Rapid decline of anti-hepatitis C virus (HCV) antibodies following early treatment of incident HCV infections in HIV-infected men who have sex with men.

OBJECTIVES: Following clearance of incident hepatitis C virus (HCV) infections, HCV antibody levels may decline, resulting in seroreversion. It is unclear to what extent HCV antibody level trajectories differ between patients with treatment-induced sustained virological response (SVR), those with spontaneous clearance and those with untreated replicating HCV infection. We investigated HCV antibody level dynamics in HIV-infected MSM with different clinical outcomes. METHODS: We investigated anti-HCV antibody level dynamics following an incident HCV infection in 67 HIV-infected men who have sex with men (MSM) with different clinical outcomes: SVR (n = 33), spontaneous clearance (n = 12), and untreated replicating infection (n = 22). Antibody levels were measured at the time of HCV diagnosis, and at yearly intervals for 3 years thereafter. RESULTS: At baseline, median HCV antibody levels were similar in the three groups: 13.4, 13.8 and 13.5 sample to cut-off (S/CO) for SVR, spontaneous clearance and untreated infection, respectively. Over 3 years of follow-up, SVR was associated with a more pronounced decrease in anti-HCV levels compared with spontaneous clearance and untreated infection [median decline 71% [interquartile range (IQR: 43-87%), 38% (IQR: 29-60%) and 12% (IQR: 9-22%), respectively; P < 0.001]. Seroreversions occurred in five of 33 (15%) patients with SVR and in one of 12 (8%) with spontaneous clearance. A shorter delay between time of infection and treatment start correlated with higher rates of decline in antibody levels. Seven patients experienced a reinfection. CONCLUSIONS: Treatment-induced HCV clearance was associated with a more pronounced decline in anti-HCV antibody levels and with higher rates of seroreversion compared with spontaneous clearance or untreated replicating HCV infection among HIV-infected MSM with incident HCV infections. Rapid clearance of HCV RNA following early HCV treatment might impair the development of persistent antibody titres.

Who is more likely to respond to dual treatment with pegylated-interferon and ribavirin for chronic hepatitis C? A gender-oriented analysis.

We assessed, in real-life practice, viral, demographic, genetic and metabolic factors influencing the sustained virologic response (SVR), with a gender-oriented analysis, in patients with chronic hepatitis C virus (HCV) treated with pegylated interferon and ribavirin. Six hundred and seventy naïve patients were treated with dual therapy and evaluated by gender and HCV genotype. Associations between baseline variables and SVR were assessed by multivariate logistic regression analysis. Among 362 genotype 1 patients, SVR was achieved in 158 patients (44%), and SVR was independently associated with age less than 50 years (OR 2.12; 95% CI 1.09-4.30; P=0.039) and C/C genotype rs12979860 SNP (OR 2.83; 1.19-6.74; P=0.002) in 163 females, while absence of visceral obesity (OR 2.491; 1.131-5.487; P=0.023), HCV-RNA lower than 400,000 IU/mL (OR 2.66; 1.273-5.558; P=0.009) and C/C genotype rs12979860 SNP (OR 4.969; 2.401-10.283; P<0.001) were independently associated with SVR in 199 males. Combining favourable baseline variables, the probability of obtaining SVR ranged from 27.6% to 84.2% in females, and from 14.3% to 85.7% in males. The rate of SVR was 81.1% in 175 genotype 2 patients, and 69% in 100 genotype 3 patients. Rapid virologic response was the only valid predictor of SVR regardless of other features. In conclusions, in the setting of HCV genotype 1, chronic hepatitis, combining rapid virologic response and predictive factors, which are different for females and males, allows clinicians to single out a group of patients whose likelihood of SVR exceeds 80%. For these patients, triple therapy with first-generation protease inhibitors may be unwarranted.

Epidemiology, characteristics, and outcome of infective endocarditis in Italy: the Italian Study on Endocarditis.

