Surveillance of antimicrobial resistance of Salmonella enterica serotype Typhi in seven Asian countries

Prevalence and antimicrobial resistance phenotypes of Salmonella species recovered at various stages of broiler operations in Hathazari, Bangladesh

Background and Aim: Dissemination of multidrug-resistant (MDR) Salmonella through food chains has serious health implications, with higher rates of morbidity and mortality. Broiler meat remains a major reservoir of Salmonella contamination. The lack of proper hygiene in local broiler operations has, therefore, prompted this research into the assessment of Salmonella contamination in local shops and associated antimicrobial resistance (AMR) phenotypes. Materials and Methods: A total of 55 broiler samples including skin, meat, and swab samples from chopping and dressing sites were included in the study. The samples were collected from broiler shops in Hathazari, Bangladesh, and screened for the presence of Salmonella strains using culture-based methods. The isolates were biochemically characterized and further tested for AMR to eight common antibiotics using the disk diffusion technique. Results: Salmonella contaminations were identified in 29% (16/55) of the broiler samples. Swab samples collected from the chopping sites appeared to be contaminated in higher proportions (33%) than those collected from the dressing areas (25%). On the other hand, the skin samples (50%) were detected with a higher percentage of contamination than the meat samples (25%). All Salmonella isolates showed resistance toward at least one of the eight antibiotics used. Although none of the isolates was resistant to all antibiotics, 18.75% showed resistance to a maximum of seven antibiotics. Resistance to nalidixic acid was most prevalent (87.5%), followed by sulfamethoxazole-trimethoprim (81.25%), erythromycin (81.25%), tetracycline (75%), streptomycin (56.25%), ampicillin-clavulanic acid (50%), chloramphenicol (43.75%), and cefotaxime (18.75%). The resistance patterns of the isolates were found to be highly diverse. The most frequently observed pattern was the following: Ampicillin-clavulanic acid-sulfamethoxazole-trimethoprim-nalidixic acid-tetracycline-chloramphenicol-streptomycin-erythromycin. Conclusion: The relatively high prevalence of MDR strains in the samples underlies an urgent need for surveillance and control measures concerning hygiene and antibiotic use in local broiler operations.

Epidemiological Profile and Antimicrobial Resistance Pattern of Enteric Fever in a Tertiary Care Hospital of North India – a Seven Year Ambispective Study

Introduction: Enteric-fever is a major public-health problem in developing countries emerging as multidrug-resistant, Nalidixic-acid resistant and extremely drug-resistant Salmonella (Pakistan, 2016), has intensified the use of WHO watch/reserve group antimicrobials such as azithromycin and meropenem. Methods: This ambispective-study was conducted on 782 non-repeat blood-culture isolates of S. Typhi, S. Paratyphi A and S. Paratyphi B obtained from 29,184 blood cultures received at a 1000-bedded tertiary-care hospital of North-India from 2011–2017. Identification and antibiograms were obtained by Vitek-2 compact and Kirby-Bauer’s disc diffusion with resistance to ampicillin, chloramphenicol and cotrimoxazole being labeled as multidrug-resistant. Decreased ciprofloxacin-susceptibility and ciprofloxacin-resistance were defined as MIC 0.125–0.5 and >1 μg/ml. Results: S. Typhi and S. Paratyphi A in a ratio of 3.9:1 were seen between July–September predominantly distributed between 6–45 year age group. Resistance to co-trimoxazole, chloramphenicol, ceftriaxone and azithromycin was 6.1%, 13.8%, 16.1 and 5.78% respectively. Multidrug-resistant S. typhi and S. paratyphi A were 2.73% and 1.91% respectively. Conclusion: Enteric-fever is a major public-health problem in India. Emergence of multidrug-resistant, Nalidixic-acid resistant and extremely-drug resistant Salmonella mandates ongoing surveillance for targeted empirical therapy and containment of spread. Repeated epidemics call for water, sanitation, hygiene and vaccination strategies to sustain herd-immunity.

