Serotype profile and molecular characterization of antimicrobial resistance in non-typhoidal Salmonella isolated from gastroenteritis cases over nine years

Drug Resistance, Characterization and Phylogenetic Discrepancy of Salmonella enterica Isolates from Distinct Sources

Salmonella enterica is one of the foodborne pathogens that can infect humans, spreading from one person to another by contaminated food and water. To identify the pathogenic S. enterica from the contaminated food product, culture-based and molecular identifications, drug resistance profiling, virulence and genetic traits of the strains have been used. Herein, different animal products was subjected to screen for S. enterica prevalence, pathogenic characterization and compared with clinical Salmonella isolates (human). A total of 173 isolates from animal products and 51 isolates from clinical samples were collected. S. Typhi, S. Agona and S. Ohio were predominant serovars in blood, stool and different animal products. Both, clinical [37% (n = 19/51)] and animal product-associated isolates [21% (n = 37/173)] expressed their highest resistance to nalidixic acid. Thirty-one percentage of (n = 16/51) clinical isolates and 12% (n = 21/173) animal food-associated isolates were resistant to multiple classes of antibiotics. Class 1 integrons encoded by S. Typhi, S. Infantis and S. Emek were screened for sequence analysis, the result revealed that the cassettes encoded-aminoglycoside acetyltransferase and dihydrofolate reductase enzymes. Salmonella pathogenicity island-1 encoded-hilA gene was detected most frequently in all the isolates. PFGE profile revealed the genetic traits of the isolates which were closely linked with antibiotic-resistant properties and virulent characteristics. Only S. Enteritidis, collected from different samples had clonal similarities. In summary, drug-resistant pathogenic Salmonella prevalence was observed in the animal product that could be an important alarm to consumers with the risk of enteric fever and it causes the potential risk to public health.

Non-typhoidal Salmonella infections across India: emergence of a neglected group of enteric pathogens

Objective

Non-typhoidal Salmonellae (NTS) are a neglected group of enteric pathogens whose prevalence is increasing at alarming rates across India. The disease burden is being underestimated because of a lack of effective surveillance of NTS infections in the Indian population. This study depicts the acquisition of NTS infection, and its persistence and spread through a diverse range of hosts, including humans and animals, and food and environmental sources.

Methods

During the study period from 2016 to 2018, a total of 999 suspected NTS isolates were received from across India and were phenotypically and serologically characterized for the presence of NTS.

Results

Of the 999 isolates, 539 (53.95%) were confirmed as NTS, consisting of 17 different NTS serovars. The majority were isolated from human samples (n = 319, 59.18%), followed by food products (n = 99, 18.37%), animals (n = 83, 15.4%) and the environment (n = 38, 7.05%). Some predominant serovars obtained included S. Typhimurium (n = 167, 30.98%), S. Lindenberg (n = 135, 25.05%), S. Enteritidis (n = 56, 10.39%), S. Weltevreden (n = 44, 8.16%), S. Choleraesuis (n = 41, 7.61%) and S. Mathura (n = 33, 6.12%).

Conclusion

This study depicts the NTS disease burden across India, on the basis of the isolation of NTS serovars across diverse geographic locations. The emergence of newer or less common NTS serovars implicated in human infection poses a potential challenge to the healthcare system in India. Therefore, national and regional level surveillance is needed to implement effective control strategies and safeguard community health in India.

A nineteen-year report of serotype and antimicrobial susceptibility of enteric non-typhoidal Salmonella from humans in Southern India: changing facades of taxonomy and resistance trend

BACKGROUND

The steady increase in the proportion of Non-typhoidal Salmonella (NTS) infections in humans represents a major health problem worldwide. The current study investigated the serovar distribution and antimicrobial susceptibility trends of NTS isolated from faecal samples during the period 2000-2018.

METHODS

Faecal specimens of patients were cultured according to standard lab protocol. The isolates were serotyped and antimicrobial susceptibility testing (AST) were performed according to CLSI guidelines.

