Evaluation of the Effects of Probiotics and Prebiotics on the Salmonella typhi Infections

Typhoid fever is one of the most commonly disseminated diseases and is considered to be linked to poor sanitation. It is responsible for 2-5% of all deaths, and its causative agent is Salmonella typhi. The current study aimed to investigate the antibacterial activity of prebiotics (inulin and starch) and probiotics against multidrug resistance of S. typhi bacterial isolates. Determination of the inhibitory effect of probiotics and prebiotics against S. typhi isolates was performed by agar well diffusion method and minimal inhibitory concentration. Body samples of all eligible patients were collected and cultured. Finally, 50 (25%) out of the total cultured samples were S. Typhi bacteria isolated from different samples. The bacteria were mainly found in blood, followed by stool and fluid (74%, 24%, and 2%, respectively). On differential medium, xylose lysine deoxycholate agar, the colonies appear red with black centers, while on MacConkey agar, the colonies appear smooth, pale, transparent, colorless, and raised. Regarding the inhibition zone values of bacteriocins of Lactobacillus from Yogurt against S. typhi in plate, significant differences were identified between the ones with and without prebiotic addition. Accordingly, the value of the inhibition zone for those without prebiotic addition (13.18±7.403) was significantly lower than that of cutoff values of 20 with a significant difference of -6.820 (t= -6.514, df 49, P=0.000). Moreover, the inhibition effect of prebiotics (inulin and starch) against S. typhi at 37 °C for 24 h in part dish glucose as control, only the mean of inulin was found to be significantly lower than that of the cutoff value of 18 with the mean difference of -3.900 (t=-4.115, df 49, P=0.000). Other prebiotics of glucose and starch in 24 h showed negative inhibition. Probiotics are live microorganisms that have beneficial host effects by enhancing microbial balance in the intestine, whereas prebiotics are indigestible food components having beneficial effects by enhancing the activity and growth of one or more colonic bacteria. Lactobacillus filtrates had considerable effects against the test S. typhi isolates.

Integron-Associated Antibiotic Resistance in Salmonella typhi

Salmonella enteric serovar Typhi (S. typhi) and paratyphi (S. paratyphi) bacteria exclusively found in humans, cause typhoid fever, an acute, and possibly deadly systemic infection. Typhoid fever is caused by a species of rod-shaped, Gram-negative Enterobacteriaceae called S. typhi. The present study aimed to examine the intI gene and investigate the possible relation between this gene and multi-drug resistance in S. typhi. A total of 30 blood samples were obtained from patients who were suspicious of typhoid fever using the direct strategy of inoculation. Each specimen was injected into a culture of a selective medium, such as XLD and SS agar, and then incubated at 37°C for 24 h. The genomic DNA was extracted through a boiling process. Tris-EDTA was used to suspend bacterial colonies cultured on MacConkey agar plates. The suspension of bacterial colonies was centrifuged for 5 min at 8000×g and for 20 min at -20°C which lyses the organisms and extracts the DNA from the buffer. The supernatant is then transferred to a fresh Eppendorf tube. Gel electrophoresis was carried out utilizing a UV transilluminator. The intI gene for S. typhi was found using a PCR test. The antibiotic sensitivity testing showed that the S. typhi isolates were classed as multi-resistant. These results were confirmed using the polymerase chain reaction (PCR) technique using intI gene where twenty specimens isolated from typhoid patients were positive for S. typhi.

Epidemiology of Multidrug Resistance among Salmonella enterica serovars typhi and paratyphi A at a Tertiary Pediatric Hospital in India Over a Decade; In-silico Approach to Elucidate the Molecular Mechanism of Quinolone Resistance

BACKGROUND

Enteric fever caused by Salmonella enterica serovar typhi and Salmonella enterica serovar paratyphi A remains one of the most common causes of community-acquired bloodstream infection among children in India. Multidrug resistance is emerging and is a cause of concern as it affects the choice of treatment in enteric fever.

METHOD

In this study, a 10-year analysis of resistance patterns was done along with in-silico homology modeling and molecular docking to understand the commonly occurring quinolone resistance.

RESULTS

A total of 1010 cases of blood culture-confirmed enteric fevers (S. typhi n=849; S. paratyphi A n=161) were recorded at the study hospital during the period from 2011-2020. Multidrug resistance among cases of S. typhi was 2.12 %, whereas it was completely absent among cases of S. paratyphi A. Fluoroquinolone resistance was high (>95%) throughout the study period. Resistance to ampicillin, chloramphenicol and co-trimoxacole was low (<3%) among S. typhi cases. No deaths were observed among study participants. Molecular docking analysis showed that quinolone had less binding affinity to mutated gyrase A than to its wild type for both S. typhi and S. paratyphi A.

