New and emerging etiologies for community-acquired pneumonia with implications for therapy. A prospective multicenter study of 359 cases

Should third-generation cephalosporins be the empirical treatment of choice for severe community-acquired pneumonia in adults?

The choice of empirical treatment for community-acquired pneumonia (CAP) is highly controversial. Our survey of 42 Australian emergency department doctors showed that monotherapy with a third-generation cephalosporin was the preferred regimen for severe CAP (14/42; 33%). We argue that cheaper regimens with a narrower spectrum are likely to be just as effective as third-generation cephalosporins and will have fewer adverse effects on the microbial ecology of hospitals. We suggest penicillin or ampicillin (to cover pneumococci--even if penicillin "resistant"--and Haemophilus influenzae), plus a macrolide (e.g., azithromycin or erythromycin; to cover Legionella and other "atypical" pathogens), plus a single large dose of an aminoglycoside (e.g., gentamicin; to cover gram-negative bacilli such as Klebsiella pneumoniae) as empirical therapy for severe CAP.

Microbiology of bacterial respiratory infections

The upper respiratory tract may become susceptible to bacterial infection as a result of health conditions such as allergies and viral infections, as well as the effects of smoking and airborne environmental pollutants. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis are the most common bacterial pathogens in upper and lower respiratory tract infections. Streptococcus pyogenes is the predominant bacterial pathogen in pharyngitis and tonsillitis. Bacterial pathogens adhere to mucous membranes and colonization ensues. In an otherwise healthy individual the host immune system responds to the invading bacteria resulting in edema and swelling. If antimicrobial treatment does not eradicate the invading organisms and successfully interrupt the progress of the infection, the patient may develop recurrent or chronic disease. S. pneumoniae and other pathogens once susceptible to penicillin and other antibiotics are now becoming resistant. Bacterial resistance has developed and disseminated because of the widespread use of antibiotics. Major mechanisms of bacterial resistance to antimicrobials in upper respiratory tract infections include enzymatic inhibition, membrane impermeability, alteration of target enzymes, active pumping out of antibiotic and alteration of the ribosomal target.

Implications of oral infections on systemic diseases in the institutionalized elderly with a special focus on pneumonia

Systemic infection in the elderly patient living in a chronic care setting presents a significant burden to the health care system. The extent to which oral organisms cause systemic infections through hematogenous dissemination in the institutionalized elderly is still unknown. A more likely and common route of systemic infection by oral microorganisms is through aspiration of oropharyngeal fluids containing oral pathogenic microorganisms, which colonize the lower respiratory tract and cause pneumonia. Respiratory pathogens emerge in the dental plaque of elderly patients with very poor oral hygiene and severe periodontal disease. In the chronic care setting, aspiration of oropharyngeal fluids contaminated with these bacteria occurs in patients with diminished host defenses, resulting in bacterial pneumonia. This is also a problem in intensive care units in the hospital setting. In one study, pre-rinsing with a 0.12% chlorhexidine gluconate mouthwash significantly lowered the mortality rate from postsurgical pneumonia in patients undergoing open heart surgery. Selective digestive decontamination, a technique involving the topical application of antimicrobials to reduce the risk of colonization of the respiratory tract, has been used to reduce the incidence of nosocomial pneumonia in the acute care setting of hospitals. This technique has not been employed in the nursing home setting. Whether improving oral hygiene would also lower the risk in either of these settings has not been studied. A number of obstacles must be overcome in designing studies to investigate the relationship between oral infections and lung infections in the institutionalized elderly. Ethical issues must be addressed, and full collaboration of the medical team is required. Future studies should establish whether reducing the risk for pneumonia in the institutionalized elderly is possible through improved oral health.

Use of guidelines in treating community-acquired pneumonia

STUDY OBJECTIVES

Guidelines for empiric treatment of community-acquired pneumonia (CAP) have been developed to assist in prescribing appropriate antimicrobials. We studied utilization of guidelines developed by the American Thoracic, Canadian Infectious Diseases, and Canadian Thoracic Societies (ATS, CIDS, and CTS, respectively), physicians' familiarity with them, reasons that prompt deviation from them, and their effects on clinical outcomes.

DESIGN

Two-part observational study, with prospective and retrospective groups.

SETTING

A 1,100-bed, two-campus, tertiary-care teaching hospital.

PATIENTS AND PARTICIPANTS

Patients admitted to the general medical ward who were being treated empirically for CAP and housestaff who provided their care.

INTERVENTIONS

Medical residents reported on patients admitted to the hospital with CAP. The charts of all unreported patients admitted with CAP over the same period were reviewed.

MEASUREMENTS AND RESULTS

One hundred twenty-two patients were prospectively described and another 130 patients were identified retrospectively. There was no difference in guidelines adherence between the prospective and retrospective groups (81% compared with 80%; p=0.94). Deviation occurred most commonly in suspected aspiration. When physicians believed that they were following guidelines, this was true in 88%. When physicians believed that they were deviating, they were actually adhering in 46%. Guidelines adherence did not alter in-hospital mortality (12% compared with 14%, p=0.92) or length of hospitalization (median, 6 days for both groups).

CONCLUSIONS

ATS/CIDS/CTS guidelines for empiric treatment of CAP are widely used in our institution. Future amendments should address aspiration more explicitly. Residents' familiarity with them could be improved. Beneficial effects on outcomes remain unproven.

Trovafloxacin versus high-dose amoxicillin (1 g three times daily) in the treatment of community-acquired bacterial pneumonia

Once-daily trovafloxacin 200 mg was compared with high-dose amoxicillin, 1 g three times daily, given for 7 to 10 days. At end of treatment (day 10), the response was clinically successful (cure + improvement) in 93% of 152 clinically evaluable trovafloxacin patients and in 89% of 160 amoxicillin patients. At study end (day 35), respective rates were 91% and 81% (95% confidence interval: 1.6, 17.6; P=0.01). In evaluable patients with positive baseline radiographs, 93% of trovafloxacin and 88% of amoxicillin patients demonstrated radiological resolution at end of treatment. Streptococcus pneumoniae and Haemophilus influenzae eradication rates were comparable at end of treatment in both treatment groups, but at study end Streptococcus pneumoniae eradication rates were higher in trovafloxacin patients (100% vs 81%). At study end, all four trovafloxacin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinically cured with pathogen eradication, whereas two of five amoxicillin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinical failures with pathogen persistence. For patients in whom no pathogen was identified, trovafloxacin was significantly more effective at end of treatment (P=0.096) and study end (P=0.013). Treatment-related adverse events were comparable; the most common were headache, vomiting and dizziness in trovafloxacin patients, and diarrhoea. headache and abdominal pain in amoxicillin patients.

Implications for macrolide treatment in community-acquired pneumonia. Hopkins CAP Team

STUDY OBJECTIVES

To identify associated clinical parameters, concurrent respiratory tract infections, and the association between macrolide-based therapy and mortality in patients with community-acquired pneumonia ascribed to atypical.

DESIGN

Secondary analysis of prospective, cross-sectional study.

SETTING

Tertiary care hospital.

