Tracking the shift in enteric fever trends and evolving antibiotic sensitivity patterns.

Objective: This study aims to examine the frequency of Salmonella Paratyphi found in blood cultures and evaluate the antibiotic susceptibility pattern of Salmonella isolates to different antibiotics. Additionally, the study aims to assess the paradigm shift in the trend of enteric fever caused by Salmonella Typhi (S. Typhi) to Salmonella Paratyphi(S. Paratyphi) . Study Design: Retrospective study. Participant: The study enrolled patients aged 12 years and above diagnosed with enteric fever (positive blood culture) and admitted to Peelamedu Samanaidu Govindasamy Naidu (PSG) Hospital. Interventions: The study analyzed demographic and antibiotic susceptibility profiles of Salmonella isolates collected from 106 enteric fever patients in the hospital between 2010 and 2022. The susceptibility profiles of Salmonella isolates to multiple antibiotics were assessed. Results: There were 106 participants, and 95 (89.62%) of them had enteric fever linked to Salmonella Typhi, while only 11 (10.38%) had enteric fever linked to Salmonella Paratyphi A. From 2010 to 2022, the study discovered a general decline in the prevalence of enteric fever caused by Salmonella species. But between 2014 and 2022, the incidence of enteric fever linked to S. Typhi rapidly increased. Azithromycin (100% , n = 106) and ceftriaxone (99% , n = 105) were highly effective against the Salmonella isolates, whereas nalidixic acid was resisted by 3 isolates (4.72%, n = 3). Conclusion: The study observed a higher incidence of Salmonella Typhi in comparison to Paratyphi A and a greater susceptibility of males to enteric fever. Funding: None declared.

Molecular Detection of Salmonella typhi Isolated from Patients Undergoing Gallbladder Cholecystectomy in Baghdad.

BACKGROUND: Salmonella typhi is a specific strain of the Salmonella bacterium, responsible for triggering typhoid fever; a significant public health concern in developing nations. OBJECTIVE: The current study aimed to identify the bacteria from the gallbladder, taken during cholecystectomies of patients, by isolating Salmonella typhi and by using microscopic characteristics, biochemical and polymerase chain reaction (PCR) tests. METHODS: A total of 120 specimens were collected from the Baghdad Teaching Hospital, Iraq. A cross-sectional descriptive study was carried out from October, 2021, to July, 2022. During that study, 26 (54.2%) male patient tested positive for Salmonella typhias well as 22 (45.8%) female patients. The age of the patients varied from < 30 to > 60 years. p-value > 0.05 was considered significant to confirm a relationship between age and Salmonella typhi effect for patients. RESULTS: Out of the 120 blood samples taken for this study, 48 (40%) tested positive by use of PCR test, 40 (33.3%) tested positive by use of the Widal test, 35 (29.1%) were positive for biopsy culture, and 35 (29.1%) were positive for blood culture. All Salmonella typhi isolates were found to be sensitive to the imipenem, cefepime, and ceftriaxone, but were resistant to gentamycin, ciprofloxacin, amikacin, erythromycin, and tetracycline (72%, 29%, 43%, 100%, 100%, respectively). CONCLUSIONS: The real time polymerase chain reaction (RT-PCR) tests and the Vitek 2 compact system showed a high level of accuracy in the detection of Salmonella typhi. Multidrug resistance was observed, which should be a signal to reduce antibiotic consumption.

The origins of haplotype 58 (H58) Salmonella enterica serovar Typhi.