RESULTS

A total of 1436 NTS isolates were obtained from faeces samples mostly comprising of S. Typhimurium (27.3%), S. Weltevreden (13%), S. Bareilly (11%), S. Newport (4.2%), S. Cholerasuis (4%), S. Infantis (3.4%), and S. Enteritidis (2.4%). Resistance to nalidixic acid (26%) was most common among the tested NTS, followed by ampicillin (18.5%), cotrimoxazole (13.5%), ciprofloxacin (12%), ceftriaxone (6.3%) and chloramphenicol (3.6%). Multidrug resistance was observed in 5% of NTS isolates with the highest rate (10.52%) in 2014. The incidence of NTS infection was maximum in children < 5 years of age with an average 19.3% of the total affected patients during the time period.

CONCLUSIONS

Based on this study, the faecal NTS isolates have high resistance rates against first line antimicrobial agents except chloramphenicol. The gradual but consistent increase in resistance to fluoroquinolones, third generation cephalosporins and macrolide may restrict future treatment options. Hence periodic monitoring of NTS infections, serotype distribution and antimicrobial resistance trend is recommended.

Effect of bile on growth and biofilm formation of non-typhoidal salmonella serovars isolated from seafood and poultry

Bacterial cells adopt various strategies to adapt themselves in diverse environmental conditions. Salmonella is one such bacteria with diverse mechanisms to survive, replicate and infect in wide host range. This study aims at investigating the biofilm-forming ability of multidrug-resistant and sensitive Salmonella serovars on exposure to bile. Antibiogram of all the isolates was determined by disk diffusion method and their biofilm-forming ability in the presence or absence of bile was assessed by microtiter plate assay. Biofilm results were validated by calcofluor, Congo red plate and test tube method. Few isolates were selected for further study of their expression of biofilm related genes on exposure to bile using real time PCR. Among the 59 isolates of Salmonella isolated from seafood and poultry, 30 isolates were multi-drug resistant (MDR). Under control conditions, 57% (n = 25) of the serovars were able to form biofilm. While, 86% (n = 51) of the serovars produced biofilm in the presence of bile. The relative gene expression study of the selected serovars for 8 different genes showed a striking difference in the expression levels, supporting the hypothesis that the presence of bile triggers biofilm formation in food associated strains of non-typhoidal Salmonella by upregulation of genes involved in biofilm production.

Characterization of non-typhoidal Salmonella isolates from children with acute gastroenteritis, Kolkata, India, during 2000-2016

Non-typhoidal Salmonella (NTS) is an important cause of acute gastroenteritis in children. The study was undertaken to determine the isolation rate, serovar prevalence, antimicrobial resistance (AMR) profiles, and molecular subtypes of NTS from a hospital-based diarrheal disease surveillance in Kolkata, India. Rectal swabs were collected from children (< 5 years of age) with acute gastroenteritis from 2000 to 2016. Samples were processed following standard procedures for identification of NTS. The isolates were tested for antimicrobial susceptibility, AMR genes, plasmid profiles, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE) subtypes. A total of 99 (1.0%) Salmonella isolates were recovered from 9957 samples processed. Of the 17 Salmonella serovars identified, S. Worthington (33%) was predominant followed by S. Enteritidis (13%), S. Typhimurium (12%), and others. The isolates showed high resistance towards nalidixic acid (43%), ampicillin (34%), third-generation cephalosporins (32%), and azithromycin (25%), while low resistance was observed for fluoroquinolones (2%). Extended-spectrum beta-lactamase production (bla_CTX-M-15 and bla_SHV-12 genes) and azithromycin resistance (mphA gene) were common in S. Worthington, while fluoroquinolone resistance (gyrA and parC mutations) was found in S. Kentucky. Diverse plasmid profiles were observed among the isolates. PFGE analysis identified genetically related strains of each serovar in circulation. MLST also revealed phylogenetically clonal isolates of which S. Worthington ST592 and ciprofloxacin-resistant S. Kentucky ST198 were not reported earlier from India. NTS resistant to current drugs of choice poses a potential public health problem. Continuous monitoring of AMR profiles and molecular subtypes of NTS serovars is recommended for controlling the spread of resistant organisms.

