Community-acquired pneumonia: An overview

Community-acquired pneumonia (CAP) accounts for a significant number of hospitalizations and outpatient visits, as well as substantial health care expenditures. CAP is particularly common among the elderly who account for more than 90% of deaths due to pneumonia. Streptococcus pneumoniae is believed to be the most common microbial etiology of CAP, but recent studies suggest that the atypical pathogens may be more common than previously thought, particularly among ambulatory patients. Recent studies have provided data regarding risk of mortality and process of care and outcomes. Increasing resistance among strains of S. pneumoniae has impacted the approach to the empiric therapy of CAP. The Infectious Diseases Society of America published guidelines for the evaluation and management of CAP this past year. Pathogen-specific therapy guided by the results of sputum gram stain and culture is emphasized. Despite enthusiasm for practice guidelines and clinical pathways, there remains insufficient published data to determine their impact on quality and cost of care in patients with CAP.     

Comparative study of clinical features of typical and atypical pneumonias]

We prospectively analyzed the clinical and laboratory features of 74 patients with community-acquired pneumonia who required hospitalization between May 1996 and October 1997. Typical pathogens were identified in 47, and atypical pathogens in 27. The average age was higher in patients affected by typical pathogens (73.9 years), than in patients affected by atypical pathogens (50.9 years). Univariable analysis found that atypical pneumonias were more frequent in healthy patients than typical pneumonias. Moreover, the presence of relatives with symptoms of airway infection, headache, and earache was more common among the patients with atypical pneumonias, while leukocytosis and elevated C-reactive protein levels were more frequent among patients with typical pneumonias. Typical pathogens accounted for up to 79.6% of the cases of pneumonia with in older patients (aged 60 years or more), whereas atypical pathogens accounted for up to 80% of the cases of pneumonia in younger patients (aged under 60 years). This difference was statistically significant. Of all 74 patients, 39 (52.7%) were afflicted by severe community-acquired pneumonia, as categorized by American Thoracic Society guidelines. The most common pathogen among these patients was Streptococcus pneumoniae. Legionella was one of the top four. Selection of the initial antimicrobial treatment is an important clinical decision that should be made on the basis of clinical features at admission, age, and severity of the patient's illness.     

Infective agents and cardiovascular disease

As a consequence of seminal laboratory and experimental work conducted in the 1970s, infections have recently been recognized among possible risk factors for atherosclerosis and its clinical cardiovascular disease manifestations. The infectious hypothesis also relates to modern atherogenesis theories that consider the crucial role of inflammation in the initial development as well as in the natural history of the atherosclerotic plaque. During the last 2 decades, numerous clinical and epidemiologic studies have explored the association between markers of chronic infections in relation to a variety of clinical and subclinical cardiovascular disease outcomes. These studies have focused on a variety of agents including herpesvirus (especially cytomegalovirus), Chlamydia pneumonia, Helicobacter pylori, and periodontal pathogens, and have produced inconsistent results. Some of the limitations and methodological issues in interpreting the existing epidemiologic evidence are discussed in this article. In addition, other supporting evidence is presented here, including pathology studies documenting the presence of infectious agents' DNA in atherosclerotic plaque tissue and experimental infection models in animal studies. Areas for future research are discussed in light of the strengths and limitations of the existing evidence.     

Uncommon respiratory pathogens

PURPOSE OF REVIEW: In many cases, the specific pathogen responsible for a respiratory infection is not identified and can lead to improper medical treatment, increased duration of illness, and possibly contributes to the development of antibiotic resistance. Molecular-based diagnostic methodologies have significantly improved our ability to identify common respiratory pathogens; these techniques are not useful, however, when a novel pathogen is responsible for the infection and clinicians must rely on differential diagnosis for the treatment of patients. RECENT FINDINGS: New pathogens previously not associated with human infections have been identified in the past few years. In addition, new strains of bacteria and viruses have emerged as the causative agents of pneumonia and acute respiratory distress. Protozoans and saprophytic fungi, which are not normally associated with respiratory infection, have also emerged as respiratory pathogens particularly in individuals with AIDS or in those who are otherwise immunocompromised. SUMMARY: This review discusses the recent literature on newly described respiratory pathogens as well as opportunistic pathogens that can infect the respiratory system of immunocompromised individuals. The studies referenced here reveal the need for expanded laboratory tests and highly trained microbiologists in clinical laboratories worldwide.     

