Cefotaxime compared with nafcillin plus tobramycin for serious bacterial infections. A randomized, double-blind trial

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta lactam antibiotic with an aminoglycoside antibiotic may provide certain advantages over beta lactam monotherapy.

OBJECTIVES

Our objectives were to compare beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy in patients with sepsis and to estimate the rate of adverse effects with each treatment regimen, including the development of bacterial resistance to antibiotics.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11); MEDLINE (1966 to 4 November 2013); EMBASE (1980 to November 2013); LILACS (1982 to November 2013); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2013). We scanned citations of all identified studies and contacted all corresponding authors. In our previous review, we searched the databases to July 2004.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta lactam monotherapy versus any combination of a beta lactam with an aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause mortality. Secondary outcomes included treatment failure, superinfections and adverse events. Two review authors independently collected data. We pooled risk ratios (RRs) with 95% confidence intervals (CIs) using the fixed-effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 69 trials that randomly assigned 7863 participants. Twenty-two trials compared the same beta lactam in both study arms, while the remaining trials compared different beta lactams using a broader-spectrum beta lactam in the monotherapy arm. In trials comparing the same beta lactam, we observed no difference between study groups with regard to all-cause mortality (RR 0.97, 95% CI 0.73 to 1.30) and clinical failure (RR 1.11, 95% CI 0.95 to 1.29). In studies comparing different beta lactams, we observed a trend for benefit with monotherapy for all-cause mortality (RR 0.85, 95% CI 0.71 to 1.01) and a significant advantage for clinical failure (RR 0.75, 95% CI 0.67 to 0.84). No significant disparities emerged from subgroup and sensitivity analyses, including assessment of participants with Gram-negative infection. The subgroup of Pseudomonas aeruginosa infections was underpowered to examine effects. Results for mortality were classified as low quality of evidence mainly as the result of imprecision. Results for failure were classified as very low quality of evidence because of indirectness of the outcome and possible detection bias in non-blinded trials. We detected no differences in the rate of development of resistance. Nephrotoxicity was significantly less frequent with monotherapy (RR 0.30, 95% CI 0.23 to 0.39). We found no heterogeneity for all these comparisons.We included a small subset of studies addressing participants with Gram-positive infection, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta lactams for sepsis should be discouraged. All-cause mortality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta-lactam antibiotic with an aminoglycoside antibiotic may have certain advantages over beta-lactam monotherapy.

OBJECTIVES

We compared clinical outcomes for beta lactam-aminoglycoside combination therapy versus beta lactam monotherapy for sepsis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, Issue 3, 2004); MEDLINE (1966 to July 2004); EMBASE (1980 to March 2003); LILACS (1982 to July 2004); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2003). We scanned citations of all identified studies and contacted all corresponding authors.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta-lactam monotherapy to any combination of one beta-lactam and one aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause fatality. Secondary outcomes included treatment failure, superinfections, colonization, and adverse events. Two authors independently collected data. We pooled relative risks (RR) with their 95% confidence intervals (CI) using the fixed effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 64 trials, randomizing 7586 patients. Twenty trials compared the same beta-lactam in both study arms, while the remaining compared different beta-lactams using a broader spectrum beta-lactam in the monotherapy arm. In studies comparing the same beta-lactam, we observed no difference between study groups with regard to all-cause fatality, RR 1.01 (95% CI 0.75-1.35) and clinical failure, RR 1.11 (95% CI 0.95-1.29). In studies comparing different beta-lactams, we observed an advantage to monotherapy: all cause fatality RR 0.85 (95% CI 0.71-1.01), clinical failure RR 0.77 (95% CI 0.69-0.86). No significant disparities emerged from subgroup and sensitivity analyses, including the assessment of patients with Gram-negative and Pseudomonas aeruginosa infections. We detected no differences in the rate of resistance development. Adverse events rates did not differ significantly between the study groups overall, although nephrotoxicity was significantly more frequent with combination therapy, RR 0.30 (95% CI 0.23-0.39). We found no heterogeneity for all comparisons. We included a small subset of studies addressing patients with Gram-positive infections, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta-lactams for sepsis should be discouraged. All-cause fatality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Effect of Aminoglycoside and β‐Lactam Combination Therapy versus β‐Lactam Monotherapy on the Emergence of Antimicrobial Resistance: A Meta‐analysis of Randomized, Controlled Trials

BACKGROUND

The addition of an aminoglycoside to a beta -lactam therapy regimen has been suggested to have a beneficial effect in delaying or preventing the development of antimicrobial resistance. We studied the effect of aminoglycoside/ beta -lactam combination therapy versus beta-lactam monotherapy on the emergence of resistance.

METHODS

We performed a meta-analysis of randomized, controlled trials (RCTs) that compared aminoglycoside/ beta-lactam combination therapy with beta-lactam monotherapy and that reported data regarding the emergence of resistance (primary outcome) and/or development of superinfection, treatment failure, treatment failure attributable to emergence of resistance, treatment failure attributable to superinfection, all-cause mortality during treatment, and mortality due to infection. Data for this meta-analysis were identified from the PubMed database, Current Contents database, Cochrane central register of controlled trials, and references in relevant articles.

RESULTS

A total of 8 RCTs were included in the analysis. Beta -lactam monotherapy was not associated with a greater emergence of resistance than was the aminoglycoside/ beta-lactam combination (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.56-1.47). Actually, beta -lactam monotherapy was associated with fewer superinfections (OR, 0.62; 95% CI, 0.42-0.93) and fewer treatment failures (OR, 0.62; 95% CI, 0.38-1.01). Rates of treatment failure attributable to emergence of resistance (OR, 3.09; 95% CI, 0.75-12.82), treatment failure attributable to superinfection (OR, 0.60; 95% CI, 0.33-1.10), all-cause mortality during treatment (OR, 0.70; 95% CI, 0.40-1.25), and mortality due to infection (OR, 0.74; 95% CI, 0.46-1.21) did not differ significantly between the 2 regimens.

CONCLUSIONS

Compared with beta-lactam monotherapy, the aminoglycoside/ beta-lactam combination was not associated with a beneficial effect on the development of antimicrobial resistance among initially antimicrobial-susceptible isolates.

Antibiotic regimens for secondary peritonitis of gastrointestinal origin in adults

BACKGROUND

Secondary peritonitis is associated with a high mortality rate and if not treated successfully leads to development of abscesses, severe sepsis and multi-organ failure. Source control and adjunctive antibiotics are the mainstay of treatment. However, no conclusive evidence suggest that one antibiotic regimen is better than any other but at the same time have a lower toxicity.