Rapid diagnostic tests for typhoid and paratyphoid (enteric) fever

BACKGROUND

Differentiating both typhoid (Salmonella Typhi) and paratyphoid (Salmonella Paratyphi A) infection from other causes of fever in endemic areas is a diagnostic challenge. Although commercial point-of-care rapid diagnostic tests (RDTs) for enteric fever are available as alternatives to the current reference standard test of blood or bone marrow culture, or to the widely used Widal Test, their diagnostic accuracy is unclear. If accurate, they could potentially replace blood culture as the World Health Organization (WHO)-recommended main diagnostic test for enteric fever.

OBJECTIVES

To assess the diagnostic accuracy of commercially available rapid diagnostic tests (RDTs) and prototypes for detecting Salmonella Typhi or Paratyphi A infection in symptomatic persons living in endemic areas.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, IndMED, African Index Medicus, LILACS, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) up to 4 March 2016. We manually searched WHO reports, and papers from international conferences on Salmonella infections. We also contacted test manufacturers to identify studies.

SELECTION CRITERIA

We included diagnostic accuracy studies of enteric fever RDTs in patients with fever or with symptoms suggestive of enteric fever living in endemic areas. We classified the reference standard used as either Grade 1 (result from a blood culture and a bone marrow culture) or Grade 2 (result from blood culture and blood polymerase chain reaction, or from blood culture alone).

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the test result data. We used a modified QUADAS-2 extraction form to assess methodological quality. We performed a meta-analysis when there were sufficient studies for the test and heterogeneity was reasonable.

MAIN RESULTS

Thirty-seven studies met the inclusion criteria and included a total of 5080 participants (range 50 to 1732). Enteric fever prevalence rates in the study populations ranged from 1% to 75% (median prevalence 24%, interquartile range (IQR) 11% to 46%). The included studies evaluated 16 different RDTs, and 16 studies compared two or more different RDTs. Only three studies used the Grade 1 reference standard, and only 11 studies recruited unselected febrile patients. Most included studies were from Asia, with five studies from sub-Saharan Africa. All of the RDTs were designed to detect S.Typhi infection only.Most studies evaluated three RDTs and their variants: TUBEX in 14 studies; Typhidot (Typhidot, Typhidot-M, and TyphiRapid-Tr02) in 22 studies; and the Test-It Typhoid immunochromatographic lateral flow assay, and its earlier prototypes (dipstick, latex agglutination) developed by the Royal Tropical Institute, Amsterdam (KIT) in nine studies. Meta-analyses showed an average sensitivity of 78% (95% confidence interval (CI) 71% to 85%) and specificity of 87% (95% CI 82% to 91%) for TUBEX; and an average sensitivity of 69% (95% CI 59% to 78%) and specificity of 90% (95% CI 78% to 93%) for all Test-It Typhoid and prototype tests (KIT). Across all forms of the Typhidot test, the average sensitivity was 84% (95% CI 73% to 91%) and specificity was 79% (95% CI 70% to 87%). When we based the analysis on the 13 studies of the Typhidot test that either reported indeterminate test results or where the test format means there are no indeterminate results, the average sensitivity was 78% (95% CI 65% to 87%) and specificity was 77% (95% CI 66% to 86%). We did not identify any difference in either sensitivity or specificity between TUBEX, Typhidot, and Test-it Typhoid tests when based on comparison to the 13 Typhidot studies where indeterminate results are either reported or not applicable. If TUBEX and Test-it Typhoid are compared to all Typhidot studies, the sensitivity of Typhidot was higher than Test-it Typhoid (15% (95% CI 2% to 28%), but other comparisons did not show a difference at the 95% level of CIs.In a hypothetical cohort of 1000 patients presenting with fever where 30% (300 patients) have enteric fever, on average Typhidot tests reporting indeterminate results or where tests do not produce indeterminate results will miss the diagnosis in 66 patients with enteric fever, TUBEX will miss 66, and Test-It Typhoid and prototype (KIT) tests will miss 93. In the 700 people without enteric fever, the number of people incorrectly diagnosed with enteric fever would be 161 with Typhidot tests, 91 with TUBEX, and 70 with Test-It Typhoid and prototype (KIT) tests. The CIs around these estimates were wide, with no difference in false positive results shown between tests.The quality of the data for each study was evaluated using a standardized checklist called QUADAS-2. Overall, the certainty of the evidence in the studies that evaluated enteric fever RDTs was low.

