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PubMed2005

Outer membrane protein of salmonella is the major antigenic target in patients with salmonella induced reactive arthritis.

OBJECTIVE: We previously reported that Salmonella typhimurium was the triggering agent in one-third of our patients with sporadic enteric reactive arthritis (ReA) and undifferentiated spondyloarthropathy (uSpA). The antigens recognized by the synovial T cells in Salmonella induced ReA are not known. We investigated the immunodominant antigens in Salmonella ReA. METHODS: Synovial fluid mononuclear cells (SFMC) from 53 patients with ReA/uSpA were cultured with crude lysate of S. typhimurium. In 20 patients, the triggering agent was found to be Salmonella (stimulation index, SI, > 2.5). For cell fractionation of S. typhimurium, the sonicated crude lysate was separated by ultracentrifugation into a cytoplasmic supernatant (CYT) and membrane pellet (OMP). The CYT was further separated on SDS-PAGE and blotted onto nitrocellulose membrane for proliferation assays. SFMC from 20 patients with Salmonella ReA/uSpA were stimulated with OMP, CYT, and cytosolic fractions of S. typhimurium, and proliferation was measured by thymidine incorporation. Quantitation of antigen-specific cells in SF was by intracellular interferon-g staining in 7 patients and paired peripheral blood (PB) in 5 patients after stimulation with crude Salmonella lysate, CYT, and OMP. RESULTS: Out of 20 patients with Salmonella ReA/uSpA, the SFMC showed a significant proliferation to OMP in 19 patients and CYT in 17 patients. The median SI of OMP (8.2, range 2.8-52.5) was significantly higher (p < 0.0005) than for the CYT (4.9, 2.7-18.8). Fifty percent of the patients showed proliferative response to cytosolic fractions of < 60 kDa. The mean antigen-specific T cell frequency was also higher with OMP (0.68% +/- 0.59%) than CYT (0.53% +/- 0.62%) but this was not statistically significant. Compared to PB, the OMP-specific cells were 7.5 times more numerous in the SF (p < 0.05). CONCLUSION: The cellular immune response in Salmonella ReA/uSpA is directed predominantly against the OMP and low molecular weight proteins in the cytosolic fraction.

Adolescent↗
PubMedDate not supplied

[Sanitation of biowaste compost by using Salmonella enteritidis as a pathogen indicator and survival of Salmonella in seepage water].

The following investigations show the frequency of the occurrence of Salmonella in biowastes. Salmonellae, belonging to the serotypes Salmonella enteritidis, infantis and agona were detected in 50% of the investigated biowaste samples. In order to control the reliability of compositing techniques on eliminating pathogens, Salmonella enteritidis was used as a pathogen indicator, which was brought into a container composting process and investigated on it's decline. Although the input indicator bacteria were eliminated in every case latest until the end of container composting, Salmonella was detected in 36% of the investigated fresh compost samples. Every time when Salmonella was detected in input material, the same serotypes were to be found in seepage water and survived there until the end of intensive rot. In laboratory experiments the maximum survival time of Salmonella enteritidis in seepage water at +5 degrees C was 42 days. Seepage water was found out to be a reservoir for survival of Salmonellae and has to be considered as a permanent source of contamination. In the question of the disposal of seepage water there are disagreements between the instructions of TA Siedlungsabfall and TA Luft.

Animal Husbandry↗
PubMed2000

Survival and filamentation of Salmonella enterica serovar enteritidis PT4 and Salmonella enterica serovar typhimurium DT104 at low water activity.

In this study we investigated the long-term survival of and morphological changes in Salmonella strains at low water activity (a(w)). Salmonella enterica serovar Enteritidis PT4 and Salmonella enterica serovar Typhimurium DT104 survived at low a(w) for long periods, but minimum humectant concentrations of 8% NaCl (a(w), 0. 95), 96% sucrose (a(w), 0.94), and 32% glycerol (a(w), 0.92) were bactericidal under most conditions. Salmonella rpoS mutants were usually more sensitive to bactericidal levels of NaCl, sucrose, and glycerol. At a lethal a(w), incubation at 37 degrees C resulted in more rapid loss of viability than incubation at 21 degrees C. At a(w) values of 0.93 to 0.98, strains of S. enterica serovar Enteritidis and S. enterica serovar Typhimurium formed filaments, some of which were at least 200 microm long. Filamentation was independent of rpoS expression. When the preparations were returned to high-a(w) conditions, the filaments formed septa, and division was complete within approximately 2 to 3 h. The variable survival of Salmonella strains at low a(w) highlights the importance of strain choice when researchers produce modelling data to simulate worst-case scenarios or conduct risk assessments based on laboratory data. The continued increase in Salmonella biomass at low a(w) (without a concomitant increase in microbial count) would not have been detected by traditional microbiological enumeration tests if the tests had been performed immediately after low-a(w) storage. If Salmonella strains form filaments in food products that have low a(w) values (0.92 to 0.98), there are significant implications for public health and for designing methods for microbiological monitoring.

