Salmonella enterica Serovar Paratyphi A and S. enterica Serovar Typhi Cause Indistinguishable Clinical Syndromes in Kathmandu, Nepal

Enteric fever in a UK regional infectious diseases unit: a 10 year retrospective review

INTRODUCTION

Enteric fever is an increasingly common diagnosis in returning travellers in the UK.

METHODS

We performed a retrospective descriptive study of culture-confirmed cases of enteric fever admitted to University Hospitals Leicester, UK between January 1999 and April 2009.

RESULTS

100 cases of enteric fever were identified in adults (n = 76) and children (n = 24). The median age of adult subjects was 38 (range 18-71) and 55% were male. Of the 61 adult cases with notes available, 60 (98.3%) were of Asian ethnicity and 56 (92%) had a recent travel history, principally to the Indian Subcontinent. Symptoms included fever (100%), headache (62%), diarrhoea (59%) and abdominal pain (44%). Common examination findings included pyrexia and mild generalized abdominal tenderness. Mild hyponatraemia, transaminitis and a normal white cell count were commonly identified. Reduced ciprofloxacin sensitivity was common and increased over the study period. Median fever clearance time was 6 days, and treatment failure occurred in 20% of cases. Relapse occurred in 2 patients. Complications were unusual, and one patient died.

DISCUSSION

Patients with enteric fever presented with a non-specific febrile illness within one month after returning from travel, and most had an uncomplicated clinical course. Increasing ciprofloxacin insensitivity was the likely explanation for a high treatment failure rate and this agent can no longer recommended as empirical treatment.

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.

Increasing rates and clinical consequences of nalidixic acid-resistant isolates causing enteric fever in returned travellers: an 18-year experience

The purpose of this study was to examine the rate and clinical consequences of nalidixic acid-resistant (NAR) isolates in travellers with enteric fever presenting to a hospital in a developed country. We retrospectively examined microbiologically confirmed cases of enteric fever in adult returned travellers over an 18-year period presenting to two tertiary referral hospitals in Melbourne, Australia. There were 59 cases of Salmonella typhi infection, 43 cases of S. paratyphi A infection and two cases of S. paratyphi B infection. Most patients reported recent travel to India (36%) or Indonesia (29%). NAR isolates were commonly encountered (41% of all isolates), particularly from India (75%), Pakistan (80%) and Bangladesh (60%). The number of NAR isolates increased progressively after 2003. Patients with NAR isolates had prolonged mean fever clearance time (5.6 vs. 3.3 days, P = 0.03) and prolonged hospital stay (7.9 vs. 5.7 days, P = 0.02) compared to non-resistant isolates. This represents the largest report of NAR enteric fever in returned travellers. NAR isolates predominate in cases of enteric fever from South Asia and result in prolonged fever clearance time and hospital stay. Empiric therapy with alternative antibiotics such as ceftriaxone or azithromycin should be considered in patients with suspected enteric fever from this region.

Murine typhus and febrile illness, Nepal

Murine typhus was diagnosed by PCR in 50 (7%) of 756 adults with febrile illness seeking treatment at Patan Hospital in Kathmandu, Nepal. Of patients with murine typhus, 64% were women, 86% were residents of Kathmandu, and 90% were unwell during the winter. No characteristics clearly distinguished typhus patients from those with blood culture–positive enteric fever.

[Pneumonia in a traveller coming back from Asia]

A case of Salmonella paratyphi A infection was diagnosed late in a patient treated for febrile pneumonia after his returning from India. This case was remarkable in two aspects: first, it illustrated the reemergence of S.paratyphi A infections in people having traveled to India, with increasing fluoroquinolone resistance, and second the difficulty of diagnosing this disease, since the patient was initially treated for pneumonia and flu-like syndrome. Salmonella typhi or paratyphi infections should be evoked in case of persistent fever in patients having traveled to endemic areas, even if digestive signs are absent. Furthermore, choosing an empiric antibiotic treatment with fluoroquinolones could lead to treatment failure if the patient traveled in a country where fluoroquinolone resistance is high, as in Asia and especially in India.

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.

A patient with paratyphoid A fever: an emerging problem in Asia and not always a benign disease

A 15-year-old Nepalese boy with fever was thought to have enteric fever and started on cefixime. His blood culture grew Salmonella paratyphoid A. On the sixth day, he developed gastrointestinal bleeding, disseminated intravascular coagulation, and later, acute respiratory distress syndrome. He succumbed to his illness despite treatment in the intensive care unit with ceftriaxone, intravenous fluids, and mechanical ventilation. Salmonella paratyphoid A, for which there is no commercial vaccine, may not be a benign disease as perceived, and cefixime that is recommended for enteric fever may be an ineffective choice.

A multi-center randomised controlled trial of gatifloxacin versus azithromycin for the treatment of uncomplicated typhoid fever in children and adults in Vietnam

BACKGROUND

Drug resistant typhoid fever is a major clinical problem globally. Many of the first line antibiotics, including the older generation fluoroquinolones, ciprofloxacin and ofloxacin, are failing.

