- Research article
- Open Access
- Open Peer Review
This article has Open Peer Review reports available.
Risk factors for the development of severe typhoid fever in Vietnam
© Parry et al.; licensee BioMed Central Ltd. 2014
Received: 7 October 2013
Accepted: 30 January 2014
Published: 10 February 2014
Typhoid fever is a systemic infection caused by the bacterium Salmonella enterica serovar Typhi. Age, sex, prolonged duration of illness, and infection with an antimicrobial resistant organism have been proposed risk factors for the development of severe disease or fatality in typhoid fever.
We analysed clinical data from 581 patients consecutively admitted with culture confirmed typhoid fever to two hospitals in Vietnam during two periods in 1993–1995 and 1997–1999. These periods spanned a change in the antimicrobial resistance phenotypes of the infecting organisms i.e. fully susceptible to standard antimicrobials, resistance to chloramphenicol, ampicillin and trimethoprim-sulphamethoxazole (multidrug resistant, MDR), and intermediate susceptibility to ciprofloxacin (nalidixic acid resistant). Age, sex, duration of illness prior to admission, hospital location and the presence of MDR or intermediate ciprofloxacin susceptibility in the infecting organism were examined by logistic regression analysis to identify factors independently associated with severe typhoid at the time of hospital admission.
The prevalence of severe typhoid was 15.5% (90/581) and included: gastrointestinal bleeding (43; 7.4%); hepatitis (29; 5.0%); encephalopathy (16; 2.8%); myocarditis (12; 2.1%); intestinal perforation (6; 1.0%); haemodynamic shock (5; 0.9%), and death (3; 0.5%). Severe disease was more common with increasing age, in those with a longer duration of illness and in patients infected with an organism exhibiting intermediate susceptibility to ciprofloxacin. Notably an MDR phenotype was not associated with severe disease. Severe disease was independently associated with infection with an organism with an intermediate susceptibility to ciprofloxacin (AOR 1.90; 95% CI 1.18-3.07; p = 0.009) and male sex (AOR 1.61 (1.00-2.57; p = 0.035).
In this group of patients hospitalised with typhoid fever infection with an organism with intermediate susceptibility to ciprofloxacin was independently associated with disease severity. During this period many patients were being treated with fluoroquinolones prior to hospital admission. Ciprofloxacin and ofloxacin should be used with caution in patients infected with S. Typhi that have intermediate susceptibility to ciprofloxacin.
Typhoid fever, caused by Salmonella enterica serovar Typhi (S. Typhi) and Salmonella enterica serovar Paratyphi A (S. Paratyphi A), has been estimated to cause approximately 27 million infections each year worldwide . The disease is common in parts of Asia particularly among children . Fatality rates in the pre-antimicrobial era ranged from 7 – 26% of hospitalised cases [3–5]. The introduction of chloramphenicol, and subsequently, other antimicrobial agents, led to a marked reduction in the occurrence of severe and fatal disease [4, 5]. Despite improvements in treatment, some patients, particularly the very young and elderly, and those receiving inadequate antimicrobial therapy, continue to develop severe and life threatening disease [5–7].
Since the early1990s multidrug-resistant (MDR) strains of S. Typhi and S. Paratyphi A (resistant to chloramphenicol, trimethoprim/sulphamethoxazole and ampicillin) have not only caused epidemics, but have become endemic across some parts of Asia [2, 8]. Similarly, isolates of S. Typhi and S. Paratyphi A with intermediate susceptibility to ciprofloxacin (formerly called decreased susceptibility and indicated in the laboratory by resistance to nalidixic acid or with a minimum inhibitory concentration (MIC) between 0.1 and 0.5 μg/mL against ciprofloxacin) are now common in endemic areas and in imported infections in industrialised countries [8, 9]. Intermediate susceptibility to ciprofloxacin has been associated with longer fever clearance time and treatment failures when either ciprofloxacin or ofloxacin are used for treatment [10, 11].
Severe or fatal typhoid fever has been reported to be associated with extremes of age, female and male sex and prolonged illness [4, 6, 7, 12–16]. Infection with antimicrobial resistant isolates (MDR and nalidixic acid resistant) has also been proposed to correlate with the development of severe infection [6, 16, 17]. The association of antimicrobial resistance with severe disease may result from a delay in the initiation of appropriate antimicrobial therapy, but may also potentially be the result of a genotypic association that increases the pathogenic potential of infecting organism.