AUTHORS' CONCLUSIONS

In 37 studies that evaluated the diagnostic accuracy of RDTs for enteric fever, few studies were at a low risk of bias. The three main RDT tests and variants had moderate diagnostic accuracy. There was no evidence of a difference between the average sensitivity and specificity of the three main RDT tests. More robust evaluations of alternative RDTs for enteric fever are needed.

Challenges and future prospects of antibiotic therapy: from peptides to phages utilization

Bacterial infections are raising serious concern across the globe. The effectiveness of conventional antibiotics is decreasing due to global emergence of multi-drug-resistant (MDR) bacterial pathogens. This process seems to be primarily caused by an indiscriminate and inappropriate use of antibiotics in non-infected patients and in the food industry. New classes of antibiotics with different actions against MDR pathogens need to be developed urgently. In this context, this review focuses on several ways and future directions to search for the next generation of safe and effective antibiotics compounds including antimicrobial peptides, phage therapy, phytochemicals, metalloantibiotics, lipopolysaccharide, and efflux pump inhibitors to control the infections caused by MDR pathogens.

Gatifloxacin versus ofloxacin for the treatment of uncomplicated enteric fever in Nepal: an open-label, randomized, controlled trial

Background

Fluoroquinolones are the most commonly used group of antimicrobials for the treatment of enteric fever, but no direct comparison between two fluoroquinolones has been performed in a large randomised trial. An open-label randomized trial was conducted to investigate whether gatifloxacin is more effective than ofloxacin in the treatment of uncomplicated enteric fever caused by nalidixic acid-resistant Salmonella enterica serovars Typhi and Paratyphi A.

Methodology and Principal Findings

Adults and children clinically diagnosed with uncomplicated enteric fever were enrolled in the study to receive gatifloxacin (10 mg/kg/day) in a single dose or ofloxacin (20 mg/kg/day) in two divided doses for 7 days. Patients were followed for six months. The primary outcome was treatment failure in patients infected with nalidixic acid resistant isolates. 627 patients with a median age of 17 (IQR 9–23) years were randomised. Of the 218 patients with culture confirmed enteric fever, 170 patients were infected with nalidixic acid-resistant isolates. In the ofloxacin group, 6 out of 83 patients had treatment failure compared to 5 out of 87 in the gatifloxacin group (hazard ratio [HR] of time to failure 0.81, 95% CI 0.25 to 2.65, p = 0.73). The median time to fever clearance was 4.70 days (IQR 2.98–5.90) in the ofloxacin group versus 3.31 days (IQR 2.29–4.75) in the gatifloxacin group (HR = 1.59, 95% CI 1.16 to 2.18, p = 0.004). The results in all blood culture-confirmed patients and all randomized patients were comparable.

Conclusion

Gatifloxacin was not superior to ofloxacin in preventing failure, but use of gatifloxacin did result in more prompt fever clearance time compared to ofloxacin. Trial registration: ISRCTN 63006567 (www.controlled-trials.com).

Enteric fever, which comprises of typhoid and paratyphoid fevers, is common in many developing countries. It is also sometimes seen in the Western world in returning travellers. This present study of uncomplicated enteric fever in an outpatient setting in a hospital in Kathmandu, Nepal compared the newer gatifloxacin with the widely-used ofloxacin (two drugs of the fluroquinolone class) in the treatment of this illness. Although fluroquinolones are commonly considered the main group of drugs in the treatment of enteric fever, there have not been comparisons of efficacy between two drugs in this same class in the treatment of enteric fever. Furthermore, certain strains of enteric fever organism called nalidixic-acid resistant strains are proving very difficult to treat in both the local population and the Western travellers. The study focused primarily on the efficacy of the 2 drugs against these particular strains. The results revealed that both drugs were effective but gatifloxacin decreased the patient's fever more rapidly than ofloxacin. Dysglycemia was noted in a 35-year-old woman taking gatifloxacin who did not disclose a pre-existing diagnosis of diabetes at time of enrollment, but not in any other healthy child or young adult.

