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SUMMARY Experimental oral infection of seven lambs with S. infantis , designed to determine the pathogenesis of infection and evaluate the efficacy of diagnostic procedures, is described. Clinical disease occurred in one lamb given 2 × 10 11 organisms and two of six lambs given 2 × 10 10 organisms. Observations were made on the clinical pathology, bacteriology and serology during the course of infection and extensive bacteriological examinations were undertaken at post-mortem examination on the lambs which were slaughtered serially during the course of infection.

The fate of Salmonella infantis, Staphylococcus oureus, and Hafnia alvei inoculated onto vacuum packaged and polyvinylchloride (PVC) packaged fresh beef plate pieces after 0, 3, 7, 14, 21, and 28 days of storage at 1.7°C was investigated. Aerobic plate counts (APC's) of representative beef pieces were also monitored during storage and the effect of heat shrinking on both inocula and APC's in vacuum packaged samples determined. APC's of vacuum packaged beef pieces increased slower and attained lower final numbers than did PVC wrapped pieces. Levels of S. infantis in PVC and vacuum packaged samples declined at similar rates during 28 days of storage with overall decreases of 52 and 55%, respectively. The most rapid decreases occured during the first week of storage. S. aureus levels in PVC and vacuum packaged samples declined at similar rates during 28 days of storage with overall decreases of 90 and 80%, respectively. H. alvei increased in numbers by approximately 4.45 and 4.60 log cycles per gram in vacuum and PVC packaged beef pieces, respectively, during 28 days of storage. Levels of inocula in vacuum packaged samples were significantly lower initially and during storage than respective inocula in PVC packaged samples. Heat shrinkage of vacuum packages had no significant effect on levels of inocula or subsequent APC's.

Six-month-old cockerels and point-of-lay pullets were infected orally with S infantis (1 × 1010). The cockerels were slaughtered at intervals up to 42 days, and the pullets slaughtered 20 weeks, after infection. Infection produced no clinical disease and minimal changes were observed at autopsy. Serological responses were transient, frequently absent three to six weeks after infection, no response at all being recorded in some birds. Faecal excretion was observed most frequently during the early stages of infection. There was no evidence of egg transmission.

Summary The effect of zinc bacitracin on the growth of Salmonella infantis in the intestine of experimental orally infected 2-day-old broiler chicks was studied. At the age of 5 weeks the chicks which had received zinc bacitracin showed a lower incidence of salmonellae than those in the control group. Chicks pretreated with the intestinal flora of adult fowls (Callus domcsticus), whether receiving zinc bacitracin in the feed or not, were equally resistant against the colonization of S. infantis as compared with chicks which had no such pretreatment. The intestinal flora of adult fowls cultured in vitro, with or without zinc bacitracin, prevented the colonization of S. infantis, while flora from the same source cultured with tetracycline hydrochloride lacked this effect.

SUMMARYThe purpose of this work was to study the effects of interrupted, continuous and post-salmonella inoculation treatment with furazolidone in the feed on the colon-ization of Salmonella infantis in the intestines of chickens, as well as the influence of furazolidone in vitro on the effect of a mixed culture used for the prevention of salmonellosis in chickens.It was shown that chickens given interrupted treatment with 0·01% furazoli-done had significantly more salmonellas in the caeca than either chickens fed continuously with this drug or chickens without any treatment. The use of 0·01% furazolidone after inoculation with Salmonella infantis had no effect on Salmonella infantis in the caeca of chickens.The mixed bacterial culture from the normal intestinal flora lost its preventive effect on salmonellosis when cultured with 0·01% furazolidone.

Effects of storage at 5 ad -18 C for up to 28 days and high and low inoculation levels on survival of Salmonella infantis and Staphylococcus aureus on smoked broiler halves were investigated. S. infantis and Staph. aureus counts were significantly reduced during storage. The reduction in counts of S. infantis could not be attributed solely to either temperature or inoculation levels. Storage at 5 C significantly (P less than .05) reduced Staph. aureus counts on smoked broiler halves as compared to storage at -18 C. For Staph. aureus, low inoculation levels (10(3) to 10(4) organisms/ml) resulted in significantly higher mortality rates than did high inoculation levels (10(7) to 10(8) organisms/ml). At both storage conditions and inoculation levels, Staph. aureus was able to maintain higher populations than S. infantis.

