Mutation and Efflux System are Responsible for Ciprofloxacin Resistance in Klebsiella pneumoniae / Las mutaciones y el sistema de eflujo son responsables de la resistencia a la ciprofloxacina en la Klebsiella pneumoniae

ABSTRACT The main mechanism of quinolone resistance in Klebsiella (K) pneumoniae is caused by mutation of porin-related proteins and efflux pumps. This study aimed to investigate the prevalence of ciprofloxacin-resistant K pneumoniae in burns patients and to understand the role of the AcrAB multidrug efflux system on minimal inhibitory concentration (MIC) of ciprofloxacin. For this reason, 52 K pneumoniae samples were collected from burns patients and evaluated for the mechanism of ciprofloxacin resistance. The results demonstrated that 40 isolates of K pneumoniae were ciprofloxacin-resistant and 35 showed the mutation on gyrA locus. By inhibition of the efflux system, the MIC yield showed a significant decrease. Therefore, it could be concluded that the high rate of mutation on the gyrA locus in combination with quinolone resistance was responsible for ciprofloxacin resistance and by inhibition of AcrA, the resistance rate showed a significant decrease in K pneumoniae isolated from burns patients.

RESUMEN El principal mecanismo de resistencia a la quinolona en las Klebsiella (K) Pneumoniae tiene como causa la mutación de las porinas y las bombas de eflujo. Este estudio tuvo por objetivo investigar la prevalencia de las K pneumoniae resistentes a la ciprofloxacina en pacientes con quemaduras, así como entender el papel del sistema de eflujo multidroga AcrAB en la concentración inhibitoria mínima (CIM) de la ciprofloxacina. Por esta razón, se recogieron 52 muestras de K pneumoniae de pacientes con quemaduras, a fin de evaluar el mecanismo de resistencia a la ciprofloxacina. Los resultados mostraron que 40 aislados de K pneumoniae eran resistentes a la ciprofloxacina y 35 mostraron la mutación en el locus gyrA. Con la inhibición del sistema de eflujo, el rendimiento de CIM tuvo una disminución significativa. Por lo tanto, se pudo concluir que la alta tasa de mutación en el locus gyrA en combinación con la resistencia a la quinolona era responsable de la resistencia a la ciprofloxacina, y por la inhibición de AcrA, la tasa de resistencia mostró una disminución significativa en las K pneumoniae aisladas de los pacientes con quemaduras.

PFGE genotyping and molecular characterization of Campylobacter spp. isolated from chicken meat.

A total of 70 samples were collected from chicken meat obtained from 10 markets in Tehran, Iran from which 39 Campylobacter coli were isolated. Among 10 antibiotics used, maximum resistance was seen to trimethoprim-sulphamethoxazole (SXT) (97.36%), nalidixic acid (94.8%), ciprofloxacin (87.7%), streptomycin (89.72%), and tetracycline (97.4%). No resistance was to gentamycin was observed. None of the Campylobacter strains under study harbored integron, suggesting the involvement of other resistance mechanisms in emergence of multi drug resistance (MDR) phenotype among the isolates. Two major types (A and B) and 15 subtypes (A1-A8 and B1-B7) were identified. Pulsed-field gel electrophoresis (PFGE) analysis demonstrated a high degree of homogeneity while the majority of the isolates shared identical or very similar PFGE genotypes. Isolates with identical genotypes differed in their resistance profile, although all of them assigned to MDR phenotype. To our knowledge, this is the first molecular survey from Iran characterizing Campylobacter isolates from poultry, which adds to our knowledge the epidemiological linkage of Campylobacter isolates with MDR properties from different sources and emphasizes the need for cautious use of antimicrobials in different fields of food production chain.

Antimicrobial resistance pattern and genetic correlation in Enterococcus faecium isolated from healthy volunteers.

