial ingress testing can be used to evaluate these risks and to help manufacturers design effective products and/or recommend appropriate disinfection practices.

needleless connector Background

Needleless infusion systems have become more common in recent years in order to limit the number of sharps injuries and reduce the risk of blood borne infections to healthcare workers.  There are many types of needleless connectors2, and they may be an integral component to a medical device, such as a Y-site connector, or they may be separate accessories attached by the user at the time of use.  A split septum connector is one example of a needleless connector. One concern when using a split septum connector is that upon removal of the blunt cannula, which used to access the connector, a negative pressure may be introduced causing a reverse flow into the lumen of the catheter. This bi-directional fluid flow may increase the patient’s risk of infection due to the potential ingress of pathogens into the sterile fluid. A luer-activated device, positive/neutral fluid displacement methods, or antimicrobial device materials can be used to help prevent contamination of needleless connectors, but they may not completely eliminate microbial ingress.

 According to the Guidelines for the Prevention of Intravascular Catheter-Related Infections3

“Use of needleless connectors or mechanical valves appear to be effective in reducing connector colonization in some, but not all studies when compared with stopcocks and caps. …. Appropriate disinfectants must be used to prevent transmission of microbes through connectors. ….  Potential explanations for outbreaks associated with these devices include difficulty encountered in adequate disinfection of the surface of t he connector due to physical characteristics of the plastic housing diaphragm interface, fluid flow properties (laminar vs. turbulent), internal surface area, potential fluid dead space, inadequate flushing of the device due to poor visualization of the fluid flow pathway in opaque devices, and the presence of internal corrugations that cou ld harbor organisms, particularly if the catheters are used to withdraw blood.”

It quickly becomes apparent
  that proper use, cleaning, and disinfection processes are critical for successful infection protection.  As part of the premarket approval [510(k)] process for Intravascular Administration Sets, the FDA has recommended the use of microbial ingress tests simulating repeated access and has provided guidance concerning the practice of microbial ingress testing.3  Several studies have been reported evaluating the resistance of needleless connectors to microbial ingress.


needleless conne ctor Microbial Ingress Test summary

 The Microbial Ingress Test is a simulated use test that mimics the use of a device in a clinical sitting.  Key parameters of a needless connector microbial ingress test may include the following:

    • Conditioning or stressing of the test device with artificial patient soil to simulate device wear in the field.

    • A number of microbial challenges determined by considering the number of user interactions that would be expected in the field.

    • The recommended disinfection or microbial resistance procedure is tested to demonstrate its effectiveness. 

 A detailed study protocol may be prepared for the specific needleless device designs using sponsor provided testing parameters.  Testing parameters may include the number of devices to be tested, the disinfection procedures, the number and length of testing cycles, and other conditions required in order to meet the device [510(k)] premarket approval requirements. Typically two gram negative and two gram positive organisms are chosen to demonstrate the ability of the test device to prevent ingress of infectious microorganisms. The protocol is reviewed and approved by the sponsor prior to initiating the testing. In the summary report, the study procedures are fully described, including the preparation, quantities and types of challenge organisms, the contamination or inoculation methods and sites, the sample size, the environmental conditions, the positive and negative controls used, along with any applicable validation methods.


StrenGths of needless device Microbial INgress Testing

Completion of microbial ingress testing will demonstrate the ability of the test device to prevent the transmission of microbial contamination when the agreed upon test procedures are followed. Microbial Ingress Testing allows the sponsor to report the microbial barrier properties of their devices with confidence and can be submitted as part of the requirements suggested by the FDAs guidance document for Intravascular Administration Sets Premarket Notification Submissions [510(k)].  


weaknesses of Needless device Microbial INgress Testing

As with any test method that simulates actual use, it is challenging to take all “real life” factors into account, and the test results will have limitations due to the assumptions used for the testing protocol.  Microchem will work with the sponsor to identify appropriate procedures and test conditions for testing protocols in order to best replicate use during actual patient procedures.


why microchem?

Since 1988 Microchem Laboratory has served industry needs as an EPA and FDA GLP-compliant testing organization with a wide array of product and customer tailored testing services for environmental surface disinfectants, high-level disinfectants, sanitizers, medical devices, antimicrobial surfaces, personal care products, and antimicrobial devices.  Our skilled, highly experienced microbiologists and chemists are ready to collaborate with you to evaluate the performance of your antimicrobial devices with regards to microbial ingress.  Microchem can help speed your project to completion.

Our microbial ingress studies are conducted following the guidance provided by the FDA1 in accordance with Good Laboratory Practice Standards (GLPs) stipulated by U.S. FDA 21 CFR 58.  In addition, studies are conducted in accordance with Microchem Laboratory’s Quality Management System and undergo a full quality assurance review.  All studies by Microchem Laboratories are conducted in accordance with general terms and conditions as posted on www.MicrochemLab.com/terms.  



1. Centers for Disease Control (CDC) laboratorian Mustafa Mazher holding up a disassembled needleless connector. Photo content provided by CDC/Melissa Dankel. Photo Credit James Gathany, 2014.  CDC Public Health Image Library, ID#16816.  http://phil.cdc.gov/phil/home.asp 

2.  Guidelines for the Prevention of Intravascular Catheter-Related Infections, 2011 http://www.cdc.gov/hicpac/pdf/guidelines/bsi-guidelines-2011.pdf p. 55-56.

3. Guidance for Industry and FDA Staff: Intravascular Administration Sets Premarket Notification Submissions [510(k)], U.S. Department of Health and Human Services Food and Drug Administration, 2008, Rockville, MD. http://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm070850.pdf

4. Photo Source: Callemanecer, licensed for sharing under the Creative Commons Attribution-Share Alike 3.0 Unported license, as described in  https://en.wikipedia.org/wiki/ICU_Medical

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