Molecular studies of plasmids of multiply-resistant Shigella spp. in Hong Kong.

One hundred and two Shigella spp. isolated in two hospitals in Hong Kong were analysed for antibiotic resistances, resistance plasmids and plasmid profiles. Three quarters of the isolates were S. flexneri. All isolates harboured plasmids, up to a maximum of ten within one strain. Plasmids of 220 kb encoding resistances to tetracycline, chloramphenicol and sulphonamide and probably also associated with invasiveness in the Sereny test were found in 80 strains and were transferable in 18% of cases. Resistance plasmids of 92 and 99 kb were found in 27 and 15 strains respectively and encoded resistances to ampicillin, tetracycline, chloramphenicol, kanamycin, sulphonamide, trimethoprim, cotrimoxazole and gentamicin; these plasmids were usually transferable. Four plasmids of 3.9, 2.8, 2.2 and 1.8 kb were commonly found in S. flexneri strains, but were rare in other species. In contrast, there was no predominant plasmid profile in S. sonnei. S. flexneri is endemic in Hong Kong and these plasmid studies suggest that the strains in circulation are derived from only a few clones.     

Genetic analysis of antibiotic-resistance determinants in multidrug-resistant Shigella strains isolated from Chilean children

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of bla(OXA) in S. flexneri and with bla(TEM) in S. sonnei. The bla(OXA) gene but not bla(TEM) was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and bla(OXA) genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and bla(TEM), dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.     

Electropherotyping of plasmid DNA of different serotypes of Shigella flexneri isolated in Bangladesh

One hundred and twenty-five Shigella flexneri strains, isolated during January-December 1984, at the Dhaka treatment centre of the International Centre for Diarrhoeal Disease Research, Bangladesh, were serotyped using absorbed rabbit antisera specific for all type- and group-factor antigens, as well as a group of ten mouse and rat monoclonal antibodies. Electropherotypes of the plasmid deoxyribonucleic acid (DNA) were also determined. S. flexneri 2a was the predominant serotype followed by 3b, 1a, and 2b. The recently described E1037 antigen was also found in three strains of S. flexneri serotype 6. Electropherotyping of the plasmid DNA showed that three plasmids of approximately 140, 2.7, and 2 megadalton (MDa) were present, respectively, in 97, 97 and 94% of the 125 strains. Additional plasmids of various other sizes were also present in different serotypes except in serotype 2a. The additional plasmids again appeared to be specific for that particular serotype. For example, all 12 strains of S. flexneri 2b harboured an additional plasmid of approximately 1 MDa. Thus, electropherotyping of plasmid DNA of different serotypes of S. flexneri might be useful to differentiate S. flexneri from other species of Shigella and in identifying different serotypes of S. flexneri. Therefore, the common plasmids, plus the additional plasmids, could be used to identify epidemic, as well as sporadic, subclones of S. flexneri strains.     

Salmonellosis in pigmy hogs (Sus salvanius)--a critically endangered species of mammal

The pigmy hog (Sus salvanius) is the smallest and the rarest wild suid in the world. This species is on the verge of extinction and the World Conservation Union has rated it among the most endangered of all mammals. This paper reports the investigation into an outbreak of salmonellosis among captive pigmy hogs at the Research and Breeding Centre of the pigmy hog conservation programme, Guwahati, Assam, India. Of 75 pigmy hogs (38 males and 37 females) maintained at the Centre, seven (9.3%) died within five days. The causative organism associated with the outbreak was identified as Salmonella Typhimurium (syn. S. enterica serovar Typhimurium). All the isolates of S. Typhimurium belonged to phage type DT193. The isolates harboured multiple plasmids. Five isolates harboured four (65.0 MDa, 4.2 MDa, 3.0 MDa, 1.3 MDa), while two isolates carried three plasmids (65.0 MDa, 4.2 MDa, 3.0 MDa). All strains showed resistance to amikacin, ampicillin, streptomycin and sulfamerazin; five strains were resistant to oxytetracycline and trimethoprim. All the strains were sensitive to chloramphenicol, ciprofloxacin, enrofloxacin and gentamicin. All seven isolates of S. Typhimurium were found to harbour stn, sopB and pefA genes. However, none of them was found to carry sefC and sopE genes.     

