Pathophysiology of Salmonella Diarrhea in the Rhesus Monkey: Intestinal Transport, Morphological and Bacteriological Studies

67:59- 70, 1974 Copyright© 1974 by The Williams & Wilkins Co .

Vol. 67, No.1

GASTROENTEROLOGY

Printed in U.S.A.

PATHOPHYSIOLOGY OF SALMONELLA DIARRHEA IN THE RHESUS MONKEY: INTESTINAL TRANSPORT, MORPHOLOGICAL AND BACTERIOLOGICAL STUDIES W. R. RoUT, M.D., S. B. FoRMAL, PH.D ., G. J . DAMMIN, M .D .,

AND

R. A. GIANNELLA,

M.D.

Departments of Gastroenterology and Applied Immunology, Walt er Reed Army Institute of Research , Washington, D. C.; and the Departments of Pathology , Harvard M edical School and Peter Bent Brigham H ospital, Boston, Massachusetts

Diarrhea caused by Vibrio cholerae and some Escherichia coli is the result of enterotoxin-induced abnormalities in small intestinal fluid and electrolyte transport. In contrast to these so-called " toxigenic diarrheas," the pathophys iology of diarrhea caused by bacteria which invade the gastrointestinal mucosa, but do not elaborate enterotoxin, is obscure. In vivo jejunal, ileal, and colonic water and electrolyte transport was studied in Salmonella typhimurium-infected rhesus monkeys, and alterations in transport correlated with changes in intestinal morphology and with intraluminal salmonella concentrations. In controls, net water absorption was seen in the jejunum, ileum, and colon. All salmonella-infected monkeys with diarrhea had severe colitis associated with either a marked inhibition of colonic water absorption or net colonic secret ion . In addition, monkeys with mild diarrhea had mildly impaired ileal and markedly impaired jejunal transport. In contrast, monkeys with severe watery diarrhea demonstrated net secretion in the jejunum, ileum , and colon. Sodium and chloride transport paralleled water transport in magnitude a nd direction. In the ileum, the severity of morphological damage and the intraluminal salmonella concentrations correlated with the degree of transport abnormalities a nd with the severity of the observed diarrhea . Despite a transport defect in the jejunum however, bacterial invasion was never seen, and morphological changes were minimal , as were intraluminal salmonella concentrations. These observations suggest that in salmonella-infected monkeys, mild diarrhea may be the result of the inability of the colon to reabsorb the fluid load presente d to it by the small intestine, but that severe diarrhea may be the result of profound transport abnormalities in both the jejunum and ileum superimposed on that in the colon. Unlike enterotoxin-mediated diarrheas, salmonella diarrhea seems to involve both the small and large intestine, and is regularly accompanied by both ileitis a nd colitis. The diarrhea caused by Vibrio cholerae, or by certain noninvasive strains of Escherichia coli, is the result of small intestinal secretion of water and electrolytes. 2 - 4 These

organisms do not invade the small intestinal mucosa, but elaborate enterotoxins intraluminally which sti mulate adenyl cyclase and intracellular cyclic AMP, result -

Received September 4, 1973. Accepted January 15, 1974. Presented in part at a meeting of The American Gastroenterological Association, New York, New

York, on May 25, 1973, and published in abstract form.' Address reprint requests to: Dr. R. A. Giannella, Department of Gastroenterology, University of 59

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ing in fluid and electrolyte secretion. 2 - 3 Colonic water and electrolyte transport is unaffected, and diarrhea results because the volume of fluid elaborated by the small intestine overwhelms the absorptive capacity of the colon. 2 ' 3 • 5 In contrast to these "toxigenic" diarrheas, little is known of the pathogenesis of diarrheal disorders caused by pathogenic bacteria which invade the gastrointestinal epithelium, but do not elaborate enterotoxins, e.g., Salmonella typhimurium . 6 The pathophysiology of salmonella-induced diarrhea has been studied in the rat, 7 but the relevance of the rodent model to man is uncertain. 8 Little is known, in human salmonellosis, about intestinal transport and its relation to changes in intestinal morphology and bacteriology. 9 Since these data are difficult, if not impossible, to obtain in human disease, we sought to examine the pathophysiology of salmonella diarrhea in the Rhesus monkey, a natural host of this disease. Furthermore, salmonellosis in the monkey is thought to resemble the disease as it occurs in man more closely than does salmonellosis in the various rodent models. 8 In this study, we examined the alterations of fluid and electrolyte transport in the small and large intestine of the salmonella-infected monkey . In addition, we examined the relationship of these alterations to intraluminal salmonella concentrations and to morphological changes in the intestinal mucosa.