Non-typhoidal Salmonella gastroenteritis at a diarrheal hospital in Dhaka, Bangladesh, 1996-2011

Data on non-typhoidal Salmonella (NTS) infection in South Asia are limited. We used data gathered prospectively from 1996 to 2011 as part of a hospital surveillance system in Dhaka, Bangladesh, to identify diarrheal patients with NTS isolated from stool. NTS was isolated in 1.3% (468 of 37,439) of diarrheal patients; 47% of total cases of NTS were in children < 5 years of age, although older adults (≥ 60 years) had the highest isolation rates. NTS isolation peaked in the monsoon months of July and August. Over the study period, rates of multidrug resistance decreased, whereas rates of decreased susceptibility to ciprofloxacin increased. Compared with control patients, NTS patients were older and wealthier; however, no differences in type of housing or exposure to animals were found. NTS patients had increased inflammatory cells in stool and required more fluid resuscitation.

In vitro susceptibility testing of fluoroquinolone activity against Salmonella: recent changes to CLSI standards

Fluoroquinolone (FQ) resistance in Salmonella enterica is a significant clinical concern. Recognition of resistance by the clinical laboratory is complicated by the multiple FQ resistance mechanisms found in Salmonella. The Clinical Laboratory Standards Institute (CLSI) recently addressed this issue by revising the ciprofloxacin break points for Salmonella species. It is critical for clinicians and laboratory workers to be aware of the multiple technical issues surrounding these revised break points. In this article, we review FQ resistance mechanisms in Salmonella, their clinical significance, and data supporting the revised ciprofloxacin break points. We encourage clinical laboratories to adopt the revised CLSI ciprofloxacin break points for all Salmonella isolates in which susceptibility testing is indicated and discuss the technical issues for laboratories using commercial antimicrobial susceptibility systems.

Highly resistant Salmonella enterica serovar Typhi with a novel gyrA mutation raises questions about the long-term efficacy of older fluoroquinolones for treating typhoid fever

As a consequence of multidrug resistance, clinicians are highly dependent on fluoroquinolones for treating the serious systemic infection typhoid fever. While reduced susceptibility to fluoroquinolones, which lessens clinical efficacy, is becoming ubiquitous, comprehensive resistance is exceptional. Here we report ofloxacin treatment failure in typhoidal patient infected with a novel, highly fluoroquinolone-resistant isolate of Salmonella enterica serovar Typhi. The isolation of this organism has serious implications for the long-term efficacy of ciprofloxacin and ofloxacin for typhoid treatment.

Salmonella infections: an update on epidemiology, management, and prevention

Salmonella species are a group of Gram-negative enterobacteria and known human pathogens in developing as well as industrialized countries. Despite significant advances in sanitation, provision of potable water, and highly controlled food chain surveillance, transmission of Salmonella spp. continues to affect communities, preferentially children, worldwide. This review summarizes updated concepts on typhoidal and non-typhoidal Salmonella infections, starting with a historical perspective that implicates typhoid Salmonella as a significant human pathogen since ancient times. We describe the epidemiology of this pathogen with emphasis on the most recent non-typhoidal Salmonella outbreaks in industrialized countries and continued outbreaks of typhoid Salmonella in underserved countries. An overview of clinical aspects of typhoid and non-typhoid infections in developing and industrialized countries, respectively, is provided, followed by a description on current treatment concepts and challenges treating multidrug-resistant Salmonella infections. We conclude with prevention recommendations, and recent research studies on vaccine prevention.

Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever)

BACKGROUND

Typhoid and paratyphoid are febrile illnesses, due to a bacterial infection, which remain common in many low- and middle-income countries. The World Health Organization (WHO) currently recommends the fluoroquinolone antibiotics in areas with known resistance to the older first-line antibiotics.

