Re-emergence of chloramphenicol-sensitive Salmonella typhi

Catalytic Syn-Selective Nitroaldol Approach to Amphenicol Antibiotics: Evolution of a Unified Asymmetric Synthesis of (-)-Chloramphenicol, (-)-Azidamphenicol, (+)-Thiamphenicol, and (+)-Florfenicol

A unified strategy for an efficient and high diastereo- and enantioselective synthesis of (-)-chloramphenicol, (-)-azidamphenicol, (+)-thiamphenicol, and (+)-florfenicol based on a key catalytic syn-selective Henry reaction is reported. The stereochemistry of the ligand-enabled copper(II)-catalyzed aryl aldehyde Henry reaction of nitroethanol was first explored to forge a challenging syn-2-amino-1,3-diol structure unit with vicinal stereocenters with excellent stereocontrol. Multistep continuous flow manipulations were carried out to achieve the efficient asymmetric synthesis of this family of amphenicol antibiotics.

Trends in Empirical Treatment of Hospitalized Children with Acute Gastroenteritis in Nigeria

BACKGROUND

Acute gastroenteritis is a common infectious disease with a high rate of morbidity and mortality in children below five years of age. Appropriate empirical treatment is therefore vital for reducing the incidence of the disease.

OBJECTIVE

This study aimed at determining the trends in the empirical treatment of hospitalized children with acute gastroenteritis.

METHODS

The study involved the data analysis of 88 medical folders of children who were diagnosed with gastroenteritis from January to February 2020 (a period of gastroenteritis yearly outbreak) in Mile 4 Hospital Abakaliki, Ebonyi State, Nigeria. Socio-demographic data and administered antibiotics data were collected.

RESULTS

Out of the 88 children, a total of 54 (61%) children were males, while 34 (39%) were females. The ages of the children ranged between 1-51 months, while the mean age was seen at 14 months. About 58 (66%) were diagnosed with acute gastroenteritis alone, with children aged 7-12 months recording higher numbers [25 (28%)]. Severe dehydration was seen as the most common morbidity of children with acute gastroenteritis. The guardians/parents of these children stayed at home for an average of 3 days (1-6 days) before visiting the hospital. The children were treated for an average of 5 days (2-9 days) in the hospital. The most singly used antibiotics was ciprofloxacin [31 (35%)] followed by a combination of ciprofloxacin and ceftriaxone [21 (24%)]. About 12 (14%) of the children were treated using a single dose of the antimalarial drug while 10 (11%) were treated in double combination therapy. The lowest duration in hospitalization (4 days) was seen in the use of a single dose regimen, while the highest hospitalization time (6 days) was seen in the use of a triple dose regimen.

CONCLUSION

The best empirical treatment of acute gastroenteritis may involve the use of ciprofloxacin alone and its combination with ceftriaxone. The severity of gastroenteritis may also be exacerbated with malaria.

Sensitivity Pattern Of Salmonella typhi And Paratyphi A Isolates To Chloramphenicol And Other Anti-Typhoid Drugs: An In Vitro Study

Purpose

To investigate the antimicrobial sensitivity pattern of commonly prescribed antimicrobials (chloramphenicol, cefixime, ofloxacin, azithromycin, and ceftriaxone) against Salmonella enterica isolates.

Methods

Blood culture positive isolates of S. typhi and S. paratyphi A (N = 251) received at Metropolis Healthcare Limited (Mumbai, India) from four zones of India (North, South, West, and East) between April and August 2018 were tested for antimicrobial susceptibility by E-test method. Based on the minimum inhibitory concentration (MIC), the organism was categorized as sensitive, intermediate, and resistant against the respective antibiotics as per Clinical and Laboratory Standards Institute criteria 2018.

Results

Out of 251 Salmonella isolates, 192 (76.5%) were S. typhi and 59 (23.5%) were S. paratyphi A. All 251 (100%) Salmonella isolates were sensitive to cefixime, ceftriaxone, and azithromycin; 237/251 (94.4%) isolates to chloramphenicol and only 9/251 (3.6%) isolates were sensitive to ofloxacin. Based on average MIC and MIC breakpoints, Salmonella isolates were found to be sensitive to chloramphenicol (MIC: 3.89±6.94 µg/mL), cefixime (MIC: 0.13±0.11 µg/mL), azithromycin (MIC: 3.32±2.19 µg/mL), and ceftriaxone (MIC: 0.11±0.18 µg/mL) and resistant to ofloxacin (MIC: 2.95±6.06 µg/mL). More than 20% of Salmonella isolates had MICs of chloramphenicol as 1.5 µg/mL (27.85% isolates) and 2 µg/mL (29.53% isolates).

Conclusion

Our study confirms the re‑emergence of susceptibility of Salmonella isolates to chloramphenicol. Further, the concern about fluoroquinolone-decreased susceptibility as indicated by the intermediate susceptibility or resistance was reiterated in this study. Though cefixime, azithromycin, and ceftriaxone showed susceptibility, the possibility of antibiotic resistance with the irrational use of these antibiotics cannot be deterred. This study thus emphasizes the need for continuous evaluation and judicious use of antimicrobials, considering the ever-changing landscape.

Comparison of phenotypic and WGS-derived antimicrobial resistance profiles of Salmonella enterica serovars Typhi and Paratyphi

Objectives

Surveillance of antimicrobial resistance (AMR) in Salmonella enterica serovars Typhi and Paratyphi is essential to provide an evidence base for empirical treatment protocols and to monitor emerging AMR. We sought to compare phenotypic and WGS-based genotypic methods for the detection of AMR in Salmonella Typhi and Salmonella Paratyphi.

Methods

WGS data from 603 isolates of Salmonella Typhi (n = 332) and Salmonella Paratyphi (n = 271) were mapped to genes or chromosomal mutations known to be associated with phenotypic AMR and compared with phenotypic susceptibility data interpreted using breakpoints recommended by EUCAST.