Enterococci are known as a cause of nosocomial infections and this aptitude is intensified by the growth of antibiotic resistance. In the present study, Enterococcus faecium isolates from healthy volunteers were considered to determine the antibiotic resistance profiles and genetic correlation. A total 91 normal flora isolates of enterococci were included in this study. Identification of Enterococcus genus and species were done by biochemical and PCR methods, respectively. Sensitivity for 10 antibiotics was determined and genetic relatedness of all isolates was assessed using Repetitive Element Palindromic PCR (REP-PCR) followed by Pulse Field Gel Electrophoresis (PFGE) on the representative patterns. None of the isolates were resistant to teicoplanin, vancomycin, quinupristin-dalfopristin, linezolid, chloramphenicol, ampicillin and high-level gentamicin. On the other hand, the resistance rate was detected in 30.7%, 23%, and 3.29% of isolates for erythromycin, tetracycline and ciprofloxacin, respectively. The results of PFGE showed 19 (61.5% of our isolates) common types (CT) and 35 (38.5%) single types (ST) amongst the isolates. This is the first study to describe antibiotic resistance pattern and genetic relationship among normal flora enterococci in Iran. This study showed no prevalence of Vancomycin Resistant Enterococci (VRE) and high degrees of diversity among normal flora isolates by genotyping using PFGE.

Suicidal behavior by burns among women in two bordering provinces in Iran.

The objective of the study was to describe epidemiologic features of suicidal behavior by burns among women in two bordering provinces in Iran. A prospective hospital-based study of all suicidal behaviors by burns among women was carried out in the Iranian provinces of Khorasan (which borders Afghanistan) and Ilam (which borders Iraq) in 2006. These two provinces suffered from war and economic instability with high rates of poverty and unemployment. Data were obtained from patients, family members, and/or significant others through interviews during the course of hospitalization. Of 181 hospitalized patients, 130 (71.8%) were female, representing a hospital separation rate of 5.4 per 100,000 person-year (P-Y). The rate of suicidal behavior involving burns among the rural population was higher than that in the urban population (6.3 vs. 4.7 per 100,000 P-Y, P = 0.09). The median age of the patients was 23 years old, with a mean (±SD) of 27.9 (±14.3) years old. Approximately 68.5% of women were married. Quarrels with "a family member, spouse, a relative, or a friend" (marital plus other conflicts) was identified as the most common precipitating factor (88.5%) in attempting suicide. More than one third of women were abused (physically and/or verbally) by family members (i.e. spouse, father-in-law). Case fatality rate in this study was 52.3% (68/130). Suicide by burns is still a socio-epidemiological problem in Iran, particularly among young, married women in rural areas. Social and economic conditions, as well as violence against women, play a major role in the high rate of suicide by burns. The findings of this study highlight the need for the implementation of a well-organized approach to reduce the rate of suicide by burns among the most vulnerable populations in Iran.

L'objectif de l'étude était de décrire les caractéristiques épidémiologiques de comportements suicidaires par brûlures chez les femmes dans deux provinces frontalières de l'Iran. Une étude prospective en milieu hospitalier de tous les phénomènes suicidaires par brûlures chez les femmes a été réalisée dans les provinces iraniennes du Khorasan (qui borde l'Afghanistan) et Ilam (frontalière de l'Irak) en 2006. Ces deux provinces ont souffert de la guerre et de l'instabilité économique avec des taux élevés de pauvreté et de chômage. Les données ont été obtenues à partir de patients, membres de la famille et / ou d' autres au cours de l'hospitalisation. Sur les 181 patients hospitalisés, 130 (71,8%) étaient des femmes et environ 68,5% d'entre elles étaient mariées. Le taux de comportement suicidaire par brûlures chez la population rurale était supérieur à celui de la population urbaine. L'âge médian des patients était de 23 ans, avec une moyenne (± SD) de 27,9 (± 14,3) ans. Les querelles avec «un membre de la famille ou un ami¼ ont été identifiées comme le facteur le plus déterminant (88,5%) dans une tentative de suicide. Plus d'un tiers des femmes ont été victimes de violence (physique et / ou verbale) par les membres de la famille. Le taux de létalité dans cette étude était de 52,3% (68/130).Le suicide par brûlure est toujours un problème socio-épidémiologique en Iran, en particulier chez les jeunes femmes mariées dans les zones rurales. Les conditions sociales et économiques, ainsi que la violence contre les femmes, jouent un rôle majeur dans le taux élevé de suicide par brûlures. Les résultats de cette étude soulignent la nécessité de la mise en oeuvre d'une approche bien organisée pour réduire le taux de suicide par brûlures chez les populations les plus vulnérables en Iran.

KPC-producer gram negative bacteria among burned infants in Motahari Hospital, Tehran: first report from Iran.

