Common Pathogens In Community-acquired Pneumonia Research Articles

Etiology of bacterial community-acquired pneumonia among hospitalized children in Hai Phong Children’s Hospital

The objectives of this study were to determine the etiology of bacterial community-acquired pneumonia (CAP) in children hospitalized at Hai Phong Children’s Hospital (HCH) in 2019 and these bacteria’s antibiotic resistance properties. The subjects were the qualified medical records of all inpatients at the Respiratory Department of Hai Phong Children’s Hospital aging from 1 month to 15 years old diagnosed with CAP according to the diagnostic criteria of the World Health Organization with positive nasopharyngeal swab culture results from January 1st, 2019, to December 31st, 2019. The sample size included all medical records of patients who met the inclusion criteria of this research during the study period. The success rate of nasopharyngeal swab culture test of CAP patients was 638/1605 (39.7%). The most common pathogens of CAP in children at HCH were S. aureus, S. pneumoniae, H. influenzae and M. catarrhalis. Antibiogram revealed that each of them showed high resistance to a various type of antibiotics. Our study also provided valuable data on the antibiotic sensitivity and raised alarm over presence of multidrug-resistant bacteria inducing CAP in children.

Diagnosis and Treatment of Water-Contaminated Severe Legionella Pneumonia with Digestive Symptoms as the First Symptom: A Case Report and Review of the Literature

Although Legionella is not the most common pathogen of community-acquired pneumonia, the epidemiological distribution of pneumonia pathogens has changed in recent years, with a gradual increase in some rare pathogens. For example, pneumonia that occurs after water source contamination is mostly caused by Legionella infection. This paper reports the diagnosis and treatment process of a patient after Legionella infection, who had misdiagnosis at the beginning, rapidly progressed to severe disease and combined with fungal infection. This article focuses on the timely and effective treatment of rapidly progressing Legionella pneumonia, in anticipation of a better understanding of the diagnosis and treatment of the disease. Here, we report a case of legionella infection with the nausea, vomiting as the first symptoms accompanied by weakness, chills, dizziness, abdominal discomfort in a 75-year-old female. The patient had a history of type 2 diabetes for 30 years, diabetic peripheral neuropathy for more than 20 years, arterial hypertension for 10 years, bone hyperplasia for more than 5 years, resection of right-sided thyroid cystadenoma in 1990. The patient had firstly been diagnosed with cholecystitis and gallbladder neck stones, diet abstinence, metronidazole, cefoperazone sulbactam, and rehydration were given. The patient responded poorly to these empiric treatments. The patient was given moxifloxacin in combination with azithromycin after the onset of respiratory symptoms, but the condition continued to deteriorate, and tigecycline was subsequently added. After the mechanical ventilation and the treatment plan adjusting, she improved significantly. Immunocompromised patient combined with underlying diseases are more susceptible to infection in an environment contaminated with Legionella, and the rapid onset and atypical respiratory symptoms make it easy to misdiagnose the disease, thus delaying treatment and leading to further deterioration. Timely diagnosis, early mechanical ventilation and rational drug administration were fundamental to treat Legionella pneumonia.

Refractory Mycoplasma Pneumonia in Children: A Systematic Review and Meta-analysis of Laboratory Features and Predictors.

Background Mycoplasma pneumoniae is a common pathogen of community-acquired pneumonia (CAP) in children. M. pneumoniae infection is usually regarded as a self-limiting disease, but in some special cases, it can also develop into refractory Mycoplasma pneumoniae pneumonia (RMPP). The aim of this study is to analyze the clinical characteristics of CRP (C-reactive protein), LDH (lactate dehydrogenase), ESR (erythrocyte sedimentation rate), D-dimer, neutrophils (%), lymphocytes (%), and lung consolidation in RMPP and explore their prediction results in the early stage of RMPP, which is important for early treatment. Methods This systematic search was conducted in PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wangfang, and Cqvip, and the date was set until February 23, 2021. For the continuous variables, mean difference (MD) with 95% CI was adopted to evaluate CRP, LDH, ESR, D-dimer, neutrophils (%), lymphocytes (%), and the correlation between lung consolidation and RMPP. Results 20 studies including 5289 patients were included in the analysis, and the results showed that the CRP of the RMPP group (MD (95% CI): 22.29 (12.20, 32.38), P < 0.001), LDH (MD (95% CI): 145.13 (78.62, 211.64), P < 0.001), neutrophils (%) (MD (95% CI): 7.27 (0.31, 14.23), P = 0.04), and D-dimer (MD (95% CI): 1.79 (-1.17, 4.74), P = 0.24) was higher than that of the NRMPP group; the risk of lung consolidation in the RMPP group (OR (95% CI): 14.29 (4.52, 45.12), P < 0.001) was higher than that in the NRMPP group, and there was no difference in ESR (MD (95% CI): 8.11 (-1.34, 17.56), P = 0.09) and lymphocytes (%) (MD (95% CI): -6.27 (-12.81, 0.27), P = 0.06) between the two groups. Conclusion So, the available evidence indicates that CRP, LDH, neutrophils (%), D-dimer, and lung consolidation are predictive factors for RMPP.

