Salmonella Isolates Research Articles

Recent trends of drug susceptibility of salmonella isolates in tertiary health care hospital at Patna Bihar

Recent trends of drug susceptibility of salmonella isolates in tertiary health care hospital at Patna Bihar

Isolation and Antimicrobial Drug Susceptibility Profiling of Salmonella isolates from Raw Milk

The present study was conducted to determine the prevalence of Salmonella spp. in milk. The samples were collected from two intermediaries viz. farms (n=50) and retail shops (n=50) and antimicrobial susceptibility of the isolates were performed. The overall prevalence of Salmonella isolates at dairy farm was recorded as 28% amongst which 50% were S. typhi. Further, results revealed that eight dairy farms (80%) were positive, while two farms (20%) were detected as negative for Salmonella. The maximum prevalence was noted in Farm 7 (100%) whereas; milk samples from Farm 2 and Farm 10 were free from Salmonella contamination .None of the dairy shops found free of Salmonella carriage. The overall prevalence of salmonella was recorded as 44%. Among the salmonella isolates the prevalence of S.typhi was 54%. The maximum prevalence (60%) of Salmonella spp. in milk was noted in samples from five shops i.e. Shop 2, 4, 5, 9 and 10. More so, S. typhi was detected in 70% of milk samples from all seven shops except Shop 3, 6 and 9 which showed maximum carriage as 100%. Whereas, samples from three shops viz. Shop 1, 2 and 7 were free of S. typhi contamination. The organisms were found highly resistant to Neomycin and Kanamycin (84.21%) followed by Oxytetracycline (78.95%), Tetracycline (73.68%), Gentamycin (68.42%), Cefixime (52.63%), Cefoxitin (47.37%), Ciprofloxacin (36.84%) and Cefipime (32.11%). The overall MDR profile showed 68.4% S. typhi isolates were resistance to three and/or above antibiotics. A total of 26.31%, 21.04%, 15.78 and 5.26%, S.typhi showed resistance against three, four, five and six antimicrobial agents, respectively.

Screening for Antimicrobial Resistance in some Pathogens isolated from Cold Smoked Fish Marketed in Menofiya Government

The objective of this study was to demonstrate the prevalence and antibiotic resistance characteristics of Salmonella species, E. coli and listeria species were isolated conventionally from ninety cold smoked fish (Herring, Clupea), from souk and markets in Menofiya province, Egypt. The Coliform Count was significantly higher (P <0 .05) in souk than markets with mean counts of 4.07± 0.23 and 3.13± 0.40 Log CFU/gm. The overall prevalence of Salmonella sp. was 2.2% (2/90), and all of them were detected from a souk samples, while E. coli isolates were 13.3% (12/90), but, Listeria spp. failed to be detected in tested samples. Conventionally, Salmonella spp. were phenotypically resistant to three, Cefozon, E-Moxclave, and Clindamycin, of 8 commonly used antibiotics in Egypt. Whilst, E.coli strain showed resistance to Cefozon, Gentamicin, Cefotaxime, Doxycycline, E-Moxclave, and Clindamycin. A multi-resistance was observed in one Salmonella strain, and in 83.3% (5/6) of tested E. coli strain. Further, the molecular results showed that all isolated salmonella (n=2) and E. coli (n=6) strains contained the beta-lactam resistance genes, blaTEM detected in the 8 isolates (100%). On the other hand, one of two salmonella isolates and two of six E. coli strain were positive for erm(B) (erythromycin ribosome methylase) genes. This study may be the first report on antimicrobial resistant Salmonella species, Escherichia coli and listeria species in cold smoked fish (Herring, Clupea) marketed in Egypt.

Prevalence and antibiogram of non-typhoidal salmonella isolates from poultry in Ilorin, Kwara State

Prevalence and antibiogram of non-typhoidal salmonella isolates from poultry in Ilorin, Kwara State

First description of plasmid mediated quinolone resistance genes in salmonella isolates from Saudi hospitals.