Results

There were two (0.03%) discordant interpretations out of a possible 6030 isolate/antimicrobial class combinations. MDR (resistant to three or more classes of antimicrobial) was detected in 83/332 (25.0%) Salmonella Typhi isolates, but was not detected in Salmonella Paratyphi. Thirty-six (10.8%) isolates of Salmonella Typhi were resistant to ciprofloxacin (MIC >0.5 mg/L), with 33 (9.9%) of 332 exhibiting mutations in gyrA and parC, and 244 (73.5%) isolates had reduced susceptibility to ciprofloxacin (MIC 0.06-0.25 mg/L). In comparison, 209/227 (92.1%) isolates of Salmonella Paratyphi A exhibited resistance to ciprofloxacin (MIC >0.5 mg/L). No resistance to azithromycin or the third-generation cephalosporins was detected.

Conclusions

WGS data provided a robust and informative approach for monitoring MDR and emerging resistance to ciprofloxacin in Salmonella Typhi and Salmonella Paratyphi. Phenotypic antimicrobial susceptibility testing continues to be performed to guide targeted individual patient treatment, but inferred AMR profiles from WGS data may be used for surveillance and to guide empirical therapy.

Changing trends of culture-positive typhoid fever and antimicrobial susceptibility in a tertiary care North Indian Hospital over the last decade

Purpose

The present study was undertaken to analyse the trend in prevalence of culture-positive typhoid fever during the last decade and to determine antimicrobial susceptibility profile of Salmonella Typhi and Salmonella Paratyphi A isolated from patients of enteric fever presenting to our hospital.

Methods

All the culture-positive enteric fever cases during 2005-2016 presenting to our Hospital were included in the study. Antimicrobial susceptibility was done against chloramphenicol, amoxicillin, co-trimoxazole, ciprofloxacin, ofloxacin, levofloxacin, pefloxacin, ceftriaxone and azithromycin as per corresponding CLSI guidelines for each year. We also analysed the proportion of culture positivity during 1993-2016 in light of the antibiotic consumption data from published literature.

Results

A total of 1066 strains-S. Typhi (772) and S. Paratyphi A (294) were isolated from the blood cultures during the study. A maximum number of cases were found in July-September. Antimicrobial susceptibility for chloramphenicol, amoxicillin and co-trimoxazole was found to be 87.9%, 75.5%, 87.3% for S. Typhi and 94.2%, 90.1% and 94.2% for S. Paratyphi A, respectively. Ciprofloxacin, ofloxacin and levofloxacin susceptibility were 71.3%, 70.8% and 70.9% for S. Typhi and 58.1%, 57.4% and 57.1% for S. Paratyphi A, respectively. Azithromycin susceptibility was 98.9% in S. Typhi. Although susceptibility to ceftriaxone and cefixime was 100% in our isolates, there is a continuous increase in ceftriaxone minimum inhibitory concentration (MIC)₅₀and MIC₉₀values over the time. The proportion of blood culture-positive cases during 1993-2016 ranged from a minimum of 0.0006 in 2014 to a maximum of 0.0087 in 1999.

Conclusion

We found that the most common etiological agent of enteric fever is S. Typhi causing the majority of cases from July to October in our region. MIC to ceftriaxone in typhoidal salmonellae is creeping towards resistance and more data are needed to understand the azithromycin susceptibility.

Pefloxacin as a surrogate marker for quinolone susceptibility in Salmonella enterica serovars Typhi & Paratyphi A in India

Background & objectives:

The emergence of resistance to fluoroquinolones in enteric fever despite the pathogen being susceptible by in vitro laboratory results, led to repeated changes in Clinical and Laboratory Standard Institute (CLSI) guidelines for this class of antibiotics to have specific and sensitive interpretative criteria. In 2015, CLSI added pefloxacin disk diffusion criteria as a surrogate marker for fluoroquinolone susceptibility. This study was carried out to evaluate the use of pefloxacin as a surrogate marker for ciprofloxacin, ofloxacin and levofloxacin susceptibility in clinical isolates of Salmonella Typhi and S. Paratyphi A.

Methods:

A total of 412 strains of S. Typhi and S. Paratyphi A were studied for pefloxacin disk diffusion test as a surrogate marker for susceptibility to ciprofloxacin, ofloxacin and levofloxacin as per CLSI and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Molecular mechanisms of resistance to fluoroquinolones were also determined and correlated with pefloxacin susceptibility breakpoints.

Results:

Of the total 412 strains, 34 were susceptible to ciprofloxacin and 33 each to levofloxacin and ofloxacin using CLSI minimum inhibitory concentration (MIC) breakpoints. There was a positive correlation between MICs with correlation coefficients 0.917, 0.896 and 0.958 for the association between ciprofloxacin and ofloxacin, ciprofloxacin and levofloxacin and ofloxacin and levofloxacin, respectively (P <0.001). The sensitivity, specificity and positive predictive value of pefloxacin as a surrogate marker using ciprofloxacin MIC as a gold standard were 100, 99.5 and 94.4 per cent, while 100, 99.2 and 91.7 per cent taking ofloxacin and levofloxacin MIC as gold standard. Mutations in target genes correlated with the pefloxacin susceptibility results.

Interpretation & conclusions:

Our results showed that pefloxacin served as a good surrogate marker for the detection of susceptibility to ciprofloxacin, ofloxacin and levofloxacin in S. Typhi and S. Paratyphi A. Further studies are required to confirm these findings.

Prediction of Phenotypic Antimicrobial Resistance Profiles From Whole Genome Sequences of Non-typhoidal Salmonella enterica

Surveillance of antimicrobial resistance (AMR) in non-typhoidal Salmonella enterica (NTS), is essential for monitoring transmission of resistance from the food chain to humans, and for establishing effective treatment protocols. We evaluated the prediction of phenotypic resistance in NTS from genotypic profiles derived from whole genome sequencing (WGS). Genes and chromosomal mutations responsible for phenotypic resistance were sought in WGS data from 3,491 NTS isolates received by Public Health England’s Gastrointestinal Bacteria Reference Unit between April 2014 and March 2015. Inferred genotypic AMR profiles were compared with phenotypic susceptibilities determined for fifteen antimicrobials using EUCAST guidelines. Discrepancies between phenotypic and genotypic profiles for one or more antimicrobials were detected for 76 isolates (2.18%) although only 88/52,365 (0.17%) isolate/antimicrobial combinations were discordant. Of the discrepant results, the largest number were associated with streptomycin (67.05%, n = 59). Pan-susceptibility was observed in 2,190 isolates (62.73%). Overall, resistance to tetracyclines was most common (26.27% of isolates, n = 917) followed by sulphonamides (23.72%, n = 828) and ampicillin (21.43%, n = 748). Multidrug resistance (MDR), i.e., resistance to three or more antimicrobial classes, was detected in 848 isolates (24.29%) with resistance to ampicillin, streptomycin, sulphonamides and tetracyclines being the most common MDR profile (n = 231; 27.24%). For isolates with this profile, all but one were S. Typhimurium and 94.81% (n = 219) had the resistance determinants bla_TEM-1,strA-strB, sul2 and tet(A). Extended-spectrum β-lactamase genes were identified in 41 isolates (1.17%) and multiple mutations in chromosomal genes associated with ciprofloxacin resistance in 82 isolates (2.35%). This study showed that WGS is suitable as a rapid means of determining AMR patterns of NTS for public health surveillance.