Impact of co-infection of streptococcus pneumoniae and pneumococcal vaccination on the clinical outcomes of coronavirus disease 19

Coronavirus disease 19 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 has spread all over the world. Streptococcus pneumoniae as a common pathogen of community-acquired pneumonia shares similar high-risk susceptible populations with COVID-19. Streptococcus pneumoniae co-infection is a key risk factor for severe COVID-19 and death. Pneumococcal vaccination has a beneficial impact on reducing the incidence and mortality of COVID-19. The vaccination rate of streptococcus pneumoniae is still low in China. Streptococcus pneumoniae vaccination may be one of effective strategies in the management of COVID-19 for high-risk population such as the elderly and those who have underlying chronic diseases.

Current guidelines for the selection of an antibacterial drug in children with community-acquired pneumonia

The COVID-19 pandemic has affected the incidence of acute respiratory infections in the modern world. Despite the growing etiological significance of viruses in the structure of infectious diseases, the importance of bacterial pathogens in the development of respiratory pathology remains. The risk of unreasonable prescription of antibacterial drugs increases. The irrational use of antibacterial drugs has affected the spread of microorganisms with high resistance to antibiotics. The article presents current knowledge on the role of the most common pathogens of community-acquired pneumonia in children, data concerning the S. pneumoniae strain with reduced sensitivity and resistance to penicillin, macrolides. Information about isolates of S. Pneumoniae with decreased susceptibility to third-generation parenteral cephalosporins (cefotaxime and ceftriaxone) have appeared. The number of β-lactamase-producing strains of H. influenzae resistant to unprotected aminopenicillins is rising. The main steps of the diagnostic process of community-acquired pneumonia approved in the clinical guidelines for community-acquired pneumonia in children in 2022, which were adopted by the Russian Ministry of Health, are considered. This document sets out clear algorithms for diagnosing and selecting antibacterial therapy in children on an outpatient basis. Algorithms for selecting initial antibacterial therapy in outpatient settings are also proposed. In most cases, S. pneumoniae is a causative agent of community-acquired pneumonia in children, which defines the selection of an initial antibacterial drug. According to the clinical guidelines, oral amoxicillin at a standard dose of 45–55 mg/kg/day given in 2–3 divided doses is such a drug for children aged 3 months and older. Particular attention is paid to amoxicillin in the form of dispersible tablets.

Диагностика и лечение внебольничной пневмонии у детей

На практике, особенно в амбулаторных условиях, серьезными проблемами педиатрии являются ранняя диагностика и рациональная терапия пневмонии у детей. Наиболее распространенными возбудителями при внебольничной пневмонии являются Streptococcus pneumoniae, Haemophilus influenzae и другие микроорганизмы, в том числе вирусы и грибы. Следует уточнить, что этиология заболеваний нижнего респираторного тракта резко отличается в разных возрастных группах. Самой частой причиной внебольничной пневмонии (до 50 %) является S.pneumoniae, реже встречаются такие палочки, как E.сoli, Klebsiella spp., C.trachomatis, Mycoplasma, Ureаplasma. У детей старше 5 лет в этиологической структуре внебольничной пневмонии наряду с S.рneumoniae возрастает значимость Mycoplasma рneumoniae. Резистентность возбудителей инфекции к антибактериальным препаратам — нарастающая глобальная проблема. Алгоритм диагностики внебольничной пневмонии включает фебрильную температуру продолжительностью &gt; 3 дней, цианоз, одышку при отсутствии признаков бронхиальной обструкции, кашель. Тахипноэ является одним из лучших предикторов пневмонии у детей всех возрастов. При физикальном обследовании — наличие укорочения перкуторного звука в зоне поражения, бронхиальное или ослабленное дыхание, звучные мелкопузырчатые или крепитирующие хрипы. Для диагностики нетяжелых внебольничных пневмоний вполне достаточно ограничиться клиническими симптомами, рентгенографией легких, общим анализом крови. Начальная антибиотикотерапия внебольничной пневмонии проводится эмпирическим путем. При лечении нетяжелых внебольничных пневмоний у детей от 2 мес. до 5 лет препаратом выбора является амоксициллин перорально. Макролиды — препараты выбора у детей от 5 до 16 лет. При тяжелой пневмонии препаратами выбора являются амоксициллин/клавуланат, цефалоспорины II, III, IV поколения. В целом продолжительность антибиотикотерапии при внебольничной пневмонии, вызванной типичными бактериями, составляет 7–10 дней, атипичными бактериями — 10–14 дней. В реальной клинической практике при проведении антибактериальной терапии нередко наблюдаются ошибки, связанные с выбором препарата, пути введения, дозировки, режима применения, длительности курса.