Antimicrobial resistance (AMR) poses a serious threat to the clinical management of typhoid fever. AMR in Salmonella Typhi (S. Typhi) is commonly associated with the H58 lineage, a lineage that arose comparatively recently before becoming globally disseminated. To better understand when and how H58 emerged and became dominant, we performed detailed phylogenetic analyses on contemporary genome sequences from S. Typhi isolated in the period spanning the emergence. Our dataset, which contains the earliest described H58 S. Typhi organism, indicates that ancestral H58 organisms were already multi-drug resistant (MDR). These organisms emerged spontaneously in India in 1987 and became radially distributed throughout South Asia and then globally in the ensuing years. These early organisms were associated with a single long branch, possessing mutations associated with increased bile tolerance, suggesting that the first H58 organism was generated during chronic carriage. The subsequent use of fluoroquinolones led to several independent mutations in gyrA. The ability of H58 to acquire and maintain AMR genes continues to pose a threat, as extensively drug-resistant (XDR; MDR plus resistance to ciprofloxacin and third generation cephalosporins) variants, have emerged recently in this lineage. Understanding where and how H58 S. Typhi originated and became successful is key to understand how AMR drives successful lineages of bacterial pathogens. Additionally, these data can inform optimal targeting of typhoid conjugate vaccines (TCVs) for reducing the potential for emergence and the impact of new drug-resistant variants. Emphasis should also be placed upon the prospective identification and treatment of chronic carriers to prevent the emergence of new drug resistant variants with the ability to spread efficiently.

Transcriptional profiling links unique human macrophage phenotypes to the growth of intracellular Salmonella enterica serovar Typhi.

Macrophages provide a crucial environment for Salmonella enterica serovar Typhi (S. Typhi) to multiply during typhoid fever, yet our understanding of how human macrophages and S. Typhi interact remains limited. In this study, we delve into the dynamics of S. Typhi replication within human macrophages and the resulting heterogeneous transcriptomic responses of macrophages during infection. Our study reveals key factors that influence macrophage diversity, uncovering distinct immune and metabolic pathways associated with different stages of S. Typhi intracellular replication in macrophages. Of note, we found that macrophages harboring replicating S. Typhi are skewed towards an M1 pro-inflammatory state, whereas macrophages containing non-replicating S. Typhi exhibit neither a distinct M1 pro-inflammatory nor M2 anti-inflammatory state. Additionally, macrophages with replicating S. Typhi were characterized by the increased expression of genes associated with STAT3 phosphorylation and the activation of the STAT3 transcription factor. Our results shed light on transcriptomic pathways involved in the susceptibility of human macrophages to intracellular S. Typhi replication, thereby providing crucial insight into host phenotypes that restrict and support S. Typhi infection.

The frequency and associated factors of typhoid carriage in patients undergoing cholecystectomy for gallbladder disease in Pakistan: A cross-sectional study.

BACKGROUND: Enteric fever is caused by Salmonella enterica serovars Typhi (S. Typhi) and Paratyphi A, B, and C. It continues to be a significant cause of morbidity and mortality worldwide. In highly endemic areas, children are disproportionately affected, and antimicrobial resistance reduces therapeutic options. It is estimated that 2-5% of enteric fever patients develop chronic asymptomatic infection. These carriers may act as reservoirs of infection; therefore, the prospective identification and treatment of carriers are critical for long-term disease control. We aimed to find the frequency of Salmonella Typhi carriers in patients undergoing cholecystectomy. We also compared the detection limit of culturing versus qPCR in detecting S. Typhi, performed a geospatial analysis of the carriers identified using this study, and evaluated the accuracy of anti-Vi and anti-YncE in identifying chronic typhoid carriage. METHODS: We performed a cross-sectional study in two centers in Pakistan. Gallbladder specimens were subjected to quantitative PCR (qPCR) and serum samples were analyzed for IgG against YncE and Vi by ELISA. We also mapped the residential location of those with a positive qPCR result. FINDINGS: Out of 988 participants, 3.4% had qPCR-positive gallbladder samples (23 S. Typhi and 11 S. Paratyphi). Gallstones were more likely to be qPCR positive than bile and gallbladder tissue. Anti-Vi and YncE were significantly correlated (r = 0.78 p<0.0001) and elevated among carriers as compared to qPCR negative controls, except for anti-Vi response in Paratyphi A. But the discriminatory values of these antigens in identifying carriers from qPCR negative controls were low. CONCLUSION: The high prevalence of typhoid carriers observed in this study suggests that further studies are required to gain information that will help in controlling future typhoid outbreaks in a superior manner than they are currently being managed.

