Fluconazole and amphotericin-B resistance are associated with increased catalase and superoxide dismutase activity in Candida albicans and Candida dubliniensis

Introduction Candida dubliniensis, a new species of Candida that has been recovered from several sites in healthy people, has been associated with recurrent episodes of oral candidiasis in AIDS and HIV-positive patients. This species is closely related to C. albicans. The enzymatic activity of C. dubliniensis in response to oxidative stress is of interest for the development of drugs to combat C. dubliniensis. Methods Fluconazole- and amphotericin B-resistant strains were generated as described by Fekete-Forgács et al. (2000). Superoxide dismutase (SOD) and catalase assays were performed as described by McCord and Fridovich (1969) and Aebi (1984), respectively. Results We demonstrated that superoxide dismutase (SOD) and catalase activities were significantly higher (p<0.05) in the fluconazole- and amphotericin B-resistant strains of C. dubliniensis and C. albicans than in the sensitive strains. The catalase and SOD activities were also significantly (p<0.01) higher in the sensitive and resistant C. albicans strains than in the respective C. dubliniensis strains. Conclusions These data suggest that C. albicans is better protected from oxidative stress than C. dubliniensis and that fluconazole, like amphotericin B, can induce oxidative stress in Candida; oxidative stress induces an adaptive response that results in a coordinated increase in catalase and SOD activities.

Investigation of class 1 integrons in Klebsiella pneumoniae clinical and microbiota isolates belonging to different phylogenetic groups in Recife, State of Pernambuco

Introduction The high prevalence of Klebsiella pneumoniae infections is related to the ability of K. pneumoniae to acquire and disseminate exogenous genes associated with mobile elements, such as R plasmids, transposons and integrons. This study investigated the presence of class 1 integrons in clinical and microbiota isolates of K. pneumoniae belonging to different phylogenetic groups and correlated these results with the antimicrobial resistance profiles of the studied isolates. Methods Of the 51 isolates of K. pneumoniae selected for this study, 29 were from multidrug-resistant clinical isolates, and 22 were from children's microbiota. The susceptibility profile was determined using the disk diffusion method, and class 1 integrons were detected through polymerase chain reaction (PCR). Results The results showed that none of the 22 microbiota isolates carried class 1 integrons. Among the 29 clinical isolates, 19 (65.5%) contained class 1 integrons, and resistance to sulfamethoxazole/trimethoprim was identified in 18 of these isolates (94.7%). Among the K. pneumoniae isolates with class 1 integrons, 47% belonged to the KpI phylogenetic group, and one isolate (14.3%) carrying these genetic elements belonged to the KpIII group. Conclusions The wide variety of detected class 1 integrons supports the presence of high rates of antimicrobial resistance, genetic variability, and rapid dissemination of beta-lactamase genes among K. pneumoniae clinical isolates in recent years in hospitals in Recife-PE, Brazil. The findings of this study indicate that the surveillance of K. pneumoniae integrons in clinical isolates could be useful for monitoring the spread of antibiotic resistance genes in the hospital environment.

Colistin and anti-Gram-positive bacterial agents against Acinetobacter baumannii

Introduction Acinetobacter baumannii has attained an alarming level of resistance to antibacterial drugs. Clinicians are now considering the use of older agents or unorthodox combinations of licensed drugs against multidrug-resistant strains to bridge the current treatment gap. We investigated the in vitro activities of combination treatments that included colistin with vancomycin, norvancomycin or linezolid against multidrug-resistant Acinetobacter baumannii. Methods The fractional inhibitory concentration index and time-kill assays were used to explore the combined effects of colistin with vancomycin, norvancomycin or linezolid against 40 clinical isolates of multidrug-resistant Acinetobacter baumannii. Transmission electron microscopy was performed to evaluate the interactions in response to the combination of colistin and vancomycin. Results The minimum inhibitory concentrations (MICs) of vancomycin and norvancomycin for half of the isolates decreased below the susceptibility break point, and the MIC of linezolid for one isolate was decreased to the blood and epithelial lining fluid concentration using the current dosing regimen. When vancomycin or norvancomycin was combined with subinhibitory doses of colistin, the multidrug-resistant Acinetobacter baumannii test samples were eradicated. Transmission electron microscopy revealed that subinhibitory doses of colistin were able to disrupt the outer membrane, facilitating a disruption of the cell wall and leading to cell lysis. Conclusions Subinhibitory doses of colistin significantly enhanced the antibacterial activity of vancomycin, norvancomycin, and linezolid against multidrug-resistant Acinetobacter baumannii.

