Clinical response to aminoglycoside therapy: importance of the ratio of peak concentration to minimal inhibitory concentration

In an examination of the relationships among plasma aminoglycoside concentrations, the minimal inhibitory concentration (MIC) for the infecting organism, and therapeutic outcome, data were analyzed from 236 patients with gram-negative bacterial infections who were participants in four clinical trials of gentamicin, tobramycin, and amikacin. Clinical response to therapy occurred in 188 (80%) patients. Elevated maximal and mean peak aminoglycoside concentration/MIC ratios were strongly associated with clinical response (P less than .00001 and P less than .0001, respectively). A graded dose-response effect was found between an increasing maximal peak concentration/MIC ratio and clinical response. By logistic regression the peak concentration/MIC ratios were associated significantly with clinical response after adjustment for underlying severity of illness and other factors correlated with response. These results demonstrate that a high peak concentration relative to the MIC for the infecting organism is a major determinant of the clinical response to aminoglycoside therapy.

Treatment correlates of successful outcomes in pulmonary multidrug-resistant tuberculosis: an individual patient data meta-analysis

BACKGROUND

Treatment outcomes for multidrug-resistant tuberculosis remain poor. We aimed to estimate the association of treatment success and death with the use of individual drugs, and the optimal number and duration of treatment with those drugs in patients with multidrug-resistant tuberculosis.

METHODS

In this individual patient data meta-analysis, we searched MEDLINE, Embase, and the Cochrane Library to identify potentially eligible observational and experimental studies published between Jan 1, 2009, and April 30, 2016. We also searched reference lists from all systematic reviews of treatment of multidrug-resistant tuberculosis published since 2009. To be eligible, studies had to report original results, with end of treatment outcomes (treatment completion [success], failure, or relapse) in cohorts of at least 25 adults (aged >18 years). We used anonymised individual patient data from eligible studies, provided by study investigators, regarding clinical characteristics, treatment, and outcomes. Using propensity score-matched generalised mixed effects logistic, or linear regression, we calculated adjusted odds ratios and adjusted risk differences for success or death during treatment, for specific drugs currently used to treat multidrug-resistant tuberculosis, as well as the number of drugs used and treatment duration.

FINDINGS

Of 12 030 patients from 25 countries in 50 studies, 7346 (61%) had treatment success, 1017 (8%) had failure or relapse, and 1729 (14%) died. Compared with failure or relapse, treatment success was positively associated with the use of linezolid (adjusted risk difference 0·15, 95% CI 0·11 to 0·18), levofloxacin (0·15, 0·13 to 0·18), carbapenems (0·14, 0·06 to 0·21), moxifloxacin (0·11, 0·08 to 0·14), bedaquiline (0·10, 0·05 to 0·14), and clofazimine (0·06, 0·01 to 0·10). There was a significant association between reduced mortality and use of linezolid (-0·20, -0·23 to -0·16), levofloxacin (-0·06, -0·09 to -0·04), moxifloxacin (-0·07, -0·10 to -0·04), or bedaquiline (-0·14, -0·19 to -0·10). Compared with regimens without any injectable drug, amikacin provided modest benefits, but kanamycin and capreomycin were associated with worse outcomes. The remaining drugs were associated with slight or no improvements in outcomes. Treatment outcomes were significantly worse for most drugs if they were used despite in-vitro resistance. The optimal number of effective drugs seemed to be five in the initial phase, and four in the continuation phase. In these adjusted analyses, heterogeneity, based on a simulated I² method, was high for approximately half the estimates for specific drugs, although relatively low for number of drugs and durations analyses.

INTERPRETATION

Although inferences are limited by the observational nature of these data, treatment outcomes were significantly better with use of linezolid, later generation fluoroquinolones, bedaquiline, clofazimine, and carbapenems for treatment of multidrug-resistant tuberculosis. These findings emphasise the need for trials to ascertain the optimal combination and duration of these drugs for treatment of this condition.

FUNDING

American Thoracic Society, Canadian Institutes of Health Research, US Centers for Disease Control and Prevention, European Respiratory Society, Infectious Diseases Society of America.

Clinical significance of differentiation of Mycobacterium massiliense from Mycobacterium abscessus

RATIONALE

Mycobacterium massiliense has been recognized as a separate species from Mycobacterium abscessus; however, little is known regarding the clinical impact of this differentiation.

OBJECTIVES

To compare clinical features and treatment outcomes between patients with M. abscessus lung disease and those with M. massiliense lung disease.