Objectives:To detect resistance genes to fluoroquinolones and β-lactams in Salmonella strains from a Saudi hospital.Methods:From October 2015 to December 2016, a total of 149 Salmonella strains were collected from stool specimens from patients admitted to King Fahad Hospital of the University, AlKhobar, Saudi Arabia using CHROMagar Salmonella. The organism identification and antimicrobial susceptibility testing were performed using Vitek 2 system. Strain serogrouping was performed using Wellcolex color Salmonella kit. Fluoroquinolone resistance genes, extended-spectrum β-lactamases (ESBLs), and AmpC β-lactamase were determined using polymerase chain reaction (PCR). Enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) was used to determine clonal relatedness.Results:The resistance rates to cefotaxime were 1.3% and ciprofloxacin 19.5%. Plasmid mediated quinolone resistance (PMQR) genes, qnrB and qnrS, were detected in 8 strains, qnrB (n=5) and qnrS (n=3), respectively. No ESBLs, AmpC, or mutations in the topoisomerases were detected. Salmonella isolates formed 7 clusters with similarity.Conclusions:This study reveals the emergence of fluoroquinolone resistant Salmonella in the region imposing public health concerns.

Comparison between Different Methods for Detection of Salmonella Species in Imported and Local Duckling

Two hundred freshly dead and apparently healthy ducklings from 160 imported and 40 local species (Muller, pekin, Muscovy and Baladi) were bacteriologically examined for isolation and identification of Salmonella species. Only10 samples were positive with prevalence 5% in all collected samples. These isolates were further characterized by polymerase chain reaction. The result revealed 10 different servore as following S.Jedburgh,S.Harrisonburg, S.Braenderup , S.Southbank, S.SekondiII, .Sinchew, S.Brandenburg from imported duckling and S.Ruzizi, S. Give and S.Entertidis from local duckling with 0.5% for each. Salmonella isolates were tested for antimicrobial sensitivity and the most resistance rate was for trimethoprim with 80%, intermediate resistance for Penicillin, amoxicillin with 40 % and100% sensitive for norfloxacin. Based on PCR, all examined salmonella were positive100 %( 7/7) for stn virulence gene, while 42.85% (3/7) of the tested salmonella isolates were positive to aadB antibiotic resistance gene.

INFLUENCE OF AMLODIPINE ON RESISTANCE TO ENROFLOXACINE IN SALMONELLA ENTERICA

In recent years, there has been an increase in the number of strains of salmonellae resistant to antibiotics of fl uoroquinolone series. The occurrence of Salmonella resistant to enrofl oxacin was assessed at poultry farms of the Russian Federation in 2007 and 2017. In 2007 sensitivity of 23 salmonella cultures to enrofl oxacin was studied and in 2017 the same study was done with 15 salmonella cultures isolated from agricultural birds. Antibiotic resistance was determined by the disc-diffusion method in compliance with the generally accepted requirements. From 2007 to 2017 the frequency of salmonella isolation resistant to enrofl oxacin increased from 0 to 23.08%. Evaluation of the effl ux (active removal of antimicrobial substances by a bacterial cell) was carried out using a classical test with ethidium bromide. It was established that the presence of effl ux in Salmonella cultures was associated with an insignifi cant increase in resistance to enrofl oxacin, trimethoprim with sulfamethoxazole and trimethoprim with sulfadimezine. The effect of amlodipine on the sensitivity of salmonella to enrofl oxacin was evaluated by cultivation of Salmonella in the presence of various concentrations of amlodipine. It was revealed that the specifi c proportion of strains of salmonella with higher sensitivity to enrofl oxacin increased with the simultaneous rise in concentrations of amlodipine (Pearson correlation, r = 0.9). Administration of amlodipine in concentration of 250 μg/ml to Salmonella enterica cultures, in the presence of subinhibitory concentrations of enrofl oxacin, increased their sensitivity to enrofl oxacin in 87.5% of cases.