Single missense mutations in Vi capsule synthesis genes confer hypervirulence to Salmonella Typhi.

Many bacterial pathogens, including the human exclusive pathogen Salmonella Typhi, express capsular polysaccharides as a crucial virulence factor. Here, through S. Typhi whole genome sequence analyses and functional studies, we found a list of single point mutations that make S. Typhi hypervirulent. We discovered a single point mutation in the Vi biosynthesis enzymes that control Vi polymerization or acetylation is enough to result in different capsule variants of S. Typhi. All variant strains are pathogenic, but the hyper Vi capsule variants are particularly hypervirulent, as demonstrated by the high morbidity and mortality rates observed in infected mice. The hypo Vi capsule variants have primarily been identified in Africa, whereas the hyper Vi capsule variants are distributed worldwide. Collectively, these studies increase awareness about the existence of different capsule variants of S. Typhi, establish a solid foundation for numerous future studies on S. Typhi capsule variants, and offer valuable insights into strategies to combat capsulated bacteria.

Enteric Fever in Children: An Epidemiological and Clinical Review of Cases in Southeast Texas.

Extensively drug-resistant (XDR) strains of Salmonella enterica serotype Typhi have emerged in Pakistan and Iraq. We report 13 children with enteric fever in Southeast Texas seen over 3.5 years, of whom 23.1% had XDR isolates.

The Salmonella typhi Cell Division Activator Protein StCAP Impacts Pathogenesis by Influencing Critical Molecular Events.

Conserved molecular signatures in multidrug-resistant Salmonella typhi can serve as novel therapeutic targets for mitigation of infection. In this regard, we present the S. typhi cell division activator protein (StCAP) as a conserved target across S. typhi variants. From in silico and fluorimetric assessments, we found that StCAP is a DNA-binding protein. Replacement of the identified DNA-interacting residue Arg34 of StCAP with Ala34 showed a dramatic (15-fold) increase in Kd value compared to the wild type (Kd 546 nm) as well as a decrease in thermal stability (10 °C shift). Out of the two screened molecules against the DNA-binding pocket of StCAP, eltrombopag, and nilotinib, the former displayed better binding. Eltrombopag inhibited the stand-alone S. typhi culture with an IC50 of 38 µM. The effect was much more pronounced on THP-1-derived macrophages (T1Mac) infected with S. typhi where colony formation was severely hindered with IC50 reduced further to 10 µM. Apoptotic protease activating factor1 (Apaf1), a key molecule for intrinsic apoptosis, was identified as an StCAP-interacting partner by pull-down assay against T1Mac. Further, StCAP-transfected T1Mac showed a significant increase in LC3 II (autophagy marker) expression and downregulation of caspase 3 protein. From these experiments, we conclude that StCAP provides a crucial survival advantage to S. typhi during infection, thereby making it a potent alternative therapeutic target.

Ultrasensitive detection of Salmonella typhi using a PAM-free Cas14a-based biosensor.

The effectiveness of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas14a1, widely utilized for pathogenic microorganism detection, has been limited by the requirement of a protospacer adjacent motif (PAM) on the target DNA strands. To overcome this limitation, this study developed a Single Primer isothermal amplification integrated-Cas14a1 biosensor (SPCas) for detecting Salmonella typhi that does not rely on a PAM sequence. The SPCas biosensor utilizes a novel primer design featuring an RNA-DNA primer and a 3'-biotin-modified primer capable of binding to the same single-stranded DNA (ssDNA) in the presence of the target gene. The RNA-DNA primer undergoes amplification and is blocked at the biotin-modified end. Subsequently, strand replacement is initiated to generate ssDNA assisted by RNase H and Bst enzymes, which activate the trans-cleavage activity of Cas14a1 even in the absence of a PAM sequence. Leveraging both cyclic chain replacement reaction amplification and Cas14a1 trans-cleavage activity, the SPCas biosensor exhibits a remarkable diagnostic sensitivity of 5 CFU/mL. Additionally, in the assessment of 20 milk samples, the SPCas platform demonstrated 100% diagnostic accuracy, which is consistent with the gold standard qPCR. This platform introduces a novel approach for developing innovative CRISPR-Cas-dependent biosensors without a PAM sequence.

