Prevalence and trends in the antimicrobial susceptibility pattern of Salmonella enterica serovars Typhi and Paratyphi A among children in a pediatric tertiary care hospital in South India over a period of ten years: a retrospective study

Molecular characterization of circulating Salmonella Typhi strains in an urban informal settlement in Kenya

A high burden of Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) bacteremia has been reported from urban informal settlements in sub-Saharan Africa, yet little is known about the introduction of these strains to the region. Understanding regional differences in the predominant strains of S. Typhi can provide insight into the genomic epidemiology. We genetically characterized 310 S. Typhi isolates from typhoid fever surveillance conducted over a 12-year period (2007–2019) in Kibera, an urban informal settlement in Nairobi, Kenya, to assess the circulating strains, their antimicrobial resistance attributes, and how they relate to global S. Typhi isolates. Whole genome multi-locus sequence typing (wgMLST) identified 4 clades, with up to 303 pairwise allelic differences. The identified genotypes correlated with wgMLST clades. The predominant clade contained 290 (93.5%) isolates with a median of 14 allele differences (range 0–52) and consisted entirely of genotypes 4.3.1.1 and 4.3.1.2. Resistance determinants were identified exclusively in the predominant clade. Determinants associated with resistance to aminoglycosides were observed in 245 isolates (79.0%), sulphonamide in 243 isolates (78.4%), trimethoprim in 247 isolates (79.7%), tetracycline in 224 isolates (72.3%), chloramphenicol in 247 isolates (79.6%), β-lactams in 239 isolates (77.1%) and quinolones in 62 isolates (20.0%). Multidrug resistance (MDR) determinants (defined as determinants conferring resistance to ampicillin, chloramphenicol and cotrimoxazole) were found in 235 (75.8%) isolates. The prevalence of MDR associated genes was similar throughout the study period (2007–2012: 203, 76.3% vs 2013–2019: 32, 72.7%; Fisher’s Exact Test: P = 0.5478, while the proportion of isolates harboring quinolone resistance determinants increased (2007–2012: 42, 15.8% and 2013–2019: 20, 45.5%; Fisher’s Exact Test: P<0.0001) following a decline in S. Typhi in Kibera. Some isolates (49, 15.8%) harbored both MDR and quinolone resistance determinants. There were no determinants associated with resistance to cephalosporins or azithromycin detected among the isolates sequenced in this study. Plasmid markers were only identified in the main clade including IncHI1A and IncHI1B(R27) in 226 (72.9%) isolates, and IncQ1 in 238 (76.8%) isolates. Molecular clock analysis of global typhoid isolates and isolates from Kibera suggests that genotype 4.3.1 has been introduced multiple times in Kibera. Several genomes from Kibera formed a clade with genomes from Kenya, Malawi, South Africa, and Tanzania. The most recent common ancestor (MRCA) for these isolates was from around 1997. Another isolate from Kibera grouped with several isolates from Uganda, sharing a common ancestor from around 2009. In summary, S. Typhi in Kibera belong to four wgMLST clades one of which is frequently associated with MDR genes and this poses a challenge in treatment and control.

Typhoid fever is a major public health concern in endemic regions. Understanding the circulating strains of S. Typhi, could provide insight into the genomic epidemiology and guide in the choice of appropriate antibiotics. In this paper, our aim was to characterize S. Typhi strains causing invasive disease in Kibera, where a high typhoid burden has been described. We also aim to understand the evolutionary history of these strains and how antimicrobial resistance determinants have changed over time. We found that there was low diversity of S. Typhi observed in Kibera isolates with isolates grouping into 4 wgMLST clades and five genotypes. The majority (93.5%) of the isolates belonged to genotype 4.3.1; phylodynamic analysis suggest isolates of this genotype from Kibera are related to other 4.3.1 isolates from Africa and this genotype has been introduced multiple times in Kibera. This genotype in particular warrants close monitoring to inform antibiotic strategy in this population. Furthermore, concurrent detection of gene markers for MDR and quinolone resistance in some isolates raise concern about the potential emergence of extensive drug resistant (XDR) strains. Additional surveillance is needed in Kibera to monitor changing trends in resistance that may require altering clinical treatment, and to inform other preventive measures such as typhoid-conjugate vaccine introduction.