METHODS

We performed molecular identification of stored clinical isolates of M. abscessus complex and compared clinical characteristics and treatment outcomes between 64 patients with M. abscessus lung disease and 81 patients with M. massiliense lung disease.

MEASUREMENTS AND MAIN RESULTS

The clinical and radiographic manifestations of disease caused by each species were similar. Standardized combination antibiotic therapy, including a clarithromycin-containing regimen in combination with an initial 4-week course of cefoxitin and amikacin, was given to 57 patients (24 with M. abscessus and 33 with M. massiliense) for more than 12 months. The proportion of patients with sputum conversion and maintenance of negative sputum cultures was higher in patients with M. massiliense infection (88%) than in those with M. abscessus infection (25%; P < 0.001). Inducible resistance to clarithromycin (minimal inhibitory concentrations ≥ 32 μg/ml) was found in all tested M. abscessus isolates (n = 19), but in none of the M. massiliense isolates (n = 28).

CONCLUSIONS

Treatment response rates to combination antibiotic therapy including clarithromycin were much higher in patients with M. massiliense lung disease than in those with M. abscessus lung disease. The inducible resistance to clarithromycin could explain the lack of efficacy of clarithromycin-containing antibiotic therapy against M. abscessus lung disease.

Transferable enzymatic resistance to third-generation cephalosporins during nosocomial outbreak of multiresistant Klebsiella pneumoniae

Klebsiella pneumoniae strains that were resistant to third-generation cephalosporins and amikacin were recovered from 62 of 395 patients (15.7%) during 1986. 25 isolates (40%) caused urinary tract infections. The outbreak involved three intensive care units (54 isolates), and spread from one unit to another and then to four wards (8 isolates). K pneumoniae of various serotypes and strains of different Enterobacteriaceae demonstrating the same antibiotic resistance pattern were isolated, which suggests dissemination of an R-factor. The isolates had low-level resistance to third-generation cephalosporins (mode minimum inhibitory concentration of cefotaxime, 2 mg/l) but remained sensitive to cephamycins. Cefotaxime was effective in cases of uncomplicated urinary tract infection, but failed in major infections at other sites. 1-5 mg/l of the beta-lactamase inhibitors clavulanic acid or sulbactam restored normal activity to cefotaxime against the multiresistant strains. Resistance to third-generation cephalosporins was mediated by a new broad-spectrum enzyme of isoelectric point 6.3. Resistance to beta-lactams and aminoglycosides was transferable to Escherichia coli. The emergence of transferable enzymatic resistance to newer beta-lactams in K pneumoniae strains indicates a major risk of spread of such resistance to otherwise sensitive strains.

Association of aminoglycoside plasma levels with therapeutic outcome in gram-negative pneumonia

To determine the association of aminoglycoside plasma levels with therapeutic outcome in gram-negative pneumonia, the case reports of 37 patients from four prospective, randomized, controlled trials of gentamicin, tobramycin, and amikacin were analyzed. Twenty (54 percent) of these patients had a favorable outcome. Patients with maximal one-hour postinfusion (peak) levels of 7 micrograms/ml or greater for gentamicin and tobramycin or 28 micrograms/ml or greater for amikacin more often had successful outcomes (14 of 20, 70 percent) than those with levels less than this (six of 19, 32 percent) (p less than 0.006). Patients with overall mean peak levels of 6 micrograms/ml or greater for gentamicin and tobramycin or 24 micrograms/ml or greater for amikacin more often had successful outcomes than those with levels less than this (six of 17, 35 percent) (p less than 0.04). The initial patient temperature, serum urea nitrogen/creatinine ratio, initial polymorphonuclear leukocyte count, and age were also associated with outcome; but by multivariate analysis, achieving an adequate peak concentration was the most important discriminating factor. These results suggest the potential importance of achieving adequate aminoglycoside levels in patients with gram-negative pneumonia.

Antibiotic treatment of Mycobacterium abscessus lung disease: a retrospective analysis of 65 patients

RATIONALE

The optimal therapeutic regimen and duration of treatment for Mycobacterium abscessus lung disease is not well established.

OBJECTIVES

To assess the efficacy of a standardized combination antibiotic therapy for the treatment of M. abscessus lung disease.

METHODS

Sixty-five patients (11 males, 55 females, median age 55 yr) with M. abscessus lung disease were treated with clarithromycin, ciprofloxacin, and doxycycline, together with an initial regimen of amikacin and cefoxitin for the first 4 weeks of hospitalization.

