Enterica Serovar Typhi Isolates Research Articles

Tenacious Endemic Typhoid Fever in Samoa.

BackgroundTyphoid fever has been endemic on the island nation of Samoa (2016 population, 195 979) since the 1960s and has persisted through 2019, despite economic development and improvements in water supply and sanitation.Methods Salmonella enterica serovar Typhi isolates from the 2 hospitals with blood culture capability and matched patient demographic and clinical data from January 2008 through December 2019 were analyzed. Denominators to calculate incidence by island, region, and district came from 2011 and 2016 censuses and from 2017–2019 projections from Samoa’s Bureau of Statistics. Data were analyzed to describe typhoid case burden and incidence from 2008 to 2019 by time, place, and person.ResultsIn sum, 53–193 blood culture-confirmed typhoid cases occurred annually from 2008 to 2019, without apparent seasonality. Typhoid incidence was low among children age < 48 months (17.6–27.8/105), rose progressively in ages 5–9 years (54.0/105), 10–19 years (60.7–63.4/105), and 20–34 years (61.0–79.3/105), and then tapered off; 93.6% of cases occurred among Samoans < 50 years of age. Most typhoid cases and the highest incidence occurred in Northwest Upolu, but Apia Urban Area (served by treated water supplies) also exhibited moderate incidence. The proportion of cases from short-cycle versus long-cycle transmission is unknown. Samoan S. Typhi are pansusceptible to traditional first-line antibiotics. Nevertheless, enhanced surveillance in 2019 detected 4 (2.9%) deaths among 140 cases.ConclusionsTyphoid has been endemic in Samoa in the period 2008–2019. Interventions, including mass vaccination with a Vi-conjugate vaccine coadministered with measles vaccine are planned.

Clinical characteristics in adult patients with Salmonella bacteremia and analysis of ciprofloxacin-nonsusceptible isolates.

The purpose of this study is to describe clinical characteristics of Salmonella bacteremia in adult patients and analyze ciprofloxacin-nonsusceptible isolates. A total of 101 Salmonella blood isolates from adult patients were collected from January 2011 to December 2013 in MacKay Memorial Hospital. Eight ciprofloxacin-nonsusceptible Salmonella blood isolates were screened for carbapenemase and other β lactamase genes. Isolates were examined by PCR for the quinolone resistance-determining region (QRDR) of all subunits for DNA gyrase (gyrA and gyrB) genes and topoisomerase IV (parC and parE) genes. There were 22 (21.78%) S. enterica serovar B, 5 (4.95%) S. enterica serovar C1, 7 (6.93%) S. enterica serovar C2, 65 (64.36%) S. enterica serovar D, and 2 (1.98%) S. enterica serovar Typhi (S. typhi) isolates. β-lactamase gene screening and sequencing yielded only one blaCMY-2-positive isolate. In multivariate risk factor analysis, renal insufficiency [odds ratio (OR) 3.774; p=0.020] and heart disease (OR 2.922; p=0.027) were more common among elderly patients (≥65 years). Independent risk factors for ciprofloxacin-nonsusceptible strains included S. enterica serovar C2 (OR 28.430; p=0.032), renal insufficiency (OR 13.927; p=0.032), and immunosuppression agent usage (OR 60.082; p=0.006). 87.50% (7/8) of isolates had gyrA mutation, 62.50% (5/8) had parC mutation, and none had gyrB and parE mutations. Isolates with both Ser83Phe/Asp87Asn gyrA and Thr57Ser/Ser80Ile parC mutation genes were highly ciprofloxacin-resistant (minimum inhibitory concentration ≥4mg/L). Elderly patients with renal insufficiency and heart disease were at risk for Salmonella bacteremia. Those for ciprofloxacin-nonsusceptible strains included S. enterica serovar C2, renal insufficiency, and immunosuppression agent usage. The 8 ciprofloxacin-nonsusceptible isolates carried gyrA and parC mutations, which cause resistance that poses a major concern.

Chromosome-mediated multidrug resistance in Salmonella enterica serovar Typhi.

A salmonella genomic island, designated SGI11, was found in 18 of 26 multidrug-resistant Salmonella enterica serovar Typhi isolates from Bangladesh. SGI11 was an IS1 composite transposon and carried 7 resistance genes that conferred resistance to 5 first-line antimicrobials. Eleven of the 18 SGI11-carrying S. Typhi isolates had developed resistance to high levels of ciprofloxacin.