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.

Curcumin Analogues as a Potential Drug against Antibiotic Resistant Protein, β-Lactamases and L, D-Transpeptidases Involved in Toxin Secretion in Salmonella typhi: A Computational Approach

Typhoid fever caused by the bacteria Salmonella typhi gained resistance through multidrug-resistant S. typhi strains. One of the reasons behind β-lactam antibiotic resistance is -lactamase. L, D-Transpeptidases is responsible for typhoid fever as it is involved in toxin release that results in typhoid fever in humans. A molecular modeling study of these targeted proteins was carried out by various methods, such as homology modeling, active site prediction, prediction of disease-causing regions, and by analyzing the potential inhibitory activities of curcumin analogs by targeting these proteins to overcome the antibiotic resistance. The five potent drug candidate compounds were identified to be natural ligands that can inhibit those enzymes compared to controls in our research. The binding affinity of both the Go-Y032 and NSC-43319 were found against β-lactamase was −7.8 Kcal/mol in AutoDock, whereas, in SwissDock, the binding energy was −8.15 and −8.04 Kcal/mol, respectively. On the other hand, the Cyclovalone and NSC-43319 had an equal energy of −7.60 Kcal/mol in AutoDock, whereas −7.90 and −8.01 Kcal/mol in SwissDock against L, D-Transpeptidases. After the identification of proteins, the determination of primary and secondary structures, as well as the gene producing area and homology modeling, was accomplished. The screened drug candidates were further evaluated in ADMET, and pharmacological properties along with positive drug-likeness properties were observed for these ligand molecules. However, further in vitro and in vivo experiments are required to validate these in silico data to develop novel therapeutics against antibiotic resistance.

Trends of Antimicrobial Resistance in Typhoidal Strains of Salmonella in a Tertiary Care Hospital in Pakistan

INTRODUCTION

Enteric fever or typhoid fever is a major public health issue affecting greater than 27 million individuals globally and is responsible for greater than 200,000 deaths per year. Due to the extensive overuse of antimicrobials, the world is moving toward a pre-antibiotic era. The emergence and transmission of antibiotic-resistant Salmonella species are a global threat and a serious concern in developing countries such as Pakistan. This study aimed to determine the trends in antimicrobial resistance (AMR) of typhoidal strains of Salmonella in a tertiary care hospital in Pakistan.

MATERIALS AND METHODS

It was a descriptive, cross-sectional study conducted in the pathology department of Sharif City Hospital, Lahore, after approval by the ethical committee of the institution. A total of 50 blood culture specimens positive for Salmonella typhi and Salmonella paratyphi from January 2019 to March 2020 were included by the non-probability consecutive sampling technique. The samples were processed by conventional bacteriological methods for isolation and identification. The antimicrobial susceptibility testing was done by the Kirby-Bauer disc diffusion method as recommended by the Clinical and Laboratory Standard Institute (CLSI). The statistical package for social sciences (SPSS, IBM Corp., Armonk, NY) version 25 was used for data entry and analysis.

RESULTS

Among the first-line drugs (ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole), 70% of strains were resistant, and only 30% strains were sensitive to them. Among the cephalosporins, 52% strains were sensitive to ceftriaxone, and 48% strains were sensitive to ceftazidime, cefotaxime, and cefepime. Twenty-four percent of strains were sensitive to ciprofloxacin. Only 50% of strains were sensitive to ampicillin-sulbactam, and 92% of strains were sensitive to piperacillin-tazobactam. All the strains were 100% sensitive to imipenem and meropenem; 96% of strains were sensitive to co-amoxiclav, doxycycline, and azithromycin. The frequency of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Salmonella species was 16% and 54%.

