Emergence of antimicrobial-resistant shigellosis in Oregon

Burden of laboratory-confirmed shigellosis infections in Guatemala 2007-2012: results from a population-based surveillance system

BACKGROUND

We describe the epidemiology and antimicrobial susceptibility patterns of culture-confirmed Shigella infections in facility-based surveillance sites in Guatemala. Current studies using quantitative molecular diagnostics suggest Shigella may contribute most to the global diarrheal disease burden. Since identification of Shigella requires culturing techniques using stool specimens and few laboratories in Guatemala routinely culture for this pathogen, little is known about the true burden of Shigella in Guatemala or, importantly, the antimicrobial resistance patterns.

METHODS

Clinical, epidemiological, and laboratory data were collected on 5399 patients with acute diarrhea (≥3 loose stools in 24 h) from June 2007-August 2012. Multidrug resistance (MDR) was defined as resistance to ampicillin and trimethoprim/sulfamethoxazole.

RESULTS

Five percent (261) of stool specimens yielded Shigella spp. The annual incidence of laboratory-confirmed infections ranged from 5.0 to 24.1 per 100,000 persons in Santa Rosa and 0.3 to 6.2 per 100,000 in Quetzaltenango; 58% of cases occurred in children < 5 years of age. Thirty patients were hospitalized; one patient died. Oral rehydration or intravenous solution was used to treat 72% of hospitalized and 15% of ambulatory cases. Fifty-nine percent of cases were S. flexneri and 51% of cases were MDR.

CONCLUSIONS

Shigella is an important cause of bacterial diarrhea in children and prevalence of MDR highlights the importance of appropriate treatment regimens. This study demonstrates that strengthening laboratory capacity in Guatemala can help determine causes which can lead to prevention of diarrheal diseases, particularly in children. Such capacity building is also critical for rapid detection and control of public health threats at their source and therefore for global health security.

Pathogen-associated porin turns IL-10 competent B-1a cells toward proinflammatory cytokine response

Shigellosis is a major problem in the developing countries causing mortality and morbidity particularly among the children. Shigella spp. harbours the epithelial cells of the human colon to infect the host and spread the disease. We analyzed the response of B-1a cells, the major component of the mucosal immune system to porin of Shigella dysenteriae type 1. We show that porin while proliferating B-1a cells, deplete Siglec-G, the inhibitory molecule present on B-1a cells. Adjuvanticity of porin has been shown to govern innate signaling for promoting host adaptive immune response. Up-regulation of CD69 and CD40 denotes activation of the cells parallel to abrogation of Siglec-G. As a result of cell activation, porin stimulated the inflammatory cytokines of CD5⁺ B-1a cells, otherwise rich in IL-10. The work shows B-1a cell responses promote the immunopotentiating activity of porin.

The Rising Dominance of Shigella sonnei: An Intercontinental Shift in the Etiology of Bacillary Dysentery

Shigellosis is the major global cause of dysentery. Shigella sonnei, which has historically been more commonly isolated in developed countries, is undergoing an unprecedented expansion across industrializing regions in Asia, Latin America, and the Middle East. The precise reasons underpinning the epidemiological distribution of the various Shigella species and this global surge in S. sonnei are unclear but may be due to three major environmental pressures. First, natural passive immunization with the bacterium Plesiomonas shigelloides is hypothesized to protect populations with poor water supplies against S. sonnei. Improving the quality of drinking water supplies would, therefore, result in a reduction in P. shigelloides exposure and a subsequent reduction in environmental immunization against S. sonnei. Secondly, the ubiquitous amoeba species Acanthamoeba castellanii has been shown to phagocytize S. sonnei efficiently and symbiotically, thus allowing the bacteria access to a protected niche in which to withstand chlorination and other harsh environmental conditions in temperate countries. Finally, S. sonnei has emerged from Europe and begun to spread globally only relatively recently. A strong selective pressure from localized antimicrobial use additionally appears to have had a dramatic impact on the evolution of the S. sonnei population. We hypothesize that S. sonnei, which exhibits an exceptional ability to acquire antimicrobial resistance genes from commensal and pathogenic bacteria, has a competitive advantage over S. flexneri, particularly in areas with poorly regulated antimicrobial use. Continuing improvement in the quality of global drinking water supplies alongside the rapid development of antimicrobial resistance predicts the burden and international distribution of S. sonnei will only continue to grow. An effective vaccine against S. sonnei is overdue and may become one of our only weapons against this increasingly dominant and problematic gastrointestinal pathogen.

A cohort study to define the age-specific incidence and risk factors of Shigella diarrhoeal infections in Vietnamese children: a study protocol

BACKGROUND

Shigella spp. are one of the most common causes of paediatric dysentery globally, responsible for a substantial proportion of diarrhoeal disease morbidity and mortality, particularly in industrialising regions. Alarming levels of antimicrobial resistance are now reported in S. flexneri and S. sonnei, hampering treatment options. Little is known, however, about the burden of infection and disease due to Shigella spp. in the community.

METHODS/DESIGN

In order to estimate the incidence of this bacterial infection in the community in Ho Chi Minh City, Vietnam we have designed a longitudinal cohort to follow up approximately 700 children aged 12-60 months for two years with active and passive surveillance for diarrhoeal disease. Children will be seen at 6 month intervals for health checks where blood and stool samples will be collected. Families will also be contacted every two weeks for information on presence of diarrhoea in the child. Upon report of a diarrhoeal disease episode, study nurses will either travel to the family home to perform an evaluation or the family will attend a study hospital at a reduced cost, where a stool sample will also be collected. Case report forms collected at this time will detail information regarding disease history, risk factors and presence of disease in the household.Outcomes will include (i) age-specific incidence of Shigella spp. and other agents of diarrhoeal disease in the community, (ii) risk factors for identified aetiologies, (iii) rates of seroconversion to a host of gastrointestinal pathogens in the first few years of life. Further work regarding the longitudinal immune response to a variety of Shigella antigens, host genetics and candidate vaccine/diagnostic proteins will also be conducted.