The usefulness of induced sputum in the diagnosis of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome

Thirty-two patients with or suspected of having the acquired immunodeficiency syndrome were evaluated for opportunistic lung infection using examination of sputum induced by inhalation of 3% saline. The specimens obtained were stained with Giemsa stain and examined for Pneumocystis carinii. Smears of sputum were also appropriately stained and examined for acid-fast organisms and fungi, as well as cultured for these organisms. Patients whose sputum did not contain P. carinii had bronchoscopy within 24 h of sputum induction. Twenty-five of the 32 patients were ultimately determined to have P. carinii pneumonia. Of these, 14 were detected by examination of sputum (sensitivity, 56%). Of 18 patients whose sputum did not contain P. carinii, 11 had the organism detected in specimens obtained by bronchoscopy (negative predictive value, 39%). There were no clinical features that identified patients more likely to have a positive sputum examination. No additional treatable lung pathogens appeared to be missed by sputum examination. In this select population, examination of induced sputum establishes the diagnosis of P. carinii pneumonia in a significant proportion of patients, thereby decreasing the need for more invasive procedures.     

Detection of penumococcal antigens in the sputum in pneumococcal pneumonia.

Forty-seven patients with bacterial pneumonia were grouped by use of clinical criteria according to the relative certainty of a diagnosis of pneumococcal pneumonia. Sputums were tested for pneumococcal antigens by counterimmunoelectrophoresis with polyvalent pneumococcal antiserum. Antigens were detected in the sputum of 29 of 39 patients with evidence of pneumococcal pneumonia, and there was good correlation between the detection of antigens and the degree of certainty of the clinical diagnosis. Antigens persisted briefly in the sputum during therapy with antimicrobial drugs and could be detected during the first 48 hours of therapy in most cases of pneumococcal pneumonia. Pneumococci were isolated from the sputum in only 18 of 39 cases of pneumococcal pneumonia, and sputum cultures did not correlate as well as counterimmunoelectrophoresis with clinical diagnoses. In studies of 27 patients with chronic bronchitis without pneumonia, pneumococci were isolated from sputum in 10 cases, whereas counterimmunoelectrophoresis was positive in 5 cases. Counterimmunoelectrophoresis provides a simple and rapid method for detecting pneumococcal antigens in sputum, and it appears to be more reliable than sputum cultures in establishing a presumptive diagnosis in pneumococcal pneumonia.     

Bacteremic pneumococcal pneumonia in the elderly

Pneumococcal pneumonia is an increasingly important disorder of the elderly. We reviewed, retrospectively, the clinical and laboratory manifestations of 29 elderly patients with bacteremic pneumococcal pneumonia during a five year period and surveyed the capsular serotypes of all blood isolates. Pneumococcal pneumonia frequently presented with subtle manifestations in these elderly patients: 50% lacked historical features suggestive of pneumonia at the time of diagnosis. A common presentation was fever, altered mental status and dehydration. Recognizing this will allow earlier diagnosis and initiation of therapy. Sixty percent of patients had potential pulmonary pathogens other than pneumococcus in cultures of sputum at the time of pneumococcal bacteremia. Reversible abnormalities of liver function were frequent. Sixty-nine percent of pneumonias were caused by serotypes included in the commercially available vaccine. Continued surveillance of pneumococcal serotypes is important to determine if the widespread use of the vaccine will result in an increased incidence of infection by serotypes which are not in the vaccine. The high mortality associated with pneumococcal pneumonia (31% in this series), particularly in the elderly, emphasizes the need for an effective vaccine.     

Bacterial pneumonia

Bacterial pneumonia is significantly more common in persons who are HIV-infected than in the general population and is most common among injection drug users and in persons with advanced HIV disease and immunosuppression. The clinical features of bacterial pneumonia are similar to those in HIV-seronegative persons, but bacteremia is more common. When a pathogen is identified, Streptococcus pneumoniae is consistently the most common, occurring in 20% to 70% of cases. Haemophilus influenzae, Staphylococcus aureus, Escherichia coli, and other gram-negative organisms are mainly responsible for the remainder of bacterial pneumonia episodes in the United States, Central Africa, Australia, and England. In some studies, Chlamydia pneumoniae was recognized as a common cause in persons with early HIV disease, whereas Pseudomonas aeruginosa is recognized as a community- and hospital-acquired lower respiratory tract pathogen in patients with severe immunosuppression. Although antimicrobial therapy is frequently empiric, it should be tailored to the severity of illness, local prevalence of infections, resistance patterns, or when an etiologic agent is identified. The treatment response is similar in patients with and without HIV infection, but bacterial pneumonia may accelerate the progression of HIV disease. Preventative measures include use of the polyvalent pneumococcal vaccine, especially early in the course of HIV infection, when it is most likely to be effective. The incidence of bacterial pneumonia is also reduced in HIV-seropositive persons who use trimethoprim-sulfamethoxazole to prevent Pneumocystis carinii pneumonia.     

