Rev Esp Quimioter 2010:23(2):72-75

Cefditoren versus ceftazidime in inducer-substrate combinations for the evaluation of AmpC production in a disc approximation test

F. CAFINI, L. AGUILAR, L. ALOU, M. J. GIMÉNEZ, D. SEVILLANO, M. TORRICO, N. GONZÁLEZ, P. CORONEL, J. PRIETO 

 

Objective: To evaluate cefditoren in inducer-substrate combinations to screen for AmpC induction.
Methods: 100 clinical isolates (25 P. aeruginosa, 25 E. cloacae, 14 M. morganii, 13 S. marcescens, 12 C. freundii, 7 P. rettgeri, and 4 E. aerogenes) were tested by the Kirby-Bauer disc approximation method using cefditoren and ceftazidime discs as substrates, and cefditoren and imipenem discs as inducers.
Results: None of the strains showed induction of AmpC with cefditoren-ceftazidime as inducer-substrate combination. Imipenem-cefditoren as inducer-substrate combination was not useful for evaluating strains of P. aeruginosa since no inhibition zones surrounding the cefditoren disc were found. Among evaluable enterobacteria (those showing substrate inhibition zone), inducible Amp C was detected in 48 out of 63 (76.2%) with cefditoren, and in 33 out of 68 (48.5%) isolates with ceftazidime as substrate. Significantly (p= 0.013) higher number of AmpC producers were detected with cefditoren versus ceftazidime (76.2% vs. 48.5%), due to the differences found for E. cloacae (72.8% vs. 21.7%; p= 0.0009) and S. marcescens (100% vs. 54.5%; p= 0.03). Higher mean reductions of diameters around substrate discs were found for cefditoren (4.17 mm) vs. ceftazidime (3.79 mm), reaching statistical significance (p<0.05) for indol-positive proteae: M. morganii (5.32 mm vs. 3.92 mm) and P. rettgeri (3.47 mm vs. 2.64 mm).
Conclusion: Cefditoren showed no induction capability, and when used as substrate (with imipenem as inducer) it offered detection rates of AmpC inducible enterobacteria higher than the imipenem-ceftazidime combination, mainly for Enterobacter spp. and Serratia spp., with higher diameter reductions for indol-positive proteae.

 
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Rev Esp Quimioter 2010:23(4):190-195

Significance of lower respiratory tract cultures yielding  Aspergillus spp. growth in a hospital without  transplant patients   

P. LUCENA, J. BARBERÁN, G. EROLES, J. J. GRANIZO, M. J. GIMÉNEZ, N. MIR, L. AGUILAR, J. PRIETO   

 

Introduction: Isolation of Aspergillus spp. in non-neutropenic, non-transplant patients with chronic obstructive pulmonary disease (COPD) usually treated with corticosteroids is not easily interpretable. A retrospective review of clinical records corresponding to cultures (respiratory samples) yielding Aspergillusspp. in non- transplant patients was carried out.

Methods: Patients were assigned to four categories: colonization, possible, probable or definitive aspergillosis. A logistic regression model (step–wise procedure) was performed using as dependent variable mortality, and as independent variables those showing differences (p≤0.1) in the bivariant analysis.

Results:Sixty-nine patients were identified. Most were elderly (68.1% ≥65 years), male (73.9%), presented comorbidities(84.1% Charlson index ≥3), COPD (76.8%), were receiving high corticosteroid doses (66.7%), and had previously received antibiotics (94.2%). Forty-five cases were colonizations, 4 possible, 15 probable and 5 definitive aspergillosis. A. fumigatus was isolated in 75.4% patients:  66.7% colonized, 75% possible,93.3% probable and 100% definitive aspergillosis. Colonized patients were older (71.9 ± 11.9 vs. 65.1 ± 9.2 years; p= 0.018) and presented higher (p=0.034) comorbidity index than patients with aspergillosis. Mortality was 31.1% in colonized vs. 62.5% in aspergillosis (p=0.012).

Conclusion: The isolation of A. fumigatus was associated with an increased probability of aspergillosis, with statistical association in the multivariate analysis between mortality and variables related to chemotherapy (no antifungal treatment), disease (diagnostic category) and immunity (leukocytosis).    

