Systemic antibiotic treatment of nosocomial pneumonia

Enhancing the Thermo-Stability and Anti-Bacterium Activity of Lysozyme by Immobilization on Chitosan Nanoparticles

The recent emergence of antibiotic-resistant bacteria requires the development of new antibiotics or new agents capable of enhancing antibiotic activity. Lysozyme degrades bacterial cell wall without involving antibiotic resistance and has become a new antibacterial strategy. However, direct use of native, active proteins in clinical settings is not practical as it is fragile under various conditions. In this study, lysozyme was integrated into chitosan nanoparticles (CS-NPs) by the ionic gelation technique to obtain lysozyme immobilized chitosan nanoparticles (Lys-CS-NPs) and then characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which showed a small particle size (243.1 ± 2.1 nm) and positive zeta potential (22.8 ± 0.2 mV). The immobilization significantly enhanced the thermal stability and reusability of lysozyme. In addition, compared with free lysozyme, Lys-CS-NPs exhibited superb antibacterial properties according to the results of killing kinetics in vitro and measurement of the minimum inhibitory concentration (MIC) of CS-NPs and Lys-CS-NPs against Pseudomonas aeruginosa (P. aeruginosa), Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus). These results suggest that the integration of lysozyme into CS-NPs will create opportunities for the further potential applications of lysozyme as an anti-bacterium agent.

Nosokomiale Pneumonie – Antibiotikatherapie und hygienische Interventionsstrategien

Die Pneumonie ist auch in unserer Zeit eine schwere Infektionskrankheit. Sie ist eine der häufigsten infektiösen Todesursachen der westlichen Industrieländer und steht an 3. Stelle unter den Infektionskrankheiten. Jede 4. ärztlich diagnostizierte Pneumonie ist nosokomial erworben. Nosokomiale Pneumonien führen neben einer verlängerten Morbidität und erhöhten Letalität zu einer Verlängerung der Krankenhausverweildauer und zu erheblichen Kosten.

Nosocomial pneumonia : rationalizing the approach to empirical therapy

Nosocomial pneumonia or hospital-acquired pneumonia (HAP) causes considerable morbidity and mortality. It is the second most common nosocomial infection and the leading cause of death from hospital-acquired infections. In 1996 the American Thoracic Society (ATS) published guidelines for empirical therapy of HAP. This review focuses on the literature that has appeared since the ATS statement. Early diagnosis of HAP and its etiology is crucial in guiding empirical therapy. Since 1996, it has become clear that differentiating mere colonization from etiologic pathogens infecting the lower respiratory tract is best achieved by employing bronchoalveolar lavage (BAL) or protected specimen brush (PSB) in combination with quantitative culture and detection of intracellular microorganisms. Endotracheal aspirate and non-bronchoscopic BAL/PSB in combination with quantitative culture provide a good alternative in patients suspected of ventilator-associated pneumonia. Since culture results take 2-3 days, initial therapy of HAP is by definition empirical. Epidemiologic studies have identified the most frequently involved pathogens: Enterobacteriaceae, Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus aureus ('core pathogens'). Empirical therapy covering only the 'core pathogens' will suffice in patients without risk factors for resistant microorganisms. Studies that have appeared since the ATS statement issued in 1996, demonstrate several new risk factors for HAP with multiresistant pathogens. In patients with risk factors, empirical therapy should consist of antibacterials with a broader spectrum. The most important risk factors for resistant microorganisms are late onset of HAP (>/=5 days after admission), recent use of antibacterial therapy, and mechanical ventilation. Multiresistant bacteria of specific interest are methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter calcoaceticus-baumannii, Stenotrophomonas maltophilia and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. Each of these organisms has its specific susceptibility pattern, demanding appropriate antibacterial treatment. To further improve outcomes, specific therapeutic options for multiresistant pathogens and pharmacological factors are discussed. Antibacterials developed since 1996 or antibacterials with renewed interest (linezolid, quinupristin/dalfopristin, teicoplanin, meropenem, new fluoroquinolones, and fourth-generation cephalosporins) are discussed in the light of developing resistance.Since the ATS statement, many reports have shown increasing incidences of resistant microorganisms. Therefore, one of the most important conclusions from this review is that empirical therapy for HAP should not be based on general guidelines alone, but that local epidemiology should be taken into account and used in the formulation of local guidelines.