DISCUSSION

This is the largest longitudinal cohort with active surveillance designed specifically to investigate Shigella infection and disease. The study is strengthened by the active surveillance component, which will likely capture a substantial proportion of episodes not normally identified through passive or hospital-based surveillance. It is hoped that information from this study will aid in the design and implementation of Shigella vaccine trials in the future.

Potential novel antibiotics from HTS targeting the virulence-regulating transcription factor, VirF, from Shigella flexneri

VirF is an AraC-type transcriptional regulator responsible for activating the transcription of virulence genes required for the intracellular invasion and cell-to-cell spread of Shigella flexneri. Gene disruption studies have validated VirF as a potential target for an anti-virulence therapy to treat shigellosis by determining that VirF is necessary for virulence, but not required for bacterial viability. Using a bacteria-based, β-galactosidase reporter assay we completed a high-throughput screening (HTS) campaign monitoring VirF activity in the presence of over 140,000 small molecules. From our screening campaign we identified five lead compounds to pursue in tissue-culture-based invasion and cell-to-cell spread assays and toxicity screens. Our observations of activity in these models for infection have validated our approach of targeting virulence regulation and have allowed us to identify a promising chemical scaffold from our HTS for hit-to-lead development. Interestingly, differential effects on invasion versus cell-to-cell spread suggest that the compounds’ efficacies may depend, in part, on the specific promoter that VirF is recognizing.

Prevalence and trends of aminoglycoside resistance in Shigella worldwide, 1999-2010

Shigellosis causes diarrheal disease in humans in both developed and developing countries, and multi-drug resistance in Shigella is an emerging problem. Understanding changing resistance patterns is important in determining appropriate antibiotic treatments. This meta-analysis systematically evaluated aminoglycoside resistance in Shigella. A systematic review was constructed based on MEDLINE and EMBASE databases. Random-effect models or fixed-effect models were used based on P value considering the possibility of heterogeneity between studies for meta-analysis. Data manipulation and statistical analyses were performed using software STATA 11.0. By means of meta-analysis, we found a lower resistance to three kinds of aminoglycosides in the Europe-America areas during the 12 year study period than that of the Asia-Africa areas. Kanamycin resistance was observed to be the most common drug resistance among Shigella isolates with a prevalence of 6.88% (95%CI: 6.36%-7.43%). Comparison of data from Europe-America and Asia-Africa areas revealed that Shigella flexneri resistance was greater than the resistance calculated for Shigella sonnei. Importantly, Shigella sonnei has played a significant role in aminoglycoside-resistance in recent years. Similarly, data showed that resistance to these drugs in children was higher than the corresponding data of adults. In conclusion, aminoglycoside-resistant Shigella is not an unusual phenomenon worldwide. Distribution in Shigella resistance differs sharply based on geographic areas, periods of time and subtypes. The results from the present study highlight the need for continuous surveillance of resistance and control of antibiotic usage.

Antimicrobial susceptibility patterns of Shigella isolates in Foodborne Diseases Active Surveillance Network (FoodNet) sites, 2000-2010

BACKGROUND

Treatment of shigellosis with appropriate antimicrobial agents shortens duration of illness and bacterial shedding, but resistance to commonly used agents is increasing.

METHODS

We describe resistance patterns among Shigella isolates in the United States with use of linked data from the Foodborne Diseases Active Surveillance Network (FoodNet) and National Antimicrobial Resistance Monitoring System (NARMS). FoodNet sites send every 20th Shigella isolate to the NARMS laboratory for susceptibility testing.

RESULTS

During 2000-2010, the NARMS laboratory tested 1376 Shigella isolates from FoodNet sites. Of 1118 isolates (81%) linked to FoodNet, 826 (74%) were resistant to ampicillin, 649 (58%) to streptomycin, 402 (36%) to trimethoprim-sulfamethoxazole (TMP-SMX), 355 (32%) to sulfamethoxazole-sulfisoxazole, 312 (28%) to tetracycline, 19 (2%) to nalidixic acid, and 6 (0.5%) to ciprofloxacin. The proportion of Shigella isolates with resistance to TMP-SMX was 40% among white persons, 58% among Hispanic persons, and 75% among persons with a history of international travel. Resistance to at least TMP-SMX and ampicillin was present in 25% of isolate, and 5% were resistant to ampicillin, TMP-SMX, and chloramphenicol. Overall, 5% of isolates showed multidrug resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole-sulfisoxazole, and tetracycline, including 49 Shigella flexneri (33%) and 3 Shigella sonnei (0.3%) isolates. Male individuals were more likely than female individuals to be infected with a multidrug-resistant strain (7% versus 3%; P < .01).

CONCLUSIONS

Antimicrobial resistance differed by race, ethnicity, age, travel, and species. Resistance to commonly used antibiotics is high; therefore, it is important to look at the susceptibility pattern before starting treatment.

Cephalosporin-resistant Shigella flexneri over 9 years (2001-09) in India

OBJECTIVES

To determine the pattern and antimicrobial resistance genes of cephalosporin resistance in Shigella flexneri and Shigella dysenteriae over 9 years.

METHODS

Isolates of Shigella (S. flexneri, n = 119 and S. dysenteriae, n = 24) were tested for resistance to ceftriaxone and cefepime by disc diffusion, for MIC by Etest and for extended-spectrum β-lactamase (ESBL) and AmpC production. The presence of antimicrobial resistance genes was investigated by PCR using specific primers for bla(TEM), bla(OXA-1), bla(CTX-M-15), bla(SHV) and bla(CMY-2) for all the isolates.