Treatment Response in Enteric Fever in an Era of Increasing Antimicrobial Resistance: An Individual Patient Data Analysis of 2092 Participants Enrolled into 4 Randomized, Controlled Trials in Nepal

Background.

Enteric fever, caused by Salmonella Typhi and Salmonella Paratyphi A, is the leading cause of bacterial febrile disease in South Asia.

Methods.

Individual data from 2092 patients with enteric fever randomized into 4 trials in Kathmandu, Nepal, were pooled. All trials compared gatifloxacin with 1 of the following comparator drugs: cefixime, chloramphenicol, ofloxacin, or ceftriaxone. Treatment outcomes were evaluated according to antimicrobial if S. Typhi/Paratyphi were isolated from blood. We additionally investigated the impact of changing bacterial antimicrobial susceptibility on outcome.

Results.

Overall, 855 (41%) patients had either S. Typhi (n = 581, 28%) or S. Paratyphi A (n = 274, 13%) cultured from blood. There were 139 (6.6%) treatment failures with 1 death. Except for the last trial with ceftriaxone, the fluoroquinolone gatifloxacin was associated with equivalent or better fever clearance times and lower treatment failure rates in comparison to all other antimicrobials. However, we additionally found that the minimum inhibitory concentrations (MICs) against fluoroquinolones have risen significantly since 2005 and were associated with increasing fever clearance times. Notably, all organisms were susceptible to ceftriaxone throughout the study period (2005-2014), and the MICs against azithromycin declined, confirming the utility of these alternative drugs for enteric fever treatment.

Conclusion.

The World Health Organization and local government health ministries in South Asia still recommend fluoroquinolones for enteric fever. This policy should change based on the evidence provided here. Rapid diagnostics are urgently required given the large numbers of suspected enteric fever patients with a negative culture.

Systematic Review of Antibiotic Resistance Rates Among Gram-Negative Bacteria in Children With Sepsis in Resource-Limited Countries

BACKGROUND

Gram-negative antimicrobial resistance (AMR) is of global concern, yet there are few reports from low- and low-middle-income countries, where antimicrobial choices are often limited.

METHODS

This study offers a systematic review of PubMed, Embase, and World Health Organization (WHO) regional databases of Gram-negative bacteremia in children in low- and low-middle-income countries reporting AMR since 2001.

RESULTS

Data included 30 studies comprising 71 326 children, of whom 7056 had positive blood cultures, and Gram-negative organisms were isolated in 4710 (66.8%). In neonates, Klebsiella pneumoniae median resistance to ampicillin was 94% and cephalosporins 84% in Asia; 100% and 50% in Africa. Large regional variations in resistance rates to commonly prescribed antibiotics for Salmonella spp. were identified. Multidrug resistance (resistance to ampicillin, chloramphenicol, and cotrimoxazole) was present in 30% (interquartile range [IQR], 0-59.6) in Asia and 75% (IQR, 30-85.4) in Africa.

CONCLUSIONS

There is a need for an international pediatric antimicrobial resistance surveillance system that collects local epidemiological data to improve the evidence base for the WHO guidance for childhood Gram-negative bacteremia.

The emergence of antibiotic resistance in typhoid fever

Typhoid fever, caused by Salmonella typhi, causes over 20 million cases annually, with at least 700,000 deaths. The main burden of disease is in developing countries, particularly the Indian Subcontinent and South East Asia. However, cases in returning travellers, immigrants and refugees in developed countries are not uncommon. Drug resistance is fast becoming a major problem in the management of this infection. Chloramphenicol resistance became established globally in the S.Typhi population after 1972 on plasmids of incompatibility group IncH. Multi-drug resistance defined as resistance to the three first-line agents used to treat typhoid fever, namely chloramphenicol, ampicillin and co-trimoxazole, and acquired on the same plasmid type, has been endemic in most of South East Asia and the Indian Subcontinent for many years. Resistance data from many endemic areas are sparse and with the increasing problem of reduced sensitivity to the fluoroquinolone antibiotics, empirical choice of antibiotics may be difficult. We review the historical aspects of the development of resistance and the current data available on the epidemiology of antibiotic resistance in S.Typhi.

WITHDRAWN: Azithromycin for treating uncomplicated typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Review status: Current question - no update intended. Azithromycin treatments are included in the review: Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever). (Thaver D, Zaidi AKM, Critchley JA, Azmatullah A, Madni SA, Bhutta ZA. Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever). Cochrane Database of Systematic Reviews 2008, Issue 4. Art. No.: CD004530. DOI: 10.1002/14651858.CD004530.pub3.)   This latter review is being updated, and will be published in late 2011.Enteric fever (typhoid and paratyphoid fever) is potentially fatal. Infection with drug-resistant strains of the causative organism Salmonella enterica serovar Typhi or Paratyphi increases morbidity and mortality. Azithromycin may have better outcomes in people with uncomplicated forms of the disease.

OBJECTIVES

To compare azithromycin with other antibiotics for treating uncomplicated enteric fever.

SEARCH STRATEGY

In August 2008, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2008, Issue 3), MEDLINE, EMBASE, LILACS, and mRCT. We also searched conference proceedings, reference lists, and contacted researchers and a pharmaceutical company.

SELECTION CRITERIA

Randomized controlled trials comparing azithromycin with other antibiotics for treating children and adults with uncomplicated enteric fever confirmed by cultures of S. Typhi or Paratyphi in blood and/or stool.

DATA COLLECTION AND ANALYSIS

Both authors independently extracted data and assessed the risk of bias. Dichotomous data were presented and compared using the odds ratio, and continuous data were reported as arithmetic means with standard deviations and were combined using the mean difference (MD). Both were presented with 95% confidence intervals (CI).