Basic aspects of and general problems in surgical infections

Antibiotics are important in the prophylaxis and treatment of surgical infections as well as in the management of nosocomial infections acquired postoperatively in surgical patients. Surgeons encounter a range of infectious conditions, including established single-pathogen infections of soft tissues, polymicrobial intra-abdominal infections, and resistant gram-negative nosocomial infections such as ventilator-associated and aspiration pneumonia. Preoperative antibiotic administration has been shown to reduce the risk of surgical site infections and is now an accepted part of the standard care for most surgical patients. In patients with established single-pathogen or polymicrobial infections requiring surgery, studies have shown appropriate empiric antibiotic therapy to be an important adjunct to surgical intervention and general supportive measures in improving patient outcome. Antibiotics are also essential for those who develop postoperative nosocomial infections. Empiric coverage of the most likely causative organisms, especially in synergistic polymicrobial mixed infections, is one of the keys to successful prophylaxis and treatment of surgical infections.

Efficacy of meropenem as monotherapy in the treatment of ventilator-associated pneumonia

We performed a prospective, open label, randomized study in intensive care unit patients with ventilator-associated pneumonia (VAP) to determine the efficacy and safety of empiric intravenous (i.v.) meropenem monotherapy compared with the combination of ceftazidime plus amikacin. A total of 140 patients receiving mechanical ventilation and diagnosed with pneumonia were included in the study. Patients were randomized to receive either 1 g meropenem i.v. every 8 hours or 2 g ceftazidime i.v. every 8 hours plus 15 mg/kg amikacin daily, administered to patients with normal renal function as two daily doses. Satisfactory clinical responses (cure or improvement) were achieved at the end of treatment in 68.1% of meropenem-treated patients and 54.9% in the ceftazidime/amikacin-treated group (relative risk 1.25; 95% confidence interval >1.00, 1.55). When non-evaluable patients were excluded from the analysis, the satisfactory clinical response was 82.5% and 66.1% for the meropenem and ceftazidime/amikacin patients, respectively (p = 0.044). Logistic regression demonstrated that treatment with meropenem and both the basic traumatic and medical pathologies were significantly associated with a satisfactory response. Adverse events judged to be possibly or probably related to treatment were reported by seven (10.1%) patients in the meropenem group and by eight patients (11.3%) in the ceftazidime/amikacin group. The results of this study confirm that monotherapy with meropenem is well tolerated and provides superior efficacy to the conventional combination of ceftazidime and amikacin in combating VAP.

Prospective randomized comparison of imipenem-cilastatin and piperacillin-tazobactam in nosocomial pneumonia or peritonitis

Nosocomial pneumonia and acute peritonitis may be caused by a wide array of pathogens, and combination therapy is often recommended. We have previously shown that imipenem-cilastatin monotherapy was as efficacious as the combination of imipenem-cilastatin plus netilmicin in these two settings. The efficacy of imipenem-cilastatin is now compared to that of piperacillin-tazobactam as monotherapy in patients with nosocomial pneumonia or acute peritonitis. Three hundred seventy one patients with nosocomial pneumonia or peritonitis were randomly assigned to receive either imipenem-cilastatin (0.5 g four times a day) or piperacillin-tazobactam (4.5 g three times a day). Three hundred thirteen were assessable (154 with nosocomial pneumonia and 159 with peritonitis). For nosocomial pneumonia, clinical-failure rates in the piperacillin-tazobactam group (13 of 75 [17%]) and in the imipenem-cilastatin group (23 of 79 [29%]) were similar (P = 0.09), as were the numbers of deaths due to infection (6 in the imipenem-cilastatin group [8%], 7 in the piperacillin-tazobactam group [9%]) (P = 0.78). For acute peritonitis, clinical success rates were comparable (piperacillin-tazobactam, 72 of 76 [95%]; imipenem-cilastatin, 77 of 83 [93%]). For infections due to Pseudomonas aeruginosa, 45 patients had nosocomial pneumonia (21 in the piperacillin-tazobactam group and 24 in the imipenem-cilastatin group) and 10 had peritonitis (5 in each group). In the patients with nosocomial pneumonia, clinical failure was less frequent in the piperacillin-tazobactam group (2 of 21 [10%]) than in the imipenem-cilastatin [corrected] group (12 of 24 [50%]) (P = 0.004). Bacterial resistance to allocated regimen was the main cause of clinical failure (1 in the piperacillin-tazobactam group and 12 in the imipenem-cilastatin group). For the patients with peritonitis, no difference in clinical outcome was observed (five of five cured in each group). The overall frequencies of adverse events related to treatment in the two groups were similar (24 in the piperacillin-tazobactam group, 22 in the imipenem-cilastatin group). Diarrhea was significantly more frequent in the piperacillin-tazobactam group (10 of 24) than in the imipenem-cilastatin group (2 of 22). This study suggests that piperacillin-tazobactam monotherapy is at least as effective and safe as imipenem-cilastatin monotherapy in the treatment of nosocomial pneumonia or peritonitis. In P. aeruginosa pneumonia, piperacillin-tazobactam achieved a better clinical efficacy than imipenem-cilastatin, due to reduced development of microbiological resistance. Tolerance was comparable, with the exception of diarrhea, which was more frequent with piperacillin-tazobactam.