OBJECTIVES

To evaluate fluoroquinolone antibiotics for treating children and adults with enteric fever.

SEARCH STRATEGY

We searched The Cochrane Infectious Disease Group Specialized Register (February 2011); Cochrane Central Register of Controlled Trials (CENTRAL), published in The Cochrane Library (2011, Issue 2); MEDLINE (1966 to February 2011); EMBASE (1974 to February 2011); and LILACS (1982 to February 2011). We also searched the metaRegister of Controlled Trials (mRCT) in February 2011.

SELECTION CRITERIA

Randomized controlled trials examining fluoroquinolone antibiotics, in people with blood, stool or bone marrow culture-confirmed enteric fever.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial's methodological quality and extracted data. We calculated risk ratios (RR) for dichotomous data and mean difference for continuous data with 95% confidence intervals (CI).Comparative effectiveness has been interpreted in the context of; length of treatment, dose, year of study, known levels of antibiotic resistance, or proxy measures of resistance such as the failure rate in the comparator arm.

MAIN RESULTS

Twenty-six studies, involving 3033 patients, are included in this review.Fluoroquinolones versus older antibiotics (chloramphenicol, co-trimoxazole, amoxicillin and ampicillin)In one study from Pakistan in 2003-04, high clinical failure rates were seen with both chloramphenicol and co-trimoxazole, although resistance was not confirmed microbiologically. A seven-day course of either ciprofloxacin or ofloxacin were found to be superior. Older studies of these comparisons failed to show a difference (six trials, 361 participants).In small studies conducted almost two decades ago, the fluoroquinolones were demonstrated to have fewer clinical failures than ampicillin and amoxicillin (two trials, 90 participants, RR 0.11, 95% CI 0.02 to 0.57).Fluoroquinolones versus current second-line options (ceftriaxone, cefalexin, and azithromycin)The two studies comparing a seven day course of oral fluoroquinolones with three days of intravenous ceftriaxone were too small to detect important differences between antibiotics should they exist (two trials, 89 participants).In Pakistan in 2003-04, no clinical or microbiological failures were seen with seven days of either ciprofloxacin, ofloxacin or cefixime (one trial, 139 participants). In Nepal in 2005, gatifloxacin reduced clinical failure and relapse compared to cefixime, despite a high prevalence of NaR in the study population (one trial, 158 participants, RR 0.04, 95% CI 0.01 to 0.31).Compared to a seven day course of azithromycin, a seven day course of ofloxacin had a higher rate of clinical failures in populations with both multi-drug resistance (MDR) and nalidixic acid resistance (NaR) enteric fever in Vietnam in 1998-2002 (two trials, 213 participants, RR 2.20, 95% CI 1.23 to 3.94). However, a more recent study from Vietnam in 2004-05, detected no difference between gatifloxacin and azithromycin with both drugs performing well (one trial, 287 participants).

AUTHORS' CONCLUSIONS

Generally, fluoroquinolones performed well in treating typhoid, and maybe superior to alternatives in some settings. However, we were unable to draw firm general conclusions on comparative contemporary effectiveness given that resistance changes over time, and many studies were small. Policy makers and clinicians need to consider local resistance patterns in choosing a fluoroquinolone or alternative.There is some evidence that the newest fluoroquinolone, gatifloxacin, remains effective in some regions where resistance to older fluoroquinolones has developed. However, the different fluoroquinolones have not been compared directly in trials in these settings.

The influence of reduced susceptibility to fluoroquinolones in Salmonella enterica serovar Typhi on the clinical response to ofloxacin therapy

Background

Infection with Salmonella enterica serovar Typhi (S. Typhi) with reduced susceptibility to fluoroquinolones has been associated with fluoroquinolone treatment failure. We studied the relationship between ofloxacin treatment response and the ofloxacin minimum inhibitory concentration (MIC) of the infecting isolate. Individual patient data from seven randomised controlled trials of antimicrobial treatment in enteric fever conducted in Vietnam in which ofloxacin was used in at least one of the treatment arms was studied. Data from 540 patients randomised to ofloxacin treatment was analysed to identify an MIC of the infecting organism associated with treatment failure.