The effect of alkaline conditions (pH 10.5 for 30-60 min at 23°C) on the extraction of protein from mechanically deboned poultry residues (MDPR) was examined with respect to the general bacterial flora, coliforms and salmonellae. Standard plate counts decreased from 1.5 × 103 CFU/g in the MDPR to 2.0 × 102 CFU/g in the freshly extracted protein curd; coliform counts decreased from 4.9 × 101 MPN/g to 0. Coliforms survived only when the MDPR was mishandled for 5 h at 23°C before alkaline extraction whereas salmonellae appeared to be eliminated entirely, irrespective of preincubation abuse of the MDPR or introduction of increased levels of Salmonella infantis . Spoilage of the protein curds occurred in 14 days at 3°C but there was no increase in coliform numbers. Reappearance of salmonellae following storage was seen only in the protein extracted from MDPR inoculated with S. infantis . The destruction of salmonellae by pH 10 was confirmed in a tryptic soy broth model system, but only under ambient temperature exposure; neither growth nor destruction occurred at 3 or 10°C. It was concluded that alkaline extraction of protein from MDPR using the suggested operating conditions does not exaggerate any public health hazard involving salmonellae.

Growth and inhibition of Salmonella infantis , Enterobacter aerogenes and Escherichia coli in fermenting soybeans during tempeh production were studied in presence and absence of Lactobacillus plantarum . In fermenting unacidified soybeans S. infantis grew by 7 log units in 40 h. E. coli and E. aerogenes grew by 6 and 7 log units respectively. A similar pattern of growth of the three test organisms in fermenting acidified beans was also noted. Further inoculation of unacidified cooked beans with L. plantarum at a level of 106/g resulted in a complete inhibition of the test organisms in the product. On acidified cooked beans a lower level of L. plantarum inoculum (102/g) was enough to show a complete inhibitory effect. The lowering of the pH in fermenting beans by L. plantarum might have played a role in the destruction of the test organisms.

Synopsis The effects of nitrovin and tetracycline on the elimination and persistence of Salmonella infantis in the intestine of broiler chicks were studied. Experiments were also carried out regarding the influence of these drugs on certain bacteria which tend to prevent the establishment of S. infantis in the intestines of chickens. It was shown that chicks artificially infected with S. infantis and fed for 5 weeks with 20 ppm nitrovin in the food had a lower incidence of salmonellae than those similarly infected and fed with 100 ppm tetracycline or without any drugs in the food. Ten ppm nitrovin in the food of artificially infected chicks did not prevent pre‐treatment with a culture of intestinal bacteria from having an inhibiting effect on the colonisation of the caeca with S. infantis. The salmonella inhibiting effect of pre‐treatment of infected chicks with intestinal bacteria was not destroyed when the bacteria were cultured in vitro in the presence of 10 ppm nitrovin, but it was destroyed by both 1...

The attachment of bacteria to chicken and beef meat with and without fascia was studied. It was found that bacteria attach readily to the meat surfaces. The kinetics of attachment depend on the bacterial strain, as well as on the meat surface. Of the bacteria tested, Pseudomonas EBT/2/143 attached most readily to all meat surfaces examined. Chicken breast with fascia was the best surface for attachment. A study was also made of the effects of storage on the multiplication of the attached bacteria and the feasibility of removing them. A high level of Salmonella infantis was found in comparison to the other bacteria after 24 h of storage at 20°C. More investigations are needed to find out whether other serotypes of salmonellae will multiply to similar levels on these surfaces. After micro-colonies began to form, the newly generated bacteria were easy to remove. The hygienic consequence of this phenomenon is discussed.

Es wird eine Epidemie mit Salmonella infantis beschrieben, die aus einer geburtshilflichen Abteilung hervorging. Der Ausgangspunkt der Infektion konnte nicht geklart werden. Insgesamt wurden 28 Sauglinge (zur Halfte Neugeborene) wegen Enteritis oder positiver Stuhlbefunde in die Kinderklinik aufgenommen. Siebenmal war der Verlauf schwer, siebenmal mittelschwer, 12mal leicht. Ein Kind starb an der Erkrankung in Komplikation mit einem schweren Pylorospasmus. Nach klinischer Heilung hielt die Bakterienausscheidung bei 8 Kindern langer als 3 Monate, bei 1 Kind 16 Monate an.