Development, confirmation, and application of a seeded Escherichia coli process control organism to validate Salmonella enterica serovar Typhi environmental surveillance methods.

Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of Typhoid fever. Blood culture is the gold standard for clinical diagnosis, but this is often difficult to employ in resource limited settings. Environmental surveillance of waste-impacted waters is a promising supplement to clinical surveillance, however validating methods is challenging in regions where S. Typhi concentrations are low. To evaluate existing S. Typhi environmental surveillance methods, a novel process control organism (PCO) was created as a biosafe surrogate. Using a previous described qPCR assay, a modified PCR amplicon for the staG gene was cloned into E. coli. We developed a target region that was recognized by the Typhoid primers in addition to a non-coding internal probe sequence. A multiplex qPCR reaction was developed that differentiates between the typhoid and control targets, with no cross-reactivity or inhibition of the two probes. The PCO was shown to mimic S. Typhi in lab-based experiments with concentration methods using primary wastewater: filter cartridge, recirculating Moore swabs, membrane filtration, and differential centrifugation. Across all methods, the PCO seeded at 10 CFU/mL and 100 CFU/mL was detected in 100% of replicates. The PCO is detected at similar quantification cycle (Cq) values across all methods at 10 CFU/mL (Average = 32.4, STDEV = 1.62). The PCO was also seeded into wastewater at collection sites in Vellore (India) and Blantyre (Malawi) where S. Typhi is endemic. All methods tested in both countries were positive for the seeded PCO. The PCO is an effective way to validate performance of environmental surveillance methods targeting S. Typhi in surface water.

Uncovering the growing burden of enteric fever: A molecular analysis of Salmonella Typhi antimicrobial resistance.

Enteric fever, a persistent public health challenge in developing regions, is exacerbated by suboptimal socioeconomic conditions, contaminated water and food sources, and insufficient sanitation. This study delves into the antimicrobial susceptibility of Salmonella Typhi, uncovering the genetic underpinnings of its resistance. Analyzing 897 suspected cases, we identified a significant prevalence of typhoid fever, predominantly in males (58.3 %) and younger demographics. Alarmingly, our data reveals an escalation in resistance to both primary and secondary antibiotics, with cases of multi-drug resistant (MDR) and extensively drug-resistant (XDR) S. Typhi reaching 14.7 % and 43.4 %, respectively, in 2021. The Multiple Antibiotic Resistance (MAR) index exceeded 0.2 in over half of the isolates, signaling widespread antibiotic misuse. The study discerned 47 unique antibiotic resistance patterns and pinpointed carbapenem and macrolide antibiotics as the remaining effective treatments against XDR strains, underlining the critical need to preserve these drugs for severe cases. Molecular examinations identified blaTEM, blaSHV, and blaCTX-M genes in ceftriaxone-resistant strains, while qnrS was specific to ciprofloxacin-resistant variants. Notably, all examined strains exhibited a singular mutation in the gyrA gene, maintaining wild-type gyrB and parC genes. The erm(B) gene emerged as the primary determinant of azithromycin resistance. Furthermore, a distressing increase in resistance genes was observed over three years, with erm(B), blaTEM and qnrS showing significant upward trends. These findings are a clarion call for robust antimicrobial stewardship programs to curtail inappropriate antibiotic use and forestall the burgeoning threat of antibiotic resistance in S. Typhi.

