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Learning strategies represent an important tool in the teaching process for students and teachers. A quantitative descriptive-correlational study was carried out that aimed to describe and analyze the use of learning strategies through an instrument and correlate them with academic performance, in a sample of students from seventh primary to eleventh secondary at a school in Chile. (N=408). The results show a low use of the four strategies at all school levels, observing a strong and significant correlation obtained through the Pearson coefficient between academic performance and all strategies in the eleventh secondary. The need to generate psychoeducational spaces that allow both teachers and students to learn to use learning strategies is discussed. The role of the support strategy in generating a positive learning climate is highlighted. [ABSTRACT FROM AUTHOR]

Background: Acral lentiginous melanoma (ALM) is a highly malignant and invasive type of melanoma with unique locations of onset. Its incidence is increasing and early diagnosis is challenging. Reflectance confocal microscopy (RCM) is a non‐invasive technique that provides an accurate image of tissue pathology. There are few reports on the use of RCM for the assessment of ALM. Materials and methods: In this retrospective study, data from 31 patients with a clinical diagnosis of ALM were collected. RCM image features were compared with histopathological findings to determine the concordance between the two methods. The sensitivity, specificity, positive predictive value, and negative predictive value of RCM for the diagnosis of ALM were evaluated. Results: RCM and histopathology findings were concordant in 29 of 31 patients (93.5%). There were no false‐negative results, although there were two false positives in RCM diagnosis. The sensitivity of RCM for diagnosing ALM was 100%, specificity was 50%, positive predictive value was 93.1%, and negative predictive value was 100%. Conclusions: RCM showed substantial concordance with histopathology in the diagnosis of ALM. It is a reliable and valuable non‐invasive diagnostic tool that holds promise for the early diagnosis of ALM. [ABSTRACT FROM AUTHOR]

ABSTRACTGastrointestinal (GI) colonization by Klebsiella pneumoniae is a risk factor for subsequent infection as well as transmission to other patients. Additionally, colonization is achieved by many strain types that exhibit high diversity in genetic content. Thus, we aimed to study strain-specific requirements for K. pneumoniae GI colonization by applying transposon insertion sequencing to three classical clinical strains: a carbapenem-resistant strain, an extended-spectrum beta-lactamase-producing strain, and a non-epidemic antibiotic-susceptible strain. The transposon insertion libraries were screened in a murine model of GI colonization. At 3 days post-inoculation, 27 genes were required by all three strains for colonization. Isogenic deletion mutants for three genes/operons (acrA, carAB, and tatABCD) confirmed colonization defects in each of the three strains. Additionally, deletion of acrA reduced bile tolerance in vitro, while complementation restored both bile tolerance in vitro and colonization ability in vivo. Transposon insertion sequencing suggested that some genes were more important for the colonization of one strain than the others. For example, deletion of the sucrose porin-encoding gene scrY resulted in a colonization defect in the carbapenemase-producing strain but not in the extended-spectrum beta-lactamase producer or the antibiotic-susceptible strain. These findings demonstrate that classical K. pneumoniae strains use both shared and strain-specific strategies to colonize the mouse GI tract.IMPORTANCEKlebsiella pneumoniae is a common cause of difficult-to-treat infections due to its propensity to express resistance to many antibiotics. For example, carbapenem-resistant K. pneumoniae has been named an urgent threat by the United States Centers for Disease Control and Prevention. Gastrointestinal colonization in patients with K. pneumoniae has been linked to subsequent infection, making it a key process to control in the prevention of multidrug-resistant infections. However, the bacterial factors which contribute to K. pneumoniae colonization are not well understood. Additionally, individual strains exhibit large amounts of genetic diversity, begging the question of whether some colonization factors are strain dependent. This study identifies the enteric colonization factors of three classical strains using transposon mutant screens to define a core colonization program for K. pneumoniae as well as detecting strain-to-strain differences in colonization strategies.