We aimed to determine microbiological and clinical factors associated with increased risk of severe typhoid fever, hypothesising that the changing antimicrobial resistance phenotypes throughout the selected study periods in Vietnam were associated with a shift in disease severity. We used a logistic regression model to assess the influence of age, sex, duration of illness prior to hospital admission, and the antimicrobial resistance profile of the infecting isolate on the clinical severity of typhoid.
This analysis was performed on data from patients at two hospitals in southern Vietnam between May 1993-July 1995 and April 1997-February 1999. The two hospitals were The Hospital for Tropical Diseases (HTD) in Ho Chi Minh City (HCMC) and Dong Thap Provincial Hospital (DTPH) in Cao Lanh, Dong Thap Province. HTD is a 500-bed infectious disease hospital with a catchment area encompassing HCMC and is a referral hospital for the surrounding province and DTPH is a 400-bed general hospital, serving the population of Cao Lanh and is a referral centre for the province of Dong Thap in the Mekong Delta. During these time periods consecutive patients with blood or bone marrow culture confirmed typhoid were included in antimicrobial treatment, diagnostic, pathophysiology and surveillance studies at the two hospitals [17–27]. There were only a small number of patients with paratyphoid and they were excluded from this analysis.
Each individual study independently received approval from the scientific and ethical committee of the respective hospital prior to the initiation of the study. Patients, or the parent or guardian for children, gave informed verbal consent before entry into the studies. The studies were conducted in accordance with the Declaration of Helsinki. This was a post-hoc analysis of the existing prospectively collected anonymised patient and laboratory data from these studies. No additional data collection or laboratory analysis was performed.
Demographic, clinical and laboratory data was prospectively gathered on standardised case report forms at the time of hospital admission. For continuous variables patients were categorised according to the presence within the first 24 hours of admission of; a peak temperature of > 40.0°C, a systolic blood pressure of < 90 mmHg, a haematocrit of < 30%, an elevated white cell count (defined as > 15 × 109/L), a low white cell count (defined as < 4 × 109/L), a low platelet count (defined as < 100 × 109/L), an elevated SGOT (defined as > 200 IU/L which was approximately five times upper limit of normal) and an elevated SGPT (defined as > 200 IU/L which was approximately five times upper limit of normal). Clinical outcomes (death or resolution) were recorded for all patients. Patients who were readmitted as relapse cases were only included for the initial admission. Information concerning antimicrobial agents used for treatment prior to hospital admission was not reliably available.
Severe disease was defined by the presence of one or more of the following features: gastrointestinal bleeding (the presence of visible blood in the stool), intestinal perforation (confirmed at surgery), encephalopathy (delirium, obtundation or coma), haemodynamic shock (systolic blood pressure < 90 mmHg and/or diastolic blood pressure < 60 mmHg associated with tissue hypoperfusion), myocarditis (tachycardia or bradycardia with an associated abnormality of the ECG or ultrasound evidence of a pericardial effusion), hepatitis (as indicated by jaundice and/or hepatomegaly with abnormal levels of SGOT (> 400 IU/L) and/or SGPT (>400 IU/L)), a clinical diagnosis of cholecystitis (right upper quadrant pain and tenderness without evidence of hepatitis), pneumonia (respiratory symptoms with abnormal chest X-ray infiltrates) or pleural effusion, severe anaemia (haematocrit ≤ 20%), the need for a blood transfusion, or death.
Blood or bone marrow aspirates was added to brain heart infusion broth containing sodium polyethanolsulphonate (1:10) and incubated at 35-37°C for seven days. Sub-cultures were performed after one, two and seven days or when the broth went turbid. Alternatively, blood was inoculated into BACTEC bottles (Becton-Dickenson, USA) and cultured for five days in a BACTEC 9050 automated incubator. Bottles that gave a positive signal were sub-cultured. Salmonella isolates were identified by standard biochemical tests and agglutination with Salmonella specific antisera (Murex diagnostics, Dartford, United Kingdom). Antimicrobial sensitivities were performed at the time of isolation by a modified Bauer-Kirby disc diffusion method and inhibition zone sizes were recorded. Interpretations of the zone sizes were based on the current (2013) CLSI guidelines . The antimicrobials tested (Unipath, Basingstoke, United Kingdom) were chloramphenicol (30μg), ampicillin (10μg), trimethoprim-sulphamethoxazole (1.25/23.75μg), ceftriaxone (30μg), ofloxacin (5μg), azithromycin (15μg) and nalidixic acid (30μg). Isolates were stored in Protect beads (Prolabs, Oxford, United Kingdom) at −20°C.
