Linkage of Whole Genome Sequencing, Epidemiological, and Clinical Data to Understand the Genetic Diversity and Clinical Outcomes of Shigella flexneri among Men Who Have Sex with Men in England

The public health value of whole genome sequencing (WGS) for Shigella spp. in England has been limited by a lack of information on sexual identity and behavior. We combined WGS data with other data sources to better understand Shigella flexneri transmission in men who have sex with men (MSM). WGS data for all S. flexneri isolates referred to the national reference laboratory were linked to i) clinical and behavioral data collected in seven of 21 health regions in England using a standardized exposure questionnaire and, ii) national HIV surveillance data. We included 926 S. flexneri isolates, of which 43.0% (n = 398) fell phylogenetically within two domestically circulating clades associated with genotypic markers of azithromycin resistance. Approximately one third of isolates in these clades were from people living with HIV, primarily acquired through sex between men. 182 (19.7%) isolates had linked questionnaire data; 88% (84/95) of MSM isolates fell phylogenetically within the domestically circulating clades, while 92% (72/78) of isolates from other cases fell within lineages linked with travel to high-risk regions. There was no evidence of sustained transmission between networks of MSM and the wider community. MSM were more likely to be admitted to hospital and receive antimicrobials. Our study emphasizes the importance of sex between men as a major route of transmission for S. flexneri. Combined WGS, epidemiological and clinical data provide unique insights that can inform contact tracing, clinical management and the delivery of targeted prevention activities. Future studies should investigate why MSM experience more severe clinical outcomes. IMPORTANCE Within the last 2 decades there have been an increasing number of Shigella spp. outbreaks among men who have sex with men (MSM) worldwide. In 2015, Public Health England (PHE) introduced routine whole genome sequencing (WGS) for the national surveillance of Shigella spp. However, the lack of information on sexual identity and behavior has hindered interpretation. Our study illustrates the power of linking WGS data with epidemiological, behavioral, and clinical data. We provide unique population-level insights into different transmission networks that can inform the delivery of appropriate public health interventions and patient management. Furthermore, we describe and compare clinical characteristics and outcomes of S. flexneri infection in MSM and other exposure groups. We found that MSM were more likely to be admitted to hospital and receive antimicrobials, indicating that their infections were potentially more severe. The exact reasons for this are unclear and require further exploration.

Correlation between the sulfamethoxazole-trimethoprim resistance of Shigella flexneri and the sul genes

The aim of this study was to discuss the correlation between the sulfamethoxazole-trimethoprim resistance of Shigella flexneri (S. flexneri) and the antibiotic resistance genes sul1, sul2, and sul3 and SXT element.From May 2013 to October 2018, 102 isolates of S. flexneri were collected from the clinical samples in Jinan. The Kirby-Bauer (K-B) test was employed to determine the antibiotic susceptibility of the S. flexneri isolates. The antibiotic resistance rate was analyzed with the WHONET5.4 software. The isolates were subject to the PCR amplification of the sul genes (sul1, sul2, and sul3) and the SXT element. On the basis of the sequencing results, the correlation between the sulfamethoxazole-trimethoprim resistance of the S. flexneri isolates and the sul genes was analyzed.The antibiotic resistance rates of the 102 S. flexneri isolates to ampicillin, streptomycin, chloramphenicol, tetracycline, and sulfamethoxazole-trimethoprim were 90.2%, 90.2%, 88.2%, 88.2%, and 62.7%, respectively. The antibiotic resistance rates of these isolates to cefotaxime, ceftazidime, and ciprofloxacin varied between 20% and 35%. However, these isolates were 100% susceptible to cefoxitin. Positive fragments were amplified from 59.8% (61/102) of the 102 S. flexneri isolates, the sizes of the sul1 and sul2 genes being 338 bp and 286 bp, respectively. The sequence alignment revealed the presence of the sul1 and sul2 genes encoding for dihydrofolate synthase. The carrying rate of the sul1 gene was 13.7% (14/102), and that of the sul2 gene was 48.0% (49/102). No target gene fragments were amplified from the 3 isolates resistant to sulfamethoxazole-trimethoprim. The sul3 gene and SXT element were not amplified from any of the isolates. The testing and statistical analysis showed that the resistance of the S. flexneri isolates to sulfamethoxazole-trimethoprim correlated to the sul1 and sul2 genes.The acquired antibiotic resistance genes sul1 and sul2 were closely associated with the resistance of the 102 S. flexneri isolates to sulfamethoxazole-trimethoprim.

Outbreak of multi-drug-resistant (MDR) Shigella flexneri in northern Australia due to an endemic regional clone acquiring an IncFII plasmid

Epidemiological surveillance of Shigella spp. in Australia is conducted to inform public health response. Multi-drug resistance has recently emerged as a contributing factor to sustained local transmission of Shigella spp. All data were collected as part of routine public health surveillance, and strains were whole-genome sequenced for further molecular characterisation. 108 patients with an endemic regional Shigella flexneri strain were identified between 2016 and 2019. The S. flexneri phylogroup 3 strain endemic to northern Australia acquired a multi-drug resistance conferring blaDHA plasmid, which has an IncFII plasmid backbone with virulence and resistance elements typically found in IncR plasmids. This is the first report of multi-drug resistance in Shigella sp. in Australia that is not associated with men who have sex with men. This strain caused an outbreak of multi-drug-resistant S. flexneri in northern Australia that disproportionality affects Aboriginal and Torres Strait Islander children. Community controlled public health action is recommended.

A high number of multidrug-resistant and predominant genetically related cluster of Shigella flexneri strains isolated over 34 years in Brazil

Shigella flexneri has been a major public health problem in developing countries. This work analyzed the frequency of 16 virulence genes, the genotypic diversity, and the antimicrobial resistance profiles of 130 S. flexneri strains isolated in Brazil. The ipaH gene was found in all the 130 strains. The frequencies of the other genes were variable ial (88.5%), sigA (82.3%), iuc (74.6%), virA (73%), pic (72.3%), virF (57.7%), sat (48.5%), ipaBCD (37%), sen (36%), set1A (35.4%), sepA (30%), set1B (30%), virB (14%), icsA (10%), and ipgD (5.4%). A total of 57 (43.8%) strains were multidrug-resistant. ERIC-PCR grouped 96 of the strains into a single cluster with ≥ 70.4% of similarity, 75 of these strains presented a similarity ≥ 80.9%. PFGE grouped 120 of the strains into a single cluster with 57.4% of similarity and 82 of these strains presented a similarity ≥ 70.6%. In conclusion, the high frequency of some virulence genes reinforces the pathogenic potential of the strains studied. The high rates of MDR strains are alarming once it may lead to failure when antimicrobial treatment is necessary. Genotype techniques reveled a major cluster with high genetic similarity including S. flexneri strains from the different Brazilian states and distinct years of isolation, showing that they probably emerged from a common ancestor.

