Aeromonas Wound Infections Associated with Outdoor
Activities -- California
Aeromonas species are associated with gastroenteritis and with
wound infections, particularly wounds incurred in outdoor
settings. On May 1, 1988, isolates of Aeromonas became reportable
in California, the first state to mandate reporting of isolates
of and infections with these organisms. Surveillance data for
1988 and 1989 represent the first population-based estimates of
both the occurrence and public health impact of Aeromonas
infections in the United States and provide a basis for assessing
the need for further surveillance of these organisms.
From May 1, 1988, through April 30, 1989, clinicians and
clinical laboratories in California reported 225 Aeromonas
isolates from 219 patients. Cases were reported on Confidential
Morbidity Report cards to local health departments, which then
conducted case investigations and forwarded their reports to the
California Department of Health Services. Of the 225 isolates,
178 (79.1%) were recovered from stool, 19 (8.4%) from wounds, 11
(4.9%) from blood, and 17 (7.6%) from other sites. A. caviae was
recovered from seven stool cultures; A. sobria was recovered from
two stool cultures and one vaginal culture. All other cultures
were reported as A. hydrophila or Aeromonas unspecified.
Based on reported cases, the incidence of Aeromonas wound
infections in California was 0.7 per million population. Of the
19 patients with wound infections, 13 were injured outdoors
(Table 1). Six of these patients required hospitalization for
their injuries and/or infections. One patient had a mixed
infection including Aeromonas, Proteus, and Pseudomonas species.
The number of infections peaked in the summer months with three
cases each in July and August. The cases reported among persons
aged 30-39 years represented the highest incidence rate for all
age groups (1.4 per million).
Reported by: SB Werner, MD, Infectious Disease Br, GW Rutherford,
III, MD, State Epidemiologist, California Dept of Health Svcs.
Div of Field Svcs, Epidemiology Program Office; Enteric Diseases
Br, Div of Bacterial Diseases, and Epidemiology Br, Hospital
Infections Program, Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: Aeromonas species are gram-negative,
facultatively anaerobic bacteria found in soil and fresh and
brackish water worldwide (1). Although Aeromonas species were
recognized in 1891 as colonizers and pathogens of cold-blooded
animals, especially fish (2), they were not identified as human
pathogens until 1968 (3). Since then, they have been associated
with a wide spectrum of human diseases (especially in
immunocompromised patients), most commonly gastroenteritis (4)
and soft tissue infections (5).
The taxonomy of Aeromonas species requires further
clarification. Three species, A. hydrophila, A. sobria, and A.
caviae, have been associated with human disease (4), but DNA
hybridization analyses support seven or more distinct genotypes
(6). Because many clinical laboratories are unable to perform
precise identification, many aeromonad isolates are reported as
hydrophila or A. hydrophila complex.
Although the California surveillance data provide limited
information about the morbidity of the wound infections reported,
they suggest that the public health impact of these soft tissue
infections is low and may be determined more by the nature of the
underlying injury than by the presence of Aeromonas organisms.
The California data do not provide information on case
management. However, one reported case series (7) suggests that
surgical debridement is an important component of treatment and
has enabled resolution of the infection when either no
antibiotics or ineffective antibiotics (i.e., antibiotics to
which the organisms were resistant) were used. These findings, as
well as the occurrence of Aeromonas organisms in mixed
infections, suggest that in some cases Aeromonas species may be
colonizers in wounds rather than pathogens.
References
Von Graevenitz A. Aeromonas and Plesiomonas. In: Lennette EH,
Ballows A, Hausler WJ, Shadomy HJ, ed. Manual of clinical
microbiology. Washington, DC: American Society for Microbiology,
1985:278-81.
Ewing WH, Hugh R, Johnson JG. Studies on the Aeromonas group.
Atlanta, Georgia: US Department of Health, Education, and
Welfare, Public Health Service, Communicable Disease Center,
1961.
Von Graevenitz A, Mensch AH. The genus Aeromonas in human
bacteriology: report of 30 cases and review of the literature. N
Engl J Med 1968;278:245-9.
Holmberg SD, Schell WL, Fanning GR, et al. Aeromonas
intestinal infections in the United States. Ann Intern Med
1986;105:683-9.
Janda JM, Duffey PS. Mesophilic Aeromonads in human disease:
current taxonomy, labo ratory identification and infectious
disease spectrum. Rev Infect Dis 1988;10:980-97.
Popoff MY, Coynault C, Kiredjian M, Lemelin M. Polynucleotide
sequence relatedness among motile Aeromonas species. Curr
Microbiol 1981;5:109-14.
Isaacs RD, Paviour SD, Bunker DE, Land SDR. Wound infection
with aerogenic Aeromonas strains: a review of twenty-seven cases.
Eur J Clin Microbiol Infect Dis 1988;7:355-60.
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