MEASUREMENTS AND MAIN RESULTS

Treatment response rates were 83% for symptoms and 74% for high-resolution computed tomography. Sputum conversion and maintenance of negative sputum cultures for more than 12 months was achieved in 38 (58%) patients. These rates were significantly lower in patients whose isolates were resistant to clarithromycin (17%, 2/12) compared with those whose isolates were susceptible or intermediate to clarithromycin (64%, 21/33; P = 0.007). Neutropenia and thrombocytopenia associated with cefoxitin developed in 33 (51%) and 4 (6%) patients, respectively. Drug-induced hepatotoxicity occurred in 10 (15%) patients. Because of these adverse reactions, cefoxitin was discontinued in 39 (60%) patients after treatment for a median of 22 days.

CONCLUSIONS

Standardized combination antibiotic therapy was moderately effective in treating M. abscessus lung disease. However, frequent adverse reactions and the potential for long-duration hospitalization are important problems that remain to be solved.

Treatment of nonpulmonary infections due to Mycobacterium fortuitum and Mycobacterium chelonei on the basis of in vitro susceptibilities

One hundred twenty-three patients with nonpulmonary infections due to Mycobacterium fortuitum or Mycobacterium chelonei were treated by wound debridement and with chemotherapy on the basis of in vitro susceptibilities of the organism. Of 76 patients with infections caused by M. fortuitum, 13 required no therapy or were adequately treated with surgery alone. Patients with active localized disease received single drug therapy (usually with a sulfonamide) for a mean period of 10.6 weeks for cellulitis and seven months for osteomyelitis. Patients with extensive disease received amikacin or amikacin plus cefoxitin (mean, four weeks) followed by a sulfonamide (mean, six months). The 47 patients with infections caused by M. chelonei received no therapy or were treated with surgery alone (6); with amikacin (10), erythromycin (6), doxycycline (3), or cefoxitin (1); or with amikacin plus cefoxitin followed by cefoxitin alone for a total of 10-12 weeks (20); or other multiple-drug regimens (1). Surgery was performed on 74 (60%) patients. Schlichter tests or serum drug levels were determined for 81 (66%) patients. Response to therapy was excellent; 68 (90%) infections with M. fortuitum and 34 (72%) with M. chelonei were successfully treated. Cultures became negative within six weeks of chemotherapy, except for sternal osteomyelitis, for which cultures were not negative until up to 14 weeks. Follow-up for a mean period of 12 months following therapy was possible in 80% of cases. Relapses were rare except in patients with disseminated disease, and drug resistance developed in only one patient. These studies demonstrate the value of routine susceptibility testing of these mycobacterial species and the benefit of chemotherapy on the basis of in vitro susceptibilities.

Controlled comparison of amikacin and gentamicin

Amikacin or gentamicin was used to treat 174 patients with suspected severe gram-negative infections in a prospective, randomized, double-blind trial. Enteric gram-negative bacilli were pathogenic in 71 cases (39 treated with amikacin, and 32 with gentamicin). Amikacin was effective in 10 to 12 bacteremias, 21 of 24 urinary-tract infections, two of five pneumonias and four of six other serious tissue infections. The toal favorable response rate was 77 per cent for amikacin and 78 per cent for gentamicin. Nephrotoxicity and auditory toxicity could be evaluated in 124 and 67 cases respectively. Definite nephrotoxicity developed in five of 62 (8 per cent) receiving amikacin and seven of 62 (11 per cent) given gentamicin, and possible nephrotoxicity developed in four patients in both groups. Definite ototoxicity developed in four patients in both groups. Definite otoxicity developed in two of 34 (6 per cent) and three of 30 (10 per cent) respectively. These differences were not statistically significant (by chisquare analysis, P greater than 0.05). The results indicate that amikacin is effective against severe gram-negative infections and is not more and not less ototoxic or nephrotoxic than gentamicin.

Mycobacterium abscessus: an emerging rapid-growing potential pathogen. Review article

Mycobacterium abscessus is the most pathogenic and chemotherapy-resistant rapid-growing mycobacterium. It is commonly associated with contaminated traumatic skin wounds and with post-surgical soft tissue infections. It is also one of the mycobacteria that are most often isolated from cystic fibrosis patients. It is essential to differentiate this species from the formerly indistinct "M. chelonae-complex", as chemotherapy is especially difficult in M. abscessussenso strictu. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents with an effect on M. abscessus, and should preferably be supplemented with other drugs since long-term monotherapy may cause resistance. Amikacin is a major parenteral drug against M. abscessus that should also be given in combination with another drug. The recently introduced drug tigecycline may prove to be an important addition to chemotherapy, but has yet to be fully clinically evaluated as an antimycobacterial agent. Surgery can be curative, or at least helpful, in the healing of M. abscessus infection, and if conducted, it should include the removal of all foreign or necrotic material. There is increasing awareness of M. abscessus as an emerging pathogen.