Stored bacterial isolates were later sub-cultured onto nutrient agar and the MICs for the isolates were determined by the standard agar plate dilution method according to CLSI guidelines or using E- test strips according to the manufacturer’s guidelines (AB Biodisk, Solna, Sweden). The evaluated antimicrobials were ciprofloxacin (0.008 μg/mL to 4 μg/mL), ofloxacin (0.008 μg/mL to 4 μg/mL) and nalidixic acid (0.5μg/mL to 512 μg/mL). Antimicrobial powders were purchased from Sigma, United Kingdom, except for ofloxacin, which was donated from Hoescht Marion Roussel. Escherichia coli ATCC® 25922 and Staphylococcus aureus ATCC® 25923 were used as control strains for these assays. An isolate was defined as MDR if it was resistant to chloramphenicol (≥ 32μg/ml), trimethoprim/sulphamethoxazole (≥ 8/152 μg/ml) and ampicillin (≥ 32μg/ml). An isolate was defined as having intermediate ciprofloxacin susceptibility if it was resistant to nalidixic acid (≥ 32μg/ml) and/or had a ciprofloxacin MIC of 0.1-0.5 μg/ml and/or ofloxacin MIC of 0.25-1.0 μg/ml.
Demographic and clinical features were described for the whole cohort and within the stratified age categories of < 5 years, 5–15 years and ≥ 16 years. Continuous data was described using median and inter-quartile range and compared using the Mann Whitney U-test. Proportions were compared with the Chi squared test or the Fisher’s exact test as appropriate. Age, sex, duration of illness prior to admission to hospital, the presence of an MDR phenotype and intermediate susceptibility to ciprofloxacin were evaluated for association with severe or fatal typhoid fever through a univariate analysis. A multivariate logistic regression model controlling simultaneously for the effects of confounding included variables associated with the outcome of severity (p < 0.10) as well as a priori factors age, sex and site. Statistical analysis was performed using STATA version 11 (StataCorp, Texas, USA).
Demographic data and diagnostic test results
The clinical and microbiological features of typhoid on hospital admission
The demographics and clinical features of 581 typhoid fever patients categorised by age
n = 581
n = 44
n = 311
n = 226
Ho Chi Minh City
Days ill prior to admission5
Signs & symptoms
6SBP <90 mmHg
8White cell count <4×109/L
8White cell count > 15×109/L
9Platelet count <100×109/L
10SGOT >200 IU/L
10SGPT >200 IU/L
Fully susceptible organism
Reduced susceptibility to FLQ
Clinical outcomes and the prevalence of severe typhoid
Outcome in the 581 patients with confirmed typhoid categorised by age group
n = 581
n = 44
n = 311
n = 226
Severe or fatal disease
Clinical and haematological characteristics of 90 severe and 491 non-severe typhoid fever patients
Severe or fatal n = 90
Non-severe n = 491
Signs & symptoms
Systolic blood pressure <90 mmHg
White cell count <4×109/L2
White cell count >15×109/L2
Platelet count <100×109L 3
SGOT > 200 IU/L4
SGPT > 200 IU/L4
Risk factors associated with severe typhoid infections
Factors associated with severe or fatal typhoid fever
Severe or fatal n = 90
Non severe n = 491
Days ill prior to admission1
Fully susceptible organism
Intermediate ciprofloxacin resistance
Ho Chi Minh City
We hypothesised that the observed association between infection with an organism exhibiting intermediate resistance to ciprofloxacin and disease severity may be related to these individuals having a longer duration of illness before hospital admission, as a result of initially receiving ineffective treatment. However, the median duration of illness prior to hospitalisation for patients infected with an organism with intermediate ciprofloxacin resistance was 8 (IQR: 6–10) days and for patients infected with a ciprofloxacin susceptible organism was also 8 (IQR: 6–13) days (p = 0.081).