Methods Animals . Male rhesus monkeys, Macacca mulatta, weighing 3 to 4 kg, and whose stools Kentucky School of Medicine, Lexington, Kentucky 40506. The authors wish to thank Sp5 Peter Manty and Mr. Smiley Austin for their expert technical assistance and Dr. Douglas Tang for help with statistical evaluation. In conducting the studies reported herein, the principles of the " Guide for Laboratory Animal Facilities and Care", as promulgated by the Committee on the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, National Academy of Sciences-National Research Council, were observed.

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were free from enteric pathogens, were housed in individual cages, and fed Purina monkey chow (Ralston Purina Co., St. Louis, Mo.) and water. After an overnight fast, monkeys were fed 5 x 10 10 agar grown S. typhimurium (strain TML), suspended in 20 ml of nutrient broth, via an orogastric tube. This strain was isolated from a patient with severe watery diarrhea. 9 Control monkeys were fed sterile broth. After inoculation, monkeys were allowed free access to water. Eighty per cent of challenged monkeys developed diarrhea. Controls and symptomatic monkeys were studied 48 to 72 hr later when diarrhea was at its peak. Salmonella-infected animals fell into two groups; those with mild diarrhea, defined as at least two liquid bowel movements on each of 2 successive days, and those with severe diarrhea, i.e., multiple copious watery bowel movements on each of 2 successive days. Four animals with severe diarrhea at 48 hr were allowed to recover and were studied 7 to 10 days later. When studied, diarrhea had ceased and stools were normal. These animals were termed "convalescent" monkeys. Surgical preparation . Monkeys were anesthetized with intramuscular phencyclidine hydrochloride (Sernylan, Bio-Center Laboratories, St. Joseph , Mo.), 1.0 mg per kg of body weight. Isotonic saline was infused into the femoral vein at a rate of 15 to 20 ml per hr. Blood samples were taken at the beginning and at the termination of the experiment for serum electrolyte and osmolality determinations. Serum osmolality did not (P > 0.05) change significantly during perfusion, nor were the osmolalities observed in the two disease groups significantly different from the control values or from each other. When necessary, anesthesia was maintained with intravenous sodium pentobarbital. The abdomen was opened, and the luminal contents were removed, by needle aspiration , from the proximal jejunum, distal ileum , and colon, and were then cultured. Segments (15 to 18 em) of the proximal jejunum (beginning at the ligament of Treitz), the distal ileum (immediately proximal to the ileocecal valve), and the transverse colon were isolated by transecting the bowel proximally and distally, with care to preserve the blood supply . A 2-cm section of bowel was excised from the proximal end of the isolated segments for histological study. The transected bowel proximal and distal to the isolated loops were sutured closed. The lumen of the isolated segments was rinsed with warm perfusion solution until clear and drained .

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PATHOPHYSIOLOGY OF SALMONELLA DIARRHEA