OBJECTIVES

We performed a randomised controlled trial to compare the efficacy and safety of gatifloxacin (10 mg/kg/day) versus azithromycin (20 mg/kg/day) as a once daily oral dose for 7 days for the treatment of uncomplicated typhoid fever in children and adults in Vietnam.

METHODS

An open-label multi-centre randomised trial with pre-specified per protocol analysis and intention to treat analysis was conducted. The primary outcome was fever clearance time, the secondary outcome was overall treatment failure (clinical or microbiological failure, development of typhoid fever-related complications, relapse or faecal carriage of S. typhi).

PRINCIPAL FINDINGS

We enrolled 358 children and adults with suspected typhoid fever. There was no death in the study. 287 patients had blood culture confirmed typhoid fever, 145 patients received gatifloxacin and 142 patients received azithromycin. The median FCT was 106 hours in both treatment arms (95% Confidence Interval [CI]; 94-118 hours for gatifloxacin versus 88-112 hours for azithromycin), (logrank test p = 0.984, HR [95% CI] = 1.0 [0.80-1.26]). Overall treatment failure occurred in 13/145 (9%) patients in the gatifloxacin group and 13/140 (9.3%) patients in the azithromycin group, (logrank test p = 0.854, HR [95% CI] = 0.93 [0.43-2.0]). 96% (254/263) of the Salmonella enterica serovar Typhi isolates were resistant to nalidixic acid and 58% (153/263) were multidrug resistant.

CONCLUSIONS

Both antibiotics showed an excellent efficacy and safety profile. Both gatifloxacin and azithromycin can be recommended for the treatment of typhoid fever particularly in regions with high rates of multidrug and nalidixic acid resistance. The cost of a 7-day treatment course of gatifloxacin is approximately one third of the cost of azithromycin in Vietnam.

TRIAL REGISTRATION

Controlled-Trials.com ISRCTN67946944.

Comparisons of predictors for typhoid and paratyphoid fever in Kolkata, India

Background:

Exposure of the individual to contaminated food or water correlates closely with the risk for enteric fever. Since public health interventions such as water improvement or vaccination campaigns are implemented for groups of individuals we were interested whether risk factors not only for the individual but for households, neighbourhoods and larger areas can be recognised?

Methods:

We conducted a large enteric fever surveillance study and analyzed factors which correlate with enteric fever on an individual level and factors associated with high and low risk areas with enteric fever incidence. Individual level data were linked to a population based geographic information systems. Individual and household level variables were fitted in Generalized Estimating Equations (GEE) with the logit link function to take into account the likelihood that household factors correlated within household members.

Results:

Over a 12-month period 80 typhoid fever cases and 47 paratyphoid fever cases were detected among 56,946 residents in two bustees (slums) of Kolkata, India. The incidence of paratyphoid fever was lower (0.8/1000/year), and the mean age of paratyphoid patients was older (17.1 years) than for typhoid fever (incidence 1.4/1000/year, mean age 14.7 years). Residents in areas with a high risk for typhoid fever had lower literacy rates and economic status, bigger household size, and resided closer to waterbodies and study treatment centers than residents in low risk areas.

Conclusion:

There was a close correlation between the characteristics detected based on individual cases and characteristics associated with high incidence areas. Because the comparison of risk factors of populations living in high versus low risk areas is statistically very powerful this methodology holds promise to detect risk factors associated with diseases using geographic information systems.

Emergence of multidrug-resistant Salmonella enterica serovar Typhi associated with a class 1 integron carrying the dfrA7 gene cassette in Nepal

A total of 121 Salmonella enterica serovars Typhi and Paratyphi A isolated from enteric fever patients at a university hospital in Nepal between February 2004 and January 2006 were tested for their antimicrobial susceptibility. The occurrence and cassette content of integrons as well as the molecular mechanisms of resistance among the multidrug-resistant (MDR) S. Typhi were evaluated. Thirty-nine percent of the isolates were susceptible to all the antimicrobial agents tested. Seven of the S. Typhi strains were MDR. None of the 121 S. enterica isolates were resistant to ciprofloxacin, cefazolin, rifampicin or kanamycin. All MDR S. Typhi isolates contained a class 1 integron with a single cassette, dfrA7, conferring resistance to trimethoprim. Pulsed-field gel electrophoresis (PFGE) of XbaI-generated genomic restriction fragments yielded 12 different patterns. Five of the seven MDR isolates containing class 1 integrons had an identical PFGE pattern. Resistance to sulfamethoxazole, streptomycin, ampicillin, tetracycline and chloramphenicol was mediated by sul1, strA-strB, blaTEM-like, tetB and catA genes, respectively. To the best of our knowledge, this is the first report of integron-associated multidrug resistance as well as the first molecular characterisation of the mechanism of resistance of S. Typhi isolated from Nepal. This study indicates the spread of integron-associated multidrug resistance in S. Typhi in Nepal.

An open randomized comparison of gatifloxacin versus cefixime for the treatment of uncomplicated enteric fever

Objective

To assess the efficacy of gatifloxacin versus cefixime in the treatment of uncomplicated culture positive enteric fever.

Design

A randomized, open-label, active control trial with two parallel arms.

Setting

Emergency Room and Outpatient Clinics in Patan Hospital, Lagankhel, Lalitpur, Nepal.