In this study of 581 Vietnamese patients hospitalised with acute typhoid we identified an independent association of infection with isolates with intermediate susceptibility to ciprofloxacin with severe typhoid. Our research and the research of other groups have previously discussed an impaired response to ofloxacin and ciprofloxacin among patients infected with a ciprofloxacin intermediate isolate [10, 11]. A retrospective report in children and adults from New Dehli, India showed an association between severe disease and MDR strains and strains with a decreased susceptibility to fluoroquinolones . In the multivariate analysis in the New Dehli study this relationship with severe disease remained significant for strains exhibiting a decreased susceptibility to fluoroquinolones (OR 3.96, 95% CI 1.39-11.24, p = 0.004). During the period of the study fluoroquinolones, such as ofloxacin and ciprofloxacin, became widely available for treating typhoid infections caused by MDR organisms in outpatients, private clinics and hospitals. Such treatment would be less effective initial treatment for strains with intermediate susceptibility to ciprofloxacin. We anticipated that this might result in a delayed presentation to hospital for patients infected with such strains. In fact there was no significant difference in the duration of illness before admission in these patients compared with those infected with ciprofloxacin susceptible strains.
Our analyses found that severe or fatal disease was slightly more common in adults than children. Previous data regarding the severity of typhoid in children and adults demonstrates variability. Some studies describe typhoid as a severe disease in young children [6, 7, 13, 14], but others characterise it as a comparatively mild, even benign, illness [29–31]. This feature of our findings may lack some generalisability, as severely ill children resident in HCMC may be admitted to one of two specialist paediatric hospitals rather than HTD. Furthermore, typhoid in very young children (< 5 years) may present with unspecific clinical features such as syndromic sepsis, pneumonia, diarrhoea or a viral syndrome and may not be recognised as clinical typhoid . We also found that that severe disease was more common in males and all the cases of intestinal perforation were in males. Previous studies have suggested that disease severity between sexes can vary geographically and has been found to be more common in females [7, 15] but also with males, particularly intestinal perforation . It is noteworthy that anaemia was significantly more common among patients with severe disease. We speculate that the reasons for this are multi-factorial including intestinal bleeding, haemolysis and nutritional.
In this analysis severe disease occurred in 15.5% of all typhoid patients and fatal disease in 0.5%. These figures are comparable with studies conducted in Pakistan, Bangladesh, India and the United States [6–8, 16]. As only approximately 10% of patients with blood culture confirmed typhoid are hospitalised in this region, these figures likely do not reflect the true frequency of severe disease in the population . The threshold for hospital admission, the availability of antimicrobials in the community without prescription and their use prior to admission will vary between different localities and undoubtedly bias who is admitted to hospital. All the fatal cases from this analysis were adults with encephalopathy and haemodynamic shock; these symptoms have previously been identified as markers of particularly severe disease [33–35].
We found no association of disease severity with an MDR phenotype. In a prospective study of 1,158 children with culture confirmed typhoid fever in Karachi, Bhutta and co-workers found that MDR infections in children in Karachi were associated with higher rates of toxicity, hepatomegaly and hypotensive shock . The 2% mortality in children with an MDR infection in the study from Pakistan was not significantly higher than the 1.4% mortality in those infected with an antimicrobial susceptible strain (OR 1.6, 95% CI; 0.5 - 4.6, p = 0.34). Notably, intermediate susceptibility to fluoroquinolones was not documented in the study from Pakistan. In a previous investigation in Vietnam, which incorporated some data from the first period of this study, higher bacterial counts in the blood were associated with an MDR phenotype .
The reason for more severe disease in those infected with strains with intermediate susceptibility to ciprofloxacin may be more complex than merely a poor response to antimicrobial therapy. We speculate that the genotype of the relevant S. Typhi organisms may also play an important role in regulating disease severity. Specifically, we suggest an association between bacterial haplotype (assessed by chromosomal single nucleotide polymorphisms (SNPs)) and the pathogenic potential of the strain. There is currently no SNP/disease severity data to support this theory. However, S. Typhi isolates originating in Papua New Guinea in the late 1980s and early 1990s exhibited extensive genetic diversity using an insensitive genotyping method (Pulsed field gel electrophoresis (PFGE)), yet a single clone appeared to associated with 11 cases of fatal disease . A further study of 81 S. Typhi isolates from 1997–1999, also in Papua New Guinea, showed increased genetic divergence in S. Typhi with PFGE, but only a restricted range of PFGE types were found in seven patients with severe or fatal disease . Furthermore, recent studies have shown an association of the ciprofloxacin intermediate phenotype and the IncH1 MDR plasmid with H58 haplotype [38–40]. We have found that this particular haplotype has undergone widespread emergence in the Mekong Delta of Vietnam in the last 10 years . Whether this haplotype is associated with more severe disease requires further investigation.