Stainless steel spools were tied into both ends of the isolated segments. The proximal spool was connected to a polyvinyl tube component of the perfusion system, while the distal spool was attac hed to a polyvinyl drainage tube. The cannu lated segments were placed into the abdominal cavity , the perfusion and collecting tubes were exited through stab incisions in the flank, and , after examining the segments to ensure that they had adequate vascular perfusion , the abdomen was closed. Perfusion technique. The segments of the jejunum, ileum , and colon were perfused simultaneously at a rate of 0.5 ml per min with a Harvard series 954 4-channel continuous automatic pump (Harvard Apparatus, Millis, Mass.). The perfusion solution, equilibrated with 5% C0 2 -95% oxygen for 30 min before and during perfusion, contained (in millimoles per liter): Na 150; K 5; Cl 125; HC0 3 30; and mannitol16. Polyethylene glycol (PEG) , 600 mg per 100 ml, was used as a nonabsorbable water marker. The pH of the perfusion solution was 7.5. The perfusion solution was kept at 37 C, and the animal's rectal temperature was maintained at 37 C with a pediatric water blanket (Gorman-Rupp Industries, Bellville, 0.). After a 2-hr equilibration period, the perfusate was separately collected for three 1-hr intervals into iced graduated cylinders, and measured to the nearest 0.1 mL At the termination of the experiment, the abdomen was reopened and the bowel examined. If a test segme nt appeared to be dilated or cyanotic, it was excluded from the study. The perfused intestinal segments were removed, the length recorded, and a 2-cm piece removed from the distal end of each segment for histological examination. The animal was then killed by intravenous overdose of sodium pentobarbitaL All chemical analyses were done in duplicate. PEG concentrations were determined by a modification of Hyden 's turbidimetric method 10 ; sodium and potassium concentrations by flame photometry; chloride by coulometric titration; osmolality by freezing point depression; and total protein estimated by the method of Warburg and Christian. 11 Net fluxes of water and electrolytes were calculated from changes in the concentration of PEG by standard formulae. 12 PEG recoveries in all segments studied were greater than 95%. Values for transport were expressed as microliters or microequivalents per hour per 15 em of boweL Each 60-min perfusion period was analyzed separately, and the mean value for the three 1-hr perfusion periods calcu lated. Negative values signify absorption, net

61

lumen to blood transport, while positive values signify secretion, net transport from blood to lumen. Bacteriology. Stool samples were cultured twice daily during the 48 to 72 hr prior to perfusion. At the time of perfusion, salmonella concentrations in the jejunum, ileum, and colon were quantitated. Luminal contents were serially diluted in broth, and the various dilutions were plated in duplicate on MacConkey agar. Lactose negative colonies were enumerated and confirmed to be S. typhimurium by slide agglutination using specific antisera. 6 Numbers of salmonellae are expressed as the geometric mean (log 10 ) per gram of intestinal content. Histology. Specimens for histological study were fixed in 10% buffered formalin, processed for light microscopy, and stained with hematoxylin and eosin stain and Giemsa stain. Coded slides were read by one of the authors (G. J.D.) who had no knowledge of the history of the monkey from which the specimen was obtained. Statistical evaluation. All data are expressed as mean ± 1 SE. Transport data were subjected to statistical analysis by utilizing the KruskalWallis analysis of variance, 13 and bacterial flora were analyzed by Student's t-test. 14 Correlation between intestinal protein concentration and water transport was calculated by linear regression by least squares. 14

Results Net transport of water and electrolytes. In control monkeys (fig. 1), net water absorption was observed in the jejunum, ileum, and colon, i.e., -799 ± 136, -1500 ± 232, and - 1389 ± 290 J.Lliters per hr per 15 em, respectively. In monkeys with mild diarrhea , a marked decrease (P < 0.01) in net water absorption was noted in the jejunum (-39 ± 150), and colon (-55± 209). In addition, mean net ileal transport was reduced in 4 of 6 animals studied. However, because of the variability observed among these animals, the mean value ( -639 ± 538) was not statistically different from controls (P > 0.05). In animals with severe diarrhea, the defect in net water transport was even more marked. A striking reversal (P < 0.01) of net water transport, from absorption to secretion, was observed in all three intestinal sites. The net secretory rate in the jejunum was + 182 ± 27, in the ileum it was + 1797 ±