Resistance test of avian salmonella strains in antibacterial drugs

In the present paper in vitro resistance of 241 salmonella isolates to 9 antibacterial drugs was studied. Salmonella strains were isolated from various avian species during the period 1990-1994. The resistance of these isolates was determined by using the Kirbi Bauer disc diffusion method. Resistance to Oxytetracycline, furazolidone and trimethoprim ranged from 6 to 50% and the highest percentage (50%) was noted to Oxytetracycline. Resistance to spectinomycin reached the highest levels (56-80%). Similar results were noted by using amoxicillin, to which resistance was relateively lower ( — 50%) with a slight decrease to 15% concerning the year 1992 isolates. Resistance to enrofloxaxin and flumequin was at 25% approximately, only for strains isolated during 1991 and 1992. All remaining isolates were sensitive. Low resistance (11%) declining to 3% during the last year of our investigation was noted when neomycin was used. Finally, resistance to chloramphenicol remained below 10%.

Salmonella infection in clinically healthy dogs in Makurdi, Benue State, North-central Nigeria: A potential source of infection to humans.

Objective:The present study was initiated to ascertain the level of shedding of salmonellae by dogs in Makurdi area and to highlight the risk of infection for dog-owners.Materials and Methods:Rectal swabs from 200 dogs from different locations in the study area were examined in the study. The samples were cultured for salmonellae using Rappaport-Vassiliadis enrichment broth (Oxoid) and brilliant green agar (Oxoid). Suspected Salmonella isolates were serologically identified.Results:Overall, Salmonellae organisms were isolated from 11 (5.5%) of the 200 dogs sampled. Prevalence rates of 5.6% and 4.5% were recorded for apparently healthy and clinically sick dogs, respectively. Salmonella was respectively isolated from 4.1% to 9.1% of male and female dogs. Dogs aged 4 years and above recorded the highest prevalence rate. The study revealed a low prevalence rate in Nigerian local breed (mongrels) and high prevalence rates in exotic breeds of dogs.Conclusion:The isolation of salmonellae in apparently healthy and clinically sick dogs in this study indicates a carrier status which may constitute a serious problem in disease control in the study area. The lower prevalence rate of Salmonella infection in mongrels could be an indication of resistance to Salmonella in local breeds of dogs and should generate interest in research in the pathogenicity and pathogenesis of salmonellae in mongrels.

Prevalence of infection of broiler chickens with motile salmonellae

The results of a five-year epidemiological survey for the evaluation of motile salmonella infection in broiler chickens are reported in the present study. Three to four-week-old birds from 184 flocks, raised in several areas of Northern Greece, were examined bacteriologically. Fifty-five out of the 184 flocks were asymptomatic and the birds were presented for preventive examination, whereas the rest 129 flocks suffered from various diseases. Bacteriological examination of caecal contents from at least ten birds of each flock was performed. Samples from the viscera were also examined bacteriologically. Clinical signs and lesions - when present – were correlated with the isolation of salmonella in the flock. According to the results of this survey, 5.9-20% of the flocks were infected. Higher incidence was noticed in other European countries. Furthermore, no considerable difference in the incidence of infection between asymptomatic and diseased flocks was observed. In conclusion, salmonellae were more easily isolated from the caecal contents than from the viscera.

Interaction of Antibiotics with Innate Host Defense Factors against Salmonella enterica Serotype Newport.

This study examines the pharmacodynamics of antimicrobials that are used to treat Salmonella with each other and with key components of the innate immune system. Antimicrobial synergy was assessed using time-kill and checkerboard assays. Antimicrobial interactions with innate immunity were studied by employing cathelicidin LL-37, whole-blood, and neutrophil killing assays. Ceftriaxone and ciprofloxacin were found to be synergistic in vitro against Salmonella enterica serotype Newport. Ceftriaxone, ciprofloxacin, and azithromycin each demonstrated synergy with the human cathelicidin defense peptide LL-37 in killing Salmonella. Exposure of Salmonella to sub-MICs of ceftriaxone resulted in enhanced susceptibility to LL-37, whole blood, and neutrophil killing. The activity of antibiotics in vivo against Salmonella may be underestimated in bacteriologic media lacking components of innate immunity. The pharmacodynamic interactions of antibiotics used to treat Salmonella with each other and with components of innate immunity warrant further study in light of recent findings showing in vivo selection of antimicrobial resistance by single agents in this pathogen. IMPORTANCE It is becoming increasingly understood that the current paradigms of in vitro antimicrobial susceptibility testing may have significant shortcomings in predicting activity in vivo. This study evaluated the activity of several antibiotics alone and in combination against clinical isolates of Salmonella enterica serotype Newport (meningitis case) utilizing both conventional and physiological media. In addition, the interactions of these antibiotics with components of the innate immune system were evaluated. Azithromycin, which has performed quite well clinically despite high MICs in conventional media, was shown to be more active in physiological media and to enhance innate immune system killing. Alternatively, chloramphenicol did not show enhanced immune system killing, paralleling its inferior clinical performance to other antibiotics that have been used to treat Salmonella meningitis. These findings are important additions to the building understanding of current in vitro antimicrobial assay limitations that hopefully will amount to future improvements in these assays to better predict clinical efficacy and activity in vivo.