Impact of insecticide resistance on the field control of Aedes aegypti in the State of São Paulo

IntroductionThe need to control dengue transmission by means of insecticides has led to the development of resistance to most of the products used worldwide against mosquitoes. In the State of São Paulo, the Superintendência de Controle de Endemias(SUCEN) has annually monitored the susceptibility of Aedes aegypti to insecticides since 1996; since 1999, surveys were conducted in collaboration with the National Network of Laboratories (MoReNAa Network) and were coordinated by the Ministry of Health. In this study, in addition to the biological characterization of insecticide resistance in the laboratory, the impact of resistance on field control was evaluated for vector populations that showed resistance in laboratory assays.MethodsField efficacy tests with larvicides and adulticides were performed over a 13-year period, using World Health Organization protocols.ResultsData from the field tests showed a reduction in the residual effect of temephos on populations with a resistance ratio of 3. For adults, field control was less effective in populations characterized as resistant in laboratory qualitative assays, and this was confirmed using qualitative assays and field evaluation.ConclusionsOur results indicated that management of resistance development needs to be adopted when insect populations show reduced susceptibility. The use of insecticides is a self-limiting tool that needs to be applied cautiously, and dengue control requires more sustainable strategies.

Effects of piperonyl butoxide on the toxicity of the organophosphate temephos and the role of esterases in the insecticide resistance of Aedes aegypti

IntroductionThe effects of piperonyl butoxide (PBO) on the toxicity of the organophosphate temephos (TE) and the role of esterases in the resistance of Aedes aegypti to this insecticide were evaluated.MethodsA. aegypti L4 larvae susceptible and resistant to TE were pre-treated with PBO solutions in acetone at concentrations of 0.125, 0.25, 0.5, 1, and 2% for 24h and subsequently exposed to a diagnostic concentration of 0.02mg/L aqueous TE solution. The esterase activity of the larvae extracts pre-treated with varying PBO concentrations and exposed to TE for three time periods was determined.ResultsAt concentrations of 0.25, 0.5, 1, and 2%, PBO showed a significant synergistic effect with TE toxicity. High levels of esterase activity were associated with the survival of A. aegypti L4 larvae exposed to TE only.ConclusionsThe results of the biochemical assays suggest that PBO has a significant inhibitory effect on the total esterase activity in A. aegypti larvae.

Evaluation of constitutive and inducible resistance to clindamycin in clinical samples of Staphylococcus aureus from a tertiary hospital

IntroductionInfections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become common in hospitals and the community environment, and this wide resistance has limited patient treatment. Clindamycin (CL) represents an important alternative therapy for infections caused by S. aureus. Antimicrobial susceptibility testing using standard methods may not detect inducible CL resistance. This study was performed to detect the phenotypes of resistance to macrolides-lincosamides-streptogramin B (MLSB) antibiotics, including CL, in clinical samples of S. aureusfrom patients at a tertiary hospital in Santa Maria, State of Rio Grande do Sul, Brazil.MethodsOne hundred and forty clinical isolates were submitted to the disk diffusion induction test (D-test) with an erythromycin (ER) disk positioned at a distance of 20mm from a CL disk. The results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI).ResultsIn this study, 29 (20.7%) of the 140 S. aureus samples were resistant to methicillin (MRSA), and 111 (79.3%) were susceptible to methicillin (MSSA). The constitutive resistance phenotype (cMLSB) was observed in 20 (14.3%) MRSA samples and in 5 (3.6%) MSSA samples, whereas the inducible resistance phenotype (iMLSB) was observed in 3 (2.1%) MRSA samples and in 8 (5.8%) MSSA samples.ConclusionsThe D-test is essential for detecting the iMLSBphenotype because the early identification of this phenotype allows clinicians to choose an appropriate treatment for patients. Furthermore, this test is simple, easy to perform and inexpensive.