Principal Findings

The proportion of patients failing ofloxacin treatment was significantly higher in patients infected with S. Typhi isolates with an MIC≥0.25 µg/mL compared with those infections with an MIC of ≤0.125 µg/mL (p<0.001). Treatment success was 96% when the ofloxacin MIC was ≤0.125 µg/mL, 73% when the MIC was between 0.25 and 0.50 µg/mL and 53% when the MIC was 1.00 µg/mL. This was despite a longer duration of treatment at a higher dosage in patients infected with isolates with an MIC≥0.25 µg/mL compared with those infections with an MIC of ≤0.125 µg/mL.

Significance

There is a clear relationship between ofloxacin susceptibility and clinical outcome in ofloxacin treated patients with enteric fever. An ofloxacin MIC of ≥0.25 µg/mL, or the presence of nalidixic acid resistance, can be used to define S. Typhi infections in which the response to ofloxacin may be impaired.

Typhoid fever is an infection of the bloodstream caused by the organism Salmonella Typhi (S. Typhi). Treatment with antimicrobials is critical for preventing severe infection and even death, yet antimicrobial resistant organisms have become a problem in many places where typhoid is common. Fluoroquinolones are a group of antimicrobials that are commonly used to treat typhoid, we analysed data from 540 enteric fever patients treated with ofloxacin (a fluoroquinolone) to identify a level of resistance (minimum inhibitory concentration (MIC)) from the infecting organism which is associated with treatment failure. The proportion of patients failing treatment was higher in those infected with a bacterium with an MIC≥0.25 µg/mL, compared with those infections with an MIC of ≤0.125 µg/mL. Treatment success was 96% when the ofloxacin MIC was ≤0.125 µg/mL, yet only 53% when the MIC was 1.00 µg/mL. Our data demonstrates that an S. Typhi bacterium with an ofloxacin MIC of ≥0.25 µg/mL correlates with a poor outcome when treated with this antimicrobial. Therefore, we propose an amendment in the current MIC guidelines for microbiology laboratories to aid clinicians treating typhoid and suggest the use of alternative therapy in these patients.

YqiC of Salmonella enterica serovar Typhimurium is a membrane fusogenic protein required for mice colonization

BACKGROUND

Salmonella enterica serovar Typhimurium is an intracellular bacterial pathogen which can colonize a variety of hosts, including human, causing syndromes that vary from gastroenteritis and diarrhea to systemic disease.

RESULTS

In this work we present structural information as well as insights into the in vivo function of YqiC, a 99-residue protein of S. Typhimurium, which belongs to the cluster of the orthologous group 2960 (COG2960). We found that YqiC shares biophysical and biochemical properties with Brucella abortus BMFP, the only previously characterized member of this group, such as a high alpha helix content, a coiled-coil domain involved in trimerization and a membrane fusogenic activity in vitro. In addition, we demonstrated that YqiC localizes at cytoplasmic and membrane subcellular fractions, that a S. Typhimurium yqiC deficient strain had a severe attenuation in virulence in the murine model when inoculated both orally and intraperitoneally, and was impaired to replicate at physiological and high temperatures in vitro, although it was still able to invade and replicate inside epithelial and macrophages cell lines.

CONCLUSION

This work firstly demonstrates the importance of a COG2960 member for pathogen-host interaction, and suggests a common function conserved among members of this group.