Antibiotic Resistance ofSalmonella entericaSerovar Typhi in Kolkata, India, andIn VitroExperiments on Effect of Combined Chemotherapy

This communication states the changing patterns of Salmonella enterica serovar Typhi (S. Typhi) isolates causing enteric fever in and around Kolkata, India. Among the isolates resistance to ampicillin (A), chloramphenicol (C), cotrimoxazole (Co) and tetracycline (T) were plasmid mediated; the plasmid was unstable in S. Typhi, and the other enteric bacteria like Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris were found to be the potential source of dissemination of such plasmids into S. Typhi. The infection with such S. Typhi strains were successfully treated with ciprofloxacin (Cp: MICs 0.0075–0.075 μg mL−1) and/or ofloxacin (Ofx: MICs 0.0125–0.075 μg mL−1), but in the later course, the S. Typhi strains, showing resistance to nalidixic acid, developed low level of resistance to Cp and Ofx, causing the treatment failure. Thus, the treatment regimen was shifted to the third generation cephalosporins like ceftriaxone (Ct) and cefotaxime (Cf). Keeping in mind the anticipation of development of resistance to Ct/Cf, we prepared the treatment regimen for MDR enteric fever, based on the double-drug synergy tests in vitro; Cp-gentamycin (FICI 0.121–0.216) and Cp-trimethoprim (FICI 0.14–0.483) combinations were found effective against S. Typhi isolates having decreased sensitivity to cp (MICs: 0.5–1.25 μg mL−1).

Bacteremia and Antimicrobial Drug Resistance over Time, Ghana

Bacterial distribution and antimicrobial drug resistance were monitored in patients with bacterial bloodstream infections in rural hospitals in Ghana. In 2001–2002 and in 2009, Salmonella enterica serovar Typhi was the most prevalent pathogen. Although most S. enterica serovar Typhi isolates were chloramphenicol resistant, all isolates tested were susceptible to ciprofloxacin.

Bacteremia and Antimicrobial Drug Resistance over Time, Ghana

Abstract Bacterial distribution and antimicrobial drug resistance were monitored in patients with bacterial bloodstream infections in rural hospitals in Ghana. In 2001–2002 and in 2009, Salmonella enterica serovar Typhi was the most prevalent pathogen. Although most S. enterica serovar Typhi isolates were chloramphenicol resistant, all isolates tested were susceptible to ciprofloxacin.

Single Nucleotide Polymorphism Typing of Global Salmonella enterica Serovar Typhi Isolates by Use of a Hairpin Primer Real-Time PCR Assay

Salmonella enterica serovar Typhi is highly homogeneous. Single nucleotide polymorphisms (SNPs) have been shown to be valuable markers for molecular typing of S. enterica serovar Typhi. Here, we used a hairpin primer real-time PCR assay for SNP typing of S. enterica serovar Typhi isolates. Forty-two SNPs were selected from a comparison of 19 published S. enterica serovar Typhi genomes and sequences from other studies. The SNPs were used to type 71 global S. enterica serovar Typhi isolates and differentiated these S. enterica serovar Typhi isolates and the 19 genome sequenced strains into 25 SNP profiles. Phylogenetic analysis revealed that these SNP profiles were grouped into six major clusters. These clusters can be identified by using five SNPs, while the full differentiation of the 25 SNP profiles requires a minimum of 24 SNPs. This real-time PCR-based SNP typing method will be useful for global epidemiological analysis.

Pattern of multi-drug resistant Salmonella enterica serovar typhi isolates in Nigeria

Typhoid fever continues to remain a health problem as the causative organism, Salmonella enterica serovar typhi, has developed resistance to many antibiotics used. This study was undertaken to determine the current pattern of resistance to antimicrobial agents by S. enterica serovar typhi isolates from Akaraugo Hospital in Owerri, Imo state. Sensitivity to most common antimicrobial agents used in the management of typhoid fever was determined by disc diffusion according to National Committee for Clinical Laboratory (NCCL) standards. There was an increase in the number of isolates with decreased sensitivity to nalixidic acid and cotrimoxazole. All isolates had complete resistance to augmentin, tetracycline and amoxicillin commonly used for treatment of typhoid fever. Therefore physicians should be advised to conduct effective susceptibility test before prescribing an antibiotics to a patient. It is also important to step up awareness to individuals about indiscriminate use of antibiotics and the need to complete a regime once it is started.