OBJECTIVES

To ascertain the efficacy and adverse effects of different antibiotic regimens in treating intra-abdominal infections in adults. Outcomes were divided into primary (clinical success and effectiveness in reducing mortality) and secondary (microbiological success, preventing wound infection, intra-abdominal abscess, clinical sepsis, remote infection, superinfection, adverse reactions, duration of treatment required, effectiveness in reducing hospitalised stay, and time to defervescence).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, Issue 4, 2004), MEDLINE (from 1966 to November 2004), EMBASE (from 1980 to November 2004) and Cochrane Colorectal Cancer Group specialised register SR-COLOCA. Bibliographies of identified studies were screened for further relevant trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing different antibiotic regimens in the treatment of secondary peritonitis in adults were selected. Trials reporting gynaecological or traumatic peritonitis were excluded from this review. Ambiguity regarding suitability of trials were discussed among the review team.

DATA COLLECTION AND ANALYSIS

Six reviewers independently assessed trial quality and extracted data. Data collection was standardised using data collection form to ensure uniformity among reviewers. Statistical analyses were performed using the random effects model and the results expressed as odds ratio for dichotomous outcomes, or weight mean difference for continuous data with 95% confidence intervals.

MAIN RESULTS

Fourty studies with 5094 patients met the inclusion criteria. Sixteen different comparative antibiotic regimens were reported. All antibiotics showed equivocal comparability in terms of clinical success. Mortality did not differ between the regimens. Despite the potential high toxicity profile of regimens using aminoglycosides, this was not demonstrated in this review. The reason for this could be the inherent bias within clinical trials in the form of patient selection and stringency in monitoring drug levels.

AUTHORS' CONCLUSIONS

No specific recommendations can be made for the first line treatment of secondary peritonitis in adults with antibiotics, as all regimens showed equivocal efficacy. Other factors such as local guidelines and preferences, ease of administration, costs and availability must therefore be taken into consideration in deciding the antibiotic regimen of choice. Future trials should attempt to stratify patients and perform intention-to-treat analysis to allow better external validity.

Application of Bayes theorem to aminoglycoside-associated nephrotoxicity: comparison of extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing

The objective of this study was to examine the incidence of aminoglycoside-associated nephrotoxicity related to extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing by applying Bayes theorem. An electronic literature search of MEDLINE (1966-2003) and a manual search of references from published meta-analyses and review articles were performed. Studies using extended-interval dosing, individualized pharmacokinetic monitoring, or multiple-daily dosing and reported aminoglycoside-associated nephrotoxicity for patients > or = 16 years of age were included. Quality scores were assigned based on the rigor of definition of aminoglycoside-associated nephrotoxicity, duration of therapy, and length of follow-up of renal function after completion of therapy. Inclusion criteria were then based on these quality scores. Quantitative data on the incidence of aminoglycoside-associated nephrotoxicity were abstracted. Twelve extended-interval dosing studies (n = 916), 10 individualized pharmacokinetic monitoring studies (n = 2066), and 27 multiple-daily dosing studies (n = 4251) met the inclusion criteria. Prior probabilities of aminoglycoside-associated nephrotoxicity were derived from a combination of a review of published studies and expert judgment. The maximum densities for the final posterior probabilities of aminoglycoside-associated nephrotoxicity for extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing were located at 12% to 13%, 10% to 11%, and 13% to 14%, respectively. Application of Bayes theorem demonstrates that aminoglycoside dosing by individualized pharmacokinetic monitoring results in less aminoglycoside-associated nephrotoxicity than extended-interval dosing or multiple-daily dosing.

Beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy for sepsis in immunocompetent patients: systematic review and meta-analysis of randomised trials

OBJECTIVE

To compare beta lactam monotherapy with beta lactam-aminoglycoside combination therapy for severe infections.

DATA SOURCES

Medline, Embase, Lilacs, Cochrane Library, and conference proceedings, to 2003; references of included studies; contact with all authors. No restrictions, such as language, year of publication, or publication status.

STUDY SELECTION

All randomised trials of beta lactam monotherapy compared with beta lactam-aminoglycoside combination therapy for patients without neutropenia who fulfilled criteria for sepsis.

DATA SELECTION

Two reviewers independently applied selection criteria, performed quality assessment, and extracted the data. The primary outcome assessed was all cause fatality by intention to treat. Relative risks were pooled with the random effect model (relative risk < 1 favours monotherapy).

RESULTS

64 trials with 7586 patients were included. There was no difference in all cause fatality (relative risk 0.90, 95% confidence interval 0.77 to 1.06). 12 studies compared the same beta lactam (1.02, 0.76 to 1.38), and 31 studies compared different beta lactams (0.85, 0.69 to 1.05). Clinical failure was more common with combination treatment overall (0.87, 0.78 to 0.97) and among studies comparing different beta lactams (0.76, 0.68 to 0.86). There was no advantage to combination therapy among patients with Gram negative infections (1835 patients) or Pseudomonas aeruginosa infections (426 patients). There was no difference in the rate of development of resistance. Nephrotoxicity was significantly more common with combination therapy (0.36, 0.28 to 0.47). Heterogeneity was not significant for these comparisons.

CONCLUSIONS

In the treatment of sepsis the addition of an aminoglycoside to beta lactams should be discouraged. Fatality remains unchanged, while the risk for adverse events is increased.

Short-term effectiveness of ceftriaxone single dose in the initial treatment of acute uncomplicated pyelonephritis in women. A randomised controlled trial

OBJECTIVE

To compare the short-term effectiveness of ceftriaxone single dose followed by cefixime with a standard treatment of acute uncomplicated pyelonephritis in women.

METHODS

An open, prospective, and randomised trial of women with acute uncomplicated pyelonephritis was performed. Group A were given a daily intravenous dose of 1 g ceftriaxone; group B: ceftriaxone 1 g intravenous single dose followed by oral cefixime. When urine culture was received, both groups completed a 10 day treatment based in sensitivity studies. Only women with positive initial urine culture were included. After three days of treatment, clinical and bacteriological efficacy was assessed. Clinical response was classified as "cured" if acute symptoms (fever, urinary syndrome and flank pain) were settled. Bacteriological response was classified as: eradication, or no eradication.

RESULTS

Of 144 eligible patients, urine culture was positive in 54 of 72 (75%) women in group A and 51 of 72 (71%) in group B. There were no significant differences between groups in resolution of acute symptoms. Clinical cure was observed in 49 of 54 (91%) patients in the group A and in 47 of 51 (92%) patients in the group B (p = 0.68). After three days of treatment urine culture was negative for all patients. No adverse effects were observed in either of the groups.