 
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Rev Esp Quimioter 2010:23(2):76-80

Variability in the sensitivity to tigecycline against Acinetobacter baumannii in different culture medium

A. TENORIO-ABREU, J. M. EIROS, E. RODRÍGUEZ-MOLINS, D. ANDALUZ, F. BOBILLO, M. DOMÍNGUEZ-GIL, R. ORTIZ DE LEJARAZU 

 

Introduction. The tigecycline may represent a therapeutic alternative for the control of multiresistant A. baumannii, although there is no consensus regarding the cutoff points for sensitivity or variability of MIC as a function of culture medium used for the antibiogram against this microorganism. Therefore, our objective was to verify this variability, and propose the culture medium that comes closest to the standard method.
Methods. We selected 41 strains of carbapenem-resistant A. baumannii. We analyzed the sensitivity to tigecycline in different culture medium: Mueller Hinton agar Oxoid commercial (C-MH), Mueller Hinton fresh agar BD and Co., USA (F-MH) and ISO-sensitest fresh agar Oxoid, using the E-test and disk. The MICs were compared against those obtained using the technique standard of macrodilution.
Results. The mean MIC and inhibition diameters obtained in the different culture medium corresponded to 9.26 mg/L and 15.1 mm in diameter for MH-C, 1.71 mg/L and 22.7 mm for MH-F; 2.68 mg/L and 20.8 mm for ISO-sensitest. Half the MIC obtained by the standard method of dilution was 0.47 mg/L (SD = 0.21), with values between 0.25 and 1 mg/L.
Conclusion. In the three growth media studied, MICs superior to the standard are observed, which is false to interpret resistance in many cases. However, the medium that comes closer more that of reference is the MH-F.

 
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Rev Esp Quimioter 2010:23(4):196-200

Antibiotic susceptibility of Corynebacterium macginleyi strains causing conjunctivitis   

M. ESPÍNOLA, Á. SOMODEVILLA, D. DOMINGO, T. ALARCÓN, M. LÓPEZ-BREA    

 

Introduction. Lipophilic corynebacteria are part of the saprophytic skin flora and they rarely cause infection. C.macginleyi is an exception since it has been involved in conjunctivitis and other ocular surface affections.

Material and methods. Thirty three C. macginleyi strainswere obtained from conjunctival swabs from patients with conjunctivitis symptoms. The minimum inhibitoryconcentration (MIC) for 7 antibiotics (penicillin, gentamycin,ciprofloxacin, tetracycline, vancomycin, rifampicin and linezolid) was tested by broth microdilution method.

Results. One strain was resistant to ciprofloxacin (MIC=16 mg/L) and two were resistant to tetracycline (MIC= 64 y 16mg/L). The rest of the strains were susceptible to all the antibiotics tested.

Conclusions. At the moment, C. macginleyi does not present a major problem due to the low resistance rates shown in the present and other studies. However, epidemiological surveillance of its susceptibility pattern is needed as well as an appropriate use of topical antibiotics in order to achieve a good infection control.    

 
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Rev Esp Quimioter 2010:23(2):81-86

Activity of daptomycin, ciprofloxacin, clindamycin and cotrimoxazole against coagulase-negative Staphylococcus strains with diminished susceptibility to vancomycin

M. FAJARDO, R. HIDALGO, S. RODRÍGUEZ, E. GARDUNO, F. F. RODRÍGUEZ, M. ROBLES 

 

Introduction. Coagulase Negative Staphylococci (CNS) have become one of the most common nosocomial pathogens and it has a high mortality rate due to the increased of seriously ill patients survival, long states immunosuppression and presence of foreign bodies, such as catheters, prostheses, pacemakers, etc. In addition, there is a significant increase in resistance to antimicrobial drugs, especially beta-lactams, and the increase in the MIC for vancomycin leads to a loss of clinical efficacy. This necessitates the search for new therapeutic alternatives, such as daptomycin. The aim of this paper is to study the activity of daptomycin, ciprofloxacin, clindamycin and cotrimoxazole in two groups of clinically significant CNS. a MIC90 with vancomycin ≤ 1 mg/L and the other with MIC90 2 mg/L.
Methods. We identified and studied MIC90 to ciprofloxacin, clindamycin and cotrimoxazole from 54 strains of clinically significant by the CNS Combo 22 Microscan panels (Dade Behring, Siemens). The MIC90 for daptomycin was performed using Etest (AB BioMérieux, Solna, Sweden) on Mueller Hinton plates (BioMérieux, France).

Results. In Group I (vancomycin MIC90 ≤ 1 mg/L) were 19 strains whereas in Group II (vancomycin MIC90 = 2 mg/L) were 35 strains. Expressed in mg/L, MIC90 ranges for daptomycin were 0.047-0.5 in Group I and 0.064-0.5 in Group II. For ciprofloxacin were 8 sensitive strains and 11 resistant in Group I and 10 sensitive and 25 resistant in Group II. For clindamycin were 7 sensitive strains and 12 resistant in Group I and 16 sensitive and 19 resistant in Group II. Finally, for cotrimoxazole were 10 sensitive strains and 9 resistant in Group I and 19 sensitive and 16 resistant in Group II.
Conclusions. The MIC levels to daptomycin were not influenced by the increase in the MIC for vancomycin. There was no statistically significant difference for the sensitivity of ciprofloxacin between the two groups of vancomycin. Regardless of vancomycin, there were a clear relationship between the sensitivity of ciprofloxacin with clindamycin and cotrimoxazole.