PATIENTS

Three hundred eighty-five consecutive patients who were admitted to the Johns Hopkins Hospital from November 11, 1990, through November 10, 1991, and treated for community-acquired pneumonia.

RESULTS

An atypical pathogen was identified in 29 of 385 adults (7.5%). A second pathogen was detected in 16 of 29 patients (55.2%) in whom an atypical pathogen was detected, compared with 13 of 137 patients (9.5%) in whom conventional bacterial pathogens were detected (odds ratio, 10.22; 95% confidence interval, 3.7 to 28.8; p<0.0001). During hospitalization, only four patients (13.8%) with detection of an atypical pathogen received at least 7 days of either a macrolide or tetracycline. No patient identified to have an atypical pathogen died. For patients who either provided paired sera or who died, 24 of 197 (12.2%) had atypical pathogens detected.

CONCLUSIONS

Despite vigorous study methods, atypical pathogens were uncommon in our hospitalized population. A second concurrent respiratory pathogen was identified for most patients with atypical pneumonia. Although macrolide use was rare in this patient population, mortality was zero for patients in whom an atypical pathogen was detected, affirming that macrolide-based therapy need not be routine in the therapeutic management of community-acquired pneumonia.

Comparative study of the clinical presentation of Legionella pneumonia and other community-acquired pneumonias

The aim of this study was to compare the clinical, biological, and radiologic features of presentation in the emergency ward of community-acquired pneumonia (CAP) by Legionella pneumophila (LP) and other community-acquired bacterial pneumonias to help in early diagnosis of CAP by LP. Three hundred ninety-two patients with CAP were studied prospectively in the emergency department of a 600-bed university hospital. Univariate and multivariate analyses were performed to compare epidemiologic and demographic data and clinical, analytical, and radiologic features of presentation in 48 patients with CAP by LP and 125 patients with CAP by other bacterial etiology (68 by Streptococcus pneumoniae, 41 by Chlamydia pneumoniae, 5 by Mycoplasma pneumoniae, 4 by Coxiella burnetii, 3 by Pseudomonas aeruginosa, 2 by Haemophilus influenzae, and 2 by Nocardia species. Univariate analysis showed that CAP by LP was more frequent in middle-aged, male healthy (but alcohol drinking) patients than CAP by other etiology. Moreover, the lack of response to previous beta-lactamic drugs, headache, diarrhea, severe hyponatremia, and elevation in serum creatine kinase (CK) levels on presentation were more frequent in CAP by LP, while cough, expectoration, and thoracic pain were more frequent in CAP by other bacterial etiology. However, multivariate analysis only confirmed these differences with respect to lack of underlying disease, diarrhea, and elevation in the CK level. We conclude that detailed analysis of features of presentation of CAP allows suspicion of Legionnaire's disease in the emergency department. The initiation of antibiotic treatment, including a macrolide, and the performance of rapid diagnostic techniques are mandatory in these cases.

Cefepime versus ceftriaxone for empiric treatment of hospitalized patients with community-acquired pneumonia. The Cefepime Study Group

Effective empiric treatment of pneumonia requires antibiotic coverage against gram-negative and gram-positive pathogens, including drug-resistant isolates. We compared the safety and efficacy of intravenous (i.v.) cefepime (2 g administered every 12 h) to those of i.v. ceftriaxone (1 g administered every 12 h) for the empiric treatment of hospitalized patients with community-acquired pneumonia. Of the 115 patients randomized to the study, 86 (cefepime recipients, n = 40; ceftriaxone recipients, n = 46) were evaluated for clinical efficacy (clinically evaluated patients). Favorable clinical outcomes (cure or improvement) were comparable among clinically evaluated patients in the cefepime and ceftriaxone treatment arms (95.0 versus 97.8%, respectively; 95% confidence interval for treatment difference [data for ceftriaxone group minus data for cefepime group], -5.1 to +10.8%). The most common bacteria isolated from patients in both treatment groups were Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. In clinically evaluated patients with a microbiologic response, all (100%) of the 32 pathogens from cefepime-treated patients and 97.4% (38 of 39) of the pathogens from ceftriaxone-treated patients were eradicated (documented or presumed eradication). The one persistent infection in the ceftriaxone group was caused by Pseudomonas fluorescens. Both treatments were well tolerated. Our data thus suggest that cefepime and ceftriaxone have comparable safety and efficacy for the treatment of pneumonia in hospitalized patients.

Identification of macrophage-specific infectivity loci (mil) of Legionella pneumophila that are not required for infectivity of protozoa

We have recently shown that many mutants of Legionella pneumophila exhibit similar defective phenotypes within both U937 human-derived macrophages and the protozoan host Acanthamoeba (L.-Y. Gao, O. S. Harb, and Y. Abu Kwaik, Infect. Immun. 65:4738-4746, 1997). These observations have suggested that many of the mechanisms utilized by L. pneumophila to parasitize mammalian and protozoan cells are similar, but our data have not excluded the possibility that there are unique mechanisms utilized by L. pneumophila to survive and replicate within macrophages but not protozoa. To examine this possibility, we screened a bank of 5,280 miniTn10::kan transposon insertion mutants of L. pneumophila for potential mutants that exhibited defective phenotypes of cytopathogenicity and intracellular replication within macrophage-like U937 cells but not within Acanthamoeba polyphaga. We identified 32 mutants with various degrees of defects in cytopathogenicity, intracellular survival, and replication within human macrophages, and most of the mutants exhibited wild-type phenotypes within protozoa. Six of the mutants exhibited mild defects in protozoa. The defective loci were designated mil (for macrophage-specific infectivity loci). Based on their intracellular growth defects within macrophages, the mil mutants were grouped into five phenotypic groups. Groups I to III included the mutants that were severely defective in macrophages, while members of the other two groups exhibited a modestly defective phenotype within macrophages. The growth kinetics of many mutants belonging to groups I to III were also examined, and these were shown to have a similar defective phenotype in peripheral blood monocytes and a wild-type phenotype within another protozoan host, Hartmannella vermiformis. Transmission electron microscopy of A. polyphaga infected by three of the mil mutants belonging to groups I and II showed that they were similar to the parent strain in their capacity to recruit the rough endoplasmic reticulum (RER) around the phagosome. In contrast, infection of macrophages showed that the three mutants failed to recruit the RER around the phagosome during early stages of the infection. None of the mil mutants was resistant to NaCl, and the dot or icm NaCl(r) mutants are severely defective within mammalian and protozoan cells. Our data indicated that in addition to differences in mechanisms of uptake of L. pneumophila by macrophages and protozoa, there were also genetic loci required for L. pneumophila to parasitize mammalian but not protozoan cells. We hypothesize that L. pneumophila has evolved as a protozoan parasite in the environment but has acquired loci specific for intracellular replication within macrophages. Alternatively, ecological coevolution with protozoa has allowed L. pneumophila to possess multiple redundant mechanisms to parasitize protozoa and that some of these mechanisms do not function within macrophages.