Antibiotic resistance and molecular epidemiology of Shigella spp. in northeastern Argentina]

OBJECTIVES: To evaluate the antibiotic resistance of strains of Shigella spp. isolated from feces samples from northeastern Argentina and to characterize the strains in terms of their molecular epidemiology. METHODS: We studied 132 isolates of Shigella spp. obtained from feces samples from 132 patients with diarrhea who were seen at various private and public laboratories in the Argentine provinces of Chaco and Corrientes during the period of 1998 to 2002. Each strain was characterized according to its serotype, its resistance to 13 individual or combination antibiotics, and its sensitivity to pyocins. With 52 strains selected in relation to their antimicrobial susceptibility profiles we conducted plasmid profile analysis using alkaline lysis, and the repetitive extragenic palindromic sequences were determined by amplifying repetitive DNA segments using polymerase chain reaction. The chi-square test was used to compare proportions, with a level of statistical significance of 0.05. RESULTS: Shigella flexneri was the most common species (78%), followed by S. sonnei (22%). In general, the resistance of S. flexneri to the antibiotics studied was greater than that of S. sonnei, and this difference was statistically significant (P < 0.001) for ampicillin, tetracycline, chloramphenicol, and the combination of ampicillin and sulbactam. The S. flexneri strains also showed multiple resistance more often than S. sonnei strains (84.5% vs. 31.0%; P < 0.001). The strains isolated from S. flexneri were grouped into five pyocin types, three plasmid profiles, and five patterns of repetitive palindromic sequences. The strains of S. sonnei formed three pyocin types, two plasmid profiles, and three patterns of repetitive palindromic sequences. CONCLUSIONS: Given that the Shigella species that were studied showed a high level of resistance to the most frequently used antibiotics, surveillance activities should be implemented in order to detect and control the appearance of new resistant strains. Applying epidemiological typing techniques can provide more precise information about the distribution and evolution of resistant strains of circulating microorganisms.     

Development of antimicrobial drug resistance among Shigellas isolated at an Israeli hospital from 1977 through 1990

BACKGROUND: Treatment of diarrhea due to Shigella sp. has become complicated in recent years by drug resistance. The emergence of resistance to antibiotics important in the treatment of shigellosis was studied among Shigella sp. isolated at the Sheba Medical Center between 1977 and 1990. METHOD: A retrospective study of resistance patterns of Shigella sp. using the Kirby-Bauer disc diffusion test. RESULTS: In the early 1980s S. sonnei replaced S. flexneri as the most frequent isolate. Ampicillin resistance rose steadily, peaking at 70% for S. sonnei in 1990 and 50% for S. flexneri in 1987 and 1990. Resistance to tetracycline roughly paralleled this. By 1990, 68% of S. sonnei and 75% of S. flexneri were insensitive. Cotrimoxazole resistance developed rapidly from 1981. By 1990, 88% of strains of S. sonnei had become resistant, compared to 63% of S. flexneri. S. boydii and S. dysenteriae were encountered less frequently, but showed important rates of resistance. Chloramphenicol remained active against almost all strains of S. sonnei, while resistance in S. flexneri reached about 30% in the late 1980s. Relatively few isolates were resistant to all four drugs. Only 20/841 (2.4%) of strains tested from 1984 to 1990 were resistant to nalidixic acid. CONCLUSION: The data presented document the emergence of antibiotic resistance as a serious public health problem among strains of Shigella isolated at a large medical center in Israel.     

Estimating the burden of shigellosis in Thailand: 36-month population-based surveillance study

