Requiring Reconsideration of Differences of Aeromonas Infections Between Extra-Intestinal and Intestinal in Hospitalized Patients

PURPOSE: The purpose of this study is to examine the variations between extra-intestinal and intestinal infections of Aeromonas in terms of strain types, risk factors, drug susceptibility results, and the distribution of drug resistance and virulence genes. PATIENTS AND METHODS: A total of 188 Aeromonas strains were identified to the species level using housekeeping genes (rpoD, gyrB, and gyrA). The risk factors for Aeromonas extra-intestinal and intestinal infection, as well as mortality, were retrospectively examined in this study. The broth microdilution method was used to investigate the antimicrobial susceptibility profiles. Touchdown polymerase chain reaction (PCR) assays and DNA sequencing were employed to confirm virulence and the presence of drug resistance genes. RESULTS: The housekeeping genes identified 188 strains into 7 species. Extra-intestinal isolates generally contained A. caviae and A. hydrophila, while intestinal were A. veronii (p=0.0001). Extra-intestinal infections (158/188) were the main type and accounted for 24/27 of all fatalities. Malignant tumors, hepatobiliary diseases, anemia, and hypoproteinemia were linked to infections. Poor results were associated with septic shock. Using the broth microdilution method, over 80% isolates were susceptible to most antimicrobials, except for ceftazidime (79.8%) and ceftriaxone (69.7%). Except for imipenem, intestinal strains were more susceptible to other medications than extra-intestinal. Using touch-down polymerase chain reaction testing and DNA sequencing, 6 strains, 31 strains, and a strain only had bla(TEM), bla(CphA), and bla(VIM), respectively. Two Aeromonas hydrophila each possessed bla(CphA)+ bla(CTXM-M-9), and bla(CphA) + bla(CTX-M-1) + bla(CTX-M-15-like) + bla(TEM); two Aeromonas caviae each possessed bla(NDM) + bla(CTX-M-1) +bla(CTX-M-15-like) + bla(TEM), and bla(NDM) + bla(TEM). Thirty-four of the 42 strains mentioned above were isolated from extra-intestinal. Act, aexT, and ascF-G, were in intestinal more frequently, but alt, hlyA, ela, and lip were in extra-intestinal more frequently. CONCLUSION: Aeromonas inside and outside intestinal differed in their clinical characteristics, drug susceptibility, drug resistance and virulence genes.