Multidrug-resistant (MDR) gram-negative bacteria pose significant challenges to the public health. Various factors are involved in the development and spread of MDR strains, including the overuse and misuse of antibiotics, the lack of new antibiotics being developed, and etc. Efflux pump is one of the most important factors in the emergence of antibiotic resistance in bacteria. Aiming at the introduction of novel plant antibiotic, we investigated the effect of eugenol on the MexA and AcrA efflux pumps in Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). Molecular docking was performed using PachDock Server 1.3. The effect of eugenol on bacteria was determined by disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). A cartwheel test was also performed to evaluate efflux pump inhibition. Finally, the expression of the MexA and AcrA genes was examined by real-time PCR. The results of molecular docking showed that eugenol interacted with MexA and AcrA pumps at − 29.28 and − 28.59 Kcal.mol−1, respectively. The results of the antibiogram test indicated that the antibiotic resistance of the treated bacteria decreased significantly (p < 0.05). The results of the cartwheel test suggested the inhibition of efflux pump activity in P. aeruginosa and E. coli. Analysis of the genes by real-time PCR demonstrated that the expression of MexA and AcrA genes was significantly reduced, compared to untreated bacteria (p < 0.001). The findings suggest, among other things, that eugenol may make P. aeruginosa and E. coli more sensitive to antibiotics and that it could be used as an inhibitor to prevent bacteria from becoming resistant to antibiotics. [ABSTRACT FROM AUTHOR]

Efflux pumps are a relevant factor in antimicrobial resistance. In E. coli, the tripartite efflux pump AcrAB-TolC removes a chemically diverse set of antibiotics from the bacterium. Therefore, small molecules interfering with efflux pump function are considered adjuvants for improving antimicrobial therapies. Several compounds targeting the periplasmic adapter protein AcrA and the efflux pump AcrB have been identified to act synergistically with different antibiotics. Among those, several 4(3-aminocyclobutyl)pyrimidin-2-amines have been shown to bind to both proteins. In this study, we intended to identify analogs of these substances with improved binding affinity to AcrA using virtual screening followed by experimental validation. While we succeeded in identifying several compounds showing a synergistic effect with erythromycin on E. coli, biophysical studies suggested that 4(3-aminocyclobutyl)pyrimidin-2-amines form colloidal aggregates that do not bind specifically to AcrA. Therefore, these substances are not suited for further development. Our study emphasizes the importance of implementing additional control experiments to identify aggregators among bioactive compounds. [ABSTRACT FROM AUTHOR]

Characterizing protein-protein interaction on a single molecular level is a challenge, experimentally as well as interpretation of the data. For example, Gram-negative bacteria contain protein complexes spanning the outer and inner cell wall devoted to efflux effectively cell toxic substances. Recent seminal work revealed the high-resolution structure of such a tripartic composition TolC-AcrA-AcrB suggesting to design inhibitors preventing efflux of antibiotics. To show that electrophysiology can provide supporting information here, we reconstitute single TolC homotrimer into a planar lipid membrane, apply a transmembrane voltage and follow the assembly of AcrA to TolC using the modulation of the ion current through TolC channel during binding. In particular, the presence of AcrA in solution increases the average ionic current through TolC and, moreover, reduces the ion-current fluctuations caused by flickering of TolC. Here, we show that statistical properties of ion-current fluctuations (the power spectral density) provide a complementary measure of the interaction of the TolC-AcrA complex in presence of putative efflux pump inhibitors. Both characteristics, the average ion current across TolC and the current noise, taken into consideration together, point to a stiffening of the tip of TolC which might reduce the formation of the complex. [Display omitted] • Binding of AcrA to single TolC channel modulates the ion current. • The TolC flickering is pronounced at 1–3 kHz. • The periplasmic end of TolC is flexible, AcrA stabilize the open form. [ABSTRACT FROM AUTHOR]

Many infections produced by multidrug-resistant (MDR) Klebsiella pneumoniae are the main cause of death and treatment restrictions worldwide. In K. pneumoniae, the efflux pump system is dangerous in drug resistance. Therefore, this study was designed to investigate the involvement of the AcrA and AcrB efflux pumps in antibiotic resistance in Klebsiella pneumoniae isolated from wound patients. During June 2021-February 2022, 87 clinical isolates of Klebsiella pneumonia bacteria were obtained from wound samples patients consulted to the hospitals in AL-Diwaniyah province, Iraq. The disc diffusion method performed an antibiotic susceptibility test after microbiological/biochemical identification. The polymerase chain reaction (PCR) technique was used to examine efflux genes' prevalence (acrA and acrB). The results showed that resistance to Carbenicillin 72 (82.7%), Erythromycin 66 (75.8%), Rifampin 58 (66.6%), Ceftazidime 52 (59.7%), Cefotaxime 44 (50.5%), Novobiocin 38 (43.6%), Tetracycline 32 (36.7%), Ciprofloxacin 22 (25.2%), Gentamicin 16 (18.3%), Nitrofurantoin 6 (10.3%) in Klebsiella pneumoniae isolates. The PCR procedure revealed that the occurrence of the acrA and acrB genes is 55 (100%) and 55 (100%), respectively. The findings of this investigation show that the AcrA and AcrB efflux pumps play a crucial character in antibiotic resistance in multidrug-resistant Klebsiella pneumoniae bacterial isolates. As a result of the unintentional transmission of antimicrobial resistance genes, precise detection of resistance genes using molecular approaches is required to switch the extent of resistant strains. [ABSTRACT FROM AUTHOR]