OBJECTIVE: To estimate incidence of shigellosis in the Kaengkhoi district, Saraburi Province, Thailand. METHODS: Population-based surveillance of shigellosis based in treatment centres. The detected rates of treated shigellosis were corrected for the number of cases missed due to the low sensitivity of microbiological culture methods and participants' use of health-care providers not participating in the study. FINDINGS: The overall uncorrected incidence of shigellosis was 0.6/1000 population per year (95% confidence interval (CI) = 0.5-0.8). The unadjusted incidence of treated shigellosis was highest among children less than 5 years old (4/1000 children per year; 95% CI = 3-6) and significantly lower among people aged > 5 years (0.3/1000 population per year; 95% CI = 0.2-0.5; P < 0.001). Adjusting for cases likely to be missed as a result of culture and surveillance methods increased estimates approximately five times. The majority of Shigella isolates (122/146; 84%) were S. sonnei; the rest were S. flexneri. Of the 22 S. flexneri isolates, the three most frequently encountered serotypes were 2a (36%), 1b (23%) and 3b (28%). A total of 90-95% of S. sonnei and S. flexneri isolates were resistant to tetracycline and co-trimoxazole. In contrast to S. sonnei isolates, more than 90% of the S. flexneri isolates were also resistant to ampicillin and chloramphenicol (P < 0.0001). CONCLUSION: Estimates of incidence of Shigella infection in the community are 10-fold to 100-fold greater than those found from routine government surveillance. The high prevalence of Shigella strains resistant to multiple antibiotics adds urgency to the development of a vaccine to protect against shigellosis in this region of Thailand.     

Shifting serotypes,plasmid profile analysis and antimicrobial resistance pattern of shigellae strains isolated from Kolkata,India during 1995-2000

One hundred and sixty-six shigellae strains, isolated from stool samples of paediatric patients (< 5 years old) at a Childrens' Hospital in Kolkata, India during the period of 1995-2000 were examined for serotyping, drug resistance pattern and plasmid profiles. Sh. flexneri (58 %) was found to be commonest isolate of total shigellae, followed by Sh. sonnei (28 %), Sh. boydii (9%) and Sh. dysenteriae (5%). This profile of species was in sharp contrast to the picture obtained before 1995, when Sh. dysenteriae 1 predominated over Sh. flexneri. In Sh. flexneri strains, Sh. flexneri 2a (35%) was the most prevalent serotype, following Sh. flexneri 3a (31%), Sh. flexneri 6 (14%), Sh. flexneri 2b (11%) and Sh. flexneri 4 (9%). Resistance patterns of the strains to 12 commonly used antimicrobial agents and minimum inhibitory concentrations (MICs) of the antibiotics were also tested. All strains were found uniformly susceptible to norfloxacin, but more than 90% strains were resistant to tetracycline, co-trimoxazole and 67% strains were resistant to ampicillin. Resistance to amoxicillin, chloramphenicol and nalidixic acid was found in 55% (range 45-74%), 46% (range 40-60%) and 29% (range 15-40%) strains respectively. Overall, shigellae strains showed statistically significant increase in resistance against tetracycline, nalidixic acid and furazolidone (P < 0.05) over the years of this study. This indicates decreased efficacy of furazolidone, cotrimoxazole and nalidixic acid for the empirical treatment of shigellosis in Kolkata. Although a few strains showed intermediate susceptibility to ciprofloxacin (4%) and cefotaxime (10%) by disk diffusion test, but the MICs of those antibiotics were within the normal limits. Almost 57% of the strains were resistant to four or more drugs with high MICs of the antibiotics. Plasmid profile analysis revealed presence of large plasmid of 220 kb in majority of the strains except in Sh. sonnei and a correlation between presence of smaller plasmids and shigellae serotypes. Hence this study reports epidemiological change of shigellae species in Kolkata, India with regard to serotypes and antibiotic resistance patterns.     

Plasmid profiles of antibiotic-resistant Shigella dysenteriae types 2, 3, 4, 6 and 7 isolated in Ethiopia during 1976-85.

Plasmid profile analysis by agarose gel electrophoresis was carried out on 37 drug-resistant strains of Shigella dysenteriae types 2, 3, 4, 6 and 7. These strains were collected between 1976 and 1985 in Addis Ababa, Ethiopia. The plasmid profile of S. dysenteriae type 2 strains with R-type CSSuT did not show middle-sized plasmids likely to code for CSSuT resistance. All strains contained a large plasmid of about 120 megadaltons (MDa), and a cryptic plasmid of about 2.2 MDa. The plasmid profiles of S. dysenteriae type 3 with R-types ACSSuT, SSuT and SSu showed a 4.2 MDa SSu-determinant, which was demonstrated in Escherichia coli K12 recipients resulting from triparental crosses. The ACT determinant in S. dysenteriae type 3 with R-type ACSSuT is probably chromosomally mediated. Cryptic plasmids of about 3.0 and 2.2 MDa were found in all S. dysenteriae type 3 isolates. The 4.2 MDa plasmid featured prominently in the plasmid profiles of S. dysenteriae types 4, 6 and 7 with R-types SSuT and SSu. However, this plasmid was not mobilizable by triparental crosses. There was a relative paucity of transferable plasmids in non-Shiga bacillus isolates. However, incompatibility group N plasmids, coding for tetracycline resistance, were detected.     

