Molecular epidemiology of invasive Salmonella typhi in southeast Turkey

Molecular typing and resistance analysis of travel-associated Salmonella enterica serotype Typhi

Salmonella enterica serotype Typhi is a human pathogen causing 12 to 30% mortality and requiring antibiotic therapy to control the severity of the infection. Typhoid fever in United States is often associated with foreign travel to areas of endemicity. Increasing resistance to multiple drugs, including quinolones, is associated with decreased susceptibility to ciprofloxacin (DCS). We investigated 31 clinical strains isolated in Florida from 2007 to 2010, associated with travel to six countries, to examine the clonal distribution of the organism and apparent nalidixic acid (NAL) resistance. The strains were isolated from blood or stool of patients aged 2 to 68 years. The isolates were subtyped by ribotyping and pulsed-field gel electrophoresis. Susceptibilities to 15 antimicrobials were determined, and the isolates were screened for integrons and gyrase A gene mutations. Both typing techniques effectively segregated the strains. Identical clones were associated with different countries, while diverse types coexisted in the same geographic location. Fifty-one percent of the strains were resistant to at least one antimicrobial, and five were resistant to three or more drugs (multidrug resistant [MDR]). All 12 isolates from the Indian subcontinent were resistant to at least one drug, and 83% of those were resistant to NAL. Three of the MDR strains harbored a 750-bp integron containing the dfr7 gene. Ninety-three percent of the resistant strains showed a DCS profile. All the NAL-resistant strains contained point mutations in the quinolone resistance-determining region of gyrA. This study affirms the global clonal distribution, concomitant genetic heterogeneity, and increased NAL resistance of S. enterica serovar Typhi.

Epidemiological characteristics and molecular typing of Salmonella enterica serovar Typhi during a waterborne outbreak in Eastern Anatolia

In this study, we aimed to study the molecular and epidemiological characteristics of Salmonella enterica serovar Typhi (S. Typhi) outbreak in Eastern Anatolia. Six hundred and thirty-seven patients from the same county with clinical diagnosis of typhoid fever were investigated with conventional methods from stool, urine and blood specimens. Antibiotic susceptibility tests and identifications were performed for positive specimens. Clonal relationships between the isolates were investigated using pulsed field gel electrophoresis (PFGE) method. A questionnaire was completed for the water consumption habits of patients. Of 91 culture positive specimens, 76 were blood, 13 were stool and 2 were urine. The isolates were resistant to ampicillin, ampicillin/sulbactam, chloramphenicol, cefuroxime, amikacin, gentamicin and trimethoprim-sulfamethoxazole. Although there was a single band difference in some isolates, PFGE results indicated that this was an outbreak caused by single strain according to the Tenover criteria. This outbreak thought to be associated with the consumption of tap water contaminated with sewage represents a breakdown of the basic public health and civil engineering infrastructure. Appropriate public health measures should be taken in order to avoid such outbreaks in the future.

Clustering analysis of Salmonella enterica serovar Typhi isolates in Korea by PFGE, ribotying, and phage typing

Salmonella enterica serovar Typhi is a Gram-negative bacterium causing the acute febrile disease typhoid fever. In Korea from 2004 to 2006, a total of 51 Salmonella Typhi isolates were identified in stool and blood from healthy carriers and patients with or without overseas travel histories. In this study, antibiogram, pulsed-field gel electrophoresis (PFGE), and automated ribotyping were performed as molecular epidemiological methods with phage typing as a classical subtyping tool of the isolates. Only two isolates were multidrug resistant and 82.3% of the isolates were susceptible to 16 antimicrobial agents tested. When the dendrogram was created based on the PFGE results, the subtypes could be clustered into five groups by 80% similarity criterion. The PFGE patterns of 31 isolates (60.8%) belonged to Cluster 3, the predominant cluster in the study. Three overseas travel-associated cases were differentiated into Cluster 4 of which three isolates were nalidixic acid or multidrug resistant. Major phage type and ribotype were A and PvuII-436-8-S-6, respectively. This study also showed the prevalence of PFGE Cluster 3 in Korea by clustering analysis and the link between some typhoid cases and travel to Cambodia, India, or Indonesia.

A simple validated prediction rule to diagnose typhoid fever in Turkey

The goal of this study was to develop a simple prediction rule for the diagnosis of typhoid fever. A model for the prediction of patients with typhoid fever at hospital admission was derived and validated by assigning weighted point values to independent predictive factors associated with a diagnosis of typhoid fever at hospital admission. Patient demographic, clinical and laboratory variables were used to compare patients with blood culture-confirmed typhoid fever with patients with fever of unknown origin. The model was derived and validated in two separate cohorts of patients from Dicle University Hospital in Diyarbakir, Turkey. A total of 371 patients were enrolled. A diagnostic index score was created using seven independent predictive factors associated with typhoid fever at hospital admission: age <30 years, abdominal distention, confusion, leukopenia, relative bradycardia, positive Widal test and a typhoid tongue. A clinical prediction rule helped to differentiate patients with typhoid fever.

Risk factors for typhoid fever among adult patients in Diyarbakir, Turkey

We conducted a case-control study to assess risk factors for typhoid fever in Diyarbakir, Turkey, a region where transmission of Salmonella typhi is endemic. We prospectively identified febrile patients from Diyarbakir and the surrounding area who were admitted to hospital. Cases were defined as patients who had S. typhi isolated from at least one blood culture. Sixty-four cases with blood culture-confirmed S. typhi were identified between May 2001 and May 2003. In total, 128 age- and sex-matched controls selected from neighbourhoods as cases were enrolled. We hypothesized that consumption of raw vegetables contaminated with sewage would be associated with an increased risk of typhoid fever. Conditional logistic regression modelling revealed that living in a crowded household (OR 3.31, 95% CI 1.58-6.92, P=0.002), eating cig kofte (a traditional raw food) (OR 5.29, 95% CI 2.20-12.69, P=0.000) and lettuce salad (OR 3.55, 95% CI 1.52-8.28, P=0.003) in the 15 days prior to symptoms onset was independently associated with typhoid fever. We conclude that living in a crowded household and consumption of raw vegetables outside the home increase the risk of typhoid fever in this region.