Biomimetic Octopus-like Particles for Ultraspecific Capture and Detection of Pathogens

Infectious diseases caused by pathogenic bacteria (such as sepsis and meningitis) seriously threaten public health; therefore, rapid and accurate identification of the target bacteria is urgently needed to prevent and treat bacterial infections. Although technologies including plate-counting and polymerase chain reaction have been established to detect the pathogenic bacteria, they are either time-consuming or sophisticated. Herein, a biomimetic octopus-like structure integrating merits of multiarm and multivalent interaction is designed for ultraspecific capture and detection of pathogens. The flexible polymeric arms and multivalent ligands work together to mimic the arm-sucker coordination of an octopus to effectively grasp the target pathogens, leading to remarkably high capacity and specificity for the target capture (above 98%, 10 CFU mL^-1) without a nonspecific absorption of background pathogens. The captured bacteria can be identified as a point of care by the surface-enhanced Raman spectroscopy method with a detection limit of 10 cells mL^-1.

Horizontal Transfer of Antimicrobial Resistance Determinants Among Enteric Pathogens Through Bacterial Conjugation

Multi-drug resistance and transfer of mobile genetic elements among enteric pathogens is being reported to have increased rapidly. Commensal Escherichia coli was previously known to acquire mobile genetic elements from other genus/species. E. coli is also capable of disseminating these elements containing antimicrobial resistance determinants through horizontal transfer. Similarly, for Shigellae the antimicrobial resistance are on rise for fluoroquinolones and cephalosporins due to accumulation of mobile elements. Thus the study was hypothesized to investigate the role of transferable plasmids in commensal MDR E. coli vs Salmonella spp, and MDR Shigella flexneri vs Salmonella spp. pKP3-A plasmid containing qnrS1 was successfully transferred from E. coli to Salmonella spp. Similarly, a plasmid containing qnrS1 and bla_CTX-M-15 was transferred from Shigella to Salmonella spp. However, bla_CTX-M-15 was not transferred from E. coli as it was integrated into chromosome that was revealed by next-generation sequencing. This might be a reason that fluoroquinolone-resistant determinants are more frequently transferred than the cephalosporin resistant determinants. Findings from the study emphasize that mobile elements with AMR determinants are significant public health concern that has potential to rapidly disseminate.

Axiom Microbiome Array, the next generation microarray for high-throughput pathogen and microbiome analysis

Microarrays have proven to be useful in rapid detection of many viruses and bacteria. Pathogen detection microarrays have been used to diagnose viral and bacterial infections in clinical samples and to evaluate the safety of biological drug materials. In this study, the Axiom Microbiome Array was evaluated to determine its sensitivity, specificity and utility in microbiome analysis of veterinary clinical samples. The array contains probes designed to detect more than 12,000 species of viruses, bacteria, fungi, protozoa and archaea, yielding the most comprehensive microbial detection platform built to date. The array was able to detect Shigella and Aspergillus at 100 genome copies, and vaccinia virus DNA at 1,000 genome copies. The Axiom Microbiome Array made correct species-level calls in mock microbial community samples. When tested against serum, tissue, and fecal samples from pigs experimentally co-infected with porcine reproductive and respiratory syndrome virus and porcine circovirus type 2, the microarray correctly detected these two viruses and other common viral and bacterial microbiome species. This cost-effective and high-throughput microarray is an efficient tool to rapidly analyze large numbers of clinical and environmental samples for the presence of multiple viral and bacterial pathogens.

Characterization of a serologically atypical Shigella flexneri Z isolated from diarrheal patients in Bangladesh and a proposed serological scheme for Shigella flexneri

Background

Atypical Shigella flexneri Z variant, that agglutinate with E1037 group factor specific monoclonal antisera against Shigella flexneri IV-I but not with other group or type specific antisera, has continuously being isolated in Bangladesh since 1997. Later this serotype has been reported in Indonesia, China and Argentina. Despite being a provisional serotype, continuous isolation of these strains in diverse geographical regions implicated a great necessity to study the overall characteristics of these strains. Therefore, we extensively characterized S. flexneri Z strains using various phenotypic and molecular tools.

Method

Of 3569 S. flexneri isolated between 1997 and 2015, 95 strains were identified as S. flexneri Z using a panel of polyvalent absorbed antisera and monoclonal antisera of S. flexneri (MASF). Of them, randomly selected 65 strains were molecular O-serotyped using multiplex PCR and characterized using different phenotypic and molecular techniques (i.e.biotyping, plasmid profile, virulence marker and PFGE) to determine relationship with other subserotypes of S. flexneri.

Results

All these atypical S. flexneri Z strains were agglutinated with MASF B and IV-I antisera. Concordantly, these strains were positive to opt-gene, responsible for MASF IV-I sero-positive phenotype. However, molecular O-serotyping of all 65 strains could not differentiate between Z and Yb giving similar amplification products (wzx1-5 and opt). Contrarily, MASF based serotypic scheme distinguished among Z and Yb as well as Ya. All these S. flexneri Z showed typical biochemical reaction of S. flexneri, harboured a 140 MDa virulence plasmid and virulence markers namely ipaH, ial, sen, sigA and sepA genes. Along with the virulence plasmid, small plasmids (2.6, 1.8 and 1.6 MDa) were present as core plasmid. Moreover, a middle ranged plasmid and a 4.0 MDa sized plasmid were observed in 65% and 20% strains, respectively. Analysis of PFGE on XbaI-digested chromosomal DNA of Bangladeshi strains showed that S. flexneri Z had a close relatedness with Ya and Yb but completely different than the strains of Xa, Xb, 2a and 2b. This observation was found to be unequivocal while the overall result of biotyping, plasmid profile, and virulence factors was compared. Therefore, we conclude that these atypical serotype Z isolated in Bangladesh had a clonal relationship with Ya and Yb of Bangladesh and the opt gene played an important role in serotypic switching among them. Current serotyping scheme of S. flexneri strains fails to place many such atypical strains (1c, 1c+6, 1d, type 4, and 4c) including S. flexneri Z isolated from different parts of the world. Therefore, an updated serotyping scheme for identification of subserotypes of S. flexneri has been proposed to avoid multiple naming of the same subserotype having similar agglutination pattern.

Bacteriophage Sf6 Tailspike Protein for Detection of Shigella flexneri Pathogens

Bacteriophage research is gaining more importance due to increasing antibiotic resistance. However, for treatment with bacteriophages, diagnostics have to be improved. Bacteriophages carry adhesion proteins, which bind to the bacterial cell surface, for example tailspike proteins (TSP) for specific recognition of bacterial O-antigen polysaccharide. TSP are highly stable proteins and thus might be suitable components for the integration into diagnostic tools. We used the TSP of bacteriophage Sf6 to establish two applications for detecting Shigella flexneri (S. flexneri), a highly contagious pathogen causing dysentery. We found that Sf6TSP not only bound O-antigen of S. flexneri serotype Y, but also the glucosylated O-antigen of serotype 2a. Moreover, mass spectrometry glycan analyses showed that Sf6TSP tolerated various O-acetyl modifications on these O-antigens. We established a microtiter plate-based ELISA like tailspike adsorption assay (ELITA) using a Strep-tag®II modified Sf6TSP. As sensitive screening alternative we produced a fluorescently labeled Sf6TSP via coupling to an environment sensitive dye. Binding of this probe to the S. flexneri O-antigen Y elicited a fluorescence intensity increase of 80% with an emission maximum in the visible light range. The Sf6TSP probes thus offer a promising route to a highly specific and sensitive bacteriophage TSP-based Shigella detection system.

