Antimicrobial resistance patterns and prevalence of integrons in Shigella species isolated from children with diarrhea in southwest Iran

Objective: To investigate the antimicrobial resistance patterns and prevalence of integrons in Shigella species isolated from children with diarrhea in southwest Iran.Methods: In this study, 1 530 stool samples were collected from children under 15 years with diarrhea referred to teaching hospitals in Ahvaz and Abadan, southwest Iran. Shigella spp. were identified by standard biochemical tests and PCR. The antibiotic resistance pattern of all Shigella isolates was determined by the disk diffusion method and minimum inhibitory concentration(MIC) by E-test. Results: Of 1 530 stool samples, 91(5.9%, 91/1 530) were positive for Shigella spp. the most common Shigella isolates were Shigella flexneri 47(51.6%, 47/1 530). Antibiotic susceptibility tests showed that the highest antibiotic resistance was related to trimethoprimsulfamethoxazole(87.9%, 80/91) and ampicillin(86.8%, 79/91). Multiplex PCR results revealed that 56% and 86.9% of Shigella isolates carried integron classⅠand integron classⅡ genes, respectively. None of the isolates included the integron class Ⅲ gene. Conclusions: The high prevalence of multi-drug resistance in Shigella isolates in our area increases the concerns about dissemination of the antibiotic-resistant isolates in this bacterium.     

Changing patterns of antimicrobial susceptibility of Shigella serotypes isolated from children with acute diarrhea in Manipal, South India, a 5 year study

This study was carried out to determine the current pattern of Shigella serogroups and their antimicrobial resistance in children with acute gastroenteritis in Manipal, South India. A total of 1,200 stool samples were collected from April 2001 to May 2006 in children suffering from acute gastroenteritis attending the out-patient department of pediatrics at Kasturba Hospital, Manipal, South India. These samples were cultured for enteric pathogens. The isolates were confirmed to be Shigella by biochemical reactions and slide agglutination tests using specific antisera. Antimicrobial susceptibility was performed using an agar diffusion technique method following the National Committee for Clinical Laboratory Standard guidelines. Of 1,200 stool samples, 68 (5.6%) were positive for Shigella spp, 31 (45%) were Shigella flexneri followed by S. sonnei in 20 (31%), S. boydii in 10 (15%), and S. dysenteriae in 6 (8%). Of the 68 isolates, 58 (85.7%) showed resistance to various drugs and 47 (70%) were resistant to two or more drugs. Resistance to trimethoprim-sulfmethoxazole, tetracycline, nalidixic acid and ampicillin was observed in this study. All the strains were resistant to nalidixic acid (100%) but sensitive to cefotaxime and ceftriaxone.     

Antibiotic resistance among Shigella species isolated in Tehran, Iran

A study of adult patients with gastroenteritis was carried out over an 18-month period from March 1984 until August 1985, with the aim of detecting Shigella species and studying their antibiotic resistance pattern. Two thousand four hundred and eighteen stool specimens were examined and 230 isolations of Shigella were made, a detection rate of 9.5%. Of the 230 isolates, 61.2% were found to be Sh. flexneri, and resistance to ampicillin, chloramphenicol, co-trimoxazole and tetracycline was extremely high, varying from 47% of isolates for chloramphenicol to 77% for tetracycline. Resistance to nalidixic acid was not encountered. In view of the fact that this disorder tends to be a self-limiting condition in Iran, it is advisable to be selective and cautious in the use of antibiotics for treatment.     

Subtype prevalence, plasmid profiles and growing fluoroquinolone resistance in Shigella from Kolkata, India (2001-2007): a hospital-based study

Objectives Shigellosis is a major public health problem, and increasing antimicrobial resistance has complicated its treatment. We report isolation frequency, plasmid profiles and antimicrobial resistance of Shigella subtypes in Kolkata, India, from a prospective hospital‐based study. Methods Fresh stool or rectal swabs were collected from children (<5 years) attending the Diarrhea Treatment Unit of a governmental paediatric referral hospital in Kolkata. Samples were processed following standard methods over a 7‐year period from January 2001 to December 2007. Results Of 4478 samples collected, 516 (11.5%) were positive for Shigella spp. S. flexneri (312; 6.9%) was the most frequently isolated serogroup, ranking before S. sonnei (123, 2.7%), S. dysenteriae (48, 1.1%) and S. boydii (33, 0.7%). Although 10 subtypes of S. flexneri were identified, the common ones circulating locally were S. flexneri 2a (179), S. flexneri 6 (38) and S. flexneri 3a (36). Knowledge of Shigella subtypes is important for vaccine development. The majority of Shigella isolates (81.0%) were multidrug (two or more antimicrobial classes) resistant and showed high minimum inhibitory concentration (MIC) with commonly used drugs like ampicillin, tetracycline, co‐trimoxazole and nalidixic acid. Emergence of fluoroquinolone (FQ)‐resistant S. dysenteriae type 1 (100.0%) in 2002–2003 was followed by frequent isolation (>25.0%) of FQ‐resistant S. flexneri 2a, and S. flexneri 3a in 2004, which restricted use of fluoroquinolones for treatment. A number of smaller plasmids (<20 kb) with distinct patterns have been observed for several years in predominant subtypes. Conclusion Long‐term surveillance of Shigellae and their antimicrobial resistance are mandatory in endemic areas to formulate treatment policy until any suitable candidate vaccine is available to control the disease.     

