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Resumen Introducción: El método de difusión de doble disco se presenta como una alternativa diagnóstica que permite identificar aislados de Staphylococcus aureus susceptibles a clindamicina, ante el aumento de resistencia a meticilina, reduciendo así la posibilidad de fallo en el tratamiento. Objetivo: Determinar la frecuencia de resistencia a clindamicina inducida por eritromicina en S. aureus resistentes a meticilina (SARM) aislados de niños paraguayos. Materiales y Métodos: Estudio observacional, descriptivo, de corte transversal. Se colectaron 145 aislados S. aureus que causaron infecciones de piel y tejidos blandos y osteo-articulares en pacientes pediátricos del Hospital Central del Instituto de Previsión Social en el período de diciembre-2012 a noviembre-2013. La resistencia a clindamicina se determinó por métodos automatizados y de difusión de doble disco. Se realizó reacción de polimerasa en cadena para genes ermA, ermB, ermC y msrA de aislados representativos. Resultados: La resistencia global a meticilina y clindamicina fue de 67 y 13%, respectivamente (11% atribuible al mecanismo de resistencia a clindamicina inducible). Los genes ermC y msrA fueron detectados individualmente en 25 y 17% de los aislados, respectivamente, mientras que un aislado presentó ambos genes en simultáneo. Discusión: La frecuencia de mecanismo de resistencia inducible a clindamicina señala la importancia de los métodos de difusión de doble disco en la práctica microbiológica, así como se encuentran en los límites de puntos de cortes considerados como aceptables para el uso de este antimicrobiano para infecciones cutáneas y osteo-articulares causadas por SARM.

Introduction:Pseudomonas aeruginosa is one of the major pathogens associated with the acute tissue damage in patients having Diabetic Foot Ulcer (DFU). The treatment of such infections can be an uphill battle due to the serious resistance to all the mainstay antibiotics, owing to overzealous production of Extended-Spectrum Beta-Lactamases (ESBLs). Pakistan also has a high prevalence of diabetes and complications related to it, however genetic disposition of the pathogens remains underinvestigated.Aim:The main objective of the study was to determine the frequency of ESBLs in Multi-drug resistant P. aeruginosa from diabetic foot patients.Methods:The duration of the present study was one year and 100 patients having DFU were enrolled. All the pus samples were subjected to the bacterial culture, gram staining, catalase test, oxidase test and antimicrobial susceptibility pattern to various antibiotics for the confirmation of P. aeruginosa. Of 23 positive isolates of P. aeruginosa, 10 were ESBLs positive as detected by double disk diffusion test. The positive ESBL strain shows an increase of ≥5mm in the zone of inhibition of the combination discs in comparison to the alone ceftazidime disc.Results:The ESBLs positive strains were also tested for TEM-1, SHV-1, PER-1, and VEB-1, where: (07/10) strains carried SHV-1, (05/10) strains were positive for TEM-1, while none of the isolates were PCR-positive for PER-1 and VEB-1.Conclusion:The findings of the current study show a difference in the pattern of ESBL genes compared to that of other such endeavors. The present study also warrants the PCR-based detection of the type of ESBL as a potential factor to consider in deciding the therapeutic strategy at any point during the treatment.

STAPHYLOCOCCUS aureus is the most common pathogens and an important nosocomial pathogen. This bacterium has ability to acquire resistance to different antibiotic classes. Erythromycin and clindamycin have been used for treating skin and soft-tissue infections caused by these bacteria. Although, expression of macrolide-lincosamide-streptogramin B resistance (MLSB) can limit the effect of these drugs.This study aimed to detect the presence of genes encoding resistance to macrolides, lincosamides and streptogramins (MLSB) among clinical Staphylococcus strains.A total of 100 Staphylococcus isolates from clinical specimens (blood, sputum and wound) were collected. All these isolates were identified biochemically. They were tested against different antibiotics and double-disk diffusion method and genes were detected using PCR.Results show that 63 isolates were genotypically tested by using real time PCR for detection of Erm (B) and Erm (C) genes. (EryS ClinS) was detected in 50 (50%) of the isolates followed by constitutive phenotype of MLSB resistance (EryR ClinR) 29 (29%) and inducible MLSB resistance (EryRClinInd) 17 (17%), while the MSB phenotype (EryR ClinS) 4(4%) was the least frequent. 51(80.9) isolates have Erm (B) gene positive 33(52.3) strains have Erm (C) gene positive.This study investigate that the double disk diffusion test is a suitable test for detection of staphylococci which are resistant to clindamycin and should be used as fast detection and help in treatment of patients. And thus, the screening procedure using Real time PCR is sensitive in detection of Erm genes which are responsible for inducible resistance to clindamycin.

Objectives: construction of agricultural environmental soil antibiotic resistance profile of the culturable bacteria in Kalyani, India, followed by the screening of ESBL producers harboring blatem, blashv, and blactx-M. Methods: 158 Multi-Drug Resistant (MDR) bacteria were isolated from 18 agricultural sampling points in Kalyani, West Bengal, India followed by their Antibiotic resistance profiling against 15 test antibiotics. They were then screened for the presence of three Extended Spectrum Beta-Lactamase (ESBL) genes, namely blatem, blactx-M and blashv by Double Disk Diffusion test and Polymerase Chain Reaction. The positive candidates were further identified using Amplified Ribosomal DNA Restriction Analysis followed by 16S rDNA sequencing. Results: lowest resistance was observed against Vancomycin (0%) whereas the highest against the β lactam Ampicillin (97.5%). Very high resistance was observed against the 3rd generation cephalosporin Cefotaxime (90%). 16/158 bacterial isolates were positive for one or more of the three ESBL genes under investigation. 11 out of those 16 isolates (68.75%) harbored at least 2 genes and the rest 31.25% either had the blashv or the blatem gene. Phylogenetic analysis of the prevalent ESBL carrying organisms in the region demonstrated that the genes are being horizontally transferred across different bacterial orders and classes. Conclusion: Significant antimicrobial resistance noted against 12 out of 15 antibiotics tested. Stenotrophomonas, Myroides, Pseudomonas, Enterobacter, and Serratia are found as culturable MDR bacteria carrying ESBL genes among the isolates. It is the first report of environmental ESBL carriage by Myroides isolated from India. Keywords: Multi-drug resistance, Antibiotic resistance profiling, Extended spectrum beta lactamases, Myroides

This work was planned to investigate the prevalence of P. aeruginosa in broiler chickens kidneys suffered from naked eye pathological lesions. Out of 240 examined kidneys samples, 25 isolates (10.4%) of P. aeruginosa were recovered. Antimicrobial sensitivity pattern against 14 different antimicrobials comprising nine groups proved that isolates were resistant to most of the used antimicrobial agents. Phenotypic detection of extended spectrum beta-lactamases (ESBLs) producing isolates using modified double disk diffusion test revealed that, ten (40%) were ESBLs producers. Genotypically using PCR, three ESBLs genes (TEM, Ctx-M and Shv) and three virulence genes (lasI, Tox A and Plc H) were detected with different percentages. Cinnamon and carvacrol oils were found bactericidal for P. aeruginosa at concentrations of 4% and 0.4% respectively.