Infections in acute exacerbation of chronic bronchitis: what are they and how do we know?

Acute exacerbations of chronic bronchitis can be due to many factors. The most commonly recognized factor is infection, with bacterial infection being identified in about fifty percent of patients with chronic bronchitis. The causative agent can be detected by several different methods. The most common is sputum examination; however, more invasive techniques have been studied. These include transtracheal aspirates and bronchoscopic samples. The most widely studied bronchoscopic sample has been the protected brush specimen (PBS). Despite the wide array of sampling techniques, the pathogens which have been identified have been relatively consistent. The three most common pathogens have been H. influenzae, S. Pneumoniae, and B. catarrhalis. Other pathogens, including gram negative enteric organisms, are seen in patients with more advanced disease. The information obtained by the diagnostic studies has allowed clinicians to develop treatment strategies for AECB. These diagnostic studies will be needed to help upgrade treatment guidelines as new bacteria and bacterial resistance patterns change.     

Diagnosis of pneumococcal pneumonia

Pneumococcal pneumonia presents peculiar problems to the diagnostician. It is at once the most common form of community-acquired bacterial pneumonia and simultaneously the most difficult to document microbiologically. Bacteremia, empyema, meningitis, or septic arthritis due to S pneumoniae unmistakably verifies this bacterium as the cause of a coexistent pneumonia; this coexistence fortunately occurs infrequently. The diagnostic dilemma arises in the less sick patient. While recognizing the common presence of pneumococci in the oropharynx of healthy individuals, we give undue credence to S pneumoniae cultured from sputum obtained by expectoration. At the same time, pneumococci are frequently not found in cultures of sputum obtained from patients with confirmed bacteremic disease. More invasive techniques (transtracheal aspiration, protected bronchoscopic catheter, lung needle aspiration) are too complex, dangerous, or both for routine use. Attempts to detect pneumococcal antigen in blood, sputum, or urine by modern immunologic techniques give promise of avoiding the problems of either contamination or lack of bacteriologic growth. However, they have not yet been evaluated in sufficiently large groups with pneumonia of independently determined bacterial etiology to calculate test sensitivity and specificity. At the present time then, the careful clinician will use all the epidemiologic and clinical evidence at hand, including a careful Gram's stain and culturing of sputum, blood, and other sources, to arrive at the most likely etiology. The probabilities must be weighed in light of the imprecision of current laboratory confirmation and modified by clinical course. Choice of antimicrobial therapy still favor penicillin for patients with community pneumonia severe enough to warrant hospitalization, despite ominous trends in multiple resistance of S pneumoniae.     

急诊就诊53例吸入性肺炎的临床特征及治疗方案分析

目的：分析吸入性肺炎的发病特征、实验室检查、病原菌及治疗方案,为临床诊断及治疗吸入性肺炎提供依据。方法：以回顾性方法收集自2019年11月至2020年7月就诊我院急诊并确诊为吸入性肺炎的患者53例,采集患者人口统计学资料、实验室检查、病原学结果、抗生素使用情况及有效性,并进行统计分析。结果：吸入性肺炎常见于高龄合并神经系统功能障碍患者,主要致病菌以G-菌为主,占83.01%,其与G+菌感染者在年龄、性别、发病时间、症状、实验室检查无明显差异性（P>0.05）。G-为主要致病菌,占83.01%（44 vs 9）,且以肺炎克雷伯菌(21 vs 53)为主。病情严重组中,主要以G-菌为主（89.74%）,提示G-菌病情更危重（χ2 =4.74,P=0.044）。在抗生素选择中,以含β-内酰胺酶抑制剂的抗生素为主且初始治疗更有效(χ2=14.95,P=0.011)。结论： 吸入性肺炎多见于老年患者,尤其是存在神经系统功能障碍患者。革兰氏阴性菌是主要病原体,其中以肺炎克雷伯菌为最常见。抗生素治疗是有效的治疗方案,含β-内酰胺酶抑制剂的抗生素可作为抗感染治疗的一线选择。     