Distribution of Shigella enterotoxin genes and secreted autotransporter toxin gene among diverse species and serotypes of shigella isolated from Andaman Islands, India

We studied the prevalence and distribution of the newly described genes for Shigella enterotoxins (ShET1 and ShET2, encoded by set and sen genes) and secreted auto-transporter toxin (encoded by sat gene) in clinical isolates from the Andaman Islands, India. A total of 153 Shigella isolates obtained from hospitalized patients during 1994-2004 were analysed. These isolates included all the four species of Shigella (S. dyseteriae-29, S. flexneri-75, S. sonnei-38, S. boydii-5) that belonged to diverse serotypes (including serologically untypable-6) and each serotype included a wide variety of genotypes. Each isolate underwent polymerase chain reaction (PCR) for detection of set, sen and sat genes employing specific primers. We found the set gene in all S. flexneri 2a and 2b isolates (41 of 41, 100%) but not outside S. flexneri serotype 2. The sen gene was well distributed among all species and serotypes but its presence was apparently low at 49.1% (75 of 153), probably because of the loss of the large plasmid that harbours the gene in 76 of the 78 (97.4%) sen negative isolates. Also, all S. flexneri 2 isolates (including 2a and 2b serotypes) had the sat gene. It was present in 96% (72 of 75) of S. flexneri, in 6.9% (2 of 29) of S. dysenteriae, in 20% (1 of 5) of S. boydii, and in 33.3% (2 of 6) of untypable Shigella, but not in (0 of 38) S. sonnei. This study provides initial data on the prevalence and distribution of of the set, sen and sat genes in a wide variety of Shigella isolated over a 10-year period. Our results suggest a greater prevalence of the set and sat genes in S. flexneri 2 isolates than previously thought and might help in future pathochip designs.     

Seasonal prevalence of Aedes aegypti immatures in Kolkata, India

Dengue and dengue hemorrhagic fever (DHF) is recurring in India in recent years, affecting many cities including Kolkata (Calcutta). In view of this, a survey of three years was carried out on the prevalence of immatures of the vector mosquito Aedes aegypti in the city of Kolkata. Mosquito immatures were found throughout the year with fluctuating densities in the habitats surveyed. An index of density of immatures (I/S)m employed in the study revealed that in the months of August and September a peak in abundance occurs, irrespective of the habitats, with the values ranging between 1.12 and 11.4. The (I/S)m values were low during the months of April and May ranging between 0.4 and 3.8. As larval habitats, earthen containers and the sewage drains were positive throughout the year, while during the months of December to February, air-coolers and conditioners as habitats remained totally dry, without immature Ae. aegypti. The number of positive sites and monthly density between the habitat types were significantly different with an I/S- value (for a year) ranging between 2.64 (air-coolers) and 4.97 (earthen containers). The survey, while providing preliminary baseline data on immature abundance in Kolkata, calls for continuous entomological surveillance using standard protocols as carried out in Thailand for the vector management program against dengue.     

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.     

Multiresistant Shigella species from African AIDS patients: antibacterial resistance patterns and application of the E-test for determination of minimum inhibitory concentration.

The antibacterial resistance pattern and minimum inhibitory concentrations (MIC) of 25 Shigella flexneri, 5 S. boydii, 8 S. sonnei, and 3 strains of S. dysenteriae type 2 isolated from Kenyan prostitutes with bacillary dysentery and AIDS were determined, and the applicability of the E-test for MIC determination evaluated. All strains were resistant to > or = 3 of 9 different antibacterial agents tested. All strains were resistant to tetracycline and erythromycin, 95% to trimethoprim/sulfonamide, 93% to streptomycin, 54% to ampicillin, 39% to chloramphenicol, 2% to nalidixic acid and none to gentamicin and ciprofloxacin. Six different resistance patterns were observed. The most common pattern was resistance to tetracycline, erythromycin, trimethoprim/sulfa and streptomycin (39%). The E-test was shown to be well-suited for susceptibility testing of multiresistant Shigella spp.; the reproducibility was excellent and the correlation with the microtiter dilution method and the disk diffusion method were 98% in both instances. The MIC measured with E-test and the microdilution method were within +/- 1 dilution step for 94.4% of the combinations tested.     