Molecular characterization of trimethoprim resistance in Shigella sonnei in Sicily

During the 3-year period 1985-7, all strains of Shigella sonnei isolated in Catania, Sicily, showed a high level of resistance to trimethoprim (Tp) which was invariably associated with resistance to other antibiotics. Plasmid analysis showed 18 different electropherotypes: 35 of 37 strains harboured a plasmid of 70 Megadaltons (MDa), and 29 of 37 strains a plasmid of 130 MDa. Restriction endonuclease fingerprinting of purified 70 MDa plasmid DNA from different strains demonstrated that these plasmids were similar but not identical. In some strains with transferable Tp resistance, DNA hybridization analysis demonstrated the presence of gene coding for the production of dihydrofolate reductase (DHFR) type V. In contrast, there was no detectable hybridization with DNA probes specific for genes coding for DHFR types I, II and IV. This is the first report of the DHFR type V gene outside Sri Lanka.     

福建省2005～2006年细菌性痢疾病原学监测结果分析

目的:了解福建省志贺菌属感染的病原学特征及药敏特点,为细菌性痢疾的防治和临床合理用药提供依据。方法:复核鉴定监测点送检的阳性菌株,按《全国细菌性痢疾监测方案》提供的方法进行系统检测。结果:两年共复核鉴定阳性菌株70株,检出志贺菌49株,其中宋内志贺菌34株,福氏志贺菌15株,分别占检出菌株数的69.4%和30.6%。药敏试验显示,49株志贺菌对头孢噻肟及环丙沙星高度敏感,全部耐药药物为四环素、利福平及复方新诺明。结论:2005～2006年福建省分离的菌株以宋内志贺菌所占比重较大,其次为福氏志贺菌,并对目前常用的抗菌药物表现一定的耐药性,应引起重视。     

甘肃省2005年-2011年志贺菌菌型变迁及耐药性监测分析

目的:为了解志贺菌属腹泻在甘肃省的流行、变迁及耐药状况。方法:于2005年-2011年对兰州市、武威市细菌性痢疾监测点分离菌株和2起幼儿园食物中毒分离的宋内氏志贺菌株进行了血清型分型及菌株耐药性分析。结果:7年共采样4546份,分离到志贺菌773株,阳性率为17.00%。血清型以福氏志贺菌(B群)居优势514株,占66.49%,其次为宋内氏志贺菌(D群)256株,占33.12%。分离菌株对10种抗生素耐药率增高,为多重耐药,耐药种类达10种。结论:甘肃省细菌性痢疾菌群仍然是腹泻的首要病原,不同年份血清型、菌株的耐药率有所差异。     

Diversity of plasmids in Staphylococcus saprophyticus isolated from urinary tract infections in women

A group of 150 Staphylococcus saprophyticus strains isolated from urinary tract infections in women were included in this study. Antimicrobial susceptibility tests showed that these isolates were sensitive to most antimicrobial agents. All strains were sensitive to penicillin, cephalothin, gentamicin, kanamycin, trimethoprim and nitrofurantoin. Resistance to tetracycline was present in 10.6% of the strains, to chloramphenicol in 4%, to erythromycin in 1.3% and to streptomycin in 1.3%. All strains were resistant to cadmium chloride as well as to novobiocin and nalidixic acid. Plasmid analysis showed that 82% of the strains harboured plasmids, some of them with complex plasmid profiles. Most plasmids were considered to be cryptic, although antibiotic resistance plasmids were identified in 18 isolates. Tetracycline resistance was encoded by a plasmid of c. 2.8 MDa, chloramphenicol resistance by a plasmid of c. 2.9 MDa and erythromycin resistance by a plasmid of c. 1.6 MDa. Streptomycin resistance could not be linked to the presence of any specific plasmid. Plasmid profiling seemed to be a good method for differentiating among S. saprophyticus strains.     