Laboratory diagnosis of nosocomial pneumonia

The second most common nosocomial infection in the United States is pneumonia, with the highest rates seen in patients requiring mechanical ventilation. Nosocomial pneumonia is a serious disease associated with significant morbidity and mortality; crude mortality rates have been estimated at 20% to 50%. The rapid institution of appropriate antimicrobial therapy has been shown to improve mortality in patients with ventilator associated nosocomial pneumonia. Thus, the identification of nosocomial pneumonia with a timely microbiologic diagnosis is important for the management of these patients. However, the accurate diagnosis of nosocomial pneumonia, along with identification of the responsible organism(s), can be challenging. This task becomes even more difficult in patients who are mechanically ventilated. The presence of new pulmonary infiltrates along with clinical criteria including fever, cough, and purulent secretions are neither sensitive nor specific for the diagnosis of nosocomial pneumonia. The laboratory can enhance the accuracy of pneumonia diagnosis, as well as provide the identification of an etiologic organism(s). There are, however, many challenges which confront the laboratory including: the ability to identify organisms from an extensive microbiologic spectrum; distinguishing colonization from infection of predominately gram-negative oropharyngeal flora; and providing timely results. This article reviews the various diagnostic tests available for nosocomial lung infections, and in particular, ventilator associated pneumonia including: blood cultures; pleural fluid; expectorated sputum; endotracheal aspirates; and respiratory specimens obtained by more invasive techniques using bronchoscopy and transthoracic needle aspiration. Emphasis is placed on optimal specimen collection, the processing of samples in the laboratory, and on the evaluation of potential risks and benefits associated with the varying techniques.     

Community-acquired bacterial pneumonia requiring admission to hospital

Patients who develop bacterial pneumonia in the community often require admission to acute-care hospitals. Knowledge of the incidence of pneumonia due to different pathogens that are brought into an institution from the community may play a role in determining the patterns of infecting organisms responsible for hospital-acquired pneumonia. For 1 year, we prospectively reviewed the records of patients admitted to our 1000-bed community hospital with community-acquired bacterial pneumonia (CABP). Patients had clinical signs and symptoms, positive radiologic findings, and pure cultures of potential pathogens from sputum, blood, pleural fluid, lung aspirate, lung biopsy, or transtracheal aspirate. Pneumonia due to Legionella pneumophila was diagnosed by serum indirect fluorescent antibody (IFA) titer ≥ 1: 256 and clinical signs and symptoms along with response to erythromycin. Of 204 patients with bacterial pneumonia, the following pathogens were implicated: Streptococcus pneumoniae, Haemophilus species, L. pneumophila, Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, oral anaerobic bacteria, Psuedomonas aeruginosa, Serratia marcescens, and others. Most patients were more than 50 years of age and many had evidence of underlying pulmonary disease. The etiology of CABP may not be as predictable as in the past. Empiric antimicrobial therapy for CABP should include agents with activity against the pathogens prevalent in the community.     

Chlamydial and mycoplasmal pneumonias

Chlamydia species and Mycoplasma pneumoniae are among the most common agents of community-acquired pneumonia, as well as causes of various nonpneumonic syndromes. Both can be considered "exotic" bacteria: Chlamydiae because they depend on host cell energy, hence their obligate intracellular replication; and M pneumoniae because it is an extracellular parasite that lacks the standard protective bacterial cell wall. The unusual biology of these organisms complicates laboratory diagnosis, but because both are susceptible to selective antimicrobials, therapy often proceeds empirically on clinical suspicion. Generally the respiratory diseases produced are self-limited without significant complications or known sequelae.     

Clinical characteristics of 8 sporadic cases of community-acquired Legionella pneumonia in advanced age

Legionella spp are well recognized as one of the etiologic factor in pneumonia, but it is difficult to distinguish the clinical features of Legionella infection from pneumonia due to other causes. The objective of the present study was to examine the clinical characteristics of community-acquired Legionella pneumonia in elderly patients. We reviewed the clinical, laboratory and radiographic findings in 8 patients diagnosed as having pneumonia caused by Legionella. The diagnosis was confirmed by the presence of urinary antigen, bacterial culture, polymerase chain reaction (PCR) and serum antibody. There were 6 men and 2 women, whose ages ranged from 76 to 85 years. All patients had fever and hypoxia, four patients had respiratory symptoms. The initial chest X-ray findings were varied--consolidation, ground glass opacity, pleural effusion and linear shadow. Urinary antigen was positive in 4 patients, bacterial culture in 2, PCR on the sputum in 3 and serum antibody in 2 patients. As pneumonia caused by Legionella often becomes life-threatening, especially in elderly people, it is imperative to diagnose it at the initial stage. In this study, urinary antigen proved to be the most useful diagnostic means. However, it is important to confirm the diagnosis through plural examinations.     

