The Existence of Gram-Negative Bacteria that do not Digest Lactose in the Feces and their Resistance to Specific Drugs

Abstract

The study’s objectives were to identify non-lactose fermenting Gram-negative bacteria from stool samples from many diarrheal patients and to use the disc diffusion method to perform an antibiotic sensitivity test to assess the degree of antibiotic resistance. Between December 2022 and March 2023, 100 stool samples were taken from a few patients at Al-Imam Alhasan Hospital. The MacConky agar medium was used to cultivate the samples. 77% of the bacteria were lactose-fermenting, while 22% were not. Out of 100 isolates, 18 fermented lactose. The percentages of the isolates were as follows: Pseudomonas bacteria in 4 out of 18 isolates 23%, Shigella bacteria in 2 out of 18 isolates (12.3%), Salmonella bacteria in 10 out of 18 isolates 54%, and Proteus bacteria in 2 out of 18 isolates (12.5%). The results of a sensitivity test using the diffusion method for ten antibiotics revealed that by measuring the diameter of colony growth inhibition around the antibiotic in millimeters and comparing the results to the international specifications (2020, Clinical and Laboratory Standards Institute), the bacteria were either sensitive (S) or resistant (R). The most inhibiting antibiotic, ciprofloxacin, was 90% inhibiting, followed by ceftriaxone at 80% and ampicillin at 15%.