CONCLUSION

The increasing frequency of MDR and XDR Salmonella species in Pakistan is a major concern. A significant percentage of the typhoidal strains of Salmonella is resistant to the first-line (16%) and second-line (54%) antibiotics. Carbapenems and azithromycin are the last resort of therapy in such cases.

Changes in antimicrobial resistance and molecular attributes of Salmonellae causing enteric fever in Kolkata, India, 2014-2018

Globally, enteric fever caused by Salmonella Typhi (S. Typhi, ST) and S. Paratyphi A (SPA) remain one of the major diseases of public health importance. In this study, a total of 457 (380 ST, 77 SPA) blood isolates were collected from three tertiary care hospitals in Kolkata during 2014-18. Additionally, 66 (3.4%) ST and 5 (0.25%) SPA were recovered from blood culture of 1962 patients attending OPD of one pediatric hospital during 2016-18. The study isolates were tested for antimicrobial resistance (AMR) profiles; AMR genes; molecular sub-types by PFGE, MLVA and CRISPR. Among the total 446 ST and 82 SPA isolates, fluoroquinolone (FQ) resistance was very common in both serovars. Ciprofloxacin resistance of 24.9% and 9.8% & ofloxacin resistance of 20.9% and 87.8% were found in ST and SPA respectively. Majority (>70%) of the isolates showed decreased susceptibility to ciprofloxacin (DCS). A single point mutation in gyrA gene (S83F) was responsible for causing DCS in 37.5% (n = 42/112) ST and 63% (n = 46/73) SPA isolates. Multidrug resistance (MDR) was found only in 3.4% ST isolates and encoded the genes bla_TEM-1, catA, sul, strA-strB, class 1 integron with dfrA7. All MDR ST (n = 15) possessed non-conjugative non-IncHI1 (180 kb) plasmid except one having conjugative IncHI1 (230 kb) plasmid and one without plasmid. The MDR genes were integrated near chromosomal cyaA gene site in ST with/without the presence of plasmid (nonIncH1). Almost 65.7% resistant ST belonged to H58 haplotype. PFGE showed clonally related isolates with 81% similarity in ST and 87% in SPA. Similarly, CRISPR typing showed less diversity among the isolates. However, the isolates (ST and SPA) were found to be more diverse by MLVA typing (D value 0.987 and 0.938). The study reports decrease in MDR and increase in FQ resistance among typhoidal Salmonella isolates over the years giving interesting information for enteric fever treatment.

Trends in bacterial resistance among perioperative infections in patients with primary ovarian cancer: A retrospective 20-year study at an affiliated hospital in South China

Background

We aimed to analyze the epidemiological and drug-resistance trends among bacterial cultures from perioperative infections in patients with primary ovarian cancer.

Methods

Medical and bacteriological records for patients with ovarian cancer patients who developed perioperative infections after primary cytoreductive surgery from 1999 to 2018 were reviewed retrospectively.

Results

The incidence of perioperative infections and the culture-positive percentage among patients in the first 10 years were 20.2% and 29.3%, respectively, and the equivalent rates in the second 10 years were 18.0% and 33.5%. The most commonly isolated pathogens in both year-groups were Escherichia coli and Enterococcus spp., but the respective percentages differed between the groups. Some strains of Staphylococcus aureus and Enterococcus spp. in the second 10-year group were resistant to linezolid and vancomycin, and ciprofloxacin resistance among Gram-negative bacteria isolates also increased in this group. However, resistance of Gram-negative bacteria to imipenem and meropenem was low among in both groups.

Conclusion

The pathogen distribution in perioperative infections in patients with primary ovarian cancer undergoing cytoreductive changed slightly from 1999 to 2018, and the antibiotic resistance of the main isolated pathogens increased. These results indicate the importance of periodic bacterial surveillance of surgical infections in these patients.