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NET SODIUM 255, and in the colon it was + 547 ± 209. Jejunum Ileum In all monkeys studied, in the control 300 animals as well as in those with diarrhea, net small intestinal and colonic sodium and chloride transport paralleled net water transport in both magnitude and direction (fig. 2). There was negligible net movement of potassium in the jejunum and ileum, in e either the control or diarrheal animals. In ] 100 t he colon, however, net potassium secretion was observed in control animals, and 200 <.001 was significantly (P < 0.05) decreased (fig. 3) in animals with severe diarrhea. Intestinal protein concentrations and protein secretion (table 1). To assess the NET CHLORIDE possibility that secretion might be due to Co lon exudation of f1uid from the inf1amed 300 injured bowel, protein concentrations in the perfusate were measured, and the -~ 200 amount of protein secreted was calcu7 lated. There was no increase in jejunal or ileal protein concentration. Although mean colonic protein concentrations were e increased, these were not statistically sig] 100 nificant. The amount of protein secreted in 20 0 ~Mild Dia rrhea <.01 infected animals also was not significantly Severe Diarrhea greater than in controls animals. Both the protein concentrations and the amounts of FIG. 2. Net intestinal sodium and chloride transprotein secreted are 5 to 14 times less than port in control and salmonella-infected monkeys. The 0

0

a

Jejunum

Ileum

Colon

size of each group is denoted by the number at the base of each bar. P values determined by comparison with controls.

c

.S!

e~

800

,

0

..0

J:

<(

'

~ ~

u

"''

0

w0" 0-

400 E


0

~

':;_ c

400

·~ ~

.,u Ul

800 1600

~

M i ld Diarrhea

Severe Diarrhea

2000

9 <.01

Net intestinal water transport in control and salmonella-infected monkeys. The size of each group is denoted by the number at the base of each bar. P values determined by comparison with controls. FIG. 1.

FIG. 3. Net intestinal potassium transport in control and salmonella-infected monkeys. The size of each group is denoted by the number at the base of each bar. P values determined by comparison with controls.

the values expected if an exudative process were occurring. 7 Furthermore, there was no correlation between intestinal protein concentration and alteration in water trans-

July 1974 TABLE

PATHOPHYSIOLOGY OF SALMONELLA DIARRHEA

1. Intes tinal protein concentrations and protein sec retion in control and salmonella-infect ed monkey sa

Concentration Jejunum

Secret ion

Il eum

Colon

J ejunum

Il eum

mg/ml

Control (7) Mild di arrhe a (6) . Seve re dia rrh ea (5) a

63

M ea n

± SE.

0.17 0.08 0 .06

± ± ±

0.05 0.06 0.04

0.08 0.09 0.08

± ± ±

0.03 0.05 0.06

Colon

mg/hr/15 em

0.10 0.24 0.16

± ± ±

0 .02 0.09 0.06

5 .0 4 .6 2. 2

± ± ±

1.4 1.0 0.6

2.0 3.2 4. 2

± ±

0.9 0.9

± 1.1

3.2 ± 0.5 9. 1 ± 4.7 5.5 ± 3.2

The number of samples is given in parentheses beside each group.

port in the jejunum, ileum, or colon (r = 0.2498. O.Ofi98, and 0.0264, respectively). Bacteriology (fig . 4) . Control monkeys were free from enteric pathogens. Of the sa lmonella-inoculated monkeys that developed diarrhea, 100% had the organism isolated from their stools . Only 60% of the asymptomatic monkeys fed S. typhimurium had positive stools. Salmonella were present in the jejunum, ileum, and colon of both groups of diarrheal animals. In the monkeys with mild diarrhea, the concentration of salmonella increased from the jejunum ( 1. 7 ± 0.9 log 10 organism per g of intestinal content) to the ileum (3.6 ± 0.9), to the colon (5.5 ± 0.7). In monkeys with severe diarrhea there was a significant increase in the number of salmonella isolated from the ileum (7 .3 ± 0.2; P < 0.01) and colon (7.6 ± 0.3; P < 0.02). Jejunal salmonella concentration remained unchanged (2.9 ± 1.1; P > 0.05) . Thus, in the ileum and colon, there was a correlation between the number of intraluminal salmonella, the magnitude of the water transport abnormality, and the severity of the diarrhea. Morphological alterations . The perfusion procedure did not result in any striking morphological alterations in either the small or large intestine. The only change attributable to the perfusion was dilation of small intestinal lacteals (figs . 5B and 6A). Alterations in jejunal morphology in salmonella-infected animals with either mild or severe diarrhea were minimal (fig. 5B; contrast with 5A). Villi were shortened, and demonstrated an increase in mononuclear cells in the epithelial layer, but there was no apparent abnormality of the villus epithelial cells. Villi appeared edematous with an increase in cellularity of the