MAIN RESULTS

Seven trials involving 773 participants met the inclusion criteria. The trials used adequate methods to generate the allocation sequence and conceal allocation, and were open label. Three trials exclusively included adults, two included children, and two included both adults and children; all were hospital inpatients. One trial evaluated azithromycin against chloramphenicol and did not demonstrate a difference for any outcome (77 participants, 1 trial). When compared with fluoroquinolones in four trials, azithromycin significantly reduced clinical failure (OR 0.48, 95% CI 0.26 to 0.89; 564 participants, 4 trials) and duration of hospital stay (MD -1.04 days, 95% CI -1.73 to -0.34 days; 213 participants, 2 trials); all four trials included people with multiple-drug-resistant or nalidixic acid-resistant strains of S. Typhi or S. Paratyphi. We detected no statistically significant difference in the other outcomes. Compared with ceftriaxone, azithromycin significantly reduced relapse (OR 0.09, 95% CI 0.01 to 0.70; 132 participants, 2 trials) and not other outcome measures. Few adverse events were reported, and most were mild and self limiting.

AUTHORS' CONCLUSIONS

Azithromycin appears better than fluoroquinolone drugs in populations that included participants with drug-resistant strains. Azithromycin may perform better than ceftriaxone.

Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Typhoid and paratyphoid are febrile illnesses, due to a bacterial infection, which remain common in many low- and middle-income countries. The World Health Organization (WHO) currently recommends the fluoroquinolone antibiotics in areas with known resistance to the older first-line antibiotics.

OBJECTIVES

To evaluate fluoroquinolone antibiotics for treating children and adults with enteric fever.

SEARCH STRATEGY

We searched The Cochrane Infectious Disease Group Specialized Register (February 2011); Cochrane Central Register of Controlled Trials (CENTRAL), published in The Cochrane Library (2011, Issue 2); MEDLINE (1966 to February 2011); EMBASE (1974 to February 2011); and LILACS (1982 to February 2011). We also searched the metaRegister of Controlled Trials (mRCT) in February 2011.

SELECTION CRITERIA

Randomized controlled trials examining fluoroquinolone antibiotics, in people with blood, stool or bone marrow culture-confirmed enteric fever.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial's methodological quality and extracted data. We calculated risk ratios (RR) for dichotomous data and mean difference for continuous data with 95% confidence intervals (CI).Comparative effectiveness has been interpreted in the context of; length of treatment, dose, year of study, known levels of antibiotic resistance, or proxy measures of resistance such as the failure rate in the comparator arm.

MAIN RESULTS

Twenty-six studies, involving 3033 patients, are included in this review.Fluoroquinolones versus older antibiotics (chloramphenicol, co-trimoxazole, amoxicillin and ampicillin)In one study from Pakistan in 2003-04, high clinical failure rates were seen with both chloramphenicol and co-trimoxazole, although resistance was not confirmed microbiologically. A seven-day course of either ciprofloxacin or ofloxacin were found to be superior. Older studies of these comparisons failed to show a difference (six trials, 361 participants).In small studies conducted almost two decades ago, the fluoroquinolones were demonstrated to have fewer clinical failures than ampicillin and amoxicillin (two trials, 90 participants, RR 0.11, 95% CI 0.02 to 0.57).Fluoroquinolones versus current second-line options (ceftriaxone, cefalexin, and azithromycin)The two studies comparing a seven day course of oral fluoroquinolones with three days of intravenous ceftriaxone were too small to detect important differences between antibiotics should they exist (two trials, 89 participants).In Pakistan in 2003-04, no clinical or microbiological failures were seen with seven days of either ciprofloxacin, ofloxacin or cefixime (one trial, 139 participants). In Nepal in 2005, gatifloxacin reduced clinical failure and relapse compared to cefixime, despite a high prevalence of NaR in the study population (one trial, 158 participants, RR 0.04, 95% CI 0.01 to 0.31).Compared to a seven day course of azithromycin, a seven day course of ofloxacin had a higher rate of clinical failures in populations with both multi-drug resistance (MDR) and nalidixic acid resistance (NaR) enteric fever in Vietnam in 1998-2002 (two trials, 213 participants, RR 2.20, 95% CI 1.23 to 3.94). However, a more recent study from Vietnam in 2004-05, detected no difference between gatifloxacin and azithromycin with both drugs performing well (one trial, 287 participants).

AUTHORS' CONCLUSIONS

Generally, fluoroquinolones performed well in treating typhoid, and maybe superior to alternatives in some settings. However, we were unable to draw firm general conclusions on comparative contemporary effectiveness given that resistance changes over time, and many studies were small. Policy makers and clinicians need to consider local resistance patterns in choosing a fluoroquinolone or alternative.There is some evidence that the newest fluoroquinolone, gatifloxacin, remains effective in some regions where resistance to older fluoroquinolones has developed. However, the different fluoroquinolones have not been compared directly in trials in these settings.

Reemergence of Chloramphenicol Sensitivity in Enteric Fever

BACKGROUND

Enteric fever is a global health problem and rapidly developing resistance to various drugs makes the situation more alarming. Drug sensitivity in Salmonella enterica serovar typhi and Salmonella enterica serovar paratyphi A isolated from 45 blood culture positive cases of enteric fever was tested to determine in-vitro susceptibility pattern of prevalent strains in northern India.

METHODS

Strains isolated from 45 blood culture positive cases of typhoid and paratyphoid fever over a period of three years were studied and their sensitivity patterns to chloramphenicol, ampicillin, ciprofloxacin, ceftriaxone, nalidixic acid, amikacin and ofloxacin were analysed.

RESULTS

Our results show a high sensitivity of both Salmonella enterica serovar typhi (96%) and Salmonella enterica serovar paratyphi A (100%) to chloramphenicol. Sensitivity to ciprofloxacin and amikacin was 88% and 84% respectively. All the isolates were sensitive to ofloxacin, nalidixic acid and ceftriaxone. Sensitivity of Salmonella enterica serovar paratyphi A was 100% to chloramphenicol, ciprofloxacin, ofloxacin, nalidixic acid and ceftriaxone, 95% to amikacin and 30% to ampicillin. Overall 44 out of 45 isolates of Salmonellae were sensitive to chloramphenicol.