CONCLUSION

These data suggest that a intravenous single dose of ceftriaxone followed by oral cefixime is both effective and safe for the initial treatment of acute uncomplicated pyelonephritis in women. This regimen could be useful in managing selected patients with pyelonephritis as outpatients.

Gentamicin for the practicing urologist: review of efficacy, single daily dosing and "switch" therapy

PURPOSE

We review the literature on gentamicin, including single daily dosing and "switch" therapy.

MATERIALS AND METHODS

We used MEDLINE to search the literature from 1966 to June 1997, and then manually searched bibliographies to identify studies that our initial search might have missed.

RESULTS

Gentamicin has attractive characteristics, including wide spectrum, infrequent resistance, economy and familiarity. Although limited by well known toxicities, gentamicin remains a drug of choice for serious Gram-negative infections. Dosing strategies, such as single daily dosing and switch therapy, have renewed enthusiasm for this time-honored drug.

CONCLUSIONS

Gentamicin remains a valuable drug in urology. Once daily dosing and switch therapy offer the potential to increase effectiveness and convenience while decreasing toxicity and costs.

Aminoglycosides

Despite their nephrotoxic and ototoxic side effects, AG remain useful antibiotics because of their major, rapid, and dose-dependent bactericidal effects. Combination therapy with an AG appears particularly important in neutropenic and other high-risk patients to provide broad-spectrum bactericidal activity, synergism, and reduction of emergence of resistant pathogens. OD AG therapy is associated with high peak levels in serum that maintain efficacy and low-to-undetectable trough levels in serum that attenuate the risk of toxicity. Administration of short-term OD AG therapy to patients not at risk without renal impairment may not absolutely require dosing monitoring. This therapeutic strategy has been proved useful in clinical trials, now including febrile episodes in neutropenic patients, but it should be avoided during infections in which antimicrobial synergism is required, such as enterococcal endocarditis.

Review and reassessment of dosing schedules for cefotaxime in selected medical indications

Cefotaxime, the first widely used "third-generation" cephalosporin, has established efficacy against a variety of serious bacterial pathogens. Some of the initial clinical studies in the United States using this agent employed large doses of the compound, up to 12 g/day, for adults. In contrast, however, initial European studies were largely with low doses of 1 to 2 g every 12 h. In the recent past, however, an effort has been made, both in the United States and in Europe to reevaluate the dosage of cefotaxime. In various clinical studies, lower doses of cefotaxime have been successfully employed for infections of the urinary tract, peritoneum, biliary tract, lung, and skin and soft tissues. The results of a number of these studies will be reviewed, including a large postmarketing surveillance study carried out in Germany during 1992. The results suggest that cefotaxime doses as low as 1 g, at intervals as long as every 12 h, can be adequate for treatment of the most commonly encountered infections, such as those caused by some hemolytic streptococci, Staphylococcus aureus, Haemophilus spp., and enteric bacilli in nonimmunocompromised patients.

Retrospective analysis of the clinical and economic outcomes of twice-daily dosing of cefotaxime in a Canadian tertiary care institution

A retrospective analysis of the clinical and economic outcome of a regimen of cefotaxime 1 g given every 12 h was conducted following the introduction of an institutional policy recommending this new dosing strategy. Patients were identified from a log order entry in the pharmacy, and the medical records were reviewed using a standardized data collection form. Explicit criteria were applied for the indications for antimicrobial therapy, presence of infection, and outcome parameters. A total of 60 patients with a mean (+/- SD) age of 56.2 (+/- 17.8) years and a mean (+/- SD) length of stay of 20.75 (+/- 18.1) days were identified. Of these, 48 (80%) were found to have a clinically or microbiologically documented infection, and of the 42 patients who could be assessed accordingly to the criteria chosen, 37 (88%) had a favorable clinical response; 21 patients (35%) received cefotaxime alone. The costs for administration of cefotaxime have decreased by approximately 30% since the introduction of this new dosing regimen.

Cefepime compared with ceftazidime as initial therapy for serious bacterial infections and sepsis syndrome

In an open randomized multicenter comparative study, we evaluated the safety and efficacy of cefepime (CP; 2.0 g given intravenously every 12 h) and ceftazidime (CZ; 2.0 g given intravenously every 8 h) as initial treatment for adult patients with suspected serious bacterial infections. A total of 133 patients entered the study, of whom 114 were evaluable for clinical and microbiological response assessment: 56 received CP and 58 received CZ. About 50% (30 who received CP and 25 who received CZ) fulfilled the criteria of the sepsis syndrome. The treatment groups were comparable with respect to sex distribution, mean age, underlying diseases, treatment duration, APACHE II score, and type of infection. The most commonly cultured microorganisms were members of the family Enterobacteriaceae, Streptococcus pneumoniae, and Staphylococcus aureus. The causative microorganisms were eradicated from 92% (37 of 40) of patients with a microbiologically documented infection who underwent treatment with CP; they were eradicated from 86% (42 to 49) of patients who received CZ. The responses of only clinically documented infections in the CP group were 90% (27 of 30 patients); in the CZ group they were 87% (26 of 30 patients). When patients fulfilled the criteria of the sepsis syndrome (septic shock excluded), the causative microorganisms were eradicated from 89% (16 of 18) of CP-treated patients and 86% (12 of 14) of CZ-treated patients. None of these differences was statistically significant. Mortality was the same in both groups (four patients in each group) and was not attributable to the study medication. In conclusion, CP is at least as effective and as safe as CZ, as initial antimicrobial therapy for suspected serious bacterial infections in nonneutropenic patients with or without the sepsis syndrome. CP has the additional advantage in that it can be given twice daily, which may lead to a decrease in hospital costs.