JEJUNUM

~ MILD

~ DIARRHEA (6)

M

SEVERE io...IIDIARRHEA (6)

FIG. 4. Comparison of intestinal salmonella concentra tions in monkeys with mild or severe diarrhea.

lamina propria, but there was no increase in polymorphonuclear neutrophils (PMN). Crypts were mildly elongated with the deeper crypt areas showing increased mitotic activity. There was a reduction in mucus content in the goblet cells of both the villi and crypts, especially the crypts. Bacterial invasion of the jejunal mucosa was never seen. In contrast, alterations in ileal morphology were striking and varied, depending upon the severity of the diarrhea. In animals with mild diarrhea (fig. 6A,), villi were edematous, bulbous, and shortened, the crypts were elongated, and the lamina propria contained many PMN. Villus epithelial cells were shortened and demonstrated loss of basal polarity of nuclei. Ulceration was not seen, but the epithelium was invaded by bacilli (studies on some monkeys using the fluorescent antibody technique have shown that these bacilli are indeed S. typhimurium) (fig. 7A). In animals with severe diarrhea, (fig. 6B) ileal abnormalities were even more

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striking. Mucosal architecture was distinctly abnormal with flattened villi, elongated crypts containing numerous mi croabscesses, reduced mucus content of villus and crypt cells, and a markedly edematous lamina propria densely infiltrated with PMN. The villus epithelial

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cells were shortened and attentuated, hyperchromatic, and arranged in a disordered fashion. Although increased exfoliation was apparent, ulcerations were rarely seen. Salmonellae were seen in moderately large numbers within the mucosa (fig. 7A). All monkeys with salmonella diarrhea,

FIG. 5. A, control jejunum. This is essentially normal except for a slight increase in crypt depth. B, jejunum in mild diarrhea. Villi are edematous and slightly reduced in height. Interepithelial cells and cellularity of the lamina propria are increased. Slight elongation of the crypts (Giemsa, x 120) .

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65

FIG. 6. A, ileum in mild diarrhea. Interepithelial cells include polymorphonuclear neutrophils as well as mononuclear cells. There is slight disorientation of the epithelial cells. Villi are edematous and shortened and the crypts are elongated with reduced mucus in the epithelial cells. B, ileum in severe diarrhea. Villi are markedly shortened, edematous and contain polymorphonuclear neutrophils in the epithelium and the lamina propria. Villus epithelial cells are deformed. Crypts are elongated, and in some areas crypt cells are damaged by a pyogenic process (arrows). Mucus is absent from both villus and crypt goblet cells (Giemsa, x 180) .

either mild or severe, demonstrated a severe acute colitis (fig. 8B). Grossly, the entire colon appeared equally involved, but only the perfused transverse colon was

histologically examined. Histological involvement ranged from a diffuse acute colitis to a more severe process, characterized by multifocal areas of microabscess

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formation and epithelial disruption . In general, the surface epithelium was attenuated, crypts microabscesses were abundant, and the lamina propria was edematous and diffusely infiltrated with

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PMN . With higher magnification , salmonellae were seen invading both the epithelial cells and the lamina propria (fig. 7B). Ulcerations were only occasionally seen.

FIG. 7. A , ileum in severe diarrhea. Villus tip showing abnormal epithelial cells at the top with migrating intraepithelial cells, edema of the lam ina propria, and a cluster of b acilli (a rrows). This formation suggests an in tracellu lar propagation. B, colon in diarrhea. Epithelium is abnormal. Cells lack mucus, and those at upper left are cuboidal. Lamina propria is edematous and contains a cluster of approx imately 20 bac illi (arrows). Despite their arrangement, they appear to be extracellular (Giemsa, x 1500).