To the best of our knowledge, this is the first report of Klebsiella, Acinetobacter and Pseudomonas-producing Klebsiella pneumoniae Carbapenemase (KPC) among burn infants in Iran. The objective of this study was to determine the phenotypic detection of these KPC among isolated Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella spp. A cross-sectional study was performed (February to September 2011) at a tertiary burn hospital in Tehran, Iran. Sixty-four strains were isolated from 20 patients. Strain and genus of isolates were confirmed, antibiotic susceptibility testing was implemented, and KPC determined by Modified Hodge Test. Fifteen of 36 strains (six Pseudomonas aeruginosa, six Acinetobacter baumannii, and three Klebsiella pneumoniae) were resistant to imipenem. Ten strains of 36 Gram negative isolates were resistant to all tested antibiotics except for Colistin. Thirteen of 15 resistant imipenem strains were confirmed as KPC-producer bacteria that isolated from nine patients. Six of 36 isolated strains were extended-spectrum ß-lactamase (ESBL)-producing bacteria, of which four strains were both KPC and ESBL. A high percentage of multidrug resistant (MDR) strains in our centre with positive KPC have created a major challenge in terms of mortality and morbidity. The findings of this study highlight the importance of implementing an effective infection control strategy to prevent and decrease the prevalence of KPC-producing organisms.

Phenotypic screening of extended-spectrum ß-lactamase and metallo-ß-lactamase in multidrug-resistant Pseudomonas aeruginosa from infected burns.

Pseudomonas aeruginosa is an important opportunistic pathogen causing nosocomial infections, especially in immunocompromised patients such as burn patients. Pseudomonas aeruginosa is potentially resistant to different broad-spectrum antibiotics due to its ability to produce extended-spectrum ß-lactamase (ESBL) and metallo-ß-lactamase (MBL). In the present 6 month study, 220 strains of multidrug-resistant (MDR) Pseudomonas aeruginosa were isolated from male and female burn patients who had been hospitalized for at least one week in Motahari Hospital in Tehran. These strains were screened by the disc diffusion and double disc methods to determine the capacity of producing ESBL and MBL. Of all strains, 18% were ESBL-positive, resulting in a significant inhibition zone (≥5 mm) with cefotaxime and ceftazidime plus clavulanic acid discs when compared to the plain cefotaxime or ceftazidime discs. 38% of the strains were MBL-positive, showing at least 7 mm difference between the inhibition zone around the imipenem discs alone in comparison with imipenem plus EDTA discs, and at least 5 mm difference between the inhibition zone around imipenem plus EDTA discs and EDTA discs alone. In the light of our results, the rapidly spreading resistance among bacterial populations due to the extensive use of antibiotics is a matter of concern for the optimal treatment of patients, particularly in burn wards, and the determination of ESBL and MBL production of MDR Pseudomonas aeruginosa strains is essential.

Nosocomial infections among burn patients in Teheran, Iran: a decade later.

The aim of this study was to determine the epidemiology of nosocomial infections among burn patients in a tertiary burn care centre in Tehran, Iran. A cross-sectional study was carried out during a 6-month period from August 2010 to January 2011 at Motahari Burn and Reconstruction Center in Tehran. Of 155 patients, 677 samples of wound and blood were taken for culture during the course of hospitalization. The rate of positive culture during the 1(st), 2(nd), 3(rd), and 4(th) week of hospitalization were 76.3%, 99.3%, 100%, and 100%, respectively. On the 2(nd), 3(rd), and 4(th) week of hospitalization, Pseudomonas aeruginosa was the most common pathogen followed by Acinetobacter, while the culture positive rate for Staphylococcus spp., Enterobacteriaceae, and Enterococcus spp. significantly decreased (P < 0.001). In this study, 70 patients out of 155 (45.2%) had at least one Acinetobacter positive culture. Our results showed that P. aeruginosa is still the leading cause of nosocomial infections. Additionally, Acinetobacter has appeared as an emerging nosocomial pathogen, and should be considered as a serious risk. We believe that changes in burn wounds' bacterial colonization over time require consistent assessment and monitoring of these changes in any burn center.

Characterization of pathogenicity island prophage in clinical and environmental strains of Vibrio cholerae.

