Bactericidal effects of amoxycillin/clavulanic acid against a Legionella pneumophila pneumonia in the weanling rat

Treatment of Legionnaires??? Disease

Legionnaires' disease is pneumonia, usually caused by Legionella pneumophila, which can range in severity from mild to quite severe. While it is commonly acquired in the community, it can just as easily be acquired nosocomially from water sources that have not been appropriately decontaminated. While historically initial treatment was always with erythromycin, current case series and treatment recommendations suggest that outpatients receive immediate treatment with one of the following antibacterials: azithromycin, erythromycin, clarithromycin, telithromycin, doxycycline or an extended-spectrum fluoroquinolone. If the symptoms are severe enough to warrant hospitalisation then the patient should receive treatment with parenteral azithromycin or extended-spectrum fluoroquinolones followed by step-down to oral formulations to complete the regimens. While a shorter course of 7-10 days for more severe infections may be possible for intravenous/oral azithromycin, other antibacterials should be administered for a total of 10-21 days and started as soon as possible upon presentation to optimise outcomes.

Exacerbation with granulocyte colony-stimulating factor of prior acute lung injury during neutropenia recovery in rats

OBJECTIVE

Neutropenia recovery may be associated with an increased risk of respiratory function deterioration. A history of pneumonia complicating neutropenia has been identified as the leading cause of adult respiratory distress syndrome during neutropenia recovery in patients receiving anticancer chemotherapy, suggesting that neutropenia recovery may worsen prior lung injury.

DESIGN

Controlled animal study.

SETTING

Research laboratory of an academic institution.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

We studied the effect of recovery from cyclophosphamide-induced neutropenia on endotoxin (lipopolysaccharide)- or hydrochloric acid-induced acute lung injury in rats. We also studied the effects of adding granulocyte colony-stimulating factor.

MEASUREMENTS AND MAIN RESULTS

Compared with noncyclophosphamide-treated rats, rats undergoing neutropenia recovery had a higher wet/dry lung weight ratio after hydrochloric acid-induced but not lipopolysaccharide-induced acute lung injury. Granulocyte colony-stimulating factor significantly increased both alveolar cell recruitment (bronchoalveolar lavage fluid counts) and pulmonary edema (wet/dry lung ratio) in both acute lung injury models during neutropenia recovery. Furthermore, in an experiment in hydrochloric acid-instilled rats, exacerbation by granulocyte colony-stimulating factor of hydrochloric acid-induced acute lung injury was inhibited by lidocaine, which prevents adhesion of neutrophils to endothelial cells. Tumor necrosis factor-alpha and interleukin-1 beta concentrations in supernatants of lipopolysaccharide-stimulated alveolar macrophages from rats undergoing neutropenia recovery with granulocyte colony-stimulating factor treatment were significantly increased compared with rats undergoing neutropenia recovery without granulocyte colony-stimulating factor.

CONCLUSION

Neutropenia recovery can worsen acute lung injury, and this effect is exacerbated by granulocyte colony-stimulating factor.

Exacerbation by granulocyte colony-stimulating factor of prior acute lung injury: implication of neutrophils

OBJECTIVE

Granulocyte colony-stimulating factor is widely prescribed to hasten recovery from cancer chemotherapy-induced neutropenia and has been reported to induce pulmonary toxicity. However, circumstances and mechanisms of this toxicity remain poorly known.

DESIGN

To reproduce a routine situation in cancer patients receiving chemotherapy, we investigated the mechanisms underlying granulocyte colony-stimulating factor-induced exacerbation of alpha-naphthylthiourea-related pulmonary edema.

SETTING

Laboratory research unit.

SUBJECTS

Male specific-pathogen-free Sprague-Dawley rats.

INTERVENTIONS

The effects of granulocyte colony-stimulating factor given alone or after alpha-naphthylthiourea used to induce acute lung injury were investigated.