RESULTS

Twenty (16.8%) S. flexneri isolates were resistant/intermediately susceptible to ceftriaxone/cefepime, while all S. dysenteriae were susceptible. In S. flexneri isolates, the MIC(50) values of ceftriaxone and cefepime were found to be 0.032 and 0.125 mg/L, respectively, while their MIC(90) values were 12 and 8 mg/L, respectively. The MIC(50) and MIC(90) for S. dysenteriae were below 1 mg/L for ceftriaxone; however, for cefepime the MIC(90) was found to be 4 mg/L. Of the 20 resistant/intermediately susceptible S. flexneri isolates, 9 were positive for ESBL production and 4 for AmpC production by phenotypic tests. All 20 isolates were found to be positive for bla(TEM), 10 for bla(CTX-M-15), 8 for bla(OXA) and 7 for bla(CMY-2); none was positive for bla(SHV).

CONCLUSIONS

We report a high level of cephalosporin resistance with high MICs and ESBL- and AmpC-mediated antibiotic resistance in Shigella from north India.

Decreased susceptibility to ciprofloxacin among Shigella isolates in the United States, 2006 to 2009

We characterized 20 Shigella isolates with decreased susceptibility to fluoroquinolones. Most patients (80%) from whom a travel history was obtained reported travel to South or Southeast Asia. Mutations within the quinolone resistance determining regions of gyrA and parC and plasmid-mediated resistance determinants (qnrB, qnrS, and aac(6')-Ib-cr) were identified. The rise in antimicrobial resistance among Shigella isolates may necessitate the increased use of extended-spectrum cephalosporins or macrolides in some patients.

A 9-year study of shigellosis in Northeast Malaysia: Antimicrobial susceptibility and shifting species dominance

Aims

In Malaysia, Shigella spp. is the third most common bacterial agent responsible for childhood diarrhoea. This study was conducted to determine the prevalence and antimicrobial susceptibility patterns of Shigella spp. isolated from patients admitted to the Hospital Universiti Sains Malaysia from January 2001 to December 2009.

Subjects and methods

A hospital-based retrospective study was used. Stool samples from patients were cultured using a standard culture method. Shigella spp. isolates were identified by biochemical and serological methods, and the antimicrobial susceptibility pattern was evaluated using the Kirby-Bauer disc-diffusion method.

Results

A total of 138 Shigella spp. were isolated from a total of 14,830 routine stool specimens, yielding an isolation rate of 0.93% that corresponded to 9.99% of the 1,381 bacterial pathogens isolated. Of these isolates, S. sonnei was the predominant species, followed by S. flexneri and S. boydii. Seasonal variation was noticed, and no significant differences were detected in the demographic data for S. flexneri and S. sonnei. The susceptibility of all isolated Shigella strains was tested against seven antibiotics. Ceftriaxone (99.1%), ciprofloxacin (98.4%), and nalidixic acid (93.8%) were effective against the Shigella strains, whereas tetracycline and trimethoprim-sulfamethoxazole exhibited high frequencies of resistance (58.4% and 53.8%, respectively).

Conclusion

This study is important for public health education aimed at reducing the morbidity and mortality associated with Shigella spp. infection. Our results also will be helpful for paediatricians and microbiologists in the selection of appropriate antibiotics for the management of diarrhoea.

Antimicrobial resistance trends of Shigella serotypes in New York City, 2006-2009

Shigellosis is the third most common enteric bacterial infection in the United States. Although infection is typically self-limiting, empiric treatment is often prescribed. Because of increasing antimicrobial resistance to Shigella, empiric treatment options are decreasing. Identifying resistance patterns can inform empiric treatment recommendations. The goals of our study were to examine risk factors associated with antimicrobial resistance of Shigella and examine issues related to empiric treatment and antimicrobial resistance of Shigella. During June 2006-February 2009, we attempted to interview all New York City patients reported to have shigellosis. Their Shigella isolates were tested for antimicrobial susceptibility to examine the level of resistance and identify risk factors for resistance. Analysis was conducted on two groups distinguished by a large outbreak that was documented during the data collection period. Of the 477 nonoutbreak patients, 333 (70%) patients reported taking an antibiotic for shigellosis and 36 (11%) were treated with an antibiotic to which their Shigella infection was resistant. Among this group, high levels of antimicrobial resistance were detected to amoxicillin-clavulanate (66%), ampicillin (68%), and trimethoprim-sulfamethoxazole (66%). Non-travel-associated ciprofloxacin-resistant Shigella (five patients) and ciprofloxacin-resistant Shigella sonnei (four patients) were reported for the first time to our knowledge. Antimicrobial resistance is significantly higher in New York City residents compared with national data. Some patients were treated with therapies that were not effective and to which the patient's Shigella infection was resistant. Shigella infections should not be treated with antibiotics unless the patient presents with severe or underlying illness and is at risk for systemic illness. When treatment is indicated, local monitoring of Shigella for antimicrobial resistance will provide local clinicians with the best guidance for effective empiric treatments.

Clinical characteristics, drug resistance and etiology in 289 patients with acute infectious diarrhea

AIM: To analyze the clinical characteristics, drug resistance and etiology in 289 infectious diarrhea patients accompanied with purulent bloody stool for guiding epidemiologic study and clinical treatment.

METHODS: Enteric pathogenic bacteria were cultured and identified for species, group and serotype with the biochemical and serologic test. The susceptibility and drug sensitivity of bacteria to antimicrobial agents were tested by K-B disc diffusion method.