T-B cell epitope peptides induce protective immunity against Mycoplasma pneumoniae respiratory tract infection in BALB/c mice

Mycoplasma pneumoniae is the most common pathogen of community-acquired pneumonia in humans. Due to its high rates of antibiotic resistance, vaccination has become the best method to control the dissemination of M. pneumoniae. The recombinant carboxyl terminus of the P1 (P1C) protein is an immunodominant antigen, but it has negative effects such as poor stability and lower purity. In the current study, T-B epitopes of the P1C protein were predicted according to bioinformatics analysis and assessed for efficacy in peptide vaccination. BALB/c mice were subcutaneously inoculated with the T-B epitope peptides four times and then infected with M. pneumoniae through the respiratory tract. The results showed that the T-B epitope peptides of the P1C protein (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) induced strong antigen-specific serum antibody responses and cellular immune responses with high levels of serum IgG, IgA antibodies and Th1-biased (IFN-γ and IL-2) cytokines. Immunization with T-B epitope peptides significantly reduced the M. pneumoniae burden and the degree of inflammation in the challenged mice. Furthermore, the levels of IFN-γ and TNF-α in the supernatants of lung homogenates were observably reduced compared to those in the PBS group. Overall, our findings demonstrate that T-B epitopes (P1C103-117, P1C155-169, P1C224-238 and P1C244-258) play significant roles in the P1C protein and can be used to induce powerful humoral and cellular immune responses to provide significant protection against M. pneumoniae pulmonary infection, which provides new insight into the design of potential multiepitope vaccines to prevent host infection by M. pneumoniae.

Yap/Taz regulate alveolar regeneration and resolution of lung inflammation.

Alveolar epithelium plays a pivotal role in protecting the lungs from inhaled infectious agents. Therefore, the regenerative capacity of the alveolar epithelium is critical for recovery from these insults in order to rebuild the epithelial barrier and restore pulmonary functions. Here, we show that sublethal infection of mice with Streptococcus pneumoniae, the most common pathogen of community-acquired pneumonia, led to exclusive damage in lung alveoli, followed by alveolar epithelial regeneration and resolution of lung inflammation. We show that surfactant protein C-expressing (SPC-expressing) alveolar epithelial type II cells (AECIIs) underwent proliferation and differentiation after infection, which contributed to the newly formed alveolar epithelium. This increase in AECII activities was correlated with increased nuclear expression of Yap and Taz, the mediators of the Hippo pathway. Mice that lacked Yap/Taz in AECIIs exhibited prolonged inflammatory responses in the lung and were delayed in alveolar epithelial regeneration during bacterial pneumonia. This impaired alveolar epithelial regeneration was paralleled by a failure to upregulate IκBa, the molecule that terminates NF-κB-mediated inflammatory responses. These results demonstrate that signals governing resolution of lung inflammation were altered in Yap/Taz mutant mice, which prevented the development of a proper regenerative niche, delaying repair and regeneration of alveolar epithelium during bacterial pneumonia.