MEASUREMENTS AND MAIN RESULTS

Lung injury was assessed based on neutrophil sequestration (myeloperoxidase activity in lung tissue) and influx into alveolar spaces (bronchoalveolar lavage fluid cell quantification) and on edema formation (wet/dry lung weight ratio) and alveolar protein concentration into bronchoalveolar lavage fluid. Tumor necrosis factor-alpha and interleukin-1beta were measured in serum, lung homogenates, and isolated alveolar macrophage supernatants. In control rats, granulocyte colony-stimulating factor (25 microg/kg) significantly elevated circulating neutrophil counts without producing alveolar recruitment or pulmonary edema. alpha-Naphthylthiourea significantly increased the wet/dry lung weight ratio (4.68 +/- 0.04 vs. 4.38 +/- 0.07 in controls, p=.04) and induced alveolar protein leakage. Adding granulocyte colony-stimulating factor to alpha-naphthylthiourea exacerbated pulmonary edema, causing neutrophil sequestration in pulmonary vessels, significantly increasing lung myeloperoxidase activity (12.7 +/- 2.0 mOD/min/g vs. 1.1 +/- 0.4 mOD/min/g with alpha-naphthylthiourea alone; p<.0001), and increasing proinflammatory cytokine secretion. alpha-Naphthylthiourea-related pulmonary edema was not exacerbated by granulocyte colony-stimulating factor during cyclophosphamide-induced neutropenia or after lidocaine, which antagonizes neutrophil adhesion to endothelial cells. Tumor necrosis factor-alpha and interleukin-1beta concentrations in alveolar macrophage supernatants and lung homogenates were significantly higher with alpha-naphthylthiourea + granulocyte colony-stimulating factor than with either agent alone, and anti-tumor necrosis factor-alpha antibodies abolished granulocyte colony-stimulating factor-related exacerbation of alpha-naphthylthiourea-induced pulmonary edema. In rats with cyclophosphamide-induced neutropenia, tumor necrosis factor-alpha concentrations in alveolar macrophage supernatants and lung homogenates were significantly decreased compared with rats without neutropenia.

CONCLUSION

Granulocyte colony-stimulating factor-related pulmonary toxicity may involve migration of neutrophils to vascular spaces, adhesion of neutrophils to previously injured endothelial cells, and potentiation of proinflammatory cytokine expression.

In vitro extracellular and intracellular activities of clavulanic acid and those of piperacillin and ceftriaxone alone and in combination with tazobactam against clinical isolates of Legionella species

The activities of ceftriaxone, piperacillin, tazobactam, clavulanic acid, and combinations of ceftriaxone or piperacillin with tazobactam against 22 clinical Legionella isolates were measured by broth microdilution and macrodilution methods and in macrophages. The broth microdilution MICs that inhibited 90% of strains tested were 2 and 1 microgram/ml for ceftriaxone and tazobactam, respectively. Broth macrodilution MICs were 8 and 1 microgram/ml, respectively, for the two Legionella pneumophila strains tested with piperacillin and were 0.25 and 0.5 microgram/ml, respectively, for clavulanate. No significant intracellular anti-L. pneumophila activity was observed for ceftriaxone (32 micrograms/ml), piperacillin (32 micrograms/ml), tazobactam alone (16 micrograms/ml), clavulanate alone (2 micrograms/ml), or tazobactam in combination with ceftriaxone (ceftriaxone/tazobactam at 32/4 and 16/16 micrograms/ml) or piperacillin (32/4 micrograms/ml). Erythromycin (1 microgram/ml) was active against intracellular L. pneumophila in the same macrophage model of infection. It is very unlikely that tazobactam or clavulanate, alone or in combination with beta-lactam antimicrobial agents, will be effective for the treatment of Legionnaires' disease in humans.

Comparative activities of piperacillin and tazobactam against clinical isolates of Legionella spp

We evaluated the in vitro activity of piperacillin alone or in combination with the beta-lactamase inhibitor tazobactam against clinical isolates of Legionella species. At an inoculum of approximately 10(4) CFU, tazobactam, piperacillin, and the 8:1 combination had equivalent activities against Legionella spp. At an approximately 10-fold higher inoculum, the following results were obtained, expressed as MICs for 50 and 90% of strains tested (MIC range): piperacillin, 4 and 16 (0.25 to 32) micrograms/ml; tazobactam, 0.5 and 1 (0.125 to 2) micrograms/ml; and piperacillin-tazobactam (expressed in terms of MIC of piperacillin) 0.5 and 1 (0.03 to 2) micrograms/ml. Tazobactam alone and the combination with piperacillin were more active than piperacillin alone at the higher inoculum.

Community-acquired pneumonia

The aetiology of community-acquired pneumonia is reviewed, and the identification of the most likely pathogens, based on clinical presentation, is discussed. By far the major pathogen in community-acquired pneumonia is Streptococcus pneumoniae; the relative frequency of other pathogens, and particularly the atypical pneumonias caused by Mycoplasma and Legionella spp., will depend on local epidemiological factors. The diagnostic tests to confirm diagnosis and subsequent treatment of these infections are reviewed.