RESULTS: Shigellae (69.6%) were the main pathogenic bacteria in infectious diarrhea patients with purulent bloody stools, and the next were Bacillus coli and Vibrion. The ratio of drug fast to quinolone antibiotics was higher in S.flexneri than in S.sonneri (norfloxacin: 11.2% vs 7.6%; ciprofloxacin: 16.3% vs 2.7%; levofloxacin: 2.9% vs 0.0%; all P < 0.01), but the ratio of drug fast to cephalosporin antibiotics was lower in S.flexneri than in S.sonneri (ceftriaxone: 1.2% vs 4.3%; cefotaxime: 0.3% vs 3.8%; cefazolin: 2.2% vs 4.4%; all P < 0.01). The incidence rate was higher in the young patients than that in old patients (72.7% vs 13.5%, P < 0.01), and fever, abdominal pain and diarrhea were the main symptoms. Infectious diarrhea with bloody purulents stools occurred more often in July and August.

CONCLUSION: Shigellae are the main pathogenic bacteria in infectious diarrhea patients, and the next are Bacillus coli and Vibrion. Surveillance for drug sensitivity and resistance to shigellae should be strengthened.

Genetic characterization of multidrug resistance in Shigella spp. from Japan

This study characterized the genetic basis of antimicrobial resistance of a number of Shigella spp. isolated from humans from 2000 to 2004 in Hiroshima prefecture, Japan. A total of 26 isolates of Shigella spp. were included in this study. Antimicrobial susceptibility tests revealed high levels of resistance, especially to ampicillin, streptomycin, trimethoprim, tetracycline, nalidixic acid and ciprofloxacin. PCR and DNA sequencing were used for screening and characterization of antibiotic-resistance determinants. PCR sequencing analysis revealed the presence of only one type of class 1 integron in one isolate of Shigella sonnei. This class 1 integron was 1904 bp and contained two gene cassettes: a probable esterase/lipase (estX) and aadA1, which confers resistance to streptomycin and spectinomycin. Two types of class 2 integron were identified in this study. One was the classic type (2158 bp) and carried the three conserved resistance gene cassettes of the class 2 integron, dfrA1, sat1 and aadA1, which confer resistance to trimethoprim, streptothricin and streptomycin/spectinomycin, respectively. This type was detected in both Shigella sonnei (14 isolates) and Shigella flexneri (five isolates). The other type was shorter (1313 bp) and carried only two gene cassettes, dfrA1 and sat1. This integron was detected in a single isolate of Shigella sonnei. PFGE patterns showed limited diversity within clusters of the same species. Furthermore, an extended-spectrum beta-lactamase gene, bla(OXA-30), which confers resistance to ampicillin, was characterized in all isolates of Shigella flexneri except the oldest strain, which was isolated in 2000. Southern blot hybridization and conjugation experiments showed that bla(OXA-30) was located in the chromosome.

Knowledge, attitudes, and practices regarding antibiotic use among Latinos in the United States: review and recommendations

Inappropriate use of antibiotics contributes to antimicrobial resistance worldwide. In Latin America, antibiotics are easily obtained over the counter. In the United States, the Latino population is the largest and fastest growing immigrant group. Hence, it is necessary to understand Latino cultural practices in regards to antibiotic use to develop effective interventions that reduce inappropriate antibiotic use among this population. We conducted a systematic review of descriptive and intervention studies measuring knowledge, attitudes, and practices of antibiotic use among Latinos in the United States. The search yielded only 11 descriptive studies and no interventions. The literature suggests that many Latinos in the United States self-prescribe antibiotics because of financial and sociocultural barriers and inaccurately believe that antibiotics help treat viral infections. Increased access to health care and appropriate culturally tailored interventions specific to Latinos are needed to promote judicious antibiotic use among Latinos.

Factors which influence Latino community members to self-prescribe antibiotics

BACKGROUND

Although there is consistent evidence of a link between antibiotic use and increasing antimicrobial resistance in the community, inappropriate use of antimicrobials continues to be a global problem.

OBJECTIVE

To describe knowledge, attitudes, and practices of Latino community members in upper Manhattan regarding use of antibiotics.

METHODS

Written questionnaires and eight focus groups comprised of Hispanic community members (three groups), bodega employees, and healthcare providers (one group) in a Latino neighborhood in New York City.

RESULTS

There were major knowledge deficits regarding use of antibiotics. Informants reported taking antibiotics for pain or other conditions as well as for symptoms of infection. Antibiotics were frequently obtained from bodegas without prescription, but generally only for adults, not for children.

DISCUSSION

Interventions to improve antibiotic use that are focused on the formal healthcare system (e.g., clinicians, pharmacists, persons with health insurance) are unlikely to be effective with recently immigrated Latino community members. Successful interventions for this population should include targeted messages to bodega employees, community organizations, and children and their parents.

High prevalence of antimicrobial resistance among Shigella isolates in the United States tested by the National Antimicrobial Resistance Monitoring System from 1999 to 2002

Shigella spp. infect approximately 450,000 persons annually in the United States, resulting in over 6,000 hospitalizations. Since 1999, the National Antimicrobial Resistance Monitoring System (NARMS) for Enteric Bacteria has tested every 10th Shigella isolate from 16 state or local public health laboratories for susceptibility to 15 antimicrobial agents. From 1999 to 2002, NARMS tested 1,604 isolates. Among 1,598 isolates identified to species level, 1,278 (80%) were Shigella sonnei, 295 (18%) were Shigella flexneri, 18 (1%) were Shigella boydii, and 7 (0.4%) were Shigella dysenteriae. Overall, 1,251 (78%) were resistant to ampicillin and 744 (46%) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Prevalence of TMP-SMX- or ampicillin- and TMP-SMX-resistant Shigella sonnei isolates varied by geographic region, with lower rates in the South and Midwest regions (TMP-SMX resistance, 27% and 30%, respectively; ampicillin and TMP-SMX resistance, 25% and 22%, respectively) and higher rates in the East and West regions (TMP-SMX resistance, 66% and 80%, respectively; ampicillin and TMP-SMX resistance, 54% and 65%, respectively). Nineteen isolates (1%) were resistant to nalidixic acid (1% of S. sonnei and 2% of S. flexneri isolates); 12 (63%) of these isolates had decreased susceptibility to ciprofloxacin. One S. flexneri isolate was resistant to ciprofloxacin. All isolates were susceptible to ceftriaxone. Since 1986, resistance to ampicillin and TMP-SMX has dramatically increased. Shigella isolates in the United States remain susceptible to ciprofloxacin and ceftriaxone.