BACKGROUND: The characteristics of patients with infective endocarditis (IE) vary significantly by region of the world. The aim of this study was to evaluate the contemporary epidemiology, characteristics, and outcome of IE in a large, nationwide cohort of Italian patients. METHODS: We conducted a prospective, observational study at 24 medical centers in Italy, including all the consecutive patients with a definite or possible diagnosis of IE (modified Duke criteria) admitted from January 2004 through December 2009. A number of clinical variables were collected through an electronic case report form and analyzed to comprehensively delineate the features of IE. We report the data on patients with definite IE. RESULTS: A total of 1,082 patients with definite IE were included. Of these, 753 (69.6%) patients had infection on a native valve, 277 (25.6%) on a prosthetic valve, and 52 (4.8%) on an implantable electronic device. Overall, community-acquired (69.2%) was more common than nosocomial (6.2%) or non-nosocomial (24.6%) health care-associated IE. Staphylococcus aureus was the most common pathogen (22.0%). In-hospital mortality was 15.1%. From the multivariate analysis, congestive heart failure (CHF), stroke, prosthetic valve infection, S. aureus, and health care-associated acquisition were independently associated with increased in-hospital mortality, while surgery was associated with decreased mortality. CONCLUSIONS: The current mortality of IE remains high, and is mainly due to its complications, such as CHF and stroke.

Changing Italian nosocomial-community trends and heteroresistance in Staphylococcus aureus from bacteremia and endocarditis.

Bloodstream infections due to Staphylococcus aureus (BSI) are serious infections both in hospitals and in the community, possibly leading to infective endocarditis (IE). The use of glycopeptides has been recently challenged by various forms of low-level resistance. This study evaluated the distribution of MSSA and MRSA isolates from BSI and IE in 4 Italian hospitals, their antibiotic susceptibility--focusing on the emergence of hVISA--and genotypic relationships. Our results demonstrate that the epidemiology of MRSA is changing versus different STs possessing features between community-acquired (CA)- and hospital-acquired (HA)-MRSA groups; furthermore, different MSSA isolated from BSI and IE were found, with the same backgrounds of the Italian CA-MRSA. The hVISA phenotype was very frequent (19.5%) and occurred more frequently in isolates from IE and in both the MSSA and MRSA strains. As expected, hVISA were detected in MRSA with vancomycin minimum inhibitory concentrations (MICs) of 1-2 mg/l, frequently associated with the major SCCmec I and II nosocomial clones; this phenotype was also detected in some MSSA strains. The few cases of MR-hVISA infections evaluated in our study demonstrated that 5 out of 9 patients (55%) receiving a glycopeptide, died. Future studies are required to validate these findings in terms of clinical impact.

In vitro activity effects of twelve antibiotics alone and in association against twenty-seven Enterococcus faecalis strains isolated from Italian patients with infective endocarditis: high in vitro synergistic effect of the association ceftriaxone-fosfomycin.

BACKGROUND: In 2004-2008, the epidemiological and clinical Infective Endocarditis Study Group (SEI) evaluated 852 cases of infective endocarditis. Staphylococcus aureus was the main involved pathogen (24.5%) and Enterococcus faecalis etiology was described in 11% of the cases. The aim of this study was to evaluate the in vitro activity of 12 antibiotics alone and in association against 27 strains of E. faecalis isolated from blood cultures of patients with infective endocarditis. RESULTS: The results showed high in vitro activity of tigecycline, daptomycin and linezolid. A high synergistic effect was obtained with the association ceftriaxone-fosfomycin [fractional inhibitory concentration (FIC)(50) = 0.34, FIC(90) = 0.78]. Furthermore, ceftriaxone plus ampicillin presented additive results (FIC(50) = 0.66, FIC(90) = 1.00), and ceftriaxone plus fosfomycin and ceftriaxone plus ampicillin were significantly more active in vitro than each drug alone. The efficacy of ceftriaxone plus fosfomycin was confirmed by the association testing using the broth dilution technique. CONCLUSION: Fosfomycin seems particularly significant and its association with ceftriaxone could be considered as a useful therapeutic option in medical treatment of E. faecalis infective endocarditis.

