Yeast Bloodstream Infections in the COVID-19 Patient: A Multicenter Italian Study (FiCoV Study).

Fungemia is a co-infection contributing to the worsening of the critically ill COVID-19 patient. The multicenter Italian observational study FiCoV aims to estimate the frequency of yeast bloodstream infections (BSIs), to describe the factors associated with yeast BSIs in COVID-19 patients hospitalized in 10 hospitals, and to analyze the antifungal susceptibility profiles of the yeasts isolated from blood cultures. The study included all hospitalized adult COVID-19 patients with a yeast BSI; anonymous data was collected from each patient and data about antifungal susceptibility was collected. Yeast BSI occurred in 1.06% of patients, from 0.14% to 3.39% among the 10 participating centers. Patients were mainly admitted to intensive or sub-intensive care units (68.6%), over 60 years of age (73%), with a mean and median time from the hospitalization to fungemia of 29 and 22 days, respectively. Regarding risk factors for fungemia, most patients received corticosteroid therapy during hospitalization (61.8%) and had a comorbidity (25.3% diabetes, 11.5% chronic respiratory disorder, 9.5% cancer, 6% haematological malignancies, 1.4% organ transplantation). Antifungal therapy was administered to 75.6% of patients, mostly echinocandins (64.5%). The fatality rate observed in COVID-19 patients with yeast BSI was significantly higher than that of COVID-19 patients without yeast BSI (45.5% versus 30.5%). Candida parapsilosis (49.8%) and C. albicans (35.2%) were the most fungal species isolated; 72% of C. parapsilosis strains were fluconazole-resistant (range 0-93.2% among the centers). The FiCoV study highlights a high prevalence of Candida BSIs in critically ill COVID-19 patients, especially hospitalized in an intensive care unit, a high fatality rate associated with the fungal co-infection, and the worrying spread of azole-resistant C. parapsilosis.

Modeling the surface topography dependence of friction, adhesion, and contact compliance.

The small-scale topography of surfaces critically affects the contact area of solids and thus the forces acting between them. Although this has long been known, only recent advances made it possible to reliably model interfacial forces and related quantities for surfaces with multiscale roughness. This article sketches both recent and traditional approaches to their mechanics, while addressing the relevance of nonlinearity and nonlocality arising in soft- and hard-matter contacts.

Simple yet effective methods to probe hydrogel stiffness for mechanobiology.

In spite of tremendous advances made in the comprehension of mechanotransduction, implementation of mechanobiology assays remains challenging for the broad community of cell biologists. Hydrogel substrates with tunable stiffness are essential tool in mechanobiology, allowing to investigate the effects of mechanical signals on cell behavior. A bottleneck that slows down the popularization of hydrogel formulations for mechanobiology is the assessment of their stiffness, typically requiring expensive and sophisticated methodologies in the domain of material science. Here we overcome such barriers offering the reader protocols to set-up and interpret two straightforward, low cost and high-throughput tools to measure hydrogel stiffness: static macroindentation and micropipette aspiration. We advanced on how to build up these tools and on the underlying theoretical modeling. Specifically, we validated our tools by comparing them with leading techniques used for measuring hydrogel stiffness (atomic force microscopy, uniaxial compression and rheometric analysis) with consistent results on PAA hydrogels or their modification. In so doing, we also took advantage of YAP/TAZ nuclear localization as biologically validated and sensitive readers of mechanosensing, all in all presenting a suite of biologically and theoretically proven protocols to be implemented in most biological laboratories to approach mechanobiology.

Incontinencia pigmenti / Pigment incontinence

La incontinencia pigmenti es una genodermatosis poco frecuente, de herencia dominante ligada al X, que se caracteriza por la presencia de lesiones cutáneas típicas que pueden asociarse con afectación de otros tejidos derivados del neuroectodermo. Es una enfermedad potencialmente grave, que requiere un diagnóstico precoz y un seguimiento multidisciplinario de por vida.Se presenta el caso de un paciente de sexo femenino de 6 días de vida con diagnóstico clínico y anatomopatológico de incontinencia pigmenti

Incontinentiapigmenti is a rare, X-linked dominantgenodermatosis, characterized by the presence of typical skin lesions that may be associated with involvement of other tissues derived from neuroectoderm. It is a potentially serious disease that requires early diagnosis and a multidisciplinary life-long follow up.Wereport the case of a 6 day old femalewith a clinical and anatomopathological diagnosis of incontinenciapigmenti.