Frozen meat by-products, liver, and fish used as components in the diets of mink and a dry cereal-type feedstuff were examined for their microbiological condition initially and after 12 and 24 hr of storage at 30 C. The dry product was moistened before incubation. Initially, frozen meat by-products and frozen liver had a similar microbiological profile. Both contained an average per gram of approximately 5.5 million total bacteria, 175 thousand enterococci, 10 to 30 thousand coliforms, and 400 yeasts and molds. Salmonellae and coagulase-positive staphylococci were recovered from 40% of the samples of both products. Salmonellae associated with these products included: Salmonella saint paul, Salmonella typhimurium, Salmonella infantis, Salmonella derby and Salmonella anatum. The frozen fish product contained, on the average, less than 10% of the number of microorganisms found in the other two products and test samples were free from coagulase-positive staphylococci. Salmonellae found in this product included: S. saint paul, S. derby, and S. infantis. Examination of the dried cereal-type mink feed revealed low numbers of microorganisms and an absence of salmonellae and coagulase-positive staphylococci. Incubation of all feedstuffs tested was accompanied by rapid growth of bacteria during the first 12 hr period and continued but slower growth during the second 12 hr period. Multiplication of yeasts and molds was minimal in the frozen feeds but was rapid in the moistened cereal product during the second 12 hr period of incubation. Coagulase-positive staphylococci grew well in the frozen feeds but multiplication of suspected salmonellae was minimal in these products.

Raw wild rice was tested for its microbiological condition and was found to contain, per gram, up to 21 × 108 total aerobic count, 63 × 106 coliforms, 98 × 107 psychrotrophs, 16 × 106 streptococci, 26 × 104 yeasts, and 83 × 105 molds. Although the product was free of coagulase-positive staphylococci, Salmonella infantis and Escherichia coli were found in some samples. Rice was parched at 51.7 C (125 F) for 8 hr, 65.6 C (150 F) for 180 min, 79,4 C (175 F) for 180 min, and 121.1 C (250 F) for 105 min. Parching reduced the number of viable organisms and greatest changes appeared when the higher temperatures were used. Unhulled rice parched at 79.4 C contained, per gram, 40 × 106 total aerobic count, 33 × 103 psychrotrophs, 46 × 102 coliforms, 100 × 103 streptococci, Samples of wild rice obtained from local supermarkets contained, per gram, up to 106 total aerobic count and 104 coliforms. Other types of microorganisms for which tests were made, could not be recovered from most samples.

Edwards , P. R. (Communicable Disease Center, U.S. Public Health Service, Atlanta, Ga.), A. C. McWhorter, and G. W. Douglas . A culture of Salmonella infantis of complex antigenic constitution. J. Bacteriol. 84: 95–98. 1962—An antigenically complex Salmonella serotype ( 6,7:z 49 , r:z 49 , 1,5 ), in which the antigen z 49 is a major component of both phases, is described. Through loss variation, this form gives rise to cultures identical with S. infantis ( 6,7:r:1,5 ). Attention is drawn to the similarity of its behavior to that of S. montgomery and S. salinatis , and the possible origin of such complex forms is discussed briefly. The organism is not assigned a name, but is considered simply as a complex form of S. infantis .

From each of three slaughterhouses, 50 samples of broiler neck skin were taken at slaughter line. A farm, from which the largest number of positive samples originated, was identified. In slaughterhouse 2, Salmonella was determined in 17 samples of which 11 samples originated from the same farm. At the beginning of broiler breeding, Salmonella presence wasn‘t detected. However, after the second week Salmonella was found. All positive samples were identified as Salmonella Infantis . Comparing genetic similarity with the same strain originating from infected humans showed that ≥ 92% of mutual genetics similarity was confirmed.

A total of 223 retail samples consisting of chicken pieces (81), Kebab and Kufta (36), Ground meat (33), Beefburger (29), Steak beef (25) and liver (19) were analyzed and revealed the presence of Salmonella sp. 16·14% of the samples. Of the nine different serotypes isolated, Salmonella infantis was predominant.

A sequence-specific endonuclease was isolated from a strain of Salmonella infantis. Its recognition sequence proved to be identical to that of restriction endonuclease · AvaII (an endonuclease from the blue-green alga Anabaena variabilis), G↓G(AT)CC.