Introduction: Evolving needs in respiratory tract infections

Two issues that have become clinically relevant to the treatment of pneumonia over the past few years are the development of antibiotic resistance among respiratory pathogens and the increasing importance of the atypical respiratory pathogens---Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella spp. Resistance has become an important issue in Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus and Gram-negative rods. The ways by which bacteria become resistant to antibiotics include production of antibiotic-modifying enzymes, reduced access to target sites, efflux of antibiotic, change in the bacterial target site and the bypassing of inhibited pathways. In Streptococcus pneumoniae that are penicillin resistant, the mechanism is through alteration of the target site for penicillins (penicillin-binding proteins) and this may also confer resistance to some cephalosporins. Multidrug resistance has also been reported in some strains of pneumococci. Of particular concern is resistance to macrolides mediated by the ermAM gene, which also confers resistance to lincosamides and streptogramin-B drugs. In Staphylococcus aureus, resistance to virtually all beta-lactam drugs is mediated by acquisition of the mecA gene, which codes for the drug-resistant beta-lactam target PBP2a. Antimicrobials are now needed that have enhanced activity against aerobic Gram-negative rods, atypical respiratory pathogens and Gram-positive cocci.

Community-acquired pneumonia due to Escherichia coli

OBJECTIVE: To describe the features of community-acquired Escherichia coli pneumonia and to compare these patients with patients with pneumonia caused by other etiologic agents. PATIENTS AND METHODS: This prospective study was carried out at five medical institutions in three geographic locations---Pittsburgh, PA, Boston, MA and Halifax, NS. Pneumonia etiology was assigned, based on results of microbiological investigations, by a committee consisting of five investigators using rules established prior to the study. Demographic and clinical features and outcomes of patients with E. coli pneumonia were compared with those of pneumonia due to other microorganisms. RESULTS: Nineteen patients (9 (47.4%) blood culture positive) had pneumonia due to E. coli and 430 (69 (16.0%) blood culture positive) had pneumonia caused by other etiologic agents. E. coli was the second most common cause of bacteremic pneumonia. The E. coli patients were older, and more likely to be female, from a nursing home and confused compared with patients with pneumonia due to other microbial agents. They were more severely ill as measured by a validated pneumonia specific severity of illness scoring measure. Although there was no in-hospital mortality for the patients with E. coli pneumonia, the 90-day mortality was 21%. Thirty-two (7.4%) of the patients with pneumonia due to other agents died in hospital and the 90-day mortality rate was 13.5% (p NS). Eight of the 19 patients with E. coli pneumonia were admitted from a nursing home and an additional four patients (63.2%) were discharged to such a facility. In contrast, only 44 (10.2%) of the patients with pneumonia due to other agents were discharged to a nursing home (p<0.001). CONCLUSIONS: Patients diagnosed with E. coli pneumonia are frequently bacteremic. They are older than patients with pneumonia due to other etiologies, and more likely to be female, from a nursing home and severely ill. Despite the absence of in-hospital mortality, 21% of these patients died within 90 days of presentation.

Community-acquired pneumonia: can it be defined with claims data?

The use of administrative data to study pneumonia is limited because International Classification of Diseases, 9th revision, Clinical Modification (ICD9-CM) diagnosis codes do not specify whether pneumonia is community-acquired (CAP), a key clinical distinction. We classified 212 patients discharged with a diagnosis code for pneumonia as to whether or not they had CAP, using three administrative data-based systems (Diagnosis Related Groups (DRGs) alone, principal diagnosis alone, and a complex algorithm). We examined agreement with classification by clinician chart review. We also compared the length of stay (LOS) and mortality among the CAP populations identified with different methods. Agreement between the clinical review and the three administrative data methods ranged from 86 to 80%. Classification by DRG performed least well. Populations defined by claims data had similar mortality but shorter mean LOS (9.70, 9.40, and 7.91 days for the algorithm, principal diagnosis and DRG methods, respectively) than the clinically defined population (10.85 days). We conclude that studies of CAP using populations identified by claims may underestimate LOS.

Severe community-acquired pneumonia

Community-acquired pneumonia (CAP) is likely to be severe in the very elderly, and clinically significant in those with hepatic/ renal insufficiency, cardiopulmonary disease, or, impaired host defenses. Pathogens in mild, moderately severe, and severe CAP are the same. These pathogens determine prognosis, complications, and duration of therapy. Empiric antimicrobial therapy should be based on likely pathogens, not severity of illness which affects the potency but not spectrum of antibiotic selected.

The clinical benefit of in-hospital observation in 'low-risk' pneumonia patients after conversion from parenteral to oral antimicrobial therapy

OBJECTIVE

To assess the benefit of in-hospital observation in "low-risk" patients with community-acquired pneumonia.

DESIGN

Retrospective review of data from a prospective study.

SETTING

Teaching community hospital.

PATIENTS

We studied 717 consecutive, adult patients admitted to the hospital for pneumonia.

MEASUREMENTS AND RESULTS

One hundred forty-five patients were classified at low-risk for complications using previously studied criteria; 144 (99%) charts were available for review. Two patients had "obvious reasons for continued hospitalization" on the day of antibiotic conversion and were excluded. One hundred two patients were observed, and 40 were not observed in-hospital after switch to oral antibiotics. No patient from either group required medical intervention within 24 h after hospital discharge. Five "observed" patients (5%, 95% confidence interval [CI], 2 to 11%) returned to the emergency department, three (3%; 95% CI, 0 to 9%) with respiratory complaints. Two (2%; 95% CI, 0 to 7%) "observed" patients were admitted to the hospital with recurrent pneumonia. One (3%; 95% CI, 0 to 13%) "not observed" patient returned to the emergency department with a nonrespiratory complaint and was not admitted. No patient from either group died within 30-day clinical follow-up. The length of stay for the "observed" and "not observed" groups was 98+/-33 h and 83+/-49 h, respectively. The difference in length of stay was 15 h (95% CI, 3 to 27).

CONCLUSIONS

In-hospital observation for low-risk patients admitted with community-acquired pneumonia after switch from parenteral to oral antibiotics is of limited benefit, and elimination of this practice could potentially reduce length of stay by almost 1 day per patient. This could translate into a cost savings of $57,200 for the 22-month study period. These results require prospective validation in a larger study.

Practical considerations and guidelines for the management of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common condition which has a significant mortality. The management of a patient with CAP is centred around assessment and correction of gas exchange and fluid balance together with administration of appropriate antibiotics. Up to 10 different pathogens regularly cause CAP, of which Streptococcus pneumoniae is the most important. These different pathogens cannot be distinguished by clinical features or simple laboratory tests. Microbiological tests are slow and insensitive, so empirical therapy is necessary, at least initially. Accurate assessment of illness severity is the most important factor determining initial management, since this assists the decision of whether to admit the patient to hospital in addition to guiding antibiotic choice and route of administration. Two different approaches to severity assessment are outlined. Our antibiotic recommendation for empirical therapy for the patient managed at home and the previously fit patient admitted to hospital is amoxicillin. Amoxicillin/clavulanate plus a macrolide is our choice for the severely ill previously fit patient and a third-generation cephalosporin plus a macrolide is recommended for the severely ill patient with comorbidity. Alternative pathogens and specific treatment regimens are also described. There may be several causes of treatment failure, and in patients who fail to respond to therapy, it is essential to review all the initial clinical and laboratory information, which if necessary must be repeated.