Liquen escleroso extragenital: Presentación de un caso / Lichen scleros extragenital: presentation of a case

El liquen escleroso es una enfermedad crónica inflamatoria de causa desconocida. En hombres su presentación es infrecuente y se observa más comúnmente en la cuarta década de la vida. Asimismo, las lesiones extragenitales son inusuales y asientan más comúnmente en extremidades y tronco. A continuación, presentamos un paciente de sexo masculino adolescente con diagnóstico de liquen escleroso en dorso

Lichen sclerosus is a chronic inflammatory disease of unknown etiology. Appearance in men is unusual and is most seen at fourth decade of life. Also extragenital lesions are rare and most commonly settle in extremities and trunk. A case of a male adolescent patient with lichen sclerosus in trunk is reported.

Dermatitis herpetiforme y enfermedad celíaca / Dermatitis herpetiformis and celiac disease

La dermatitis herpetiforme (DH) es una enfermedad crónica y ampollar caracterizada por la presencia de lesiones intensamente pruriginosas, de ubicación característica, y por asociarse en todos los casos a enfermedad celíaca (EC) (sintomática o no). Ambas entidades se consideran una expresión, en diferentes órganos, de hipersensibilidad al gluten. Se presenta una serie de cuatro pacientes de sexo femenino, con un promedio de 46 años, que consultaron por la aparición de pápulas, lesiones erosivocostrosas, excoriaciones y ampollas, pruriginosas, localizadas predominantemente en los codos, las rodillas y el dorso superior. Referían brotes intermitentes con un tiempo de evolución de entre 6 meses y 10 años. Se realizó una biopsia cutánea y estudio histopatológico que evidenció la presencia de una dermatosis ampollar subepidérmica con neutrófilos e IFD positiva en tres de las pacientes, y que confirmó el diagnóstico de dermatitis herpetiforme. Los hallazgos de laboratorio y la videoendoscopia digestiva alta con toma de biopsia fueron compatibles, en todos los casos, con enfermedad celíaca. Se les indicó dieta libre de gluten (DLG) a todas las pacientes; en una de ellas fue suficiente para lograr la remisión completa de las lesiones después de 3 meses; las tres restantes requirieron tratamiento con dapsona para controlar la enfermedad (AU)

Dermatitis herpetiformis (DH) is a chronic, bullous disease, which is characterized by intensely pruritic lesions, property location and diagnosis in all cases of celiac disease (CD) (symptomatic or not). Both entities are considered expression in different organs of hypersensitivity to gluten. A series of four female patients is presented with an average of 46 years who consulted by the appearance of papules, erosivocostrosas injuries, abrasions and blisters, itchy, localized predominantly on elbows, knees and upper back. Intermittent outbreaks concerned with evolution time between 6 months and 10 years. IFD positive skin biopsy and histopathological study showed subepidermal bullous dermatosis with neutrophils was performed, and in three of the patients confirmed the diagnosis of dermatitis herpetiformis. Laboratory findings and upper gastrointestinal video endoscopy with biopsy were compatible in every case with celiac disease. Gluten-free diet in all patients indicated, one of them was enough to achieve complete remission of lesions after three months; the remaining three required starting dapsone for disease control (AU)

Leishmaniasis cutánea: presentación inusual en placa verrucosa / Cutaneous leishmaniasis: inusual verrucous plaque presentation

La leishmaniasis es una enfermedad zoonótica de distribución mundial que puede presentarmúltiples manifestaciones clínicas. Se presenta el caso de un paciente con leishmaniasiscutánea en placa verrucosa de 8 años de evolución confirmada por PCR ycon buena respuesta al tratamiento con antimoniato de meglumina. La leishmaniasiscutánea verrucosa es una variante clínica infrecuente, de evolución crónica y difícil diagnóstico...

