Enteropathogen

No. (%)b of Patients

Salmonella (not S. typhi)

7 (1.6)

Campylobacter

2 (0.5)

a Bacterial enteropathogens were identified in 214 (49.5%) of the 432 stool samples collected.

b The total percentage of isolates is higher than the percentage of patients with an identified enteropathogen because 36 patients had mixed infections.

c Two patients had mixed heat-labile and heat-stabile enterotoxigenic E. coli infections, with individual colonies producing either heat-labile or heat-stable toxin alone.

SOURCE: Reprinted with permission from Hyams et al. 1991.

Hyams and colleagues tested E. coli-like organisms for heat-labile and heat-stabile toxin by using alkaline phosphate-conjugated oligonucleotide DNA probes and Y-1 adrenal cell and suckling-mouse assays (Hyams et al. 1991). Later, Wolf and colleagues further analyzed the Hyams et al. ETEC isolates for their toxin distribution, and other factors (Wolf et al. 1993). A given strain of ETEC may produce heat-labile enterotoxin (LT), heat-stabile enterotoxin (ST), or both. LT is nearly identical with the toxin that causes cholera. Some 85% of 132 ETEC isolates from 124 symptomatic Gulf War troops produced LT (Table 4.4).

TABLE 4.4 Toxin distribution Among 132 ETEC Isolates from 124 US Troops with Gastroenteritis during Operation Desert Storm

Toxin

No. (percentage) of isolates

LT and ST

59 (45)

LT

53 (40)

ST

20 (15)

SOURCE: Adapted with permission from Wolf et al. 1993.

Antimicrobial susceptibility. Using the disk-diffusion method, Hyams and colleagues determined which of five antibiotics would most effectively treat the strains of ETEC and Shigella identified in the stool cultures. Up to 63% of the ETEC and up to 85% of the Shigella specimens were resistant to several of the antibiotics most accessible to clinicians in the field (Table 4.5), including trimethoprim-sulfamethoxazole, the antibiotic most frequently used to treat diarrhea during the early stages of ODSh deployment. In contrast, the scientists found, ETEC and Shigella were 100% susceptible to ciprofloxacin and norfloxacin. Hyams and colleagues reported that empiric results of antibiotic treatment for diarrheal disease in the field led military clinicians to gravitate toward ciprofloxacin and norfloxacin over time. Clinicians also reportedly administered quinolone drugs to affected critical combat troops to shorten the duration of gastroenteric symptoms.

TABLE 4.5 Antimicrobial Resistance of Enterotoxigenic E. coli and Shigella Specimens

 

Proportion of Resistant Specimens, %

Antibiotic

Enterotoxigenic

E. coli (N = 125)

Shigella

(N = 113)

Trimethoprim-sulfamethoxazole

39

85

Tetracycline

63

68

Ampicillin

48

21

Ciprofloxacin

0

0

Norfloxacin

0

0

SOURCE: Adapted with permission from Hyams et al. 1991.



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