70 PAHO BULLETIN l vol. 15, no. 1, 1981
latter goal should be relatively easy to achieve, because in most instances the production of these agents does not require the costly infra- structures associated with production of con- ventional insecticides. Furthermore, the pro- duction of many of these promising agents is much more labor-intensive than capital- intensive, and should thus be quite suitable for the many countries of the tropical zone where labor-intensive methods are still eco- nomically feasible.
To pave the way for such developments, the
research on biological control of vectors is be- ing closely associated with special efforts to develop national expertise within endemic countries and to disseminate relevant infor- mation among those countries so that they can ultimately achieve a measure of regional or national self-reliance in controlling the vectok borne diseases that continue to plague them.
Source: World Health Organization document TDR/ PWVEC/80, 1980.
ANTIBIOTIC TREATMENT OF DIARRHEA
The use of antibioticsfor the treatment of diarrhea1 disease is controversial. The Australian National Health and Medical Research Council has recently recon- mended the following policies in an attempt to rationalize the attitude of medical practitioners on this issue. 1
Introduction
Diarrhea is a common symptom of many noninfective diseases, and sometimes it may be prominent in infections which do not pri- marily affect the bowel, e.g., malaria. It is also a frequent side-effect of drug administra- tion, including the administration of antibi- otics. In fact, antibiotic-induced diarrhea is occasionally very severe and many even cause death.
Many infective diarrhea1 diseases, such as rotavirus gastroenteritis and staphylococcal toxin food-poisoning, do not benefit from an- tibiotics. In addition, some bacterial gastroin- testinal infections such as salmonellosis are not improved by antibiotic treatment despite the in vitro sensitivity of the salmonella species strain concerned. For these reasons, antimi- crobial agents should only be prescribed for certain selected gastrointestinal infections that
‘A comprehensive list of references on which the above note has been based are available from the Editor, Com- municable Diseases Intelligence, P.O. Box 100, Woden, A.C.T. 2606, Australia.
have been shown to benefit clinically from specific chemotherapy. Accurate diagnosis of the diarrheal disease is a prerequisite for this.
Acute Diarrhea, Diagnosis Pending
Chemotherapy is rarely necessary in these circumstances. Rehydration, if necessary, is the essential measure for acutely ill patients. Immediate chemotherapy, after the collection of appropriate culture specimens, may be con- sidered for selected patients if the epidemiolo- gy strongly favors a particular etiology such as giardiasis or cholera. If salmonella food poisoning is suspected, empirical chemothera- py may be considered for patients who are prone to septicemia because of impaired defense mechanisms, e.g., immunosuppres- sion.
Salmonella Gastroenteritis
l ABSTRACTS AND REPORTS 71
monella carrier state, which is usually tempo- rary. On the contrary, the use of absorbable antibiotics such as ampicillin, co-trimoxazole, or chloramphenicol may prolong the period of excretion of salmonellae after clinical recov- ery. The same is true when nonabsorbable antibiotics such as neomycin are used.
In occasional patients with severe salmonel- la gastroenteritis and suspected or confirmed septicemia, treatment using either chloram- phenicol, ampicillin, amoxycillin, or co-tri- moxazole is indicated. One of these drugs may also be necessary if salmonella gastroenteritis develops in immunocompromised patients.
Shigella Dysen tey
Controlled shigellosis studies indicate that the use of absorbable antibiotics such as ampicillin or co-trimoxazole cause a more rapid clinical recovery and shorten the period during which shigellae are excreted. In con- trast to ampicillin, amoxycillin is relatively in- effective against this disease. This is possibly because amoxycillin is two-fold less active than ampicillin against Shigelka spp. in vitro, and also because amoxycillin is rapidly ab- sorbed, resulting in subinhibitory concentra- tions in the colon. However, most present-day data suggest that for the treatment of shigello- sis good systemic absorption of a drug is more important than the attainment of high intralu- minal concentrations; nonabsorbable antibi- otics such as neomycin are relatively ineffec- tive.