Aminoglycoside resistance and aminoglycoside usage: ten years of experience in one hospital

For 10 years the 700-bed Minneapolis Veterans Affairs Medical Center has conducted a policy of carefully controlled aminoglycoside usage and monitoring of resistance of over 25,000 aerobic and facultative gram-negative bacillary isolates to the aminoglycosides. On two occasions during the 1980s, our experience of introducing amikacin at a high level of usage was associated with a significant reduction in resistance to gentamicin and tobramycin among gram-negative bacilli. Rapid reintroduction of gentamicin usage in 1982 after the first amikacin period was associated with a significant and rapid increase in gentamicin and tobramycin resistance. However, in 1986, gentamicin was again reintroduced to this institution at an initially modest level, and the percentage of usage of gentamicin was gradually increased over a 15-month period without a significant change in resistance to gentamicin, tobramycin, or amikacin while maintaining an overall 68% gentamicin usage and 30% amikacin usage. Aminoglycoside usage (measured as patient days) rose steadily from under 2,000 patient days per quarter in 1980 and 1981 to over 3,000 days per quarter in 1985. Since 1985, usage has declined to under 2,500 patient days per quarter in 1990. This usage rise and fall occurred during a steadily declining daily patient census that was 590 in 1980 and 465 in 1989. A move to a new hospital building in June 1988 was associated with an additional significant decline in resistance to all aminoglycosides (P less than 0.05), continuing a trend that was evident for the year preceding the move. Resistance to aminoglycoside antibiotics is now at the lowest level in 10 years at this institution, with only one gram-negative organism, Pseudomonas aeruginosa, that exhibits more than 5% resistance to gentamicin and no gram-negative species that are more than 5% resistant to amikacin and tobramycin.

Piperacillin-tazobactam plus amikacin versus ceftazidime plus amikacin as empiric therapy for fever in granulocytopenic patients with cancer. The International Antimicrobial Therapy Cooperative Group of the European Organization for Research and Treatment of Cancer

Gram-positive bacteria have become the predominant infecting organisms in granulocytopenic cancer patients. Empiric antibiotic regimens used in febrile neutropenic patients often include an extended-spectrum cephalosporin, but the response to therapy in gram-positive coccal bacteremia has been unsatisfactory. Thus, new antibiotics with better activity against gram-positive bacteria should be tested. The objective of this prospective randomized controlled study was to evaluate and compare the efficacy and tolerance of piperacillintazobactam plus amikacin with that of ceftazidime plus amikacin, the standard regimen of the International Antimicrobial Therapy Cooperative Group of the European Organization for Research and Treatment of Cancer, in the empiric treatment of febrile granulocytopenic cancer patients. A total of 858 episodes were eligible for this study, and 706 episodes were assessable for efficacy. The antibiotic treatment was successful in 210 (61%) of 342 episodes in the piperacillin-tazobactam-amikacin group compared with 196 (54%) of 364 episodes treated with ceftazidime plus amikacin (P = 0.05). The time to defervescence was significantly shorter (P = 0.01) and the time to failure was significantly longer (P = 0.02) in the piperacillin-tazobactam-amikacin group. A significant difference in response to bacteremic infections between the two patient groups was found: piperacillin-tazobactam plus amikacin was successful in 40 of 80 episodes (50%), and ceftazidime plus amikacin was successful in 35 of 101 episodes (35%) (P = 0.05). A multivariate analysis showed that the probability of failure was significantly greater with ceftazidime plus amikacin than with piperacillin-tazobactam plus amikacin (P = 0.02). This trial suggests that piperacillin-tazobactam plus amikacin is more effective than ceftazidime plus amikacin for the empiric treatment of fever and bacteremia in granulocytopenic cancer patients. Although cutaneous reaction was more frequently associated with piperacillin-tazobactam plus amikacin than with ceftazidime-amikacin, this unwanted effect was relatively mild and its incidence was comparable to that of other penicillin compounds.

Treatment of disseminated Mycobacterium avium complex infection in AIDS with amikacin, ethambutol, rifampin, and ciprofloxacin. California Collaborative Treatment Group

OBJECTIVE

To determine the efficacy of combination drug therapy for disseminated Mycobacterium avium complex infection in patients with the acquired immunodeficiency syndrome (AIDS).