Shigella dysenteriae strains having a provisional serovar isolated from imported diarrheal cases in Tokyo]

Two bacterial strains (ME448 and ME474) isolated from stool cultures of imported cases in Tokyo in 1987 had typical biochemical characteristics of Shigella dysenteriae. The results of antigenic analyses showed that they were serologically identical to each other, but did not belong to any of the established Shigella serovars. These strains were positive for Serény test in guinea pig eye and cell-invasion test in HeLa cells. The strains also had virulence-plasmid encoding outer membrane proteins, indicating that they were pathogenic. We then contacted the Centers for Disease Control in the United States and the Central Public Health Laboratory in the United Kingdom and arranged serological examinations of the strain ME448. From the results, the strain was confirmed to have provisional S. dysenteriae serovar E23507. Although the serovar had been isolated from a Swedish patient who developed diarrhea while in India, this is thought to be the first report of its isolation in Japan.     

Emergence of tetracycline-resistant Vibrio cholerae O1 serotype Inaba, in Kolkata, India

Out of 2,235 diarrheal stool samples collected from patients admitted to the Infectious Diseases Hospital, Kolkata, 343 cases were positive for Vibrio cholerae (341, V. cholerae O1 and 2, O139). During the year 2004, infections caused by V. cholerae serotype Ogawa and Inaba were 93 and 7%, respectively, while in 2005, the Inaba isolation rate rose to 88% as compared to 12% for Ogawa. Susceptibility to antimicrobial agents revealed that the O1 strains were resistant to multiple antibiotics (ampicillin, co-trimoxazole, furazolidone, nalidixic acid and streptomycin) with reduced susceptibility to ciprofloxacin. Increased isolation of tetracycline-resistant strains (27.3% for Ogawa and 15% for Inaba) was noted in 2005. It appears that the population might be at risk of infection by the Inaba serotype and that tetracycline may not be useful for the treatment.     

Shigella boydii strains possessing a new serovar (SM00-27) isolated from diarrhea of overseas travelers in Japan

Five Shigella strains isolated from stool cultures of five sporadic imported diarrheal cases in Japan during 1999-2001, did not react to any antisera of the established Shigella serovars. These strains had the typical biochemical characteristics of Shigella boydii, and were biochemically identical. All strains were positive in a PCR assay and a cultured-cell invasion test for invasiveness; these indicate that they can cause shigellosis in humans. The results of antigenic analysis revealed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable. Strain SM00-27 is designated as the test strain for this new S. boydii serovar.     

Shigella dysenteriae type 1-induced diarrhea in rats

With the aim of setting up an animal model of Shigella dysenteriae-induced diarrhea, Wistar rats received per os increasing densities of S. dysenteriae type 1 (Sd1). Inoculum of 12 x 10(8) Sd1 provoked dysenteric diarrhea within 24 h. Feces of healthy rats were molded, brown to black and rough. Rats developing diarrhea presented blood at the anal orifice; stools were soft or liquid containing mucus, or molded, smooth and mucus-coated. At times, stools appeared longer, dark and shiny due to the presence of mucus and blood, or molded, lumpy and brittle. Diarrheal induction was associated with abdominal ailment, progressive increase in stool weight and frequency, and increase in bacterial population. Sixty-seven percent of the total number of deaths had occurred by day 6 after diarrheal induction. These results indicate that Sd1 induced in rats a model of shigellosis which might be helpful for physiopathological and pharmacological studies of this type of infectious diarrhea.     

HIV Transmission Potential Among Local and Migrant Factory Workers in Kolkata, India

Migrant workers in India play a key role in the spread of HIV. Kolkata is a common destination for workers, who may acquire infection and transmit it to their wives and/or other sexual partners. We investigated sexual relations and condom use by factory workers. Migrant and local factory workers were randomly selected from five wards of Kolkata. Information was collected about demographic and socio-economic characteristics, sexual relationships, condom usage, and perceptions and intent to use condoms. Condom use was very low in both groups of workers, particularly among migrants. Many married workers visited female sex workers but never used condoms. Few intended to use condoms, and if they did, it did not always translate into actual usage. There is great potential for transmission of HIV/sexually transmitted infections by these workers. Carefully designed intervention and education programs in the context of low literacy and cultural norms are urgently needed.