Outbreak of Shigella sonnei gastroenteritis in Northeastern Taiwan

A gastroenteritis outbreak of Shigella sonnei involving 122 children occurred between April 2001 and January 2002 in I-lan, Taiwan. The resistant rates of the isolates to nalidixic acid, trimethoprim-sulfamethoxazole, ampicillin and ceftriaxone were 98, 97.5, 32 and 27%, respectively. None of the isolates was resistant to ciprofloxacin. Prolonged bacterial shedding in the feces can occur when an inappropriate antibiotic is used.

Drug-resistant diarrheogenic Escherichia coli, Mexico

Diarrheogenic Escherichia coli isolates from 45 (73%) of 62 hospitalized patients were resistant to common antimicrobial drugs. Sixty-two percent were multidrug resistant, and >70% were resistant to trimethoprim-sulfamethoxazole and ampicillin. Ciprofloxacin and cefotaxime were uniformly active. Effective and safe oral agents are needed to treat children with bacterial diarrhea.

Antimicrobial susceptibility and pulsed-field gel electrophoresis of Shigella sonnei strains in Malaysia (1997-2000)

AIMS

Antimicrobial resistance of Shigella sonnei from Malaysia was determined and subtyping was carried by pulsed-field gel electrophoresis (PFGE) to assess the extent of genetic diversity of these strains.

METHODS AND RESULTS

A total of 62 isolates of S. sonnei from sporadic cases of shigellosis in different parts of Malaysia were studied by antimicrobial susceptibility test and PFGE. Approximately 35.5% of the strains showed resistance to three or more antimicrobial agents. Eight resistant phenotypes, i.e. RI to RVIII, was defined. Resistant phenotype RV and RVIII only appeared in year 2000. PFGE analysis with NotI and XbaI restriction showed that a great heterogeneity existed at the DNA level among Malaysian S. sonnei isolates. Fifty-eight NotI and 61 XbaI-PFGE profiles were observed in 63 S. sonnei isolates, including ATCC 11060 isolate. Drug sensitive isolates displayed very different profiles from drug-resistant isolates, with a few exceptions. Isolates of resistant phenotype RVI (SXTr.TETr.STRr) showed a greater similarity among each other compared with isolates of resistant phenotype RI and drug-sensitive isolates.

CONCLUSION

Multi-drug-resistant S. sonnei were circulated in different parts of Malaysia and the emergence of new resistant phenotype was observed. Wide genetic variations among Malaysian S. sonnei were observed and the drug-sensitive strains could be differentiated from drug-resistant strains by PFGE.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study verifies the usefulness of PFGE in characterizing and comparing strains of S. sonnei. Minor variations among S. sonnei isolates could be detected by PFGE.

Antimicrobial-resistant Shigella sonnei: limited antimicrobial treatment options for children and challenges of interpreting in vitro azithromycin susceptibility

BACKGROUND

Antimicrobial-resistant Shigella sonnei is a growing problem in the United States and poses treatment challenges particularly among children. Azithromycin is recommended as an alternative oral agent for shigellosis.

METHODS

All isolates of Shigella submitted to Johns Hopkins clinical laboratory during the outbreak year (2002) were compared with a historical comparison group (1996-2000). Isolates were considered multiresistant if they were resistant to ampicillin and trimethoprim-sulfamethoxazole (TS). Selected outbreak and reference isolates were tested for azithromycin susceptibility by E-test, disk diffusion and broth dilution methods.

RESULTS

Between 1996-2000, among the 111 isolates submitted, 63% were from pediatric patients; 63% of isolates were resistant to ampicillin and 12% to TS. In 2002, among the 205 isolates submitted, 82% were from pediatric patients; 91% isolates were resistant to ampicillin and 67% to TS. The proportion of multiresistant isolates increased from 6% in 1996 to 65% in 2002 (P < 0.05). Azithromycin susceptibility by E-test and disk diffusion demonstrated 2 zones of inhibition for S. sonnei. Interpretation using the inner zone resulted in higher MICs (minimal inhibitory concentration) compared with the outer zones by E-test (P < 0.0001) and disk diffusion (P < 0.0001).

CONCLUSIONS

With increasing interest in using azithromycin for shigellosis, clinical laboratories should be aware of the interpretation difficulty caused by the dual-zone phenomenon seen with E-test and disk diffusion methods for S. sonnei.

Important bacterial gastrointestinal pathogens in children: a pathogenesis perspective

This article focuses on the five most common bacterial enteropathogens of the developed world--Helicobacter pylori, Escherichia coli, Shigella, Salmonella, and Campylobacter--from the perspective of how they cause disease and how they relate to each other. Basic and recurring themes of bacterial pathogenesis, including mechanisms of entry, methods of adherence, sites of cellular injury, role of toxins, and how pathogens acquire particular virulence traits (and antimicrobial resistance), are discussed.