Animals↗
PubMedDate not supplied

Efficacy of two avian Salmonella-immune lymphokines against liver invasion in chickens by Salmonella serovars with different O-group antigens.

Newly hatched chicks are susceptible to organ invasion by various serovars of Salmonella. We have previously shown that intraperitoneal administration of Salmonella enteritidis-immune lymphokine (SEILK) increased resistance to organ invasion by S. enteritidis (SE) in day-of-hatch chicks. In the present study, we determined that Salmonella-immune lymphokines can provide protection against organ invasion by serovars that are unrelated to the original serovar used as an immunogen. Immune lymphokines were produced from the splenic T cells of mature hens immunized with either viable SE or Salmonella anatum (SA). Day-of-hatch chicks were treated with either SA-immune lymphokine (SAILK) or SEILK and challenged per os with either Salmonella typhimurium (ST) or SE 1 hr later. Liver samples were aseptically collected 20 hr later and were cultured to detect salmonella. We found that SAILK conferred resistance against invasion by either SE, a serogroup D organism, or ST, a serogroup B organism. Furthermore, SEILK reduced organ invasion by ST. These observations together reveal that the protection against organ invasion conferred by Salmonella-immune lymphokines is unrelated to the serovar-specific antigenic characteristics of the immunizing bacteria.

Animals↗
PubMed1999

Intracellular Salmonella typhimurium induce lysis of human polymorphonuclear leukocytes which is not associated with the Salmonella virulence plasmid.

The interaction between Salmonella typhimurium and human polymorphonuclear leukocytes (PMNs) was analyzed in vitro. Three S. typhimurium strains, the wild-type strain OU5043, its isogenic virulence plasmid-cured strain OU5048, and LT2, which represented the types that exhibited three mouse virulence levels, respectively, were used in this study. There was no correlation between the recovery of intracellular S. typhimurium from PMNs and the presence or absence of the virulence plasmid, or the strains' mouse virulence level. When the oxygen-dependent response of PMNs upon phagocytosis of S. typhimurium was examined by checking the intracellular reduction of nitroblue tetrazolium (NBT), the fraction of PMNs that reduced NBT on phagocytosis of the three strains was around 80%, whereas it was 58% with Escherichia coli, 95% with phorbol 12-myristate 13-acetate and 15% with a negative control. Thus there were no significant differences among the three Salmonella strains in terms of their ability to induce the oxidative response in PMNs. Microscopic analysis of Salmonella-infected PMNs indicated that the intracellular Salmonella induced lysis of PMNs. Both OU5043 and OU5048 exhibited a significant intracellular cytotoxic effect on PMNs after 24 hr of infection and this effect was not associated with the presence or absence of the virulence plasmid. On the other hand, lysis of PMNs was related to the intracellular survival of Salmnonella, as ofloxacin, an antibiotic, appeared to be able to protect human PMNs from Salmonella-induced cytotoxicity when this agent was added into the medium to inactivate the intracellular organism. The ability to induce lysis of PMNs by either wild-type or plasmid-cured strains of S. typhimurium may play a crucial role in the pathogenesis of non-typhoid Salmonella. The contribution of pSTV to human salmonellosis is likely to be limited. Furthermore, early institution of antibiotics with a high intracellular activity against Salmonella, such as fluoroquinolones, may be useful to prevent the dissemination of Salmonella infection.

Adult↗
PubMed1979

Diagnosis of Salmonella bacteria: antibodies against synthetic Salmonella O-antigen 8 for immunofluorescence and co-agglutination using sensitized protein A-containing staphylococci.