Causes of death and risk factors among HIV-infected persons in the HAART era: analysis of a large urban cohort.

OBJECTIVE: We aimed to examine the clinical outcome in HIV-1-infected patients after more than 10 years of highly active antiretroviral therapy (HAART). METHODS: We analyzed data from 1,236 treatment-naïve adults who had started HAART. The primary endpoint was the yearly prevalence of death for AIDS-related causes (ARC) or for non-AIDS related causes (non-ARC). The data from our cohort were compared with that of the general population (GP) of our region. RESULTS: We observed that 116 patients died, and 58.6% of deaths were non-ARC. The death incidence decreased from 18.8% in 1998-1999 to 1.2% in 2008-2009. The leading causes of death were malignancies (35.3%), infections (21.6%), end-stage liver diseases (18.1%), and cardiovascular diseases (CVD) (6.9%). Yearly death rates were similar in the HIV-infected cohort and in the crude GP (odds ratio [OR] 1.1, 95% confidence interval [CI] 0.5-2.5), but when adjusted for age, HIV-infected patients showed a greater risk (OR 7.4, 95% CI 4.1-13.4). The difference was still highly significant when the analysis was restricted to non-ARCs (OR 4.3, 95% CI 2.07-9.2). Overall, malignancies (OR 5.7, 95% CI 2.6-12.8) and end-stage liver diseases (OR 35.0, 95% CI 15.5-78.8) were significantly more frequent than in the age-adjusted GP. CONCLUSIONS: Despite HAART, HIV-infected patients are at greater risk of death compared to a reference uninfected population.

Evolution of antiretroviral prescription and response over a period of 8 years: an Italian multicentre observational prospective cohort study.

BACKGROUND: There is very less information on the use of antiretroviral (ARV) drugs and viro-immunological outcome over calendar years in Italy. PATIENTS AND METHODS: We performed an analysis of a prospective observational cohort (MASTER) to assess antiretroviral drug use in first line HAART and explore whether initial treatment response changed over the years. RESULTS: 3,648 ARV-naive patients with available HIV-RNA and CD4+ T cell count at baseline who started their first HAART between 1997 and 2004 were studied. Mean age was 37.7 years; they were mostly males (72.3%) and Italians (81.4%). Prescription of non-nucleoside reverse transcriptase inhibitors and protease inhibitors boosted with ritonavir rose from 0.3% in 1997 to 58% in 2004 and from 0.3%in 1997 to 33.4% in 2004, respectively. Virological failures decreased over calendar years: from 42.9% in 1997 to 8.1%in 2004 after 6 months of HAART (p<0.001); from 42.1%(1997) to 10.7% (2004) after 12 months (p<0.001) and; from 39.5% (1997) to 8.2% (2004) after 18 months (p<0.001). The same trend, but less striking, was found for immunological failure rates. CONCLUSIONS: In the general Italian population of HIV-positive patients, evolution of treatment prescription correlated with improved viro-immunological outcome.

Scedosporium apiospermum soft-tissue infection: a case report and review of kidney transplant literature.

Scedosporium apiospermum is an environmental mould. Human infections caused by this organism have been observed; however, only a few case reports show its role as a telluric contaminant to kidney recipients. We have reported here a case of a dramatic soft tissue infection by S. apiospermum in a kidney-transplanted man. Surgical drainage together with voriconazole systemic therapy was successful.

Resolution of lymphocytic interstitial pneumonia in a human immunodeficiency virus-infected adult following the start of highly active antiretroviral therapy.