Estimating the burden of enteric fever in Chhattisgarh: A single-center study on culture-positive cases from a newly built tertiary care hospital

BACKGROUND

Enteric fever is the most common cause of community acquired blood stream infections in under developed and developing countries. The enteric fever is exclusive to humans and transmitted through the faeco-oral route. Though India is an endemic zone for enteric fever, the data is very scarce from Central India. The present study was undertaken to determine the prevalence of enteric fever in this region and to know the antimicrobial susceptibility pattern of the isolated typhoidal Salmonellae.

MATERIAL AND METHOD

We conducted a retrospective analysis of blood culture positive cases of enteric fever over a period of two years (December 2015 to December 2017). All blood cultures submitted for suspected enteric fever and associated symptoms were included in the study. Relevant demographic, clinical and laboratory data were analyzed.

RESULT

A total of 51 cases (3.56%) were of typhoidal Salmonella from a total of 1430 blood culture submission. Salmonella Typhi were 70.5% while Salmonella Paratyphi A were 29.5% of the total isolated Salmonellae. The most vulnerable age group was 10-19years (41.2%). The mean minimum inhibitory concentration of ciprofloxacin for Salmonella Typhi and Salmonella Paratyphi A are 1.20 and 1.97 μg/ml respectively. All the isolates were susceptible to ceftriaxone. Highest isolation was in the July - September quarter (35.3%).

CONCLUSION

There is a high prevalence of the disease which needs urgent focus on safe water, sanitation services and also to establish guidelines for empiric therapy for enteric fever.

Pediatric Blood Cultures and Antibiotic Resistance: An Overview

Bloodstream infections (BSI) due to multidrug-resistant organisms, especially from pediatric intensive care units (PICU), are being increasingly reported across the world. Since BSI is associated with high mortality, it is essential to treat these infections early with appropriate antibiotics. Surveillance of etiology and emerging antimicrobial resistance (AMR) is considered an important step in the formulation of antibiotic policy for early treatment and judicious use of antibiotics. In this review on etiology and its antibiogram in community acquired BSI, S. typhi followed by S. paratyphi A were the major bacterial isolates. Quinolone resistance of more than 90% in Salmonella is now reported from all over India. Ceftriaxone remains the drug of choice for enteric fever due to its 100% susceptibility. In PICU there is an emergence of candidemia due to non-albicans candida which are now predominant isolates at few centers. BSI due to gram-negative bacteria, mostly by Klebseilla pneumoniae and gram-positive cocci (S. aureus) are the other major pathogens commonly observed in BSI from PICU. There is a high prevalence of antimicrobial resistance to commonly used antibiotics like ampicillin (94.9%-90.7%), cefotaxime (92.4%-71.4%), piperacillin-tazobactum (31.2%-27.5%) and levofloxacin (42.4%-39.8%). Resistance to carbapenems, primarily due to bla_NDM is seen in all the centers and the rate varies between 1%- 79% with K. pneumoniae and A. baumannii showing the maximum resistance. This review highlights the magnitude of the AMR in the pediatric population and calls for the urgent implementation of antimicrobial stewardship programs to save the remaining antimicrobials.

Bacterial resistance trends among intraoperative bone culture of chronic osteomyelitis in an affiliated hospital of South China for twelve years

Background

The purpose of this study was to gather temporal trends on bacteria epidemiology and resistance of intraoperative bone culture from chronic ostemyelitis at an affiliated hospital in South China.

Method

Records of patients with chronic osteomyelitis from 2003 to 2014 were retrospectively reviewed. The medical data were extracted using a unified protocol. Antimicrobial susceptibility testing was carried out by means of a unified protocol using the Kirby-Bauer method, results were analyzed according to Clinical and Laboratory Standards Institute definitions.