An antiserum against the synthetic disaccharide abequose 1 leads to 3 alpha rhamnose (AR), representative of Salmonella O-antigen 8, coupled to bovine serum albumin (BSA) was used for diagnosis of Salmonella bacteria by indirect immunofluorescence (IFL) and by co-agglutination (COA) using sensitized protein A-containing staphylococci. Among the 1150 enteric bacteria tested in IFL, the antiserum correctly identified all 99 Salmonella serogroup C2 and C3 bacteria with O-antigen 8. No fluorescence was seen with 484 Salmonella bacteria belonging to other serogroups or 567 non-Salmonella enteric bacteria. The anti-AR-BSA serum was favourable as compared to a conventional Salmonella factor O8 serum as regards both titre and specificity. In the COA test, all 22 Salmonella serogroup C2 and C3 strains agglutinated strongly and within seconds, whereas no agglutination could be seen when 93 Salmonella bacteria representing other serogroups were tested.

Agglutination Tests↗
PubMed2004

Salmonella enterica serovar Typhimurium infection induces cyclooxygenase 2 expression in macrophages: involvement of Salmonella pathogenicity island 2.

Salmonella pathogenicity island 2 (SPI-2) is required for intramacrophage survival and systemic infection in mice. We have recently reported that Salmonella enterica causes activation of the protein kinase A (PKA) signaling pathway in a manner dependent on SPI-2, resulting in the upregulation of interleukin-10 expression in macrophages (K. Uchiya et al., Infect. Immun. 72:1964-1973, 2004). We show in the present study the involvement of SPI-2 in a signal transduction pathway that induces the expression of cyclooxygenase 2 (COX-2), an inducible enzyme involved in the synthesis of prostanoids. High levels of prostaglandin E(2) (PGE(2)) and prostacyclin (PGI(2)), which are known to activate the PKA signaling pathway via their receptors, were induced in J774 macrophages infected with wild-type Salmonella compared to a strain carrying a mutation in the spiC gene, located within SPI-2. The increased production of both prostanoids was dependent on COX-2. COX-2 expression was dose dependently blocked by treatment with a specific inhibitor of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway, and the phosphorylation level of ERK1/2 was higher in macrophages infected with wild-type Salmonella compared to the spiC mutant. Taken together, these results indicate that Salmonella causes an SPI-2-dependent ERK1/2 activation that leads to increased COX-2 expression, resulting in the upregulation of PGE(2) and PGI(2) production in macrophages. A COX-2 inhibitor inhibited not only Salmonella-induced activation of the PKA signaling pathway but also growth of wild-type Salmonella within macrophages, suggesting that Salmonella utilizes the COX-2 pathway to survive within macrophages and that the mechanism involves activation of the PKA signaling pathway.

Animals↗
PubMed2005

Prevalence and antimicrobial resistance of Salmonella enteritidis and other salmonellas in the eggs and egg-storing trays from retail markets of Coimbatore, South India.

A study was conducted to determine the incidence of Salmonella enterica serovar Enteritidis and other Salmonella serovars on eggshell, egg contents and on egg-storing trays. A total of 492 eggs and 82 egg-storing trays were examined over a period of 1 year from different retail outlets of a residential area of Coimbatore city, South India. Salmonella contamination was recorded in 38 of 492 (7.7%) eggs out of which 29 was in eggshell (5.9%) and 9 in egg contents (1.8%). Around 7.5% of the egg-storing trays were also found to be contaminated with Salmonella. Serotyping of the Salmonella strains showed that 89.7% of the strains from eggshell, 100% of the strains from egg contents and 71.4% of the strains from egg-storing trays were Salmonella Enteritidis. Other serovarvars encountered were S. Cerro, S. Molade and S. Mbandaka from eggshell and S. Cerro from egg-storing trays. Seasonal variations in the prevalence pattern were identified with, a higher prevalence during monsoon months followed by post-monsoon and premonsoon. Further examination of the Salmonella strains was carried out by testing their antimicrobial sensitivity against 10 commonly used antimicrobials. Results revealed high prevalence of multiple antimicrobial resistance among these strains suggesting possible prior selection by use of antimicrobials in egg production.

Animals↗
PubMed2002

Herd prevalence of Salmonella spp. in Danish pig herds after implementation of the Danish Salmonella Control Program with reference to a pre-implementation study.