Antimicrobial susceptibility profile & resistance mechanisms of Global Antimicrobial Resistance Surveillance System (GLASS) priority pathogens from India

Antimicrobial resistance is a major concern globally. Infections due to drug-resistant pathogens are becoming difficult and a challenge to treat. As treatment choices are limited due to the high-drug resistance rates, there is an increase in the health care cost, duration of hospital stay, morbidity and mortality rates. Understanding the true burden of antimicrobial resistance for a geographical location is important to guide effective empirical therapy. To have a national data, it is imperative to have a systemic data capturing across the country through surveillance studies. Very few surveillance studies have been conducted in India to generate national data on antimicrobial resistance. This review aims to report the cumulative antibiogram and the resistance mechanisms of Global Antimicrobial Resistance Surveillance System (GLASS) priority pathogens from India.

Prevalence of Multidrug Resistant Salmonellae with Increasing Frequency of Salmonella enterica Serovars Kentucky and Virchow among Hospitalized Diarrheal Cases in and around Delhi, India

Non-typhoidal salmonellae (NTS) are a major cause of acute diarrhea with characteristic multidrug resistance (MDR). In a hospital-based study, 81 NTS were isolated and tested for serotypes and antimicrobial resistance (AMR). Salmonella enterica isolates were classified into 7 different typable serovars, however, 19 (23%) isolates remained untypable. The most common serovars were S. Kentucky (48%), and S. Virchow (22%). Most of the NTS isolates displayed resistance to nalidixic acid (NA) (73%), ciprofloxacin (CIP) (48%), ampicillin (AM) and norfloxacin (NOR) (36% each), and gentamicin (CN) (31%). The AMR profiles for CN and NA; and AM, CIP, NA and NOR, were found to be high in S. Virchow (83%) and S. Kentucky (43%), respectively. Analysis of the pulsed-field gel electrophoresis patterns of S. Kentucky revealed 3 clusters. S. Kentucky has clones closely related to become prominent in recent years in Delhi. The AMR appears to be consistent with the change in MDR patterns during 2014-2017. The observed prevalence of S. Kentucky and S. Virchow in large numbers of diarrheal cases is novel. The NTS are mostly resistant to fluoroquinolones, which is the current drug of choice for treating diarrheal cases. MDR is very common among clonally related S. Kentucky.

Endemic fluoroquinolone-resistant Salmonellaenterica serovar Kentucky ST198 in northern India

Salmonellaenterica serovar Kentucky is an emergent human pathogen. Human infection with ciprofloxacin-resistant S. enterica Kentucky ST198 has been reported in Europe and North America as a consequence of travel to Asia/the Middle East. This is, to the best of our knowledge, the first study reporting the identification of this epidemic clone in India and South Asia.

An emerging threat of ceftriaxone-resistant non-typhoidal salmonella in South India: Incidence and molecular profile

Background

Non-typhoidal Salmonella (NTS) infection is a serious public health problem globally. Although NTS infections are self-limited, antimicrobial therapy is recommended for severe infections and immunocompromised patients. Antimicrobial resistance (AMR) in these pathogens further limits its therapeutic options. Here, we report an incidence of ceftriaxone resistance in NTS over the past 9 years in a southern Indian region.

Materials and Methods

Molecular mechanisms of resistance in ceftriaxone-resistant NTS have been tested by both phenotypic and molecular methods. Minimum inhibitory concentration was determined by the E-test and broth microdilution method. AMR gene markers of β-lactamases such as AmpCs (blaMOX, blaCMY, blaDHA, blaFOX, blaACC and blaACT) and extended-spectrum β-lactamases (ESBLs) (blaSHV, blaTEM, blaVEB, blaPER, blaCTXM-1like,blaCTXM-2like, blaCTXM-8like, blaCTXM-9like and blaCTXM-25like) were screened. The presence of IncH12 and IncI1 plasmid was also analysed.