The aims of this study were to describe the distribution of the most common erm genes in a collection of Norwegian Bacteroides isolates and to investigate whether the phenotypic tests for determining inducible clindamycin resistance among Bacteroides species recommended by EUCAST, NordicAST and the manufacturer of E-test®, are effective. We investigated 175 unique Bacteroides isolates for the presence of erm(B), erm(F) and erm(G) genes, determined their minimum inhibitory concentrations (MICs) to clindamycin and categorised their susceptibility according to EUCAST breakpoints. 27 isolates were resistant to clindamycin. Furthermore, we investigated whether these recommended methods could detect inducible resistance in the Bacteroides isolates: 1) EUCAST recommendation: Dissociated resistance to erythromycin (clindamycin susceptible with erythromycin MIC > 32 mg/L), 2) NordicAST recommendation: Double disk diffusion test (DDD) or 3) Manufacturer of E-test®’s recommendation: prolonged incubation of clindamycin E-test® for 48 h. erm genes were detected in 30 (17%, 95% CI 12%–23%) of 175 Bacteroides isolates with erm(F) as the dominating gene. There were six (4%, 95% CI 1%–7%) of 148 clindamycin susceptible isolates harbouring erm genes, they were considered inducibly resistant to clindamycin. None of the methods for phenotypic detection of inducible clindamycin resistance performed satisfactory with sensitivities of 33%, 17% and 0% and specificities of 90%, 99% and 97% for dissociated resistance, DDD and prolonged incubation of clindamycin E-test®, respectively. In our view, the scientific basis for investigating every Bacteroides isolate for inducible resistance to clindamycin is weak. Molecular detection of erm genes may prove a better option than the phenotypic methods we evaluated.

Widespread use of Macrolide, lincosamide and Streptogramin B (MLSB) family of antibiotics in the treatment of Staphylococcus aureus (S. aureus) has led to an increased resistance to MLSB antibiotics. The purpose of this study was to determine the frequency of MLSB resistance among clinical isolates of methicillin sensitive S. aureus (MSSA) and Methicillin resistant S. aureus (MRSA) from Mansoura University Children Hospital (MUCH), Egypt, phenotypically by using D‑test and genotypically by detection of erm genes by PCR. Different microbiological samples were collected under complete aseptic condition from patients in MUCH according to the site of infection over a period of 9 months from March 2016 to November 2016. S. aureus isolates were identified using standard microbiological methods. MRSA was detected by growth on oxacillin screen agar plate and cefoxitin disk screen test. Antimicrobial susceptibility of the isolates was determined by Kirby-Bauer disk diffusion method. S. aureus isolates that were found to be erythromycin resistant were further studied for inducible clindamycin resistance using D-zone test according to CLSI recommendations. erm genes in S. aureus isolates were detected by PCR. Among 230 S. aureus isolates, 164 were MSSA (71.3%) and 66 were MRSA (28.7%). Twenty-five MSSA (15.2%), and 37 MRSA (56.1%) isolates were erythromycin resistant. Constitutive MLSB phenotype (cMLSB) (30.3 and 4.2%) and inducible MLSB phenotype (iMLSB) (22.7 and 7.9%) were observed in MRSA and MSSA, respectively by D-zone test. The rate of iMLSB phenotype and cMLSB phenotype in MRSA was significantly higher than in MSSA isolates. The frequency of ermA, ermB and ermC genes were 72.9, 5.4 and 13.5% in MRSA isolates and 60, 4 and 12% in MSSA isolates, respectively. Screening test for of iMLSB‑resistant strains is very important by double disk diffusion test (D‑test). This phenotypic test is simple, accessible and reliable method that can be done in every laboratory and research facility, without the need of costly genetic tests. Since the treatment of patients infected with S. aureus with iMLSB phenotype with clindamycin can lead to the expansion of constitutive resistance (cMLSB) and therapy failure. Key words: Clindamycin, cMLSB, erm genes, iMLSB phenotype, MRSA, MSSA, S. aureus.

Extended Spectrum ß- Lactamase (ESBL) acquired by bacteria is a highly effective weapon for drug resistance against a wide range of antibiotics (penicillins, cephalosporins and monobactams). ESBLs have continued to increase in variety and prevalence and are now a global health concern including Bangladesh. They are associated with failure in effective treatment, increased morbidity and mortality, poor outcomes, increases in length of stay (LOS) in hospital and health care costs. So, it is important to identify it and take necessary measures to treat with appropriate antimicrobial therapy. This study has been designed to establish an easy method for routine reporting of ESBL organisms and notify it's incidence in Health Care settings. Double Disk Diffusion Test, utilizing Cefotaxime, Amoxicillin/Clavulanic acid and Ceftazidime, was used as Screening Test. Phenotypic Confirmatory Test was done for confirmation of screening ESBL positive organisms. Four hundred seventy two organisms (Escherichia coli and Klebsiella sp.) were isolated from urine and pus collected from Health Care settings. Only 50 screening ESBL positive organisms and 50 ESBL negative organisms were tested by Phenotypic Confirmatory Test. All of them were positive and negative respectively by Phenotypic Confirmatory Test. Predominant organism among the isolates was Escherichia coli (82.8%) of which 54.4% were ESBL positive followed by Klebsiella sp. (17.2%) of which 44.4% were ESBL positive. ESBL positivity was more in hospital infections (73.3%) than in community acquiredinfections (44.5%).Bangladesh J Med Microbiol 2014; 08 (02): 23-27

