Antimicrobial susceptibilities ofAeromonas species andPlesiomonas shigelloides

Susceptibilities of motile Aeromonas sp. to antimicrobial agents

Resistance to antimicrobial agents of 106 isolates of motile Aeromonas sp. was characterized. The results indicated that in vitro susceptibilities among the three species of the motile Aeromonas sp. were similar, and only the distribution of susceptibility to cephalothin was different. The percentage of resistance of A. sobria strains was lower than the percentage of the resistant strains of A. hydrophila and A. caviae. All of the isolates were susceptible to kanamycin, nalidixic acid, tobramycin, amikacin, netilmicin, cefuroxime, ceftriaxone, cefoperazone and cefotaxime. Three of the tested strains (two A. hydrophila and one A. caviae) transferred resistance plasmids to the Aeromonas hydrophila recipient.

Aeromonas as a human pathogen

Although the first Aeromonas strain was described by Zimmermann as early as in 1890, it took 60 years until Caselitz established human pathogenicity of strains then called "Vibrio jamaicensis". Since then, and especially in the last 10 years, there have been increasing numbers of reports on different infections caused by members of the genus Aeromonas. These include sepsis; meningitis; cellulitis; necrotizing fasciitis; ecthyma gangrenosum; pneumonia; peritonitis; conjunctivitis; corneal ulcer; endophthalmitis; osteomyelitis; suppurative arthritis; myositis; subphrenic abscess; liver abscess; cholecystitis and/or ascending cholangitis; urinary tract infection; endocarditis; ear, nose, and throat infections; balanitis; etc. The role of Aeromonas in gastrointestinal disease is very controversial. Increasing epidemiological data suggest that these organisms play a major role in enteric infections, but so far enteropathogenicity has not been demonstrable in experiments where volunteers were given high numbers of Aeromonas possessing different virulence factors. Virulence factors include hemolysin(s), enterotoxin(s), hemagglutinins, invasivity, and others; but these are not found more frequently in strains isolated from patients with diarrhea than from healthy controls. Whether there is a correlation between species and disease remains to be elucidated and requires more information about the taxonomy of this genus.