In this study 86 isolates of Vibrio cholerae were analysed for their adhesive properties and the presence of pathogenicity island genes. With the exception of three isolates, all of the other clinical isolates (92.5%) contained an intact TCP (toxin-co-regulated pilus) gene cluster. In contrast, 95% of all environmental non-O1-non-O139 isolates were negative for the TCP gene cluster. The majority of clinical isolates (82.5%) possessed the complete vibrio pathogenicity island (VPI) gene cluster and had a similar RFLP pattern, while only a single environmental strain possessed an almost complete VPI cluster (lacking 0.4 kb in the tcpA and toxT region). The result showed that the isolates with tcpA(+)/toxT(+) had a strong attachment for HT-29 and Vero cells, whereas isolates with tcpA(+)/toxT(-) or tcpA(-)/toxT(-) genomic characteristics showed no autoagglutination and weak attachment for the cell lines. Two environmental strains (tcpA(-)/toxT(-)) showed strong adhesive properties to the cell lines, indicating that non-fimbrial adhesive factors are involved in the environmental V. cholerae strains in the absence of TCP.

Burn wound infections and antimicrobial resistance in tehran, iran: an increasing problem.

Pseudomonas aeruginosa and Staphylococcus aureus remain the most important pathogens and are frequently the cause of burn wound infections in our centre. This is a particular problem in high-risk and long-stay patients and can lead to epidemics of infection in hospital settings. This study analysed P. aeruginosa and S. aureus infections in Tohid Burn Centre, Iran, in order to estimate their frequency and antibiotic susceptibilities. Out of 6704 strains examined, 4904 and 688 were found respectively to be P. aeruginosa and S. aureus in the period March 1995-September 1999, in burn patients hospitalized in this burn centre. Antimicrobial susceptibility was determined by the disk diffusion method outlined by the National Committee for Clinical Laboratory Standards. The overall frequencies of P. aeruginosa and S. aureus were respectively 73.1% and 10.3%; the remaining 16.6% consisted of other organisms. The frequency of P. aeruginosa resistance to cipro?oxacin, amikacin, and gentamicin was over 85%. The rate of S. aureus resistance to cloxacillin and cephalexin was 90%. P. aeruginosa and S. aureus were thus the commonest organisms in this centre. High frequency rates of resistance to these micro-organisms were found in this study. It is necessary to limit the use of antimicrobial agents in our epidemiological setting. In 2000 the Burn Centre was closed.

Pediatric burn injuries in Tehran, Iran.

The objective of this study was to identify the epidemiologic features of pediatric burn injuries in western Tehran. Study subjects included all children up to the age of 15 years who were treated as inpatients at the Tohid Burn Center in Tehran between April 1995 and March 1998. Among the 3341 burns admitted to the Center over the 3-year study period, 1454 (43.5%) occurred in children less than 16 years of age. The overall case fatality rate for children was 16%, while the annual burn incidence rates ranged from 22.7 to 17.8 burns per 100000 child-years. The overall gender ratio (boys/girls) was 2.6. Children less than 2 years of age had the highest burn incidence and burn mortality rates. These findings will be used as a basis for developing targeted preventive programs to protect Iranian children from burns.

Pseudomonas infections in Tohid Burn Center, Iran.

Burn injury is a major public health problem in many areas of the world. Pseudomonas aeruginosa is one of the most common causes of burn wound infection in burn patients. Septicemia due to this organism is a major cause of mortality among burn patients. This study analyzed P. aeruginosa infections in the Tohid Burn Center in Tehran during 1995-1997 in order to estimate their frequency, antibiotic susceptibility and their role in burn morbidity. Among 2122 patients who were admitted during this study period, 3365 bacterial strains were isolated and the frequency of P. aeruginosa was 73.9%. This was followed by Staphylococcus aureus (9.1%) and other organisms (17%) in frequency. The frequency of P. aeruginosa resistant to gentamicin, carbenicillin, co-trimoxazole, ceftizoxime and tetracycline was over 95% and resistance to amikacin which was 49% in 1995, increased to 90% in 1997. With the introduction of ciprofloxacin at our burn center, the frequency of P. aeruginosa resistance increased from 45% in 1995, to 82% in 1997. P. aeruginosa was found more frequently in the ICU than in the wards. These findings show that P. aeruginosa remains the leading cause of nosocomial infections in our burn center. It is necessary to introduce urgent measures for restriction of the spread of P. aeruginosa infections in our burn center.