Results

The study reports a 5% prevalence of ceftriaxone resistance in NTS. The most common serogroup was Salmonella Group B followed by Salmonella Group E and Salmonella group C1/C2. The occurrence of blaCTX-M-1, blaTEM, blaCMY and blaSHV genes was observed in 54%, 54%, 48% and 3% of the isolates, respectively. Interestingly, few isolates carried dual resistance genes (ESBLs and AmpCs). IncH12 and IncI1 plasmid was identified in isolates carrying ESBL and AmpC genes, respectively.

Conclusion

This study shows that ceftriaxone resistance is mainly mediated by β-lactamases such as ESBL and AmpC. As the incidence of ceftriaxone resistance is rising gradually over the years, it is imperative to monitor the AMR in this species.

Antimicrobial resistance, plasmid, virulence, multilocus sequence typing and pulsed-field gel electrophoresis profiles of Salmonella enterica serovar Typhimurium clinical and environmental isolates from India

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common serovar associated with non-typhoidal salmonellosis globally. However, there is insufficient data on molecular characterization of S. Typhimurium isolates from India. This study was undertaken to determine the antimicrobial resistance (AMR), plasmid, virulence profiles and molecular subtypes of S. Typhimurium Indian isolates (n = 70) of clinical and environmental origin isolated during 2010–2017. Antimicrobial susceptibility and minimum inhibitory concentrations were determined by disc diffusion and E-test methods respectively. Plasmid extraction was done following standard protocol. AMR genes, virulence genes and plasmid incompatibility types were detected by PCR; Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were used for molecular subtyping. Majority (57%) of the study isolates was pan susceptible; five AMR profiles were observed among the resistant (43%) isolates. AMR was significantly (p = 0.004) associated with extra-intestinal isolates than intestinal isolates.The class 1 integron and plasmid-mediated quinolone resistance genes (qnrB1, qnrS1) in the resistant isolates were transferable by conjugation. Plasmids (≥1) ranging from 1.9 to 254kb size and of IncFIIS and/or FIB type were found in most isolates. A total of 39 pulsotypes by PFGE and four sequence types by MLST like ST36 (55.7%), ST19 (32.9%), ST313 (10%) and ST213 (1.4%) were observed. ST36 and ST19 were found circulating in both clinical and environmental host, while ST313 isolates had an exclusive clinical origin. All ST19 isolates (100%) were drug-resistant, while isolates belonging to ST313 (100%), ST213 (100%) and ST36 (82%) were pan susceptible. The virulence plasmid (VP) genes (spvB- spvC) were present in all genotypes except ST36. The VP was significantly (p<0.001) associated with extra-intestinal than intestinal isolates. Some environmental and clinical isolates were clonal indicating their zoonotic transmission. Knowledge on the molecular subtypes and AMR profiles of locally prevalent Salmonella serotypes is important for effective control of spread of resistant organisms. The MLST of S. Typhimurium isolates and its association with AMR, virulence profiles was not reported earlier from India.

Clinical features of children with nontyphoidal Salmonella bacteremia: A single institution survey in rural Japan