Azithromycin-Nonsusceptible Shigella flexneri 3a in Men Who Have Sex with Men, Taiwan, 2015-2016

We report an outbreak of azithromycin-nonsusceptible Shigella flexneri 3a infection in Taiwan associated with men who have sex with men. The bacterial strains belonged to the sublineage A of a recently reported outbreak lineage associated with men who have sex with men, characterized by reduced azithromycin susceptibility and circulation in shigellosis low-risk regions.

Evaluation of microplate immunocapture method for detection of Vibrio cholerae, Salmonella Typhi and Shigella flexneri from food

BACKGROUND

Improved methods with better separation and concentration ability for detection of foodborne pathogens are in constant need. The aim of this study was to evaluate microplate immunocapture (IC) method for detection of Salmonella Typhi, Shigella flexneri and Vibrio cholerae from food samples to provide a better alternative to conventional culture based methods.

RESULTS

The IC method was optimized for incubation time, bacterial concentration, and capture efficiency. 6 h incubation and log 6 CFU/ml cell concentration provided optimal results. The method was shown to be highly specific for the pathogens concerned. Capture efficiency (CE) was around 100% of the target pathogens, whereas CE was either zero or very low for non-target pathogens. The IC method also showed better pathogen detection ability at different concentrations of cells from artificially contaminated food samples in comparison with culture based methods. Performance parameter of the method was also comparable (Detection limit- 25 CFU/25 g; sensitivity 100%; specificity-96.8%; Accuracy-96.7%), even better than culture based methods (Detection limit- 125 CFU/25 g; sensitivity 95.9%; specificity-97%; Accuracy-96.2%).

CONCLUSION

The IC method poses to be the potential to be used as a method of choice for detection of foodborne pathogens in routine laboratory practice after proper validation.

Risk factors and outcome of Shigella encephalopathy in Bangladeshi children

BACKGROUND

Although, Shigella encephalopathy, a serious extra-intestinal complication of shigellosis, significantly increases the risks of death, data are very limited on predicting factors particularly related to electrolyte profiles in children below five years of age with Shigella encephalopathy. Our objective was to determine the clinical as well as laboratory predicting factors and outcome of children with Shigella encephalopathy.

METHODOLOGY/PRINCIPAL FINDINGS

In this unmatched case-control design, children aged 2-59 months having a positive stool culture for Shigella and who had their serum electrolytes been done from July 2012 to June 2015 were studied. Children with Shigella encephalopathy, defined as having abnormal mentation, constituted the cases, and those without encephalopathy constituted the controls. During the study period, we identified a total of 541 children less than five years of age, who had Shigella in their stool culture. Only 139 children fulfilled the study criteria and among them 69 were cases and 70 were controls. The cases more often had fatal outcome compared to the controls (7% vs. 0%, P = 0.02). In logistic regression analysis, the cases were independently associated with shorter duration (1.2 ± 0.4 days) of diarrhea prior to admission, dehydrating diarrhea, sepsis and hyponatremia (p<0.05 for all). Among 139 Shigella isolates, S. flexneri (88/139, 63%) and S. sonnei(34/139, 24%) were the dominant species. S. dysenteriae was not isolated throughout the study period. S.sonnei was more frequently isolated from the cases (24/69, 35%) than the controls (10/70, 14%), whereas the isolation of S. flexneri was comparable between the groups (40/69, 58% vs 48/70, 69%). A total of 94 (67.6%) isolates were resistant to trimethoprim-sulphamethoxazole, 84 (60.4%) to ciprofloxacin, 66/138 (48%) to ampicillin, 5 (3.5%) to ceftriaxone, 17 (12.2%) to mecillinum and 35 (25%) to azithromycin.

CONCLUSIONS/SIGNIFICANCE

The case-fatality-rate was significantly higher among the children with Shigella encephalopathy compared to those without encephalopathy. Early identification and aggressive management of simple risk factors for Shigella encephalopathy may help to reduce morbidity and deaths in such children especially in resource-limited settings.

Antimicrobial Use for and Resistance of Zoonotic Bacteria Recovered from Nonhuman Primates

As a growing threat to human and animal health, antimicrobial resistance (AMR) has become a central public-health topic. Largescale surveillance systems, such as the National Antimicrobial Resistance Monitoring System (NARMS), are now established to monitor and provide guidance regarding AMR, but comprehensive literature on AMR among NHP is sparse. This study provides data regarding current antimicrobial use strategies and the prevalence of AMR in zoonotic bacteria recovered from NHP within biomedical research institutions. We focused on 4 enteric bacteria: Shigella flexneri, Yersinia enterocolitica, Y. pseudotuberculosis, and Campylobacter jejuni. Fifteen veterinarians, 7 biomedical research institutions, and 4 diagnostic laboratories participated, providing susceptibility test results from January 2012 through April 2015. Veterinarians primarily treated cases caused by S. flexneri, Y. enterocolitica, and Y. pseudotuberculosis with enrofloxacin but treated C. jejuni cases with azithromycin and tylosin. All isolates were susceptible to the associated primary antimicrobial but often showed resistance to others. Specifically, S. flexneri isolates frequently were resistant to erythromycin (87.5%), doxycycline (73.7%), and tetracycline (38.3%); Y. enterocolitica isolates to ampicillin (100%) and cefazolin (93.6%); and C. jejuni isolates to methicillin (99.5%) and cephalothin (97.5%). None of the 58 Y. pseudotuber-culosis isolates was resistant to any tested antimicrobial. Notably, resistance patterns were not shared between this study's NHP isolates and human isolates presented by NARMS. Our findings indicate that zoonotic bacteria from NHP diagnostic samples are broadly susceptible to the antimicrobials used to treat the clinical infections. These results can help veterinarians ensure effective antimicrobial therapy and protect staff by minimizing occupational risk.

Shigellosis in Nepal: 13 years review of nationwide surveillance

BACKGROUND

Shigella is a major cause of gastroenteritis especially in children. In developing countries, the incidence is frequent and results are often life threatening. Changing epidemiology and emerging antibiotic resistance warrants continuous monitoring of susceptibility. The present study highlights the changing epidemiology and drug resistance patterns of Shigella isolated at different hospitals of Nepal over a period of 13 years (Jan. 2003-Dec. 2015).

METHODS

This study was carried out in 12 participating laboratories. Stool specimens received at respective laboratories were processed for isolation and identification of Shigella species and confirmed by serotyping at National Public Health Laboratory. Antimicrobial resistance patterns were determined by Kirby Baeur disc diffusion test.