CONCLUSION

These findings suggest changing pattern of antibiotic resistance in enteric fever with reemergence of chloramphenicol sensitivity in northern India.

Gatifloxacin versus chloramphenicol for uncomplicated enteric fever: an open-label, randomised, controlled trial

BACKGROUND

We aimed to investigate whether gatifloxacin, a new generation and affordable fluoroquinolone, is better than chloramphenicol for the treatment of uncomplicated enteric fever in children and adults.

METHODS

We did an open-label randomised superiority trial at Patan Hospital, Kathmandu, Nepal, to investigate whether gatifloxacin is more effective than chloramphenicol for treating uncomplicated enteric fever. Children and adults clinically diagnosed with enteric fever received either gatifloxacin (10 mg/kg) once a day for 7 days, or chloramphenicol (75 mg/kg per day) in four divided doses for 14 days. Patients were randomly allocated treatment (1:1) in blocks of 50, without stratification. Allocations were placed in sealed envelopes opened by the study physician once a patient was enrolled into the trial. Masking was not possible because of the different formulations and ways of giving the two drugs. The primary outcome measure was treatment failure, which consisted of at least one of the following: persistent fever at day 10, need for rescue treatment, microbiological failure, relapse until day 31, and enteric-fever-related complications. The primary outcome was assessed in all patients randomly allocated treatment and reported separately for culture-positive patients and for all patients. Secondary outcome measures were fever clearance time, late relapse, and faecal carriage. The trial is registered on controlled-trials.com, number ISRCTN 53258327.

FINDINGS

844 patients with a median age of 16 (IQR 9-22) years were enrolled in the trial and randomly allocated a treatment. 352 patients had blood-culture-confirmed enteric fever: 175 were treated with chloramphenicol and 177 with gatifloxacin. 14 patients had treatment failure in the chloramphenicol group, compared with 12 in the gatifloxacin group (hazard ratio [HR] of time to failure 0·86, 95% CI 0·40-1·86, p=0·70). The median time to fever clearance was 3·95 days (95% CI 3·68-4·68) in the chloramphenicol group and 3·90 days (3·58-4·27) in the gatifloxacin group (HR 1·06, 0·86-1·32, p=0·59). At 1 month only, three of 148 patients were stool-culture positive in the chloramphenicol group and none in the gatifloxacin group. At the end of 3 months only one person had a positive stool culture in the chloramphenicol group. There were no other positive stool cultures even at the end of 6 months. Late relapses were noted in three of 175 patients in the culture-confirmed chloramphenicol group and two of 177 in the gatifloxacin group. There were no culture-positive relapses after day 62. 99 patients (24%) experienced 168 adverse events in the chloramphenicol group and 59 (14%) experienced 73 events in the gatifloxacin group.

INTERPRETATION

Although no more efficacious than chloramphenicol, gatifloxacin should be the preferred treatment for enteric fever in developing countries because of its shorter treatment duration and fewer adverse events.

FUNDING

Wellcome Trust.

Emerging Salmonella Paratyphi A enteric fever and changing trends in antimicrobial resistance pattern of salmonella in Shimla

This retrospective study incorporates a six years, six months (January 2000-June 2006) laboratory data comprising 258 isolates of Salmonella. Cultures were identified by standard methods. Salmonella enterica serotype Typhi (S.Typhi) was the more frequent serotype isolated i.e., 61.62% with the remaining 38.37% being Salmonella enterica serotype Paratyphi A (S. Paratyphi A). There was emergence of S. Paratyphi A as the predominant serotype in 2003-2004 with resurgence of serotype Typhi thereon. A total of 66.27% isolates were resistant to one or more antibiotics. MDR S. Typhi was 10.69% and while 13.13% were MDR S. Paratyphi A. There was decrease in resistance to ampicillin, cotrimoxazole in 2004 and nalidixic acid beyond 2005 and increase in resistance to cefuroxime. We also documented a decrease in resistance to ciprofloxacin after 2005.

Global trends in typhoid and paratyphoid Fever

Typhoid and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and Southeast Asia, where enteric fever is associated with poor sanitation and unsafe food and water. High-quality incidence data from Asia are underpinning efforts to expand access to typhoid vaccines. Efforts are underway to develop vaccines that are immunogenic in infants after a single dose and that can be produced locally in countries of endemicity. The growing importance of Salmonella enterica serotype Paratyphi A in Asia is concerning. Antimicrobial resistance has sequentially emerged to traditional first-line drugs, fluoroquinolones, and third-generation cephalosporins, posing patient treatment challenges. Azithromycin has proven to be an effective alternative for treatment of uncomplicated typhoid fever. The availability of full genome sequences for S. enterica serotype Typhi and S. enterica serotype Paratyphi A confirms their place as monomorphic, human-adapted pathogens vulnerable to control measures if international efforts can be redoubled.

A comparison of fluoroquinolones versus other antibiotics for treating enteric fever: meta-analysis

OBJECTIVES

To review evidence supporting use of fluoroquinolones as first line agents over other antibiotics for treating typhoid and paratyphoid fever (enteric fever).

DESIGN

Meta-analysis of randomised controlled trials.

DATA SOURCES

Cochrane Infectious Diseases Group specialised register, CENTRAL (issue 4, 2007), Medline (1966-2007), Embase (1974-2007), LILACS (1982-2007), selected conferences, reference lists, and ongoing trial register (November 2007). Review methods Trials comparing fluoroquinolones with chloramphenicol, cephalosporins, or azithromycin in culture-proven enteric fever were included. Two reviewers extracted data and assessed methodological quality. Odds ratios with 95% confidence intervals were estimated. Trials recruiting over 60% children were analysed separately from trials on adults. Primary outcomes studied were clinical failure, microbiological failure, and relapse.

