Emergence of high-level resistance to gentamicin and streptomycin in Streptococcus agalactiae in Buenos Aires, Argentina                                
 

HUGO EDGARDO VILLAR, MÓNICA BEATRIZ JUGO             

Introduction. Streptococcus agalactiae has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Optimal antimicrobial therapy for serious infections requires the use of synergistic combinations of a cell wall-active agent, such as a penicillin, with an aminoglycoside, which results in bactericidal activity against this organism. The synergistic effect is eliminated by the acquisition of high-level resistance (HLR) to aminoglycosides. The aim of our study was to determine the prevalence of HLR to gentamicin (GEN) and streptomycin (EST). The ability to detect HLR using a standard agar screen plate and high-content discs was investigated.
Methods. This study was conducted with 141 strains of S. agalactiae isolated from vaginal and rectal swabs of pregnant women at term. Minimum inhibitory concentrations (MICs) to GEN and STR were determined by the E-test method. Disks of GEN (120 μg) and STR (300 μg) were used to detect HLR. Agar screening plates were performed with GEN 100 mg/L, GEN 500 mg/L and STR 2000 mg/L.
Results. The HLR to GEN and STR was detected in 13.5% and 16.3% of the isolates respectively. Among 141 strains, 7.8% were simultaneously resistant to GEN and STR. With 120-μg GEN and 300-μg STR disks, strains for which MICs were ≥512 mg/L and ≥1024 mg/L had no zones of inhibition. Isolates with inhibitory zones for GEN and STR of ≥13 mm showed a MICs ≤64 mg/L and ≤512 mg/L. All the screening plates were negative for these isolates. HLR to aminoglycosides was associated (83.9%) with resistance to erythromycin and/or clindamycin.
Conclusions. This study highlights the emergence of strains with HLR to aminoglycosides. The disk-agar diffusion test performed with high-content aminoglycoside disks and screening plates can provide laboratories with a convenient and reliable method for detecting S. agalactiae isolates that are resistant to aminoglycoside-betalactam synergy.

Rev Esp Quimioter 2013:26(2):112-115 [pdf]

Detection of antibacterial resistance by MALDI-TOF mass spectrometry                                 
 

YULIYA ZBOROMYRSKA, MARIO FERRER-NAVARRO, FRANCESC MARCO, JORDI VILA               

In the last decade we have witnessed a remarkable increase in the number of strains isolated in hospitals that are producing extended spectrum β-lactamases (ESBL) or, more recently, carbapenemases. This makes clear the need for a system for rapid detection of these resistance mechanisms that allow the selection of the most suitable antibiotic treatment in order to improve patient care. Recent data support the possibility of using mass spectrometry (MS), specifically MALDI-TOF (Matrix-Assisted Laser Desorption / Ionization, Time-of-Flight ) systems to identify specific resistance mechanisms and their use offers several advantages. First, the economic cost of each determination is clearly inferior to the classical molecular techniques for detection of resistance genes. Second, detection of resistance by MALDI-TOF reduces the time for obtaining results compared to the routine methods currently employed. Finally, the possibility that this method allow us to detect enzymes not previously characterized, that there is no information about the genes that encode them. Therefore, we believe that this may be a good tool to implement in clinical microbiology laboratories. This review aims to present the latest developments in this field.

Rev Esp Quimioter 2014:27(2):87-92 [pdf]

Physicians with access to point-of-care tests significantly reduce the antibiotic prescription for common cold                                 
 

C. LLOR, S. HERNÁNDEZ, J. M. COTS, L. BJERRUM, B. GONZÁLEZ, G. GARCÍA, J. D. ALCÁNTARA, G.  GUERRA, M. CID, M. GÓMEZ, J. ORTEGA, C. PÉREZ, J. ARRANZ, M. J. MONEDERO, J. PAREDES, V. PINEDA, GRUPO DE TRABAJO HAPPY AUDIT ESPAÑA               

Objective. This study was aimed at evaluating the effect of two levels of intervention on the antibiotic prescribing in patients with common cold.
Methods. Before and after audit-based study carried out in primary healthcare centres in Spain. General practitioners registered all the episodes of common cold during 15 working days in January and February in 2008 (preintervention). Two types of intervention were considered: full intervention, consisting in individual feedback based on results from the first registry, courses in rational antibiotic prescribing, guidelines, patient information leaflets, workshops on rapid tests –rapid antigen detection and C-reactive protein tests– and provision of these tests in the surgeries; and partial intervention, consisting of all the above intervention except for the workshop and they did not have access to rapid tests. The same registry was repeated in 2009 (postintervention). In addition, new physicians filled out only the registry in 2009 (control group).
Results. 210 physicians underwent the full intervention, 71 the partial intervention and 59 were assigned to the control group. The 340 doctors prescribed antibiotics in 274 episodes of a total of 12,373 cases registered (2.2%).The greatest percentage of antibiotic prescription was found in the control group (4.6%). The partial intervention increased the antibiotic prescription percentage from 1.1% to 2.7% while only doctors who underwent the complete intervention lead to a significant reduction of antibiotics prescribed, from 2.9% before to 0.7% after the intervention (p<0.001).
Conclusion. Only physicians with access to rapid tests significantly reduced antibiotic prescription in patients with common cold.