Result

Four hundred eighteen cases met our inclusion criteria. For pathogen distribution, the top five strains were Staphylococcus aureus (27.9%); Pseudomonas aeruginosa (12.1%); Enterobacter cloacae (9.5%); Acinetobacter baumanii (9.0%) and Escherichia coli (7.8%). Bacterial culture positive rate was decreased significantly among different year-groups. Mutiple bacterial infection rate was 28.1%. One strain of Staphylococcus aureus was resistant to linezolid and vancomycin. Resistance of Pseudomonas aeruginosa stains to Cefazolin, Cefuroxime, Cefotaxime, and Cefoxitin were 100% nearly. Resistance of Acinetobacter baumanii stains against Cefazolin, Cefuroxime were 100%. Ciprofloxacin resistance among Escherichia coli isolates increased from 25 to 44.4%. On the contrary, resistance of Enterobacter cloacae stains to Cefotaxime and Ceftazidime were decreased from 83.3 to 36.4%.

Conclusions

From 2003 to 2014, positive rate of intraoperative bone culture of chronic osteomyelitis was decreased; the proportion of Staphylococcus aureus was decreased gradually, and our results indicate the importance of bacterial surveilance studies about chronic osteomyelitis.

Salmonella enterica Serovar Typhi in Bangladesh: Exploration of Genomic Diversity and Antimicrobial Resistance

Typhoid fever, caused by Salmonella enterica serovar Typhi, is a global public health concern due to increasing antimicrobial resistance (AMR). Characterization of S Typhi genomes for AMR and the evolution of different lineages, especially in countries where typhoid fever is endemic such as Bangladesh, will help public health professionals to better design and implement appropriate preventive measures. We studied whole-genome sequences (WGS) of 536 S Typhi isolates collected in Bangladesh during 1999 to 2013 and compared those sequences with data from a recent outbreak in Pakistan reported previously by E. J. Klemm, S. Shakoor, A. J. Page, F. N. Qamar, et al. (mBio 9:e00105-18, 2018, https://doi.org/10.1128/mBio.00105-18), and a laboratory surveillance in Nepal reported previously by C. D. Britto, Z. A. Dyson, S. Duchene, M. J. Carter, et al. [PLoS Negl. Trop. Dis. 12(4):e0006408, 2018, https://doi.org/10.1371/journal.pntd.0006408]. WGS had high sensitivity and specificity for prediction of ampicillin, chloramphenicol, co-trimoxazole, and ceftriaxone AMR phenotypes but needs further improvement for prediction of ciprofloxacin resistance. We detected a new local lineage of genotype 4.3.1 (named lineage Bd) which recently diverged into a sublineage (named Bdq) containing qnr genes associated with high-level ciprofloxacin resistance. We found a ceftriaxone-resistant isolate with the bla _CTX-M-15 gene and a genotype distinct from the genotypes of extensively drug-resistant (XDR) isolates from Pakistan. This result suggests a different source and geographical origin of AMR. Genotype 4.3.1 was dominant in all three countries but formed country-specific clusters in the maximum likelihood phylogenetic tree. Thus, multiple independent genetic events leading to ciprofloxacin and ceftriaxone resistance took place in these neighboring regions of Pakistan, Nepal, and Bangladesh. These independent mutational events may enhance the risk of global spread of these highly resistant clones. A short-term global intervention plan is urgently needed.IMPORTANCE Typhoid fever, caused by Salmonella enterica serovar Typhi, is responsible for an estimated burden of approximately 17 million new episodes per year worldwide. Adequate and timely antimicrobial treatment invariably cures typhoid fever. The increasing antimicrobial resistance (AMR) of S Typhi severely limits the treatment options. We studied whole-genome sequences (WGS) of 536 S Typhi isolates collected in Bangladesh between 1999 and 2013 and compared those sequences with data from a recent outbreak in Pakistan and a laboratory surveillance in Nepal. The analysis suggests that multiple ancestral origins of resistance against ciprofloxacin and ceftriaxone are present in three countries. Such independent genetic events and subsequent dissemination could enhance the risk of a rapid global spread of these highly resistant clones. Given the current treatment challenges, vaccination seems to be the most appropriate short-term intervention to reduce the disease burden of typhoid fever at a time of increasing AMR.