A case of human immunodeficiency virus (HIV)-associated lymphocytic interstitial pneumonia is described, in which improvement occurred soon after starting antiviral therapy. A 20-y-old black female with HIV infection (CD4+ count 228 x 10(6) cells and plasma viral load 379,670 copies/ml) showed radiological signs of reticulonodular infiltrates of the lungs and pulmonary functional tests indicative of a severe restrictive syndrome. Bronchoalveolar and blood cultures yielded no organism and transbronchial biopsy disclosed findings consistent with lymphocytic interstitial pneumonia. After 4 weeks on triple HIV combination therapy, she was well and respiratory tests had normalized. Six months later, a computed tomographic scan of the chest showed only residual alterations. Despite a good sirological response to treatment, no significant immune recovery occurred over a 2 y follow-up.

Antiviral potency of HAART regimens and clinical success are not strictly coupled in real life conditions: evidence from the MASTER-1 study.

PURPOSE: To compare in a real clinical setting the largely unknown midterm clinical effectiveness of two protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) regimens with different potency and tolerability profiles in naïve patients. METHOD: This study was a multicenter, open-label, randomized trial in naïve patients with less than 400 CD4+ cell count/microL, regardless of viral load. Treatment arms were hard gel capsule saquinavir (HGC-SQV)-based HAART (Arm A), with an expected more favorable tolerability profile, and indinavir (IDV)-based HAART (Arm B), with more potent virologic activity. While viro-immunological surrogate markers and World Health Organization (WHO) grade III toxicity (secondary endpoints) were regularly monitored, primary endpoints of the study were clinical and defined as any AIDS-defining event, AIDS-related death, WHO grade IV toxicity, drop outs, and protocol violations. RESULTS: 262 consecutive patients were enrolled in the study from March 1, 1997 to December 31, 1997, in 24 different Italian clinical centers (132, Arm A; 130, Arm B). After 24 months of follow-up, patients who were enrolled in Arm B showed a significantly higher rate of virological success (75% had viremia below 500 copies/mL, CI = 12.9%, in the on-treatment analysis) and immunological gain (mean CD4+ cell count increase of 274 CD4+ cells/microL, SD = 234) when compared to patients enrolled in arm A (57%, CI = 15.5% and 223 CD4+ cells/microL, SD = 192; p =.0353 and.026, respectively). Despite the significant difference observed in surrogate markers, the number of total primary endpoints did not differ in the two groups (55 out of 132 in Arm A vs. 58 out of 130 person-years in Arm B; p =.86). CONCLUSION: Our results suggest that, after 24 months of follow-up in a real clinical setting, a PI-based HAART induces significant clinical benefits in naïve patients even in the absence of a complete suppression of viral replication. However, the long-term clinical impact of the possible accumulation of viral mutations in the presence of low-grade viral replication remains to be elucidated.

Guidelines of tuberculosis preventive therapy for HIV-infected persons: a prospective, multicentre study. GISTA (Gruppo Italiano di Studio Tubercolosi e AIDS).

The aim of this study was to assess the degree of implementation of national guidelines for isoniazid preventive therapy (IPT) among human immunodeficiency virus (HIV)-infected individuals and factors affecting the impact of the programme. Twenty-eight infectious disease hospital units in Italy participated in this observational, multicentre, prospective cohort study. A number of HIV-infected subjects, (n=1,705) seen for the first time as outpatients, were included in this analysis. Of the subjects considered, 1,215 out of the 1,705 completed purified protein derivative (PPD) screening. Variables independently associated with offering and completion of PPD screening included having acquired immune deficiency syndrome (AIDS), higher educational levels and currently receiving therapy. Overall, 103 subjects were identified as candidates for IPT. Of these subjects, five had tuberculosis and 15 had contraindications to IPT. Forty subjects agreed to start IPT, and 29 completed a full-course regimen. The incidence of tuberculosis among IPT candidates who either did not begin or discontinued IPT was 6.1 per 100 person-yrs, while no cases of tuberculosis were observed in subjects completing IPT. Several factors may limit the implementation of an isoniazid preventive therapy programme for human immunodeficiency virus-infected persons. Physicians fail to offer purified protein derivative screening to patients with high degrees of immunodeficiency, and those with a more intense workload seem to pay less attention to this test. The high number of contraindications among patients and their low level of acceptance further affects the impact of isoniazid preventive therapy.