Antibiotic resistance in diarrheagenic Escherichia coli and Shigella strains isolated from children in Hanoi, Vietnam

The MICs for 162 diarrheagenic Escherichia coli strains and 28 Shigella strains were determined on the basis of NCCLS guidelines. More than 75% of the strains were resistant to ampicillin, chloramphenicol (53.6% of Shigella strains), and trimethoprim-sulfamethoxazole. Multiresistance was detected in 89.5% of E. coli strains and 78.6% of Shigella strains.

Shigella antibiotic resistance in central Turkey: comparison of the years 1987-1994 and 1995-2002

BACKGROUND

The epidemiology and antibiotic susceptibility of Shigella species changes over time. Updated susceptibility knowledge is necessary for appropriate empirical antibiotic treatment.

METHODS

In this study the clinical characteristics and the antibiotic susceptibility test results of Shigella species isolated from patients admitted to Hacettepe University Ihsan Dogramac Children's Hospital Diarrheal Diseases Training and Treatment Unit between 1995-2002 (n = 218) were evaluated. The results were compared with the results of 1987-1994 from the same center (n = 618).

RESULTS

The predominant species was S. sonnei in both periods with increasing prevalence in the later period (64% and 71.5% respectively, P < 0.05). Although the prevalence of bloody diarrhea among Shigella cases did not change between periods, the prevalence of mild to moderate dehydration (11% and 20.6%) increased. Approximately 40% of cases were prescribed antibiotics on the suspicion of shigellosis. When the two periods were compared, Shigella resistance to trimethoprim/sulfamethoxazole increased from 39% to 70% (P < 0.0001), whereas resistance to ampicillin decreased from 41% to 23% (P < 0.0001). However, the resistance of S. flexneri to ampicillin was found to be quite high (72.9%) between 1995-2002. No Shigella species resistant to ciprofloxacin was detected. Multi-drug resistance was present in 52 (24%) of the cases, of which 10 were S. sonnei (6.3%) and 42 S. flexneri (26.4%) (P < 0.0001).

CONCLUSION

The need to treat all Shigella cases in areas where S. sonnei is predominant should be reevaluated, as should the appropriate empirical antibiotic.

Antimicrobial resistance among enteric pathogens

Diarrhea is a major cause of morbidity and mortality in infants and children worldwide. Use of antimicrobial therapy in children with bacterial diarrhea involves consideration of advantages and limitations of use of appropriate agents in the general population and in specific hosts. Antimicrobial agents for bacterial diarrhea should be prescribed with an appreciation of limitations including antimicrobial resistance. Studies from many countries have reported resistance to Campylobacter jejuni, Campylobacter coli, Shigella species, Salmonella species, and shiga toxin producing Escherichia coli. In many geographic areas of the world including the United States, resistance patterns have demonstrated a consistent increase over the course of time, with resistance occurring to several classes of antimicrobial agents. Resistance patterns are influenced by geographic location, year isolates were obtained, classes of antimicrobial agents, pressure exerted by antimicrobial use, and source of the isolate. Because antimicrobial resistance among enteric pathogens is a common finding, has increased over time, and varies by geographic location, constant monitoring of susceptibility patterns is necessary for selection of appropriate antimicrobial agents for therapy when indicated.

Up-regulation of CD80-CD86 and IgA on mouse peritoneal B-1 cells by porin of Shigella dysenteriae is Toll-like receptors 2 and 6 dependent

Porin of Shigella dysenteriae type 1 increased the mRNA levels for Toll-like receptor (TLR) 2 and TLR6 by 1.5- and 2.9-fold respectively, of peritoneal cavity B-1a and B-1b cells, implicating that coexpression of TLR2 and TLR6 is essential as a combinatorial repertoire for recognition of porin by the B-1 cells. Among the two key TLRs, TLR2 and TLR4, which are primarily responsible for recognizing majority of the bacterial products, TLR2 and not TLR4, participates in porin recognition. TLR2 got increased on both the B-1 cell populations whereas the TLR4 expression remained unaffected. Besides TLRs, mRNA for MyD88, an effector molecule associated with TLR-mediated response was enhanced by 1.8-fold that suggests of its involvement in the activity of porin. Both of the B-1 cell populations expressed strongly the mRNA for NF-kappaB in the presence of porin, that was 2.4-fold more than untreated control, conforming to the earlier finding that coexpression of TLR2 and TLR6, resulted in robust NF-kappaB activation for signaling. Porin treatment of B-1 cell populations of C57BL/6 mice, and C3H/HeJ mice in particular, selectively up-regulated the expression of the costimulatory molecules. CD80 expression got enhanced on the B-1a cells whereas CD86 got solely expressed on B-1b cells. Porin-induced cell surface expression of IgM and IgA on B-1 cell populations from C57BL/6 mice. The IgA-generating capacity, hallmark of mucosal immune response, was confirmed with B-1 cells of C3H/HeJ, the lipopolysaccharide non-responder mouse, in response to the protein. The porin-mediated induction of IgA was augmented by interleukin-6 on B-1a and B-1b cells, by 2.4- and 2.6-fold, respectively. The IgA expressed on both B-1a and B-1b cell surfaces after 72 h of culture was found to bind to the 38 kDa monomer of porin confirming it to be anti-porin IgA antibody.