Once versus thrice daily gentamicin in patients with serious infections

Aminoglycosides are usually given in two or three divided doses. A once-daily regimen might be more effective and less toxic. We have conducted a randomised trial in consecutive patients with serious infections for whom an aminoglycoside seemed warranted. Exclusion criteria were neutropenia or severely impaired renal function. 123 patients were enrolled. For efficacy analysis only those patients were considered in whom treatment with the aminoglycoside was not stopped within 72 h (n = 67); toxicity was analysed on patients receiving aminoglycosides for more than 48 h and not using other nephrotoxic medication (n = 85). Gentamicin 4 mg/kg every day (OD) or gentamicin 1.33 mg/kg three times daily (MD) (with dose-reduction in case of renal dysfunction) were given intravenously. In almost all patients intravenous amoxycillin 1 g every 6 h was also started. Baseline characteristics were comparable in both arms. A good clinical response was observed in 32/35 (91%) of the OD and in 25/32 (78%) in the MD group (difference 13%, 95% confidence interval -6.4% to +26.9%). 2 patients in each group died with uncontrolled infection. An insufficient bacteriological response (persistent positive cultures, resistance, or superinfection) was observed in 2 patients with OD and 3 patients with MD. In patients treated for more than 48 h duration of therapy and mean doses were 7.0 days (1590 mg) and 7.4 days (1672 mg) in OD and MD respectively. Mean first serum trough/peak levels were 0.6/10.2 mg/L and 1.4/5.2 mg/L. Nephrotoxicity (a rise in serum creatinine of 45 mumol/L or more) developed in 2/40 (5%) in OD and 11/45 (24%) in MD (p = 0.016). Risk factors for nephrotoxicity were duration of therapy and baseline creatinine clearance rate. High-tone audiometry was performed when possible; no significant differences were found in hearing loss (3/12 and 3/11) or prodromal signs of ototoxicity (5/12 and 4/11). A once-daily dosing regimen of gentamicin is at least as effective as and is less nephrotoxic than more frequent dosing.

Evaluation of clinical judgment in the identification and treatment of nosocomial pneumonia in ventilated patients

To evaluate the accuracy of clinical judgment in the diagnosis and treatment of nosocomial pneumonia in ventilated patients, we studied 84 patients suspected of having nosocomial pneumonia because of the presence of a new pulmonary infiltrate and purulent tracheal secretions. We prospectively evaluated the accuracy of diagnostic predictions and therapeutic plans independently formulated by a team of physicians aware of all clinical, radiologic and laboratory data, including the results of Gram-stained bronchial aspirates. Definite (n = 51) or probable (n = 33) diagnoses could be established in all patients by strict histopathologic and/or bacteriologic criteria. Only 27/84 patients were diagnosed as having pneumonia. Organisms responsible for pneumonias were identified by quantitative cultures of samples obtained using a protected specimen brush or pleural fluid cultures. Four hundred eight predictions were made for the 84 studied patients. Clinical diagnoses for patients subsequently diagnosed as having pneumonia were accurate in 81/131 cases (62 percent). Furthermore, only 43/131 (33 percent) therapeutic plans proposed for these patients represented effective therapy. Common causes of inappropriate treatment included failure to diagnose pneumonia (50 plans), failure to effectively treat highly resistant organisms (21 plans), and failure to treat all organisms in cases of polymicrobial pneumonia (14 plans). Therapeutic plans formulated for patients without pneumonia included the unnecessary use of antibiotics in 45/277 cases (16 percent). These findings indicate that the use of clinical criteria alone does not permit the accurate diagnosis of nosocomial pneumonia in ventilated patients, and commonly results in inappropriate or inadequate antibiotic therapy for these patients.

Ceftriaxone versus latamoxef in febrile neutropenic patients: empirical monotherapy in patients with solid tumours

121 patients with 132 febrile episodes were randomised to ceftriaxone or latamoxef monotherapy in order to compare antibiotic efficacy in neutropenic patients treated with cytotoxic chemotherapy for solid tumours. In 80 evaluable episodes no significant differences were observed between the two groups with respect to efficacy and fatal failure rates. Of episodes treated with ceftriaxone, 67% showed a favourable clinical response vs. 61% in the latamoxef group. The clinical response rates in episodes with documented bacterial infections were 67 and 56% in the two treatment groups. In 18% of the episodes with documented initial infections the patients died of presumably uncontrolled infection. The convenient once daily dosage schedule combined with fewer severe adverse reactions favours the use of ceftriaxone instead of latamoxef. Although a relative high degree of response was seen, empirical antibiotic monotherapy apparently does not offer a sufficient antibacterial cover in infections in this type of patient with defective host immunity.

Cost effectiveness of once-daily oral antimicrobial therapy

Once daily dosing of oral antimicrobials achieves significantly better patient compliance than three or four times daily dosing, and limited data suggest that this is associated with greater efficacy. Comparison of once daily and twice daily dosing is less consistent, and most studies show only marginally better compliance with once daily dosing versus twice daily dosing. Detection of urinary antimicrobial activity provides a simple method for checking compliance with oral antimicrobials and deserves wider study. Counts of residual tablets have been shown to overestimate compliance. Intravenous formulations are always more expensive than equivalent oral formulations, and preparation and administration of intravenous drugs adds significant additional costs. Moreover, intravenous regimens are complex, and a number of studies have shown that serious errors occur in both preparation and administration of intravenous drugs. There is increasing evidence that serious infections can be adequately treated with oral drugs, and the excellent bioavailability of quinolones makes them particularly attractive for these indications. Clinicians require a method for checking absorption by patients with severe infection, and the Serum Bactericidal Test may provide a practical method for monitoring a wide variety of drugs.

Evaluating the cost-effectiveness of treatment with third-generation cephalosporins

Spreadsheet computer software was used to compare the estimated global treatment costs of the third-generation cephalosporins, cefotaxime and ceftriaxone, in the management of pneumonia using treatment schedules taken from current studies. Included in the analysis were not only acquisition costs, but also costs that contribute to total expenses for a course of treatment, such as those of (a) preparation and administration (disposable supplies, nursing, and pharmacy time), (b) projected laboratory costs to monitor for hypoprothrombinemia, and (c) complication costs (diarrhea, superinfection, pseudocholelithiasis, and so on). The cost analysis was performed using United States trial-derived factors. Where published cost factors were not available, reasonable estimates were sought. Our analysis indicates that cefotaxime therapy may be less costly than ceftriaxone therapy in the dosage schedules used in these clinical studies and routine clinical practice.

Mild ischemia predisposes the S3 segment to gentamicin toxicity

The purpose of these studies was to determine if a functionally insignificant ischemic insult, occurring prior to gentamicin administration, enhanced gentamicin nephrotoxicity. Bilateral renal pedicle clamp studies demonstrated that 15 minutes of ischemia did not increase the plasma creatinine yet markedly enhanced gentamicin nephrotoxicity. Further studies, in uninephrectomized rats, demonstrated that following fifteen minutes of renal ischemia and four hours of reperfusion inulin clearance, FENa+ and cellular morphology were normal. This model, therefore, was used in all subsequent studies. While the plasma creatinine concentrations were normal 24 hours following 15 minutes of ischemia and only slightly increased following gentamicin administration (100 mg/kg, i.p.) gentamicin administered four hours following 15 minutes of renal ischemia resulted in significantly increased 24-hour plasma creatinine values. Light microscopic quantitation of tissue injury, performed 24 hours following experimental manipulation, was notable for S3 segment damage in the ischemia plus gentamicin group. This was not observed in either the ischemia group or the sham operated gentamicin group. Cortical gentamicin levels were elevated in the ischemia plus gentamicin group, despite similar plasma gentamicin half-lives. However, the elevation in cortical gentamicin levels was dissociated from the enhanced nephrotoxicity seen following mild ischemic injury. Taken together these data indicate that mild renal ischemia, occurring prior to gentamicin administration, greatly enhanced gentamicin nephrotoxicity with the greatest damage occurring to S3 cells.