Queilitis granulomatosa de Miescher / Granulomatous Miescher cheilitis

La queilitis granulomatosa de Miescher es la forma monosintomática más frecuente del síndrome de Melkersson-Rosenthal, cuya tríada clásica se completa con la presencia de parálisis facial y lengua fisurada. Es una entidad de causa desconocida, curso crónico eincierto y difícil tratamiento, que muchas veces requiere múltiples modalidades terapéuticas y seguimiento a largo plazo.Se presenta el caso de una paciente con edema labial permanente que evoluciona con múltiples brotes recurrentes...

Crioglobulinemia tipo I asociada a mieloma múltiple en un paciente con hapatits C / Type I cryoglobulinemia associated with multiple myeloma in a patient with hepatitis C

La presencia de crioglobulinas asociadas a manifestaciones clínicas sistémicas constituyen el síndrome crioglobulinémico. Se describen tres subtipos de esta entidad con características serológicas, clínicas e histológicas distintivas. En todos los casos, el órgano más afectadoes la piel. La sospecha clínica y el abordaje multidisciplinario son fundamentales para arribar al diagnóstico correcto e iniciar el tratamiento correspondiente.A continuación se presenta un caso de crioglobulinemia tipo I asociada a mieloma múltiple de reciente diagnóstico en un paciente con antecedente de hepatitis C que presentó un extenso compromiso cutáneo...

Hemiatrofia facial progresiva y morfea en golpe de sable: ¿entidades diferentes o un espectro de la misma enfermedad? / Progressive facial hemiatrophy and morphea en coup de sabre: different entities or a spectrum of the same disease?

La hemiatrofia facial progresiva (HFP) o síndrome de Parry-Romberg se caracteriza por lapresencia de lesiones atróficas que comprometen unilateralmente la piel de la cara. Lamorfea en golpe de sable (MGS) es un subtipo de esclerodermia localizada de disposición lineal en cara o cuero cabelludo. Ambas comparten múltiples características, por lo que diferenciarlas suele ser un gran desafío. Existen controversias acerca de si son procesosindependientes o un espectro de una misma enfermedad. Objetivos. Describir las características clínicas, hallazgos histológicos y de laboratorio delos pacientes con diagnóstico de HFP, MGS o ambas entidades evaluados en nuestro servicio. Comparar ambas patologías y revisar la bibliografía publicada para intentar esclarecersi son entidades independientes o un espectro de la misma enfermedad.Material y métodos. Se realizó un estudio retrospectivo y descriptivo. Se incluyerontodos los pacientes con diagnóstico de HFP, MGS o ambas entidades evaluados desde enero de 2002 hasta julio de 2014. Resultados.Se encontraron 83 pacientes con esclerodermia localizada. Se seleccionaron 12 pacientes: 4 con MGS, 4 con HFP y 4 con ambas entidades. Se observó la coexistenciacon morfea en área extracefálica en un 25%, sin predominio por ningún grupo. En relación con las manifestaciones extracutáneas, el 41,66% presentó alteraciones oftalmológicas y/o otorrinolaringológicas, principalmente en el grupo con HFP o ambas patologías.Ningún paciente presentó alteraciones neurológicas. Sólo 2 pacientes, una con diagnóstico de HFP y otra con HFP + MGS, presentaron FAN reactivo. Todos los pacientes presentaron estudio histopatológico compatible. Se pudieron revisar 6/12 biopsias cutáneas. Los principales hallazgos histopatológicos independientemente del diagnóstico clínico fueron: esclerosis con hialinización del colágeno e infiltrado inflamatorio mononuclear. Conclusion. Los hallazgos del presente estudio respecto de la clínica, la histología...

Dynamic QuantiFERON Response in Psoriasis Patients Taking Long-Term Biologic Therapy.