Rev Esp Quimioter 2013:26(1):12-20 [pdf]

Staphylococcus aureus infections and factors associated with resistance to methicillin in a hospital emergency department 

JUAN GONZÁLEZ-CASTILLO, CATERINA CENCI, ESTHER RODRIGUEZ-ADRADA, FRANCISCO JAVIER CANDEL, FERNANDO DE LA TORRE-MISIEGO, CRISTINA FERNÁNDEZ, FRANCISCO JAVIER MARTÍN-SÁNCHEZ             

Objective. Assessment of the characteristics of patients with Staphylococcus aureus (SA) infections, and factors associated with resistance to methicillin in a hospital emergency department (ED) in Spain.
Materials and Methods. All adult patients admitted between January 2007 and December 2010 with a SA infection confirmed by a positive culture in a sample obtained in the hospital emergency department were selected for enrolment. Epidemiological, clinical, therapeutic and microbiological variables were retrospectively collected from the patients’ medical charts. The variable assessed within the primary outcome of the study was the isolation of methicillin resistant Staphylococcus aureus (MRSA). For the purpose of the analysis, the sample was divided in terms of the presence or not of the resistance to methicillin and a logistic regression analysis was performed to identify the factors associated with isolation and empirical antibiotic coverage of MRSA.
Results. A total of 207 patients with a confirmed SA infection were included in the study analysis, with a mean age of 64.7 (SD 20) years. MRSA was isolated in a total of 63 (30.4%) patients, and a linear incremental trend was observed over the course of the study (p=0,047). MRSA was empirically covered in the emergency department on an average rate of one in three patients. Independent factors associated with the isolation of MRSA were: age above 65 years [OR 2.97 (95% CI 1.24 to 7.1), P = 0.014], severe baseline functional dependence [OR 2.41 (95 % 1.02 to 5.69), P = 0.045], chronic obstructive pulmonary disease [OR 4.83 (95% CI 1.88 to 12.42), P = 0.001], history of antibiotic treatment within the previous 2 months [OR 4.94 (95% CI 2.27 to 10.76), P <0.001] and a confirmed urinary infection [OR 5.98 (95% CI 1.65 to 21.69) p = 0.007]. Independent factors associated with empiric coverage of MRSA in the ED were history of antibiotic treatment within the previous 2 months [OR 3.88 (95% CI 1.76 to 8.57), P <0.001] and the presence of a catheter device [OR 6.28 (95% CI 1.64 to 24.07), P = 0.007].
Conclusions. Resistance to methicillin appears to be increasingly frequent in patients infected with SA admitted in our emergency department and there appears to be a need for a more optimal empiric antibiotic treatment in these patients.

Rev Esp Quimioter 2013:26(4):337-345 [pdf]

Trend in the susceptibility of the most frequent bacterial pathogens isolated at Hospital General La Mancha Centro over 2010-2012 period                                 
 

MARÍA ÁNGELES ASENCIO, MARÍA HUERTAS, RAFAEL CARRANZA, MARÍA FRANCO, JESÚS CASTELLANOS, JOSÉ RAMÓN BARBERÁ, MARÍA DEL CARMEN CONDE, JOSÉ MARÍA TENÍAS              

Introduction. Our objective was to determine the trend of the antimicrobial susceptibility of the most common bacterial
pathogens isolated in La Mancha Centro Hospital (MCH) between 2010-2012.
Material and methods. Isolates of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa from patients admitted to MCH were studied. These data and their antibiotic susceptibility were obtained from the database OBSERVA (BioMérieux).
Results. The percentages of susceptibility for S. aureus were: 50% methicillin-resistant-S. aureus (MRSA) (higher co-resistance to erythromycin and levofloxacin), 46% erythromycin, 73% clindamycin, 45% levofloxacin, 99% rifampin and 100% cotrimoxazole, glycopeptides, linezolid and daptomycin. Increased resistance in ICU was observed (63% MRSA), with 50% of S. aureus (susceptible and methicillin-resistant strains) with vancomycin MIC values ≥ 0.5 mg/L. E. coli susceptibility: 62% amoxicillin-clavulanate, 55% ciprofloxacin, 60% cotrimoxazole, 84% gentamicin and 95% fosfomycin. K. pneumoniae susceptibility: 74% amoxicillin-clavulanate, 71% ciprofloxacin, 78% cotrimoxazole, 94% gentamicin and 87% fosfomycin. The percentage of BLEE strains was 17% and 21% for E. coli and K. pneumoniae, respectively, without detection of resistance to carbapenems. P. aeruginosa susceptibility: 80% ceftazidime and carbapenems, 63% ciprofloxacin and higher than 90% aminoglycosides. A decreasing trend of susceptibility to ceftazidime and carbapenems was observed in ICU and increasing trend to ciprofloxacin.
Conclusions. Resistance percentages were higher in ICU than in the rest of the hospital, highlighting 63% of MRSA strains. Our percentage of BLEE and MRSA strains were higher than the Spanish media. Rifampicin and cotrimoxazole maintain good susceptibility to S. aureus, fosfomycin and aminoglycosides to Enterobacteriaceae and carbapenems to P. aeruginosa.

Rev Esp Quimioter 2014:27(4):261-268 [pdf]