Objective: To study the prevalence of inducible clindamycin along with vancomycin and methicillin resistance and assessment of hyper variable region (HVR) of mecA gene among different clinical isolates of Staphylococcus spp. Methods: A total of 176 clinical isolates of Staphylococci were collected from Pakistan Institute of Medical Sciences (PIMS), Islamabad during 2014-2015. The sample sources were pus, blood, urine, sputum, tracheal secretions and tissue fluids. Bacterial identification was done by colony morphology and biochemical tests. Kirby-Bauer disc-diffusion method was carried out to assess the susceptibility against different antibiotics. Minimal inhibitory concentrations (MICs) were done for vancomycin resistance. Double Disk Diffusion test (D-test) was used to detect the clindamycin inducible resistance. PCR was performed to detect erm(C), mecA and HVR genes. Results: Clindamycin inducible resistance among Staphylococcal isolates was found to be 7%, whereas in S. aureus it was 4%, and in coagulase negative Staphylococci (CoNS) it was 11%. The highest resistance was observed against fosfomycin, fusidic acid and cefoxitin. Vancomycin resistance was observed in 23 isolates (13%) of Staphylococci. erm(C), mecA and HVR genes were found in 18%, 50% and 42% respectively. Conclusions: D-test must be performed routinely to avoid clindamycin failure. A high level of resistance against vancomycin in Staphylococcal isolates is a concern for public health. doi: https://doi.org/10.12669/pjms.36.2.665 How to cite this:Khan AA, Farooq J, Abid M, Zahra R. Assessment of inducible clindamycin resistance and Hyper Variable Region (HVR) of mecA gene in clinical staphylococci. Pak J Med Sci. 2020;36(2):136-140. doi: https://doi.org/10.12669/pjms.36.2.665 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Resumen Introducción: El método de difusión de doble disco se presenta como una alternativa diagnóstica que permite identificar aislados de Staphylococcus aureus susceptibles a clindamicina, ante el aumento de resistencia a meticilina, reduciendo así la posibilidad de fallo en el tratamiento. Objetivo: Determinar la frecuencia de resistencia a clindamicina inducida por eritromicina en S. aureus resistentes a meticilina (SARM) aislados de niños paraguayos. Materiales y Métodos: Estudio observacional, descriptivo, de corte transversal. Se colectaron 145 aislados S. aureus que causaron infecciones de piel y tejidos blandos y osteo-articulares en pacientes pediátricos del Hospital Central del Instituto de Previsión Social en el período de diciembre-2012 a noviembre-2013. La resistencia a clindamicina se determinó por métodos automatizados y de difusión de doble disco. Se realizó reacción de polimerasa en cadena para genes ermA, ermB, ermC y msrA de aislados representativos. Resultados: La resistencia global a meticilina y clindamicina fue de 67 y 13%, respectivamente (11% atribuible al mecanismo de resistencia a clindamicina inducible). Los genes ermC y msrA fueron detectados individualmente en 25 y 17% de los aislados, respectivamente, mientras que un aislado presentó ambos genes en simultáneo. Discusión: La frecuencia de mecanismo de resistencia inducible a clindamicina señala la importancia de los métodos de difusión de doble disco en la práctica microbiológica, así como se encuentran en los límites de puntos de cortes considerados como aceptables para el uso de este antimicrobiano para infecciones cutáneas y osteo-articulares causadas por SARM. Background: The double disc diffusion method is an alternative diagnostic that allows the identification of Staphylococcus aureus isolates apparently susceptible to clindamycin but that may develop resistance due to an induction phenomena, mainly asociated to the increase in resistance to methicillin, thus increasing the possibility of failure in the treatment. Aim: To determine the frequency of induced clindamycin resistance in methicillin-resistant S. aureus (MRSA) isolated from Paraguayan children. Materials and Methods: In this cross sectional study, we collected 145 S. aureus isolates that caused skin and soft tissue and osteoarticular infections in pediatric patients of the Central Hospital I.P.S. in the period from December-2012 to November-2013. Resistance to clindamycin was determined by automated methods and double disc diffusion. PCR was performed for ermA, ermB, ermC and msrA genes from representative isolates. Results: The global resistance to methicillin and clindamycin was 67 and 13%, respectively (11% attributable to the inducible mechanism). The ermC and msrA genes were detected individually in 25 and 17% of the isolates respectively while an isolate presented both genes simultaneously. Discussion: The frequency of inducible resistance to clindamycin indicates the importance of double disc diffusion methods in microbiological practice, as well as being within the cut off points considered acceptable for the use of this antibiotic for skin infections. and osteoarticular caused by MRSA.

Made available in DSpace on 2018-12-11T16:41:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01. Added 1 bitstream(s) on 2019-10-09T18:28:33Z : No. of bitstreams: 1 S1517-83822016000100191.pdf: 925242 bytes, checksum: 13310cbeb78914b8e91ca21dbd4ba22c (MD5) The aim of this study was to investigate the occurrence of multidrug-resistant, extended spectrum beta-lactamase (ESBL) producing Salmonella spp. isolated from conveyor belts of broiler cutting rooms in Brazilian broiler processing plants. Ninety-eight strains of Salmonella spp. were analyzed. Multidrug resistance was determined by the disk diffusion test and the susceptibility of the isolated bacteria was evaluated against 18 antimicrobials from seven different classes. The double disk diffusion test was used to evaluate ESBL production. Of the 98 strains tested, 84 were multidrug resistant. The highest rates of resistance were against nalidixic acid (95%), tetracycline (91%), and the beta-lactams: ampicillin and cefachlor (45%), followed by streptomycin and gentamicin with 19% and 15% of strain resistance, respectively. By contrast, 97% of the strains were sensitive to chloramphenicol. 45%of the strains were positive for the presence of ESBL activity. In this study, high rates of multidrug resistance and ESBL production were observed in Salmonella spp. Universidade Federal do Paraná (UFPR), Rua Pioneiro no 2153, Bairro Jardim Dallas Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Distrito de Rubião Júnior s/n Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Distrito de Rubião Júnior s/n

Background: In Turkey, Escherichia coli causing urinary tract infections (UTI) do not have current data on antibacterial resistance, extended spectrum β-lactamase (ESBL) enzymes types and virulence factors. Objectives: In this study, the isolation of E. coli from patients with UTI, determination of antimicrobial resistance of isolates, and investigation of the presence of ESBL enzymes and pyelonephritis-associated P fimbriae types, were aimed. Methods: Isolation E. coli from urine samples and identification were performed with conventional methods. Antibiotic resistance profiles were performed with the disc diffusion test (DDT). The presence of ESBL enzyme was investigated by the double disk diffusion test (DDDT). The presence of ESBL genes and P fimbriae genes were also investigated with PCR. The Chi squared test was used to compare the relationship between antibiotic susceptibility and resistance status in ESBL producing or non-producing and P fimbriae carrying and non-carrying isolates. Results: It was determined that 50.3% and 41.9% of isolates were resistant to ciprofloxacin, trimethoprim sulfamethoxazole. It was demonstrated that 49.7% of isolates were phenotypically ESBL positive, while 59.4% were genetically positive. The percentages of genes detected with PCR were 32.3%, 31.6%, 21.1%, 2.3% for blaTEM, blaCTX, blaOXA, blaSHV, respectively. A total of 51 pap genes were detected in 27.0% (36/133) of the total isolates. Conclusions: Extended spectrum β-lactamase producing E. coli infections associated with UTI increased in last years in Turkey. Further studies should be designed to investigate plasmids of ESBL positive E. coli stains isolated from UTI and whether plasmids are responsible for ESBL production.