Microbiological evaluation of some frozen and salted fish products in Egyptian markets

Sixty random samples of fish and fish products (frozen fish: Tilapia nilotica and imported basa fillet– salted fish: Mugil cephalus and sardine) (15 of each) were collected from different supermarketsin Egypt. All collected samples were microbiologically examined for determination of AerobicPlate Count (APC), coliforms, Escherichia coli, Mould & yeast and Staphylococcal aureuscounts (log10 cfu/g). Isolation and identification of salmonella, liesteria monocytogenes and Vibrioparahaemoliticus. The bacteriological examination revealed that the mean values of APC in theexamined fish samples were 4.80± 0.16, 4.63±0.18, 2.35±0.18 and 2.70±0.13 (log10 cfu/g) forfrozen Tilapia nilotica, Basa salted Mugil cephalus and Sardine respectively, 1.48± 0.22, 2.19±0.19,2.10±0.16 and 2.52±0.11 average coliform counts in examined samples respectively, and E.colicount with an average of 2.52±0.14, 2.01±0.17, 1.31±0.11and 1.64±0.14. Mould & yeast averagecounts were 0.93±0.18, 1.22±0.16, 1.67±0.021 and 1.69±0.18 in examined fish samples,respectively, and the Staphylococcal counts were 1.30±0.17, 1.58±0.26, 2.12±0.14, 1.46±0.23 and2.17±0.17 in examined fish samples, respectively. The incidence of food poisoning organisms(Salmonella & Listeria monocytogenes and Vibrio parahaemolyticus also was investigated and oneof both Listeria monocytogenes and Vibrio parahaemolyticus were isolated in frozen Basa filletsamples with a percentage of 33% and 33% from the examined samples.

STUDY ON SOME ENTEROPATHOGENS OF STREET VENDED MEAT MEALS

Sixty random samples of street vended meat meals including 20 samples each of Shawerma, Liver sandwich and Hawawshi were randomly collected from different street vendors at Damanhur city Elbehaira Governorate for chemical and microbiological evaluation. The results revealed that, the mean values of total volatile nitrogen (TVB-N), Thiobarbituric acid (TBA) and Aerobic Plate count (APC) were 27.8±0.48, 25.8±0.17, 27.6±0.41 mg/100gm; 0.71±0.02, 4.2±0.33, 0.73±0.01mgMD/kg and 7.5x104±0.85x104, 4.8x104±0.50x104, 4.5x104±0.48 x104cfu/g in the examined samples of Shawerma, liver sandwich and Hawawshi, respectively. Also, enterococci, enteropathogenic E.coli, Salmonella and Shigella were isolated with an incidence of 25, 20, 25 %; 30, 20, 25 %; 10, 15, 0 % and 15, 10,10% from the examined samples of Shawerma, liver sandwich and Hawawshi, respectively. Serotyping of the obtained isolates of enteropathogenic E. coli revealed the detection of O157: H7, O128: K67, O86: K61, O26: K60 and O26: K72 strains at varying rates, Stereotyping Salmonella isolates revealed the detection of S. Enteritidis, S. Typhi and S. Paratyphi. In addition to, biochemical identification of the obtained Shigella isolates revealed the detection of S. dysenteriae, S. flexneri and S. sonnei. Two strain of isolated E.coliO157:H7 and one salmonella isolates were investigated by using PCR to detect presence of virulent genes stx1 (614 bp) and stx2 (779 bp) in E.coli O157:H7 and stn. Gene (617 bp) in Salmonella. From previously mentioned results, enteric pathogens still constitute common contaminants of street vended meat meals and their presence was very important due to its public health significance therefore strict hygienic measures must be applied to obtain safe and wholesome street vended meat meals.