The problems addressed are: (1) comparison of prevalences of Salmonella spp. in different herd types in the Danish pig population after implementation of the Danish Salmonella Control Program (DSCP), and (2) to make a reference to a study from 1993/1994 (pre-implementation) with a discussion of possible biases when diagnostic methods differ slightly. The objectives were to present the prevalences of Salmonella spp., Salmonella Typhimurium, and multiresistant S. Typhimurium DT104 in Danish pig herds in 1998. Further, to discuss how herd prevalences may be compared to a previous study.A bacteriological study in 1998 comprised: (a) a random sample of slaughter pig producing herds (N=1962); (b) a random sample of farrow-to-grower (sow) herds (N=305); and (c) all breeding and multiplying (genetic) herds (N=366). A previous bacteriological study on Salmonella presence in 1993/1994 served as a model for the present study. The results of the study were that multiresistant S. Typhimurium DT104 was detected in one herd producing slaughter pigs. The herd apparent prevalences (HAPs) of Salmonella spp. were 11.7, 16.7 and 11.4% in genetic, sow, and slaughter pig herds, respectively. The conclusion of the study was that prevalence of multiresistant S. Typhimurium DT104 was low in the examined slaughter pig herds. The herd true prevalence (HTP) of Salmonella spp. in pigs had declined from before the start of the DSCP in 1993/1994 to 4 years later (1998).

Animals↗
PubMed2001

Emergence of multidrug-resistant Salmonella Gloucester and Salmonella typhimurium in Bangladesh.

Infections due to non-typhoid Salmonella, resistant to antibiotics, have recently emerged as an important health problem worldwide. Antibiotic resistance was studied by the disc-diffusion method among 3,876 (2.78%) non-typhoid Salmonella isolates cultured from 139,279 faecal samples in a diarrhoea treatment centre in Dhaka, Bangladesh, during 1989-1996. Of 499 salmonellae isolated in 1989, serogroup C (1.12%) was the most common, followed by Salmonella Typhi (0.72%) and serogroup B (0.71%). Isolation rate of serogroup B increased significantly to 2.18% (p < 0.01) in 1992 compared to 0.56% in 1991, 2.86% in 1995, and 2.48% in 1996. Serotyping of 194 serogroup B isolates revealed Salmonella Typhimurium (52%) and Salmonella Gloucester (45%) as predominant serotypes. Resistance to ampicillin (A), chloramphenicol (C), and trimethoprim-sulphamethoxazole (Sxt) (R type-ACSxt) increased to 89-100% during 1992-1996 from 20-28% during 1989-1991 (p < 0.01) among S. Typhimurium and S. Gloucester isolates. In 1993, 8-10% of the strains of both the serotypes, resistant to ampicillin, chloramphenicol, and trimethoprim-sulphamethoxazole, acquired resistance to ceftriaxone (Cr) (R type-ACSxtCr), which increased to 85-92% in 1996 (p < 0.01). All were susceptible to ciprofloxacin. A 157-kb conjugative plasmid transferred R type-ACSxt from both the serotypes to Escherichia coli K-12. The findings of the study suggest the emergence of multidrug-resistant S. Gloucester and S. Typhimurium for the first time as a significant health problem in Bangladesh, and surveillance is essential to monitor the resistant non-typhoid Salmonella and identify its sources and modes of transmission.

Anti-Bacterial Agents↗
PubMed2004

Haemolysins of Salmonella, their role in pathogenesis and subtyping of Salmonella serovars.

Haemolysin patterns of 175 strains of different Salmonella enterica subspecies enterica serovars isolated from different animal sources and places were determined using 11 different blood agar media made with either non-washed horse/sheep erythrocytes or with washed erythrocytes of cattle, sheep, horse, goat, rabbit, guinea pig, and human A, O and B blood groups. Study on 47 strains belonging to 10 serovars of Salmonella from buffalo meat (buffen), 42 strains of 11 serovars from goat meat (chevon): 16 strains of Salmonella enterica serovar Paratyphi B and 25 of S. enterica serovar Paratyphi B var Java from fish, meat, meat products and clinical cases; 45 isolates of S. Abortusequi from aborted mares (18), fetal contents (21), aborted donkey mares (2) and 4 reference strains, revealed that all host restricted Salmonella namely, S. enterica serovar Gallinarum, S. enterica serovar Anatum, S. enterica serovar Abortusequi and S. enterica serovar Paratyphi B could be divided into different haemolysin types based on their inability to produce haemolysis on one or more types of blood agar, while strains of all zoonotic Salmonella serovars induced haemolysis on all the 9 types of blood agar made of washed erythrocytes. None of 175 Salmonella could produce hemolytic colonies on blood agar made of non-washed horse/ sheep erythrocytes. Haemolysin type I (lysing all types of washed erythrocytes) was the commonest one among all serovars except S. Abortusequi, none of which lysed horse erythrocytes. Salmonella enterica serovar Abortusequi having hemolytic activity against sheep erythrocytes were more invasive but had lesser ability to survive in sheep mononuclear cells than non-hemolytic strains. Multiplicity of haemolysins appeared significant epidemiological tool.

