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Introduction: Monoclonal antibodies targeting the epidermal growth factor receptor (EGFR) have shown clinical benefit in advanced stages of head and neck carcinoma; however, despite encouraging initial results, clinical studies show that there are patients who present rates very poor or null response with its use. Method: A review of the scientific literature was carried out in the specialized sources Medline, Cochrane Library and academic Google on the molecular mechanisms of resistance that may be involved in reducing the efficacy of the monoclonal antibodies cetuximab and nimotuzumab. Results: In the case of cetuximab, the mechanisms of intrinsic and acquired resistance are exposed, such as: the presence of the EGFR-K521 and AURKA Phe31-Ile polymorphisms, the hot spots activating PIK3CA and KRAS/HRAS mutations, the loss of PTEN protein expression, mutations in the extracellular domain of EGFR, overexpression of MET and induction of epithelial–mesenchymal transition, as well as some mechanisms involving the AKT/PI3K, RAS/ RAF/MEK/ERK and JAK/STAT pathways. About nimotuzumab, the literature refers that the best clinical results with its use have been associated with EGFR overexpression. Conclusions: The greatest challenges in head and neck carcinoma are understanding resistance to these therapies and identifying predictive biomarkers of response for proper patient selection. Although there are multiple proposals for biomarkers that are published, they require their validation in prospective clinical trials for their introduction into routine clinical practice. The need to increase studies on the mechanisms of resistance to nimotuzumab is suggested. [ABSTRACT FROM AUTHOR]

Candida albicans is a commensal yeast capable of causing an opportunistic infection called candidiasis in susceptible hosts. Treatment to combat Candida may be topical or systemic according to the type of infection and the imidazole derivatives (fluconazole, itraconazole, ketoconazole, miconazole, etc.) are the antifungals most widely used. However, resistance to these drugs is observed by a decrement in their effectiveness. This is mainly due to the emergence of resistant yeasts and of new pathogenic species, as well as to the irrational prescribing of antifungal prophylaxis and the use of higher therapeutic doses. There are two mechanisms by which Candida can acquire an azole resistance, the first is by molecular mutations of antifungal target enzyme, as the alteration of enzymes related to the synthesis of ergosterols and the second by change in the efflux pumps, such as those of ATP-binding cassette and the higher facilitators. In this work the main mechanisms of resistance to Candida and the importance of performing susceptibility tests in order to provide an adequate treatment for this type of opportunistic infections are summarized. [ABSTRACT FROM AUTHOR]

Rhipicephalus (Boophilus) microplus is an endemic cattle pest in tropical and subtropical regions of the world, causing major economic losses to cattle producers. Chemical acaricides have played a pivotal role in the control of R. (B.) microplus; however, as a consequence of extensive use of acaricides, this tick specie has developed resistance to all major classes of acaricides worldwide. Resistant to organophosphates, synthetic pyrethroids and amitraz has been reported mainly in Australia and Latinoamerica. The acaricide resistance in ticks is conferred primarily by two major physiological mechanisms: target site insensitivity and metabolic detoxification. Alone and or in combination these mechanisms confer resistance to all of the available classes of acaricides. In the present review we present the current status of R. (B.) microplus resistant to acaricides worldwide (with emphasis in Mexico) and the most important mechanisms involved in this phenomenon. [ABSTRACT FROM AUTHOR]

Introduction: Microbial resistance to antibiotics is a growing problem in hospitals, in recent years the number of multiresistant bacteria has increased at an alarming rate despite the existence of various groups of broad-spectrum antimicrobial drugs and strains have been reported resistant to all currently available antibacterials Objective: To identify the profiles of antimicrobial resistance in blood culture reports from the Central Military Hospital during 2009. Material and methods. We collected copies of the reports of all blood cultures and antibiograms were performed on patients hospitalized in 2009, were captured in spreadsheet and susceptibility data were analyzed using measures of central tendency to identify the microorganisms most frequently developed and Profiles antimicrobial resistance. Results. We analyzed a total of 376 reports of blood cultures, in which the three predominant organisms were Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. 32% of gramnegative express broadpectrum beta lactamases, and 71% of gram-positive beta-lactamase expressed. More than 60% are multidrug-resistant gramegative organisms. But even though most of the isolates were multiresistant, still retain a high percentage of sensitivity to drugs such as cefotetan, aminoglycosides, rifampicin and chloramphenicol. [ABSTRACT FROM AUTHOR]

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