Nontyphoidal Salmonella (NTS) can cause bacterial enterocolitis. Although some children with NTS infection develop bacteremia, its clinical manifestations have not been discussed adequately. Therefore, we examined children with NTS bacteremia. We retrospectively examined the medical records of 15 patients aged less than 15 years. Salmonella spp. were detected in the blood cultures of these patients between 1991 and 2014. We divided an additional sample group of 34 patients diagnosed with an NTS infection between 2005 and 2014, into 2 groups. Group bacteremia (B) included patients in whose blood cultures Salmonella spp. were detected, and group non-bacteremia (NB) included patients in whom Salmonella infection was not detected. We compared each group using Wilcoxon test and Fisher’s exact test. The number of patients with fever, diarrhea, or abdominal pain was 15 (100%), 13 (87%), and 9 (60%), respectively, in the first sample of patients. However, vomiting and bloody stool were observed in only 5 patients (33%). More than 70% of patients exhibited a reduced white blood cell count, while C-reactive protein levels were variable in the patients. Salmonella spp. were detected via stool culture in 10 patients (67%). Diarrhea persisted for more than 4 days more frequently in group B than group NB (p = 0.004). The number of patients whose fever persisted for more than 4 days was significantly higher in group B than group NB (p = 0.030). Therefore, if NTS bacteremia is suspected, blood cultures should be collected and antibiotics should be initiated in cases with diarrhea or fever for more than 4 days. Furthermore, a negative stool culture result does not preclude the possibility of NTS bacteremia.

Salmonella Serogroup C: Current Status of Vaccines and Why They Are Needed

Nontyphoidal Salmonella (NTS; i.e., Salmonella enterica organisms that do not cause typhoid or paratyphoid) are responsible for 94 million infections and 155,000 deaths worldwide annually, 86% of which are estimated to be foodborne. Although more than 50 serogroups and 2,600 serovars have been described, not all Salmonella serovars cause disease in humans and animals. Efforts are being made to develop NTS vaccines, with most approaches eliciting protection against serovars Typhimurium and Enteritidis (serogroups B [O:4] and D [O:9], respectively), as they are widely considered the most prevalent. Here, we show that serogroup C (O:6,7, O:6,8, or O:8 epitopes) is the most common serogroup in the United States, and the prevalence of serovars from this serogroup has been increasing in Europe and the United States over the last decade. They are also the most commonly isolated serovars from healthy cattle and poultry, indicating the underlying importance of surveillance in animals. Four out of the 10 most lethal serovars in the United States are serogroup C, and reports from African countries suggest that strains within this serogroup are highly antibiotic resistant. Serogroup C consists of highly diverse organisms among which 37 serovars account for the majority of human cases, compared to 17 and 11 serovars for serogroups B and D, respectively. Despite these concerning data, no human vaccines targeting serogroup C NTS are available, and animal vaccines are in limited use. Here, we describe the underestimated burden represented by serogroup C NTS, as well as a discussion of vaccines that target these pathogens.

Emergence and serovar profiling of non-typhoidal Salmonellae (NTS) isolated from gastroenteritis cases-A study from South India

Human infection with non-typhoidal Salmonella (NTS) serovars is often a neglected and undiagnosed infection in the developing world. Invasive NTS is now being established as having a new and emerging pathogenic role. There is not sufficient data on the prevalence of NTS serovars and their antibiotic susceptibility pattern from India. Faecal specimens collected from patients with acute gastroenteritis were processed to isolate Salmonella according to the standard protocol for a period from January 2011-December 2014. Salmonella isolates were serotyped and tested for antibiotic susceptibility. Of the total 320 (10.04%) bacterial enteric pathogens isolated, 64 (20%) were non-typhoidal Salmonella. Among the serogroup, O:4 (B) (n = 26; 40.6%) was found to be the commonest followed by O:7 (C1) (n = 11; 17.1%) and O:3,10 (E1) (n = 11; 17.1%). NTS infection in cancer patients could also be termed as nosocomial NTS diarrhoea due to primary community infection with prolonged incubation periods, consumption of contaminated food during hospital stay or Nosocomially acquired infection. Serovar Oslo has been predominant (9/17) in NTS isolates from cancer patients, whereas serovars Bovismorbificans, Wangata and Schleissheim have been reported for the first time in the country. The isolates were mostly susceptible to antibiotics except Salmonella ser Kentucky, which showed resistance to ciprofloxacin is reported for the first time in the country. Continuous surveillance is required to monitor resistance of NTS isolates.