Activity of amoxycillin-clavulanic acid against Legionella pneumophila in vitro and in an experimental respiratory infection model

Amoxycillin and clavulanic acid show good activity against Legionella pneumophila in vitro, and synergy has been observed between the two agents. However, in tissue culture studies, amoxycillin was inactive against intracellular legionellae, whereas clavulanic acid and amoxycillin plus clavulanic acid were as effective as erythromycin in preventing bacterial growth. These latter findings were reflected in the results of therapy of a L. pneumophila pneumonia in the neutropenic rat. Amoxycillin was ineffective in reducing bacterial counts in the lungs of infected animals, but clavulanic acid and amoxycillin-clavulanic acid produced bactericidal effects similar to those of erythromycin. The data illustrate the bactericidal activity of amoxycillin-clavulanic acid and clavulanic acid against intracellular L. pneumophila in contrast to the lack of activity of amoxycillin.

Fatal Legionella pneumophila pneumonia: treatment failure despite early sequential oral-parenteral amoxicillin-clavulanic acid therapy

A 68-year-old male, having just returned from a two-week holiday on the Island of Ischia, developed unilateral pneumonia for which he was treated with oral amoxicillin-clavulanic acid and hospitalized within three days when the disease worsened and spread to both lungs. Despite parenteral amoxicillin-clavulanic acid (up to 2.2 g i.v. t.i.d.) the pneumonia spread rapidly over the next three days. Sputum cultures returned post mortem yielded Legionella pneumophila serogroup 1 and urine tests revealed the presence of Legionella antigen. Disk diffusion susceptibility testing on BCYE of the causative pathogen revealed zone diameters of inhibition of the clinical isolate exceeding 50 mm, indicating high susceptibility to this antibiotic combination. The therapeutic failure of amoxicillin-clavulanic acid should stimulate further reports and studies on the efficacy against legionellosis of this drug and similar beta-lactam inhibitor combinations as well as other beta-lactamase-stable beta-lactams.

Current trends in bacterial respiratory pathogens

The relationship of virulence and antimicrobial susceptibility with morbidity due to bacterial respiratory pathogens is complex and evolving. Ultimately, decreasing the incidence of pneumonia due to bacterial pathogens will be dependent on successful preparation and distribution of effective vaccines. Until effective vaccines are widely available, control of a majority of respiratory infections will depend on promotion of rational therapeutic strategies. Though limited to a few specific serotypes and strains, changes in virulence of bacterial respiratory pathogens have been noted. Co-infections due to multiple respiratory pathogens may increase morbidity; however, the epidemiology of co-infections is not clear. Relationships between respiratory viruses and bacteria may exist that increase virulence of both agents, but information regarding these relationships awaits further investigation. Resistance of respiratory pathogens to the more commonly used antimicrobials, such as penicillin, erythromycin, chloramphenicol, and cotrimoxazole, is being documented globally with increasing frequency. The evolution of antimicrobic resistance, especially among strains of Streptococcus pneumoniae, the most common and deadly agent of lower respiratory tract infections, provides impetus to develop and promote effective pneumococcal vaccines and to search for new and effective antimicrobials.

Bactericidal effects of ticarcillin-clavulanic acid against Legionella pneumophila pneumonia in immunocompromised weanling rats

A model of acute Legionella pneumophila pneumonia in neutropenic weanling rats was developed as a means of assessing the efficacies in vivo of the beta-lactams ticarcillin, ticarcillin-clavulanic acid, and clavulanic acid, agents active against the organism in vitro. Weanling rats were dosed with cyclophosphamide 3 days before and immediately prior to infection by intrabronchial intubation with L. pneumophila. The bacteria persisted in the lungs of untreated animals at high counts (5.0 to 7.0 log10 CFU/g of lung tissue) for up to 168 h after infection, and the histological characteristics of the infection were similar to those of the disease in humans. Transmission electron micrography revealed the presence of L. pneumophila multiplying within alveolar macrophages. Therapy with ticarcillin was ineffective in reducing the bacterial numbers in the lung tissue, whereas ticarcillin-clavulanic acid and clavulanic acid were active, producing bactericidal effects similar to those of erythromycin. The ticarcillin-clavulanic acid combination was significantly more efficacious (P less than 0.01) than corresponding doses of clavulanic acid alone. Synergistic activity between ticarcillin and clavulanic acid against L. pneumophila has been demonstrated in vivo, and the combination showed activity similar to that of erythromycin.