Our investigation has limitations that need to be considered. Firstly, we only studied hospital admitted cases and our data are, therefore, biased by factors that determine hospital admission such as pre-hospital treatment and access to healthcare. The lack of reliable data concerning pre-hospital antimicrobial therapy is a further drawback. The data are recorded from a period more than ten years ago and, therefore, may not represent the contemporary situation in Vietnam or in other parts of Asia. However, we selected this period as it covered a period of changing antimicrobial susceptibility patterns and strains. In many locations, which are currently endemic for typhoid, antimicrobial resistant strains now dominate the local epidemiology, making it difficult to determine any potential link between resistance and disease severity .
In this large dataset on clinical typhoid and disease severity we found an independent association between infections with strains with intermediate susceptibility to ciprofloxacin and severe typhoid fever. This may reflect the widespread use of fluoroquinolones, particularly ciprofloxacin and ofloxacin, in this area during this period that are not fully effective against these infections. Whether additional host and bacterial factors are implicated in severe disease requires further investigation. Ciprofloxacin and ofloxacin should be used with caution in patients infected with S. Typhi that have intermediate susceptibility to ciprofloxacin. Although the newer generation fluorquinolone gatifloxacin is effective for treating such infections it is now unavailable in many countries because of safety concerns. Other alternatives for treating infections with isolates that are MDR and have intermediate susceptibility to ciprofloxacin are extended spectrum cephalosporins and azithromycin .
We thank the Directors, clinical and laboratory staff of the Hospital for Tropical Diseases and Dong Thap Provincial Hospital for their support of this study and the patients for their agreement to participate.
This work was supported by The Wellcome Trust of Great Britain. Stephen Baker is supported by a Sir Henry Dale Fellowship from the Royal Society and the Wellcome Trust. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
- Buckle GC, Fischer Walker CL, Black RE: Typhoid fever and paratyphoid fever: Systematic review to estimate global morbidity and mortality for 2010. J Global Health. 2012, 2: 010401-View ArticleGoogle Scholar
- Ochiai RL, Acosta CJ, Danovaro-Holliday MC, Baiqing D, Bhattacharya SK, Actinic MD, Bhutta ZA, Cahn DG, Ali M, Shin S, Wain J, Page AL, Albert MJ, Farrar J, Abu-Elated R, Pang T, Galindo CM, von Seidlein L, Clemens JD: DOMI study typhoid group. A study of typhoid fever in five Asian countries: disease burden and implications for control. Bull WHO. 2008, 86: 260-268.PubMedPubMed CentralGoogle Scholar
- Parry CM, Hien TT, Dougan G, White NJ, Farrar JJ: Typhoid fever. New Engl J Med. 2002, 347: 1770-1782. 10.1056/NEJMra020201.View ArticlePubMedGoogle Scholar
- Butler T, Knight J, Nath SK, Speelman P, Roy SK, Azad MAK: Typhoid fever complicated by intestinal perforation: a persisting fatal disease requiring surgical management. Rev Infect Dis. 1985, 7: 244-256. 10.1093/clinids/7.2.244.View ArticlePubMedGoogle Scholar
- Van den Bergh ETAM, Gasem MH, Keuter M, Dolmans MV: Outcome in three groups of patients with typhoid fever in Indonesia between 1948 and 1990. Trop Med Int Health. 1999, 4: 211-215. 10.1046/j.1365-3156.1999.43374.x.View ArticlePubMedGoogle Scholar