Randomized Controlled Comparison of Ofloxacin, Azithromycin, and an Ofloxacin-Azithromycin Combination for Treatment of Multidrug-Resistant and Nalidixic Acid-Resistant Typhoid Fever

Isolates of Salmonella enterica serovar Typhi that are multidrug resistant (MDR, resistant to chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole) and have reduced susceptibility to fluoroquinolones (nalidixic acid resistant, Na(r)) are common in Asia. The optimum treatment for infections caused by such isolates is not established. This study compared different antimicrobial regimens for the treatment of MDR/Na(r) typhoid fever. Vietnamese children and adults with uncomplicated typhoid fever were entered into an open randomized controlled trial. Ofloxacin (20 mg/kg of body weight/day for 7 days), azithromycin (10 mg/kg/day for 7 days), and ofloxacin (15 mg/kg/day for 7 days) combined with azithromycin (10 mg/kg/day for the first 3 days) were compared. Of the 241 enrolled patients, 187 were eligible for analysis (186 S. enterica serovar Typhi, 1 Salmonella enterica serovar Paratyphi A). Eighty-seven percent (163/187) of the patients were children; of the S. enterica serovar Typhi isolates, 88% (165/187) were MDR and 93% (173/187) were Na(r). The clinical cure rate was 64% (40/63) with ofloxacin, 76% (47/62) with ofloxacin-azithromycin, and 82% (51/62) with azithromycin (P = 0.053). The mean (95% confidence interval [CI]) fever clearance time for patients treated with azithromycin (5.8 days [5.1 to 6.5 days]) was shorter than that for patients treated with ofloxacin-azithromycin (7.1 days [6.2 to 8.1 days]) and ofloxacin (8.2 days [7.2 to 9.2 days]) (P < 0.001). Positive fecal carriage immediately posttreatment was detected in 19.4% (12/62) of patients treated with ofloxacin, 6.5% (4/62) of those treated with the combination, and 1.6% (1/62) of those treated with azithromycin (P = 0.006). Both antibiotics were well tolerated. Uncomplicated typhoid fever due to isolates of MDR S. enterica serovar Typhi with reduced susceptibility to fluoroquinolones (Na(r)) can be successfully treated with a 7-day course of azithromycin.

부산지역에서 분리된 Salmonella enterica serovar Typhi균에 대한 PFGE를 이용한 Molecular typing

1996년부터 2005년까지 부산지역에서 분리된 Salmonella enterica serovar Typhi 균주에 대한 항균제 내성 변화양상 및 Pulsed-field gel electrophoresis(PFGE)를 이용한 분리주의 분자역학적 형별을 분석하였다. 전체 424주에 대한 항균제 감수성 시험결과 multidrug-resistant (MDR) 6주(1.4%)와 nalidixic acid에만 내성을 보이는 2주를 제외한 나머지 416주(98.1%)가 시험 항균제 18종 모두에 감수성을 보였다. 부산지역 분리 장티푸스균의 유전적 이질성을 확인하고자 실시한 산발 분리 50주의 PFGE/XbaI 시험결과, 최소 32종의 다양한 패턴이 나타났다. 각 패턴별로 제한효소 절편 수는 13개에서 18개까지였고, 절편크기는 약 20 kb에서 630 kb 범위였다. 본 시험결과 부산지역의 장티푸스의 산발 또는 집단 발생시 PFGE는 유용한 역학적 지표로 사용가능함을 알 수 있었으며 또한 전국적 PulseNet 구축의 기초 자료로서 활용도가 높을 것으로 사료된다. We obtained 424 Salmonella enterica serovar Typhi isolates from sporadic cases of infection in Busan during 1996 to 2005. We investigated the trend of antimicrobial resistance and molecular typing by pulsed-field gel electrophoresis (PFGE). Of the total 424 isolates, 6 strains (1.4%) were multidrug-resistant (MDR) S. enterica serovar Typhi isolates, 2 strains (0.5%) were resistant to only nalidixic acid, and the remaining 416 strains (98.1%) were fully susceptible to the 18 antimicrobial agent. PFGE of XbaI-digested chromosomal DNA was performed on 50 sporadic S. enterica serovar Typhi isolates with the objective of investigating the extent of genetic diversity of these isolates in our region. We could find that these isolates were much more heterogeneous and at least 32 different PFGE patterns were generated according by dice coefficient, between 0.69 and 1.0. Restriction fragment patterns consisted of 13 to 18 fragments ranged in size from 20 to 630 kb. The results confirmed that PFGE would be an useful tool for investigating surveillance of sporadic or outbreak case and assessing clonality for S. enterica serovar Typhi in Busan area. Our finding will be valuable in developing rational strategies to control this pathogen and setting the basis of an effective PulseNet system in Korea.