INTRODUCTION: The risk of active tuberculosis is increased in psoriasis patients receiving biologic drug therapy. The QuantiFERON-TB Gold In-Tube assay (QFT) is used for latent tuberculosis screening in these patients. This study presents a retrospective analysis on repeated QFT assays, investigating the influence of biologic drugs and isoniazid therapy on the outcome of the assay. METHODS: Serial QFTs of 58 psoriasis patients, who received biologic drug therapy, were evaluated at baseline and after 12 months of treatment. Patients were retrospectively divided in four groups according to QFT results at baseline and at follow-up: patients having a QFT reversion (from positive to negative results); patients with a conversion (from negative to positive); patients confirming the baseline results, either positive or negative. RESULTS: At the end of the 12-months period, 11.1% of patients with a negative QFT result at baseline presented a conversion, showing low interferon (IFN)-gamma values, whereas 6.9% of positive patients presented a QFT reversion. When the test was repeated after 2-3 months without isoniazid chemoprophylaxis, patients with QFT conversion showed negative results. No patient developed active tuberculosis. CONCLUSIONS: In patients undergoing biologic therapy, a positive QFT assay needs to be further confirmed, as false-positive results may occur after long-term therapy. Repeating QFT tests in patients with low IFN-gamma values could reduce the incidence of false-positive latent tuberculosis infection diagnosis, thus preventing unnecessary tuberculosis chemoprophylaxis. In conclusion, a dynamic QFT response is possible in psoriasis patients undergoing biologic therapy.

Macrolide resistance and in vitro selection of resistance to antibiotics in Lactobacillus isolates.

Spreading of resistance to antibiotics is of great concern due to the increasing rate of isolation of multiresistant pathogens. Since commensal bacteria may transfer determinants of resistance to pathogens, studies on development of resistance should include also lactobacilli. Resistance to macrolides, penicillins and tetracycline was determined in 40 isolates of Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus crispatus, and Lactobacillus casei isolated from faeces of apparently healthy volunteers. Frequency of mutation and changes in susceptibility after serial exposure to these antibiotics at concentrations of 4× and 8× MIC were evaluated in susceptible isolates. Acquired resistance was defined as an increment in MIC values of at least four times in respect to the pre-selection values. Resistance to macrolides and/or tetracycline was identified in 14 and 4 isolates, respectively. ermB gene and A2058G mutation in 23S rRNA were detected in macrolide resistant isolates. Frequencies of mutation of susceptible isolates (n=26) were lower for ampicillin and erythromycin than for tetracycline. Serial exposure to antibiotics led to selection of resistant mutants. However, acquired resistance was rather unstable and was lost after subcultures in antibiotic-free medium in most mutants. Resistance to erythromycin was associated to a A2058G mutation in 23S rRNA. In conclusion, results indicate that resistance to macrolides and tetracycline is present among intestinal lactobacilli. Decrease in susceptibility following serial exposure to antibiotics might occur in lactobacilli, in a strain- and antibiotic-dependent way. Since lactobacilli are often used as probiotics, their ability to acquire resistance should be evaluated for isolates candidate to be included in probiotics based products.

In vitro selection of resistance in Escherichia coli and Klebsiella spp. at in vivo fluoroquinolone concentrations.

BACKGROUND: Fluoroquinolones are potent antimicrobial agents used for the treatment of a wide variety of community- and nosocomial- infections. However, resistance to fluoroquinolones in Enterobacteriaceae is increasingly reported. Studies assessing the ability of fluoroquinolones to select for resistance have often used antimicrobial concentrations quite different from those actually acquired at the site of infection. The present study compared the ability to select for resistance of levofloxacin, ciprofloxacin and prulifloxacin at concentrations observed in vivo in twenty strains of Escherichia coli and Klebsiella spp. isolated from patients with respiratory and urinary infections. The frequencies of spontaneous single-step mutations at plasma peak and trough antibiotic concentrations were calculated. Multi-step selection of resistance was evaluated by performing 10 serial cultures on agar plates containing a linear gradient from trough to peak antimicrobial concentrations, followed by 10 subcultures on antibiotic-free agar. E. coli resistant strains selected after multi-step selection were characterized for DNA mutations by sequencing gyrA, gyrB, parC and parE genes. RESULTS: Frequencies of mutations for levofloxacin and ciprofloxacin were less than 10-11 at peak concentration, while for prulifloxacin they ranged from <10-11 to 10-5. The lowest number of resistant mutants after multistep selection was selected by levofloxacin followed by ciprofloxacin and prulifloxacin. Both ciprofloxacin- and prulifloxacin-resistant mutants presented mutations in gyrA and parC, while levofloxacin resistance was found associated only to mutations in gyrA. CONCLUSIONS: Among the tested fluoroquinolones, levofloxacin was the most capable of limiting the occurrence of resistance.