DESIGN

Prospective, nonrandomized, before-after comparison.

SETTING

Outpatient clinics at three university medical centers.

PATIENTS

Seventeen patients with at least two consecutive blood cultures positive for M. avium complex who had not been previously treated with antituberculous medications. Fifteen of the seventeen patients completed at least 4 weeks of treatment.

INTERVENTION

Patients received daily intravenous amikacin (7.5 mg/kg body weight) for the first 4 weeks plus the following oral medications for at least 12 weeks: ciprofloxacin, 750 mg twice daily; ethambutol, 1000 mg daily; and rifampin, 600 mg daily.

MEASUREMENTS AND MAIN RESULTS

The baseline geometric mean colony count from blood cultures decreased from 537/mL to 14/mL (P less than 0.001) after 4 weeks of therapy. The microbiologic suppression was sustained while on treatment and was associated with a decrease in systemic symptoms related to M. avium complex infection. Premature withdrawal from treatment (less than 12 weeks) occurred in 7 of 17 patients. The commonest reasons for early withdrawal were gastrointestinal intolerance and hepatic toxicity.

CONCLUSIONS

Mycobacterial load and systemic symptoms in patients with AIDS and disseminated M. avium complex infection can be effectively reduced by a regimen containing amikacin, ethambutol, rifampin, and ciprofloxacin.

Prospective randomized comparison of three antibiotic regimens for empirical therapy of suspected bacteremic infection in febrile granulocytopenic patients

The standard regimen used by members of the European Organization for Research on Treatment of Cancer Antimicrobial Therapy Cooperative Group for empiric therapy of febrile neutropenic cancer patients has been treatment with ticarcillin plus amikacin. A three-arm prospective randomized controlled trial was performed to determine whether the extended-spectrum antipseudomonal penicillin azlocillin or the extended-spectrum cephalosporin cefotaxime had more or less efficacy than the beta-lactam in the ticarcillin-plus-amikacin regimen. A total of 742 patients from 22 institutions were evaluated. Single gram-negative rod bacteremias accounted for 83 episodes, and it was among these patients that the prognosis was least satisfactory, leading to a more intensive evaluation of this patient group. In these patients the azlocillin-plus-amikacin regimen resulted in a 66% response rate, compared with a 37% response rate for patients who received cefotaxime plus amikacin (P = 0.080) and a 47% response rate for patients who received ticarcillin plus amikacin (P = 0.207). The patients with gram-negative rod bacteremias and persistently profound granulocytopenia had substantially poorer response rates (37%) than the patients with rising granulocyte counts (73%; P = 0.004). A logistic regression analysis indicated that the following factors also affected infection resolution: beta-lactam utilization in the regimen (azlocillin was better than ticarcillin or cefotaxime), resolution of profound granulocytopenia (less than 100 cells per microliter) during therapy, and susceptibility to the beta-lactam antibiotic.

Significance of antimicrobial synergism for the outcome of gram negative sepsis

Amikacin plus penicillin (A+P) was compared to amikacin plus carbenicillin (A+C) in a double-blind study. Therapy with one of these combinations was given, as soon as servere infection was suspected, to 117 patients with proved gram negative infection, none of whom was granulocytopenic. Gram negative bacteremia was documented retrospectively in 52 patients; 25 had received A+P and 27 had been treated with A+C. All the isolated gram negative pathogens were sensitive to amikacin (MIC less than 12 microng/ml). In the A+P group, 55 per cent of the patients responded favorably while in the A+C group 63 per cent did respond; the difference was more striking for bacteremic patients: 52 per cent responded in the A+P group and 70 per cent in the A+C group. This difference, however, was not statistically significant. The outcome of patients whose infection was treated by synergistic combinations against the offending pathogen was better (66 per cent) than that observed in patients who received nonsynergistic combinations (48 per cent) (p less than 0.05). Once again the results were more striking in the bacteremic patients (p less than 0.01). A favorable outcome was associated also with a high (larger than or equal to 1/8) bactericidal activity of the diluted serum of the treated patient against the offending pathogen (p less than 0.05). This study suggests that the optimal therapy in gram negative septicemia might be the administration of synergistic combinations of antibiotics.

