Errors are a problematic theme in today’s medicine. While error is associated with humans, error brings substantial increase in medical expense, morbidity, mortality, and can contribute to public health concerns, such as antibiotic resistance. Error in medicine can be explained by system’s theory, where human error is attributed to system flaws. The purpose of this correlational quantitative research is to bring light to the prevalence of error that occurs with antibiotic susceptibility testing in the clinical laboratory; and to further establish the relationship that exists among dependent variable procedural knowledge and independent variables licensure and certification. A retrospective review of antibiotic susceptibility proficiency testing was conducted to indicate outliers in proficiency testing results. Descriptive statistics were performed to determine the prevalence of incorrect proficiency testing results for antibiotic susceptibility testing. A survey was distributed to five hundred and thirty-six medical laboratory microbiology professionals to determine the relationship between dependent variable procedural knowledge and independent variables licensure and certification. Survey questions were designed using Clinical Laboratory Standards Institute (CLSI) standards for performing daily routine bacterial inoculums for antibiotic susceptibility testing. A multiple regression analysis indicated a strong statistical significance between the independent variables’ certification and state licensure, and dependent variable procedural knowledge. It was determined there was a strong statistically significant correlation between the lack of antibiotic susceptibility procedural knowledge and laboratory professionals who do not hold a state licensure (p <0.001). There was also a strong statistically significant correlation between the lack of antibiotic susceptibility procedural knowledge and laboratory professionals who are not certified by a nationally recognized certifying agency (p <0.001). A parallel study was conducted congruently to ensure reproducibility. The parallel study results also indicated a correlation between dependent and independent variables. Laboratory professionals who are certified and/or hold a state licensure reduce medical error and contributors of antibiotic resistance. This research demonstrates the value of certification and state licensure among laboratory professionals when performing antibiotic susceptibility testing .