Third generation cephalosporins: safety profiles after 10 years of clinical use

Compared with aminoglycosides, chloramphenicol, sulfonamides, tetracyclines, and even penicillins, the cephalosporins represent a remarkably safe class of antibiotics. Among the cephalosporins, the extended spectrum, third generation agents developed generally produce few side effects and appear to be less allergenic than the penicillins. Nephrotoxicity has not been a problem at recommended doses. Some third generation agents can cause hypoprothrombinemia if not administered with vitamin K, and disulfiram-like reactions occur with some agents because of the presence of a thiomethyl tetruzole moiety affixed to the cephem nucleus. There is a greater incidence of diarrhea associated with the agents excreted through a primarily biliary route, and this may contribute to the selection of drug resistant bacteria. Some agents are less active against staphylococci and their use may result in an increased incidence of superinfection or overgrowth of enterococci. If attention is given to the potential for adverse effects, many of these problems can be avoided and the third generation cephalosporins can be used safely in hospitals, nursing homes, and home care settings.

A team approach to reduce antibiotic costs

After partial success in reducing antibiotic drug costs by traditional methods (i.e., closed formulary, use of generic drugs, retrospective drug usage review, continuing education), a study of a new "team approach" was implemented. The study involved a clinical pharmacist and physicians working together to select the most appropriate antibiotic therapy. The clinical pharmacist reviewed the culture and sensitivity data and the pattern of infectious disease over the six-month period prior to the initiation of the study and prepared a list of the most appropriate antibiotics based on clinical efficacy and cost effectiveness. He then joined the physicians on morning rounds to monitor therapy and help in the selection of the most appropriate drug regimen. At the end of the study period, antibiotic cost savings of 58.6 percent were achieved.

Discovery and development of new antimicrobial agents

The unprecedented growth in the number of new antibiotics over the past two decades has been the result of extensive research efforts that have exploited the growing body of knowledge describing the interactions of antibiotics with their targets in bacterial cells. Information gained from one class of antimicrobial agents has often been used to advance the development of other classes. In the case of beta-lactams, information on structure-activity relationships gleaned from penicillins and cephalosporins was rapidly applied to the cephamycins, monobactams, penems, and carbapenems in order to discover broad-spectrum agents with markedly improved potency. These efforts have led to the introduction of many new antibiotics that demonstrate outstanding clinical efficacy and improved pharmacokinetics in humans. The current review discusses those factors that have influenced the rapid proliferation of new antimicrobial agents, including the discovery of new lead structures from natural products and the impact of bacterial resistance development in the clinical setting. The development process for a new antibiotic is discussed in detail, from the stage of early safety testing in animals through phase I, II, and III clinical trials.

Antimicrobial agents: the old and the new

Although there are many new antimicrobial agents, many of the old antibiotics are still useful in the treatment of infections, particularly those in the community. Antimicrobial resistance patterns and special pharmacologic properties should influence the selection of newer antimicrobial agents. Change from parenteral therapy to oral therapy should increase to avoid the complications of intravenous therapy and to reduce hospital costs. Older antibiotics that are less costly should be used when the etiology and susceptibility of infecting pathogens are known. There will continue to be new antibiotics produced. Understanding the microbiologic and pharmacologic advantages of the new agents compared with older agents is essential if the new agents are to be used properly and not destroyed by inappropriate use.

Comparative study of three different dosing regimens of cefotaxime for treatment of gram-negative bacteremia

Thirty-one patients with Gram-negative bacteremia with organisms susceptible to cefotaxime (CTX) (MIC of 1 microgram/ml or less) were randomized to receive 2 g of CTX every 6, 8, or 12 hr. Five-hour susceptibility studies were performed on a bacterial pellet obtained from the patient's positive blood culture vial. Thus, patients were enrolled within hours after Gram-negative organisms were demonstrated in their blood cultures. All bacteremias were cleared although two patients had unsatisfactory responses to therapy. Trough serum bactericidal levels were 1:2 or greater in all patients. This study supports that CTX can be used at an 8- or 12-hr intervals in selected patients with Gram-negative bacteremia.

Evaluation of cefotaxime alone and in combination with desacetylcefotaxime against strains of Staphylococcus aureus that produce variants of staphylococcal beta-lactamase

We evaluated cefotaxime (CTX) alone and in combination with its metabolite, desacetylcefotaxime (dCTX) against strains of Staphylococcus aureus that produce the four recognized variants of staphylococcal beta-lactamase and a beta-lactamase-producing isolate characterized by the expression of borderline resistance to methicillin. Although macrodilution MICs revealed that dCTX was less active than CTX against these strains (geometric means of 16 micrograms/ml and 4 micrograms/ml, respectively), the addition of clinically achievable concentrations of dCTX to CTX resulted in a reduction in the observed CTX MICs. This effect was similar to although less pronounced than that obtained by combining clavulanic acid with cefazolin. The increased antistaphylococcal activity noted by MIC determinations was confirmed with kill-kinetic studies. Determination of the relative rates of hydrolysis of selected cephalosporins showed that neither CTX nor dCTX were appreciably hydrolyzed by the variant staphylococcal enzymes. Evaluation of the effect of CTX and dCTX upon the staphylococcal beta-lactamases demonstrated that neither agent inhibited the destruction of a 100 microM solution of nitrocefin, although the reduction of CTX and cefazolin MICs by low concentrations of dCTX suggests that the dCTX metabolite may act as a competitive inhibitor of beta-lactamase. These observations may explain the previously demonstrated clinical efficacy of CTX used alone for the treatment of serious infections caused by S. aureus.