Variations in antimicrobial use and cost in more than 2,000 patients with community-acquired pneumonia

PURPOSE

To assess the patterns of antimicrobial use, costs of antimicrobial therapy, and medical outcomes by institution in patients with community-acquired pneumonia.

PATIENTS AND METHODS

The route, dose, and frequency of administration of all antimicrobial agents prescribed within 30 days of presentation were recorded for 927 outpatients and 1328 inpatients enrolled in the Pneumonia Patient Outcomes Research Team (PORT) multicenter, prospective cohort study. Total antimicrobial costs were estimated by summing drug costs, using average wholesale price for oral agents and institutional acquisition prices for parenteral agents, plus the costs associated with preparation and administration of parenteral therapy. Thirty-day outcome measures were mortality, subsequent hospitalization for outpatients, and hospital readmission for inpatients.

RESULTS

Significant variation (P <0.05) in prescribing practices occurred for 17 of the 23 antimicrobial agents used in outpatients across 5 treatment sites, and for 18 of the 20 parenteral agents used in inpatients across 4 treatment sites. The median duration of antimicrobial therapy for treatment site ranged from 11 to 13 days for outpatients (P=0.01), and from 13 to 15 days for inpatients (P=0.49). The overall median cost of antimicrobial therapy was $12.90 for outpatients, and ranged from $10.80 to $58.90 among treatment sites (P <0.0001). The overall median cost of antimicrobial therapy was $228.70 for inpatients, and ranged from $183.70 to $315.60 among sites (P <0.0001). Mortality and hospital readmission for inpatients were not significantly different across sites after adjusting for baseline differences in patient demographic characteristics, comorbidity, and illness severity. Although subsequent hospitalization for outpatients differed by site, the rate was lowest for the site with the lowest antimicrobial costs.

CONCLUSION

Variations in antimicrobial prescribing practices by treatment site exist for outpatients and inpatients with community-acquired pneumonia. Although variation in antimicrobial prescribing practices across institutions results in significant differences in antimicrobial costs, patients treated at institutions with the lowest antimicrobial costs do not demonstrate worse medical outcomes.

Heterogeneity in the attachment and uptake mechanisms of the Legionnaires' disease bacterium, Legionella pneumophila, by protozoan hosts

Invasion and intracellular replication of Legionella pneumophila within protozoa in the environment plays a major role in the transmission of Legionnaires' disease. Intracellular replication of L. pneumophila within protozoa occurs in a rough endoplasmic reticulum (RER)-surrounded phagosome (Y. Abu Kwaik, Appl. Environ. Microbiol. 62:2022-2028, 1996). Since the subsequent fate of many intracellular pathogens is determined by the route of entry, we compared the mechanisms of attachment and subsequent uptake of L. pneumophila by the two protozoa Hartmannella vermiformis and Acanthamoeba polyphaga. Our data provide biochemical and genetic evidence that the mechanisms of attachment and subsequent uptake of L. pneumophila by the two protozoan hosts are, in part, different. First, uptake of L. pneumophila by H. vermiformis is completely blocked by the monovalent sugars galactose and N-acetyl-D-galactosamine, but these sugars partially blocked A. polyphaga. Second, attachment of L. pneumophila to H. vermiformis is associated with a time-dependent and reversible tyrosine dephosphorylation of multiple host proteins. In contrast, only a slight dephosphorylation of a 170-kDa protein of A. polyphaga is detected upon infection. Third, synthesis of H. vermiformis proteins but not of A. polyphaga proteins is required for uptake of L. pneumophila. Fourth, we have identified L. pneumophila mutants that are severely defective in attachment to A. polyphaga but which exhibit minor reductions in attachment to H. vermiformis and, thus, provide a genetic basis for the difference in mechanisms of attachment to both protozoa. The data indicate a remarkable adaptation of L. pneumophila to attach and invade different protozoan hosts by different mechanisms, yet invasion is followed by a remarkably similar intracellular replication within a RER-surrounded phagosome and subsequent killing of the host cell.

Microbiological and clinical aspects of infection associated with Stenotrophomonas maltophilia

The gram-negative bacterium Stenotrophomonas maltophilia is increasingly recognized as an important cause of nosocomial infection. Infection occurs principally, but not exclusively, in debilitated and immunosuppressed individuals. Management of S. maltophilia-associated infection is problematic because many strains of the bacterium manifest resistance to multiple antibiotics. These difficulties are compounded by methodological problems in in vitro susceptibility testing for which there are, as yet, no formal guidelines. Despite its acknowledged importance as a nosocomial pathogen, little is known of the epidemiology of S. maltophilia, and although it is considered an environmental bacterium, its sources and reservoirs are often not readily apparent. Molecular typing systems may contribute to our knowledge of the epidemiology of S. maltophilia infection, thus allowing the development of strategies to interrupt the transmission of the bacterium in the hospital setting. Even less is known of pathogenic mechanisms and putative virulence factors involved in the natural history of S. maltophilia infection and this, coupled with difficulties in distinguishing colonization from true infection, has fostered the view that the bacterium is essentially nonpathogenic. This article aims to review the current taxonomic status of S. maltophilia, and it discusses the laboratory identification of the bacterium. The epidemiology of the organism is considered with particular reference to nosocomial outbreaks, several of which have been investigated by molecular typing techniques. Risk factors for acquisition of the bacterium are also reviewed, and the ever-expanding spectrum of clinical syndromes associated with S. maltophilia is surveyed. Antimicrobial resistance mechanisms, pitfalls in in vitro susceptibility testing, and therapy of S. maltophilia infections are also discussed.

Pneumococcal community-acquired pneumonia in 148 hospitalized adult patients

In a previous prospective study, Streptococcus pneumoniae was identified as the causative agent in 148 (42.8%) of 346 adult patients hospitalized over the course of one year with community-acquired pneumonia (CAP) in the Soroka Medical Center, Beer-Sheva, Israel. The present study characterizes those cases in which Streptococcus pneumoniae was the only pathogen and those in which additional etiological agents were identified. Pneumococcal CAP was diagnosed by standard blood cultures or positive serological tests by one of two laboratory methods. In 100 (67.6%) patients, at least one other etiological agent of CAP was identified in addition to Streptococcus pneumoniae. Compared with patients who were not infected by Streptococcus pneumoniae, patients with Streptococcus pneumoniae CAP were older and had a higher rate of comorbidity (39.5% vs. 29.8%). Streptococcus pneumoniae CAP had a more severe clinical course and a higher mortality rate, especially when Streptococcus pneumoniae was the only pathogen. Community-acquired pneumonia due to Streptococcus pneumoniae only was more similar in its clinical manifestations to classic typical pneumococcal pneumonia. When an additional etiological agent was identified, the clinical characteristics could not be distinguished from those of atypical pneumonia. It is concluded that Streptococcus pneumoniae remains the principal cause of CAP in this region. The frequency of additional etiological agents of CAP and the difficulty in differentiating clinically between cases due to Streptococcus pneumoniae only and those due to Streptococcus pneumoniae plus other organisms necessitates initial empirical treatment that covers Streptococcus pneumoniae as well as other causative agents of atypical pneumonia.