- Bhutta ZA: Impact of age and drug resistance on mortality in typhoid fever. Arch Dis Child. 1996, 75: 214-217. 10.1136/adc.75.3.214.View ArticlePubMedPubMed CentralGoogle Scholar
- Butler T, Islam A, Kabir I, Jones PK: Patterns of morbidity and mortality in typhoid fever dependent on age and gender: review of 552 hospitalised patients with diarrhoea. Rev Infect Dis. 1991, 13: 85-90. 10.1093/clinids/13.1.85.View ArticlePubMedGoogle Scholar
- Chau TT, Campbell JI, Galindo CM, Hoang NVM, Diep TS, Nga TTT, Vinh Chau NV, Tuan PQ, Page AL, Ochiai L, Schultsz C, Wain J, Bhutta ZA, Parry CM, Bhattacharya SK, Dutta S, Agtini M, Dong B, Honghui Y, Anh DD, Canh DG, Naheed A, Albert MJ, Phetsouvanh R, Newton PN, Basnyat B, Arjyal A, La TTP, Rang NN, Phuong LT, Bay PVB, von Seidlein L, Dougan G, Clemens JD, Vinh H, Hien TT, Chinh NT, Acosta CJ, Farrar J, Dolecek C: Antimicrobial drug resistance of Salmonella enteric serovar Typhi in Asia and molecular mechanism of reduced susceptibility to the fluoroquinolones. Antimicrob Agents Chemother. 2007, 51: 4315-4323. 10.1128/AAC.00294-07.View ArticlePubMedPubMed CentralGoogle Scholar
- Lynch MF, Blanton EM, Bulens S, Polyak C, Vojdani J, Stevenson J, Medalla F, Barzilay E, Joyce K, Barrett T, Mintz ED: Typhoid fever in the United States, 1999–2006. JAMA. 2009, 302: 859-865. 10.1001/jama.2009.1229.View ArticlePubMedGoogle Scholar
- Crump JA, Kretsinger K, Gay K, Hoekstra RM, Vugia DJ, Hurd S, Segler SD, Megginson M, Luedeman LJ, Shiferaw B, Hanna SS, Joyce KW, Mintz ED, Angulo FJ: Emerging Infection Program FoodNet, NARMS Working Group: Clinical response and outcome of infection with Salmonella enterica serotype Typhi with decreased susceptibility to fluoroquinolones: a United States FoodNet multicentre retrospective cohort study. Antimicrob Agents Chemother. 2008, 52: 1278-1284. 10.1128/AAC.01509-07.View ArticlePubMedPubMed CentralGoogle Scholar
- Parry CM, Vinh H, Chinh NT, Wain J, Campbell JI, Hien TT, Farrar JJ, Baker S: The influence of reduced susceptibility to fluoroquinolones in Salmonella enterica serovar Typhi on the clinical response to ofloxacin therapy. PLoS Negl Trop Dis. 2011, 5: e1163-10.1371/journal.pntd.0001163.View ArticlePubMedPubMed CentralGoogle Scholar
- Stuart BM, Pullen RL: Typhoid. Clinical analysis of three hundred and sixty cases. Arch Intern Med. 1946, 78: 629-661. 10.1001/archinte.1946.00220060002001.View ArticleGoogle Scholar
- Scragg J, Rubidge C, Wallace HL: Typhoid fever in African and Indian children in Durban. Arch Dis Child. 1969, 44: 18-28. 10.1136/adc.44.233.18.View ArticlePubMedPubMed CentralGoogle Scholar
- Duggan MB, Beyer L: Enteric fever in young Yoruba children. Arch Dis Child. 1975, 1975 (50): 67-71.View ArticleGoogle Scholar
- Khan M, Coovadia YM, Connolly C, Sturm AW: Influence of sex on clinical features laboratory findings and complications of typhoid fever. Am J Trop Med Hyg. 1999, 61: 41-46.PubMedGoogle Scholar
- Walia M, Gaind R, Mehta R, Paul P, Aggarwal P, Kalaivani M: Current perspectives of enteric fever: a hospital based study from India. Ann Trop Paed. 2005, 25: 161-174. 10.1179/146532805X58085.View ArticleGoogle Scholar
- Wain J, Diep TS, Ho VA, Walsh AM, Hoa NTT, Parry CM, White NJ: Quantitation of bacteria in blood of typhoid fever patients and relationship between counts and clinical features, transmissibility and antimicrobial resistance. J Clin Microbiol. 1998, 36: 1683-1687.PubMedPubMed CentralGoogle Scholar