Aminoglycosides: current role in antimicrobial therapy

Aminoglycosides remain the cornerstone of antibiotic therapy for nosocomial, gram-negative bacillary infections despite the recent introduction of broad-spectrum beta-lactam antibiotics and quinolones with antipseudomonal activity. Initially, aminoglycosides were used as antiaerobic gram-negative antimicrobial therapy. Currently, they have a key role in many types of infections, such as gram-negative urosepsis and in febrile granulocytopenic patients, because of their established antipseudomonal activity. Empiric treatment of febrile episodes in granulocytopenic cancer patients with an aminoglycoside, in combination with an anti-pseudomonal beta-lactam, accounts for much of the aminoglycoside use. Amikacin is emerging as one of the most effective aminoglycosides on the basis of resistance rates, pharmacokinetic factors likely to affect clinical efficacy, safety, and overall cost of therapy.

Comparison of once daily ceftriaxone with gentamicin plus cefuroxime for treatment of serious bacterial infections

To compare the efficacy of once daily monotherapy with that of standard combination antibiotic therapy for the initial management of patients suspected of serious bacterial infections, 105 patients were randomised to treatment with ceftriaxone alone (53 patients) or to a combination of cefuroxime and gentamicin (52 patients). There was no difference between the groups in proportions responding to therapy or proportions dying from infection, except when non-evaluable patients were excluded from the group with definite bacterial infection, in which case response was better among those treated with ceftriaxone. The groups did not differ in number of side-effects, but therapy had to be discontinued because of treatment failure, an adverse effect, or death in 1 of 53 patients given ceftriaxone and in 11 of 34 given the combination. Use of ceftriaxone was 107.36 pounds ($182.51) cheaper per patient, and saved 40 minutes of nursing and drug administration time per patient per day. Thus 2 g ceftriaxone given once a day is at least as effective and costs less in time and money than gentamicin plus cefuroxime for the initial treatment of patients with serious systemic bacterial infections.

Recent advances in the treatment of pneumonia in the intensive care unit

The treatment of pneumonia acquired in the intensive care unit (ICU) includes intravenous antibiotics and supportive care. In many cases, the aetiologic agent of infection is not clear and empirical broad-spectrum antibiotic regimens are commonly used. Combinations of beta-lactam and aminoglycoside agents are particularly popular due to the high incidence of Gram-negative bacillary and Staphylococcus aureus pneumonias in the hospital setting. Several new approaches to treatment of pneumonia in the ICU are currently being evaluated including single-agent empirical treatment with broad-spectrum beta-lactam agents; intrabronchial aminoglycoside instillation therapy; oral quinolone agents for treatment of Gram-negative bacillary pneumonia; and passive immune therapy. Conventional and experimental therapy are discussed in this report.

Bactericidal activity of ciprofloxacin compared with that of cefotaxime in normal volunteers

We compared ciprofloxacin (200 mg) with cefotaxime (2 g) when each was administered intravenously over a 30-min period to six volunteers in a crossover manner 1 week apart. To integrate the pharmacologic and microbiologic activity, inhibitory and bactericidal activities in serum were obtained for both antibiotics 1 and 6 h after administration against 10 strains of Escherichia coli, 10 strains of Klebsiella pneumoniae, 15 strains of Pseudomonas aeruginosa, and 10 strains each of methicillin-susceptible and -resistant Staphylococcus aureus. Geometric mean bactericidal titers for E. coli 1 h after the infusion were 1:60 for ciprofloxacin and 1:252 for cefotaxime, and for K. pneumoniae they were 1:20 and 1:256, respectively. However, geometric mean titers were poor for both antibiotics against methicillin-susceptible S. aureus (less than 1:2 for ciprofloxacin versus 1:5 for cefotaxime) and methicillin-resistant S. aureus (less than 1:2 for both antibiotics), as well as against P. aeruginosa (1:3 for ciprofloxacin versus 1:2 for cefotaxime). These data suggest that ciprofloxacin may be useful for the treatment of serious infections caused by E. coli and K. pneumoniae. However, caution is suggested when this dose of ciprofloxacin is used in situations in which septicemia is caused by P. aeruginosa or S. aureus and originates outside the urinary tract.

Studies of risk factors for aminoglycoside nephrotoxicity

The epidemiology of aminoglycoside-induced nephrotoxicity is not fully understood. Experimental studies in healthy human volunteers indicate aminoglycosides cause proximal tubular damage in most patients, but rarely, if ever, cause glomerular or tubular dysfunction. Clinical trials of aminoglycosides in seriously ill patients indicate that the relative risk for developing acute renal failure during therapy ranges from 8 to 10 and that the attributable risk is 70% to 80%. Further analysis of these data suggests that the duration of therapy, plasma aminoglycoside levels, liver disease, advanced age, high initial estimated creatinine clearance and, possibly, female gender all increase the risk for nephrotoxicity. Other causes of acute renal failure, such as shock, appear to have an additive effect. Predictive models have been developed from these analyses that should be useful for identifying patients at high risk. These models may also be useful in developing insights into the pathophysiology of aminoglycoside-induced nephrotoxicity.

Cefsulodin treatment for serious Pseudomonas aeruginosa infections

Cefsulodin, a narrow-spectrum cephalosporin with excellent antipseudomonal activity was used to treat 48 patients with 51 Pseudomonas aeruginosa infections. These included osteomyelitis, infected prostheses, post-operative and post-traumatic superficial wounds, decubitus and stasis ulcers, lower respiratory tract infections and infections of the urinary tract. Many of the patients were compromised by underlying debilitating conditions such as severe trauma, diabetes mellitus, vascular impairment, and abuse of alcohol and drugs. In cases of polymicrobial infections, a concomitant non-antipseudomonal antibiotic was sometimes administered. Cefsulodin was administered intravenously to 47 patients and by intramuscular injections to one individual. The dosage ranged from 0.5 to 2.0 g every six hr and duration of therapy was from 4 to 70 days. A satisfactory clinical response was observed in 88% of the patients. P. aeruginosa was eradicated from 76% of the infection sites. Failures, which included relapse within one year, were generally associated with prior severe trauma or vascular impairment in cases of osteomyelitis. Reinfections and superinfections developed in 12 individuals. Adverse reactions reported for two patients were nausea and vomiting. A third patient had transient increases in alkaline phosphatase and SGOT. These data indicate that cefsulodin is an effective and safe antibiotic in various types of P. aeruginosa infections.

Double-blind, prospective, multicenter trial comparing ceftazidime with moxalactam in the treatment of serious gram-negative infections

Ceftazidime is a new antimicrobial agent possessing excellent in vitro activity against most members of the family Enterobacteriaceae and against Pseudomonas aeruginosa. We conducted a double-blind, prospective, multicenter trial to compare ceftazidime with moxalactam in the treatment of serious gram-negative infections. The overall favorable response rates for the two regimens were similar (93 of 106 [88%] and 84 of 97 [86%], respectively). Among these, the response rates of the 56 gram-negative bacteremias and the 23 P. aeruginosa infections were comparable. Both groups had similar incidences of subsequent infections with P. aeruginosa, enterococci, and yeasts. A total of 13% of the patients in the moxalactam group developed a prolonged prothrombin time (P less than 0.01), and three patients demonstrated clinical bleeding. These results suggest that although the overall efficacy of both regimens was similar, treatment with moxalactam resulted in a higher incidence of prolongation of prothrombin time with an attendant risk of bleeding. In nonneutropenic patients, ceftazidime as a single agent is safe and effective in gram-negative bacillary infections.