Efflux pumps are a relevant factor in antimicrobial resistance. In E. coli, the tripartite efflux pump AcrAB-TolC removes a chemically diverse set of antibiotics from the bacterium. Therefore, small molecules interfering with efflux pump function are considered adjuvants for improving antimicrobial therapies. Several compounds targeting the periplasmic adapter protein AcrA and the efflux pump AcrB have been identified to act synergistically with different antibiotics. Among those, several 4(3-aminocyclobutyl)pyrimidin-2-amines have been shown to bind to both proteins. In this study, we intended to identify analogs of these substances with improved binding affinity to AcrA using virtual screening followed by experimental validation. While we succeeded in identifying several compounds showing a synergistic effect with erythromycin on E. coli, biophysical studies suggested that 4(3-aminocyclobutyl)pyrimidin-2-amines form colloidal aggregates that do not bind specifically to AcrA. Therefore, these substances are not suited for further development. Our study emphasizes the importance of implementing additional control experiments to identify aggregators among bioactive compounds.

Background and Objective: Moraxella catarrhalis a gram-negative bacterium, is a significant cause of lower and upper respiratory infections. The RND family efflux pumps lead to multidrug resistance in gram-negative bacteria. One of the well-known pumps in M. catarrhalis is AcrAB-OprM system. This study aimed to investigate the antibiotic resistance in M. catarrhalis and to determine its antibiotic resistance dependence on the efflux pump. Methods: In this study, 137 different clinical samples were collected. M. catarrhalis isolates were confirmed by biochemical assays and PCR. The antibiotic susceptibility pattern was investigated by disc diffusion method according to CLSI. Phenotypic study of the efflux pumps activity was done using cartwheel method. Study of the acra, acrb, and oprm genes were performed by, PCR. In addition, the association of efflux pump with antibiotic resistance was investigated using phenylalanine-arginine β-naphthylamide. Results: Of 10 isolated M. catarrhalis, 70% (7 isolates) showed multiple antibiotic resistance. The resistance to cefazolin, ceftazidime, tetracycline, chloramphenicol, and ciprofloxacin antibiotics was also dependent on the efflux pump. Conclusion: The results showed that multiple antibiotic resistance has increased in Moraxella catarrhalis. The 70% presence of acra, acrb, oprm efflux genes of the efflux pumps in this bacterium and antibiotic resistance reduction in the presence of efflux pump inhibitor shows the importance of examining these genes’ presence to suggest a suitable treatment model for the patients infected with M. catarrhalis.

Undergraduate training continues to be a challenge to train entrepreneurial specialists with research-oriented attitudes. Depending on the level of functional development of the brain, the level of learning will be differ-ent in relation to chronological age. The ACRA learning strategies scales [1] allow verifying the frequency, type of strategy and specific technique used by students, the coding strategies being the most important for effective performance throughout life; although there is an abbreviated and validated version of this scale applicable only at the university level by [2] De la Fuente and Justicia (2003); In the study, the 2001 version of [1] is applied to analyze, according to age, the correspondence between the learning strategies used by the students with their academic performance, as well as to verify if there is a difference by gender, during a period of three years. Technical sheets and final grades of the students were also applied; a multiple linear regression analysis; it is a mixed type investigation. It is observed that the Coding strategies are not used very frequently. In Academic Performance (AR), only 7.85% of the students obtained a final score of 14 or more, the use score coinciding with scales that measure the same learning strategies. The type of strategies and the age (18-19 years) registered influence the RA and only the Acquisition strategies show a slight rela-tionship with the RA. There is no gender relationship. [ABSTRACT FROM AUTHOR]