Strain-dependent release of cytokines modulated by Lactobacillus salivarius human isolates in an in vitro model.

BACKGROUND: Oral administration of probiotics is known to modulate cytokines profile not only locally, but also systemically. Four strains of Lactobacillus salivarius, LDR0723, BNL1059, RGS1746 and CRL1528, were evaluated for their ability to modulate release of pro- and anti-inflammatory cytokines. FINDINGS: Strains were assessed for effects on production of Interleukin-12 (IL-12), Interferon-gamma (IFN-gamma), Interleukin-4 (IL-4) and Interleukin-5 (IL-5) by incubating bacterial suspensions with THP-1 macrophage like cells. Cytokines were determined by means of specific quantitative enzyme-linked immunosorbent assays.LDR0723 and CRL1528 led to a sustained increment in production of IL-12 and IFN-gamma and to a decrease in release of IL-4 and IL-5, while BNL1059 and RGS1746 favoured Th2 response, leading to a decrease in Th1/Th2 ratio with respect to unstimulated cells. CONCLUSIONS: In conclusion, capability of L. salivarius to modulate immune response was strictly strain dependent and strains of the same species might have opposite effects. Therefore, a careful evaluation of anti-inflammatory properties of lactobacilli should be performed on single strain, before any consideration on potential probiotic use.

In vitro activity of telithromycin against Haemophilus influenzae at epithelial lining fluid concentrations.

BACKGROUND: Haemophilus influenzae is one of the main aetiological agents of community-acquired respiratory tract infections. The primary aim of this study was to evaluate the antibacterial activity of telithromycin against H. influenzae clinical isolates showing different pattern of resistance in comparison with azithromycin and clarithromycin at 1/4 x, 1/2 x, 1 x, 2 x, 4 x minimum inhibitory concentration (MIC) and to peak concentrations in epithelial lining fluid (ELF). The secondary aim was to determine the influence of CO2 enriched atmosphere on bacterial susceptibility. RESULTS: Telithromycin showed high activity against H. influenzae, including strains susceptible to beta-lactams (n = 200), beta-lactamase producer (n = 50) and beta-lactamase negative ampicillin resistant (BLNAR) (n = 10), with MIC from < or =0.03 to 4 mg/L, and MIC50/MIC90 of 1/2 mg/L with susceptibility rate of 100%, and minimum bactericidal concentrations (MBC) from 2 to 4-fold higher than the MIC. Azithromycin was the most active tested macrolide (range: 0.25 - 4 mg/L; MIC50/MIC90: 1/2 mg/L), comparable to telithromycin, while clarithromycin showed the highest MICs and MBCs (range: 0.25 - 8 mg/L; MIC50/MIC90: 2/8 mg/L). In time-kill studies, telithromycin showed a bactericidal activity at the higher concentrations (4 - 2 x MIC and ELF) against all the strains, being complete after 12 - 24 hours from drug exposition. At MIC concentrations, at ambient air, bactericidal activity of telithromycin and azithromycin was quite similar at 12 hours, and better than that of clarithromycin. Besides, telithromycin and clarithromycin at ELF concentrations were bactericidal after 12 hours of incubation for most strains, while 24 hours were needed to azithromycin to be bactericidal. Incubation in CO2 significantly influenced the MICs and MBCs, and only slightly the in vitro killing curves. CONCLUSION: Telithromycin showed an in-vitro potency against H. influenzae comparable to azithromycin, with an in-vitro killing rate more rapid and superior to clarithromycin at 2X-MIC against beta-lactamase producers and BLNAR strains, and to azithromycin at ELF concentrations against beta-lactamase negative strains. Against all strains, MICs and MBCs were lower in the absence of CO2 for the tested antibiotics, showing an adverse effect of incubation in a CO2 environment. The in-vitro potency together with the tissue concentrations of the antimicrobial, should be considered in predicting efficacy.