Synergism of Ciprofloxacin and Trimethoprim against Salmonella enterica Serovar typhi Isolates Showing Reduced Susceptibility to Ciprofloxacin

The activity of the combination of ciprofloxacin and trimethoprim against 16 Salmonella enterica serovar typhi isolates from blood cultures were tested by agar dilution checkerboard technique. When used in combination, minimum inhibitory concentrations (MICs) of ciprofloxacin and trimethoprim ranged from 0.5 to 1.25 and from 10 to 125 µg/ml, respectively, and fractional inhibitory concentrations (FICs) from 0.025 to 0.125 and from 2.5 to 10 µg/ml, respectively. The FIC index was 0.140–0.483, indicating a marked synergy between ciprofloxacin and trimethoprim against trimethoprim-resistant S. enterica serovar typhi isolates (100%) with high MICs for ciprofloxacin.

Molecular typing of Salmonella enterica serovar typhi isolates from various countries in Asia by a multiplex PCR assay on variable-number tandem repeats.

A multiplex PCR method incorporating primers flanking three variable-number tandem repeat (VNTR) loci (arbitrarily labeled TR1, TR2, and TR3) in the CT18 strain of Salmonella enterica serovar Typhi has been developed for molecular typing of S. enterica serovar Typhi clinical isolates from several Asian countries, including Singapore, Indonesia, India, Bangladesh, Malaysia, and Nepal. We have demonstrated that the multiplex PCR could be performed on crude cell lysates and that the VNTR banding profiles produced could be easily analyzed by visual inspection after conventional agarose gel electrophoresis. The assay was highly discriminative in identifying 49 distinct VNTR profiles among 59 individual isolates. A high level of VNTR profile heterogeneity was observed in isolates from within the same country and among countries. These VNTR profiles remained stable after the strains were passaged extensively under routine laboratory culture conditions. In contrast to the S. enterica serovar Typhi isolates, an absence of TR3 amplicons and a lack of length polymorphisms in TR1 and TR2 amplicons were observed for other S. enterica serovars, such as Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Enteritidis, and Salmonella enterica serovar Paratyphi A, B, and C. DNA sequencing of the amplified VNTR regions substantiated these results, suggesting the high stability of the multiplex PCR assay. The multiplex-PCR-based VNTR profiling developed in this study provides a simple, rapid, reproducible, and high-resolution molecular tool for the epidemiological analysis of S. enterica serovar Typhi strains.

Antibiotic Susceptibilities of Salmonella enterica Serovar Typhi and S. enterica Serovar Paratyphi A Isolated from Patients in Japan

The antibiotic susceptibilities of 62 strains of Salmonella enterica serovar Typhi and 37 strains of S. enterica serovar Paratyphi A were investigated with 18 antibiotics. Eighteen S. enterica serovar Typhi isolates and five S. enterica serovar Paratyphi A isolates were resistant to one or more antimicrobial agents, among which 10 S. enterica serovar Typhi isolates were nalidixic acid resistant and also showed decreased ciprofloxacin susceptibility.

Analysis of plasmid and chromosomal DNA of multidrug-resistant Salmonella enterica serovar typhi from Asia.

Molecular analysis of chromosomal DNA from 193 multidrug-resistant (MDR) Salmonella enterica serovar Typhi isolates from 1990 to 1995 from Pakistan, Kuwait, Malaysia, Bangladesh, and India produced a total of five major different pulsed-field gel electrophoresis (PFGE) patterns. Even within a particular country MDR S. enterica serovar Typhi DNA was found to be in different PFGE groups. Similar self-transferable 98-MDa plasmids belonging to either incompatibility group incHI1 or incHI1/FIIA were implicated in the MDR phenotype in S. enterica serovar Typhi isolates from all the locations except Quetta, Pakistan, where the majority were of incFIA. A total of five different PFGE genotypes with six different plasmids, based on incompatibility and restriction endonuclease analysis groups, were found among these MDR S. enterica serovar Typhi isolates.

Molecular typing of multiple-antibiotic-resistant Salmonella enterica serovar Typhi from Vietnam: application to acute and relapse cases of typhoid fever.

The rate of multiple-antibiotic resistance is increasing among Salmonella enterica serovar Typhi strains in Southeast Asia. Pulsed-field gel electrophoresis (PFGE) and other typing methods were used to analyze drug-resistant and -susceptible organisms isolated from patients with typhoid fever in several districts in southern Vietnam. Multiple PFGE and phage typing patterns were detected, although individual patients were infected with strains of a single type. The PFGE patterns were stable when the S. enterica serovar Typhi strains were passaged many times in vitro on laboratory medium. Paired S. enterica serovar Typhi isolates recovered from the blood and bone marrow of individual patients exhibited similar PFGE patterns. Typing of S. enterica serovar Typhi isolates from patients with relapses of typhoid indicated that the majority of relapses were caused by the same S. enterica serovar Typhi strain that was isolated during the initial infection. However, some individuals were infected with distinct and presumably newly acquired S. enterica serovar Typhi isolates.