Risk factors and comparisons of clinical nephrotoxicity of aminoglycosides

Controversy continues regarding risk factors for nephrotoxicity and the possible differences in nephrotoxicity rates associated with the aminoglycosides commonly used in clinical practice. Review of published data, including 27 comparative clinical studies, indicates the following: sensitive markers of tubular toxicity do not correlate directly with clinically significant diminution in glomerular filtration rate; of all the proposed risk factors, few are consistently found; despite numerous studies, some with potential drawbacks, no current aminoglycoside has been shown to be consistently and conclusively less nephrotoxic than another; and, as per a previous recommendation, the choice of an aminoglycoside should not be made on the basis of nephrologic criteria.

Increased risk of renal dysfunction due to interaction of liver disease and aminoglycosides

To determine if aminoglycoside use and liver disease interact to cause an increased risk for renal dysfunction, data from 179 hospitalized patients who had been enrolled in a prospective, randomized trial of nafcillin/tobramycin versus cefotaxime were analyzed. The cefotaxime-treated patients served as a control group not receiving an aminoglycoside. Renal dysfunction occurred in seven of 88 (8 percent) given cefotaxime and 37 of 91 (41 percent) given tobramycin (p less than 0.001), in 11 of 29 (38 percent) with liver disease and 33 of 150 (22 percent) without liver disease (p less than 0.08), and occurred in 11 of 15 (73 percent) with both liver disease and tobramycin use and in 0 of 14 (0 percent) with liver disease and cefotaxime use (p less than 0.001). By logistic regression analysis, the relative odds of renal dysfunction developing during tobramycin treatment in a patient were 6.0 (95 percent confidence interval: 3.8 to 9.5). The relative odds of renal dysfunction developing in a patient receiving tobramycin and having liver disease were 31.8 (95 percent confidence interval: 19.7 to 51.4). This analysis demonstrates an interaction between tobramycin use and liver disease for increasing the risk of renal dysfunction.

Kinetics of antimicrobial activity

Assessment of antimicrobial activity from standard in vitro minimum inhibitory and minimum bactericidal concentration determinations alone is incomplete. Rate of bacterial killing, effect of increasing concentration, sub-MIC effects, and degree of suppression of bacterial growth after limited exposure (post-antibiotic effect) more precisely describe the course of antimicrobial activity. Aminoglycoside antibiotics exhibit concentration-dependent bactericidal activity and a prolonged post-antibiotic effect. beta-Lactam antibiotics demonstrate more time-dependent killing and lack post-antibiotic effects, except with staphylococci. Most bacteriostatic antimicrobial agents also produce post-antibiotic suppression of growth. Studies in different animal infection models with a variety of organisms suggest that beta-lactams are more efficacious with continuous dosing, whereas the efficacy of aminoglycosides is relatively independent of dosing regimen, even when administered once daily. Knowledge of the kinetics of antimicrobial action is useful in predicting optimal dosage regimens.

Can the third-generation cephalosporins eliminate the need for antimicrobial combinations?

Antimicrobial combinations have been widely utilized since the beginning of the chemotherapeutic era. This is true despite the fact that the use of such combinations has a number of potential disadvantages, including (1) antibiotic antagonism; (2) an increased incidence of toxicity; (3) the emergence of multi-resistant organisms; (4) promotion of a false sense of security; and (5) increased expense. The reasons generally given for the use of such combinations include (1) antimicrobial synergism, (2) suppression of antimicrobial resistance, (3) decreased toxicity, and (4) broader coverage. Although there are clearly some situations in which synergistic combinations have been shown to be useful (such as in the treatment of enterococcal endocarditis and severe Pseudomonas infections), the use of combination therapy to reduce the emergence of resistance (excluding the treatment of mycobacterial infections and of infections in which rifampin is used) or to reduce toxicity has not met with widespread success. Indeed, most combinations are used simply to broaden the spectrum of antimicrobial coverage. The development of new penicillins and cephalosporins with broader spectra of activity has raised the distinct possibility that these drugs could be used as single agents for the treatment of most serious infections. Although comparative studies performed to date suggest that the new broad-spectrum penicillins and cephalosporins may be useful as single agents in the treatment of infections in a variety of clinical situations in which combinations are now commonly employed, additional studies enrolling greater numbers of patients are necessary to determine whether these agents can replace combination therapy. The use of single-drug therapy in the management of febrile episodes and documented infections in neutropenic patients remains problematic because of the greater likelihood of infections with organisms such as Pseudomonas aeruginosa, in which case combination therapy is often required. Earlier studies have clearly documented that combinations of antibiotics that are synergistic are more effective in treating bacteremias and other serious infections in neutropenic patients than are combinations that have failed to demonstrate synergism. Because of the increased activity of some of the newer drugs, such as ceftazidime, against P. aeruginosa it is possible that such agents could be used as monotherapy for patients with severe neutropenia. This possibility is an attractive one, but it should be studied carefully to make certain that it will not be associated with significant failure due to the emergence of resistant organisms.

Ceftazidime in the treatment of nosocomial sepsis

Ceftazidime has broad antibacterial activity against many gram-positive and most clinically significant nosocomial gram-negative bacillary pathogens. Many studies have been undertaken both in this country and in western Europe to determine the clinical effectiveness of ceftazidime in seriously ill patients. Differentiating between nosocomial and community-acquired infections is difficult in many reports, but high cure rates, usually exceeding 80 percent, have been reported for documented gram-negative bacillary infections. In non-neutropenic patients, response rates have also been in a comparable range. Particularly impressive have been the high cure rates in Pseudomonas aeruginosa bacteremia complicating burns and other gram-negative bacteremias in patients with underlying diseases. In comparative studies carried out in seriously ill or neutropenic patients, the results with ceftazidime have not significantly differed from those obtained with regimens that included beta-lactam agents paired with aminoglycosides. Some problem areas persist in these studies: the interpretation of comparative studies in which a large number of cases were eliminated because of "unevaluability," superinfections due to gram-positive organisms that may require or necessitate addition of agents like vancomycin, and the emergence of resistance as seen in three groups of organisms--Pseudomonas, Serratia, and Enterobacter species. Nonetheless, summary data from cases treated in the United States indicate cure and/or improvement in 100 percent of 14 cases of Serratia bacteremia, 83 percent of 12 cases of Enterobacter sepsis, 82 percent of 22 cases of Staphylococcus aureus bacteremia, and 85 percent in 27 cases of P. aeruginosa bacteremia. Only 11 of 86 cases of bacteremia due to the organisms just cited were judged unevaluable. Three of the four failures in the treatment of Pseudomonas bacteremia occurred in neutropenic patients. More definitive information on the relative efficacy of ceftazidime in controlled trials, particularly in granulocytopenic patients, may result from more careful analysis of survivorship using methods that do not eliminate "unevaluable cases." Techniques for this type of analysis have already been implemented in some studies.