江苏省2008年～2009年志贺菌菌型分布及耐药性分析

目的：了解江苏省2008年～2009年志贺菌菌型分布及耐药性情况,为菌痢防控提供依据。方法：通过系统生化条鉴别菌株,用血清玻片凝集鉴定菌型,K-B法确定药物敏感性。结果：498株志贺菌中福氏志贺菌344株,其中F2a占36.16%;宋内氏志贺菌150株,鲍氏志贺菌4株。药敏实验结果显示,萘啶酸耐药率最高,为73.69%,其次为四环素（72.89%）,氨苄西林、复方新诺明耐药率均〉50%。〉58.23%的志贺菌对9种抗生素中的5种以上具有耐药性。两年中志贺菌对大部分常用药物抗性都有所增加。结论：2008年～2009年江苏省志贺菌流行菌型为F2a,宋内氏志贺菌检出率显著升高;志贺菌对萘啶酸耐药率最高,多重耐药现象日趋严重。     

Antimicrobial resistance of Shigella spp. in Córdoba, Argentina, during the period 1990-1997]

This study analyzed the evolution of antimicrobial resistance in 771 isolates of Shigella spp. obtained from a total of 9,195 feces cultures done between 1990 and 1997 in a children's hospital in Córdoba, Argentina. S. flexneri, which was responsible for 73% of the Shigella infections, was the species with the greatest resistance. The frequency of S. flexneri resistance to the three antibiotics most used (ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol) increased from 10% in 1990 to 58% in 1997 (P < 0.001). Considering each of the drugs individually, the resistance to ampicillin increased from 60% to 100% (P < 0.001), the resistance to chloramphenicol from 13% to 71% (P < 0.001), and the resistance to trimethoprim-sulfamethoxazole from 79% to 84% (P = 0.22). For S. sonnei, the increase in resistance to ampicillin (from 36% in 1990 to 54% in 1997) was not statistically significant (P = 0.20), nor was the reduction in resistance to trimethoprim-sulfamethoxazole, which went from 82% in 1990 to 55% in 1997 (P = 0.08). Only two S. sonnei isolates were found that were resistant to chloramphenicol, one in 1995 and another in 1997; two S. sonnei isolates were found with resistance to all three antibiotics. We consider it essential to carry out susceptibility tests of each Shigella clinical isolate, to detect changes in the resistance profile and thus modify empiric treatment.     

The prevalence and genetics of resistance to commonly used antimicrobial agents in faecal Enterobacteriaceae from children in Bangladesh.

The present study was undertaken to investigate the occurrence of antibiotic resistance in enteric flora in 64 children in rural Bangladesh over a 12-month period. The antibiotic resistance pattern of the isolates varied throughout the year and multiple resistance was highest during the post monsoon period. Seventy-three percent of children had isolates resistant to more than three antibiotics throughout the year. Resistance to streptomycin was highest (78%), followed closely by ampicillin (72%). Of 82 multiply resistant isolates, plasmid DNA was demonstrated in 75%. Plasmid sizes ranged between 3.7 and 110 MDa, the commonest plasmids were of 70, 98 and 110 MDa. Complete or partial resistance was transferred by conjugation from 52% of the isolates, most frequently by single plasmids. The commonest plasmid incompatibility group was F11-A (46%) followed by incompatibility group P (22%). Plasmids of molecular weight 98 MDa most often hybridized with F11-A probes and those of 110 MDa with H11 probes. Plasmids from 10 transconjugants were digested with restriction enzymes and digest patterns demonstrated the presence of common plasmids. The findings show that there is a diverse, and mobile, genetic pool of resistance genes in this rural community. This genetic reservoir is potentially transferable to enteric pathogens, with major implications for public health and diarrhoeal disease control.     