Community-acquired pneumonia in the elderly. Clinical and nutritional aspects

Community-acquired pneumonia (CAP) in the elderly has a different clinical presentation than CAP in other age groups. Confusion, alteration of functional physical capacity, and decompensation of underlying illnesses may appear as unique manifestations. Malnutrition is also an associated feature of CAP in this population. We undertook a study to assess the clinical and nutritional aspects of CAP requiring hospitalization in elderly patients (over 65 yr of age). One hundred and one patients with pneumonia, consecutively admitted to a 1,000-bed teaching hospital over an 8-mo period, were studied (age: 78 +/- 8 yr, mean +/- SD). Nutritional aspects and the mental status of patients with pneumonia were compared with those of a control population (n = 101) matched for gender, age, and date of hospitalization. The main symptoms were dyspnea (n = 71), cough (n = 67), and fever (n = 64). The association of these symptoms with CAP was observed in only 32 patients. The most common associated conditions were cardiac disease (n = 38) and chronic obstructive pulmonary disease (COPD) (n = 30). Seventy-seven (76%) episodes of pneumonia were clinically classified as typical and 24 as atypical. There was no association between the type of isolated microorganism and the clinical presentation of CAP, except for pleuritic chest pain, which was more common in pneumonia episodes caused by classical microorganisms (p = 0.02). This was confirmed by a multivariate analysis (relative risk [RR] = 11; 95% confidence interval [CI]: 1.7 to 65; p = 0.0099). The prevalence of chronic dementia was similar in the pneumonia cohort (n = 25) and control group (n = 18) (p = 0.22). However, delirium or acute confusion were significantly more frequent in the pneumonia cohort than in controls (45 versus 29 episodes; p = 0.019). Only 16 patients with pneumonia were considered to be well nourished, as compared with 47 control patients (p = 0.001). Kwashiorkor-like malnutrition was the predominant type of malnutrition (n = 65; 70%) in the pneumonia patients as compared with the control patients (n = 31; 31%) (p = 0.001). The observed mortality was 26% (n = 26). Pleuritic chest pain is the only clinical symptom that can guide an empiric therapeutic strategy in CAP (typical versus atypical pneumonia). Both delirium and malnutrition were very common clinical manifestations of CAP in our study population.

Recurrence of pneumonia in middle-aged and elderly adults after hospital-treated pneumonia: aetiology and predisposing conditions

In order to investigate the predisposing conditions and aetiologic agents in patients with recurrent pneumonia, we prospectively studied 653 immunocompetent patients, 50-85 years of age, who had been treated in hospital for community-acquired pneumonia. After an average patient follow-up period of 32 months, 11 variables were examined for association with the following end points: death, recurrence of pneumonia and recurrence of pneumococcal pneumonia. During the follow-up period there were 171 episodes of pneumonia in 115 of the 653 patients, and 52 deaths (all causes). Multivariate analysis showed that age, male sex, congestive heart failure and presence of other chronic diseases were significantly associated with higher mortality. Age and chronic pulmonary disease were associated with recurrence of pneumonia. The major aetiologic agents were Streptococcus pneumoniae (26%), Haemophilus influenzae (11%) and Moraxella catarrhalis (6%). We conclude that pneumonia recurrences are common in middle-aged and elderly patients after treatment in hospital for community-acquired pneumonia. The recurrence risk is higher in elderly patients, and in those with chronic pulmonary diseases. Given the prominence of H. influenzae and M. catarrhalis found in the present study, these organisms should always be considered when choosing the initial antibiotic in patients with recurrent pneumonia.

Utilization of similar mechanisms by Legionella pneumophila to parasitize two evolutionarily distant host cells, mammalian macrophages and protozoa

The Legionnaires' disease bacterium, Legionella pneumophila, is an intracellular pathogen of humans that is amplified in the environment by intracellular multiplication within protozoa. Within both evolutionarily distant hosts, the bacterium multiplies in a rough endoplasmic reticulum-surrounded phagosome that is retarded from maturation through the endosomal-lysosomal degradation pathway. To gain an understanding of the mechanisms utilized by L. pneumophila to invade and replicate within two evolutionarily distant hosts, we isolated a collection of 89 mini-Tn10::kan insertion mutants that exhibited defects in cytotoxicity, intracellular survival, and replication within both U937 macrophage-like cells and Acanthamoeba polyphaga. Interestingly, the patterns of defects in intracellular survival and replication of the mutants within both host cells were highly similar, and thus we designated the defective loci in these mutants pmi (for protozoan and macrophage infectivity loci). On the basis of their ability to attach to host cells and their growth kinetics during the intracellular infection, the mutants were grouped into five groups. Groups 1 and 2 included 41 mutants that were severely defective in intracellular survival and were completely or substantially killed during the first 4 h of infection in both host cells. Three members of group 1 were severely defective in attachment to both U937 cells and A. polyphaga, and another four mutants of group 1 exhibited severe defects in attachment to A. polyphaga but only a mild reduction in their attachment to U937 cells. Four members of groups 1 and 2 were serum sensitive. Intracellular replication of mutants of the other three groups was less defective than that of mutants of groups 1 and 2, and their growth kinetics within both host cells were similar. The mutants were tested for several other phenotypes in vitro, revealing that 14 of the pmi mutants were resistant to NaCl, 3 had insertions in dot or icm, 3 were aflagellar, 12 were highly intolerant to a hyperosmotic medium, and one failed to grow in a minimal medium. Our data indicated that similar mechanisms are utilized by L. pneumophila to replicate within two evolutionarily distant hosts. Although some mechanisms of attachment to both host cells were similar, other distinct mechanisms were utilized by L. pneumophila to attach to A. polyphaga. Our data supported the hypothesis that preadaptation of L. pneumophila to infection of protozoa may play a major role in its ability to replicate within mammalian cells and cause Legionnaires' disease.

LOWER RESPIRATORY TRACT INFECTIONS IN ELDERLY PATIENTS WITH ASTHMA

Infection plays a significant role in the morbidity and mortality of the elderly. One population in which infection has not been adequately studied is the elderly asthmatic. This article examines the problems of lower respiratory tract infections in elderly asthmatics in the context of their host defenses, the severity of infection, and their risk of infection with specific organisms. The role of infection in the pathogenesis of asthma and consideration of prophylaxis and therapy are presented.

In vitro activity of clarithromycin alone and in combination with ciprofloxacin or levofloxacin against Legionella spp.: enhanced effect by the addition of the metabolite 14-hydroxy clarithromycin

Clarithromycin is metabolized to an active metabolite, 14-hydroxy clarithromycin. These compounds have demonstrated excellent in vitro activity against Legionella species, with both agents having significantly lower MICs than erythromycin. Using a checkerboard assay, the activity of clarithromycin and its hydroxy metabolite, alone and in combination, was examined against 41 Legionella organisms. The activity of clarithromycin and 14-hydroxy clarithromycin, in a 2:1 ratio, plus ciprofloxacin or levofloxacin was also determined. Activity of the antibiotic combinations was determined by calculating the fractional inhibitory concentration index. An agar dilution method using buffered charcoal yeast extract media was used for susceptibility and synergy testing. An inoculum of 10(4) CFU/spot was used, with all plates incubated at 35 degrees C for 48 h. The MIC90 for clarithromycin or 14-hydroxy clarithromycin alone was 0.5, versus 0.25 microgram/mL for the combination. Additive effects were observed with clarithromycin and its hydroxy metabolite for 61% of the Legionella species, with fractional inhibitory concentration indices ranging from 0.63 to 1.25. The 14-hydroxy metabolite significantly increased the activity of both fluoroquinolone/clarithromycin combinations. Based on these data, in vitro susceptibility testing of agents such as clarithromycin should be reevaluated to account for the activity of active metabolites.