Detection of bla KPC-2 in Proteus mirabilis in Brazil

INTRODUCTION : Infections caused by Klebsiella pneumoniae carbapenemase (KPC)-producing isolates pose a major worldwide public health problem today. METHODS : A carbapenem-resistant Proteus mirabilis clinical isolate was investigated for plasmid profiles and the occurrence of β-lactamase genes. RESULTS : The isolate exhibited resistance to ertapenem and imipenem and was susceptible to meropenem, polymyxin, and tigecycline. Five plasmids were identified in this isolate. DNA sequencing analysis revealed the presence of bla KPC-2 and bla TEM-1 genes. An additional PCR using plasmid DNA confirmed that bla KPC-2 was present in one of these plasmids. Conclusions: We report the detection of bla KPC-2 in P. mirabilis in Brazil for the first time. This finding highlights the continuous transfer of bla KPC between bacterial genera, which presents a serious challenge to the prevention of infection by multidrug-resistant bacteria.

Antimicrobial resistance of Helicobacter pylori strains to five antibiotics, including levofloxacin, in Northwestern Turkey

INTRODUCTION: Antibiotic resistance is the main factor that affects the efficacy of current therapeutic regimens against Helicobacter pylori. This study aimed to determine the rates of resistance to efficacy clarithromycin, amoxicillin, tetracycline, levofloxacin and metronidazole among H. pylori strains isolated from Turkish patients with dyspepsia. METHODS: H. pylori was cultured from corpus and antrum biopsies that were collected from patients with dyspeptic symptoms, and the antimicrobial susceptibility of H. pylori was determined using the E-test (clarithromycin, amoxicillin, tetracycline, metronidazole and levofloxacin) according to the EUCAST breakpoints. Point mutations in the 23S rRNA gene of clarithromycin-resistant strains were investigated using real-time PCR. RESULTS: A total of 98 H. pylori strains were isolated, all of which were susceptible to amoxicillin and tetracycline. Of these strains, 36.7% (36/98) were resistant to clarithromycin, 35.5% (34/98) were resistant to metronidazole, and 29.5% (29/98) were resistant to levofloxacin. Multiple resistance was detected in 19.3% of the isolates. The A2143G and A2144G point mutations in the 23S rRNA-encoding gene were found in all 36 (100%) of the clarithromycin-resistant strains. Additionally, the levofloxacin MIC values increased to 32 mg/L in our H. pylori strains. Finally, among the clarithromycin-resistant strains, 27.2% were resistant to levofloxacin, and 45.4% were resistant to metronidazole. CONCLUSIONS: We conclude that treatment failure after clarithromycin- or levofloxacin-based triple therapy is not surprising and that metronidazole is not a reliable agent for the eradication of H. pylori infection in Turkey.

History of insecticide resistance of Triatominae vectors

AbstractIn the last 15 years, different types of Triatominae resistance to different insecticides have been reported; thus, resistance may be more widespread than known, requiring better characterization and delimitation, which was the aim of this review. This review was structured on a literature search of all articles from 1970 to 2015 in the PubMed database that contained the keywords Insecticide resistance and Triatominae . Out of 295 articles screened by title, 33 texts were selected for detailed analysis. Insecticide resistance of Triatomines is a complex phenomenon that has been primarily reported in Argentina and Bolivia, and is caused by different factors (associated or isolated). Insecticide resistance of Triatominae is a characteristic inherited in an autosomal and semi-dominant manner, and is polygenic, being present in both domestic and sylvatic populations. The toxicological profile observed in eggs cannot be transposed to different stages of evolution. Different toxicological profiles exist at macro- and microgeographical levels. The insecticide phenotype has both reproductive and developmental costs. Different physiological mechanisms are involved in resistance. Studies of Triatomine resistance to insecticides highlight three deficiencies in interpreting the obtained results: I) the vast diversity of methodologies, despite the existence of a single guiding protocol; II) the lack of information on the actual impact of resistance ratios in the field; and III) the concept of the susceptibility reference lineage. Research on the biological and behavioral characteristics of each Triatominae species that has evolved resistance is required in relation to the environmental conditions of each region.

Phenotypic and genotypic profile of pyrethroid resistance in populations of the mosquito Aedes aegypti from Goiânia, Central West Brazil

ABSTRACTINTRODUCTION:The mosquito Aedes aegypti has evolved resistance to pyrethroid insecticides. The present study evaluated Ae. aegypti from Goiânia for the resistant phenotype and for mutations associated with resistance.METHODS:Insecticide dose-response bioassays were conducted on mosquitoes descended from field-collected eggs, and polymerase chain reaction (PCR) was used to genotype 90 individuals at sites implicated in pyrethroid resistance.RESULTS:All mosquito populations displayed high levels of resistance to deltamethrin, as well as high frequencies of the 1016Ile kdr and 1534Cys kdrmutations.CONCLUSIONS:Aedes aegypti populations in the Goiânia area are highly resistant to deltamethrin, presumably due to high frequencies of kdr(knockdown-resistance) mutations.

