SURVEILLANCE STRATEGIES: ANTIBACTERIAL RESISTANCE MONITORING AMONG BACTERIAL ISOLATES FROM ANIMALS, HUMANS AND FOODS

Paula J. Fedorka-Cray, USDA-ARS-Antimicrobial Resistance Research Unit

When a surveillance system is developed, seven areas should be considered. These include program development, culture techniques, isolation and identification if the bacterial isolates, testing and characterization of the isolates, analysis and interpretation of the data, data reporting, debate and citation of the data, and reassessment and possible redirection of the program.

Program development: Program development begins with an idea, ultimately leading to the implementation of a program. In the US, development of the National Antimicrobial Resistance Monitoring System - Enteric Bacteria (NARMS) was initiated in 1995. NARMS is a multi agency program led by the FDA-Center for Veterinary Medicine. Other participating partners include the CDC, FDA-Office of Research, and the USDA (ARS, APHIS, and FSIS). The system consists of two separate but parallel systems: the human arm of NARMS, administered by CDC and the animal arm of NARMS, administered by USDA.

Culture: Culture is the enrichment of a sample resulting in recovery of bacteria of interest. Culture methods often affect outcomes. For instance, use of an antimicrobial in media may result in the selection of a bacterial population rendered resistant to that particular antimicrobial.

Isolation and identification: Isolation and identification are tied directly to culture methods. This is a critical step in the process as misidentification can lead to the reporting of erroneous results.

Testing: Most surveillance systems include testing of the bacteria of interest. For NARMS, isolates are tested for susceptibility to antimicrobials that are important in both human and veterinary medicine.

Analysis and interpretation: Analyses are a fairly straightforward process, summarizing study findings. Interpretation, however, is subject to human bias and it is usual for data to be ‘over interpreted’. It is critically important to recognize that antimicrobial surveillance data is descriptive in nature, and that no cause or effect can be determined.

Reporting, debate and citation: Reporting of the data includes dissemination by hard copy, posting to a website, presentation at meetings and/or through scientific publication. Debate often ensues after the report is released as interpretation often varies between individuals/groups.

Reassessment and redirection: It is imperative that surveillance systems are continually reevaluated to ensure that the information is being correctly captured and reported. Redirection is often needed to ensure continued high quality data.

Fedorka-Cray, Paula J., USDA-ARS-Antimicrobial Resistance Research Unit, 950 College Station Road, Athens, GA 30605-2720. Tel: 706-5463685, Fax:706-546-3066, email: pcray@saa.ars.usda.gov.