The widespread use of Macrolide Lincosamide Streptogramin B (MLSB) antibiotics has led to an increase in the resistant strains. Although Clindamycin is effective against MRSA but its use in the presence of Erythromycin can lead to induction of cross-resistance among members of the MLSB group which could limit the effectiveness of this drug. Furthermore, at times, some strains are also harbored with PVL genes which are encoded by two contiguous and co-transcribed genes viz., lukF-PV and lukS-PV. The results of a study conducted to find the prevalence of inducible Clindamycin resistance in PVL positive isolates of Staphylococcus aureus from Belgaum, Karnataka, India. Method: More than 120 isolates of S.aureus were collected from hospital in Belgaum during the period 2010-2012, out of which, 72 isolates confirming S.aureus status were kept for further study at RMRC (ICMR), Belgaum. They were characterized as resistant/sensitive using various conventional, molecular and automated techniques. PVL genes LukS and LukF in these strains were detected by PCR. Phenotypic inducible resistance to clindamycin was detected by Double Disk Diffusion test. Result: Out of 72 isolates, 46 were MRSA and 26 were MSSA. In all, 50 isolates (69.44%) showed the presence of PVL genes. Out of these, 14 PVL positive S. aureus isolates (26.38%) showed iMLSB phenotype which included 13 MRSA and 1 MSSA. Conclusion- The cause of concern is the 13 isolates which are MRSA, PVL positive and show inducible clindamycin resistance. Such a combination can be a treatment challenge to the clinicians who are left with very few options.

Background: Clindamycin inducible resistant Staphylococcus aureus (S.aureus) isolates can cause failure in treatment with this antibiotic. Biofilm production via polysaccharide intercellular adhesion (PIA) contributes in the colonization of S. aureus , resulting in the initiation of different diseases. The aim of this study was to detect icaADBC genes among isolates of S.aureus with inducible resistance to clindamycin. Materials and Methods: A total of 209 clinical S.aureus isolates were collected and identified by conventional phenotypic tests. Isolates with inducible resistance to clindamycin were detected by double disk diffusion test (D-Test) using clindamycin (2 �� g) and erythromycin (15 �� g). Oxacillin was used to detect Methicillin resistant Staphylococcus aureus (MRSA) isolates. Polymerase Chain Reaction (PCR) was performed to detect the icaADBC genes. Results: The rate of clindamycin inducible resistance was 4% (n=8). All the isolates were susceptible to methicillin. Four isolates (50%) Contained the whole icaADBC genes. The prevalence of icaA, icaB, icaC and icaD genes were 5 (62.5%), 4 (50%), 6 (75%) and 5 (62.5%), respectively. Conclusion: The results indicate that the prevalence of icaADBC genes among clindamycin inducible resistant strains was low, and also these strains were susceptible to methicillin.

Macrolide resistance in Streptococcus pneumoniae and in group A streptococci (GAS) is a significant problem worldwide. In Serbia, data on the mechanisms of resistance and the corresponding resistance genes in streptococci are largely lacking. Therefore, we analyzed the distribution of macrolide resistance phenotypes and genotypes in 44 macrolideresistant GAS (MRGAS) and 50 macrolide-resistant S. pneumoniae (MRSP) isolates collected in the same period. The double disk diffusion test and PCR were used to analyze resistance phenotypes and resistance genes, respectively. Among MRSP, the MLSB phenotype dominated, whereas the M phenotype was the most prevalent among MRGAS isolates. Consequently, in MRSP, the ermB gene was the most common (n=40, 80%), followed by the mefA gene (n=7,14%). In MRGAS strains, mefA dominated (n=27,61%), followed by ermA (n=15, 33%) and ermB (n=3, 7%). In 3 MRSP isolates no resistance genes were detected, while one MRGAS strain with iMLSB phenotype harbored both ermA and mefA genes.

Although macrolides are widely used for treating pneumococcal infections, an increase in macrolide resistance might compromise their use. The objective of this study was to determine the prevalence of macrolide-resistant phenotypes and genotypes in macrolide-resistant S. pneumoniae isolates in Serbia. A total of 228 macrolide-resistant strains isolated during the period of 2009-2012, were analyzed. Macrolide resistance phenotypes were determined by a double disk diffusion test. The presence of macrolide resistance genes was detected by PCR. Antibiotics susceptibilities were tested using the VITEK2 system and E test. Among the examined isolates, the MLSB phenotype which is linked to the presence of the erm(B) gene dominated (83.3%), while the mef(A) gene which is associated with the M phenotype, was identified in 16.7% isolates. Over 40% of isolates expressed co-resistance to penicillin. A multiple-resistant pattern was found in 36.4% strains, more frequently in children. However, all strains were susceptible to telithromycin, vancomycin, linezolid, fluoroquinolones and rifampicin. [Projekat Ministarstva nauke Republike Srbije, br. 175039]

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli strains have been reported worldwide; however, the incidence and characterization of foodborne ESBL-producing E. coli strains have been rarely reported in the People's Republic of China. Among a collection of 659 E. coli isolates recovered from retail foods in Shaanxi Province, People's Republic of China, 223 cefoxitin-resistant and/or cefoperazone-resistant isolates were screened for ESBL production with the double disk diffusion test. The ESBL-producing isolates were characterized for antimicrobial resistance and the presence of blaTEM, blaSHV, and blaCTX-M genes. Isolates with blaCTX-M were further classified by PCR as having blaCTX-M-1, blaCTX-M-2, blaCTX-M-8, blaCTX-M-9, or blaCTX-M-25. One hundred forty-seven isolates were identified as ESBL positive. PCR detection revealed that 146 isolates (99.3%) contained the blaCTX-M gene. Among these isolates, 42 (28.8%) were positive for the enzyme CTX-M-1, 5 (3.4%) for CTX-M-2, and 99 (67.8%) for CTX-M-9. No CTX-M-8 and CTX-M-25 were found in this study. One hundred fifteen isolates (78.2%) were positive for the blaTEM gene, but blaSHV was not detected. Among the 147 ESBL-producing E. coli isolates, 75 (51.0%), 35 (23.8%), and 4 (2.7%) isolates were positive for blaTEM and blaCTX-M-9, blaTEM and blaCTX-M-1, and blaTEM and blaCTX-M-2, respectively. All of the 147 ESBL-producing isolates were resistant to three or more non-β-lactam antibiotics. This study provides evidence that foodborne E. coli can harbor ESBL-encoding genes. Thus, food could be a vehicle for the dissemination of ESBL-producing E. coli strains, a situation that requires surveillance and appropriate management strategies.

b-Lactamase production is considered one of the most important resistance mechanisms among virulent Pseudomonas aeruginosa isolates. The aim of this study was to compare the production and antimicrobial resistance patterns of some virulence factors in extended spectrum b-lactamase (ESbL)-producing and nonproducing P. aeruginosa clinical isolates. Materials and methods: Out of 183 different clinical specimens, 104 Pseudomonas aeruginosa isolates were recovered. The isolates were screened for ESbL production using the double disk diffusion test and phenotypic confirmatory disk diffusion test. All isolates were tested for susceptibility to 25 antimicrobials, as well as for expression of various virulence factors including pigment, hemolysin, gelatinase, protease, lipase, rhamnolipids, biofilm, and cell surface hydrophobicity. The results of ESbL producers and nonproducers were statistically compared. Results: All isolates showed a high frequency of multiple resistance to at least 14 and up to 25 of the tested antimicrobials. Nevertheless, most virulence factors were produced at higher rates in ESbL-producing than in ESbL-nonproducing Pseudomonas aeruginosa isolates. Conclusion: The results of this study suggest a correlation between ESbL phenotype and the production of some factors that are reported to be involved in the virulence of P. aeruginosa.