Twelve compounds were evaluated as salmonella antagonists in commercial meat and bone meal. The test organism was a nalidixic acid-resistant strain of Salmonella infantis. Adequate moisture to support salmonella growth was assured by the addition of 40% water to each 50 g test sample. Compounds were tested at levels permitted for food additives except formalin which has not been approved. Salmonella counts were determined every few days by spread plates and the pH was recorded from the initial 1:10 dilution. Although the salmonella population initially declined in the presence of several additives, none of the compounds were effective in preventing salmonella multiplication in the MBM except formalin at levels greater than .1%.

A large S. infantis infection epidemic in broiler chickens was studied during a period of one year. The outbreak affected three broiler producing companies in Finland. The infection spread to breeding farms according to available data during the summer of 1975. The epidemic still prevailed at the end of the studies on the farms of certain companies. The origin of the infection and the means of its spreading could not be ascertained. Some epidemiological evidence suggesting that a hatchery might have spread the infection was found. Contaminated feed may also have been involved, although the findings do not support feed as the principal vehicle in the epidemic. A complex pattern of transmission is most probable. A microbiological preventive method based on the feeding of a culture of intestinal flora of adult chickens to newly hatched broiler chickens was used on many farms in the study. The feeding of the culture lowered the proportion of infected flocks on the farms and significantly lowered the number of infected birds in those flocks, where the prevention was not complete. kw|Keywords|k]Salmonella infantis; k]infection; k]epidemic; k]broiler chicken

A bacteriophage typing system is described for Salmonella infantis. Nine phages were selected, of which three were isolated from sewage and six from human feces. All except 7 of the 546 strains collected between 1974 and 1978 could be classified into 23 different phage types. The five most common phage types comprised 26, 13, 9, 9, and 9% of all strains, respectively. Strains from humans, animals, food, and water isolated during nine episodes, or from given patients at different intervals of time, belonged to the same phage type.

An outbreak ofSalmonella infantisgastroenteritis in a Minnesota hospital, in 1962, involved 17 inpatients and six hospital personnel. Epidemiological studies indicated the source of infection to be scrambled eggs contaminated after preparation by a food-service worker recently recovered from gastroenteritis. Direct person-to-person spread of salmonellosis was indicated by findingSal infantisin five hospital personnel in whom gastroenteritis developed subsequent to close contact with either the presumed index subject or infected patients. Although in vitro antibiotic studies showed the organism sensitive to tetracylcine and chloramphenicol, treatment had no apparent effect on the clinical course or on duration ofSal infantisrecovery from the patients' stools.

POULTRY are a considerable reservoir of salmonellae and a common source of infection in human Salmonella epidemics1. In 1971 a severe outbreak of Salmonella infantis infection occurred among Finnish broiler flocks, and 277 human cases2 were diagnosed as caused by the same serotype. The broiler industry suffered serious losses through confiscation of broiler meat and elimination of infected birds.

Background and Objectives: Multidrug resistant Salmonella strains have been observed around the world in recent years. Many mechanisms contribute to the spread of antimicrobial resistance genes. This study aimed at determining the distribution and transmission of class 1, 2 and 3 integrons among MDR Salmonella isolates collected from a selection of chicken broilers in the north of Iran. Materials and Methods: PCR assays were used to detect genes for tetracyclines (tetA, tetB and tetG), chloramphenicol (cat1 and floR), and streptomycin (strA). Also, the presence of class 1, 2 and 3 integrons in all MDR isolates was evaluated using specific primers for the integrase genes of integrons intI1, intI2 and intI3. Results: Class 1, 2 and 3 integrons were present in 36%, 42% and 4% of the MDR isolates, respectively. Out of the tetracyclines resistant isolates, 47 (100%) and 5 (10.6%) carried tetA, tetB genes, respectively, while no isolate was positive for the tetG gene. All 36 chloramphenicol- resistant strains carried floR and cat1 genes. Nine (18%) Salmonella Infantis isolates harbored the strA gene, conferring resistance to sterptomycin. Conclusion: This study found a high frequency of antimicrobial resistance genes among Salmonella isolates; therefore, management strategies are needed to prevent food-borne diseases caused by MDR Salmonella from food supplies.