RESULTS

A total of 332 isolates were identified as Shigella species of which Shigella flexneri (50 %) was the predominant serotype. Shigella dysenteriae, Shigella sonnei, Shigella boydii, and untypable Shigella spp. respectively, accounted for 28.6, 27.54, 10.2, 4.5, and 6.6 % of the total number. Change in prevalent serotype is noted over the years. S. dysenteriae was the prevalent species in Nepal in 2003 and 2004, but since 2005, S. flexneri remained prevalent. Majority of the isolates were recovered from children aged 1-10 years and was statistically significant (p = 0.023) compared to the other age groups. High resistance among all Shigella species to the first-line drugs like ampicillin (88 %), cotrimoxazole (76 %), ciprofloxacin (39 %,) and nalidixic acid (80 %) was observed; 46.1 % of total isolates were multidrug resistant (MDR), and the most common MDR profile was ampicillin, nalidixic acid, and co-trimoxazole. Prevalence of MDR increased significantly in 2010 as compared to 2003. Only few Shigella isolates were resistant to ceftriaxone.

CONCLUSIONS

The study revealed S. flexneri as the predominant serogroup in Nepal. Children below 10 years were more prone to the disease. Nalidixic acid, ampicillin, co-trimoxazole, and ciprofloxacin should not be used empirically as the first-line drugs in treatment of shigellosis. Since the distribution of different species of Shigella and their antibiotic susceptibility profile may vary from one geographical location to another and may also change with time, continuous local monitoring of resistance patterns is necessary for appropriate antimicrobial therapy.

Shigella infections: A two year experience in cancer patients

OBJECTIVE

To identify clinical and microbiological characteristics of Shigella infections among cancer patients.

METHODS

The retrospective study was conducted at Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan, and comprised medical records from December 2011 to November 2013 which were reviewed to identify persons with laboratory-confirmed Shigella infections. Demographic information, clinical history, seasonal variation, microbiological details, treatment given, and outcomes in term of symptoms resolution and mortality at two weeks were noted.

RESULTS

Shigella infection was diagnosed in 45 cancer patients. The mean age of the patients was 36.02±19.30 years (range: 1-64 years), with 35(78%) patients being >18 years of age. Overall, 16(35.5%) patients had presented during winter months and 40(89%) presented as emergencies. Diarrhoea was present in 44(98%) patients and among them 20(45%) had dysentery whereas 28(64%) had fever and 21(47%) had abdominal pain. Of the total 45 cases, 41(91%) had isolates from stool. Besides, 39(87%) Shigella isolates were further speciated and Shigella flexneri was the most commonly isolated serotype in 25(64.1%). Overall, 42(93%) strains were sensitive to cefixime and ceftriaxone. Mean duration of symptoms resolution was 3.92±1.51 days (range: 1-10 days). No mortality was noted at 2 weeks.

CONCLUSIONS

Shigella flexneri was the most common serotype isolated. Majority of the isolates were sensitive to 3rd generation cephalosporins (cefixime/ceftriaxone).

Antimicrobial Resistance of Shigella flexneri Serotype 1b Isolates in China

Shigella flexneri serotype 1b is among the most prominent serotypes in developing countries, followed by serotype 2a. However, only limited data is available on the global phenotypic and genotypic characteristics of S. flexneri 1b. In the present study, 40 S. flexneri 1b isolates from different regions of China were confirmed by serotyping and biochemical characterization. Antimicrobial susceptibility testing showed that 85% of these isolates were multidrug-resistant strains and antibiotic susceptibility profiles varied between geographical locations. Strains from Yunnan were far more resistant than those from Xinjiang, while only one strain from Shanghai was resistant to ceftazidime and aztreonam. Fifteen cephalosporin resistant isolates were identified in this study. ESBL genes (bla_SHV, bla_TEM, bla_OXA, and bla_CTX-M) and ampC genes (bla_MOX,bla_FOX,bla_MIR(ACT-1),bla_DHA,bla_CIT and bla_ACC) were subsequently detected among the 15 isolates. The results showed that these strains were positive only for bla_TEM, bla_OXA, bla_CTX-M, intI1, and intI2. Furthermore, pulsed-field gel electrophoresis (PFGE) analysis showed that the 40 isolates formed different profiles, and the PFGE patterns of Xinjiang isolates were distinct from Yunnan and Shanghai isolates by one obvious, large, missing band. In summary, similarities in resistance patterns were observed in strains with the same PFGE pattern. Overall, the results supported the need for more prudent selection and use of antibiotics in China. We suggest that antibiotic susceptibility testing should be performed at the start of an outbreak, and antibiotic use should be restricted to severe Shigella cases, based on resistance pattern variations observed in different regions. The data obtained in the current study might help to develop a strategy for the treatment of infections caused by S. flexneri 1b in China.

Genetic characterization of Shigella flexneri isolates in Guizhou Province, China

Shigella flexneri is one of the major etiologic causes of shigellosis in Guizhou Province, China. However, the genetic characteristics of circulating isolates are unknown. Phenotypic and molecular profiles of 60 S. flexneri isolates recovered in Guizhou between 1972 to 1982 and 2008 to 2010 were determined. Nine serotypes (1a, 2a, 3a, 1b, 2b, X, Y, 4av and Yv) were identified. Multi-locus sequence typing differentiated the isolates into 20 sequence types (STs); 18 were novel. Four STs, ST 129, ST 100, ST 126 and ST 18, were most abundant, accounting for 65% of the isolates. Thirty-nine NotI-pulsed field gel electrophoresis patterns (pulsotypes, PTs) were observed; eight PTs were represented by more than one isolate with six isolates sharing the PT 13 profile. Multi-locus variable-nucleotide tandem-repeat analysis recognized 44 different types (MTs); seven MTs were represented by more than one isolate and MT 1 was most commonly encountered. Correlation between genetic relationships and serotypes was observed among the isolates studied; the majority of isolates belonging to the same serotype from different years clustered together based on the molecular data. These clustered isolates were also from similar geographical origins. These results enhance our understanding of genetic relationships between S. flexneri in Guizhou Province and can be used to help understand the changing etiology of shigellosis in China.

Clinical and microbiological profiles of shigellosis in children

Shigellosis presents with varied clinical features are dictated by the species involved, virulence factors of the strain, and the host immune status. We studied the species, virulence genes, and antibiotic susceptibility pattern of the Shigella strains isolated from 33 children aged less than 12 years, with clinical features of shigellosis. Identification and antibiotic sensitivity of Shigella species were done using disc diffusion and E-test. Multiplex PCR was done for the detection of virulence genes (ipaH, ial, set1A, set1B, sen, and stx) and ESBL genes. Parents of the children were interviewed using structured questionnaire to assess the severity of the disease; 26 (79%) of the isolates were Shigella flexneri. Ciprofloxacin and ceftriaxone resistance was seen in 23 (69%) and 3 (9%) Shigella isolates respectively. Two ceftriaxone-resistant strains were found to harbour blaCTX gene and the third blaTEM gene. Virulence gene ipaH was detected in 100% of strains while ial, sen, setlA, and setlB were detected in 85%, 61%, 48%, and 48% respectively.