RESULTS

Twenty trials were included. Trials were small and often of limited methodological quality. Only 10 trials concealed allocation and only three were blinded. In trials on adults, fluoroquinolones were not significantly different from chloramphenicol for clinical failure (594 participants) or microbiological failure (n=378), but reduced clinical relapse (odds ratio 0.14 (95% confidence interval 0.04 to 0.50), n=467, 6 trials). Azithromycin and fluoroquinolones were comparable (n=152, 2 trials). Compared with ceftriaxone, fluoroquinolones reduced clinical failure (0.08 (0.01 to 0.45), n=120, 3 trials) but not microbiological failure or relapse. Compared with cefixime, fluoroquinolones reduced clinical failure (0.05 (0.01 to 0.24), n=238, 2 trials) and relapse (0.18 (0.03 to 0.91), n=218, 2 trials). In trials on children infected with nalidixic acid resistant strains, older fluoroquinolones (ofloxacin) produced more clinical failures than azithromycin (2.67 (1.16 to 6.11), n=125, 1 trial), but there were no differences with newer fluoroquinolones (gatifloxacin, n=285, 1 trial). Fluoroquinolones and cefixime were not significantly different (n=82, 1 trial).

CONCLUSIONS

In adults, fluoroquinolones may be better than chloramphenicol for preventing clinical relapse. Data were limited for other comparisons, particularly for children.

Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Fluoroquinolones are recommended as first-line therapy for typhoid and paratyphoid fever (enteric fever), but how they compare with other antibiotics and different fluoroquinolones is unclear.

OBJECTIVES

To evaluate fluoroquinolone antibiotics for treating enteric fever in children and adults compared with other antibiotics, different fluoroquinolones, and different durations of fluoroquinolone treatment.

SEARCH STRATEGY

In November 2007, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2007, Issue 4), MEDLINE, EMBASE, LILACS, mRCT, conference proceedings, and reference lists.

SELECTION CRITERIA

Randomized controlled trials of fluoroquinolones in people with blood or bone marrow culture-confirmed enteric fever.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials' methodological quality and extracted data. We calculated odds ratios (OR) for dichotomous data with 95% confidence intervals (CI). We analysed trials with greater than 60% children separately from trials of mostly adults.

MAIN RESULTS

Of 38 included trials, 22 had unclear allocation concealment and 34 did not use blinding. Four trials included exclusively children, seven had both adults and children, and three studied outpatients.

ADULTS

Among primary outcomes (clinical failure, microbiological failure, and relapse), compared with chloramphenicol, fluoroquinolones were not statistically significantly different for clinical failure (594 participants) or microbiological failure (378 participants), but they reduced clinical relapse (OR 0.14, 95% CI 0.04 to 0.50; 467 participants, 6 trials). We detected no statistically significant difference versus co-trimoxazole (82 participants, 2 trials) or azithromycin (152 participants, 2 trials). Fluoroquinolones reduced clinical failure compared with ceftriaxone (OR 0.08, 95% CI 0.01 to 0.45; 120 participants, 3 trials), but not microbiological failure or relapse. Versus cefixime, fluoroquinolones reduced clinical failure (OR 0.05, 95% CI 0.01 to 0.24; 238 participants; 2 trials) and relapse (OR 0.18, 95% CI 0.03 to 0.91; 218 participants, 2 trials).

CHILDREN

In children with high proportions of nalidixic acid-resistant strains, older fluoroquinolones increased clinical failures compared with azithromycin (OR 2.67, 95% CI 1.16 to 6.11; 125 participants, 1 trial), with no differences using newer fluoroquinolones (285 participants, 1 trial). Fluoroquinolones and cefixime were not statistically significantly different (82 participants, 1 trial). Trials comparing different durations of fluoroquinolone treatment were not statistically significantly different (889 participants, 9 trials). Norfloxacin had more clinical failures than other fluoroquinolones (417 participants, 5 trials).

AUTHORS' CONCLUSIONS

Trials were small and methodological quality varied. In adults, fluoroquinolones may be better for reducing clinical relapse rates compared to chloramphenicol. Data are limited for other comparisons, particularly in children.

Azithromycin for treating uncomplicated typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Enteric fever (typhoid and paratyphoid fever) is potentially fatal. Infection with drug-resistant strains of the causative organism Salmonella enterica serovar Typhi or Paratyphi increases morbidity and mortality. Azithromycin may have better outcomes in people with uncomplicated forms of the disease.

OBJECTIVES

To compare azithromycin with other antibiotics for treating uncomplicated enteric fever.

SEARCH STRATEGY

In August 2008, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2008, Issue 3), MEDLINE, EMBASE, LILACS, and mRCT. We also searched conference proceedings, reference lists, and contacted researchers and a pharmaceutical company.

SELECTION CRITERIA

Randomized controlled trials comparing azithromycin with other antibiotics for treating children and adults with uncomplicated enteric fever confirmed by cultures of S. Typhi or Paratyphi in blood and/or stool.

DATA COLLECTION AND ANALYSIS

Both authors independently extracted data and assessed the risk of bias. Dichotomous data were presented and compared using the odds ratio, and continuous data were reported as arithmetic means with standard deviations and were combined using the mean difference (MD). Both were presented with 95% confidence intervals (CI).

MAIN RESULTS

Seven trials involving 773 participants met the inclusion criteria. The trials used adequate methods to generate the allocation sequence and conceal allocation, and were open label. Three trials exclusively included adults, two included children, and two included both adults and children; all were hospital inpatients. One trial evaluated azithromycin against chloramphenicol and did not demonstrate a difference for any outcome (77 participants, 1 trial). When compared with fluoroquinolones in four trials, azithromycin significantly reduced clinical failure (OR 0.48, 95% CI 0.26 to 0.89; 564 participants, 4 trials) and duration of hospital stay (MD -1.04 days, 95% CI -1.73 to -0.34 days; 213 participants, 2 trials); all four trials included people with multiple-drug-resistant or nalidixic acid-resistant strains of S. Typhi or S. Paratyphi. We detected no statistically significant difference in the other outcomes. Compared with ceftriaxone, azithromycin significantly reduced relapse (OR 0.09, 95% CI 0.01 to 0.70; 132 participants, 2 trials) and not other outcome measures. Few adverse events were reported, and most were mild and self limiting.

AUTHORS' CONCLUSIONS

Azithromycin appears better than fluoroquinolone drugs in populations that included participants with drug-resistant strains. Azithromycin may perform better than ceftriaxone.

Surveillance of antimicrobial resistance of Salmonella enterica serotype Typhi in seven Asian countries

Two hundred and four Salmonella enterica serotype Typhi (S. Typhi) isolates were collected from seven Asian countries during 2002–2004. Multidrug-resistant S. Typhi (resistant to ⩾3 antibiotics) was detected in 84 (41·2%) isolates and 142 (69·6%) showed reduced susceptibility to ciprofloxacin (minimum inhibitory concentration=0·125–1·0 mg/l). This study highlights the worsening situation of antimicrobial resistance of S. Typhi in Asia.