Long-term clinical benefit after highly active antiretroviral therapy in advanced HIV-1 infection, even in patients without immune reconstitution.

Our objective was to assess, in the clinical setting, the predictors of immune reconstitution (IR) and its relation with long-term clinical benefit, in HIV patients with advanced disease after highly active antiretroviral therapy (HAART) through an observational study. A retrospective cohort study in a clinical setting of 383 consecutive adult patients with advanced HIV infection (CD4+ cells <200/mm(3) at baseline), starting their first protease inhibitor (PI)-containing regimen was observed. Immune reconstitution was defined as CD4 count >200 cells/mm(3) and an increase > or =100 cells from baseline, anytime since starting HAART. Clinical benefit was defined as decreased mortality and reduction in AIDS-defining events, AIDS-related complex (ARC) events, major infections and hospitalization (days spent in hospital). During a mean follow-up of 808 days, 261 patients (68.1%) achieved IR. About 50% of these patients reached this result within one year after starting HAART. In multivariate analysis, predictors of immune recovery were sex (female) and baseline CD4 count higher than 50 cells/mm(3). The group of patients with IR had greater clinical benefit with lower mortality, fewer AIDS-defining events, shorter lengths of stay in hospital, fewer ARC events and fewer major infections during all the follow-up (P < 0.0001, tests for trends). However, although they did less remarkably than the first group of patients, even those patients who did not achieve IR experienced a significant decrease in the incidence of all the above events, as compared with the first and sometimes the second trimester after starting their HIV therapy. About 70% of HIV patients with advanced disease achieved IR after starting HAART. Such a benefit is a time-dependent effect and may even take more than 2 years to occur. Predictors of IR were sex (female) and higher baseline CD4 count (>50 cells/mm(3)). The patients who achieved immune recovery performed clinically better than patients who did not. Also the patients who failed to gain such a strong immunological recovery experienced a long-term clinical benefit. This suggests that PI-containing regimens, in advanced HIV disease, may produce a significant clinical benefit, at least temporary, even for patients who do not achieve a substantial immune response.

Gabapentin in painful HIV-related neuropathy: a report of 19 patients, preliminary observations.

The objective of this study was to assess the efficacy and safety of Gabapentin as the sole analgesic in patients with HIV-related painful neuropathy. Nineteen patients with HIV-related painful neuropathy were administered Gabapentin. Efficacy was evaluated with two 100-mm Visual Analogue Scales (VAS) (0: no symptom; 100: worst symptom), rating pain and interference of pain with sleep, performed at baseline and monthly intervals. Main Pain VAS score decreased from a baseline of 55.7 +/- 19.1 mm to a final 14.7 +/- 18.6 mm (ANOVA P = 0.0001) and mean Sleep Interference VAS score decreased from a baseline of 60.4 +/- 31.9 mm to a final 15.5 +/- 27.7 mm (ANOVA P = 0.0001). Gabapentin provided significant pain relief in our patients with HIV-associated painful sensory neuropathy.

Severe lactic acidosis and thiamine administration in an HIV-infected patient on HAART.

Severe lactic acidosis has been increasingly reported as a potentially fatal complication of HIV treatment. We report on an asymptomatic HIV-infected woman treated with stavudine, lamivudine and indinavir for one year. She was hospitalized because of progressive dispnoea, oedema, cyanosis and severe lactic acidosis. Arterial blood pH was 6.98, bicarbonate 4.4 mmol/l (normal value 22-26), blood lactate: 29.7 mmol/l (normal value <2.2). Hepatic function was normal. She had an impressively rapid response (within a few hours) to empirical treatment with thiamine (100 mg i.v.). No evidence of sepsis or malabsorption were identified and vitamin B1 level was not tested before thiamine infusion. Three months later she was re-started successfully on nelfinavir plus nevirapine. The rapid response to thiamine infusion deserves a careful attention and such an approach should be considered in similar cases as a support treatment of this potentially life-threatening complication of HIV therapy.