CONCLUSION

Quinolone resistance was high among cases of enteric fever, whereas no resistance was observed among third-generation cephalosporins. In-silico studies indicated that a mutation in gyrase A might be the cause of the gradual increase in ciprofloxacin resistance over the study period.

Antibiotic resistome of Salmonella typhi: molecular determinants for the emergence of drug resistance

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.

Typhi as a potential candidate for acute typhoid

Typhoid fever caused by human restricted Salmonella typhi presents a considerable health burden on developing South-Asian nations like India. The suboptimal sensitivity and specificity associated with culture-based isolation of etiological agent and the extensively used surface antigen-based serological assays often lead to misdiagnosis and inappropriate antimicrobial treatment. The increasing reports of the emergence of resistant strains and undefined disease burden signify the critical need for an inexpensive, reliable, easy-to-use, and highly sensitive diagnostic test for typhoid fever. Utilizing S. typhi-specific and immunogenic antigens in sero-diagnostic assays could lead to precise diagnosis of acute typhoid and prompt treatment. In this study, we report cloning, expression, and purification of recombinant Cytolethal distending toxin subunit B (CdtB) of S. typhi, which is reported to be highly specific, immunogenic, and expressed only upon S. typhi infection. We further evaluated the purified recombinant CdtB for its diagnostic potential in an IgM-based indirect ELISA format using 33 human samples. Twenty-one serum samples from blood culture confirmed cases (n = 21) of typhoid and 12 samples from healthy controls (n = 12) were tested. The assay showed sensitivity of 100% and specificity of 83.3% respectively with positive and negative predictive values of 91.3 and 100% respectively. Efficient detection of specific IgM antibodies indicates that CdtB could be highly valuable in sero-diagnosis of acute typhoid and rapid screening of clinical samples.

Acute epididymo-orchitis due to Salmonella Typhi in a young man from Bangladesh

S. typhi infection rarely involves the genitourinary system. We report the first described case of acute epididymo-orchitis due to S. typhi in a 14-year-old boy from Bangladesh. A high index of suspicion should be maintained when evaluating patients coming from endemic countries also in case of unusual sites of infection.

Burden of intestinal pathogens and associated factors among asymptomatic food handlers in South Ethiopia: emphasis on salmonellosis

Objective

The study aims to assess the burden of intestinal parasites and Salmonellosis among asymptomatic food handlers at meal serving facilities in Sodo town. Antibiotic resistance was also common and increasing among Salmonella isolates with multidrug resistance as current concern.

Result

Community based cross-sectional study was carried out from 387 food handlers working in meal serving facilities. Food handlers, 159(41%) had one or more intestinal parasites. A. lumbricoides was the most prevalent parasite 30(7.8%), followed by Taenia species 26(6.7%) and Hook worm 23(5.9%). A total number of 35 Salmonella isolates were found of which Sero-group D was the most frequent, 17(48.5%) followed by Sero-group C, 12(34.3%), and B 6(17.1%). Ten (2.5%) isolates were Salmonella typhi. Raw meat eating, hand washing after toilet and after touching dirty materials showed significant association with intestinal pathogens. Salmonella isolates were highly resistant to ampicillin (85.7%), amoxicillin and tetracycline 74.3% each. Multidrug resistance prevalence of 81.8% was identified. Periodic screening of food handlers is important in order to prevent the transmission of intestinal parasites and Salmonellosis. Treatment needs to be based on accurate laboratory detection to mitigate the spread of drug resistant Salmonella strains.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3610-4) contains supplementary material, which is available to authorized users.

Detection of typhoid fever by diatom-based optical biosensor

Surface-modified diatom substrates are employed for the development of immunocomplex-based optical biosensor for diagnosis of typhoid. Biosensor has been prepared by covalent immobilization of Salmonella typhi antibody onto the crosslinked diatom substrates via glutaraldehyde. Photoluminescent (PL) studies revealed good specificity and ability of conjugated diatom substrates to distinguish complementary (S. typhi) and non-complementary (Escherichia coli) antigens. The immunocomplexed biosensor showed detection limit of 10 pg. The excellent performance of biosensor is associated to its large surface-to-volume ratio, good photoluminescent property, and biocompatibility of diatom frustules, which enhances the antibody immobilization and facilitates the nucleophilic electron transfer between antibody and conjugated diatom surface. Hence, immunocomplexed diatom substrates are considered to be a suitable platform for the environmental monitoring of water-borne pathogen S. typhi.