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67

FIG. 8. A, control colon . This is essentially norm al. B, colon in diarrhea. Surface epithelium is intact but abnormal in t hat cells are cuboidal to flat an d lack mu cus. There is focal dilation of crypt glands with discontinuity rel ated to a small mucosal abscess (arrow). The lam ina propria is edematous and increased in cellularity (Giemsa, x 180) .

Convalescent studies. In the 4 convalescent monkeys studied 10 to 14 days after initiation of infection, small and large intestinal fluid and electrolyte transport were normal, and jejunal, ileal, and colonic morphology were indistinguishable from control specimens. In spite of this prompt

morphological and physiological recovery, S. typhimurium was still recovered from the ileum and colon in substantial concentrations: 3.3 ± 1.3 and 5.8 ± 0.7 organisms per g (log, 0 ) , respectively. However, S. typhimurium was not recovered from the jejunum of any of these animals .

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Discussion In this study, the most consistent abnormalities in fluid and electrolyte transport were observed in the jejunum and colon. Regardless of the severity of the diarrhea, all salmonella-infected monkeys demonstrated severe colitis associated with either a marked inhibition of fluid absorption in animals with mild diarrhea, or net colonic secretion in those animals exhibiting severe diarrhea. In addition to the colonic defect, monkeys with mild diarrhea had severely impaired jejunal and moderately impaired ileal transport. Monkeys with severe diarrhea, however, exhibited net secretion of fluid in the jejunum and ileum as well as the colon. The alterations in ileal and colonic transport were always associated with bacterial invasion of the mucosa, which was most pronounced in the ileum and colon of those animals with severe diarrhea. The more severe transport defects observed in the ileum and colon of animals with severe diarrhea were paralleled by a significant increase in the intraluminal salmonella concentration in these sites. As in this study, previous intestinal perfusion studies of salmonella-infected rats revealed that alterations in ileal transport correlated with the severity of the ileitis and with the clinical diarrheal state of the animal. 7 There was no apparent correlation, in this study, between the intensity of the colonic inflammatory process and the magnitude of the colonic transport defect. A similar observation was noted in salmonellainfected rats, since there was no alteration of colonic transport despite the presence of severe cecal inflammation. 7 In salmonella-infected monkeys, fluid loss per unit length of intestine in the ileum was greater than in the jejunum. This pattern differs from that observed in human cholera 15 and E. coli diarrhea, 16 but is similar to that observed in tropical sprue. 17 The greater ileal secretory component in salmonellosis may relate to either the greater concentrations of salmonellae in the ileum, and/or the character of the morphological damage seen in the ileum,

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as compared with the jejunum. Specifically, it may be due to the relatively greater damage to the villus or absorptive mucosa versus the crypt or secretory mucosa of the ileum. We have previously reported that, in the rabbit ileum, S. typhimurium must invade the epithelium to induce fluid secretion, but that invasion alone is not sufficient stimulus for fluid secretion. 6 Thus, the bacterial-host interaction in salmonellosis differs from that which occurs in cholera and some E. coli infections. We have been unable to detect a "salmonella enterotoxin," and what occurs after invasion to evoke fluid secretion is not known. 6 Fluid secretion may be the result of active epithelial secretion, impaired epithelial absorption, or a passive transport process through a damaged mucosa. The invasive nature of S. typhimurium and the resultant extensive mucosal inflammatory process are consistent with this latter possibility. The lack of a significant concentration of protein in the perfusate, and the absence of a correlation between perfusate protein concentration and alterations in water transport, make a transudativeexudative mechanism less likely. In addition, our previous studies of in vitro ion transport in isolated strips of salmonella-infected rabbit ileum have demonstrated that fluid secretion is primarily the result of alterations of various active ion transport processes. 18 Salmonella-infected ileum behaved similarly to cholera toxinexposed ileum. There was an inhibition of active sodium absorption and stimulation of active chloride secretion. The changes observed in cholera are mediated by the adenyl cyclase-cyclic AMP system. 2 - 4 Whether the same active transport mechanisms account for the jejunal, ileal, and colonic secretion seen in the salmonellainfected monkey must await further study. Although net jejunal fluid transport was abnormal in monkeys with mild or severe diarrhea, bacterial invasion of the mucosa was not seen, and both morphological changes and intraluminal salmonella concentrations were minimal. A similar defect in jejunal fluid and electrolyte transport, in