Prognostic factors of severe Legionella pneumonia requiring admission to ICU

Despite the fact that the epidemiology of community-acquired pneumonia and nosocomial Legionella infection is well known, there are no specific reports dealing with severe cases of Legionella pneumophila pneumonia admitted to intensive care units. We undertook a prospective study upon 84 patients with a reliable diagnosis of L. pneumophila pneumonia that required ICU admission. The study assessed the prognostic factors, clinical, radiological and outcome variables of both nosocomial (n = 33) and community-acquired (n = 51) cases of L. pneumophila pneumonia. The following variables were more common in nosocomial acquired as compared to community-acquired Legionella pneumonia: Chronic obstructive pulmonary disease (COPD) (64 versus 41%), cardiac disease (39 versus 10%), chronic renal failure (21 versus 4%), alcoholism (54 versus 18%), septic shock (33 versus 16%), and unilateral chest X-ray involvement (61 versus 39%). The crude mortality rate in this study was 30% (25 of 84) with no differences when comparing mortality between nosocomial (9, 27%) to community-acquired (16, 31%) types. The univariate analysis showed that cardiac disease, diabetes mellitus, creatinine > or = 1.8 mg/dl, septic shock, chest X-ray extension, mechanical ventilation, hyponatremia < or = 136 mEq/L, PACO2/FIO2 < 130, and blood urea levels > or = 30 mg/dl were factors related to poor outcome. On the other hand, the following two variables were related to better outcome: adequate treatment for Legionella and pneumonia improvement. The logistic regression analysis demonstrated that APACHE II score > 15 at admission (RR: 11.5; 95% CI 1.75 to 76.1; p = 0.025), and serum Na levels < or = 136 (RR: 21.3; 95% CI 1.11 to 408; p = 0.023), were the only independent factors related to death. On the other hand, improving pneumonia is associated with better outcome in Legionnaires' disease than for patients not having improving pneumonia (RR: 0.019; 95% CI: 0.036 to 0.106; p < 0.0001). A better understanding of the prognostic factors in cases of severe Legionella pneumonia will optimize our therapeutic approach in this disease and help to decrease both its mortality and morbidity rates.

Sparfloxacin versus cefaclor in the treatment of patients with community-acquired pneumonia: a randomized, double-masked, comparative, multicenter study

Community-acquired pneumonia remains an important infectious disease problem, with more than 4 million cases occurring in the United States annually. Although Streptococcus pneumoniae remains the most commonly identified organism, a variety of bacterial and nonbacterial pathogens may be involved. Hospitalization is unnecessary in most cases, and oral antibiotic therapy is common. In the majority of cases, the etiology of pneumonia is unknown at the time of presentation, necessitating the use of empiric therapy. Quinolones have not been utilized in this setting in the past because of their inconsistent coverage of S pneumoniae. Sparfloxacin (RP 64206) is a broad-spectrum fluoroquinolone with excellent activity in vitro against the majority of bacteria involved in community-acquired pneumonia, including pneumococcus. We therefore studied the efficacy and safety of sparfloxacin compared with the second-generation cephalosporin cefaclor as empiric therapy for patients with community-acquired pneumonia in a double-masked, double-dummy, multicenter trial. Three hundred thirty patients aged 18 years or older with community-acquired pneumonia suspected of being bacterial in etiology were enrolled at 74 centers in the United States from June 1, 1992, to March 4, 1995. Patients meeting the inclusion criteria were randomized to receive 10 days of either sparfloxacin 400 mg orally once followed by sparfloxacin 200 mg orally daily (n = 168), or cefaclor 500 mg orally every 8 hours (n = 162). There were no significant differences between groups with regard to baseline characteristics. Patients were followed up serially at 4 +/- 1 days, 20 +/- 3 days, and 38 +/- 7 days after the beginning of therapy. Patients were evaluated for clinical response, clinical recurrence of infection, and eradication of baseline pathogens. The primary efficacy variable was the clinical response (cured or improved) in the subgroup of patients meeting the definition of clinically assessable. Responses were also evaluated in the intent-to-treat population. In the intent-to-treat population, 35.7% of patients receiving sparfloxacin were clinically cured, compared with 32.1% of patients receiving cefaclor. Clinical successes (patients clinically cured plus improved) were also comparable (72.6% of patients in the sparfloxacin group and 71.0% of patients in the cefaclor group). Similar clinical success rates were noted using only the clinically assessable population (primary efficacy variable). Forty-four percent of patients receiving sparfloxacin and 39.1% of patients receiving cefaclor were clinically cured. In the sparfloxacin group, 86.6% of patients were clinical successes, compared with 84.4% of patients in the cefaclor group. Microbiologic cures were comparable in both groups. There was no difference in the incidence of recurrence of infection or superinfection. Adverse events thought to be due to study drug occurred equally in both groups (14.3% in the sparfloxacin group vs 14.8% in the cefaclor group). Results show that sparfloxacin is a safe and effective empiric therapy for patients with community-acquired pneumonia and is comparable to cefaclor.

A multicenter, randomized study comparing the efficacy and safety of intravenous and/or oral levofloxacin versus ceftriaxone and/or cefuroxime axetil in treatment of adults with community-acquired pneumonia

Five hundred ninety patients were enrolled in a prospective, multicenter, randomized trial comparing the efficacy and safety of 7 to 14 days of levofloxacin treatment with that of ceftriaxone and/or cefuroxime axetil in the management of community-acquired pneumonia in adults. Patients received either intravenous and/or oral levofloxacin (500 mg once daily) or the comparative agents, parenteral ceftriaxone (1 to 2 g once to twice daily) and/or oral cefuroxime axetil (500 mg twice daily). Erythromycin or doxycycline could be added to the comparator arm at the investigator's discretion. The decision to use an intravenous or oral antimicrobial agent for initial therapy was made by the investigator. Clinical and microbiological evaluations were completed at the baseline, during treatment, 5 to 7 days posttherapy, and 3 to 4 weeks posttherapy. Four hundred fifty-six patients (226 given levofloxacin and 230 administered ceftriaxone and/or cefuroxime axetil) were evaluable for clinical efficacy. Streptococcus pneumoniae and Haemophilus influenzae were isolated in 15 and 12%, respectively, of clinically evaluable patients. One hundred fifty atypical pathogens were identified: 101 were Chlamydia pneumoniae, 41 were Mycoplasma pneumoniae, and 8 were Legionella pneumophila. Clinical success at 5 to 7 days posttherapy was superior for the levofloxacin group (96%) compared with the ceftriaxone and/or cefuroxime axetil group (90%) (95% confidence interval [CI] of -10.7 to -1.3). Among patients with typical respiratory pathogens who were evaluable for microbiological efficacy, the overall bacteriologic eradication rates were superior for levofloxacin (98%) compared with the ceftriaxone and/or cefuroxime axetil group (85%) (95% CI of -21.6 to -4.8). Levofloxacin eradicated 100% of the most frequently reported respiratory pathogens (i.e., H. influenzae and S. pneumoniae) and provided a >98% clinical success rate in patients with atypical pathogens. Both levofloxacin and ceftriaxone-cefuroxime axetil eradicated 100% of the S. pneumoniae cells detected in blood culture. Drug-related adverse events were reported in 5.8% of patients receiving levofloxacin and in 8.5% of patients administered ceftriaxone and/or cefuroxime axetil. Gastrointestinal and central and peripheral nervous system adverse events were the most common events reported in each treatment group. In conclusion, these results demonstrate that treatment with levofloxacin is superior to ceftriaxone and/or cefuroxime axetil therapy in the management of community-acquired pneumonia in adults.