Vancomycin, ticarcillin, and amikacin compared with ticarcillin-clavulanate and amikacin in the empirical treatment of febrile, neutropenic children with cancer

We assessed two antibiotic regimens--vancomycin, ticarcillin, and amikacin, as compared with a vancomycin placebo, ticarcillin-clavulanate, and amikacin--as initial empirical therapy for febrile, neutropenic children with cancer. In a randomized, double-blind clinical trial, the planned 10-day treatment was unsuccessful in 15 percent of the vancomycin, ticarcillin, and amikacin group (n = 53), as compared with 38 percent of the group receiving ticarcillin-clavulanate and amikacin (n = 48) (P = 0.010). Of 10 episodes of breakthrough bacteremia, 9 (1 fatal) occurred in patients treated with ticarcillin-clavulanate and amikacin (P = 0.006). Each of the 10 microbial isolates was a gram-positive bacterium with similar susceptibilities to vancomycin and ticarcillin-clavulanate in vitro. Both regimens were well tolerated. None of the patients had detectable renal dysfunction, but those receiving vancomycin, ticarcillin, and amikacin were more likely to have twofold increases in serum hepatic-enzyme activity. Rashes consistent with the "red-man" syndrome occurred in three patients upon the infusion of vancomycin and in three others who received a placebo. We conclude that the combination of vancomycin, ticarcillin, and amikacin is more effective than ticarcillin-clavulanate and amikacin as empirical antibiotic therapy in clinical settings in which gram-positive bacteremias are a serious problem.

Aminoglycoside volume of distribution and illness severity in critically ill septic patients

The volume of distribution of amikacin and the APACHE II score were determined in 42 critically ill patients being treated for a gram-negative infection. The mean volume of distribution (Vdt) was 0.41 +/- 0.12 l/kg with a wide range (normal of 0.25 l/kg). There was a good relationship between the Vdt and illness severity as measured by the APACHE II score (r = 0.70; P < 0.001). Critically ill patients should receive larger loading doses of aminoglycosides in order to achieve therapeutic blood levels. The aminoglycoside Vdt may be useful in determining the degree of capillary leak and tissue oedema that accompanies sepsis.

Antimicrobial therapy for pulmonary pathogenic colonisation and infection by Pseudomonas aeruginosa in cystic fibrosis patients

Pseudomonas aeruginosa colonisation has a negative effect on pulmonary function in cystic fibrosis patients. The organism can only be eradicated in the early stage of colonisation, while reduction of bacterial density is desirable during chronic colonisation or exacerbations. Monthly, or at least 3-monthly, microbiological culture is advisable for patients without previous evidence of P. aeruginosa colonisation. Cultures should be performed at least every 2-3 months in patients with well-established colonisation, and always during exacerbations or hospitalisations. Treatment of patients following the first isolation of P. aeruginosa, but with no clinical signs of colonisation, should be with oral ciprofloxacin (15-20 mg/kg twice-daily for 3-4 weeks) plus inhaled tobramycin or colistin (intravenous treatment with or without inhaled treatment can be used as an alternative), while patients with acute infection should be treated for 14-21 days with high doses of two intravenous antimicrobial agents, with or without an inhaled treatment during or at the end of the intravenous treatment. Maintenance treatment after development of chronic P. aeruginosa infection/colonisation (pathogenic colonisation) in stable patients (aged>6 years) should be with inhaled tobramycin (300 mg twice-daily) in 28-day cycles (on-off) or, as an alternative, colistin (1-3 million units twice-daily). Colistin is also a possible choice for patients aged<6 years. Treatment can be completed with oral ciprofloxacin (3-4 weeks every 3-4 months) for patients with mild pulmonary symptoms, or intravenously (every 3-4 months) for those with severe symptoms or isolates with ciprofloxacin resistance. Moderate and serious exacerbations can be treated with intravenous ceftazidime (50-70 mg/kg three-times-daily) or cefepime (50 mg/kg three-times-daily) plus tobramycin (5-10 mg/kg every 24 h) or amikacin (20-30 mg/kg every 24 h) for 2-3 weeks. Oral ciprofloxacin is recommended for patients with mild pulmonary disease. If multiresistant P. aeruginosa is isolated, antimicrobial agents that retain activity are recommended and epidemiological control measures should be established.