 
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Rev Esp Quimioter 2010:23(4):201-205

Impact of the consumption of ophthalmic topical antibiotics   

S. GARCÍA, P. MORI, A. LÓPEZ, L. ALOU, D. MARTINEZ, C. RAMOS, M. L. GÓMEZ-LUS    

 

Introduction. The aim of the study was to value the impact of the consumption of the topical antibiotics used in ophthalmology and to lay the foundations for their prudent use.

Material and methods. A descriptive study about antibiotic use in Spain between 1st January 2004 and 31th December 2008 was carried out. Drugs used in the study had to follow the next criteria: topical administration and ophthalmic antibiotics only or in association. Data of the number of vials and nosocomial consumption were provided by Intercontinental Marketing Services (IMS) and  Health National System, respectively.

Results. Nosocomial and community ophthalmologic antiinfectives in 2008 mean a cost of 4.9 and 24.4 millions of euros, respectively increasing a 5.5% respect to the previous year. Six millions of vials were used, 65% were antibiotics alone and 35% antibiotics in association. The most used ophthalmic antibiotics in monoterapy were the aminoglycosides(tobramycin and gentamicin), followed by the quinolones while the most used ophthalmic antibiotic in association were gramicidine plus neomycine plus polimixin B.

Conclusions.The ophthalmic antiinfectives market, alone and in association, used in the nosocomial and community context means 30 millions of euros and shows an increase about 6%. Strict measures in the antibiotic use are not taken incount in the context of the ophthalmic topical antibiotics.    

 
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Rev Esp Quimioter 2010:23(2):87-92

Comparative study of the susceptibility to daptomycin and other antimicrobials against Staphylococcus spp. resistant to methicillin and Enterococcus spp. using Wider, E-test, and microdilution methods

J. L. GÓMEZ-GARCÉS, F. LÓPEZ-FABAL, A. BURILLO, Y. GIL 

 

The human and material costs of inappropriate antimicrobial therapy are high. This study was designed to search for a rapid, simple and effective antimicrobial susceptibility test capable of identifying the best treatment strategy against microorganisms causing hospital infections showing resistance or reduced susceptibility to the more traditional antibiotics. The tests compared were the E-test, an automated test (Wider) and broth microdilution (as the reference test), to determine the susceptibility to vancomycin, teicoplanin, linezolid and daptomycin of clinical isolates of methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant coagulase negative Staphylococcus spp. and Enterococccus spp. The E-test and Wider methods showed good agreement with the reference method indicating their reliability for routine susceptibility testing of staphylococci and enterococci against vancomycin, teicoplanin, linezolid and daptomycin. Notwithstanding, when faced with a serious enterococcal infection, the MIC of daptomycin should be more accurately determined using a reference technique such as broth microdilution.

 

 
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Rev Esp Quimioter 2010:23(4):206-209

Rapid identification of Mycobacterium tuberculosis complex from broth cultures by immunochromatographic assay   

P. GARCÍA-MARTOS, L. GARCÍA-AGUDO, M. J. RODRÍGUEZ-JIMÉNEZ, M. RODRÍGUEZ-IGLESIAS    

 

Background: Recently, a simple and rapid commercial assay (BD MGIT TBc ID) has been developed using a monoclonal antibody anti-MPT64 for the differentiation of Mycobacterium tuberculosis complex from other mycobacteria by immunochromatography.

Methods: We evaluate in this work the clinical usefulness of the test for the identification of 51 strains of M. tuberculosis complex and 24 strains of other mycobacteria belonging to 14 different species, compared with the method of hybridization with DNA probes.

Results: Immunochromatographic method performance was excellent, with sensitivity, specificity, positive and negative predictive values of 98, 100, 96.1, and 98.7%, respectively.

Conclusions: These results indicate that immunochromatographic assay can be safely used for rapid identification of M. tuberculosis complex in combination with culture in liquid media. The test is extremely simple, provides results in just 15 minutes, requires no complex equipment or specialized personnel and may be a good alternative to molecular methods, especially in small laboratories.    

 
Rev Esp Quimioter 2010:23(4):206-209 [pdf]

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