Comparison of cefdinir and cefaclor in treatment of community-acquired pneumonia

Six hundred ninety patients were enrolled in a multicenter, randomized, double-blind trial comparing the efficacy and safety of cefdinir with those of cefaclor in the treatment of community-acquired pneumonia. Patients received either 10 days of treatment with cefdinir (n = 347) at 300 mg twice daily or 10 days of treatment with cefaclor (n = 343) at 500 mg three times daily. Microbiological assessments were performed on sputum specimens obtained at admission and at the two posttherapy visits, if available. Respiratory tract pathogens were isolated from 538 (78%) of 690 patient admission sputum specimens, with the predominant pathogens being Haemophilus parainfluenzae, Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus. The microbiological eradication rates at the test-of-cure visit were 92% (238 of 260 pathogens) and 93% (245 of 264 pathogens) for the evaluable patients treated with cefdinir and cefaclor, respectively. A satisfactory clinical response (cure plus improvement) was achieved in 89% (166 of 187) and 86% (160 of 186) of the evaluable patients treated with cefdinir and cefaclor, respectively. Except for the incidence of diarrhea, adverse event rates while on treatment were equivalent between the two treatment groups. Diarrhea incidence during therapy was higher for patients treated with cefdinir (13.7%) than for patients treated with cefaclor (5.3%). These results indicate that cefdinir is effective and safe in the treatment of patients with pneumonia.

[Community-acquired pneumonia (CAP) with hospital treatment. The value of the clinical picture and complementary exams in predicting its etiology]

We studied 162 patients with community-acquired pneumonia admitted for hospital treatment, in order to determine the utility of clinical and ancillary examinations for predicting etiology and guiding the most appropriate empirical treatment. Acute first appearance of symptoms, purulent expectoration, chest sounds indicating lung condensation, pleuritic chest pain and leukocytosis over 12,500/ml were statistically significant in differentiating typical pneumonias from those with atypical behavior patterns. The last two features were the most relevant according to multivariate analysis. We conclude that careful taking of case histories and basic blood testing continue to be relevant and must not be considered anachronistic for the differential diagnosis of community-acquired pneumonias.

Rapid detection of pneumococcal antigen in lung aspirates: comparison with culture and PCR technique

Detection of pneumococcal antigen has been used to increase the rate of diagnosis of pneumococcal pneumonia. The present study was designed to determine the value of rapid detection of pneumococcal antigen in samples obtained by transthoracic needle aspiration (TNA) from patients with community-acquired pneumonia (CAP) in a comparative analysis with culture and polymerase chain reaction (PCR). Pneumococcal antigen was detected by latex agglutination. One hundred and ten consecutive patients diagnosed with CAP underwent TNA. Patients were grouped, according to PCR, culture and serological results, into pneumococcal pneumonia (n = 18), other known aetiology (n = 67) and unknown aetiology (n = 25). In patients with pneumococcal pneumonia, antigen was detected in 17 (94.4%) cases. Antigen was detected in one and nine patients with pneumonia of other known or unknown aetiologies, respectively, yielding a specificity of 89.1%. In conclusion, detection of pneumococcal antigen on samples obtained by TNA from patients with CAP provides a sensitive and specific diagnosis of Streptococcus pneumoniae infection. Furthermore, its rapid results would reduce the dependence on empirical treatments.

Microbial etiology of acute community-acquired pneumonia in adult hospitalized patients in Yaounde-Cameroon

OBJECTIVE: To determine the microbial etiology of acute community-acquired pneumonia in Yaoundé. METHODS: Ninety-one consecutive adult patients admitted to hospital for radiologically confirmed acute community-acquired pneumonia were studied prospectively. Sputum microscopy and culture, blood cultures, pneumococcal antigen detection in serum and serologic analysis for agents of atypical pneumonia and for human immunodeficiency virus (HIV) were performed for most patients. RESULTS: There were 65 men and 26 women, mean age 36.5 years. Of 91 patients, 70.3% had at least one predisposing factor and 21.7% (20 of 81) were seropositive for HIV. A microbial etiology was identified in 48 (52.7%) cases. A single pathogen was identified in 42 (85.4%) and double pathogens in six (14.6%). Bacteremia occurred in 12 of 81 patients and was significantly more common in HIV-seropositive than in HIV-seronegative patients. Streptococcus pneumoniae was the commonest causative agent, identified in 22 of 91 (24.2%) patients, 10 of whom were bacteremic. Atypical pathogens were diagnosed in 14 of 65 patients with serologic tests. Mycoplasma pneumoniae and Coxiella burnetii were diagnosed in six of 65 (9.2%) cases each, and Chlamydia pneumoniae in three (4.6%) patients. Mycoplasma pneumoniae and Chlamydia pneumoniae occurred as a dual infection in one case. Seven of 91 patients died, and death was not associated with any particular etiology. CONCLUSION: Streptococcus pneumoniae remains the predominant etiologic pathogen of community-acquired pneumonia. For this reason, and also because ampicillin used empirically to treat patients with this disease in the same setting has been shown to be efficacious, we propose the use of an aminopenicillin in the initial treatment of acute community-acquired pneumonia in adults in Yaoundé. However, patients who fail to respond clinically to such treatment should benefit from either a macrolide or a tetracycline in order to cover for atypical pathogens.

Legionnaire's disease during pregnancy: a case presentation and review of the literature

Acute pneumonia complicating pregnancy can have serious consequences for both the mother and the fetus. Streptococcus pneumoniae remains the most common bacterial pathogen, but Legionella pneumophila must be considered as well, especially in severe multisystem disease. With severe disease, premature delivery may occur as has been described in the only previous report of Legionnaire's disease during pregnancy. We present here the first report of Legionnaire's disease in pregnancy, resulting in the term delivery of a healthy infant. Also presented is an extensive review of the literature.

Survey of physicians concerning the use of chest radiography in the diagnosis of pneumonia in out-patients

OBJECTIVE

To determine how physicians use chest radiography in the diagnosis of pneumonia in ambulatory patients.