The total process cost of parenteral antibiotic therapy: beyond drug acquisition cost

Intravenous antibiotic therapy represents a considerable expense to hospital pharmacy budgets; however, when evaluating the cost of these therapies one needs to look beyond acquisition cost and consider the total "process" cost of treatment. These additional costs include the personnel time and the materials required for drug preparation and administration, maintenance of intravenous access, waste disposal, and therapeutic drug monitoring. This paper provides an examination of the daily process costs of intravenous therapy with cefazolin, cefotaxime, ceftazidime, once-daily ceftriaxone, cefuroxime, or aminoglycoside (tobramycin or gentamicin) combination therapy, where the aminoglycoside is given once daily or in divided doses. This analysis demonstrates that the costs associated with drug preparation and administration can equal or exceed drug acquisition costs and are highly dependent on dosing frequency. On this basis, ceftriaxone, at $52.21, is the least expensive of these antibiotic regimens in terms of total daily process cost, followed by the remaining cephalosporins at $53.29 to $94.57, aminoglycoside once-daily combinations at $93.44 to $99.65, and aminoglycoside multidose combinations at $103.26 to $111.42, respectively (values are given in constant 1995 Canadian dollars). Once-daily ceftriaxone offers the potential for cost savings compared with other antibiotic regimens whose pharmacokinetics require multiple daily doses, due largely to the reduced resources required for ceftriaxone preparation and administration.

Modification of empiric antibiotic treatment in patients with pneumonia acquired in the intensive care unit. ICU-Acquired Pneumonia Study Group

OBJECTIVE

To assess the frequency of and the reasons for changing empiric antibiotics during the treatment of pneumonia acquired in the intensive care unit (ICU).

DESIGN

A prospective multicenter study of 1 year's duration.

SETTING

Medical and surgical ICUs in 30 hospitals all over Spain.

PATIENTS

Of a total of 16,872 patients initially enrolled into the study, 530 patients developed 565 episodes of pneumonia after admission to the ICU.

RESULTS

Empiric antibiotics were administered in 490 (86.7%) of the 565 episodes of pneumonia. The antimicrobials most frequently used were amikacin in 120 cases, tobramycin in 110, ceftazidime in 96, and cefotaxime in 96. Monotherapy was indicated in 135 (27.6%) of the 490 episodes, a combination of two antibiotics in 306 episodes (62.4%), and a combination of three antibiotics in 49 episodes (10%). The empiric antibiotic treatment was modified in 214 (43.7%) cases because of isolation of a microorganism not covered by treatment in 133 (62.1%) cases, lack of clinical response in 77 (36%), and development of resistance in 14 (6.6%). Individual factors associated with modification of empiric treatment identified in the multivariate analysis were microorganism not covered (relative risk (RR)) 22.02; 95% confidence interval (CI) 11.54 to 42.60; p < 0.0001), administration of more than one antimicrobial (RR 1.29; 95% CI 1.02 to 1.65; p = 0.021), and previous use of antibiotics (RR 1.22; 95% CI 1.08 to 1.39; p = 0.0018). Attributable mortality was 16.2% in patients with appropriate initial therapy and 24.7% in patients with inappropriate treatment (p = 0.034).

CONCLUSIONS

A high percentage of patients (43.7%) required modification of empiric antibiotic treatment for pneumonia acquired in the ICU. In 62.1% of cases the main reason for changing antibiotic treatment was inadequate antibiotic coverage of microorganisms. Attributable mortality was significantly higher in patients with inappropriate initial antibiotic therapy. Rapid and accurate diagnostic methods are needed to initiate appropriate antibiotic treatment as soon as pneumonia is suspected.

