Colonial architecture and growth dynamics of Staphylococcus aureus resistant to methicillin

F. GÓMEZ-AGUDO, M. L. GÓMEZ-LUS, M. T. CORCUERA, L. ALOU, M. J. ALONSO, D. SEVILLANO, D. VAL, A. PALMEIRO, N. IGLESIAS, J. PRIETO

 

The aim of the study was to explore the structure and growth dynamics of Staphylococcus aureus resistant to methicillin (MRSA) colonies using semithin sections visualized by light microscope. One S. aureus susceptible to methicillin (MSSA) and one MRSA clinical strains were studied. Colonies in agar plates were embedded in epoxy resin after each incubation period (24 h and 48 h) at 37ºC. Semithin sections of 0.5µm were stained with toluidine blue and visualized by light microscope. Microscopically, no structural differences were observed between SASM and SARM colonies but differences were observed in both strains between 24 and 48 h incubation periods. Colonies showed two layers clearly differentiated at24 h independently of the resistance to methicillin: (A) one basal layer with high density of population in contact with culture media, and (B) one superficial layer with a lower density of population. Colonies showed four layers at 48 h:(A) one basal layer with high density of population; (B) one clear layer constituted by very degraded bacterial remains in which can be observed cocci dispersed with their dyeing properties; (C) one mixed layer constituted by viable bacteria and little degraded bacterial remains (D) one superficial layer with a lower density of population than basal layer. Colonial architecture is a complex and time-dependent process.

 
Rev Esp Quimioter 2009:22(4):224-227 [pdf]

Influenza surveillance by molecular methods

A. TENORIO, J. M. EIROS, E. RODRÍGUEZ, J. F. BERMEJO, M. DOMÍNGUEZ, T .VEGA, J. CASTRODEZA, R. ORTIZ

 

Introduction: Our objective was to evaluate the application of molecular techniques in the surveillance of influenza, and to describe clinical and epidemiological characteristics of cases diagnosed in 2007-2008 and2008-2009 seasons.

Methods: We analyzed 183 pharyngeal swabs from the same number of patients referred to the virology laboratory of the Sentinel Physician Network of Castilla y Leon, the study of influenza viruses by shell-vial technique and RT-PCR capable of detecting multiple Simultaneously, influenza virus A, B, C, respiratory syncytial virus A, B and adenovirus.

Results: Using cell culture were isolated 17 influenza A viruses and 19 influenza B viruses (19.7% of total). By multiple RT-PCR, was detected 49 influenza A virus, 29 influenza B virus, an influenza virus C, 3 syncytial virus type A and other B and 6 adenoviruses (44.3% of total). All influenza viruses isolated in cell culture was detected by RT-PCR. RT-PCR by 5 co-infections were detected, which represented a 6.25% of co-infections on the whole of positive samples. The average age of patients was 29 years (SD = 21.07). The proportion of women and men accounted for 43.7% and 56.3% respectively. The number of cases diagnosed in relation to age follows a pattern of negative linear correlation.

Conclusions: RT-PCR is revealed as an useful tool for epidemiological surveillance of influenza, allowing also to detect viral subtypes along with other viruses involved in respiratory infections.

Rev Esp Quimioter 2009:22(4):214-220 [pdf]  

Evaluation of three Immunochromatographic Assays for Detection of Legionella pneumophila serogroup 1 Antigen in Urine Samples

M. J. MUÑOZ, M.C. MARTÍNEZ, G. YAGÜE, M. SEGOVIA

 

The Uni-Gold, the SAS and the Binax NOW immunochromatographic test (ICT) urinary antigen assays for the qualitative detection of Legionella pneumophila serogroup 1 were compared using 39 unfrozen and nonconcentrated urine samples from patients with Legionnaires´disease (LD). The Uni-Gold anti-gen test detected the urinary antigen in 41% (16/39), the SAS antigen test in 61.5% (24/39), and the Binax NOW antigen test in 74.3% (29/39). The Binax NOW ICT assay showed the best results when detecting L. pneumophila urinary antigen.

Rev Esp Quimioter 2009:22(4):207-209 [pdf]

Vaccination and postexposure prophylaxis in heath-care workers      

M. N. GUTIÉRREZ, M. C. SÁENZ  

 

Health-care workers are an important professional group exposed to biological risks during their professional activity. The legal regulation of the occupational exposure, as well as the knowledge of occupational diseases, has facilitated the development of prevention measures for this group. Nowadays, vaccination against a number of infectious diseases is considered the most effective strategy of primary prevention. The recommended vaccines include those, according to age, included on adult immunization schedule, and vaccines against infectious diseases that can constitute a major risk, both for the professional and for the patient: chicken pox, rubella, HBV,.On the other hand, the occupational exposure to blood or other body fluids (transmission of HIV, HCV and HBV) is the main risk for health-care workers. Nevertheless, at this moment there is no effective immunoprophylaxis against any disease of this group, excepting HBV infection. Thus, occupational exposure prevention, chemoprophylaxis with anti-retroviral drugs when available, and exposure follow-up are the main strategies to decrease transmission risk.

Rev Esp Quimioter 2009:22(4):190-200 [pdf] 

Glycopeptide heteroresistance and tolerance in hospital grampositive isolates: “invisible” phenomena to the clinician with clinical implications?

L. AGUILAR, M. J. GIMÉNEZ, J. BARBERÁN  

  

This article reviews the concepts of heteroresistance and tolerance to glycopeptides in gram-positive bacteria isolated from hospitalised patients. Heteroresistance (resistant subpopulations among the total bacterial population of the strain, that can be selected by the treatment) and tolerance (capability of survival, but not growth, in the presence of usually lethal antibiotic concentrations) have in common several characteristics: 1) the absence of its determination in laboratory daily practice, 2) they implied a decrease in antimicrobial activity not reflected in MIC values (thus being “invisible” to clinicians in daily routine laboratory reports), 3) the decrease in antimicrobial activity may have clinical implications and 4) they affect a wide spectrum of gram positive bacteria in the hospital (Staphylococcus aureus, coagulase-negative staphylococci, enterococci and different estreptococcal species). The decrease produced in the bactericidal activity (that is critical for the treatment of bacteremias, endocarditis, meningitis and infections in immunocompromised patients) has clinical implications such as persistance of bacteremia, refractory bacteremia, relapse of infections and increased length of stay. Two strategies are possible to overcome tolerance and heteroresistance: addition of antibiotics to obtain bactericidal activity by synergism (key factor for which it should be taken into account antagonic combinations or high resistance to aminoglycosides when choosing the antibiotic regimen),or the use of bactericidal compounds to which gram-positive bacteria show susceptibility and absence of heteroresistance and tolerance (in contrast to glycopeptides), as is the case of lipopeptide daptomycin.

Rev Esp Quimioter 2009;22(4):173-179 [pdf]