We undertook this study to assess the accuracy of the clindamycin-erythromycin disk approximation test (D-test) for detection of inducible clindamycin resistance in Staphylococcus spp. One hundred sixty-three Staphylococcus aureus and 68 coagulase-negative Staphylococcus (CoNS) spp. which were erythromycin nonsusceptible but clindamycin susceptible were tested using the D-test performed at both 15-mm and 22-mm disk separations and compared with genotyping as the “gold standard.” The rate of inducible clindamycin resistance was 96.3% for S. aureus and 33.8% for CoNS spp. The sensitivities of the D-tests performed at 15 mm and 22 mm were 100% and 87.7%, respectively, and specificities were 100% for both. The use of 22-mm disk separation for the D-test to detect inducible clindamycin resistance results in an unacceptably high very major error rate (12.3%). All isolates with false-negative results harbored the ermA gene, and the majority were methicillin-resistant Staphylococcus aureus . False-negative results were associated with smaller clindamycin zone sizes and double-edged zones. We recommend using a disk separation distance of ≤15 mm. There is wide geographic variation in the rates of inducible clindamycin resistance, and each laboratory should determine the local rate before deciding whether to either perform the D-test routinely or else report that all erythromycin-resistant S. aureus isolates are also clindamycin resistant.

Increasing community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has led many to use clindamycin for CA-MRSA disease, whereas others suggest caution because of inducible clindamycin resistance and rely on drugs such as trimethoprim-sulfamethoxazole (TMP-SMX).To analyze the change in antibiotic susceptibility pattern of S. aureus isolates from 2001 to 2004 in a closed health care system, a period during which clindamycin and TMP-SMX use increased 99 and 62%, respectively.S. aureus cultures from 57 military hospitals and clinics from 2001-2002 and 2003-2004 were compared for body site and antibiotic sensitivity, particularly the potentially inducible clindamycin-susceptible erythromycin-resistant pattern. A portion was evaluated by a double disk diffusion test (D test).Numbers of S. aureus-positive cultures obtained from "wound" sites rose significantly in both pediatric (138 to 215, P0.001) and adult (715 to 972, P0.001) isolates, with a rise in MRSA in children (6 of 138 to 60 of 215, P0.001) and in adults (161 of 715 to 324 of 972, P0.001). Clindamycin resistance increased among pediatric S. aureus isolates (1 of 207 to 13 of 327, P0.05), whereas96% remained TMP-SMX-susceptible. Five methicillin-susceptible S. aureus (MSSA), 2 MRSA of 41 pediatric and 36 MSSA, 43 MRSA of 437 adult S. aureus specimens were D test-positive.In late 2004, most S. aureus from our region are still beta-lactam-susceptible. Most of the MRSA are still susceptible to clindamycin and do not appear to have inducible resistance. We must closely monitor the rates of constitutive and inducible clindamycin resistance as well as consider treatment alternatives that may slow the rate of clindamycin resistance.

Salmonella spp. producing extended-spectrum beta-lactamases (ESBLs) have been reported in many countries, but there is no information on their prevalence in Africa. ESBL-producing Salmonella enterica serotype Isangi and S. enterica serotype Typhimurium strains have been noted in South Africa since 2001. A total of 160 consecutive isolates of Salmonella spp. were collected from 13 hospitals located in different cities in South Africa over a 5-month period from December 2002 to April 2003. All strains were screened for production of ESBLs by the double disk diffusion test and for AmpC production by assessing resistance to cefoxitin. bla SHV , bla TEM , bla CTX-M , and bla CMY-2 were sought from all ESBL-positive and cefoxitin-resistant isolates. A total of 15.6% (25 of 160) isolates produced SHV or TEM ESBLs, and 1.9% (3 of 160) produced CMY-2. Nine S. enterica serotype Typhimurium, eight S. enterica serotype Isangi, and three S. enterica serotype Muenchen strains produced either TEM-63 or a derivative of TEM-63 designated TEM-131. Both TEM-63 and TEM-131 have an isoelectric point of 5.6, and their sequences have the following amino acid substitutions compared to the TEM-1 sequence: Leu21Phe, Glu104Lys, Arg164Ser, and Met182Thr. Additionally, TEM-131 has an Ala237Thr substitution. ESBL-producing Salmonella spp. have become a significant public health problem in South Africa with particular implications for the treatment of serious nontyphoidal Salmonella infections in children, for whom extended-spectrum cephalosporins were the preferred treatment.

Resistance to macrolides in staphylococci may be due to active efflux (encoded by msrA ) or ribosomal target modification (macrolide-lincosamide-streptogramin B [MLS B ] resistance; usually encoded by ermA or ermC ). MLS B resistance is either constitutive or inducible following exposure to a macrolide. Induction tests utilize closely approximated erythromycin and clindamycin disks; the flattening of the clindamycin zone adjacent to the erythromycin disk indicates inducible MLS B resistance. The present study reassessed the reliability of placing erythromycin and clindamycin disks in adjacent positions (26 to 28 mm apart) in a standard disk dispenser, compared to distances of 15 or 20 mm. A group of 130 clinical isolates of Staphylococcus aureus and 100 isolates of erythromycin-resistant coagulase-negative staphylococci (CNS) were examined by disk approximation; all CNS isolates and a subset of S. aureus isolates were examined by PCR for ermA , ermC , and msrA . Of 114 erythromycin-resistant S. aureus isolates, 39 demonstrated constitutive resistance to clindamycin, while 33 showed inducible resistance by disk approximation at all three distances. Only one isolate failed to clearly demonstrate induction at 26 mm. Of 82 erythromycin-resistant CNS isolates that contained ermA or ermC , 57 demonstrated constitutive clindamycin resistance, and 25 demonstrated inducible resistance, at 20 and 26 mm. None of the 42 S. aureus isolates or 18 CNS isolates containing only msrA and none of the erythromycin-susceptible isolates yielded positive disk approximation tests. Simple placement of erythromycin and clindamycin disks at a distance achieved with a standard disk dispenser allowed detection of 97% of S. aureus strains and 100% of CNS strains with inducible MLS B resistance in this study.