Loss of function of metabolic traits in typhoidal Salmonella without apparent genome degradation.

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively adapted to the human host, where they can cause life-long persistent infection. A distinct feature of these serovars is the presence of a relatively high number of degraded coding sequences coding for metabolic pathways, most likely a consequence of their adaptation to a single host. As a result of convergent evolution, these serovars shared many of the degraded coding sequences although often affecting different genes in the same metabolic pathway. However, there are several coding sequences that appear intact in one serovar while clearly degraded in the other, suggesting differences in their metabolic capabilities. Here, we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. Thus, the inability of S. Typhi to metabolize Glucose-6-Phosphate or 3-phosphoglyceric acid is due to the silencing of the expression of the genes encoding the transporters for these compounds due to point mutations in the transcriptional regulatory proteins. In contrast, its inability to utilize glucarate or galactarate is due to the presence of point mutations in the transporter and enzymes necessary for the metabolism of these sugars. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars and highlight a limitation of bioinformatic approaches to predict metabolic capabilities. IMPORTANCE: Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars can only infect the human host, where they can cause life-long persistent infection. Because of their adaptation to the human host, these bacterial pathogens have changed their metabolism, leading to the loss of their ability to utilize certain nutrients. In this study we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars.

Predominance of multidrug-resistant Salmonella Typhi genotype 4.3.1 with low-level ciprofloxacin resistance in Zanzibar.

BACKGROUND: Typhoid fever is a common cause of febrile illness in low- and middle-income countries. While multidrug-resistant (MDR) Salmonella Typhi (S. Typhi) has spread globally, fluoroquinolone resistance has mainly affected Asia. METHODS: Consecutively, 1038 blood cultures were obtained from patients of all age groups with fever and/or suspicion of serious systemic infection admitted at Mnazi Mmoja Hospital, Zanzibar in 2015-2016. S. Typhi were analyzed with antimicrobial susceptibility testing and with short read (61 strains) and long read (9 strains) whole genome sequencing, including three S. Typhi strains isolated in a pilot study 2012-2013. RESULTS: Sixty-three S. Typhi isolates (98%) were MDR carrying blaTEM-1B, sul1 and sul2, dfrA7 and catA1 genes. Low-level ciprofloxacin resistance was detected in 69% (43/62), with a single gyrase mutation gyrA-D87G in 41 strains, and a single gyrA-S83F mutation in the non-MDR strain. All isolates were susceptible to ceftriaxone and azithromycin. All MDR isolates belonged to genotype 4.3.1 lineage I (4.3.1.1), with the antimicrobial resistance determinants located on a composite transposon integrated into the chromosome. Phylogenetically, the MDR subgroup with ciprofloxacin resistance clusters together with two external isolates. CONCLUSIONS: We report a high rate of MDR and low-level ciprofloxacin resistant S. Typhi circulating in Zanzibar, belonging to genotype 4.3.1.1, which is widespread in Southeast Asia and African countries and associated with low-level ciprofloxacin resistance. Few therapeutic options are available for treatment of typhoid fever in the study setting. Surveillance of the prevalence, spread and antimicrobial susceptibility of S. Typhi can guide treatment and control efforts.

Extensively drug-resistant Salmonella Typhi leading to relapsed urinary tract infection: A case report.

Salmonella enterica serotype Typhi (S Typhi) associated urinary tract infections are exceedingly rare, accounting for less than 1% of cases. Such infections have known to occur in immune-compromised or individuals with urogenital structural abnormalities. With the emergence of extensively drug resistant S Typhi strains in Pakistan, the management of its various unique presentations poses therapeutic challenges. We report the first documented case of a 74 years old male patient presenting with relapsed urinary tract infection secondary to extensively drug resistant S Typhi.

Alternate typhoid toxin assembly evolved independently in the two Salmonella species.