In vitro evaluation of antibiotics' combinations for empirical therapy of suspected methicillin resistant Staphylococcus aureus severe respiratory infections.

BACKGROUND: Methicillin resistant Staphylococcus aureus (MRSA) is an increasingly common cause of nosocomial infections, causing severe morbidity and mortality worldwide, and accounting in some hospitals for more than 50% of all S. aureus diseases. Treatment of infections caused by resistant bacterial pathogens mainly relies on two therapeutic modalities: development of new antimicrobials and use of combinations of available antibiotics. Combinations of antibiotics used in the empiric treatment of infections with suspected methicillin resistant Staphylococcus aureus etiology were investigated. METHODS: Double (vancomycin or teicoplanin with either levofloxacin or cefotaxime) and triple (vancomycin or teicoplanin + levofloxacin + one among amikacin, ceftazidime, cefepime, imipenem, piperacillin/tazobactam) combinations were evaluated by means of checkerboard assay and time kill curves. Mutational rates of single and combined drugs at antimicrobial concentrations equal to the resistance breakpoints were also calculated. RESULTS: Vancomycin or teicoplanin + levofloxacin showed synergy in 16/50 and in 9/50 strains respectively, while vancomycin or teicoplanin + cefotaxime resulted synergic for 43/50 and 23/50 strains, respectively. Triple combinations, involving teicoplanin, levofloxacin and ceftazidime or piperacillin/tazobactam gave synergy in 20/25 strains. Teicoplanin + levofloxacin gave synergy in triple combinations more frequently than vancomycin + levofloxacin. For single antibiotics, mutational frequencies ranged between 10(-5) and <10(-9) for levofloxacin, cefotaxime, amikacin and imipenem, and <10(-9) for vancomycin and teicoplanin. When tested in combinations, mutational frequencies fell below 10(-9) for all the combinations. CONCLUSION: In vitro evidence of synergy between glycopeptides, fluoroquinolones (levofloxacin) and beta-lactams and of reduction of mutational frequencies by combinations are suggestive for a potential role in empirical therapy of severe pneumonia with suspected MRSA etiology.

Activity of a Lactobacillus acidophilus-based douche for the treatment of bacterial vaginosis.

OBJECTIVES: Bacterial vaginosis is characterized by alteration of the normal vaginal microflora, in which a mixed anaerobic bacterial flora becomes prevalent over the population of lacobacilli. Because administration of probiotics might be of some utility in restoring a normal flora, the present study aimed to evaluate the effect of a Lactobacillus acidophilus-strain-based douche on the vaginal environment in bacterial vaginosis. PATIENTS AND METHODS: In an open-label pilot evaluation, 40 women with bacterial vaginosis as defined by Amsel's criteria were treated for 6 days with a douche containing L. acidophilus. Vaginal smears were collected from the patients and analyzed according to Nugent's criteria at the time of diagnosis, after 6 days of treatment, and again at 20 days after the last treatment. At the same times, determination of vaginal pH and a Whiff test were performed. RESULTS: The Nugent score decreased significantly from bacterial vaginosis or an intermediate flora toward a normal flora during treatment, and remained low during the follow-up period for almost all of the patients, indicating bacterial vaginosis in 52.5% and in 7.5% of the patients before treatment and at follow-up, respectively. After treatment, significant decreases in vaginal pH were observed, to less than pH 4.5 in 34/40 women, and the odor test became negative in all of the patients. CONCLUSIONS: In this preliminary study, treatment of bacterial vaginosis with a vaginal douche containing a strain of L. acidophilus contributed to the restoration of a normal vaginal environment.