Virological and immunological responses to a once-a-day antiretroviral regimen with didanosine, lamivudine and efavirenz.

Current antiretroviral drugs cannot eradicate HIV infections, and persons living with HIV are often faced with very demanding daily therapeutic schedules that can induce poor adherence. More conveniently dosed and patient-friendly regimens are needed. We investigated, in this 48-week pilot study, a once-a-day highly active antiretroviral therapy regimen of didanosine, lamivudine and efavirenz. Seventy-five consecutive antiretroviral-naive subjects were enrolled. Over the 48-week period, plasma HIV-RNA levels declined sharply, with a median decrease at the end of the observation time >3.4 log copies/ml. The proportion of patients achieving a plasma HIV-RNA level below the limit of detection (50 copies/ml) was 77% (intention to treat analysis) at the end of the study period. The mean CD4 cell count increased steadily over time from 251 to 459 cells/microl. Antiviral efficacy was similar in patients with a baseline HIV-RNA level above or below 100,000 copies/ml. However, patients with a baseline CD4 cell count <200 cells/microl showed a significantly worse virological response than that observed in patients with higher baseline CD4 counts. Overall 15 patients interrupted therapy. In four cases treatment interruption was due to lack of treatment response; three additional patients were lost to follow-up or withdrew informed consent. Eight patients stopped therapy because of adverse events. The once-daily combination of didanosine, lamivudine and efavirenz resulted in sustained viral suppression and was well-accepted by patients. This regimen may offer advantages in selected difficult-to-treat populations, allows directly observed therapy and can be a safe and effective alternative in antiretroviral-naive patients. These encouraging pilot results need to be confirmed in a comparative clinical trial.

A randomized trial comparing the introduction of ritonavir or indinavir in 1251 nucleoside-experienced patients with advanced HIV infection.

ISS-IP1, a multicenter, randomized, 48-week open trial, was designed to compare the introduction of ritonavir or indinavir in patients with previous nucleoside experience and CD4+ cell counts below 50/mm3. Concomitant antiretroviral treatment with nucleoside analogs was allowed. Primary efficacy measures were survival and time to a new AIDS-defining event or death, analyzed through the whole period of observation by the intention-to-treat approach. Primary toxicity measures were time to treatment discontinuation and adverse events, grade at least 3/serious, analyzed by an on-treatment approach. Evaluation-of efficacy also included CD4+ cell and RNA response. The trial enrolled 1251 patients in 5 months. At baseline, mean CD4+ cell count was about 20 cells/mm3 and mean HIV RNA copy number was 4.9 log10/ml in both groups. Overall, 402 patients in the ritonavir group and 250 patients in the indinavir group permanently discontinued the assigned treatment (relative risk, 1.96; 95% CI, 1.68-2.30; p = 0.0001), with most of this difference dependent on a higher number of discontinuation for adverse events in the ritonavir group. After a mean follow-up of 307 days (ritonavir, 304; indinavir, 309), 124 deaths (ritonavir, 61; indinavir, 63; relative risk, 0.96; 95% CI, 0.67-1.36; p = 0.80) and 330 new AIDS-defining events (ritonavir, 170; indinavir, 160; relative risk, 1.05; 95% CI, 0.85-1.31; p = 0.60) were observed. CD4+ cell counts increased in both groups in patients still receiving treatment, with about 100 cells gained by week 24 and 150 cells gained by week 48. Body weight also increased over time in both groups. Analysis of RNA response showed a decrease of 1.5 log10 or higher in both treatment groups. Overall, 400 patients in the ritonavir group and 338 patients in the indinavir group developed at least one grade 3/serious new adverse event during follow-up (relative risk, 1.48; 95% CI, 1.28-1.72; p = 0.0001). Favorable CD4+ cell and RNA responses at 24 and 48 weeks were observed in both groups of patients remaining on treatment. Indinavir showed slightly better effects in sustaining RNA, CD4+ cell, and body weight responses. Ritonavir and indinavir results were comparable in terms of clinical outcome (survival and AIDS-defining events).