The enteritis resulting from shigellosis may vary from a mild illness to severe, often life- threatening disease; the latter is typical of in- fection caused by Shigella dysenteriae (Shiga bacil-
lus). Chemotherapy with oral or parenteral
ampicillin or co-trimoxazole is recommended for severe cases of shigella dysentery. In many parts of the world, including developed coun- tries, ampicillin-resistant shigellae are now common; these organisms may also be multi- ply resistant to tetracyclines, chlorampheni- col, and sulfonamides. Such strains now ap- pear to be prevalent in South-East Asia.
Co-trimoxazole is the drug of choice for the treatment of shigellosis caused by ampicillin- resistant strains. Chloramphenicol may also occasionally be indicated for the treatment of seriously ill patients, provided the Shigella spp. strain is sensitive to this drug. Tetracyclines are usually not recommended; however, one study in adults showed that a single oral dose of 2.5 g tetracycline was effective against shigellosis, irrespective of the sensitivity of the organism.
Most patients with a mild shigella dysente- ry, especially if the infection is caused by
Shigella sonnei, recover uneventfully without
chemotherapy. Many clinicians prefer to treat these patients by symptomatic measures alone. Apart from their clinical status, the social and physical environment of such pa- tients may sometimes be a consideration. For instance, a reduction of the duration of fecal excretion of organisms may be important when treating patients at home, where family members may be susceptible to infection.
Acute Diarrhea Caused by Escherichia coli
Certain serogroups of E. coli may be entero- toxic, causing (as in cholera) a movement of fluid into the small bowel lumen. Others may be enteroinvasive, having the ability, like shigellae, to invade the intestinal mucosa.
72 PAHO BULLETIN l vol. 15, no. 1, 1981
treatment of the not very common disease caused by enteroinvasive strains of E. coli.
Cholera
In treating this disease, correction of dehy- dration is the most important measure. Nevertheless, controlled studies show that oral tetracycline or doxycycline is effective in eradicating vibrios from stools and also in diminishing the volume and duration of diar- rhea. A three-day course of tetracycline also effectively eliminates the organisms from cholera carriers. A four-day course of co- trimoxazole has been reported as effective as tetracycline for the treatment of acute cholera. Vibrio parahaemolyticus Gastroenteritis
This is usually a relatively mild, acute, self- limiting diarrheal disease, and chemotherapy is usually not used. The organism is sensitive in vitro to the tetracyclines, but it is not known whether the administration of these drugs is of any benefit.
Campylobacter Enteritis
The majority of patients with this disease recover without any specific chemotherapy. As a result of in vitro studies, erythromycin has been suggested as the drug of choice for treatment of severe cases, but this has not yet been confirmed by clinical studies. A small percentage of campylobacter strains are erythromycin-resistant.
Traveler’s Diarrhea
The routine prophylactic use of anti- biotics for travelers to developing countries is not recommended because of possible side ef- fects and the likelihood of inducing resistant
enteric pathogens. However, in one controlled trial a 100 mg daily dose of doxycycline, given for three weeks, was very effective in reducing the frequency of traveler’s diarrhea among Peace Corps volunteers in Kenya.
Giardiasis
Metronidazole is now regarded as the drug of choice for the treatment of this infection. The recommended regimen for adults (2 g orally once a day for three days) produces a higher parasitological cure rate than standard courses of either mepacrine (quinacrine, “Atabrine”) or fin-azolidone. For severe or recurrent cases of giardiasis a more prolonged metronidazole course may be required. Tini- dazole, similar to metronidazole, is another nitroimidazole drug; it has been used in either single or multiple-dose regimens to treat giar- diasis with success. Some authors in the United States still prefer mepacrine for treat- ment of giardiasis, particularly giardiasis in children.
Amebic Dysentery
Metronidazole is a very effective drug for the treatment of all forms of amebiasis. For in- testinal infections and symptomless cyst passers, a regimen of 400-800 mg given orally three times a day for 5-10 days is now recom- mended.
As with giardiasis, tinidazole has been used for the treatment of amebic dysentery with success, but so far clinical experience with this drug is limited.