OBJECTIVES: The present study was aimed to investigate the antibiotic resistance, virulence potential and phylogenetic grouping of ESBL-producing uropathogenic Escherichia coli (EP-UPEC) isolated from long-term hospitalized patients. MATERIALS AND METHODS: EP-UPEC isolates from September 2013 to June 2014 at a tertiary care hospital of China were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic resistance testing, PCR of different ESBL and virulence genes, and phylogenetic grouping. RESULTS: One hundred and twenty EP-UPEC were isolated from long-term hospitalized patients. All EP-UPEC isolates were resistant to Ampicillin, Cefazolin, Cefuroxime, Cefotaxime, Cefoperazone and Ceftriaxone, and the majority of EP-UPEC isolates were resistant to Piperacillin (82.5%), Ciprofloxacin (81.2%), Trimethoprim-Sulfamethoxazole (72.5%). The isolates showed the highest sensitivity against Imipenem (98.4%), Piperacillin/tazobactam (96.7%), Cefoperazone/sulbactam (91.7%), Amikacin (90.8%) and Cefepime (75.8%). Nine different ESBL genotype patterns were observed and CTX-M type was the most prevalent ESBL genotype (42.5%, 51/120). Majority of EP-UPEC isolates possess more than one ESBL genes. EP-UPEC isolates belonged mainly to phylogenetic group B2(36.7%) and D(35.0%). The prevalence of traT, ompT, iss, PAI, afa, fimH and papC were 75.8%, 63.3%, 63.3%, 60.8%, 40.8%, 19.2% and 6.7%, respectively. The number of virulence genes (VGs) detected was significantly higher in group B2 than in group A (ANOVA, p

Bactérias produtoras de metalo-beta-lactamases (MBLs) são em grande parte resistentes aos betalactâmicos de largo espectro, incluindo oximino-aminotiazol cefalosporinas e também aos carbapenens. O objetivo deste trabalho foi detectar cepas de Pseudomonas aeruginosa resistentes ao imipenem e à ceftazidima, assim como identificar aquelas produtoras de MBLs. Foram estudadas 198 linhagens não-repetitivas isoladas de diversas amostras clínicas, hospitalares e comunitárias, identificadas bioquimicamente por técnicas de rotina. A triagem para a detecção de amostras produtoras de MBLs foi realizada pelo método de dupla difusão proposto por Arakawa et al. (2000) e modificado por Nakajima et al. (2001), utilizando discos contendo mercaptoacetato de sódio. Foi detectado um percentual de resistência de 19,7% (39/198) ao imipenem e de 15,2% (30/198) à ceftazidima, com 10,1% (20/198) de resistência cruzada aos dois antimicrobianos. Entre estas amostras, 2% (4/198) demonstraram produção de MBLs e padrão de multirresistência. A detecção destas amostras configura um problema emergente, com importantes implicações na terapêutica antimicrobiana, necessitando, portanto, de maior investigação através de metodologia molecular, para melhor caracterizar a extensão do problema. Producers of metallo-beta-lactamases (MBLs) have been shown to confer resistance to carbapenems. The present study was undertaken to evaluate the presence of resistance to imipenem and oxymino cephalosporins, as well as MBLs production among clinical isolates of Pseudomonas aeruginosa in João Pessoa-PB, Brazil. A total of 198 non-repetitive strains of P. aeruginosa identified by routine techniques were studied. These strains were screened for MBL production, using the double disk diffusion test previously described by Arakawa et al. (2000), as modified by Nakajima et al. (2001), using disks containing sodium mercaptoacetate as inhibitor of MBL. Strains were considered to be MBL producer when they demonstrated a typical expansion in the inhibitory zone by the presence of thiol compound. A total of four strains (2%) showed positive results among the isolates tested. Our findings indicate that the appearance of metallo-beta-lactamase in Pseudomonas aeruginosa strains is an emerging problem, with important therapeutic implications, and this fact needs further investigation including the use of molecular methodologies to fully characterize the extent of the problem.

Background Early detection of carbapenem-resistant Enterobacteriaceae(CRE) is crucial for selection of effective treatment. While KPC is the most prevalent carbapenemase in the US, phenotypic screening methods, such as the carbapenemase inactivation method (CIM) and CarbaNP, cannot easily distinguish between serine and metallo-β-lactamases (MBL). The aim of this study was to evaluate a simple double disk diffusion (DD) test to confirm carbapenem (meropenem) resistance (MER disk) and that resistance was due to a serine carbapenemase as indicated by susceptibility to ceftazidime-avibactam (CAZ-AVI disk). MBL-producing organisms are likely to be resistant to both MER and CAZ-AVI. Methods In total, 83 clinical isolates of Enterobacteriaceae were selected for the validation: 54 Klebsiella pneumoniae (KP), 16 Enterobacter cloacae (ECL) and 13 Escherichia coli (EC). All isolates were screened for specific β-lactamase genes (Checkpoints, Wageningen, Netherlands) and included KPC, OXA, IMP, VIM, NDM as well as strains with KPC and alterations on OmpK35 and OmpK36. Isolates were tested for susceptibility to MER and CAZ-AVI by disk diffusion and broth microdilution (BMD) per CLSI guidelines. Results were analyzed to evaluate suitability of the DD test to distinguish between serine and MBL-producing organisms. Results Overall correlation between disk and BMD was 97–100% for CAZ-AVI and 94–100% for MER. Among the 50 CRE that were susceptible to CAZ-AVI were strains positive for KPC, or OXA, or in combination with ESBLs. Among the 16 isolates that were resistant to both CAZ-AVI and MER were strains that produced MBLs such as IMP, VIM and NDM and included strains with alteration in OmpK35 and OmpK36. Among the 17 carbapenem-susceptible control strains all were susceptible to both agents and were positive for AmpC or ESBLs. Conclusion The CAZ-AVI and MER DD test was successful in confirming CRE phenotype and in distinguishing between serine carbapenemase-producing and MBL-producing organisms. The test will be useful in screening patients in future trials to evaluate the efficacy of CAZ-AVI in global CRE studies where MBL’s are more prevalent in other geographic regions. Both disks are commercially available and can be performed in most clinical laboratories. Disclosures L. Y. Lin, Allergan plc: Employee, Salary; I. Critchley, Allergan plc: Employee, Salary; D. Melnick, Allergan plc: Employee, Salary

Clindamycin is a possible antibiotic treatment of infections by Gram-positive cocci. However, its use can be limited by inducible clindamycin resistance. To screen for the presence of this type of resistance, the D-zone test is used. The aim of this study was to compare the performance of SirScan paper disks with that of Rosco Neo-Sensitabs for the D-zone test at distances according to dispensers provided by the manufacturers (25 mm) and when the disks are placed at a distance of 15 mm. We studied 364 Gram-stain-positive cocci representing clinical isolates that were resistant to erythromycin and susceptible to clindamycin. Out of these isolates, 207 (57%) gave a positive D-zone test result at 25 mm distance using SirScan paper disks. When the test was repeated with the same disks placed 15 mm from the 157 (43%) isolates that had previously given a negative result, 58 (36.9%) gave a positive D-zone test result. The same isolates were also found to test positive when Rosco Neo-Sensitabs were used. Placing the disks at a distance of 15 mm instead of 25 mm led to an 84.3% increase in positive D-tests among Staphylococcus aureus, 43.8% among group B streptococci (GBS) and 6.4% among coagulase-negative staphylococci (CNS). In conclusion, the SirScan paper disks are equivalent to Rosco Neo-Sensitabs in screening for inducible resistance to clindamycin. The D-test needs to be performed at a shorter distance (15 mm) to prevent false-negative reporting.