Fil: Merino, Luis Antonio. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Fil: Ronconi, María Cristina. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Fil: Navia, Margarita M. Hospital Clínic. Instituto de Infecciones e Inmunología; España. Fil: Ruiz, Joaquim. Hospital Clínic. Instituto de Infecciones e Inmunología; España. Fil: Sierra, Josep M. Hospital Clínic. Instituto de Infecciones e Inmunología; España. Fil: Cech, Norma B. Hospital “4 de Junio”; Argentina. Fil: Lodeiro, Norma S. Hospital “4 de Junio”; Argentina. Fil: Vila, Jordi. Hospital Clínic. Instituto de Infecciones e Inmunología; España. Salmonella Infantis has been the second most common serovar in Argentina in the last two years, being isolated mostly from paediatric hospitalised patients. In order to determine the clonal relationship among Salmonella Infantis strains, we examined 15 isolates from paediatric patient faeces in Argentina (12 geographically related and 3 geographically non-related) by using antimicrobial susceptibility, plasmid profiling, repetitive extragenic palindromic (REP) PCR, enterobacterial repetitive intergenic consensus (ERIC) PCR, and low-frequency restriction analysis of chromosomal DNA by pulsed field gel electrophoresis (PFGE). Four Spanish strains were included as controls of clonal diversity in molecular techniques. Antibiotype and plasmid profile was not useful as epidemiological tools. PFGE and REP-PCR were able to discriminate between Argentinean and Spanish isolates of Salmonella Infantis allowing to detect genetically related strains in three different cities. This finding indicates that a possible spread of a clone of this serovar in the North-eastern Region of Argentina has taken place in 1998. Salmonella Infantis ha sido el segundo serovar más común en la Argentina en los últimos dos años, siendo aislada principalmente, a partir de pacientes pediátricos hospitalizados. La relación clonal entre 15 aislamientos de Salmonella Infantis obtenidos de heces de pacientes pediátricos en Argentina se estudió mediante la susceptibilidad antimicrobiana, el perfil plasmídico, amplificación por reacción en cadena de la polimerasa (PCR) de las secuencias repetitivas REP y ERIC, y electroforesis de ADN total en campo pulsátil (PFGE). Cuatro cepas españolas fueron incluidas como control de diversidad clonal. El antibiotipo y el perfil plasmídico no fueron herramientas útiles en la tipificación. PFGE y REP-PCR fueron capaces de discriminar entre las cepas argentinas y españolas de Salmonella Infantis, permitiendo detectar cepas genéticamente relacionadas en tres ciudades diferentes. Este hallazgo indica que una posible diseminación clonal de este serovar ha tenido lugar en la región nordeste de Argentina en 1998.

Salmonella Infantis is considered in recent years an emerging Salmonella serovar, as it has been associated with several outbreaks and multidrug resistance phenotypes. Phages appear as a possible alternative strategy to control Salmonella Infantis (SI). The aims of this work were to characterize two phages of the Felixounavirus genus, isolated using the same strain of SI, and to expose them to interact in challenge assays to identify genetic and phenotypic changes generated from these interactions. These two phages have a shared nucleotide identity of 97% and are differentiated by their host range: one phage has a wide host range (lysing 14 serovars), and the other has a narrow host range (lysing 6 serovars). During the 12 h challenge we compared: (1) optical density of SI, (2) proportion of SI survivors from phage-infected cultures, and (3) phage titer. Isolates obtained through the assays were evaluated by efficiency of plating (EOP) and by host-range characterization. Genomic modifications were characterized by evaluation of single nucleotide polymorphisms (SNPs). The optical density (600 nm) of phage-infected SI decreased, as compared to the uninfected control, by an average of 0.7 for SI infected with the wide-host-range (WHR) phage and by 0.3 for SI infected with the narrow-host-range (NHR) phage. WHR phage reached higher phage titer (7 × 1011 PFU/mL), and a lower proportion of SI survivor was obtained[AS1] [DR2] from the challenge assay. In SI that interacted with phages, we identified SNPs in two genes (rfaK and rfaB), which are both involved in lipopolysaccharide (LPS) polymerization. Therefore, mutations that could impact potential phage receptors on the host surface were selected by lytic phage exposure. This work demonstrates that the interaction of Salmonella phages (WHR and NHR) with SI for 12 h in vitro leads to emergence of new phenotypic and genotypic traits in both phage and host. This information is crucial for the rational design of phage-based control strategies. [AS1]Please confirm that your original meaning is retained [DR2]Authors: Yes, it's correct, Data_Supplementary Materials_viruses-516726