- Hoa NTT, Diep TS, Wain J, Parry CM, Hien TT, Smith MD, Walsh AL, White NJ: Community acquired septicaemia in southern Vietnam: the importance of multidrug resistant Salmonella typhi. Trans Roy Soc Trop Med Hyg. 1998, 92: 503-508. 10.1016/S0035-9203(98)90891-4.View ArticlePubMedGoogle Scholar
- Smith MD, Duong NM, Hoa NTT, Wain J, Ha HD, Diep TS, Day NPJ, Hien TT, White NJ: Comparison of ofloxacin and ceftriaxone for short-course treatment of enteric fever. Antimicrob Agents Chemother. 1994, 38: 1716-1720. 10.1128/AAC.38.8.1716.View ArticlePubMedPubMed CentralGoogle Scholar
- Vinh H, Wain J, Hanh VTN, Nga CN, Chinh MT, Bethell D, Hoa NTT, Diep TS, Dung NM, White NJ: Two or three days of ofloxacin treatment for uncomplicated multidrug-resistant typhoid fever in children. Antimicrob Agents Chemother. 1996, 40: 958-961.PubMedPubMed CentralGoogle Scholar
- Chinh NT, Solomon T, Thong MX, Ly LT, Hoa NTT, Wain J, Diep TS, Smith MD, Day NPJ, Phi LT, Parry CM, White NJ: Short courses of ofloxacin for the treatment of enteric fever. Trans R Soc Trop Med Hyg. 1997, 91: 347-349. 10.1016/S0035-9203(97)90102-4.View ArticleGoogle Scholar
- Chinh NT, Parry CM, Ly NT, Ha HD, Thong MX, Diep TS, Wain J, White NJ, Farrar JJ: A randomised controlled comparison of azithromycin and ofloxacin for treatment of multidrug-resistant or nalidixic acid resistant enteric fever. Antimicrob Agents Chemother. 2000, 44: 1855-1859. 10.1128/AAC.44.7.1855-1859.2000.View ArticlePubMedPubMed CentralGoogle Scholar
- Wain J, Bay PVB, Vinh H, Duong NM, Diep TS, Walsh AL, Parry CM, Hasserjian RP, Ho VA, Hien TT, Farrar J, White NJ, Day NPJ: Quantitation of bacteria in bone marrow from patients with typhoid fever: relationship between counts and clinical features. J Clin Microbiol. 2001, 39: 1571-1576. 10.1128/JCM.39.4.1571-1576.2001.View ArticlePubMedPubMed CentralGoogle Scholar
- Vinh H, Parry CM, Hanh VTN, Chinh MT, House D, Tham CT, Thao NTT, Diep TS, Wain J, Day NPJ, White NJ, Farrar JJ: Double blind comparison of ibuprofen and paracetamol for adjunctive treatment of uncomplicated typhoid fever. Pediatr Infect Dis J. 2004, 23: 226-230. 10.1097/01.inf.0000114905.87426.c2.View ArticlePubMedGoogle Scholar
- Chanh NQ, Everest P, Khoa TT, House D, Murch S, Parry CM, Connerton P, Bay PV, Diep TS, Mastroeni P, White NJ, Hien TT, Ho VA, Dougan G, Farrar JJ, Wain J: A clinical, microbiological, and pathological study of intestinal perforation associated with typhoid fever. Clin Infect Dis. 2004, 39: 61-67. 10.1086/421555.View ArticleGoogle Scholar
- Vinh H, Duong NM, Phuong LT, Truong NT, Bay PVB, Wain J, Diep TS, Ho VA, White NJ, Day NPJ, Parry CM: Comparative trial of short course ofloxacin for uncomplicated typhoid fever in Vietnamese children. Ann Trop Paed. 2005, 25: 17-22. 10.1179/146532805X23308.View ArticleGoogle Scholar
- Parry CM, Ho VA, Phuong LT, Bay PVB, Lanh MN, Tung LT, Tham NTH, Wain J, Hien TT, Farrar JJ: Randomised controlled comparison of ofloxacin, azithromycin and an ofloxacin-azithromycin combination for treatment of multidrug-resistant and nalidixic acid resistant typhoid fever. Antimicrob Agents Chemother. 2007, 51: 819-825. 10.1128/AAC.00447-06.View ArticlePubMedGoogle Scholar
- Clinical and Laboratory Standards Institute: Performance Standards for Antimicrobial Susceptibility Testing: 23rd Informational Supplement. CLSI document M100–S23: 33(1), Clinical and Laboratory Standards Institute. 2013, PA: WayneGoogle Scholar
- Ferreccio C, Levine MM, Manterola A, Rodriguez G, Rivara I, Prenzel I, Black RE, Mancuso T, Bulas D: Benign bacteraemia caused by Salmonella typhi and paratyphi in children younger than 2 years. J Pediatr. 1984, 104: 899-901. 10.1016/S0022-3476(84)80492-8.View ArticlePubMedGoogle Scholar