Background: Moraxella catarrhalis a gram-negative bacterium, is a significant cause of lower and upper respiratory infections. The RND family efflux pumps lead to multidrug resistance in gram-negative bacteria. One of the well-known pumps in M. catarrhalis is AcrAB-OprM system. This study aimed to investigate the antibiotic resistance in M. catarrhalis and to determine its antibiotic resistance dependence on the efflux pump. Methods: In this study, 137 different clinical samples were collected. M. catarrhalis isolates were confirmed by biochemical assays and PCR. The antibiotic susceptibility pattern was investigated by disc diffusion method according to CLSI. Phenotypic study of the efflux pumps activity was done using cartwheel method. Study of the acra, acrb, and oprm genes were performed by, PCR. In addition, the association of efflux pump with antibiotic resistance was investigated using phenylalanine-arginine β-naphthylamide. Results: Of 10 isolated M. catarrhalis, 70% (7 isolates) showed multiple antibiotic resistance. The resistance to cefazolin, ceftazidime, tetracycline, chloramphenicol, and ciprofloxacin antibiotics was also dependent on the efflux pump. Conclusion: The results showed that multiple antibiotic resistance has increased in Moraxella catarrhalis. The 70% presence of acra, acrb, oprm efflux genes of the efflux pumps in this bacterium and antibiotic resistance reduction in the presence of efflux pump inhibitor shows the importance of examining these genes’ presence to suggest a suitable treatment model for the patients infected with M. catarrhalis. [ABSTRACT FROM AUTHOR]

With the amelioration of digital technology, study of Online Social Networks (OSNs) like Twitter has gain a lot of attention from research community. Analysing OSN data enhances the understanding of relationships among people to address several issues regarding society. OSN data as a graph depicts people/user as node and their relationship as link/edge. Influence Analysis is an important area of research on OSN data. It analyses the links between users to identify influential node in the network graph. Graph database and processing models are suitable to perform such analysis. Neo4j a Graph Database facilitates to store, to portray relationships, to study the connection between users and user-friendly visualization of Twitter data. Study of Twitter metrics create opportunities for researchers and scientist for identifying topical influential node. This research aims to identify and rank topical influential nodes and propose algorithm i.e. Aggregation Consensus Rank Algorithm (ACRA) that combines various selected Twitter metrics to generate top-k influencer list. ACRA is applied on time intervals-based data for identification and ranking of influential nodes. The experimental results of proposed algorithm are evaluated against standard metrics. The results show that ACRA perform better for selected metric set as compared to other approaches. [ABSTRACT FROM AUTHOR]

La presente investigación tuvo como propósito evaluar la validez y confiabilidad de las Escalas de Estrategias de Aprendizaje ACRA en una población de alumnos en tres universidades peruanas: Universidad Peruana Cayetano Heredia, Universidad Nacional Mayor de San Marcos y Universidad Nacional Federico Villarreal. El muestreo fue intencional y estuvo constituida por 569 personas: 269 hombres y 302 mujeres. Se empleó la metodología para encontrar la consistencia interna por mitades y homogeneidad del análisis de ítems y la validez de constructo por análisis factorial; además de la derivación de baremos, los mismos que se expresan en percentiles. Las principales conclusiones indican que el ACRA es un instrumento confiable respecto a su consistencia interna en una población universitaria diversa, y demuestra ser un instrumento válido en las cuatro escalas analizadas (Adquisición, Codificación, Recuperación y Apoyo).

Bacterial efflux pumps confer multidrug resistance by transporting diverse antibiotics from the cell. In Gram-negative bacteria, some of these pumps form multi-protein assemblies that span the cell envelope. Here, we report the near-atomic resolution cryoEM structures of the Escherichia coli AcrAB-TolC multidrug efflux pump in resting and drug transport states, revealing a quaternary structural switch that allosterically couples and synchronizes initial ligand binding with channel opening. Within the transport-activated state, the channel remains open even though the pump cycles through three distinct conformations. Collectively, our data provide a dynamic mechanism for the assembly and operation of the AcrAB-TolC pump.

Miastenia Gravis is a neuromuscular disease caused by auto antibodies. Early Clinical and biochemical diagnosis and treatment is demanded in the assurementof quality and time of life in all dogs. In this study we describe the conventional diagnosis methods and therapy in 32 dogs with suspected myasthenia gravis and propose the administration of bromide of piridostigmin as another use full diagnosis method in dogs.