AB5-type toxins are a diverse family of protein toxins composed of an enzymatic active (A) subunit and a pentameric delivery (B) subunit. Salmonella enterica serovar Typhi's typhoid toxin features two A subunits, CdtB and PltA, in complex with the B subunit PltB. Recently, it was shown that S. Typhi encodes a horizontally acquired B subunit, PltC, that also assembles with PltA/CdtB to produce a second form of typhoid toxin. S. Typhi therefore produces two AB5 toxins with the same A subunits but distinct B subunits, an evolutionary twist that is unique to typhoid toxin. Here, we show that, remarkably, the Salmonella bongori species independently evolved an analogous capacity to produce two typhoid toxins with distinct B subunits. S. bongori's alternate B subunit, PltD, is evolutionarily distant from both PltB and PltC and outcompetes PltB to form the predominant toxin. We show that, surprisingly, S. bongori elicits similar levels of CdtB-mediated intoxication as S. Typhi during infection of cultured human epithelial cells. This toxicity is exclusively due to the PltB toxin, and strains lacking pltD produce increased amounts of PltB toxin and exhibit increased toxicity compared to the wild type, suggesting that the acquisition of the PltD subunit potentially made S. bongori less virulent toward humans. Collectively, this study unveils a striking example of convergent evolution that highlights the importance of the poorly understood "two-toxin" paradigm for typhoid toxin biology and, more broadly, illustrates how the flexibility of A-B interactions has fueled the evolutionary diversification and expansion of AB5-type toxins. IMPORTANCE: Typhoid toxin is an important Salmonella Typhi virulence factor and an attractive target for therapeutic interventions to combat typhoid fever. The recent discovery of a second version of this toxin has substantial implications for understanding S. Typhi pathogenesis and combating typhoid fever. In this study, we discover that a remarkably similar two-toxin paradigm evolved independently in Salmonella bongori, which strongly suggests that this is a critical aspect of typhoid toxin biology. We observe significant parallels between how the two toxins assemble and their capacity to intoxicate host cells during infection in S. Typhi and S. bongori, which provides clues to the biological significance of this unusual toxin arrangement. More broadly, AB5 toxins with diverse activities and mechanisms are essential virulence factors for numerous important bacterial pathogens. This study illustrates the capacity for novel A-B interactions to evolve and thus provides insight into how such a diverse arsenal of toxins might have emerged.

Nuclear factor kappa B-dependent persistence of Salmonella Typhi and Paratyphi in human macrophages.

Salmonella serovars Typhi and Paratyphi cause a prolonged illness known as enteric fever, whereas other serovars cause acute gastroenteritis. Mechanisms responsible for the divergent clinical manifestations of nontyphoidal and enteric fever Salmonella infections have remained elusive. Here, we show that S. Typhi and S. Paratyphi A can persist within human macrophages, whereas S. Typhimurium rapidly induces apoptotic macrophage cell death that is dependent on Salmonella pathogenicity island 2 (SPI2). S. Typhi and S. Paratyphi A lack 12 specific SPI2 effectors with pro-apoptotic functions, including nine that target nuclear factor κB (NF-κB). Pharmacologic inhibition of NF-κB or heterologous expression of the SPI2 effectors GogA or GtgA restores apoptosis of S. Typhi-infected macrophages. In addition, the absence of the SPI2 effector SarA results in deficient signal transducer and activator of transcription 1 (STAT1) activation and interleukin 12 production, leading to impaired TH1 responses in macrophages and humanized mice. The absence of specific nontyphoidal SPI2 effectors may allow S. Typhi and S. Paratyphi A to cause chronic infections. IMPORTANCE: Salmonella enterica is a common cause of gastrointestinal infections worldwide. The serovars Salmonella Typhi and Salmonella Paratyphi A cause a distinctive systemic illness called enteric fever, whose pathogenesis is incompletely understood. Here, we show that enteric fever Salmonella serovars lack 12 specific virulence factors possessed by nontyphoidal Salmonella serovars, which allow the enteric fever serovars to persist within human macrophages. We propose that this fundamental difference in the interaction of Salmonella with human macrophages is responsible for the chronicity of typhoid and paratyphoid fever, suggesting that targeting the nuclear factor κB (NF-κB) complex responsible for macrophage survival could facilitate the clearance of persistent bacterial infections.