Antimicrobial resistance profiles and oxacillinase genes in carbapenem-resistant Acinetobacter baumannii isolated from hospitalized patients in Santa Catarina, Brazil

Abstract: INTRODUCTION: Carbapenems are the therapy of choice for treating severe infections caused by the Acinetobacter calcoaceticus-Acinetobacter baumannii complex. We aimed to assess the prevalence and antimicrobial susceptibility profiles of producers of distinct oxacillinases among nosocomial isolates of the A. calcoaceticus-A. baumannii complex in a 249-bed general hospital located in Joinville, Southern Brazil. METHODS: Of the 139 A. baumannii clinical isolates with reduced susceptibility to carbapenems between 2010 and 2013, 118 isolates from varying anatomical sites and hospital sectors were selected for genotypic analysis. Five families of genes encoding oxacillinases, namely blaOXA-23-like, blaOXA-24-like, blaOXA-51-like, blaOXA-58-like, and blaOXA-143-like, wereinvestigated by multiplex polymerase chain reaction (PCR). RESULTS: Most (87.3%) isolates simultaneously carried the blaOXA-23-likeand blaOXA-51-likegenes, whereas three (2.5%) isolates harbored only blaOXA-51-likeones. The circulation of carbapenem-resistant isolates increased during the study period: from none in 2010, to 22 in 2011, 64 in 2012, and 53 in 2013. CONCLUSIONS: Isolates carrying the blaOXA-23-likeand blaOXA-51-likegenes were widely distributed in the hospital investigated. Because of the worsening scenario, the implementation of preventive measures and effective barriers is needed.

New Delhi metallo-beta-lactamase-1-producing Acinetobacter spp. infection: report of a survivor

Abstract: New Delhi metallo-beta-lactamase-1 (NDM-1) is a bacterial enzyme that renders the bacteria resistant to a variety of beta-lactam antibiotics. A 20-year-old man was hospitalized several times for surgical treatment and complications caused by a right-sided vestibular schwannoma. Although the patient acquired several multidrug-resistant infections, this study focuses on the NDM-1-producing Acinetobacter spp. infection. As it was resistant to all antimicrobials tested, the medical team developed a 20-day regimen of 750mg/day metronidazole, 2,000,000IU/day polymyxin B, and 100mg/day tigecycline. The treatment was effective, and the patient recovered and was discharged from the hospital.

Study of in vivo interactions between penicillin-binding proteins of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a major human pathogen that has acquired resistance to practically all classes of β-lactam antibiotics, being responsible of Multidrug resistant S. aureus (MRSA) associated infections both in healthcare (HA-MRSA) and community settings (CA-MRSA). The emergence of laboratory strains with high-resistance (VRSA) to the last resort antibiotic, vancomycin, is a warning of what is to come in clinical strains. Penicillin binding proteins (PBPs) target β-lactams and are responsible for catalyzing the last steps of synthesis of the main component of cell wall, peptidoglycan. As in Escherichia coli, it is suggested that S. aureus uses a multi-protein complex that carries out cell wall synthesis. In the presence of β-lactams, PBP2A and PBP2 perform a joint action to build the cell wall and allow cell survival. Likewise, PBP2 cooperates with PBP4 in cell wall cross-linking. However, an actual interaction between PBP2 and PBP4 and the location of such interaction has not yet been determined. Therefore, investigation of the existence of a PBP2-PBP4 interaction and its location(s) in vivo is of great interest, as it should provide new insights into the function of the cell wall synthesis machinery in S. aureus. The aim of this work was to develop Split-GFPP7 system to determine interactions between PBP2 and PBP4. GFPP7 was split in a strategic site and fused to proteins of interest. When each GFPP7 fragment, fused to proteins, was expressed alone in staphylococcal cells, no fluorescence was detectable. When GFPP7 fragments fused to different peptidoglycan synthesis (PBP2 and PBP4) or cell division (FtsZ and EzrA) proteins were co-expressed together, fluorescent fusions were localized to the septum. However, further analysis revealed that this positive result is mediated by GFPP7 self-association. We then interpret the results in light of such event and provide insights into ways of improving this system.