Decreased relative risk of pneumococcal pneumonia during the last decade, a nested case-control study

BackgroundStreptococcus pneumoniae (SP) is one of the most common pathogens of Community-Acquired Pneumonia (CAP), but recent reports suggest that its incidence may be declining in relation to the use of the conjugate 13-valent pneumococcal vaccine in children. We compared the result of the immunochromatographic SP urinary antigen test (SPUAT) and clinical outcomes in patients with CAP admitted in two periods of time: 2001–2002(CAP1) and 2015–2016(CAP2).MethodsThis was a matched nested case-control study of two prospectively recorded cohorts of patients admitted with CAP, with SPUAT and blood culture performed in all patients. CAP2 cases and CAP1 controls were matched for age ± 4 years, sex, and Pneumonia Severity Index (PSI) score ± 10 points. Odds ratios (OR) for having SPUAT positive was estimated by conditional logistic regression. A multivariate model assessed the contribution of individual variables.ResultsFour hundred ninety-eight patients were recruited; 307 during the CAP1 and 191 during the CAP2 periods. Comparing both periods we observed differences, in age, PSI score, and the percentage of smokers, outpatients, previously immunized with pneumococcal vaccine, and positive SPUAT. On the other hand, mortality, admission from nursing homes, pneumococcal bacteremia and hospital admission were not different. After matching, pneumonia due to SP per the SPUAT was observed in 34(23.4%) of CAP1 and in 12(8.3%) of CAP2 patients (p < 0.001), and 6/145 CAP1 vs 33/145 CAP2 patients had received pneumococcal immunization before their admission (p < 0.001). A multivariate analysis confirmed that, independent of falling into PSI class 5, having not received the pneumococcal vaccine and having not survived the episode of pneumonia, there were two factors that increased the probability of having SPUAT positive: developing pneumonia during the CAP1 period (OR = 1.23) and having pneumococcal bacteremia (OR = 2.66).ConclusionWe observed a reduction of the role of SP as pathogen, along with an increase in the number of patients who received pneumococcal immunization before admission, in 2015-2016 compared to 2001-2002. In addition, the use of conjugate 13-valent vaccine, starting in 2012 for childhood immunization, could be an additional factor contributing to these changes, as a result of early herd immunity in adults pneumonia.

Aetiology of Bacterial Pathogens from Adult Patients with Community-Acquired Pneumonia in Arba Minch Hospital, South Ethiopia

Background: Community-acquired pneumonia (CAP) is major causes of morbidity and mortality. The etiology of CAP varies by geographic region; knowing the etiology might help for the management of the case in case of emergency and to guide treatment. So, in resource limited countries it is wise to identify the most common pathogens of CAP. The objective of this study was to determine bacterial etiology of CAP among adult patients visiting Arba Minch Hospital. Methods: A cross sectional study was conducted in Arba Minch Hospital, Southern Ethiopia from March 01 to June 01, 2013. Data was collected from adult patients with CAP visiting Arba Minch Hospital using face to face interviews, observation using checklist and laboratory examinations. Sputum specimens were collected and microbiological investigations were performed using standard procedures. Data was processed and analyzed with SPSS version16.0 and Excel 2007. Results: Out of 170 cases, only 68 (40%) were culture positive. One pathogen was demonstrated in 63 (92.6%) patients and 6 (7.4%) had mixed infection. The common isolates of single bacterial pathogens from sputum specimens were S. pneumoniae 20 (11.8%), S. aureus 15 (8.8%), P. aeruginosa 10 (5.8%), K. pneumoniae 8 (4.7%), E. coli 4 (2.4%), H. influenzae 4 (2.4%), P. mirabilis 1 (0.6%), and P. vulgaris 1 (0.6%). The commonest mixed bacterial isolate was K. pneumoniae and P. aeruginosa 2(1.2%). Conclusion: In this study, common bacteria isolated were S. pneumoniae, S. aureus and gram negative bacteria. Significant numbers of Gram negative bacteria were isolated which may indicate a shift of infection trend to Gram negative bacteria. Hence, periodic monitoring of etiologic agents with their drug resistant pattern is essential for better management of CAP and treatment strategies.