ABSTRACT Salicylic acid (SA) is an important signaling molecule in local and systemic plant resistance. Following infection by microbial pathogens and the initial oxidative burst in plants, SA accumulation functions in the amplification of defense gene expression. Production of pathogenesis-related proteins and toxic antimicrobial chemicals serves to protect the plant from infection. Successful microbial pathogens utilize a variety of mechanisms to rid themselves of toxic antimicrobial compounds. Important among these mechanisms are multidrug-resistance pumps that bring about the active efflux of toxic compounds from microbial cells. Here, we show that a combination SA and its precursors, t-cinnamic acid and benzoic acid, can activate expression of specific multidrug efflux pump-encoding genes in the plant pathogen Erwinia chrysanthemi and enhance survival of the bacterium in the presence of model as well as plant-derived antimicrobial chemicals. This ability of plant-pathogenic bacteria to co-opt plant defense-signaling molecules to activate multidrug efflux pumps may have evolved to ensure bacterial survival in susceptible host plants.

Over-expression of multidrug efflux pumps of the Resistance Nodulation Division (RND) protein super family counts among the main causes for microbial resistance against pharmaceuticals. Understanding the molecular basis of this process is one of the major challenges of modern biomedical research, involving a broad range of experimental and computational techniques. Here we review the current state of RND transporter investigation employing molecular dynamics simulations providing conformational samples of transporter components to obtain insights into the functional mechanism underlying efflux pump-mediated antibiotics resistance in Escherichia coli and Pseudomonas aeruginosa.

The AcrAB-TolC multidrug efflux pump confers resistance to Escherichia coli against many antibiotics and toxic compounds. The TolC protein is an outer membrane factor that participates in the formation of type I secretion systems. The genome of Vibrio vulnificus encodes two proteins homologous to the E. coli TolC, designated TolCV1 and TolCV2. Here, we show that both TolCV1 and TolCV2 partially complement the E. coli TolC function and physically interact with the membrane fusion protein AcrA, a component of the E. coli AcrAB-TolC efflux pump. Using site-directed mutational analyses and an in vivo cross-linking assay, we demonstrated that the α-barrel tip region of TolC homologs plays a critical role in the formation of functional AcrAB-TolC efflux pumps. Our findings suggest the adapter bridging model as a general assembly mechanism for tripartite drug efflux pumps in Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Abstract: Tigecycline resistance has been attributed to ramA overexpression and subsequent acrA upregulation. The ramA locus, originally identified in Klebsiella pneumoniae, has homologues in Enterobacter and Salmonella spp. In this study, we identify in silico that the ramR binding site is also present in Citrobacter spp. and that Enterobacter, Citrobacter and Klebsiella spp. share key regulatory elements in the control of the romA–ramA locus. RACE (rapid amplification of cDNA ends) mapping indicated that there are two promoters from which romA–ramA expression can be regulated in K. pneumoniae. Correspondingly, electrophoretic binding studies clearly showed that purified RamA and RamR proteins bind to both of these promoters. Hence, there appear to be two RamR binding sites within the Klebsiella romA–ramA locus. Like MarA, RamA binds the promoter region, implying that it might be subject to autoregulation. We have identified changes within ramR in geographically distinct clinical isolates of K. pneumoniae. Intriguingly, levels of romA and ramA expression were not uniformly affected by changes within the ramR gene, thereby supporting the dual promoter finding. Furthermore, a subset of strains sustained no changes within the ramR gene but which still overexpressed the romA–ramA genes, strongly suggesting that a secondary regulator may control ramA expression. [Copyright &y& Elsevier]

This study was set up to assess the patterns of antimicrobial susceptibility and mutations in acrA-tolC genes of Shigella isolates and its association. One hundred and three isolates of Shigella spp. were tested to evaluate the antimicrobial susceptibility and mutation on acrA and tolC genes. The antimicrobial resistance profiles were: tetracycline (99%), ampicillin (85.4%), chloramphenicol (83.5%), trimethoprim (85.4%), ciprofloxacin (25.2%), cefazolin (3.9%), cefotaxime (3.9%), and gentamicin (2.9%). The rate of mutation in tolC was 90% ( S. flexneri) and 30.8% ( S. sonnei). Shigella flexneri isolates were more resistant than those of Shigella sonnei to chloramphenicol (97.8 versus 0.0%, p < 0.001) and ciprofloxacin (27.8 versus 7.7%, p = 0.106). High frequency of mutation was found in gene tolC (82.5%), but relatively less in acrA (22.3%). Shigella flexneri isolates were more mutated in tolC gene than S. sonnei (90 versus 30.8%, p < 0.001). Our study suggested that mutation of acrA and tolC may play major role in multiple antimicrobial resistance in Shigella spp. Shigella isolates are emerging which are resistant to first and third generation cephalosporin like cefazolin and cefotaxime, which is a matter of concern in terms of shigellosis treatment. [ABSTRACT FROM AUTHOR]

