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Letter
Aeromonas
spp. and Infectious Diarrhea, Hong Kong
Stewart Siu-Wa Chan*
and King Cheung Ng*
*The Chinese University of Hong Kong, Hong Kong
Suggested citation
for this article:
Chan SS, Ng KC. Aeromonas spp. and infectious diarrhea, Hong
Kong [letter]. Emerg Infect Dis [serial on the Internet]. 2004 Aug [date
cited]. Available from: http://www.cdc.gov/ncidod/EID/vol10no8/03-0518.htm
To the Editor: Vila et al. reported the prevalence of Aeromonas
spp. associated with traveler’s diarrhea in Spain (1).
Some of the patients described in this study had traveled to countries
in Asia, such as Thailand and India. This report details the prevalence
of this pathogen in patients with acute infectious diarrhea who were treated
in emergency department settings in Hong Kong.
Over a 12-month period, we retrospectively studied all adult patients
who showed clinical features of acute infectious diarrhea, were treated
as outpatients with or without observation in the emergency department,
and had a positive stool culture (2–4). Our data were
collected at an urban university-affiliated hospital with 1,400 beds and
an emergency department with an annual census of 190,000 patient visits.
Aeromonas spp. were isolated from stool samples by standard culture
procedures, which included introduction onto xylose lysine desoxycholate
agar plate and thiosulphate citrate bile sucrose plate, and subsequent
screening by triple iron sugar slant (acid butt with no H2S),
positive oxidase, negative urease, fermentation of mannitol but not dulcitol
and inositol, resistance to vibriostatic agent 0/129, and ability to grow
at 0% NaCl. The main species of Aeromonas were identified by the
differential biochemical reactions of gas production from D-glucose, arginine
dihydrolase, ornithine and lysine decarboxylase; esculin hydrolysis; Voges
Proskauer reaction; fermentation from arabinose, sucrose, mannitol, salacin,
and D-sorbitol; and citrate and glycerol utilization (5).
Of 130 patients with positive stool cultures, Aeromonas spp. were
isolated in 9 patients (6.9%), including A. caviae in 4 patients,
A. hydrophila in 2 patients, and A veronii in 3 patients.
The cases were not epidemiologically linked. In one of these isolates
(A. caviae), another enteropathogen (Vibrio parahemolyticus)
was also isolated. None of the patients reported recent travel abroad
or to mainland China before treatment.
Our review of the clinical features of these nine patients found that
the mean highest body temperature at the time of treatment or during the
patient’s stay in the emergency department was 37.4°C (95% confidence
interval [CI] 36.9–38.0). Two patients (both with A. caviae isolated)
had temperatures >37.5°C. Bloody diarrhea was present in two patients
(one with A. veronii and one with A. caviae). The mean number
of unformed stools per day was 8.6 (95% CI 4.0–13.2). Abdominal pain in
eight patients and vomiting in four patients was reported. Five patients
required admission to the emergency department’s observation unit before
discharge. Of these, four patients needed intravenous fluid therapy. Empiric
ciprofloxacin was given to one patient with a temperature of 38.3°C.
Stool culture results were available within 3 days for positive isolation
of Aeromonas. All Aeromonas strains were susceptible to
ciprofloxacin, cefotaxime, cotrimoxazole, and chloramphenicol, while two
of nine isolates (one A. caviae strain and one A. hydrophila
strain) were susceptible to ampicillin. All patients had recovered satisfactorily
by the time stool culture results were available, and antimicrobial therapy
was not necessary, except for the patient who was given ciprofloxacin
empirically.
In conclusion, Aeromonas spp. are responsible for a small proportion
of cases of bacterial gastroenteritis encountered in an urban emergency
department setting in Hong Kong. Patients affected do not necessarily
have a history of travel to a nonindustrialized region. In a substantial
proportion of cases, the symptoms are severe enough to require intravenous
fluid therapy and observation. However, symptoms generally would have
resolved by the time the pathogen was isolated from stool culture. In
contrast to the report of Vila et al., persistent diarrhea is uncommon,
and antimicrobial therapy is usually unnecessary in our particular setting.
Aeromonas spp. are susceptible to a wide range of antimicrobial
drugs, except ampicillin. Whether empiric antimicrobial drugs given at
the time of treatment would have significantly shortened the duration
of the symptoms is not known.
References
- Vila J, Ruiz J, Gallardo F, Vargas M, Soler L, Figueras
MJ, et al. Aeromonas spp. and traveler’s diarrhea: clinical features
and antimicrobial resistance. Emerg Infect Dis [serial online]. 2003
May [accessed on July 3, 2003]. Available from: http://www.cdc.gov/ncidod/EID/vol9no5/02-0451.htm
- Chan SSW, Ng KC, Lyon DJ, Cheung WL, Cheng AFB, Rainer TH. Acute
bacterial gastroenteritis: a study of adult patients with positive stool
cultures treated in the emergency department. Emerg Med J. 2003;20:335–8.
- Ng KC, Chan SSW, Lyon DJ, Cheung WL, Cheng FB, Rainer TH. Acute bacterial
gastroenteritis in adult patients treated in the emergency department
of a regional hospital. The Fifth Annual Scientific Meeting of the Hong
Kong Society for Infectious Diseases, March 31, 2001; Hong Kong. Abstract
(Free Papers): 23.
- Chan SSW, Ng KC, Lyon DJ, Cheung WL, Rainer TH. Empiric antibiotics
for acute infectious diarrhoea. The Hong Kong Practitioner. 2001; 23:430–7.
- Murray PR, Baron EJ, Jorgensen JH, Pfaller MA, Yolken RH. Manual
of clinical microbiology. 8th ed. Washington: ASM Press; 2003.
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