Resistome is a cluster of microbial genes encoding proteins with necessary functions to resist the action of antibiotics. Resistome governs essential and separate biological functions to develop resistance against antibiotics. The widespread clinical and nonclinical uses of antibiotics over the years have combined to select antibiotic-resistant determinants and develop resistome in bacteria. At present, the emergence of drug resistance because of resistome is a significant problem faced by clinicians for the treatment of Salmonella infection. Antibiotic resistome is a dynamic and ever-expanding component in Salmonella. The foundation of resistome in Salmonella is laid long before; therefore, the antibiotic resistome of Salmonella is reviewed, discussed, and summarized. We have searched the literature using PubMed, MEDLINE, and Google Scholar with related key terms (resistome, Salmonella, antibiotics, drug resistance) and prepared this review. In this review, we summarize the status of resistance against antibiotics in S. typhi, highlight the seminal work in the resistome of S. typhi and the genes involved in the antibiotic resistance, and discuss the various methods to identify S. typhi resistome for the proactive identification of this infection and quick diagnosis of the disease.
Anti-Bacterial Agents/pharmacology* ; Drug Resistance ; Humans ; Microbial Sensitivity Tests ; Salmonella ; Salmonella typhi/genetics*

OBJECTIVETo study the role of RpoE and RpoS on the influence of the metabolism and growth of bacterial under hyperosmotic stress.

METHODSThe rpoS/rpoE double deletion mutant of Salmonella enterica serovar typhi (S. typhi) was prepared by homologous recombination through the suicide plasmid mediated. The recombination was visualized by PCR. Growth curves were drawn by using photometric value A600 as the ordinate and cultivation time as abscissa. The survival abilities of bacterial were compared under hyperosmotic stress. Statistical differences of early logarithmic growth stage (4 h) and laters logarithmic growth stage (12 h) were analyzed by one-way ANOVA. The expression difference of metabolism related genes of wild-type and mutant strains of S. Typhi incubated under hyperosmotic stress were investigated by Salmonella genomic DNA microarray. Real-time quantitative PCR (qRT-PCR) was performed to validate the results of microarray assay in some selected genes.

RESULTSThe rpoS/rpoE double deletion mutant of S. Typhi was successfully generated. The analysis of growth curve showed that the 4-hour and 12-hour A600 values were separately 0.503 ± 0.018 and 2.060 ± 0.112 in rpoS deletion mutant strains, 0.293 ± 0.053 and 1.933 ± 0.115 in rpoE deletion mutant strains, and 0.051 ± 0.007 and 0.963 ± 0.111 in rpoS/rpoE double deletion mutant strains; all of which were lower than the values of wild-type strains, who were 0.725 ± 0.097 and 2.496 ± 0.171, respectively. The difference were statistically significant (P < 0.05). The genomic DNA microarray revealed that 42 genes relevant with bacterial metabolism were influenced by RpoE and RpoS. Results of qRT-PCR showed that the expression values of rpsE, rbsK, nusG and etuB in rpoS deletion mutant strains were (1.86 ± 0.14)×10(6), (1.37 ± 0.11)×10(6), (2.72 ± 0.58)×10(6) and (8.27 ± 1.01)×10(6) copies/µg, respectively; while those in rpoE deletion mutant strains were (2.19 ± 0.17)×10(6), (1.51 ± 0.12)×10(6), (2.73 ± 0.57)×10(6) and (9.63 ± 1.42)×10(6) copies/µg, respectively. Compared with the values in wild-type strains, which were separately (1.94 ± 0.10)×10(6), (1.52 ± 0.11)×10(6), (2.39 ± 0.52)×10(6) and (10.83 ± 1.52)×10(6) copies/µg, the differences was not statistical significance (P > 0.05). However, compared with the values in rpoS/rpoE double mutant strains, which were separately (5.64 ± 0.59)×10(6), (4.17 ± 0.40)×10(6), (9.44 ± 1.22)×10(6) and (2.95 ± 0.88)×10(6) copies/µg, the difference was significant (P < 0.05).

CONCLUSIONRpoE and RpoS could influence the expression of lots of metabolism genes. Together, they regulated the metabolism and growth of S. Typhi under hyperosmotic stress.

Bacterial Proteins ; genetics ; Gene Deletion ; Osmosis ; Salmonella typhi ; genetics ; growth & development ; metabolism ; Sigma Factor ; genetics ; Stress, Physiological

OBJECTIVETo analyses the genetic diversity and relationship of Salmonella typhi strains isolated from different years and districts in Guizhou province.

METHODSRibotyping with 16s rDNA probe was used to describe the diversity of the 209 strains which were isolated in 26 counties of Guizhou province, from 1959 to 1999. The antibiotics resistance was also studied.