Lung deposition and efficiency of nebulized amikacin during Escherichia coli pneumonia in ventilated piglets

Lung tissue deposition and antibacterial efficiency of nebulized and intravenous amikacin (AMK) were compared in anesthetized and ventilated piglets suffering from a bronchopneumonia produced by the intrabronchial inoculation of Escherichia coli. AMK was administered 24 hours after the inoculation either through an ultrasonic nebulizer (45 mg x kg-1, n = 10) or by intravenous infusion (15 mg x kg-1, n = 8). Piglets were killed 1 hour after a second AMK administration performed 24 hours after the first one, and lung tissue concentrations of AMK and lung bacterial burden were assessed on multiple lung specimens. The amount of nebulized AMK reaching the tracheobronchial tree represented 38 +/- 6% of the initial nebulizer AMK charge. After nebulization, AMK lung tissue concentrations were 3- to 30-fold higher than after intravenous administration and were influenced by the severity of lung lesions: 188 +/- 175 microg x g-1 in lung segments with mild bronchopneumonia versus 40 +/- 65 microg x g-1 in lung segments with severe bronchopneumonia (p < 0.01). Lung bacterial burden was significantly lower in the aerosol group than in the intravenous group (median = 0 colony forming units. g-1 versus median = 5 x 10(2) colony forming units x g-1, p < 0.001). In conclusion, the deposition of AMK in infected lung parenchyma and the efficiency of bacterial killing were greater after nebulization than after intravenous administration.

Treatment of Mycobacterium avium complex bacteremia in AIDS with a four-drug oral regimen. Rifampin, ethambutol, clofazimine, and ciprofloxacin. The California Collaborative Treatment Group

OBJECTIVE

To determine the quantitative microbiologic response and the clinical response of patients with Mycobacterium avium complex bacteremia and AIDS to an oral antimycobacterial regimen.

DESIGN

A phase II, multicenter clinical trial.

SETTING

Four university-affiliated medical centers.

PATIENTS

Forty-one patients with HIV infection who had at least two consecutive blood cultures positive for M. avium complex and who had not received previous antimycobacterial therapy were enrolled in the study. Thirty-one patients were evaluable with regard to the efficacy of the oral regimen.

INTERVENTIONS

Patients received a combination of orally administered rifampin (600 mg), ethambutol (15 mg/kg body weight), clofazimine (100 mg once daily), and ciprofloxacin (750 mg twice daily) for 12 weeks. Parenterally administered amikacin, 7.5 mg/kg daily for 4 weeks after the first 4 weeks of oral therapy, was used at the discretion of the individual investigator.

MEASUREMENTS

Clinical symptoms, Karnofsky scores, and adverse events were monitored. Colony counts for M. avium complex were determined.

MAIN RESULTS

The mean logarithmic (log) baseline colony count decreased from 2.1 to 0.7 after 4 weeks of oral therapy (P less than 0.001). Suppression of bacteremia was sustained throughout therapy. Thirteen patients (42%) became culture negative during therapy. The mean duration of treatment was 9.7 weeks. Nineteen evaluable patients (61%) completed 12 weeks of therapy. Adverse reactions to one or more agents were common.

CONCLUSIONS

A rapid reduction in symptoms and bacteremia can be achieved as early as week 2 of therapy using an oral regimen of rifampin, ethambutol, clofazimine, and ciprofloxacin. Colony counts rose dramatically after therapy was discontinued, suggesting that more prolonged periods of therapy are necessary to eradicate systemic infection.

A multicenter, double-blind, placebo-controlled trial comparing piperacillin-tazobactam with and without amikacin as empiric therapy for febrile neutropenia

In a prospective, multicenter, double-blind, randomized clinical trial, we compared the efficacy of piperacillin-tazobactam (4.5 g 3 times daily intravenously) plus placebo versus piperacillin-tazobactam plus amikacin (7.5 mg/kg twice daily intravenously) for the treatment of 760 febrile, adult patients with cancer with chemotherapy-induced profound (<500 neutrophils/mm3) and prolonged (>10 days) neutropenia. A total of 733 patients were assessable for efficacy of the drug regimens, and an overall successful outcome was reported in 49% (179 of 364) of the patients who received monotherapy, compared with 53% (196 of 369) of patients who received combination therapy (P=.2). Response rates were similar with both regimens, as were incidences of bacteremia and clinically documented and possible infections. In our epidemiological setting, the initial empiric combination therapy was not associated with improved outcomes when compared with initial monotherapy.

Visual outcomes following the use of intravitreal steroids in the treatment of postoperative endophthalmitis

OBJECTIVE

To compare visual outcomes between cases of acute postoperative endophthalmitis that did or did not receive intravitreal steroids.

DESIGN

Retrospective nonrandomized comparative trial.

PARTICIPANTS

Fifty-seven patients with postoperative endophthalmitis.

INTERVENTION

Thirty-one patients with postoperative endophthalmitis resulting from cataract extraction received both intravitreal antibiotics and steroids, whereas the remaining 26 received only intravitreal antibiotics.