Clinical features of community-acquired pneumonia treated at Srinagarind Hospital,Khon Kaen,Thailand

Pneumonia is a serious illness associated with significant morbidity and mortality. The interpretation guidelines for pneumonia management requires knowledge of both the clinical presentation of the disease and local epidemiology. We studied the clinical features, initial laboratory results, antibiotic sensitivities, and outcomes of patients diagnosed with acute community-acquired pneumonia between January 1999 and December 2000 at Srinagarind Hospital. The causative organisms were identified in only 52.2% patients; Streptococcus pneumoniae accounted for 23.1% of infections. Other common causes included Klebsiellapneumoniae (19.2%), Burkholderia pseudomallei (15.4%), Hemophilus influenzae (11.5%), Mycoplasma pneumoniae (6.2%), and Staphylococcus aureus (4.6%). Younger patients were more likely to be infected with M. pneumoniae, while the mean age of those with other types of infections was 50. Healthy adults were infected with M. pneumoniae and S. pneumoniae; specific pathogens attacked patients with certain co-morbidity : i) diabetes mellitus and ageing, ii) diabetes mellitus and renal disease, iii) cardiovascular diseases, and iv) connective tissue diseases and steroid-use; these patients were vulnerable to i) K. pneumoniae, ii) B. pseudomallei, iii) H. influenzae, and iv) S. aureus respectively. White blood cell counts were normal in M. pneumoniae infection. Gram-stained sputum had some limitations, especially when determining Gram-negative infections; chest x-rays could not differentiate pathogens. Bactermia was found in one half of patients infected with B. pseudomallei and S. aureus. Antibiotic-resistant organisms were not common in our study. Because morbidity and mortality were high among patients infected with S. aureus and B. pseudomallei, empirical antibiotic treatment should be considered in suspected cases, especially when patients present with acute severe community-acquired pneumonia.     

Current issues in the management of bacterial respiratory tract disease: the challenge of antibacterial resistance

The worldwide burden of respiratory tract disease is enormous. Resistance to penicillins, macrolides, and cephalosporins is now detected among the leading bacterial pathogens that cause respiratory tract infections (RTIs)-Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increasing role of atypical/intracellular pathogens (eg, Chlamydia pneumoniae, Mycoplasma pneumoniae, Legionella pneumophila) in RTIs, as well as their increase in antibiotic resistance prevalence, continues to be of great concern. More recently introduced treatment options for RTIs include the newer respiratory fluoroquinolones, along with the macrolides and azalides. Although these agents demonstrate good activity against common respiratory pathogens, reduced susceptibility to these agents has been reported. The ketolides are recently developed antibacterial agents with targeted-spectrum activity against common respiratory tract pathogens, including atypical/intracellular pathogens, and a low potential for inducing resistance. These promising new drugs have shown in vitro and in vivo efficacy in the treatment of community-acquired RTIs, such as community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial maxillary sinusitis.     

Pneumonia due to Moraxella (Branhamella) catarrhalis

Branhamella catarrhalis is a Neisseriae-like organism that is the newest member of the family of pneumonic pathogens. The organism is seasonal, encountered only during the respiratory disease season. The majority of patients with pneumonia (80% to 90%) have underlying chronic pulmonary disease, and their clinical illness may be difficult to distinguish from exacerbations of lung disease by other causes. B catarrhalis is the most common bacterial pathogen in this setting after Haemophilus influenzae and Streptococcus pneumoniae. The organism is easy to identify in the laboratory, with a quality gram stain of sputum being the key to recognition. Most patients show patchy non-cavitary infiltrates on chest roentgenograms. Because 75% of isolates produce beta lactamase, empiric therapy with penicillin or amoxicillin is likely to fail. Recommended drugs include erythromycin, trimethoprim/sulfamethoxazole, amoxicillin/clavulanic acid (Augmentin), or one of the newer broad spectrum cephalosporins.