Suitable disk antimicrobial susceptibility breakpoints defining Salmonella enterica serovar Typhi isolates with reduced susceptibility to fluoroquinolones

Infections with Salmonella enterica serovar Typhi isolates that have reduced susceptibility to ofloxacin (MIC ≥ 0.25 μg/ml) or ciprofloxacin (MIC ≥ 0.125 μg/ml) have been associated with a delayed response or clinical failure following treatment with these antimicrobials. These isolates are not detected as resistant using current disk susceptibility breakpoints. We examined 816 isolates of S. Typhi from seven Asian countries. Screening for nalidixic acid resistance (MIC ≥ 16 μg/ml) identified isolates with an ofloxacin MIC of ≥0.25 μg/ml with a sensitivity of 97.3% (253/260) and specificity of 99.3% (552/556). For isolates with a ciprofloxacin MIC of ≥0.125 μg/ml, the sensitivity was 92.9% (248/267) and specificity was 98.4% (540/549). A zone of inhibition of ≤28 mm around a 5-μg ofloxacin disc detected strains with an ofloxacin MIC of ≥0.25 μg/ml with a sensitivity of 94.6% (246/260) and specificity of 94.2% (524/556). A zone of inhibition of ≤30 mm detected isolates with a ciprofloxacin MIC of ≥0.125 μg/ml with a sensitivity of 94.0% (251/267) and specificity of 94.2% (517/549). An ofloxacin MIC of ≥0.25 μg/ml and a ciprofloxacin MIC of ≥0.125 μg/ml detected 74.5% (341/460) of isolates with an identified quinolone resistance-inducing mutation and 81.5% (331/406) of the most common mutant (carrying a serine-to-phenylalanine mutation at codon 83 in the gyrA gene). Screening for nalidixic acid resistance or ciprofloxacin and ofloxacin disk inhibition zone are suitable for detecting S. Typhi isolates with reduced fluoroquinolone susceptibility.

Global trends in typhoid and paratyphoid Fever

Typhoid and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and Southeast Asia, where enteric fever is associated with poor sanitation and unsafe food and water. High-quality incidence data from Asia are underpinning efforts to expand access to typhoid vaccines. Efforts are underway to develop vaccines that are immunogenic in infants after a single dose and that can be produced locally in countries of endemicity. The growing importance of Salmonella enterica serotype Paratyphi A in Asia is concerning. Antimicrobial resistance has sequentially emerged to traditional first-line drugs, fluoroquinolones, and third-generation cephalosporins, posing patient treatment challenges. Azithromycin has proven to be an effective alternative for treatment of uncomplicated typhoid fever. The availability of full genome sequences for S. enterica serotype Typhi and S. enterica serotype Paratyphi A confirms their place as monomorphic, human-adapted pathogens vulnerable to control measures if international efforts can be redoubled.

Elucidation of Antimicrobial Susceptibility Profiles and Genotyping of Salmonella enterica Isolates from Clinical Cases of Salmonellosis in New Mexico in 2008

In this study, we investigated the antimicrobial susceptibility profiles and the distribution of some well known genetic determinants of virulence in clinical isolates of Salmonella enterica from New Mexico. The minimum inhibitory concentrations (MICs) for various antimicrobials were determined by using the E-test strip method according to CLSI guidelines. Virulence genotyping was performed by polymerase chain reaction (PCR) using primers specific for known virulence genes of Salmonella enterica. Of 15 isolates belonging to 11 different serovars analyzed, one isolate of Salmonella Typhimurium was resistant to multiple drugs namely ampicillin, amoxicillin / clavulanic acid, chloramphenicol and tetracycline, that also harbored class 1 intergron, bla(TEM) encoding genes for β-lactamase, chloramphenicol acetyl transferase (cat1), plus floR, tet(C) and tet(G). This strain was phage typed as DT104. PCR analysis revealed the presence of invA, hilA, stn, agfA and spvR virulence genes in all the isolates tested. The plasmid-borne pefA gene was absent in 11 isolates, while 5 isolates lacked sopE. One isolate belonging to serogroup E4 (Salmonella Sombre) was devoid of multiple virulence genes pefA, iroB, shdA and sopE. These results demonstrate that clinical Salmonella serotypes from New Mexico used here are predominantly sensitive to multiple antimicrobial agents, but vary in their virulence genotypes. Information on antimicrobial sensitivity and virulence genotypes will help in understanding the evolution and spread of epidemic strains of Salmonella enterica in the region of study.