- Topley JM: Mild typhoid fever in children. Arch Dis Child. 1986, 61: 164-167. 10.1136/adc.61.2.164.View ArticlePubMedPubMed CentralGoogle Scholar
- Mahle WT, Levine MM: Salmonella typhi infection in children younger than five years of age. Pediatr Infect Dis J. 1993, 12: 627-631. 10.1097/00006454-199308000-00001.View ArticlePubMedGoogle Scholar
- Kasper MR, Sokhal B, Blair PJ, Wierzba TF, Putnam SD: Emergence of multidrug- resistant Salmonella enterica serovar Typhi with reduced susceptibility to fluoroquinolones in Cambodia. Diag Micro Infect Dis. 2010, 66: 207-209. 10.1016/j.diagmicrobio.2009.09.002.View ArticleGoogle Scholar
- Hoffman SL, Punjabi NH, Kumala S, Moechtar A, Pulungsih SP, Rivai RL, Rockhill RC, Woodward TE, Loedin AA: Reduction of mortality in chloramphenicol-treated severe typhoid fever by high dose dexamethasone. N Engl J Med. 1984, 310: 82-88. 10.1056/NEJM198401123100203.View ArticlePubMedGoogle Scholar
- Rogerson SJ, Spooner VJ, Smith TA, Richens J: Hydrocortisone in chloramphenicol treated severe typhoid fever in Papua New Guinea. Trans R Soc Trop Med Hyg. 1991, 85: 113-116. 10.1016/0035-9203(91)90180-7.View ArticlePubMedGoogle Scholar
- Punjabi NH, Hoffman SL, Edman DC, Sukri N, Laughlin LW, Pulungsih SP, Rivai AR, Sutoto Moechtar A, Woodward TE: Treatment of severe typhoid fever in children with high dose dexamethasone. Ped Infect Dis J. 1988, 7: 598-600. 10.1097/00006454-198808000-00002.View ArticleGoogle Scholar
- Thong KL, Passey M, Clegg A, Combs BG, Yassin RM, Pang T: Molecular analysis of isolates of Salmonella typhi obtained from patients with fatal and non-fatal typhoid fever. J Clin Microbiol. 1996, 34: 1029-1033.PubMedPubMed CentralGoogle Scholar
- Thong KL, Goh YL, Yasin RM, Lau MG, Passey M, Winston G, Yoannes M, Pang T, Reeder JC: Increasing genetic diversity of Salmonella enterica serovar Typhi isolates from Papua New Guinea over the period from 1992 to 1999. J Clin Microbiol. 2002, 40: 4156-4160. 10.1128/JCM.40.11.4156-4160.2002.View ArticlePubMedPubMed CentralGoogle Scholar
- Phan MD, Kidgell C, Nair S, Holt KE, Turner AK, et al: Variation in Salmonella enterica serovar Typhi IncH1 plasmids during the global spread of resistant typhoid fever. Antimicrob Agents Chemother. 2009, 53: 716-727. 10.1128/AAC.00645-08.View ArticlePubMedGoogle Scholar
- Holt KE, Phan MD, Baker S, Duy PT, Nga TVT, Hinds J, Putcher P, Cooke FJ, Thomson NR, Titball R, Bhutta ZA, Hasan R, Dougan G, Wain J: Emergence of a globally dominant IncHI1 plasmid type associated with multiple drug resistant typhoid. PLoS Negl Trop Dis. 2011, 5: e1245-10.1371/journal.pntd.0001245.View ArticlePubMedPubMed CentralGoogle Scholar
- Romagnac P, Weill FX, Dolecek C, Baker S, Brisse S, Chinh NT, Le TAH, Acosta CJ, Farrar J, Dougan G, Achtman M: Evolutionary history of Salmonella Typhi. Science. 2006, 314: 1301-1304. 10.1126/science.1134933.View ArticleGoogle Scholar
- Holt KE, Dolecek C, Chau TT, Duy PT, La TTP, Hoang NVM, Nga NVT, Campbell JI, Manh BH, Vinh Chau NV, Hien T, Farrar J, Dougan G, Baker S: Temporal fluctuation of multidrug resistant Salmonella Typhi haplotypes in the Mekong River Delta region of Vietnam. PLoS Neglect Trop Dis. 2011, 5: e929-10.1371/journal.pntd.0000929.View ArticleGoogle Scholar
- Butler T: Treatment of typhoid fever in the 21st Century: promises and shortcomings. Clin Microbiol and Infect. 2011, 17: 959-963. 10.1111/j.1469-0691.2011.03552.x.View ArticleGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2334/14/73/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.