Abstract: RND (Resistance-Nodulation-Division) family transporters are widespread especially among Gram-negative bacteria, and catalyze the active efflux of many antibiotics and chemotherapeutic agents. They have very large periplasmic domains, and form tripartite complexes with outer membrane channels and periplasmic adaptor proteins. AcrAB–TolC complex of Escherichia coli, which pumps out a very wide range of drugs, has been studied most intensively. Early studies showed that the transporter captures even those substrates that cannot permeate across the cytoplasmic membrane, such as dianionic β-lactams, suggesting that the capture can occur from the periplasm. It was also suggested that the capture occurs from the cytoplasmic membrane/periplasm interface, because most substrates contain a sizable hydrophobic domain; however, this may simply be a reflection of the nature of the binding site within AcrB. Genetic studies of chimeric transporters showed that much of the substrate specificity is determined by their periplasmic domains. Biochemical studies with intact cells recently led to the determination of the kinetic constants of AcrB for some β-lactams, and the result confirms the old prediction that AcrB is a rather slow pump. Reconstitution of purified AcrB and its relatives showed that the pump is a drug/proton antiporter, that AcrA strongly stimulates the activity of the pump, and that AcrB seems to have a highest affinity for conjugated bile salts. Structural study with mutants of the network of charged residues in the transmembrane domain showed that protonation here produced a far-reaching conformational change, which was found to be present in one of the protomers in the asymmetric crystal structure of the wild-type AcrB. The functional rotatory hypothesis then predicts that the drug bound in the periplasmic domain is extruded through this conformational change initiated by the protonation of one of the residues in the aforementioned network, an idea that was recently supported by disulfide cross-linking as well as by the behavior of linked AcrB protomers. [Copyright &y& Elsevier]

Abstract: In Gram-negative bacteria, type I protein secretion systems and tripartite drug efflux pumps have a periplasmic membrane fusion protein (MFP) as an essential component. MFPs bridge the outer membrane factor and an inner membrane transporter, although the oligomeric state of MFPs remains unclear. The most characterized MFP AcrA connects the outer membrane factor TolC and the resistance–nodulation–division-type efflux transporter AcrB, which is a major multidrug efflux pump in Escherichia coli. MacA is the periplasmic MFP in the MacAB–TolC pump, where MacB was characterized as a macrolide-specific ATP-binding-cassette-type efflux transporter. Here, we report the crystal structure of E. coli MacA and the experimentally phased map of Actinobacillus actinomycetemcomitans MacA, which reveal a domain orientation of MacA different from that of AcrA. Notably, a hexameric assembly of MacA was found in both crystals, exhibiting a funnel-like structure with a central channel and a conical mouth. The hexameric MacA assembly was further confirmed by electron microscopy and functional studies in vitro and in vivo. The hexameric structure of MacA provides insight into the oligomeric state in the functional complex of the drug efflux pump and type I secretion system. [Copyright &y& Elsevier]

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Abstract: We studied the mechanisms of resistance to fluoroquinolones in two Citrobacter freundii strains (1.44 and 1.38) isolated from the same patient and belonging to the same clone by pulsed-field gel electrophoresis. This study allowed partial characterisation of the acrA and acrB genes of this microorganism. As previously reported, the two strains showed the same substitutions in the GyrA and ParC proteins (Thr-83→Ile and Asp-87→Tyr in GyrA and Ser-83→Ile in ParC). However, differences were observed in the amount of ciprofloxacin accumulated, with strain 1.38 showing less accumulation. Expression of genes in both strains was analysed using DNA microarrays for Escherichia coli. Ten genes were overexpressed in strain 1.38 compared with strain 1.44, including genes acrA and acrB. Nucleotide similarity between the partially sequenced acrA and acrB genes of C. freundii and E. coli was 80.7% and 85%, respectively. The acrA and acrB genes of C. freundii are similar to those described in E. coli and their overexpression may play an important role in modulating the final minimum inhibitory concentration of fluoroquinolones in collaboration with mutations in the gyrA and parC genes. [Copyright &y& Elsevier]