Multidrug-resistant typhoid fever

OBJECTIVE

To study the epidemiological pattern, clinical picture, the recent trends of multidrug-resistant typhoid fever (MDRTF), and therapeutic response of ofloxacin and ceftriaxone in MDRTF.

METHODS

The present prospective randomized controlled parallel study was conducted on 93 blood culture-proven Salmonella typhi children. All MDRTF cases were randomized to treatment with ofloxacin or ceftriaxone.

RESULTS

Of 93 children, 62 (66.6%) were MDRTF. 24 cases were below 5 years, 26 between 5-10 years and 12 were above 10 years. Male to female ratio was 1.85: 1. Majority of cases came from lower middle socio-economic classes with poor personal hygiene. Fever was the main presenting symptom. Hepatomegaly and splenomegaly was present in 88% and 46% cases respectively. 19 (30.6%) cases developed complications. Mean defervescence time with ceftriaxone and ofloxacin was 4.258 and 4.968 days respectively.

CONCLUSION

MDRTF is still emerging as serious public and therapeutic challenge. Ceftriaxone is well-tolerated and effective drug but expensive whereas ofloxacin is safe, cost-effective and therapeutic alternative in treatment of MDRTF in children with comparable efficacy to ceftriaxone.

Antibiogram pattern and seasonality of Salmonella serotypes in a North Indian tertiary care hospital

The antibiogram pattern and seasonal distribution of Salmonella serotypes were analysed retrospectively over a 6-year period from January 1999 to December 2004. Blood cultures received in the Bacteriology Laboratory were processed by standard procedures and the Salmonella spp. isolates were identified with specific antisera and standard biochemical tests. Antimicrobial susceptibility testing was carried out by a standard disc diffusion method and the minimum inhibitory concentration (MIC) of ciprofloxacin for 332 representative Salmonella isolates was determined by E test. Salmonella Typhi (75.7%) was the predominant serotype among 830 Salmonella spp. isolated during the study period followed by S. Paratyphi A (23.8%). The maximum number of enteric fever cases occurred during April-June (dry season) followed by July-September (monsoon season). There was a decrease in multidrug-resistant (MDR) S. Typhi, but MDR S. Paratyphi A isolates increased. There was also a dramatic increase in nalidixic acid-resistant isolates. All isolates were susceptible to third-generation cephalosporins and ciprofloxacin except one S. Typhi strain which demonstrated high-level ciprofloxacin resistance with a MIC of 16 mug/ml. A knowledge of the seasonal distribution and antibiotic resistance pattern of Salmonella in a particular geographical region is helpful in the delineation of appropriate control measures required for prevention of enteric fever.

Typhoid and paratyphoid fever

Typhoid fever is estimated to have caused 21.6 million illnesses and 216,500 deaths globally in 2000, affecting all ages. There is also one case of paratyphoid fever for every four of typhoid. The global emergence of multidrug-resistant strains and of strains with reduced susceptibility to fluoroquinolones is of great concern. We discuss the occurrence of poor clinical response to fluoroquinolones despite disc sensitivity. Developments are being made in our understanding of the molecular pathogenesis, and genomic and proteomic studies reveal the possibility of new targets for diagnosis and treatment. Further, we review guidelines for use of diagnostic tests and for selection of antimicrobials in varying clinical situations. The importance of safe water, sanitation, and immunisation in the presence of increasing antibiotic resistance is paramount. Routine immunisation of school-age children with Vi or Ty21a vaccine is recommended for countries endemic for typhoid. Vi vaccine should be used for 2-5 year-old children in highly endemic settings.

Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Fluoroquinolones are recommended as first-line therapy for typhoid and paratyphoid fever, but how they compare with other cheaper antibiotics and different fluoroquinolones is unclear.

OBJECTIVES

To evaluate fluoroquinolone antibiotics for treating enteric fever in children and adults compared with other antibiotics, different fluoroquinolones, and different treatment durations of the same fluoroquinolone.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (August 2004), CENTRAL (The Cochrane Library Issue 3, 2004), MEDLINE (1966 to August 2004), EMBASE (1974 to August 2004), LILACS (1982 to August 2004), conference proceedings, reference lists, and contacted researchers.

SELECTION CRITERIA

Randomized controlled trials of fluoroquinolones in people with blood or bone marrow culture-confirmed enteric fever.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality of trials and extracted data. We calculated the odds ratio (OR) for dichotomous data with 95% confidence intervals. We analysed norfloxacin separately.

MAIN RESULTS

Thirty-three trials met the inclusion criteria; 22 had unclear allocation concealment, and 29 were not blinded. Three trials exclusively included children, and two studied outpatients. The main analysis examined clinical failure, microbiological failure, and relapse. Compared with chloramphenicol, fluoroquinolones were not statistically significantly different for clinical (544 participants) or microbiological failure (378 participants) in adults; they reduced clinically diagnosed relapse in adults (OR 0.14, 0.04 to 0.50; 467 participants, 6 trials), but this was not statistically significant in participants with blood culture-confirmed relapse (121 participants, 2 trials). Compared with co-trimoxazole, we detected no statistically significant difference (82 participants, 2 trials). Among adults, fluoroquinolones reduced clinical failure compared with ceftriaxone (OR 0.08, 0.01 to 0.45; 120 participants, 3 trials), but showed no difference for microbiological failure or relapse. We detected no statistically significant difference between fluoroquinolones and cefixime (80 participants, 1 trial) or azithromycin (152 participants, 2 trials). In trials of hospitalized children, fluoroquinolones were not statistically significantly different from ceftriaxone (60 participants, 1 trial, involving norfloxacin) or cefixime (82 participants, 1 trial). Norfloxacin had more clinical failures than other fluoroquinolones (417 participants, 5 trials). Trials comparing different durations of fluoroquinolone treatment showed no statistically significant differences (693 participants, 8 trials).

AUTHORS' CONCLUSIONS

Many trials were small, and methodological quality varied widely. Although enteric fever most commonly affects children, trials in this group were particularly sparse. Insufficient data in all comparisons preclude any firm conclusions to be made regarding superiority of fluoroquinolones over first-line antibiotics in children and adults.