A new extended-spectrum beta-lactamase with an isoelectric point (pI) of 6.2 was detected in Klebsiella pneumoniae F161 that was isolated from a patient with infection. This strain was highly resistant to the third or fourth generation cephalosporins such as ceftazidime, ceftriaxone, cefoperazone, and cefpirome. Analysis of this strain by the double disk diffusion test showed synergies between amoxicillin-clavulanate (AMX-CA) and cefotaxime, and AMX-CA and aztreonam, which suggested that this strain produced a extended-spectrum beta-lactamase (ESBL). Genetic analysis revealed that the resistance was due to the presence of a 9.4-kb plasmid, designated as pKP161, encoding for new beta-lactamase gene (bla). Sequence analysis showed that a new bla gene of pKP161 differed from bla(TEM-1) by three mutations leading to the following amino acid substitutions: Val84 --> Ile, Ala184 --> Val, and Gly238 --> Ser. These mutations have not been reported previously in the TEM type beta-lactamases produced by clinical strains. The novel beta-lactamase was overexpressed in E. coli and purified by ion exchange chromatography on Q-Sepharose and CM-Sepharose, and then further purified by gel filtration on Sehadex G-200. The catalytic activity of the purified beta-lactamase was confirmed by the nitrocefin disk.

BackgroundResistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.MethodsA total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003-2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).ResultsWe identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.ConclusionThe prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for blaCTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.

This study evaluated an agar disk diffusion D-zone test and an erythromycin-clindamycin (ERY + CLI) single-well broth test for inducible CLI resistance in Streptococcus pneumoniae . The standard CLSI disk approximation test and a single-well combination test incorporating 1 plus 0.5 μg/ml ERY + CLI detected >96% of isolates containing the ermB determinant.

This paper reports on the in vitro antimicrobial activity of ampicillin-ceftriaxone and ampicillin-ertapenem combinations against five strains of E. faecalis with high-level aminoglycoside resistance recovered from blood of septicemic patients. Double disk diffusion test and time killing curves were used. A bacteriostatic synergistic effect between ampicillin and ceftriaxone was detected using the disk diffusion assay for three of the five enterococcal strains studied. With the same three isolates enhanced bactericidal activity was also observed using time killing experiments. Overall, for these three strains, after 24 hr of contact, a decrease >/= 2 log(10) from the initial bacterial inoculum was registered with most ampicillin-ceftriaxone combinations, reaching with some of them a colony reduction >/= 3 log(10). This bactericidal interaction was negatively influenced increasing the bacterial inoculum. In all five isolates neither a bacteriostatic nor a bactericidal cooperation was observed for ampicillin combined with 2 mg/l of ertapenem.This investigation broadened the evidence of antimicrobial synergism in vitro between ampicillin and ceftriaxone in selected strains of Enterococcus faecalis with high-level aminoglycoside resistance.

In total, 269 methicillin-resistant Staphylococcus aureus (MRSA) and 434 methicillin-susceptible S. aureus (MSSA) isolates were investigated to determine their macrolide–lincosamide–streptogramin B (MLSB) resistance phenotypes and genotypes. The constitutive phenotype (61.3% in MRSA, 1.3% in MSSA) and erm(A) gene predominated among the 261 erythromycin-resistant MRSA isolates, while the inducible phenotype (38.7% in MRSA, 94.0% in MSSA) and erm(C) gene were more prevalent among the 150 erythromycin-resistant MSSA isolates. There was a higher incidence of the MLSB inducible phenotype compared with other countries, perhaps because MLSB antibiotics are not recommended as first-line agents against S. aureus in Japan.

Urinary tract infections (UTIs) are common with an annual global incidence of at least 250 million cases; and Escherichia coli is the most common pathogen (1). Trimethoprim/sulfamethoxazole (SMX) has been used successfully to treat community-acquired UTI (CA-UTI) previously, but fluoroquinolones (FQ) are currently being used more frequently as the first-line treatment because of the increasing resistance to SMX among uropathogens (2). However, FQ-resistant E. coli is increasing recently in most countries, which becomes a great concern for public health worldwide. Several studies have reported that FQ resistance rate of E. coli in Korea reached 30%, indicating that Korea is one of hot spots for antimicrobial resistance of E. coli (3). Increasing trend of multi-drug resistance of E. coli from CA-UTI requires other treatment options. In terms of candidate antibiotics for CA-UTI, especially for cystitis which is very common but not serious infection in community, selective pressure by antibiotics as well as treatment efficiency should be carefully considered. With this perspective, fosfomycin (FM), nitrofurantoin (NI) and temocillin (TMO) would be good candidate antibiotics for uncomplicated cystitis from community. In brief, FM has been extensively used in several European countries for the treatment of uncomplicated UTI since 1988. Despite many years of treatment use, FM continues to be characterized by low resistance of 1% against E. coli strains worldwide (4). NI is also an old drug used for uncomplicated UTI, but its use is limited because of nephrotoxicity. Nevertheless, the potential role of NI for uncomplicated UTI in the growing resistance era has been presented (5, 6). In Korea, there has been a report for in vitro activity of FM (7), but no report for TMO or NI against E. coli isolates from urine. Objective of this study was to figure out the minimal inhibitory concentration (MIC) distribution of candidate antibiotics against uropathogenic E. coli from CA-UTI in Korea. As part of a nationwide multicenter surveillance study, a total of 346 community-acquired E. coli from patients with UTI were collected from April 2010 to March 2011. The isolates were from 12 hospitals with 582-250 beds each, located throughout the Korean peninsula (3 in Seoul, 4 in Gyeonggi-do, 2 in Incheon, 2 in Daegu and 1 in Busan), and 11 were academic hospitals. The study was approved by the institutional review board (IRB) of Hanyang University Hospital (2010-007). Only the first isolate from each patient was included in the study. Susceptibility to FM, TMO, NI, ciprofloxacin (CIP), SMX and cefepime (FEP) was examined. The MIC of FM, TMO, NI, CIP, and FEP was determined by E-test (bioMerieux, Marcy L'Etoile, France), and SMX by agar dilution method according to Clinical and Laboratory Standards Institute (CLSI) guildeline (8). Quality control was performed using E. coli ATCC 25922. Extended-spectrum beta-lactamase (ESBL)-positivity was defined by extended-spectrum beta-lactamase test in either a semi-automated system or double disk diffusion test. We considered the isolates as plasmid-mediated AmpC beta-lactamase (PABL)-producers when they were resistant to extended-spectrum cephalosporins (ESC) but Extended-spectrum beta-lactamase test was negative. A total of 346 E. coli isolates were collected in urine and/or blood cultures. The susceptibility rates of antibiotics were as follows: FM 100% (346/346), TMO 96.8% (335/346), NI 99.4% (344/346), FEP 98.5% (341/346), CIP 78% (270/346) and SMX 70.8% (245/346). The MIC50 and MIC90 values (µg/mL) of each antibiotic were measured: FM, 0.5, 1.5; TMO, 4, 12; NI, 4, 8; FEP, 0.016, 0.064; CIP 0.016, >32; SMX