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PATHOPHYSIOLOGY OF SALMONELLA DIARRHEA

the absence of jejunal morphological abnormalities, has been observed in ulcerative colitis 19 and in Shigella flexneri 2a-infected rhesus monkeys (unpublished observations). It is possible that an as yet undetected enterotoxin is responsible for the alterations in jejunal fluid and electrolyte transport observed in this study. Alternatively, the jejunal defect may be the result of a "colonic or ileal factor" released by an extensively damaged ileum or colon. The colon, and other segments of the intestine are rich in prostaglandins. 20 • 21 Prostaglandins are released from various inflamed tissues. 21 Circulating prostaglandins can result in net jejunal and ileal secretion. 22 ' 23 Therefore, the possibility that prostaglandins may mediate the observed abnormalities in fluid and electrolyte transport must be considered. Salmonella-induced diarrhea in the rhesus monkey is due to transport alterations in the colon, as well as in the small intestine. Although the colon normally absorbs greater than 95% of the water entering it from the small intestine, z., 25 this function was impaired in all diarrheal animals, and net colonic secretion was seen in most. Thus, in monkeys with mild diarrhea, the diarrhea may be the result of the inability of the colon to absorb fluid entering it from the small intestine. Severe diarrhea may be the result of profound transport abnormalities occurring in both the jejunum and ileum superimposed on that in the colon. To what extent these findings in monkeys can be extrapolated to human salmonellosis is uncertain. Although salmonellosis is estimated to occur in 2 million Americans yearly, 26 little is known of the disease process in man. However, our observations in the monkey, as well as those of Kent et al. 8-that the colon is consistently involved-are similar to those of Boyd 27 who found similar colonic lesions at autopsy in each of 6 fatal human cases of salmonellosis due to S. typhimurium. Whether the physiological abnormalities observed in this study are also similar to those occurring in man is not known and must await human perfusion studies.

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17. Banwell JG, Gorbach SL, Mitra R, et al: Tropical Sprue and malnutrition in West Bengal. II. Fluid and electrolyte transport in the small intestine. Am J Clin Nutr 23 : 1559-1568, 1970 18. Fromm D, Giannella RA, Formal SB, et al: Active ion transport across isolated ileum invaded by salmonella. Gastroenterology 66:215-225, 1974 19. Binder HJ, Ptak T : Jejunal absorption of water and electrolytes in inflammatory bowel disease. J Lab Clin Med 76:915-924, 1970 20. Bennett A, Fleshier B : Prostaglandins and the gastrointestinal tract. Gastroenterology 59:790800, 1970 21. Waller SL: Prostaglandins and the gastrointestinal tract. Gut 14:402-417, 1973 22. Cummings JH, Newman A, Misiewicz JJ, et al: Effect of intravenous prostaglandin F ,. on small

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intestinal function in man. Nature 243:169-171, 1973 Matuchansky C, Bernier JJ: Effect of prostaglandin E, on glucose, water, and electrolyte absorption in the human jejunum. Gastroen· terology 64:1111-1118, 1973 Levitan R, Fordtran JS, Burrows BA, et al: Water and salt absorption in the human colon. J Clin Invest 41:1754-1759, 1962 Phillips SF, Giller J: The contribution of the colon to electrolyte and water conservation in man . J Lab Clin Med 81:733-746, 1973 Aserkoff B, Schroeder SA, Brachman PS : SaJ. monellosis in the United States. A 5 year review. Am J Epidemiol 92:13-24, 1970 Boyd JF: Salmonella typhimurium, colitis, and pancreatitis. Lancet 2:901-902, 1969