Salmonella and Shigella in adult diarrhoea in Addis Ababa--prevalence and antibiograms

Ninety Shigella and 45 Salmonella strains were isolated from 1000 adult diarrhoeal out-patients from various hospitals and clinics in Addis Ababa. The Shigella species were isolated in the order of frequency of S. flexneri, S. dysenteriae, S. boydii and S. sonnei and the Salmonella in the order of Group C, Group B, S. typhi, other Group D and Groups A and E. Almost all Shigella isolates were sensitive to cephalothin, gentamicin, kanamycin, polymyxin B and trimethoprim-sulphamethoxazole. About 17% were sensitive to the 11 drugs tested. Multiple resistance was detected in 62%, the most common to six drugs (27%). All Salmonella isolates were sensitive to gentamicin, polymyxin B and trimethoprim-sulphamethoxazole. About 69% were sensitive to all drugs tested. 22% were multiply resistant and the most common was to eight drugs (18%).     

High level resistance to trimethoprim, cotrimoxazole and other antimicrobial agents among clinical isolates of Shigella species in Ontario, Canada--an update.

A total of 598 isolates of Shigella species (24 S. dysenteriae, 254 S. flexneri, 30 S. boydii, 290 S. sonnei) submitted to the Ontario Public Health Laboratories in 1990 were tested for their susceptibility to 14 antimicrobial agents by the agar dilution method. Overall 79.6% of isolates were resistant to one or more antimicrobial agents and 52.0% were resistant to four or more. Trimethoprim resistance ranged from 26.7% among isolates of S. boydii to 39.4% among S. flexneri strains. The majority of the 224 TMP resistant isolates (88.8%) demonstrated high level resistance (MIC > 1000 mg/l) to trimethoprim. Resistance to cotrimoxazole increased from 3% in 1978 to between 26.7 and 37.6% in 1990. MICs for 90% of isolates (MIC90s) for ampicillin, ticarcillin and piperacillin were 128 to > 256 mg/l, > 256 for tetracycline and chloramphenicol, and > 2.0/38.0 for cotrimoxazole. These results from the Canadian Province of Ontario emphasize the need for prudent use of antimicrobial agents in the treatment of shigellosis.     

Emergence of highly trimethoprim-sulfamethoxazole-resistant Shigella in a native American population: an epidemiologic study

Resistance to trimethoprim-sulfamethoxazole (TMP-SMX) emerged among Shigella isolates from the Navajo Reservation in the southwestern United States in 1985, years after this antimicrobial agent came into common use. In the study area, TMP-SMX resistance increased dramatically from 3 per cent in 1983 to 21 per cent in 1985. Resistance was polyclonal and occurred in both S. sonnei and S. flexneri. No single plasmid was common to all resistant strains. However, all 28 TMP-SMX resistant isolates examined were resistant to ampicillin and streptomycin and had minimum inhibitory concentrations to sulfamethoxazole of greater than or equal to 4,096 micrograms/ml and to trimethoprim of greater than or equal to 1,024 micrograms/ml. The authors found that 28 of 101 Navajo children with gastrointestinal symptoms who were not taking antimicrobials had TMP-SMX-resistant aerobic fecal flora. To determine risk factors for acquiring resistant strains, they compared 40 case-patients with TMP-SMX-resistant Shigella to 66 controls with TMP-SMX-sensitive Shigella. Case-patients were more likely than controls to have used antimicrobials recently (p = 0.004) and to be hospitalized for shigellosis (p = 0.05). These findings suggest that polyclonal highly TMP-SMX-resistant Shigella emerged by transfer of trimethoprim resistance genes from aerobic bowel flora to endemic Shigella strains, that use of antimicrobials can lead to symptomatic shigellosis and thus the persistence of trimethoprim-resistant Shigella, and that appropriate therapy of shigellosis on the reservation is now a major challenge.     

Genetic diversity of Shigella species from different intercontinental sources

One hundred and twenty three strains of Shigella spp. (mostly Shigella sonnei and Shigella flexneri) were isolated between 1995 and 2000 from patients suffering from traveller's diarrhoea. Seventy nine of them have been typed by digestion of their chromosomal DNA with Xba I and pulsed field gel electrophoresis. Results show a high degree of heterogeneity in both S. sonnei and S. flexneri isolates. This is the first time that the molecular typing of such a high number of geographically unrelated isolates of Shigella sp. is carried out, showing a high level of genomic re-arrangement.