Background: Streptococcus pyogenes is the most common cause of bacterial pharyngitis. T antigens and emm genotypes are essential markers for an epidemiological study of S. pyogenes. Macrolide resistance of S. pyogenes is a serious obstracle to successfully treating a sore throat. Methods: One-hundred forty-seven strains of S. pyogenes isolated from healthy school children in 2006 were subjected to T typing and emm genotyping. A disk diffusion method was applied for several antibiotics. A double disk diffusion test was performed to evaluate the phenotype distribution of macrolide resistance. Results: Among T antigens and emm genotypes, T11 (19.7%) and emm78 (16.7%), respectively, were the most common in 2006. Both T5/27/44 (2.3%) and emm44/61 (9.1%) declined to a great extent from about 29% in 2004. The rate of resistance to antibiotics were 11.6% to erythromycin, 4.8% to clindamycin, 21.8% to tetracycline, and 7.5% to ofloxacin. M and cMLSB phenotypes were 52.9% and 41.2% respectively. Conclusion: T typing and emm genotyping proved a dynamic change in their distribution in 2006 compared to the results of 2004. Erythromycin and clindamycin resistance remained low as in 2004, whereas ofloxacin resistance increased slightly. M and cMLSB phenotypes were equivalent in 2006, whereas cMLSB was predominant in 2004. (Korean J Clin Microbiol 2009;12:6-10)

OBJECTIVE: To understand the mechanisms and epidemiology of resistance to oxyiminocephalosporins in Escherichia coli over a 2-year period in a French hospital. METHODS: Forty-four strains, resistant or intermediately resistant to one of the oxyiminocephalosporins or aztreonam, were collected from 35 patients. MIC determinations were carried out for the 44 isolates using a panel of beta-lactam antibiotics, and characterization of the beta-lactamases they produced by isoelectric focusing and catalytic activity measurement. Extended-spectrum beta-lactamase production was studied by use of the double disk diffusion test. Conjugation experiments were used to search for plasmidic cephalosporinase. An epidemiologic study was then performed, by use of molecular typing of the strains with an ERIC-PCR method and a case-control analysis. RESULTS: Less than 1% of all the E. coli isolates at our hospital showed decreased susceptibility to oxyiminocephalosporins. Only three of the 44 isolates showed synergy between clavulanate and a third-generation cephalosporin and produced an extended-spectrum beta-lactamase. For the other strains, a beta-lactamase with a highly basic isoelectric point was detected. Spectrophotometric measures confirmed that most of these isolates were AmpC hyper-producers. No plasmidic cephalosporinase could be detected by conjugation experiments. Molecular typing showed all isolates to be different, except for two strains isolated in two patients of the same hospital unit, and for the repeated isolates of some patients. When 20 case patients were compared to 40 randomly selected control patients, prior receipt of an antimicrobial and more specifically of a beta-lactam agent was significantly associated with case patients. CONCLUSIONS: Although it appears to be very rare, the resistance to broad-spectrum cephalosporins needs our attention, because of the high frequency of E. coli infections and beta-lactam use in their treatment.

High-level clindamycin resistance in Bacteroides species was investigated by measuring zone sizes surrounding 2 micrograms clindamycin and 60 micrograms erythromycin discs, using a nonstandardized disc diffusion method, and by determining minimal inhibitory concentrations (MIC). The absence of a zone of inhibition surrounding either disc was predictive for all isolates having high-level resistance to both antibiotics (MIC greater than 256 micrograms/ml), characteristic of macrolide-lincosamide-streptogramin (MLS) cross-resistance. Although zone size could not be used as an absolute predictor of MIC, a clindamycin zone diameter of less than 17 mm was suggestive of strains with a moderate level of clindamycin resistance (MIC greater than or equal to 8 micrograms/ml), regardless of erythromycin zone size. Disc diffusion testing using a combination of clindamycin and erythromycin discs can be a useful screening method for detection of clindamycin-resistant Bacteroides species, occurring either alone or as part of the MLS resistance phenotype.

Purpose: The incidence of extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia coli and Klebsiella pneumoniae is increasing worldwide, which may change empiric antibiotic treatment. This study was conducted to explore the increasing extent of the incidence of ESBLproducing strains (ESBLPS) in E. coli and K. pneumoniae. Methods: This was a retrospective study at a regional hospital in southern Taiwan. From 2009 to 2013, all E. coli and K. pneumoniae isolates from clinical microbiology laboratory were enrolled in this study. ESBLPS were confirmed by double disk diffusion test. Results: A total of 15954E. coli and5374K. pneumoniae isolateswere enrolled. The ESBLPS accounted for 10.7 % (325/3048) and 16.8% (186/1109), 12.1% (362/ 2989) and 16.1% (155/963), 13.3% (447/3359) and 19.2% (214/1112), 17.4% (633/3635) and 20.8% (219/1051), as well as 20.5 % (753/2923) and 20.2% (230/1139) of E. coli and K. pneumoniae isolates in 2009, 2010, 2011, 2012, and 2013, respectively. The incidence of ESBLPS of E. coli and K. pneumoniae was statistically significant difference between 2009 and 2013 (P < 0.05). Conclusions: As a result of this study, the incidence of ESBLPS of E. coli and K. pneumniae was statistically significant increase from 2009 to 2013 (10.7% versus 20.5% in E. coli and 16.8% versus 20.2% in K. pneumoniae). The incidence of ESBLPS of E. coli was lower than that of K. pneumoniae before 2012, but that was similar in 2013. We think that the rapid increase of ESBLPS of E. coli should be concerned in clinical practice because E. coli is more frequent organism causing infections than K. pneumoniae.