MAIN OUTCOME MEASURES

Improvement in visual acuity.

RESULTS

Multivariate logistic regression was used to analyze the variables that potentially influence a three-line visual acuity improvement. The mean baseline visual acuities of both groups were comparable. The use of intravitreal steroids reduced the probability of developing a three-line improvement in visual acuity (odds ratio [OR] = 0.287; 95% confidence interval [CI] [0.072-0.852]). On the basis of logistic regression analysis using our multivariate model, gender, baseline visual acuity, and pars plana vitrectomy were not significantly associated with visual outcome differences between the two groups.

CONCLUSIONS

Patients who received intravitreal steroids had a significantly reduced likelihood of obtaining a three-line improvement in visual acuity. At a minimum our study provides no support for their use and, therefore, steroids may not be efficacious for acute endophthalmitis related to cataract extraction.

A prospective randomized study comparing once- versus twice-daily amikacin dosing in critically ill adult and paediatric patients

Three hundred and forty eight critically-ill patients with a documented Gram-negative infection were randomized to receive amikacin once- (od) or twice-daily (bd). The amikacin was given by slow intravenous injection in a daily dose of 20 mg/kg in patients under the age of one year (paediatric group) and 15 mg/kg in patients over the age of one year (adult group). Paediatric and adult patients on the od regimen received a loading dose of 25 and 20 mg/kg respectively. The dosages were subsequently adjusted to achieve desirable blood levels. Patients received other antibiotics as clinically indicated. Forty-eight patients were withdrawn from the study due to death or azotaemia occurring in the first 72 h. One hundred and fifty five patients (76 paediatric) received an od dose and 145 (65 paediatric) received a bd dose. The clinical cure rate was 83% in the od group compared to 66% in the bd group (P = 0.001). The bacteriological cure rate was 81% in the od group compared to 58% in the bd group (P = 0.005). In the paediatric sub-group the cure rate was higher with the od regimen (P = 0.002) but this difference was not statistically significant in the adult patients (P = 0.1). The serum creatinine rose in 35% of patients in the bd group compared to 21% in the od group (P = 0.05). Although audiometry was not performed there was no clinical evidence of ototoxicity in any of the patients. In conclusion od amikacin dosing resulted in a higher cure and less nephrotoxicity than conventional bd dosing.

Clinical usefulness of amikacin and doxycycline in the treatment of infection due to Mycobacterium fortuitum and Mycobacterium chelonei

The antimicrobial agents amikacin and doxycycline, which are not conventionally considered for use in treatment of mycobacterial infections, inhibit growth of Mycobacterium fortuitum and Mycobacterium chelonei in vitro. Ten patients were treated with these drugs alone or in combination with some surgical procedure. Seven of the 10 patients were definitely cured by the therapy. Only one definite treatment failure occurred. Patients with infections due to M. fortuitum or M. chelonei that are susceptible in vitro to these drugs appear to benefit from chemotherapy.

Comparative study of ototoxicity and nephrotoxicity in patients randomly assigned to treatment with amikacin or gentamicin

Fifty-four patients treated with gentamicin and 52 patients treated with amikacin were evaluated for nephrotoxicity and ototoxicity in a prospective, randomized, blinded comparative trail. According to our definition of nephrotoxicity (an increase in serum creatinine levels to at least 50 percent and 0.5 mg/dl above the baseline value), nephrotoxicity occurred in eight (15 percent) of the patients who were treated with gentamicin and none of the patients who were treated with amikacin (p = 0.006). Using several other definitions of nephrotoxicity, the differences in incidence between the treatment arms were not significant. Nephrotoxicity appeared to be associated with impaired baseline renal function, greater age, and the presence of bacteremia. Ototoxicity occurred in six (11 percent) of the 54 gentamicin-treated patients; auditory toxicity occurred in three patients, and toxic changes were observed in three of the 33 patients who could also be evaluated for vestibular toxicity. Similarly, ototoxicity was observed in seven (13 percent) of the 52 amikacin-treated patients; auditory toxicity occurred in four patients, and of the 34 patients who could also be evaluated for vestibular toxicity, three exhibited vestibular toxicity without auditory toxicity are one experienced vestibular effects in addition to those affecting the cochlea. We observed a modest association of ototoxicity with nephrotoxicity and with an elevated mean trough aminoglycoside serum level. The results of this study indicate that amikacin may be less nephrotoxic than gentamicin in humans; however, the broad applicability of this finding to other patient populations is uncertain.