Animals↗
PubMed1991

DNA sequence of a Salmonella-specific DNA fragment and the use of oligonucleotide probes for Salmonella detection.

Hybridization specificity of a 1.8-kb HindIII DNA fragment isolated from Salmonella typhimurium by a molecular cloning technique was confirmed by colony hybridization with 327 Salmonella isolates of various serotypes and 56 non-Salmonella isolates including Enterobacteriaceae closely related to Salmonella, such as Escherichia coli, Klebsiella, Citrobacter and Shigella. It was found that this 1.8-kb DNA fragment was highly specific for all the Salmonella isolates tested. The DNA sequence of this 1.8-kb fragment was then determined by the dideoxynucleotide chain termination method. According to this DNA sequence, six oligonucleotide fragments ranging from 17- to 26-mer were then chemically synthesized and tested for their hybridization specificities. Results show that three of the six oligonucleotide fragments are highly specific for all 327 Salmonella strains tested and can be used as probes for the specific detection of Salmonella in foods or other samples.

Base Sequence↗
PubMed1990

Dead salmonellae or their endotoxin accelerate the early course of a Salmonella infection in mice.

The course of a Salmonella infection following a low intravenous dose of virulent organisms was studied in mice. Simultaneous administration of 10(4) S. typhimurium C5 together with c. 10(8) dead salmonellae caused a marked acceleration of early net bacterial growth in the liver and spleen, leading to a rapidly overwhelming infection. Administration of similar numbers of either Staphylococcus albus or Bacillus cereus had no effect, whereas 20 micrograms of S. typhimurium Boivin-type lipopolysaccharide (B-LPS) produced an effect similar to dead organisms; 1 microgram B-LPS had a significant infection-accelerating effect. Both B-LPS and Westphal-type endotoxin (W-LPS) could enhance a salmonella infection in LPS-responsive C3H/HeMg mice, whereas only B-LPS was effective in LPS non-responder C3H/HeJ mice, implying that the infection-enhancing effect of a large bolus of dead organisms may be due in part to its LPS content. The results show that the course of a Salmonella infection following administration of large numbers of salmonellae in mice is different from that of Salmonella infections arising from small inocula. The relevance of these results to studies on the possible intracellular location of salmonellae in vivo is discussed.

Animals↗
PubMed2002

Estimating the prevalence of Salmonella spp. in swine herds--influence of sensitivity and specificity of Salmonella detection.

Information about the proportion of truly Salmonella-free herds is required for an evaluation of the epidemiological situation, the development of control strategies and their implementation. Findings regarding the presence of salmonellas in faeces and intestinal lymph nodes as well as the presence of Salmonella antibodies in meat juice from slaughtered pigs were obtained in the context of a study conducted by a number of institutes. These data were used for an analysis of the validity of data on the prevalence of infected animals within herds and on the prevalence of infected herds. The proportion of batches or herds with exclusively negative individual findings was found to depend not only on the true proportion of truly Salmonella-free animals within herds but quite essentially also on the distribution of the proportion of infected animals within herds, the sensitivity of the methods of examination and sample sizes. When taking into account the existing dependencies, it was found that among the swine, the real numbers of Salmonella carriers were much higher than shown by bacteriological and serological examination. Regarding salmonellosis in swine, also a number of contaminated herds must be expected which is far higher than that shown by the number of herds with positive findings in at least one animal. Even a low contamination of all or almost all herds would result in the numbers of 'negative' batches observed, i.e. batches with exclusively negative individual findings. A rating of the salmonella exposure of herds as high, low, or very low is possible and may, and should be, used for measures of consumer protection, irrespective of the proportion of truly Salmonella-free herds.

Animal Husbandry↗
PubMed2006

Immunization of sows in an integrated pig-breeding herd using a homologous inactivated Salmonella vaccine decreases the prevalence of Salmonella typhimurium infection in the offspring.