Phenotypic and Genotypic Characterization of Paratyphoid Salmonellae isolated from Poultry in Delta Area- Egypt

The present work aimed to isolate and characterize Salmonellae from chickens, ducks, quails and turkeys in five Egyptian Governorates. Polymerase chain reaction (PCR) was used for the detection of common virulence genes. A total of 265 flock samples (150 chickens, 60 ducks, 30 quails and 25 turkeys) were collected from Dakahlia, Kafrelsheik, Damietta, Sharkia and Gharbia Governorates. Birds were subjected to either clinical and/or post-mortem examination, in adittion to isolation and identification of salmonellae from internal organs including liver, lung, spleen, caecum and unabsorbed yolk sac. Biochmeical and serological identification of the isolates was done. Twenty eight birds (10.6%) were found positive for Salmonella isolation. The number and percentage of positive chickens, ducks, quails and turkeys were 16 (10.7%), 7 (11.7%), 3 (10%) and 2 (8%), respectively. Salmonella Typhimurium, S. Enteritidis, S. Kentucky, S. Paratyphi A, S. Molade, S. Heidelberg, S. Infantis and S. Apeyeme were isolated from chickens. While S. Enteritidis, S. Typhimurium, S. Paratyphi A, S. Kentucky, S. Inganda and S. Bargny were isolated from ducks. While, S. Virchow, S. Tamale and S. Typhimurium were isolated from Quails and S. Wingrove, finally, S. Kentucky were isolated from turkeys. Molecular characterization of common virulence genes Salmonella outer proteins (sopB), Plasmid encoded virulence gene (spvC), salmonella enterotoxin (stn) and bacterial colonization factor (bcfC) showed the presence of stn and bcfC genes in all isolates, while, sopB and Spv genes were present in 64.3% and 10.7%, respectively. It is concluded that salmonellae with common virulence genes were widely spread among domestic birds in Delta areas, Egypt, resulting in economic and public health problems which require the application of strictly biosecurity measures in poultry rearing.

Azithromycin: Is it a favorable alternative therapeutic option against salmonella species ?

Background: For decades chloramphenicol has been highly effective against S. typhi and S.paratyphyi . However the known hematological side effects of chloramphenicol and the widespread emergence of multiple drug resistance (MDR) to S. typhi has necessitated the search for other therapeutic options .Aim of study: To compare between azithromycin and chloramphenicol as antimicrobial drugs for isolated salmonella speciesMaterials and Methods: 65 isolates of salmonella spp. was collected by performing blood culture and stool culture for suspected patients with history of typhoid fever and diarrhea at Maternity and Child teaching Hospital in Diwaniyah city. For each isolates antimicrobial susceptibilities for azothromycin and chloramphenicol were determined by Disk diffusion methods.In addition, a broth dilution tests for azithromycin were performed by using serial dilution of concentrations ranging from 4- 32 mg\ liter to record the minimal inhibitory concentration (MIC) for azithromycin .Results: The isolated salmonella species are high susceptible of to azithromycin in comparison to chloramphenicol with lower MIC.Conclusion: though it needs further clinical studies, azithromycin seems to be a suitable therapeutic option for the treatment of typhoid fever in children as well as in adult.