Plasmid-mediated sulfamethoxazole resistance encoded by the sul2 gene in the multidrug-resistant Shigella flexneri 2a isolated from patients with acute diarrhea in Dhaka, Bangladesh

In this study, mechanisms of plasmid-mediated sulfamethoxazole resistances in the clinical strains of multi-drug resistant (MDR) Shigella flexneri 2a were elucidated for the first time in Bangladesh. From 2006 to 2011, a total of 200 S. flexneri 2a strains were randomly selected from the stock of the Enteric and Food Microbiology Laboratory of icddr,b. Antimicrobial susceptibility of the strains showed 73%, 98%, 93%, 58%, 98%, 64% and 4% resistance to trimethoprim-sulfamethoxazole, nalidixic acid, ampicillin, erythromycin, tetracycline, ciprofloxacin and ceftriaxone respectively. Plasmid profiling revealed heterogeneous patterns and interestingly, all the trimethoprim-sulfamethoxazole resistant (SXT(R)) strains yielded a distinct 4.3 MDa plasmid compared to that of the trimethoprim-sulfamethoxazole susceptible (SXT(S)) strains. Curing of this 4.3 MDa plasmid resulted in the susceptibility to sulfamethoxazole alone suggesting the involvement of this plasmid in the resistance of sulfamethoxazole. Moreover, PCR analysis showed the presence of sul2 gene in SXT(R) strains which is absent in SXT(S) strains as well as in the 4.3 MDa plasmid-cured derivatives, confirming the involvement of sul2 in the resistance of sulfamethoxazole. Furthermore, pulsed-field gel electrophoresis (PFGE) analysis revealed that both the SXT(R) and SXT(S) strains were clonal. This study will significantly contributes to the knowledge on acquired drug resistance of the mostly prevalent S. flexneri 2a and further warrants continuous monitoring of the prevalence and correlation of this resistance determinants amongst the clinical isolates of Shigella and other enteric pathogens around the world to provide effective clinical management of the disease.

[Virulence genes and pathogenicity of Shigella flexneri Xv isolated in Beijing]

OBJECTIVE

To understand the biochemical characteristics, virulence genes and pathogenicity of Shigella flexneri Xv isolated in Beijing.

METHODS

61 strains of S. flexneri Xv isolated from diarrhea patients in Beijing were systematically determined through biochemical reactions and serological tests. Application of PCR technique in detection of virulence genes on ipaH, sen, virF, ial and pulsed-field gel electrophoresis (PFGE) was used to identify the related characteristics and on rat lung slices to determine its pathogenicity.

RESULTS

All of the S. flexneri Xv could ferment glucose, mannitol, melibiose and arabinose. Using serum agglutination, we found that the antigen structure was (IV: 7, 8). IpaH, sen, virF and ial that carried rates of virulence genes appeared to be 100%, 81.97%, 75.41% and 80.30%, respectively. Among 61 strains of S. flexneri Xv, the PFGE typing of Shigella bacteria could be divided into 25 belt types while the results from rat lung slices showed inflammatory change of Xv.

CONCLUSION

S. flexneri Xv was found that it carried high rate of Shigella virulence genes, exhibiting genetic polymorphism and highly invasive.

[Direct PCR detection of food-borne bacteria from mixed human feces]

Mixed human feces were evaluated for simultaneous direct PCR detection of 3 food-borne bacteria--verotoxin-producing bacteria, Salmonella, and Shigella. Mixed feces concentrated approximately 2.5% in distilled water, were heated at 95 degrees C for 5 min. The heated suspension was then centrifuged and 5 microL of the supernatant poured into a 45 microL PCR mixture prepared to neutralize PCR inhibitors originating in biological samples. As a result of PCR under the above conditions followed by melting curve analysis (MCA), one positive fecal sample containing food-borne bacteria was detected from among 50 mixed fecal samples, showing the same sensitivity as individual cultivation. Results thus indicate that this method enables rapid, reliable, highly sensitive testing of many fecal samples--especially those of personnel handling food, which requires the simultaneous testing of many samples.

Shigellosis outbreak associated with contaminated well water in a rural elementary school: Sichuan Province, China, June 7-16, 2009

Objectives

We investigated a shigellosis outbreak in an elementary school to identify the source of infection, mode of transmission and risk factors for illness.

Methods

In a case-control investigation, we compared the source of drinking water, consumption of untreated well water and suspected food items, and hygienic habits between case-students and randomly selected asymptomatic control-students, frequency-matched by class on a 1∶1 ratio.

Results

18% of the 533 students and no teachers developed Shigella. 52%(44/85) of case-students and 17% (12/71) of control-students drank untreated well water (OR = 2.3, 95% CI = 1.1–5.8); 47% (n = 40/85) of case-students and 14% (10/71) of control-students drank untreated water from Well A (OR = 3.7, 95% CI = 1.3–11). The odds ratio increased with the amount of untreated Well A water consumed (p = 0.035, χ² test for trend). Rectal swabs from 5 of 6 case-students and water from Well A yielded Shigella flexneri 2b.

Conclusions

This shigellosis outbreak was caused by drinking untreated water from a well polluted by Shigella flexneri 2b.

Ongoing outbreak of Shigella flexneri serotype 3a in men who have sex with men in England and Wales, data from 2009-2011

Diagnoses of Shigella flexneri in the United Kingdom (UK) are usually travel-related. However, since 2009, there has been an overall increase in UK-acquired cases. The Health Protection Agency has been investigating a national outbreak of S. flexneri detected in 2011 and which is still ongoing. Cases occurred mostly in men who have sex with men and were of serotype 3a. The investigation aimed at obtaining epidemiological data to inform targeted outbreak management and control.

[Antagonistic activity of lactobacilli of the colon]

AIM

Study of antagonistic activity of lactobacilli of the colon against members of its autochthonous bacterial flora and agents of some acute infectious and chronic diseases of the gastrointestinal tract.

MATERIALS AND METHODS

Antagonistic activity of 19 lactobacilli cultures against 28 cultures of bacteria belonging to various groups and fungi was evaluated within the framework of specially developed two-stage cultivation technique in the conditions of a combined system. The results of the study were evaluated according to a semi-quantitative scale that allows to put one or the other value of the zone of growth delay of the studied strain culture in compliance with the one or the other (low, moderate, high) level of antagonistic activity of the lactobacillus culture.

RESULTS

Lactobacilli of the colon showed selective antagonistic activity against pathogenic enterobacteriae: pronounced against Salmonella enterica Serovar Enteritidis, Shigella flexneri 2b, Yersinia spp., and trace against Salmonella enterica Serovar Typhimurium. The level of antagonistic activity of lactobacilli against a wide range of members of autochthonous bacterial flora varied in a wide range, without revealing connection neither to its belonging to species, nor to its population level, nor to the belonging to group of the antagonistic effect objects. On the other hand a connection was traced with beloriging to a certain microbiota: being quite active against members of its own microbiota, lactobacilli often showed significantly lower level of antagonistic activity against cultures with the same species name isolated from other microbiota.

CONCLUSION

In light of the results obtained, level of lactobacilli population may hardly be viewed as the only criteria of their full participation in the process of stabilizing microecological welfare of the colon, that allows to make a complete representation of the level of dysbiotic disorder in the mentioned biotope. With in the framework of rational bacteriological diagnostics of the level of dysbiotic disorders in the colon, evaluation of population level of lactobacilli should be evaluated along with the degree of their antagonistic activity against other components of the same microbiota.