New Cephalosporin Shows Promise in Drug-Resistant Pneumonia

New Cephalosporin Shows Promise in Drug-Resistant Pneumonia

Significance of Anaerobes and Oral Bacteria in Community-Acquired Pneumonia

BackgroundMolecular biological modalities with better detection rates have been applied to identify the bacteria causing infectious diseases. Approximately 10–48% of bacterial pathogens causing community-acquired pneumonia are not identified using conventional cultivation methods. This study evaluated the bacteriological causes of community-acquired pneumonia using a cultivation-independent clone library analysis of the 16S ribosomal RNA gene of bronchoalveolar lavage specimens, and compared the results with those of conventional cultivation methods.MethodsPatients with community-acquired pneumonia were enrolled based on their clinical and radiological findings. Bronchoalveolar lavage specimens were collected from pulmonary pathological lesions using bronchoscopy and evaluated by both a culture-independent molecular method and conventional cultivation methods. For the culture-independent molecular method, approximately 600 base pairs of 16S ribosomal RNA genes were amplified using polymerase chain reaction with universal primers, followed by the construction of clone libraries. The nucleotide sequences of 96 clones randomly chosen for each specimen were determined, and bacterial homology was searched. Conventional cultivation methods, including anaerobic cultures, were also performed using the same specimens.ResultsIn addition to known common pathogens of community-acquired pneumonia [Streptococcus pneumoniae (18.8%), Haemophilus influenzae (18.8%), Mycoplasma pneumoniae (17.2%)], molecular analysis of specimens from 64 patients with community-acquired pneumonia showed relatively higher rates of anaerobes (15.6%) and oral bacteria (15.6%) than previous reports.ConclusionOur findings suggest that anaerobes and oral bacteria are more frequently detected in patients with community-acquired pneumonia than previously believed. It is possible that these bacteria may play more important roles in community-acquired pneumonia.

The incidence and etiology of community-acquired pneumonia in fever outpatients

The purpose of this study was to analyze the incidence, etiology and clinical characteristics of community-acquired pneumonia (CAP) among outpatients with sore throat and/or cough, and thus to provide theoretical basis for timely and accurate diagnosis and treatment for CAP. We used chest X-rays for fever (a temperature greater than 37.5°C) patients, who were recruited since 2007, presenting with sore throat and/or cough. The patients' age, gender, days of fever, respiratory symptoms (e.g. cough and sputum), peripheral blood count and etiology (pathogens) of CAP were recorded. Of all the 6539 fever outpatients, those aged 10-39 and above 60 years old accounted for 61.0% and 15.6%, respectively. In total, 402 were diagnosed with CAP with an incidence rate of 6.1%. Among them, 38.1% were above 60 years old. The prevalence increased with age. Of the 402 CAP patients, 36.8% (148/402) presented no respiratory symptoms and 30.1% (121/402) had positive etiology. The top three pathogens were Mycoplasma pneumoniae (23.1%), Streptococcus pneumoniae (17.3%) and Haemophilus influenzae (9.1%). Among the 121 etiology-positive patients, 14 cases were mixed infections (at least one atypical pathogen). Nine cases were M. pneumoniae mixed with bacterial/virus infection, and five cases were Chlamydia pneumoniae mixed with other bacteria/mycoplasma infection. We found that fever outpatients have a higher prevalence of CAP, which increases with age, i.e. older people are more susceptible to CAP. S. pneumoniae and H. influenzae are common pathogens in CAP; however, atypical pathogens, especially M. pneumoniae, remain the most common pathogens in CAP.

Progress on the treatment of mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae is the common pathogen of community-acquired pneumonia in children. In recent years,the incidence of mycoplasma pneumoniae pneumonia(MPP) has increased year by year. And it is found that case reports about intractable MPP at home and abroad have also significantly increased. The treatments of MPP become the focus in clinical physicians. This paper summarized about progress of MPP in antibiotic therapy,immune therapy and other ancillary treatment. Key words: Mycoplasma pneumoniae; Pneumonia; Antibiotic; Immune treatment

Clinical Evaluation of the Multiplex PCR Assay for the Detection of Bacterial Pathogens in Respiratory Specimens from Patients with Pneumonia