Shigella infections in children: new insights

Shigellosis , the acute enteric infection caused by bacteria of the genus Shigella , has a worldwide distribution with an estimated annual incidence of 164.7 million cases, of which 163.2 million occur in developing countries, and 1.1 million deaths. Sixty-nine percent of all episodes and 61 percent of all Shigella -related deaths involve children younger than 5 years old. In the United States, 10,000 to 15,000 cases of shigellosis are reported each year. Although usually confined to the colonic mucosa, shigellosis sometimes can cause extraintestinal complications. Recent publications have shed light on the clinical characteristics of Shigella -induced bacteremia, surgical complications, urogenital symptoms, and neurologic manifestations, and on the unique manifestations in the neonatal period. The mainstay of treatment of shigellosis in children is correction of the fluid and electrolyte loss, which often is achieved by the administration of oral rehydration solutions. Appropriate antibiotic therapy shortens the duration of both clinical symptoms and fecal excretion of the pathogen. However, the increasing antimicrobial resistance of shigellae worldwide constitutes a major problem. Regarding the pathophysiology of shigellosis and its complications, recent data not only elucidated the molecular mechanisms involved but also linked manifestations of disease to the interplay of bacterial virulence factors and host responses. The improved understanding of the pathophysiology is hoped to lead to innovative therapeutic approaches against shigellosis and new generations of vaccine candidates.

Availability of antibiotics without prescription in New York City

Misuse of antibiotics in the community has been associated with emergence of increasingly antibiotic-resistant bacterial strains. Although antibiotics in the United States are to be prescribed by a health care provider, the extent to which they are obtained by other means is not known. The purpose of this article is to describe a survey of the availability of nonprescription antibiotics in neighborhood independent businesses in several Manhattan, New York, neighborhoods. A survey was conducted of 101 stores in three neighborhoods--one primarily Hispanic; one primarily black, non-Hispanic; and one primarily white, non-Hispanic. Antibiotics were available in all stores in the Hispanic neighborhood (n = 34), but in none of the others (P < .001). If efforts to rationalize the use of antibiotics are to be successful, the beliefs and cultural norms of subpopulations must be considered, and interventions must be culturally relevant.

Multistate shigellosis outbreak and commercially prepared food, United States

In 2000, shigellosis traced to a commercially prepared dip developed in 406 persons nationwide. An ill employee may have inadvertently contaminated processing equipment. This outbreak demonstrates the vulnerability of the food supply and how infectious organisms can rapidly disseminate through point-source contamination of a widely distributed food item.

Acute infectious gastroenteritis in adults. Seven steps to management and prevention

In caring for patients with acute gastroenteritis, the physician's primary task is to assess the severity of illness and to tailor fluid and electrolyte replacement and symptomatic therapy accordingly. Antibiotics are seldom indicated for acute gastroenteritis, and it is up to the physician to make a rational, informed choice about their use. Narrowing the considerations in differential diagnosis can help guide decision making about the need for diagnostic tests, specific therapy, and public health intervention.

A Pediatric Cluster of Shigella dysenteriae Serotype 1 Diarrhea with Hemolytic Uremic Syndrome in 2 Families from France

We report a cluster of pediatric diarrhea due to Shigella dysenteriae serotype 1 involving 11 children in France, including the index case, who had returned from Senegal. Child-to-child transmission was documented by ribotyping. Five children developed hemolytic uremic syndrome (HUS). On the basis of our findings, the choice of antimicrobial treatment for infections with S. dysenteriae serotype 1 should take into account widespread drug resistance and the risk of HUS.

Porin of Shigella dysenteriae enhances mRNA levels for Toll-like receptor 2 and MyD88, up-regulates CD80 of murine macrophage, and induces the release of interleukin-12

Sera of patients convalescing from shigellosis reacted strongly and specifically with the 38,000 Da monomer of porin of Shigella dysenteriae type 1. Since human, the only natural host of S. dysenteriae type 1, recognized the protein through humoral immune response, it is of great significance to study the surface-exposed outer membrane antigen as an adjuvant. Porin treatment of CD11b+ peritoneal cavity (PerC) MPhi of BALB/c mouse was found to up-regulate CD80 on cell surface and had no effect on CD86 expression. The surface expression of CD80 got increased by 1.6-fold in the presence of gamma interferon (IFN-gamma) supporting selective regulation of the B7-1 (CD80) member of the B7 family. MPhi released 7.25 pg of interleukin-12 (IL-12) in the presence of porin. The protein in combination with IFN-gamma augmented profoundly the release of IL-12 by 2.6-fold. Porin-mediated induction of IL-12 release would therefore influence Th1-type response, known to be preferentially triggered due to up-regulation of CD80 expression. Treatment of PerC MPhi by the protein showed an increase of mRNA for both Toll-like receptor (TLR)2 and myeloid differentiation factor 88 (MyD88) by 2- and 2.3-fold respectively, emphasizing that TLR2 is essential for recognition of S. dysenteriae type 1 porin. Understanding the mechanism of adjuvanticity of porin of S. dysenteriae type 1 is a necessary step towards the development of a better adjuvant against shigellosis.

Diagnosis and treatment of bacterial diarrhea

Diarrheal illness caused by bacterial pathogens is a global health problem and remains one of the most common complaints prompting patients to seek medical care. Strategies to increase the yield of stool culture and new rapid diagnostic tests can improve diagnostic ability. Emerging antimicrobial resistance among the common bacterial causes of diarrhea has made treatment more challenging. Emerging fluoroquinolone resistance is a particular concern. Recent studies of rifaximin, a nonabsorbed antibiotic for the treatment of bacterial diarrhea, have shown favorable results. Rifaximin may represent a much-needed addition to the armamentarium against bacterial agents.

Sexually Transmitted Diseases in Men Who Have Sex with Men: A Clinical Review

Increases in sexually transmitted diseases (STDs) among men who have sex with men (MSM) have coincided with recent increases in sexual risk behaviors across the United States and Europe. The identification of same-sex sexual risk behavior in men and the subsequent risk for certain bacterial and viral infections requires competency in taking a sexual history. Recent advances in the diagnosis and treatment of STDs have made STD management easier for physicians and patients and expanded the ability of a variety of health care professionals to participate in the management of STDs. This review focuses on recent developments in the epidemiology, pathogenesis, diagnosis, and management of common STDs in MSM.