Shigellosis outbreak at Addis Ababa University: March-April 2010

BACKGROUND

Between 2006 and 2008, there have been various reports of diarrhea with blood in Ethiopia and also reports of Shigelloses outbreaks in some parts of the country. In March 2010, Addis Ababa University (AAU) Technology Campus reported occurrence of an outbreak of diarrheal illness among students.

OBJECTIVE

The study was conducted to identify the causative agent and the possible source of the diarrhea outbreak that occurred at Technology Campus.

MATERIALS AND METHODS

Active case finding and review of medical records were undertaken to characterize the outbreak. The investigation consisted of a case-control study with laboratory testing and environmental assessment. A structured questionnaire was used to collect data. Data were analyzed using Epi-info (v3.3.2).

RESULTS

A total of 104 suspected cases were identified, based on the case definition, with an attack rate of 6.8%. Stool culture confirmed Shigella flexneri species in 5/11 (45%) of specimens tested. Risk factors associated with illness included eating specific foods at specific meal times. Food items served on Friday March 26, at lunch time (OR: 3.59, CI: 1.0- 12.7, p = 0.04) and on Saturday March 27, during dinner (OR: 2.89 CI: 1.0- 8.2, p = 0.04) were significantly associated with increased odds of illness. Water stored in a tank in the cafeteria had evidence of fecal contamination (fecal coliform count > 161 Mpn /100ml) and the hygiene and sanitary conditions in the cafeteria, kitchen, living area were unsatisfactory.

CONCLUSION

Food-borne transmission and water contamination were suspected as the sources of infection. Regular supervision and inspection of the campus' food handling facilities and practices were recommended to improve food hygiene and sanitation. Improved water storage, correcting periodic water shortages in the latrine facility and promotion of hand washing could reduce potential future outbreaks.

Evaluation of low-copy genetic targets for waterborne bacterial pathogen detection via qPCR

Recent developments in water quality research have highlighted difficulties in accurately predicting the incidence of pathogens within freshwater based on the viability, culturability and metabolic activity of indicator organisms. QPCR-driven assays are candidates to replace standard culture-based methods, however, protocols suitable for routine use have yet to be sufficiently validated. The objective of this study was to evaluate five oligonucleotide primers sets (ETIR, SINV, exoT, VS1 and ipaH2) for their potential applicability in qPCR assays to detect contamination from five waterborne bacterial pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Campylobacter jejuni, Pseudomonas aeruginosa, and Shigella flexneri). An enrichment-free qPCR protocol was also tested using S. Typhimurium-seeded source water, combining membrane filtration and mechanical, chemical and enzymatic lysis techniques to recover the bacterial cells. All five primer sets were found to have high specificity and sensitivity for the tested organisms. Four of the primers were able to detect pathogen loads as low as 10 cells/mL while 200 cells/mL of C. jejuni were detectable in pure culture. Although sensitivity decreased in an artificially contaminated environmental matrix, it was still possible to detect as few as 10 S. Typhimurium cells without enrichment. The primers and protocols evaluated in this study have demonstrated potential for further validation for possible application alongside traditional indicator techniques.

Centers for Disease Control and Prevention (CDC). Notes from the field: emergence of Shigella flexneri 2a resistant to ceftriaxone and ciprofloxacin --- South Carolina, October 2010

On October 20, 2010, the South Carolina Department of Health and Environmental Control and CDC began investigating a cluster of three diarrheal illnesses caused by multidrug-resistant Shigella flexneri 2a. The index case occurred in a girl aged 2 years who experienced the onset of diarrhea on September 25 and was hospitalized the next day because of a seizure and fever. On September 30, her brother, aged 6 years, was hospitalized with vomiting, bloody diarrhea, and hyponatremia. Three days later, her father was hospitalized with vomiting, bloody diarrhea, and hyponatremia.

[Structure of the oligosaccharide region (core) of the lipopolysaccharides of Shigella flexneri types 2a and 5b]

The full structure of the lipopolysaccharide core of bacteria Shigella flexneri types 2a and 5b, the causative agents of bacillary dysentery (shigellosis), was established by chemical methods, high-resolution electrospray ionization mass spectrometry, and two-dimensional NMR spectroscopy. The structure of the O-antigen repeating unit and the configuration and position of the linkage between the O-antigen and the core were determined in the lipopolysaccharide of S. flexneri type 2a.

Highly sensitive detection of Shigella flexneri using fluorescent silica nanoparticles

Robust signal amplification tactic is a good solution for improving detection sensitivity. Unprocessed fluorophores have many limitations. Here we describe an effective strategy for highly sensitive detection of bacteria by using fluorescent conjugated nanoparticles. The nanoparticles were synthesized using silica as matrix. Fluorescein isothiocyanate distributed in the matrix. S. flexneri specific antibody was coated on the surface of the nanoparticles. Compared to the traditional fluorescent antibody, these antibody-coated fluorescent conjugated nanoparticles were resistant to photobleaching and could ensure prolonged microscope checking for a small number of target bacteria. These nanoparticles could be used in routine bacterial detection for different species.

A randomized controlled trial to evaluate the efficacy of lactobacillus GG in infantile diarrhea

In a randomized, double-blind, placebo-controlled trial, 229 infants hospitalized for acute diarrhea in rural India were given a 10-day course of Lactobacillus rhammosus GG (minimum dose, 10 degrees bacteria) or placebo. There was no difference in groups in the duration of diarrhea or numbers of stool on days 3, 6, or 10 of treatment.

Shigella from humans in Thailand during 1993 to 2006: spatial-time trends in species and serotype distribution

In Thailand during 1993-2006, a total of 9063 Shigella isolates from different medical centers were serotyped and trends over time and spatial clustering analyzed. Of 3583 cases with age information, 1315 (37%) cases were from children between 0 and 4 years and 684 (19%) from children between 5 and 8 years. Most infections were recorded during 1993-1994 (> 1500 per year), decreasing to < 200 in 2006. The relative species distribution also changed. During 1993-1994, Shigella flexneri accounted for 2241 (65%) of 3474 isolations. This proportion decreased to 64 (36%) of 176 infections in 2006. Most infections occurred during July and August, and fewest in December. S. flexneri clustered around Bangkok, and Shigella sonnei in southern Thailand. Most S. flexneri infections were caused by serotype 2a (1590 of 4035) followed by serotype var X (1249). For both serotypes, a pronounced decrease in the number of isolates occurred over time. A much smaller decrease was observed for serotype 3a isolates. Phase I S. sonnei was initially most common, but shifted gradually over phase I, II, to only phase II. No differences in spatial distribution were found. The three most common S. flexneri serotypes all clustered in, around, and west of Bangkok. Serotypes 2a and 3a also clustered in southern Thailand, whereas var X clustered north and northeast of Bangkok. In conclusion, looking at Shigella species, Thailand changed from being a developing country to a developed country between 1995 and 1996. In addition, major shifts in the types of S. sonnei were observed as were differences in spatial clustering of S. flexneri and S. sonnei and S. flexneri serotypes.