Evaluation of antibacterial in vitro activity of moxifloxacin and its effects on pulmonary clearance of Klebsiella pneumoniae in an animal experimental model.

Moxifloxacin (CAS 186286-86-8) is a recent fluoroquinolone addressed to the treatment of respiratory infections, although clinical efficacy has been shown also in the therapy of urinary tract diseases. The in vitro activity of moxifloxacin against one encapsulated strain of Klebsiella pneumoniae was determined by means of time-kill curves and by evaluation of effects of subinhibitory concentrations on bacterial morphology by means of scanning electron microscopy. Moreover, the efficacy and time requested to eradicate the same strain from lungs was determined after intratracheal infection of guinea pigs. K. pneumoniae was rapidly killed by moxifloxacin at concentrations greater than the minimum inhibitory concentration (MIC). Subinhibitory concentrations (1/4 and 1/8 of the MIC ) induced filamentation in a remarkable portion of bacteria. A progressive decrease in the bacterial content of lungs was observed during the 48-h period, with statistically significant differences compared with the control animals. In conclusion, this study provides in vivo evidence of the antimicrobial properties of moxifloxacin against K. pneumoniae.

In vitro selection of resistance in Pseudomonas aeruginosa and Acinetobacter spp. by levofloxacin and ciprofloxacin alone and in combination with beta-lactams and amikacin.

OBJECTIVES: The aim of this study was to evaluate the ability of levofloxacin and ciprofloxacin alone and in combination with either ceftazidime, cefepime, imipenem, piperacillin-tazobactam or amikacin to select for antibiotic-resistant mutants of Pseudomonas aeruginosa and Acinetobacter spp. METHODS: Clinical strains of P. aeruginosa (n = 5) and Acinetobacter spp. (n = 5) susceptible to all the drugs used in the study were assayed. Development of resistance was determined by multi-step and single-step methodologies. For multi-step studies, MICs were determined after five serial passages on antibiotic-gradient plates containing each antibiotic alone or in combination with levofloxacin or ciprofloxacin. Acquisition of resistance was defined as an increase of >or=4-fold from the starting MIC. In single-step studies, the frequency of spontaneous mutations was calculated after a passage on plates containing antibiotics alone and in combinations at concentrations equal to the highest NCCLS breakpoints. RESULTS: Serial passages on medium containing single antibiotics resulted in increased MICs for each antibiotic; MIC increases were limited by antibiotics in combination. A decrease in the number of strains with MICs above the NCCLS breakpoints occurred when fluoroquinolones were combined with a second antibiotic for both P. aeruginosa and Acinetobacter spp. isolates. Frequencies of mutation were higher for antibiotics alone than for combinations. CONCLUSIONS: Use of combinations of fluoroquinolones with beta-lactams and amikacin reduces the risk for in vitro selection of resistant P. aeruginosa and Acinetobacter spp.

Activity of levofloxacin and ciprofloxacin in combination with cefepime, ceftazidime, imipenem, piperacillin-tazobactam and amikacin against different Pseudomonas aeruginosa phenotypes and Acinetobacter spp.

BACKGROUND: Combination therapy is used to widen the antimicrobial spectrum, minimize toxicity and prevent the emergence of resistant mutants. METHODS: Synergy between levofloxacin or ciprofloxacin and ceftazidime, cefepime, imipenem, piperacillin-tazobactam and amikacin was evaluated by checkerboard assay with 55 strains and by time-kill curves with 8 strains of Pseudomonas aeruginosa and Acinetobacter spp. RESULTS: In the checkerboard assay, synergy and additivity were the most frequent effects observed among all the combinations against P. aeruginosa and Acinetobacter spp., with no significant differences between the two fluoroquinolones. No antagonism was observed. In the time-kill curves, synergy was evidenced against all the tested strains, at least for one combination at one of the time points considered. Levofloxacin and ciprofloxacin combined with ceftazidime, as well as levofloxacin plus amikacin, were synergistic for all the strains tested. CONCLUSION: Combinations of fluoroquinolones with beta-lactams or amikacin show an enhanced activity against P. aeruginosa and Acinetobacter spp.