Imipenem/cilastatin: an update of its antibacterial activity, pharmacokinetics and therapeutic efficacy in the treatment of serious infections

The prototype carbapenem antibacterial agent imipenem has a very broad spectrum of antibacterial activity, encompassing most Gram-negative and Gram-positive aerobes and anaerobes, including most beta-lactamase-producing species. It is coadministered with a renal dehydropeptidase inhibitor, cilastatin, in order to prevent its renal metabolism in clinical use. Extensive clinical experience gained with imipenem/cilastatin has shown it to provide effective monotherapy for septicaemia, neutropenic fever, and intra-abdominal, lower respiratory tract, genitourinary, gynaecological, skin and soft tissues, and bone and joint infections. In these indications, imipenem/cilastatin generally exhibits similar efficacy to broad-spectrum cephalosporins and other carbapenems and is at least equivalent to standard aminoglycoside-based and other combination regimens. Imipenem/cilastatin is generally well tolerated by adults and children, with local injection site events, gastrointestinal disturbances and dermatological reactions being the most common adverse events. Seizures have also been reported, occurring mostly in patients with impaired renal function or CNS pathology, or with excessive dosage. Although it is no longer a unique compound, as newer carbapenems such as meropenem are becoming available, imipenem/cilastatin nevertheless remains an important agent with established efficacy as monotherapy for moderate to severe bacterial infections. Its particular niche is in treating infections known or suspected to be caused by multiresistant pathogens.

Retrospective analysis of risk factors and prognosis in non-ventilated patients with nosocomial pneumonia

Although nosocomial pneumonia in non-ventilated patients continues to be frequent and have high mortality rates, knowledge of the associated risk and prognostic factors is still limited. This retrospective study was designed to analyze epidemiological characteristics, risk and prognostic factors in patients with nosocomial pneumonia admitted to a hospital internal medicine department. Data on epidemiological, clinical and microbiological factors as well as diagnosis and clinical course were obtained from the medical records of 104 patients diagnosed with nosocomial pneumonia, according to Centers for Disease Control criteria, and from 104 control subjects. The incidence of nosocomial pneumonia was 18.8 per 1000 admissions. Risk factors significantly associated with contracting the disease were female sex, hospital stay longer than 14 days, other admission in the previous month and use of antibiotics during the previous six weeks. The most frequent underlying diseases were cardiorespiratory in nature (59.4%). Prognostic factors significantly associated with increased mortality were serious underlying disease, initially critical clinical status, severe and moderate respiratory insufficiency and bilateral radiological signs. More epidemiological data are needed to improve the diagnosis, treatment and prevention of nosocomial pneumonia.

Influence of pulmonary surfactant on in vitro bactericidal activities of amoxicillin, ceftazidime, and tobramycin

The influence of a natural pulmonary surfactant on antibiotic activity was investigated to assess the possible use of exogenous surfactant as a vehicle for antibiotic delivery to the lung. The influence of surfactant on the bactericidal activity of amoxicillin was tested against Staphylococcus aureus and Streptococcus pneumoniae, and the influence of surfactant on the activities of ceftazidime and tobramycin was tested against Klebsiella pneumoniae, Pseudomonas aeruginosa, S. aureus, and S. pneumoniae. In vitro antibiotic activity was determined by killing curve studies in media with and without surfactant. Amoxicillin and ceftazidime activities were not changed in the presence of surfactant, except for a decreased killing rate of S. pneumoniae by ceftazidime in medium with additional rabbit serum. In contrast, killing curves with low concentrations of tobramycin (0.25x and 1x the MIC) showed a decreased level of activity of tobramycin against all pathogens tested in the presence of surfactant. With higher tobramycin concentrations (4x the MIC) killing rates were decreased less or were unchanged in the presence of surfactant. Concluding from the results of the study, both amoxicillin and ceftazidime can be combined with surfactant without the loss of activity. For mixing surfactant with tobramycin, dosages should be adjusted to overcome the partial inactivation of tobramycin by surfactant.

Serious Infections Caused by Pseudomonas Aeruginosa

Over the last 3 decades, Pseudomonas aeruginosa has become a leading cause of infectious morbidity and mortality in certain predisposed patient populations. It primarily affects those with impaired host defenses, and its prevalence in the hospital environment makes it an important nosocomial pathogen. Infection with this organism may result in a broad spectrum of clinical manifestations, many of which may be seen in the intensive care setting. This review focuses on epidemiology, clinical presentations, nad treatment of serious Pseudomonas infections.