Epidemiology of highly endemic multiply antibiotic-resistant shigellosis in children in the Peruvian Amazon

OBJECTIVE

Our goal was to estimate the impact of a Shigella vaccine in an area where shigellosis is endemic by characterizing the disease burden and antibiotic-resistance profiles of isolates and by determining the prevalence of Shigella flexneri serotypes.

PATIENTS AND METHODS

We conducted a 43-month-long prospective, community-based diarrheal disease surveillance in 442 children <72 months of age in the Peruvian Amazon between October 1, 2002, and April 15, 2006.

RESULTS

The incidence of diarrheal disease was 4.38 episodes per child-year. The incidence rate for shigellosis was 0.34 episodes per child-year in children <72 months of age and peaked in children between 12 and 23 months at 0.43 episodes per child-year. Maternal education at or beyond the primary grade level, piped water supply, weight-for-age z score, and improved water-storage practices were the most significant determinants of disease in this community with living conditions comparable to many rural areas in the developing world.

CONCLUSIONS

Children living in this region had a 20-fold higher rate of disease incidence detected by active surveillance as those recently estimated by passive detection. Most symptomatic disease was caused by S flexneri, although the diversity of serotypes will require a multivalent vaccine to have a significant impact on the burden of disease caused by shigellosis. Several other public health disease-control interventions targeted at water source and improved storage, nutritional interventions, and improved maternal education seem to have a greater impact than a univalent S flexneri 2a vaccine.

Antimicrobial resistance in Shigella species isolated in Dakar, Senegal (2004-2006)

From May 2004 to October 2006, a prospective study was carried out in Dakar, Senegal, to update information about the antimicrobial susceptibility of Shigella spp. isolated from stool specimens. Among the 165 non-duplicate strains collected, 81 (49%) were identified as Shigella flexneri, 75 (45%) as Shigella sonnei, 5 (3%) as Shigella boydii, and 4 (2%) as Shigella dysenteriae. Disk diffusion testing revealed that the majority of isolates were resistant to sulphonamides, trimethoprim-sulfamethoxazole, streptomycin, and tetracycline (respective overall resistance rates: 90, 90, 96, and 94%). More than half of the S. flexneri isolates were resistant to amoxicillin, amoxicillin-clavulanic acid, and chloramphenicol (respective resistance rates: 59, 58, and 52%), and almost all of the S. sonnei isolates were susceptible to these antimicrobials (respective resistance rates: 4, 1, and 4%). Only one isolate (belonging to the species S. sonnei) was resistant to nalidixic acid and displayed reduced susceptibility to ciprofloxacin.

Epidemiological characterization of resistance and PCR typing of Shigella flexneri and Shigella sonnei strains isolated from bacillary dysentery cases in Southeast Brazil

Shigella spp are Gram-negative, anaerobic facultative, non-motile, and non-sporulated bacilli of the Enterobacteriaceae family responsible for "Shigellosis" or bacillary dysentery, an important cause of worldwide morbidity and mortality. However, despite this, there are very few epidemiological studies about this bacterium in Brazil. We studied the antibiotic resistance profiles and the clonal structure of 60 Shigella strains (30 S. flexneri and 30 S. sonnei) isolated from shigellosis cases in different cities within the metropolitan area of Campinas, State of São Paulo, Brazil. We used the following well-characterized molecular techniques: enterobacterial repetitive intergenic consensus, repetitive extragenic palindromic, and double-repetitive element-polymerase chain reaction to characterize the bacteria. Also, the antibiotic resistance of the strains was determined by the diffusion disk method. Many strains of S. flexneri and S. sonnei were found to be multi-resistant. S. flexneri strains were resistant to ampicillin in 83.3% of cases, chloramphenicol in 70.0%, streptomycin in 86.7%, sulfamethoxazole in 80.0%, and tetracycline in 80.0%, while a smaller number of strains were resistant to cephalothin (3.3%) and sulfazotrim (10.0%). S. sonnei strains were mainly resistant to sulfamethoxazole (100.0%) and tetracycline (96.7%) and, to a lesser extent, to ampicillin (6.7%) and streptomycin (26.7%). Polymerase chain reaction-based typing supported the existence of specific clones responsible for the shigellosis cases in the different cities and there was evidence of transmission between cities. This clonal structure would probably be the result of selection for virulence and resistance phenotypes. These data indicate that the human sanitary conditions of the cities investigated should be improved.

Direct detection of Shigella flexneri and Salmonella typhimurium in human feces by real-time PCR

We have established a SYBR Green-based realtime PCR method using AnyDirect solution, which enhances PCR from whole blood, for direct amplification of the virA gene of Shigella flexneri and the invA gene of Salmonella typhimurium from human feces without prior DNA purification. When we compared the efficiency of conventional or realtime PCR amplification of the virA and invA genes from the supernatant of boiled feces supplemented with S. flexneri and S. typhimurium in the presence or absence of AnyDirect solution, amplification products were detected only in reactions to which AnyDirect solution had been added. The detection limit of real-time PCR was 1 x 10(4) CFU/g feces for S. flexneri and 2 x 10(4) CFU/g feces for S. typhimurium this sensitivity level was comparable to other studies. Our real-time PCR assay with AnyDirect solution is simple, rapid, sensitive, and specific, and allows simultaneous detection of S. flexneri and S. typhimurium directly from fecal samples without prior DNA purification.

Antimicrobial susceptibility of Shigella flexneri and S. dysenteriae isolated from stool specimens of patients with bloody diarrhoea in Mwanza, Tanzania

This study was conducted to determine frequency and pattern of antimicrobial susceptibility of Shigella species isolated from stool specimens collected from patients presenting with bloody diarrhoea in Mwanza City, Tanzania. The study was carried out from October 2004 to October 2005 and involved patients attending Sekou Toure Regional Hospital and Butimba Health Centre. Bacteriological cultures were done at the National Institute for Medical Research laboratory. A total of 489 patients (median age = 20 years) participated in the study and were able to provide stool specimens. Shigella species were isolated from 14% (69/489) of the stool specimens collected. Of the sixty nine strains of Shigella spp isolated, 62 (90%) were S. flexneri and 7 (10%) were S. dysenteriae. All Shigella strains isolated showed high resistance to ampicillin, tetracycline, trimethoprim-sulphamethoxazole and chloramphenicol, drugs commonly used for management of shigellosis in Tanzania. However all isolates were fully susceptible to ciprofloxacin, nalidixic acid, erythromycin, cefuroxime and gentamycin. S. flexneri showed resistance to amoxy-clavulanic_acid and azithromycin in 5% and 2% of isolates, respectively. None of the S. dysenteriae isolates were resistant to these two drugs. Entamoeba histolytica, Giardia lamblia and Schistosoma mansoni were microscopically detected in 16.5%, 4.4% and 5.3% of patients, respectively. These findings suggest that there is a need to carry out extensive susceptibility studies in different parts of the country with view of re-appraising the current guidelines for management of bloody diarrhoea in Tanzania.