Prevalence, antimicrobial resistance profile and comparison of methods for the isolation of salmonella in chicken liver from Argentina

This study was conducted to estimate the apparent prevalence of Salmonella spp. in chicken livers obtained from markets in Entre Ríos, Argentina, using two culture methods (preenrichment and direct selective agar plating). We also determined the antimicrobial resistance of Salmonella isolated strains and evaluated the performance of the two culture methods and selective-differential plating media used for Salmonella isolation. Of 666 chicken livers studied, 32 organs (4.8%) related to 4 poultry slaughterhouse companies were positive for Salmonella sp. using one or two culture methods. Fifty Salmonella strains were isolated from the positive liver samples and were typed into 3 serovars: S. ser. Schwarzengrund (78%), S. ser. Enteritidis (18%), and S. ser. Typhimurium 4(%). More than one Salmonella serovar was found in livers belonging to two chicken slaughterhouse companies. All strains were susceptible to all antibiotics tested, with the exception of erythromycin (100% resistant) and streptomycin (22% intermediate sensitivity). Overall, 32 (4.80%) and 3 (0.45%) of the chicken liver samples were positive for Salmonella sp. in preenrichment method and direct selective agar plating method, respectively; these percentages were significantly different (P=0.0001; kappa=0.16). There was also a statistical difference in relative accuracy, sensitivity and negative predictive value between the preenrichment method and the direct selective agar plating method; the first had greater values for these parameters than the direct selective agar plating method. These parameters were statistically different between MacConkey agar (MCA) and modified lysine iron (MLIA) in the two culture methods; the second had greater values than MCA for both culture methods. This study shows that even though serovars that are important for public health were isolated, the prevalence of Salmonella sp. is low in chicken livers from Entre Rios, Argentina. The isolated strains do not have multi-resistance patterns. Furthermore, the preenrichment method and MLIA are superior to the direct selective agar plating method and MCA for Salmonella sp. isolation from chicken liver samples, respectively.

PREVALENCE OF SOME ANTIMICROBIAL RESISTANCE GENES IN MULTIDRUG RESISTANT SALMONELLA ISOLATED FROM BROILER CHICKENS

Salmonellosis is one of the major bacterial problems in the poultry industry in Egypt and worldwide. Resistance to antimicrobial agents within nontyphoidal Salmonellae is a serious problem. The present study aimed to analyze some β-lactamase resistance genes in Salmonella isolates from broiler chicken. Five hundred samples were collected from diseased broiler chickens of different ages (3-6 weeks) from different farms in Assiut Governorate during the period from January 2015 to December 2015. Bacteriological examination showed that 26 salmonella isolates were recovered with a prevalence rate of 5.2% Serotyping of Salmonella isolates showed that S. Enteritidis S. Typhimurium, and S. Kentuky were identified at rates of 50%, 30.8% and 19.2%, respectively. Results of antibiogram showed that 18 salmonellaisolates (92.3%) were multidrug resistant. All isolates were screened for the presence of 2 β-lactamase resistance genes (blaCTX and blaCMY) using multiplex PCR. The overall prevalence was 14/26 (53.9%) for blaCTX and 9/26 (34.6%) for blaCMY.

Molecular characterization of antimicrobial multi-drug resistance in non-typhoidal Salmonellae from chicken and clam in Mangalore, India.

Salmonella enterica has been documented as one of the leading causes of salmonellosis throughout the world and is most commonly associated with the consumption of contaminated food products. Thus, this research was aimed at studying the antimicrobial susceptibility pattern and detection of quinolone resistance in Salmonella spp isolated from food of animal origin. Thirty-six Salmonella isolates comprising 8 from poultry and 28 from seafood (clams) were identified, serotyped and characterized for their antimicrobial susceptibility against 10 different antibiotics. Plasmid DNA was isolated from all the isolates by alkaline lysis, quinolone resistant non-typhoidal S. Weltevreden were examined for mutation in the DNA gyrase coding gene. Among the 36 Salmonella isolates, 20 were S. weltevreden (8 from poultry and 12 from seafood) and 16 were S. Typhimurium (from seafood). All the isolates showed multiple resistance to nalidixic acid, tetracycline, co-trimoxazole and nitrofurantoin, but, interestingly, the isolates were 100% susceptible to ampicillin, chloramphenicol and gentamicin. Resistant isolates from the study carried the genes responsible for resistance to respective antibiotics. The strain S130 isolated in the study showed single point mutation, Asp87Gly, at position 87 in quinolone resistance determining region. It revealed mutation in quinolone resistance determining region as a cause for quinolone resistance in non-typhoidal Salmonellae. The occurrence of genes accountable for plasmid mediated resistance to quinolones (viz., qnrA, qnrB and qnrS) in plasmid of non-typhoidal Salmonellae isolates provides evidence for plasmid mediated quinolone resistance.