Salmonella Typhi genomics: envisaging the future of typhoid eradication

Next-generation whole-genome sequencing has revolutionised the study of infectious diseases in recent years. The availability of genome sequences and its understanding have transformed the field of molecular microbiology, epidemiology, infection treatments and vaccine developments. We review the key findings of the publicly accessible genomes of Salmonella enterica serovar Typhi since the first complete genome to the most recent release of thousands of Salmonella Typhi genomes, which remarkably shape the genomic research of S. Typhi and other pathogens. Important new insights acquired from the genome sequencing of S. Typhi, pertaining to genomic variations, evolution, population structure, antibiotic resistance, virulence, pathogenesis, disease surveillance/investigation and disease control are discussed. As the numbers of sequenced genomes are increasing at an unprecedented rate, fine variations in the gene pool of S. Typhi are captured in high resolution, allowing deeper understanding of the pathogen's evolutionary trends and its pathogenesis, paving the way to bringing us closer to eradication of typhoid through effective vaccine/treatment development.

Gene Specific DNA Sensors for Diagnosis of Pathogenic Infections

Gene specific DNA based sensors have potential applications for rapid and real time monitoring of hybridization signal with the target nucleic acid of pathogens. Different types of DNA based sensors and their applications have been studied for rapid and accurate detection of pathogens causing human diseases. These sensors are based on surface plasmon resonance, quantum-dots, molecular beacons, piezoelectric and electrochemical etc. Curbing epidemics at an early stage is one of the massive challenges in healthcare systems. Timely detection of the causative organism may provide a solution to restrain mortality caused by the disease. With the advent of interdisciplinary sciences, bioelectronics has emerged as an effective alternative for disease diagnostics. Gene specific DNA sensors present themselves as cost-effective, sensitive and specific platforms for detection of disease causing pathogens. The mini review explores different transducer based sensors and their potential in diagnosis of acute and chronic diseases.

Antimicrobial resistance in Salmonella enterica serovar typhi and paratyphi in South Asia-current status, issues and prospects

The human race owes a debt of gratitude to antimicrobial agents, penicillin and its successors that have saved people from tremendous pain and suffering in the last several decades. Unfortunately, this consideration is no more true, as millions of people are prone to the challenging threat of emergence of antimicrobial resistance worldwide and the menace is more distressing in developing countries. Comparable with other bacterial species, Salmonella enterica serovar Typhi (S. typhi) and Paratyphi (S. paratyphi) have been evolving multidrug resistance (MDR) against a wide array of antibiotics, including chloramphenicol, ampicillin and co-trimoxazole, and globally affecting 21 million people with 220,000 deaths each year. S. typhi and S. paratyphi infections are also endemic in South Asia and a series of antibiotics used to treat these infections, have been losing efficacy against enteric fever. Currently, quinolones are regarded as a choice to treat MDR Salmonella in these regions. Travel-related cases of enteric fever, especially from South Asian countries are the harbinger of the magnitude of MDR Salmonella in that region. Conclusively, the MDR will continue to grow and the available antimicrobial agents would become obsolete. Therefore, a radical and aggressive approach in terms of rational use of antibiotics during treating infections is essentially needed.

typhi

Twenty strains each of susceptible and multiple drug resistant strains of S. typhi were compared for susceptibility to complement lysis and cellular invasion. Drug resistant strains showed increased resistance to complement killing. Antibody increased the efficiency of complement killing of S. typhi. Susceptible and drug resistant strains showed almost the same rates of adherence and invasion of HeLa cells and human monocyte cell lines. However, the resistant strains showed a relatively higher rate of intracellular multiplication after 6 hours within human mononuclear macrophages. Decreased killing by complement and the relatively higher multiplication within mononuclear macrophages of the drug resistant strains may be the reason for their increased virulence.

SCANNING ELECTRON MICROSCOPIC STUDY OF HeLa CELL INVASION BY SALMONELLA TYPHI

Invasion of cultured non-pliagoeytic cells by salmonella is illustrated by a scanning electron microscopie study of HeLa cell invasion by S. typhi. This study shows that after bacterial adherence the HeLa cell cytoplasmic membrane shows ruffling and formation of filopodia which gradually engulf the bacterium and draw it into the cytoplasm. The available literature is reviewed and the probable mechanism underlying phagocytosis is hypothesized.