Effect of intensive handwashing in the prevention of diarrhoeal illness among patients with AIDS: a randomized controlled study

Patients with AIDS frequently develop diarrhoeal illness. In this randomized, controlled study, 260 patients were screened for those who had not had diarrhoea in the preceding 3 months and who had received a stable highly active antiretroviral therapy regimen for at least 6 weeks prior to the study enrollment. A total of 148 patients met the inclusion criteria and were enrolled: 75 patients were randomly assigned to an intensive handwashing intervention (i.e. handwashing after defecation, after cleaning infants who had defecated, before preparing food, before eating, and before and after sex) and 73 patients were randomly assigned to the control group. Patients in both groups were called weekly by telephone to determine compliance with handwashing and to determine the number of diarrhoeal episodes for the preceding week. Patients were observed for 1 year. Patients assigned to the intensive handwashing intervention group washed their hands more frequently compared with the control group (seven vs four times a day, respectively; P <0.05) and developed fewer episodes of diarrhoeal illness (1.24+/-0.9 vs 2.92+/-0.6 new episodes of diarrhoea, respectively; P <0.001) during the 1 year observation. The most common pathogens identified in both groups in patients who developed diarrhoeal illness were Giardia lamblia, Cryptosporidium, Entamoeba histolytica and Shigella flexneri. These data suggest that intensive handwashing reduces diarrhoeal illness in patients with AIDS.

Dipstick for rapid diagnosis of Shigella flexneri 2a in stool

BACKGROUND

Shigellosis or bacillary dysentery, an acute bloody diarrhoea, is a major public health burden in developing countries. In the absence of prompt and appropriate treatment, the infection is often fatal, particularly in young malnourished children. Here, we describe a new diagnostic test for rapid detection, in stool, at the bedside of patients, of Shigella flexneri 2a, the most predominant agent of the endemic form of the disease.

METHODOLOGY/PRINCIPAL FINDINGS

The test is based on the detection of S.flexneri 2a lipopolysaccharide (LPS) using serotype 2a-specific monoclonal antibodies coupled to gold particles and displayed on one-step immunochromatographic dipstick. A concentration as low as 20 ng/ml of LPS is detected in distilled water and in reconstituted stools in under 15 minutes. The threshold of detection corresponds to a concentration of 5x10(7) CFU/ml of S. flexneri 2a, which provides an unequivocal positive reaction in three minutes in distilled water and reconstituted stools. The specificity is 100% when tested with a battery of Shigella and unrelated strains, in culture. When tested in Vietnam, on clinical samples, the specificity and sensitivity were 99.2 and 91.5%, respectively. A decrease of the sensitivity during the evaluation on stool samples was observed after five weeks at room temperature and was due to moistening of the dipsticks caused by the humidity of the air during the fifth week of the evaluation. This drawback is now overcome by improving the packaging and providing dipsticks individually wrapped in waterproof bags.

CONCLUSION

This simple dipstick-bases test represents a powerful tool for case management and epidemiological surveys.

Escherichia coli, Shigella and Salmonella species in acute diarrhoea in Hamedan, Islamic Republic of Iran

This study investigated the frequency of Escherichia col, Shigella and Salmonella species in stool specimens from patients with diarrhoea presenting to health centres in Hamedan province, Islamic Republic of Iran. From 144 samples, Shigella strains were isolated in 17 cases (11.8%): 10 Sh. flexneri, 3 Sh. sonnei, 2 Sh. boydii and 2 untyped strains. No Salmonella strains were isolated. Using molecular diagnostic methods, diarrheogenic E. coli were detected in 37 cases (25.7%), the majority were enterotoxigenic (ETEC) (22 cases) and Shiga toxin-producing (STEC) strains (15 cases). In 14 cases (9.7%) there was co-infection.

Comparing invasive and non-invasive of isolated Shigella flexneri by electron microscopy of cell culture, SDS-PAGE and Congo red method

BACKGROUND

The aim of this study was to compare invasive and non-invasive strains of Shigella flexneri isolated from Tehran by a 120 kDa protein band by SDS-PAGE, electron microscopy of cell culture and Congo red dye methods.

METHODS

S. flexneri strains were isolated by standard bacterial methods from fecal specimens of children attending to the 3 children's hospitals. Phenotype analysis for screening virulent of strains of S. flexneri was done on a plate of tryptic soy agar contained 0.003% Congo red dye. Whole membrane protein preparations were used to examine the protein profiles of the inner and outer membrane of these Gram-negative bacteria. The protein mixture was electrophoresed through a polyacrylamide gel. The gel was stained with Coomassie brilliant blue R250 and destained with ethanol and acetic acid. HeLa cell culture was done by two-step preparations: one for light microscopy and the other for electron microscopy.

RESULTS

Some of S. flexneri (46%) were Congo red positive colonies. S. flexneri with negative Congo red phenotype could not enter the HeLa cell culture. A 120 kDa protein band was found in 46% of these bacteria which could enter into HeLa cell culture. Pseudopod structures which facilitate bacterial cell-to-cell spread were readily identified by electron microscopy.

DISCUSSION

Since the existence of 120-kDa protein band was corresponded to enter of S. flexneri into the HeLa cell culture and correlated with Congo red dye positive, for identification of invasive and non-invasive S. flexneri strains, the use of a 120-kDa protein band by SDS-PAGE or a simple, rapid and very cheap Congo red dye method is recommended. Because, there are some deaths due to Shigella sp. in our country, notification on the isolation of these bacteria in both children hospitals laboratories and private clinical laboratories is important.

[PFGE of Shigella flexneri 4c isolates from food-poisoning outbreaks and sporadic diarrhea patients]

OBJECTIVE

To know the molecular characteristic of Shigella flexneri 4c isolates from patients in two food-poisoning outbreaks and one sporadic diarrhea case in Hangzhou, China.

METHODS

S. flexneri isolates from patients in two food-poisoning outbreaks (outbreak 1 and outbreak 2, n = 13 and n = 12, respectively) and one sporadic diarrhea patient (n = 1) in Hangzhou during 2003 and 2005 were serotyped. Antibiotic resistances of these isolates were measured by the Kirby-Bauer method. Invasive plasmid antigen gene ipaH was examined by PCR. Pulse field gel electrophoresis (PFGE) was performed for molecular typing.

RESULTS

In outbreak 1, all 13 isolates were S. flexneri 4c, of them 6 isolates tested were quite different in PFGE patterns with dice coefficient from 0.78 to 0.92. In outbreak 2, 10 isolates were S. flexneri 4c and 2 isolates were S. flexneri X, however their PFGE patterns were almost identical (dice coefficient > 0.8). Compared to the two outbreaks isolates, the sporadic isolate was demonstrated with a distinct PFGE pattern (dice coefficient < 0.8). The antibiotic resistance patterns with 14 kinds of antibiotics had a little difference among the isolates from outbreak 1, outbreak 2 and sporadic diarrhea patient, but the same pattern was found among 10 isolates of S. flexneri 4c and 2 isolates of S. flexneri X from outbreak 2.

CONCLUSIONS

PFGE might distinguish the isolates from these two outbreaks and the sporadic diarrhea patient. Some differences in PFGE patterns, serotypes and antibiotic resistance patterns might occur among S. flexneri 4c isolates during an outbreak.