Background: Community-acquired pneumonia (CAP) is a major infectious disease with significant morbidity and mortality worldwide. Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Bordetella pertussis are common pathogens of CAP; however, the conventional methods used to detect these agents, including culturing, lack sensitivity and are time-consuming. We evaluated a recently developed multiplex PCR assay which can test these agents simultaneously. Methods: One hundred patients with pneumonia and 99 healthy adults were tested using the Seeplex Pneumobacter ACE Detection assay (Seegene, Inc., Seoul, Korea). Culture and urinary antigen tests were also performed. Results: In patients with pneumonia, the positive detection rates of PCR for S. pneumoniae and H. influenzae were 52.0% (52/100) and 30.0% (30/100), respectively, those of M. pneumoniae and L. pneumophila were 2.0% (2/100) and 1.0% (1/100), respectively, and B. pertussis and C. pneumoniae were not detected. In healthy adults, the detection rates of S. pneumoniae and H. influenzae revealed similar results, 53.5% (53/101) and 40.4% (40/101), respectively, and the other four pathogens were not detected. The sensitivity and specificity of PCR for S. pneumoniae in pneumonia patients were 100% (95% confidence interval [CI], 87.9∼100%) and 65.7% (95% CI, 55.2∼76.5%), respectively, according to the urinary antigen test and cultures of the respiratory samples and blood. Conclusion: Differentiating S. pneumoniae and H. influenzae colonization from infection was difficult using the PCR assay. Therefore, the use of this assay is inappropriate for the diagnosis of pneumonia due to these agents, although multiplex PCR assay would be useful for the detection of M. pneumoniae and L. pneumophila. (Korean J Clin Microbiol 2010;13:40-46)

A Case of Mycoplasma Pneumonia Presenting with RUL Collapse

Mycoplasma pneumoniae에 의한 폐렴의 임상양상은 다양하다고 알려져 있으며, 흉부 방사선 소견상 대부분 기관지 주위 폐렴이나 반점형 폐 침윤 양상을 보이고 폐 허탈은 5% 정도로 매우 드물게 발생하는 것으로 되어 있다. 본 저자들은 미열, 두통, 건성 기침, 근육통 등 비정형적인 폐렴의 증상을 보이면서 대엽성 무기 폐로 발현한, 마이코플라즈마 폐렴을 경험하였기에 이를 보고하는 바이다.

Review of treatment guidelines for community-acquired pneumonia

Community-acquired pneumonia (CAP) is a costly disease that is associated with significant morbidity and mortality. The growing prevalence of this disease has resulted in various advances in diagnosis and treatment. The most common pathogens of CAP include Streptococcus pneumoniae, Haemophilus influenzae, and atypical pathogens; however, the underlying pathogen often is unknown. Treatment of CAP has evolved because of changing etiologic patterns and increasing antimicrobial resistance among common respiratory pathogens. Among the groups that have established treatment guidelines for CAP are the American Thoracic Society (ATS), the Infectious Diseases Society of America (IDSA), and the Centers for Disease Control and Prevention (CDC). These guidelines establish risk factors associated with drug resistance or infection with specific pathogens. In addition, each guideline provides unique recommendations that are similar in some ways, yet different in others. By understanding the various risk factors for drug resistance and the treatment options endorsed by these guidelines, physicians can treat patients with the most appropriate antimicrobial available.

Comparative efficacies of ciprofloxacin, amoxicillin, amoxicillin-clavulanic acid, and cefaclor against experimental Streptococcus pneumoniae respiratory infections in mice

Experimental respiratory infections were established in mice by intranasal inoculation of Streptococcus pneumoniae. Inoculation of 10(7) CFU of either S. pneumoniae 1629 or S. pneumoniae 7 produced a fatal pneumonia in nontreated mice 2 to 3 days after infection. Oral therapy was commenced 1 h after infection and was continued three times a day for 2 days. The doses used in mice produced peak concentrations in serum and lung tissue similar to those measured in humans. Ciprofloxacin failed to eliminate either strain of pneumococcus from mouse lungs at any of the doses tested (40, 80, or 160 mg/kg of body weight) by the end of therapy (33 h). Mice that received ciprofloxacin at 160 mg/kg were clear of S. pneumoniae 7 5 days later, whereas persistence and regrowth of S. pneumoniae 1629 resulted in the death of 20% of animals treated with ciprofloxacin. Therapy with cefaclor (20 mg/kg) produced an effect similar to that of ciprofloxacin. In contrast, amoxicillin (10 and 20 mg/kg) and amoxicillin-clavulanic acid (10/5 and 20/10 mg/kg) were significantly (P less than 0.05) more effective in eliminating both strains of S. pneumoniae from the lungs by the end of therapy and, by 168 h, had prevented mortality in 80 to 100% of treated animals. The efficacy of ciprofloxacin against these experimental pneumococcal respiratory infections was poor, despite good penetration into lung tissue, and is a reflection of the low in vitro activity of the quinolone against S. pneumoniae, one of the most common pathogens in community-acquired pneumonia.