STUDY POPULATION

A convenience sample of 176 Nova Scotia family physicians and internists selected to represent all geographic areas of the province proportional to population. STUDY INSTRUMENT: A 35-item questionnaire covering demographics, experience with out-patients with pneumonia, use of chest radiographs to make this diagnosis and factors that were considered important in the decision to perform initial and follow-up chest radiographs. Two skill-testing questions were also included.

RESULTS

One hundred and fourteen of 176 (64.7%) responded; 88% had treated out-patients with pneumonia in the previous three months. Fifty-seven per cent of physicians requested chest radiographs on 90% to 100% of out-patients in whom they had made a clinical diagnosis of pneumonia. These physicians were more likely to be internists and to have graduated before 1970. Factors that ranked most important in the decision to request the initial chest radiograph were clinical appearance, respiratory distress and physical findings, while age and smoking history contributed most to the decision to perform a follow-up chest radiograph.

CONCLUSIONS

There is considerable variability among physicians in requesting chest radiographs on out-patients with a clinical diagnosis of pneumonia. Physician and patient factors contribute to this variability.

Atypical respiratory pathogens

The main atypical pathogens in respiratory tract infections are classified on the basis of their ability to cause atypical pneumonia. This is not a well-defined clinical entity, and it is evident that atypical pathogens can sometimes cause 'typical' pneumonias and vice versa. This emphasizes the need for microbiological diagnosis, since it affects the selection of proper treatment, in which beta-lactam antibiotics and aminoglycosides are not effective. Moreover, mixed infections caused by atypical and typical pathogens together are common. At this moment rapid and sensitive diagnostic methods are lacking. Besides numerous viruses, the main bacterial pathogens causing atypical pneumonias are Mycoplasma pneumoniae, two chlamydial species, Chlamydia pneumoniae and C. psittaci, one rickettsia, Coxiella burnetti, and several Legionella species. The majority of these pathogens cause upper respiratory tract infections more often than overt pneumonias. An atypical agent, Chlamydia pneumoniae, has also been associated with chronic inflammatory conditions in the cardiovascular system. The most recently discovered pathogen in atypical pneumonias is a hantavirus causing hantavirus pulmonary syndrome.

Haemophilus influenzae infections in adults: a pathogen in search of respect

Despite the success of Haemophilus influenzae type b vaccines in preventing bacterial disease in children, H influenzae remains a common pathogen in adult patients in the United States and Europe. At least half of invasive H influenzae infections are caused by nontypable strains. The spectrum of diseases includes sinusitis, pneumonia, otitis media, epiglotitis, and meningitis. An etiologic diagnosis is most reliably established by positive cultures from a normally sterile site. Although resistance to ampicillin and amoxicillin has steadily increased in clinical H influenzae isolates during the past two decades, a variety of other antimicrobial agents are available for the treatment of infections caused by this bacterium.

[Community acquired pneumonia. Reliability of the criteria for deciding ambulatory treatment]

To determine whether criteria for not admitting community-acquired pneumonia (CAP) patients diagnosed in the emergency room are appropriate, and to characterize the symptoms, etiology and course of CAP. This one-year prospective, protocol study of immunocompetent CAP patients diagnosed in the emergency room of our hospital enrolled patients not considered to require hospital admission according to the recommendations of the Spanish Society of Respiratory Disease (SEPAR). Medical histories, chest X-rays and blood analysis were obtained for all patients. Blood cultures were analyzed for antibodies against Legionella pneumophila, Mycoplasma pneumoniae, Coxiella burnetii, Chlamydia pneumoniae, Chlamydia psittaci and influenza virus types A and B. The patients received erythromycin for 14 days and were regularly checked by the pulmonologist in the outpatient clinic until signs and symptoms had disappeared. One hundred six patients were enrolled. Mean age was 36 +/- 13 years. Only 3 patients had to be admitted to hospital, after which outcome was good. The main symptoms were fever (106, 100%) and cough (83, 78%). In 46 (43.4%) chest sounds were normal. Microbiologic diagnoses were achieved for 28 (26.4%) and Coxiella burnetii was the agent most often found (19, 17.9%). Outcome was good in all cases, with faster disappearance of symptoms than of radiological signs. The SEPAR criteria for admitting patients with CAP are appropriate. The clinical symptoms of such patients are non specific, a noteworthy finding being that many patients had normal chest sounds. Coxiella burnetii was the most common causative agent. Both clinical and radiological outcomes were excellent.

Role of oral antibiotics in treatment of community-acquired lower respiratory tract infections

Amoxicillin/clavulanic acid has been one of the first choice treatments for community-acquired lower respiratory tract infection since its introduction nearly 15 years ago. Since then, it has become the "gold standard" against which most new oral antimicrobials are compared, but none of these newer agents has demonstrated a superior efficacy. To the contrary, two recent studies comparing amoxicillin/clavulanic acid with azithromycin, cefixime, or ciprofloxacin in the treatment of acute exacerbations of chronic bronchitis have demonstrated a higher efficacy rate for amoxicillin/clavulanic acid.

Efficacies of cefotaxime and ceftriaxone in a mouse model of pneumonia induced by two penicillin- and cephalosporin-resistant strains of Streptococcus pneumoniae

We previously demonstrated the efficacy of ceftriaxone (CRO), at 50 mg/kg of body weight every 12 h, against a highly penicillin-resistant (MIC, 4 micrograms/ml) Streptococcus pneumoniae strain with low-level resistance to CRO (MIC, 0.5 microgram/ml) in a leukopenic-mouse pneumonia model (P. Moine, E. Vallée, E. Azoulay-Dupuis, P. Bourget, J.-P. Bédos, J. Bauchet, and J.-J. Pocidalo, Antimicrob. Agents Chemother. 38:1953-1958, 1994). In the present study, we assessed the activity of CRO versus those of cefotaxime (CTX) and amoxicillin (AMO) against two highly penicillin- and cephalosporin-resistant S. pneumoniae strains (P40422 and P40984) (MICs of 2 and 8 for penicillin, 2 and 4 for AMO, and 4 and 8 for CRO or CTX, respectively). Against both strains, a greater than an 80% cumulative survival rate was observed with CRO at a dose of 100 or 200 mg/kg every 12 h (dose/MIC ratio, 25). With CTX, a high dosage of 400 mg/kg (dose/MIC ratio, 100 or 50) administered every 8 h (TID) was needed to protect 66 and 75% of the animals, respectively, with no statistically significant differences versus CRO. Against the P40422 strain, CRO (100 mg/kg) produced the greatest bactericidal effect, from the 8th to the 24th hour after a single injection (1.8-log-unit reduction over 24 h), and the fastest bacterial pulmonary clearance during treatment; with CTX, only multiple injections at a high dosage, i.e., 400 mg/kg TID, demonstrated a significant bactericidal effect. AMO in a high dosage, 400 mg/kg (dose/MIC ratio, 200) TID, showed good activity only against the P40422 strain. Despite the identical MICs of CTX and CRO, the longer time (3.6 to 4.6 h) that serum CRO concentrations remained above the MICs for the pathogens at a dose of 100 mg/kg resulted in greater efficacy versus CTX against highly penicillin- and cephalosporin-resistant S. pneumoniae strains.