Typhoidal salmonella disease in Mukuru informal settlement, Nairobi Kenya; carriage, diversity, and antimicrobial resistant genes.

INTRODUCTION: Multiple studies have shown that typhoid fever is endemic in developing countries characterized by poor hygiene. A unique way of Salmonella Typhi (S.Typhi) pathogenicity is establishing a persistent, usually asymptomatic carrier state in some infected individuals who excrete large numbers of bacteria in faeces. This study aimed to determine the isolation rate of S.Typhi from blood and stool samples among cases and asymptomatic individuals in the Mukuru informal settlement and identify antibiotic resistance patterns within the same population. MATERIALS AND METHODS: We recruited 1014 outpatient participants presenting with typhoid-like symptoms in selected health centres in Nairobi, Kenya. Bacterial isolation was done on Xylose Lysine Deoxycholate agar (XLD) and Mac Conkey agar (Oxoid), followed by standard biochemical tests. Identification was done using API20E, and S.Typhi was confirmed by serotyping using polyvalent antisera 0-9 and monovalent antisera d. The Kirby-Bauer disc diffusion method was used to test the antimicrobial susceptibility of S.Typhi isolates, while Multi-Drug Resistant (MDR) strains were characterized using conventional PCR. RESULTS: Of 1014 participants, 54 (5%) tested positive for S.Typhi. Thirty-eight (70%) of the S.Typhi isolated were from stool samples, while sixteen (30%) were from blood. Three (0.2%) of the isolates were from asymptomatic carriers. Of the 54 S.Typhi isolates, 20 (37%) were MDR. Resistance to ciprofloxacin and nalidixic acid was 43% and 52%, respectively. Resistance to amoxicillin-clavulanic acid (a beta-lactam inhibitor) was 2%. The BlaTEM-1 gene was present in 19/20 (95%) MDR isolates. CONCLUSION: MDR S.Typhi is prevalent in Mukuru Informal settlement. The sharp increase in nalidixic acid resistance is an indication of reduced susceptibility to fluoroquinolones, which are currently the recommended drugs for the treatment of typhoid fever. This study highlights the need for effective antimicrobial stewardship and routine surveillance of antimicrobial resistance (AMR) to inform policy on the prevention and control of MDR Typhoid disease.

Large outbreak of typhoid fever on a river cruise ship used as accommodation for asylum seekers, the Netherlands, 2022.

On 6 April 2022, the Public Health Service of Kennemerland, the Netherlands, was notified about an outbreak of fever and abdominal complaints on a retired river cruise ship, used as shelter for asylum seekers. The diagnosis typhoid fever was confirmed on 7 April. An extensive outbreak investigation was performed. Within 47 days, 72 typhoid fever cases were identified among asylum seekers (n = 52) and staff (n = 20), of which 25 were hospitalised. All recovered after treatment. Consumption of food and tap water on the ship was associated with developing typhoid fever. The freshwater and wastewater tanks shared a common wall with severe corrosion and perforations, enabling wastewater to leak into the freshwater tank at high filling levels. Salmonella Typhi was cultured from the wastewater tank, matching the patient isolates. In the freshwater tank, Salmonella species DNA was detected by PCR, suggesting the presence of the bacterium and supporting the conclusion of contaminated freshwater as the probable source of the outbreak. Outbreaks of uncommon infections may occur if persons from endemic countries are accommodated in crowded conditions. Especially when accommodating migrants on ships, strict supervision on water quality and technical installations are indispensable to guarantee the health and safety of the residents.