Характеристика морфологічних ознак та фізіологічних властивостей штамів сальмонел, ізольованих від птиці і телят

In order to develop effective domestic drugs for the prevention of animal salmonella, in our previous studies, 30 isolates of salmonella were obtained from different collections, including those isolated from epizootic centers of salmonellosis. From this collection, six strains of salmonella were selected as promising production strains for constructing vaccine preparations against salmonellosis and as controls for the study of the immunogenic properties of vaccines.The article presents the results of comparative study of morphological characteristics, tinctorial, culture, biochemical, virulent and antigenic properties of six selected salmonella strains.It was established that the strains studied have morphological characteristics characteristic for salmonella, tinctorial, cultural and biochemical properties and typical for each type of antigenic structure. The highest antigenic activity was S. typhimurium (1:256 ± 154 – 1:192 ± 82) and S. dublin (1:192 ± 51), and the lowest was S. gallinarum (1:72 ± 43). S. infantis and S. gallinarum were not virulent for white mice, while virulent properties of other strains had significant differences.Some regularities in the manifestation of virulent and antigenic properties of the studied salmonella strains were revealed. In particular, it was found that the higher the virulence of the strain, the higher its antigenic activity, and the more distant the term from the date of isolation of the strain from the epizootic center of salmonellosis, the less its virulence, that is, the prolonged storage of strains of salmonella leads to a decrease or to a complete loss of their virulence.

Renaissance of Conventional First-Line Antibiotics in Salmonella enterica Clinical Isolates: Assessment of MICs for Therapeutic Antimicrobials in Enteric Fever Cases from Nepal.

Enteric fever caused by Salmonella enterica is a life-threatening systemic illness of gastrointestinal tract especially in tropical countries. Antimicrobial therapy is generally indicated but resistance towards commonly used antibiotics has limited their therapeutic usefulness. Therefore, we aimed to determine the antimicrobial susceptibility pattern by minimum inhibitory concentration method of common therapeutic regimens against Salmonella enterica from enteric fever clinical cases. Salmonella enterica clinical isolates recovered from the patients with suspected enteric fever whose blood samples were submitted to microbiology laboratory of Manmohan Memorial Community Hospital, Kathmandu, from March 2016 to August 2016, were studied. These isolates were subjected to antimicrobial susceptibility testing against common therapeutic antimicrobials by Kirby-Bauer disk diffusion method. The minimum inhibitory concentration of ciprofloxacin, azithromycin, chloramphenicol, and cefixime was determined by Agar dilution method based on the latest CLSI protocol. A total of 88 isolates of Salmonella enterica were recovered from blood samples of enteric fever cases. Out of them, 74 (84.09%) were Salmonella Typhi and 14 (15.91%) were Salmonella Paratyphi A. On Kirby-Bauer disk diffusion antimicrobial susceptibility testing, entire isolates were susceptible to cotrimoxazole, cefixime, ceftriaxone, azithromycin, and chloramphenicol. Sixty-four (72.7%) Salmonella enterica isolates were nalidixic acid resistant and nonsusceptible to ciprofloxacin and levofloxacin. On MIC determination, four Salmonella isolates were ciprofloxacin resistant with MIC 1 µg/ml and two isolates were ciprofloxacin intermediate with MIC 0.5 µg/ml. The MIC range of azithromycin was from 0.125 µg/ml to 2.0 µg/ml, whereas that for chloramphenicol was 2.0 µg/ml–8.0 µg/ml and for cefixime was 0.0075–0.5 µg/ml, respectively. Despite global surge of antimicrobial resistance among Salmonella enterica clinical isolates, the level of drug resistance in our study was not so high. However, higher level of NARST strains limits therapeutic use of fluoroquinolones and necessitates the routine monitoring of such resistance determinants in order to effectively and rationally manage enteric fever cases.