Drug-resistant Streptococcus pneumoniae in Community-acquired Pneumonia

Bacteraemic pneumococcal pneumonia: Impact of HIV on clinical presentation and outcome

OBJECTIVES

The objectives of this study were to investigate the clinical and laboratory features, hospital course and outcome of patients with bacteraemic pneumococcal pneumonia, comparing HIV with non-HIV patients, as well as HIV patients from different parts of the world.

METHODS

This was a multicentre prospective observational study of consecutive adult cases with bacteraemic pneumococcal pneumonia in 10 countries on 6 continents.

RESULTS

A total of 768 cases were recruited, of which 200 were HIV-infected; 166 were from South Africa. Lower age, i.v. drug use, fewer co-morbid illnesses, and a higher frequency of respiratory symptoms were significantly more likely to occur in HIV patients. The 14-day mortality for the group as a whole was 14.5%, being 16% in the HIV patients and 13.9% in the non-HIV patients (not significant). When adjustments were made for age and severity of illness, HIV patients had significantly higher 14-day mortality with significant trend for increasing 14-day mortality in those with lower CD4 counts. Despite differences in various clinical and laboratory parameters in patients from different parts of the world, on multivariate analysis, when adjusting for regional differences, the HIV-infected patients were still noted to have poorer 14-day mortality.

CONCLUSIONS

This study, in contrast to previous investigations, indicates that there are significant differences in the clinical presentation and outcome of bacteraemic pneumococcal pneumonia when comparing HIV and non-HIV patients.

In vitro selection of resistance to clarithromycin in Streptococcus pneumoniae clinical isolates

In this study the effects of exposure to serum, lung and breakpoint concentrations on Streptococcus pneumoniae susceptibility to clarithromycin, azithromycin, amoxicillin/clavulanate, levofloxacin and moxifloxacin were evaluated. Development of resistance was determined by multi-step and single-step methodologies. In the first experimental set, minimum inhibitory concentrations (MICs) were determined after 10 passages on antibiotic-gradient plates and 10 passages on antibiotic-free plates. Acquisition of resistance was defined as an increase of > or = 4-fold from the starting MIC. In single-step studies, the rate of spontaneous mutations was calculated after a passage on antibiotic-containing agar plates. Azithromycin and levofloxacin gave the highest number of strains with MIC increased of at least 4 times the starting value, followed by moxifloxacin and by clarithromycin which only at the lowest concentration tested selected for resistance in 5 strains. Amoxicillin/clavulanate never displayed > or = 4-fold MIC increase. Frequencies of mutation were lower for clarithromycin and moxifloxacin than for the comparators. At lung concentrations clarithromycin had limited potential to select for resistance.

Clinical relevance of antimicrobial resistance in the management of pneumococcal community-acquired pneumonia

Streptococcus pneumoniae remains the most common bacterial cause of community-acquired pneumonia, and these infections are associated with significant morbidity and mortality worldwide. A major concern is the increasing incidence of antibiotic resistance among pneumococcal isolates, which, in the case of certain of the antibiotic classes, has been associated with treatment failure. Yet despite multiple reports of infections with penicillin-resistant pneumococcal isolates, no cases of bacteriologic failure have been documented with the use of penicillin or ampicillin in the treatment of pneumonia caused by penicillin-resistant pneumococci. Current prevalence and levels of penicillin resistance among pneumococal isolates in most areas of the world do not indicate a need for substantial treatment changes with regard to the use of the penicillins. For infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will still be effective for treatment. In the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment, although higher dosages are recommended. Infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In the case of the cephalosporins, pharmacodynamic/pharmacokinetic parameters help predict which of those agents are likely to be successful, and the less active agents should not be used. Debate continues in the literature with regard to the impact of macrolide resistance on the outcome of pneumococcal pneumonia, with some investigators providing evidence of an "in vivo-in vitro paradox," referring to discordance between reported in vitro resistance and clinical success of macrolides/azalide in vivo. However, several cases of macrolide/azalide treatment failure have been documented, and many clinicians recommend that these agents not be used on their own in areas with a high prevalence and levels of macrolide/azalide resistance. However, evidence is emerging to show beneficial effects on outcome with combination therapy, especially that of a beta-lactam agent and a macrolide given together to sicker, hospitalized patients with pneumococcal pneumonia. In an attempt to prevent the emergence of resistance, it has been recommended by some that the new fluoroquinolones not be used routinely as first-line agents in the treatment of community-acquired pneumonia; instead, they say, these agents should be reserved for patients who are allergic to the commonly used beta-lactam agents, for infections known to be or suspected of being caused by highly resistant strains, and for patients in whom initial therapy has failed.

Systemic up-regulation of sTNFR2 and IL-6 in Porphyromonas gingivalis pneumonia in mice

Aspiration pneumonia is a common cause of death in older people, and the pathophysiology is a chronic respiratory failure with a mild airway inflammation. In this study, we established a mild inflammatory pneumonia model using Porphyromonas gingivalis (Pg) pathogen-infected mice. It elucidated the effects of Pg-infected pneumonia on proinflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin-6 (IL-6), and IL-1beta production in both lung tissue and serum. We also elucidated production of soluble (s) TNF receptor (R) s, because TNF-alpha is considered to be a dominant inflammatory mediator. Lung TNF-alpha levels significantly increased at 2 h after infection, and rapidly returned to basal level at 24 h. Consistent with increase of TNF-alpha, remarkable increase of sTNFR2 but not sTNFR1 was detected in lung tissue from 2 to 72 h. Interestingly, sTNFR2/sTNFR1 ratio was significantly enhanced at 2 h in serum. In addition, lung IL-1beta and IL-6 levels also significantly increased from 2 to 24 h. Importantly, we found that IL-6 levels in serum reflected its local level. These results may suggest that systemically produced sTNFR2 and IL-6 could be a key role to modulate proinflammatory activities of TNF-alpha in Pg-induced lung inflammation simulated aspiration pneumonia.