Participants

Patients with clinically diagnosed uncomplicated enteric fever meeting the inclusion criteria.

Interventions

Patients were allocated to receive one of two drugs, Gatifloxacin or Cefixime. The dosages used were Gatifloxacin 10 mg/kg, given once daily for 7 days, or Cefixime 20 mg/kg/day given in two divided doses for 7 days.

Outcome Measures

The primary outcome measure was fever clearance time. The secondary outcome measure was overall treatment failure (acute treatment failure and relapse).

Results

Randomization was carried out in 390 patients before enrollment was suspended on the advice of the independent data safety monitoring board due to significant differences in both primary and secondary outcome measures in the two arms and the attainment of a priori defined endpoints. Median (95% confidence interval) fever clearance times were 92 hours (84–114 hours) for gatifloxacin recipients and 138 hours (105–164 hours) for cefixime-treated patients (Hazard Ratio[95%CI] = 2.171 [1.545–3.051], p<0.0001). 19 out of 70 (27%) patients who completed the 7 day trial had acute clinical failure in the cefixime group as compared to 1 out of 88 patients (1%) in gatifloxacin group(Odds Ratio [95%CI] = 0.031 [0.004 – 0.237], p<0.001). Overall treatment failure patients (relapsed patients plus acute treatment failure patients plus death) numbered 29. They were determined to be (95% confidence interval) 37.6 % (27.14%–50.2%) in the cefixime group and 3.5% (2.2%–11.5%) in the gatifloxacin group (HR[95%CI] = 0.084 [0.025–0.280], p<0.0001). There was one death in the cefixime group.

Conclusions

Based on this study, gatifloxacin is a better treatment for uncomplicated enteric fever as compared to cefixime.

Trial Registration

Current Controlled Trials ISRCTN75784880

Multidrug-resistant Salmonella enterica serovar paratyphi A harbors IncHI1 plasmids similar to those found in serovar typhi

Salmonella enterica serovars Typhi and Paratyphi A cause systemic infections in humans which are referred to as enteric fever. Multidrug-resistant (MDR) serovar Typhi isolates emerged in the 1980s, and in recent years MDR serovar Paratyphi A infections have become established as a significant problem across Asia. MDR in serovar Typhi is almost invariably associated with IncHI1 plasmids, but the genetic basis of MDR in serovar Paratyphi A has remained predominantly undefined. The DNA sequence of an IncHI1 plasmid, pAKU_1, encoding MDR in a serovar Paratyphi A strain has been determined. Significantly, this plasmid shares a common IncHI1-associated DNA backbone with the serovar Typhi plasmid pHCM1 and an S. enterica serovar Typhimurium plasmid pR27. Plasmids pAKU_1 and pHCM1 share 14 antibiotic resistance genes encoded within similar mobile elements, which appear to form a 24-kb composite transposon that has transferred as a single unit into different positions into their IncHI1 backbones. Thus, these plasmids have acquired similar antibiotic resistance genes independently via the horizontal transfer of mobile DNA elements. Furthermore, two IncHI1 plasmids from a Vietnamese isolate of serovar Typhi were found to contain features of the backbone sequence of pAKU_1 rather than pHCM1, with the composite transposon inserted in the same location as in the pAKU_1 sequence. Our data show that these serovar Typhi and Paratyphi A IncHI1 plasmids share highly conserved core DNA and have acquired similar mobile elements encoding antibiotic resistance genes in past decades.

Fever after a stay in the tropics: diagnostic predictors of the leading tropical conditions

Differential diagnosis of fever in travelers returning from the tropics is extremely diverse. Apart from the travel destination, other diagnostic predictors of tropical infections are poorly documented in returning travelers. From April 2000 to December 2005, we prospectively enrolled all patients presenting at our referral centers with fever within 1 year after visiting a tropical or subtropical area. For clinical relevance, the diagnostic predictors of the leading tropical conditions were particularly investigated in the febrile episodes occurring during travel or within 1 month after return (defined as early-onset fever). In total, 2071 fever episodes were included, occurring in 1962 patients. Most patients were western travelers (60%) or expatriates (15%). Regions of exposure were mainly sub-Saharan Africa (68%) and southern Asia/Pacific (14%). Early-onset fever accounted for 1619 episodes (78%). Most tropical infections were related to specific travel destinations. Malaria (mainly Plasmodium falciparum) was strongly predicted by the following features: enlarged spleen, thrombocytopenia (platelet count <150 x 10(3)/microL), fever without localizing symptoms, and hyperbilirubinemia (total bilirubin level >or=1.3 mg/dL). When malaria had been ruled out, main predictors were skin rash and skin ulcer for rickettsial infection (mainly African tick bite fever); skin rash, thrombocytopenia, and leukopenia (leukocyte count <4 x 10(3)/microL) for dengue; eosinophil count >or=0.5 x 10(3)/microL for acute schistosomiasis; and enlarged spleen and elevated alanine aminotransferase level (>or=70 IU/L) for enteric fever. The initial clinical and laboratory assessment can help in selecting appropriate investigations and empiric treatments for patients with imported fever.