Salmonella Infantis is considered in recent years an emerging Salmonella serovar, as it has been associated with several outbreaks and multidrug resistance phenotypes. Phages appear as a possible alternative strategy to control Salmonella Infantis (SI). The aims of this work were to characterize two phages of the Felixounavirus genus, isolated using the same strain of SI, and to expose them to interact in challenge assays to identify genetic and phenotypic changes generated from these interactions. These two phages have a shared nucleotide identity of 97% and are differentiated by their host range: one phage has a wide host range (lysing 14 serovars), and the other has a narrow host range (lysing 6 serovars). During the 12 h challenge we compared: (1) optical density of SI, (2) proportion of SI survivors from phage-infected cultures, and (3) phage titer. Isolates obtained through the assays were evaluated by efficiency of plating (EOP) and by host-range characterization. Genomic modifications were characterized by evaluation of single nucleotide polymorphisms (SNPs). The optical density (600 nm) of phage-infected SI decreased, as compared to the uninfected control, by an average of 0.7 for SI infected with the wide-host-range (WHR) phage and by 0.3 for SI infected with the narrow-host-range (NHR) phage. WHR phage reached higher phage titer (7 × 1011 PFU/mL), and a lower proportion of SI survivor was obtained[AS1][DR2] from the challenge assay. In SI that interacted with phages, we identified SNPs in two genes (rfaK and rfaB), which are both involved in lipopolysaccharide (LPS) polymerization. Therefore, mutations that could impact potential phage receptors on the host surface were selected by lytic phage exposure. This work demonstrates that the interaction of Salmonella phages (WHR and NHR) with SI for 12 h in vitro leads to emergence of new phenotypic and genotypic traits in both phage and host. This information is crucial for the rational design of phage-based control strategies. [AS1]Please confirm that your original meaning is retained [DR2]Authors: Yes, it's correct

Ten isolates of Salmonella infantis (serologically typed) were found in litter and runoff collected from two experimental feedlots near the Kansas State University campus. Pathogenic implications are discussed relative to recreation water sites. Agricultural runoff maybe a source of viable salmonellae.

WHEREAS abortion in cattle associated with Brucella or Vibrio infection is very common, it can, in some rare cases, also be caused by Salmonella species. The Salmonella strain most frequently held responsible for bovine abortion is Salmonella dublin; this strain has already been found in the Belgian Congo in a bovine fœtus. Salmonella infantis, a world-wide Salmonella type, which has already been isolated from man and several animal species, has not yet been recorded, so far as we can ascertain, as causing bovine abortion.

SUMMARY A native intestinal microflora of chickens which is protective against salmonella readily transferred to penmates and apparently to birds in adjacent pens. The microflora not only minimized infection resulting from exposure following colonization of the gut with microflora, but significantly abbreviated the period of infection when introduced after a salmonella infection was established in chicks. A microflora with undiminished protective activity, sensitive to only a few commonly used antibacterials, was established in a SPF-Cofal/Marek-negative population. Intestinal microflora from mourning doves was at least partially effective in protecting chicks against a naladixic-acid-resistant strain of Salmonella infantis. In limited tests with 2 of 3 sources of protective microflora, the growth rate of chicks in the absence of salmonellae was significantly improved. A hypothesis involving specificity of attachment between the glycocalyces of the protective microflora and of the intestinal mucosa is offered as the likely mechanism of protection.

Competitive exclusion of salmonella by native gut microflora was studied in 24 groups of 100 chickens each started in thoroughly cleaned and sanitized isolation facilities. During 53-day test periods, infection by both Salmonella infantis and S. typhimurium was greatly restricted in groups previously treated with native microflora compared with control groups. Feed and water starvation for 48 hours starting at either 23 or 51 days did not affect the incidence of infection in protected groups. The protective flora spread readily to adjacent untreated groups; infected groups given the protective flora at 11 days exhibited a more rapid elimination of infection than untreated control groups.

SUMMARY Preliminary studies with Salmonella infantis and S. typhimurium showed that those salmonellae do not persist as long in built-up poultry litter as in fresh litter. The shed rate of birds on built-up litter suggests an inhibitory effect for salmonellae in the litter. This effect may reduce salmonellae in either the litter or the intestinal tract. Cycling of salmonellae between litter and the intestinal tract appears of significance in maintaining intestinal infection. This cycling is more evident in unchanged new litter than in built-up litter or in fresh litter changed periodically. Fresh litter replaced periodically did not appear to differ from built-up litter in infection rate. Contamination levels of the two litters were similar.