The emergence of multidrug resistance to antimicrobial agents for the treatment of typhoid fever

Resistance to chloramphenicol was reported in Salmonella Typhi in 1950 but it was not until 22 years later that the first outbreaks of chloramphenicol-resistant typhoid fever occurred. Multidrug-resistant (MDR) Salmonella Typhi emerged in the 1980s and today has an almost worldwide distribution. Genome analysis of Salmonella Typhi strain CT18, an MDR isolate from a patient admitted to The Centre for Tropical Diseases, Ho Chi Minh City, Viet Nam, in December 1993 revealed that the resistance plasmid pHCM1 is very closely related to plasmid R27 which was first isolated in 1961. There is a core region shared by the two plasmids with five regions of variation. Two of these regions contain the genes encoding resistance. The largest region is 34.955 kbp in length, is bordered by two almost identical IS10 elements and contains several integron-like structures including a truncated Tn10 element. The second region is 14.75I kbp and encodes a trimethoprim-resistance gene, dfrA14, associated with a class one integrase. Restriction enzyme analysis has shown that the variation in Salmonella Typhi plasmids, collected during the emergence of resistant Salmonella Typhi in Viet Nam, maps to five variable regions. These regions appear to be hot spots for DNA acquisition in IncHI1 plasmids.

Short‐Course Azithromycin for the Treatment of Uncomplicated Typhoid Fever in Children and Adolescents

We studied 149 children and adolescents 3-17 years of age with clinical typhoid fever who were treated with either oral azithromycin (20 mg/kg per day; maximum dose, 1000 mg/day) or intravenous ceftriaxone (75 mg/day; maximum dose, 2.5 g/day) daily for 5 days. Blood and stool specimens were obtained for culture before the initiation of therapy and were repeated on days 4 and 8 of treatment. Isolation of Salmonella enterica serovar Typhi or S. enterica serovar Paratyphi from the initial culture was required for inclusion in the final analysis. S. Typhi was isolated from 68 patients, 32 of whom were receiving azithromycin. Cure was achieved in 30 (94%) of 32 patients in the azithromycin group and in 35 (97%) of 36 patients in the ceftriaxone group (P=NS). Mean time to clearance of bacteremia was longer in the azithromycin group than in the ceftriaxone group. No patient who received azithromycin had a relapse, compared with 6 patients who received ceftriaxone. A 5-day course of azithromycin was found to be an effective treatment for uncomplicated typhoid fever in children and adolescents.

Trends of multiple-drug resistance among Salmonella serotype Typhi isolates during a 14-year period in Egypt

A total of 853 isolates of Salmonella serotype Typhi recovered from patients with typhoid fever who were admitted to a major infectious disease hospital in Cairo, Egypt, from 1987 through 2000 underwent antibiotic susceptibility testing to determine multiple-drug resistance. The observed resurgence of chloramphenicol susceptibility (P=.002) may suggest reuse of this drug for the treatment of typhoid fever in Egypt.

Identification of bacterial genes required for in-vivo survival

Genetic approaches used for in-vivo studies of bacterial pathogenesis are providing insights into how bacteria disrupt host defences and exploit host molecules for their own advantage. Signature tagged mutagenesis (STM) provides a means of identifying the genes involved in the process of infection, particularly those genes that are important for bacterial proliferation in-vivo. In this review, the application of STM to the understanding of bacterial pathogenesis and findings from work on three human pathogens, Salmonella typhimurium, Mycobacterium tuberculosis and Neisseria meningitidis, are discussed. The next challenge is to understand how these and other genes influence the infective process at the molecular and cellular levels and to design novel interventions to block the progression of disease.

Clinical and bacteriological profiles of patients with typhoid fever treated during 1975-1998 in the Tokyo Metropolitan Komagome Hospital

Patients with typhoid fever presenting to the Tokyo Metropolitan Komagome Hospital during the period 1975-1998 were retrospectively investigated. All cases were diagnosed by a positive culture for Salmonella typhi in either of their clinical specimens. Of the total number of 130 patients, 57% contracted the disease abroad; this population increased in later years as the total numbers of cases decreased. The period from disease onset to diagnosis averaged 14 days with 20% of the cases requiring over three weeks to establish a diagnosis. As for symptomatology relative bradycardia was seen in less than half of the cases, and rose spots or splenomegaly in less than one third. A positive blood culture was the most frequent test establishing the diagnosis followed by a positive stool culture. Intestinal bleeding was recognized in as many as 35 cases (27%) and even intestinal perforation occurred in two cases (1.5%). Chloramphenicol was most commonly employed during the early study period, however, during the late period it was replaced by fluoroquinolones. The clinical cure rate was 98% with regimens that include fluoroquinolones/quinolone; however it was 87% with the other antimicrobial regimens. Bacteriological relapse occurred in 25% of the non-fluoroquinolone group while only in 2.0% in the fluoroquinolone/quinolone group. Four strains of Salmonella typhi that were multi-resistant to chloramphenicol, ampicillin and cotrimoxazole were isolated in travelers from Asia. Early diagnosis by appropriate bacteriological examination regardless of classical symptomatology should be stressed and the use of fluoroquinolones is warranted in the treatment of typhoid fever.

Treatment of gastrointestinal infections

Studies aimed at improving treatment strategies for patients with acute diarrhea have included the clinical testing of modifications to the standard oral rehydration solution. A malabsorbed carbohydrate has been found to improve resuscitation, probably through the recruitment of colonic absorptive capacity. A reduced osmolarity solution is safe in adults and as effective as the standard solution. For non-nursing infants, increasing the frequency of feeding with reduced volume results in comparable total caloric intake and diminishes the risk of prolonged diarrhea. Increasing resistance of important enteric pathogens to inexpensive and newer antibiotics continues to be a concern. Reports from Asia of decreased Salmonella typhi resistance to chloramphenicol, attributed to restricted antibiotic usage, may indicate a reversal of the usual trend. A strategy to block the action of shiga toxins in the gut through the use of recombinant bacteria has shown promise in a mouse model. A small but well-designed study supported the use of either norfloxacin or amoxicillin-clavulanic acid in the treatment of small bowel overgrowth syndrome. Studies exploring passive immunity strategies for the treatment of Escherichia coli, Cryptosporidium, and Candida infections have reported variable levels of success.