Acute enteric sepsis: bacteriology and antibiotic cover

Most cases of enteric sepsis are caused by both aerobic and anaerobic organisms which form the normal flora of the mouth and lower gastrointestinal tract. This flora is extremely variable and subject to change due to disease and antimicrobial treatment. Bacteriological investigation of patients with severe enteric sepsis is important and should be undertaken before antibiotic treatment is commenced. The choice of antibiotics depends on the nature of the infection and its location. Initially they should be given in maximum dosage. If polymicrobial infection is suspected both aerobes and anaerobes should be covered to prevent bacteraemic shock and abscess formation. If abscesses have formed or the patient fails to respond to appropriate antibiotics, surgical exploration and drainage remain the treatment of choice. Antibiotics often fail to eradicate organisms from established abscesses and are responsible for some serious complications.

Use of aminoglycosides in immunocompromised patients

For much of the last decade, combination therapy with aminoglycosides has been accepted as the therapeutic approach of choice in immunocompromised hosts. Improved clinical results have also correlated with the presence of synergistic interactions between the aminoglycoside and beta-lactam components of a regimen. Differences between the aminoglycosides and beta-lactam agents remain a subject of controversy. Studies at the University of California, Los Angeles, Medical Center suggest that amikacin interacts more frequently in a synergistic manner with beta-lactams than do alternative aminoglycosides. Amikacin has been used experimentally and (following licensure) without reservation at the University of California, Los Angeles, Medical Center since 1973. Almost 100 blood isolates of both Pseudomonas aeruginosa and Klebsiella pneumoniae collected during the last 12 years have been retested, and no evidence of increased aminoglycoside resistance was found. A relatively new development is interest in empiric therapeutic regimens that employ two beta-lactam agents. In a large, recently completed study, less satisfactory results were observed in P. aeruginosa infections treated with the "double beta-lactam" than in those treated with the regimen containing amikacin; furthermore, nephrotoxicity and eighth nerve damage occurred no more commonly in the group receiving amikacin than in recipients of the double beta-lactam regimen.

The cephalosporin antibiotic agents--III. Third-generation cephalosporins

The third-“generation” cephalosporin antibiotics (Table 1) represent a class of agents with an expanded gram-negative spectrum of activity beyond that of the first- and second-“generation” cephalosporins. Greater stability to beta-lactamases produced by gram-negative organisms confers to these agents a greater bactericidal action against the Enterobacteriaceae. Large bacterial inocula (105/ml) in vitro significantly increase the minimum inhibitory and bactericidal concentrations (MIC and MBC) explaining treatment failures with these agents in infections associated with large numbers of organisms. The pharmacokinetic features of some of the agents allow prolongation of dosing intervals, and enhanced tissue penetration amplifies their clinical utility in infections distant from the bloodstream (eg, meningitis).

Lack of evidence for interaction between tobramycin and shock in their effect on renal function

We sought to determine whether there was an interaction between aminoglycoside use and shock in their effect on renal function among seriously ill patients suspected of having gram-negative sepsis. Serial serum creatinine determinations were used to estimate changes in creatinine clearance rates in 179 patients entered onto a prospective randomized trial of tobramycin-nafcillin versus cefotaxime. A 25% decline in estimated creatinine clearance was considered to be clinically important. Univariate chi-square analysis showed that both shock (P less than 0.01) and tobramycin use (P less than 0.001) were independently associated with decline in estimated creatinine clearance. A two-way analysis of variance showed that both shock (F = 10.44, P less than 0.01) and tobramycin use (F = 42.6, P less than 0.001) continued to be significantly associated with renal dysfunction in the presence of each other, but there was no significant interaction between shock and tobramycin in their effect (F = 0.62, P less than 0.43). A multiple logistic regression with an interaction term representing the occurrence of shock and tobramycin use simultaneously yielded similar results. Our study provided no analytic evidence supporting the existence of an interaction between shock and aminoglycoside use in their effect on renal function.

Gram-positive superinfections following beta-lactam chemotherapy: the significance of the enterococcus

The recent literature was reviewed with regard to the risks of superinfection following beta-lactam chemotherapy. The summary publications for the pseudomonas-active penicillins (azlocillin, carbenicillin, mezlocillin, piperacillin and ticarcillin), cefoperazone, cefotaxime, ceftazidime, imipenem and moxalactam show marked variations. Moxalactam was most likely to produce both gram-negative (5-38%) and enterococcal (2.2-12%) superinfections. Ceftazidime or moxalactam therapy was more often associated with anaerobic superinfections, usually by Clostridium spp., than the other beta-lactams. Comparable and lower incidences of superinfections were cited for cefoperazone, ceftazidime, mezlocillin and imipenem. The most common pathogens for the above drugs were the fungi (Candida spp.), Pseudomonas spp. and some beta-lactamase-producing Enterobacteriaceae. Staphylococcal, Escherichia coli and Klebsiella spp. secondary infections were more common in patients receiving the newer penicillins. Cefotaxime had a very low incidence of superinfections (1.1%), especially caused by gram-positive organisms such as enterococci. The reasons for this favorable feature seem to be: excellent inhibitory activity and beta-lactamase stability against a wide variety of bacterial pathogens, synergistic interactions of cefotaxime and its desacetyl metabolite, enhanced anti-enterococcal activity of cefotaxime in the presence of a human serum factor and interactions of cefotaxime and desacetyl cefotaxime to suppress the development of antimicrobial resistance. The most common superinfections following cefotaxime treatment were with Pseudomonas spp., Enterobacter spp. and fungi. Cefotaxime appears to possess physical-chemical characteristics that react favorably with bacteria and the host to minimize gram-positive superinfections, especially with most enteric Streptococcus spp. (Streptococcus faecalis and Streptococcus faecium).