Virtual screening for submicromolar leads of tRNA-guanine transglycosylase based on a new unexpected binding mode detected by crystal structure analysis

Eubacterial tRNA-guanine transglycosylase (TGT) is involved in the hypermodification of cognate tRNAs, leading to the exchange of G34 by preQ1 at the wobble position in the anticodon loop. Mutation of the tgt gene in Shigella flexneri results in a significant loss of pathogenicity of the bacterium due to inefficient translation of a virulence protein mRNA. Herein, we describe the discovery of a ligand with an unexpected binding mode. On the basis of this binding mode, three slightly deviating pharmacophore hypotheses have been derived. Virtual screening based on this composite pharmacophore model retrieved a set of potential TGT inhibitors belonging to several compound classes. All nine tested inhibitors being representatives of these classes showed activity in the micromolar range, two of them even in the submicromolar range.

U.S. medical students' rotations in epidemiology and public health at state and local health departments

Elective rotations in health departments expose medical students to public health practice and career opportunities in applied epidemiology and preventive medicine. State and county epidemiologists and health officers can serve as excellent role models for medical students. In 2000-2001, the authors identified such electives by consulting medical schools' Web sites and by contacting state epidemiologists, teachers of preventive medicine, and medical school associate deans. The authors found that electives were offered in nine state and five local health departments; these are described in detail. Those electives usually focused on infectious diseases, involved students in outbreak investigations when possible, lasted four or more weeks, were open to other students and medical residents, and were overseen by a health department preceptor with a medical school faculty appointment and a commitment to train students. Some electives included more didactic components, encouraged the student to publish a manuscript, or were coordinated by a preventive medicine residency director. The authors observe that health departments can benefit from training enthusiastic medical students via such electives; these students bring fresh ideas to the departments. Medical school catalogs, Web sites, and word of mouth are important means for promoting these electives. Ideally, in the future every medical school will offer a state or local health department elective so that all medical students will become aware of epidemiology and public health career options. The electives reported in this article can help guide additional medical schools and health departments as they initiate such rotations.

Resistance to trimethoprim-sulfamethoxazole

Sulfonamides have a glorious history. In 1935, they were the first class of true antimicrobial agents with life-saving potency. Today, 66 years later, increased bacterial resistance to sulfonamides and to trimethoprim (TMP), a synthetic antimicrobial agent that is 30 years younger than sulfonamides, has limited their use to only a few indications. In the treatment and prophylaxis of patients with urinary tract infections, trimethoprim-sulfamethoxazole (TMP-SMZ) or TMP alone is still considered the first-line drug of choice, although increased bacterial resistance to these agents has been linked with treatment failure. TMP-SMZ has a possible role as a second- or third-line treatment for patients who have respiratory tract infections. In the developing world, where this inexpensive drug is widely used as first-line treatment, bacterial resistance has caused problems, especially with regard to the treatment of patients with severe respiratory tract infections. Use of TMP-SMZ as prophylaxis for Pneumocystis carinii infection has rapidly increased the multidrug resistance of bacterial pathogens found in human immunodeficiency virus-infected patients. Today, detailed and reliable knowledge on the resistance of bacterial pathogens to both TMP-SMZ and TMP is an essential requirement for the safe and effective use of these drugs in all clinical settings.

SHV-type extended-spectrum beta-lactamase in a Shigella flexneri clinical isolate

A Shigella flexneri isolate resistant to oxyimino-cephalosporins was recovered from a stool sample of a 16 month-old Algerian child hospitalized in Paris, France. This isolate harboured an SHV-2 beta-lactamase gene located on a c. 80 kb self-transferable plasmid. This is the first report of an Ambler class A extended-spectrum beta-lactamase from Shigella spp.

Foodborne Illnesses

Foodborne illnesses cause a substantial human and financial burden. Despite sanitary infrastructure improvements, the incidence of foodborne bacterial infections due to non-typhoidal salmonellae (NTS), Campylobacter jejuni, and enterohemorrhagic Escherichia coli (EHEC) has risen over the last two decades. Overall, viruses account for two thirds of all foodborne illness. Most foodborne illnesses are self-limited. Supportive therapy with rehydration and the correction of electrolyte abnormalities is usually sufficient. Antibiotics play a beneficial role in the treatment of patients with certain foodborne diseases, such as listeriosis and typhoid fever, and all patients with tissue invasive or bloodstream infections. Immunocompromised patients should be treated presumptively. Antibiotics are of variable efficacy for the treatment of many infections limited to the gastrointestinal tract, and recommendations differ between pathogens. Antibiotics are generally helpful for shigellosis and cholera, and possibly beneficial for campylobacteriosis. However, antibiotics are potentially harmful in uncomplicated NTS and EHEC gastroenteritis and generally should not be used. Toxin-mediated food poisoning usually does not require specific therapy. The exception is botulism, for which botulinum antitoxin is highly efficacious if used early in the course of illness. Empiric therapy for gastroenteritis is possibly beneficial, though the magnitude of benefit is modest and incurs the risk of inadvertently treating NTS or EHEC. The choice of antibiotic should be based on local resistance patterns and the results of susceptibility testing.

Third-generation cephalosporin resistance in Shigella sonnei, Argentina

Shigella sonnei resistant to cefotaxime (but not to ceftazidime) was isolated for the first time in stool samples from a pediatric patient with vomiting and bloody diarrhea in northern Argentina. Microbiologic and biochemical tests confirmed the presence of an extended spectrum beta-lactamase displaying an apparent isoelectric point value of 8.2.