RESULTSTwenty-six ribotypes were found in all 209 strains, with two dominant types. The strains isolated from local typhoid epidemics belonged to the unique Ribotypes. The major ribotypes of the resistant strains were RT7 and RT1.

CONCLUSIONThe Salmonella typhi isolates from Guizhou diverged obviously. The abundant clones and multi-resistance of the strains might serve the major reasons of the high morbidity of typhoid in Guizhou.

Blotting, Southern ; China ; DNA, Bacterial ; genetics ; DNA, Ribosomal ; genetics ; Phylogeny ; RNA, Ribosomal, 16S ; genetics ; Ribotyping ; Salmonella typhi ; classification ; genetics ; isolation & purification

Objective: To understand the epidemiological and molecular characteristics of typhoid and paratyphoid in China from 2009 to 2013, and provide evidence for the prevention and control of typhoid and paratyphoid, the development and improvement of surveillance strategies. Methods: Epidemiological analysis was conducted on the incidence data of typhoid and paratyphoid, and related public health emergencies in China during 2009-2013. Pathogen isolation and culture, serologic test were conducted for the typhoid and paratyphoid cases from 13 national surveillance sites. The isolates were subjected to antimicrobial susceptibility testing. Pulsed-field gel electrophoresis (PFGE) was performed for the molecular typing of these isolates. Results: The average incidence of typhoid and paratyphoid in China during this period was 1.03/100 000. The reported case number and incidence decreased with year. The provinces reporting high case numbers were Yunnan, Guizhou, Guangxi, Hunan, Zhejiang, Guangdong and Xinjiang. The incidence of age group 0-4 years was highest. The proportion of farmers and children outside child care settings showed an increasing tendency over time. The annual incidence peak was during July-August. Twenty five outbreaks occurred during 2009-2013. The results of pathogen isolation and culture showed that the positive rate was 3.00% (940/31 322), among the positive isolates, the proportion of Salmonella paratyphi A accounted for higher proportion (68.19%, 641/940) compared with Salmonella typhi (31.60%, 297/940). The drug resistances of Salmonella typhi and Salmonella paratyphi varied, but their resistances to nalidixic acid were highest (50.22% and 85.33%) respectively. A certain amount of Salmonella typhi isolates showed the resistance to the 3rd generation cephalosporins. PFGE analysis showed divergent patterns of Salmonella typhi compared with limited patterns of Salmonella paratyphi A. Conclusion: The epidemic level of typhoid and paratyphoid in China was relatively low, but the outbreak occurred occasionally. It is necessary to enhance the laboratory-based surveillance, particularly the capability of etiological diagnosis, outbreak investigation, response and antibiotic resistance monitoring, and conduct risk factor investigation in provinces with high incidences in recent years.
Child ; Child, Preschool ; China/epidemiology* ; Disease Outbreaks ; Drug Resistance, Bacterial/genetics* ; Electrophoresis, Gel, Pulsed-Field ; Epidemics ; Farmers ; Humans ; Incidence ; Infant ; Molecular Typing ; Paratyphoid Fever/microbiology* ; Population Surveillance ; Salmonella paratyphi A/isolation & purification* ; Salmonella typhi/isolation & purification* ; Typhoid Fever/microbiology*

We report a relapsed case of a 25 year-old man with multi-drug resistant Salmonella serovar Typhi (MDRST) bacteremia who had recently returned from travel in India. Due to unresponsiveness to ciprofloxacin and ceftriaxone, we examined the strain's resistance to quinolones and extended-spectrum beta-lactamases (ESBLs). The strain had a single gyrA mutation at codon 83 (Ser83Phe), which explains its decreased susceptibility to fluoroquinolone and resistance to nalidixic acid. In the screening tests of ESBLs, TEM-1 was positive, which is beta-lactamase but not ESBL. The patient was finally successfully treated with meropenem and aztreonam. In the presence of clinical unresponsiveness despite favorable sensitivity tests, further laboratory evaluations are needed, which should include studies of genes related to antibiotic resistance and ESBLs. In addition, further prospective trials should be done about the possible inclusion of antibiotics not yet mentioned in the current guidelines. With MDRST on the rise worldwide, the most optimal and effective line of antibiotic defense needs to be devised.
Adult ; Anti-Bacterial Agents/*administration & dosage ; Aztreonam/*administration & dosage ; Bacteremia/drug therapy/microbiology ; Drug Resistance, Bacterial/genetics ; Drug Resistance, Multiple/genetics ; Drug Therapy, Combination ; Humans ; Male ; Salmonella typhi/*drug effects/genetics ; Thienamycins/*administration & dosage ; Typhoid Fever/*drug therapy