In vitro activity of cefixime versus ceftizoxime against Salmonella typhi.

Emergence of multi-resistant strains of Salmonella typhi is a major problem in treatment of typhoid fever and requires an excessive hospitalization period. Therefore, the present study was carried out to estimate the degree of the resistance of S. typhi strains to various antibiotics such as cefixime. Fifty two strains of Salmonella typhi isolated from patients with typhoid fever and their sensitivity to various antibiotics was determined. MICs of cefixime and chloramphenicol were also determined according to comitee de l'antibiogramme français. Results indicated that 41.9%, 33.9%, 38.7%, 58.1% and 1.6% of isolated strains were resistant to chloramphenicol, co-trimoxazole, ampicillin, tetracycline and gentamycin respectively. About one third (33.9%) of strains showed multiple resistance to the first four mentioned antibiotics. All strains were susceptible to ceftizoxime and cefixime (MICs 1 and less than 1 mcg/ml). It could be concluded that cefixime due to its effectiveness, oral administration and shorter courses of treatment could be the therapy of choice in cases of typhoid fever caused by multiple resistant strains especially when we have a shortage of hospital beds.

Implantation and in vivo antagonistic effects of antibiotic-susceptible Escherichia coli strains administered to premature newborns.

Two antibiotic-susceptible and non-pathogenic Escherichia coli strains were administered to hospitalized premature infants in order to protect them from intestinal colonization by hospital-acquired antibiotic-resistant enteric organisms (EOs). Three groups of 16 premature newborns received respectively strain ECA, strain EMO and both strains simultaneously. A fourth group was used as a control. Resistant EOs became spontaneously established in the digestive tract of a majority of the unadministered children. Both ECA and EMO were able to colonize the digestive tract of a majority of the subjects, and reached high population numbers (greater than 10(7)/g) in the faeces. Both strains appeared as able to reduce significantly the establishment of antibiotic-resistant EOs. This effect was more prominent with EMO, which also impaired the implantation of ECA when both strains had been administered simultaneously. The use of such innocuous microorganisms could thus constitute an additional means of preventing nosocomial infections of intestinal origin.

[The effect of previous antibiotherapy on the colonization of an Escherichia coli strain sensitive to antibiotics in the digestive tract of hospitalized children]. / Influence d'une antibiothérapie préalable sur l'implantation d'une souche d'Escherichia coli sensible aux antibiotiques dans le tube digestif des enfants hospitalisés.

The administration of the Escherichia coli (az) strain has already been used successfully to protect premature infants against intestinal colonization by nosocomial strains of antibiotic resistant enteric organisms. The purpose of the present study was to assess the protective value of this strain in older full term babies after cessation of an antibiotics treatment. Two groups of children treated with antibiotics of respectively 8-90 days and 3-12 months of age were studied and compared to two control groups of untreated children. In both groups of children, the implantation of E. coli az was higher in treated than in untreated subjects. The group of younger children was significantly less colonized by antibiotic resistant hospital acquired enteric organisms, whereas in 3-12 months old children non protective effect of E. coli az was recorded. Therefore, the antagonistic effect of the strain studied appeared as age dependent.

[Early administration of antibiotic susceptible strain of Escherichia coli in the intestine of the premature infant]. / Administration précoce d'une souche de Escherichia coli antibiosensible dans l'intestin du nouveau-né prématuré.

An antibiotic-susceptible, innocuous Escherichia coli strain of human origin was administered to premature infants in order to protect them from nosocomial colonization by antibiotic-resistant enteric organisms. The strain was given to 16 untreated patients in the first six hours of life, and to 11 patients treated with antibiotics in the first six hours after cessation of treatment. The strain was able to colonize the intestinal tracts of all treated infants and 14/16 untreated infants. Colonization of these patients by antibiotic-resistant enteric organisms was compared with results obtained in a control group of 15 unadministered and untreated infants. A significant difference was recorded in the first ten days after administration. Our results show that previous antibiotic treatments did not impair intestinal colonization by an antibiotic-susceptible strain, and demonstrate the in vivo antagonistic abilities of the administered strain. Such antagonistic strains might thus be used for control of nosocomial infections of intestinal origin due to antibiotic-resistant enteric organisms.