Duration of viral suppression in patients on stable therapy for HIV-1 infection is predicted by plasma HIV RNA level after 1 month of treatment.

UNLABELLED: The aim of this study was to assess the predictive value of HIV RNA levels after 1 month of therapy on the long-term virologic outcome in an unselected general population of HIV-infected patients. DESIGN: Analysis was conducted retrospectively on an ongoing clinical cohort of HIV-positive patients who were receiving antiretroviral treatment. Data on 575 patients were analyzed. RESULTS: The HIV RNA value at 1 month was significantly correlated with the virologic outcome after 12 and 24 months of therapy (R = 0.258 and R = 0.44, respectively). The predictive value of the 1-month viral load was also statistically significant after stratification for baseline CD4 T-cell counts. Prediction was similar in highly compromised patients (CD4 < or = 100 cells/microl; R = 0.426; p = .001) or in patients with a better immunologic status (R = 0.419; p < .0001). It retained validity in patients who were naive or experienced for antiretroviral therapy. CONCLUSION: HIV RNA level after 1 month of therapy is a useful prognostic marker in HIV-infected patients. It predicts long-term virologic and immunologic outcome. A cutoff level of 5000 copies/ml identifies patients most likely to fail current therapy. In these patients, a more aggressive strategy or specific diagnostic interventions to clarify the relative influence of viral resistance and/or subtherapeutic regimens is advised.

In-vitro activity of moxifloxacin combined with other antibacterials against methicillin-resistant Staphylococcus aureus.

Killing kinetic experiments were performed with moxifloxacin, a novel fluoroquinolone, vancomycin, clarithromycin, cotrimoxazole, gentamicin, rifampicin and with moxifloxacin in combination with each of the above drugs against six methicillin-resistant Staphylococcus aureus clinical isolates. Half of the strains were ciprofloxacin-resistant. The early bactericidal effect of moxifloxacin alone was substantially greater than that of the other tested drugs. No antagonism was observed between moxifloxacin and each of the other drugs. For each combination the mean decrease in the number of organisms (after 6 hours) was comparable to that achieved with moxifloxacin alone, however, when moxifloxacin was tested with gentamicin, a slight increase in the bactericidal effect was observed.

Effects of subinhibitory concentrations of moxifloxacin in an in-vitro dynamic model.

The postantibiotic effect (PAE), sub-MIC effect (SME) and postantibiotic sub-MIC effect (PASME) of moxifloxacin were investigated in an in-vitro dynamic model reproducing in-vivo elimination kinetics of the antibiotic. The PAE was induced by exposing strains of Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli and Klebsiella pneumoniae to 5 x MIC of the antibiotic for 1.5 hours. After induction, cultures were washed to eliminate the antibiotic and resuspended into the dynamic model either in the presence or absence of a subinhibitory concentration of the antibacterial agent of 0.5 x MIC. Unexposed controls were treated similarly. PASMEs were constantly longer than corresponding SMEs, but differences between them were not statistically significant. Both PASMEs (mean 11:17 hours, range from 8:17 to 14:57) and SMEs (mean 9:23 hours, range from 6:03 to 12:34) had an initial bactericidal effect and were significantly longer than PAEs (mean 1:31 hours, range from 0:21 to 2:14). The primary effect of moxifloxacin sub-MICs appears to be prevalent in PAE. The possibility of once-daily dosing of the drug is strengthened.