The efficacy of a homologous vaccination in preventing infection of suckling piglets with Salmonella (S.) Typhimurium was evaluated after an immunization of pregnant sows using an inactivated herd-specific S. Typhimurium vaccine. Twenty-five pregnant sows were vaccinated three times antepartum. The efficiency of this vaccine regime was assessed by comparison with a control group of 37 sows and their suckling piglets, which were daily treated with enrofloxacin from day 14 antepartum until the day of weaning. From the first day of life until day 142 post-partum, faecal samples of the piglets were collected and analysed for Salmonella shedding. In parallel, systemic antibody responses were monitored using a whole cell-based isotype-specific enzyme-linked immunosorbent assay (ELISA). The bacteriological investigation showed marked effects of vaccination. Salmonella Typhimurium could not be detected in any of the faecal samples of the piglets from the vaccinated sows. In contrast, the piglets of the group with long-time antibiotic treatment shed salmonellae rating to 47.4% of the animals. Furthermore, the offspring from vaccinated sows showed significantly decreased antibody activities of immunoglobulin (Ig)A and IgG. These bacteriological and serological results indicate a significantly lower Salmonella prevalence in piglets of the vaccinated group. As this study shows, the presented strategy of vaccination of pregnant sows with an inactivated Salmonella vaccine seems to be a suitable measure in decreasing Salmonella prevalence in offspring of infected sows.

Animals↗
PubMed1992

Evaluation of the Wellcolex Colour Salmonella Test for detection of Salmonella spp. in enrichment broths.

The Wellcolex Colour Salmonella Test was evaluated for detection of Salmonella spp. in enrichment broths of 1,010 stool samples. In 39 specimens, Salmonella spp. could be isolated from the selenite F broth (SF). Wellcolex agglutination indicative of the presence of Salmonella spp. was noted with the SF in 36 cases, 34 of which were in agreement with the subculture results. Therefore, relative to subculture, the sensitivity and specificity of the Wellcolex-selenite F procedure were 87 and 99%, respectively. Five false-negative results were noted. The gram-negative broth (GN) subculture revealed only 23 Salmonella spp. (59% sensitivity). The Wellcolex agglutination procedure applied to the GN indicated Salmonella spp. for 21 samples; its sensitivity was 70% and its specificity was 99% compared with GN subcultures. The Wellcolex agglutination procedure applied to the SF performed better than the agglutination of GN or direct plating procedures and detected 17 of the 39 Salmonella spp. at least 24 h earlier than did culture.

Bacteriological Techniques↗
PubMed1977

[The effectiveness of antibiotic treatment for Salmonella enteritis and Salmonella excretors].

The role of antibiotic treatment was evaluated in 190 hospitalized patients with Salmonella enteritis and 80 with asymptomatic Salmonella infection (without typhoid or paratyphoid). The results indicate that antibiotic treatment does not shorten the duration of excretion (compared with non-treated patients). Because of the danger of prolonged bacterial excretion under antibiotic treatment in complication-free Salmonella enteritis as well as the possible development of resistant Salmonella strains, antibiotic treatment of Salmonella infections (other than typhoid or paratyphoid) should be limited to systemic forms. Treatment of complication-free Salmonella enteritis and Salmonella excretors should be limited to intestine-cleansing measures.

Acute Disease↗
PubMed2003

Reevaluating fluoroquinolone breakpoints for Salmonella enterica serotype Typhi and for non-Typhi salmonellae.

Salmonella enterica infections cause considerable morbidity and mortality worldwide. Antimicrobial therapy may be life-saving for patients with extraintestinal infections with S. enterica serotype Typhi or non-Typhi salmonellae. Because antimicrobial resistance to several classes of traditional first-line drugs has emerged in the past several decades, the quinolone antimicrobial agents, particularly the fluoroquinolones, have become the drugs of choice. Recently, resistance to nalidixic acid has emerged among both Typhi and non-Typhi Salmonella serotypes. Such Salmonella isolates typically also have decreased susceptibility to fluoroquinolones, although minimum inhibitory concentrations of the fluoroquinolones usually are within the susceptible range of the interpretive criteria of the NCCLS. A growing body of clinical and microbiological evidence indicates that such nalidixic acid-resistant S. enterica infections also exhibit a decreased clinical response to fluoroquinolones. In this article, we recommend that laboratories test extraintestinal Salmonella isolates for nalidixic acid resistance, we recommend that short-course fluoroquinolone therapy be avoided for infection with nalidixic acid-resistant extraintestinal salmonellae, and we summarize existing data and data needs that would contribute to reevaluation of the current NCCLS fluoroquinolone breakpoints for salmonellae.

Anti-Infective Agents↗