Characteristics of Streptococcus pneumoniae and atypical bacterial infections in children 2-5 years of age with community-acquired pneumonia

Pneumonia in hospitalized children

Pneumonia is one of the most common infections in the pediatric age group and one of the leading diagnoses that results in overnight hospital admission for children. Various micro-organisms can cause pneumonia, and etiologies differ by age. Clinical manifestations vary, and diagnostic testing is frequently not standardized. Hospital management should emphasize timely diagnosis and prompt initiation of antimicrobial therapy when appropriate. Issues of particular relevance to inpatient management are emphasized in this article.

Role of atypical bacteria and azithromycin therapy for children with recurrent respiratory tract infections

BACKGROUND

The aim of this study of 352 patients, 1-14 years of age, with acute respiratory infections and a history of recurrent respiratory tract infections (RRTIs), and 208 healthy subjects was to evaluate whether Mycoplasma pneumoniae and Chlamydia pneumoniae played a role in causing acute respiratory episodes among children with RRTIs and whether specific antibiotic treatment for these bacteria could improve the acute episodes and reduce recurrences.

METHODS

The patients were blindly randomized to receive azithromycin (10 mg/kg/d for 3 days weekly, for 3 weeks) together with symptom-specific agents or symptom-specific agents alone. Acute M. pneumoniae and/or C. pneumoniae infection was diagnosed if the child had a significant antibody response in paired sera and/or if the DNA of the bacteria was detected in nasopharyngeal aspirates.

RESULTS

Atypical bacterial infections were identified for 190 patients (54.0%) and 8 healthy control subjects (3.8%; P < 0.0001). Short term (1-month) clinical success was significantly more frequent among the patients who had received azithromycin together with symptom-specific agents than among those who had received symptom-specific agents alone, but the difference was significant only for the group of patients with atypical bacteria. In contrast, long term (6-month) clinical success was significantly more frequent among the patients who had received azithromycin in addition to symptom-specific agents, regardless of whether they experienced infections with atypical bacteria or other pathogens, although positive outcomes were significantly more frequent among those with atypical bacteria.

CONCLUSIONS

Atypical bacteria seem to play a role among children with RRTIs, and prolonged azithromycin therapy can significantly improve the acute episodes and reduce the risk of recurrences.

Immunogenicity, safety and tolerability of heptavalent pneumococcal conjugate vaccine administered at 3, 5 and 11 months post-natally to pre- and full-term infants

We assessed the immunogenicity, safety and tolerability of heptavalent pneumococcal conjugate vaccine (PCV7) administered three, five and 11 months post-natally to 46 pre-term (PT) and 46 full-term (FT) infants. After each dose, there was no significant difference between the groups in antibody levels for any of the vaccine serotypes. After the second dose, the majority of subjects in both groups showed titres of > or =0.35 microg/mL, whereas an antibody concentration of > or =1.0 microg/mL was usually reached in both PT and FT infants after the third dose. Safety and tolerability was also similar in the groups. These findings support the use of the simplified schedule that includes three doses of PCV7 in both PT and FT infants, and suggest that this may reduce costs, as well as problems related to vaccine supply and administration.

Non-specific host response markers in the differentiation between pneumococcal and viral pneumonia: what is the most accurate combination?

BACKGROUND

Serum C-reactive protein (CRP), blood white cell count (WBC), serum procalcitonin (PCT) and erythrocyte sedimentation rate (ESR) were measured in 132 children hospitalized for community-acquired pneumonia. Serological evidence for viral infection was found in 38 cases and for pneumococcal infection in 41 cases, and the infiltrate was alveolar in 46 cases and interstitial in 86 cases. The aim of the present paper was to determine if there is a combination of these four host response markers and chest radiograph findings suitable for differentiating pneumococcal from viral etiology of pneumonia.

METHODS

The 50th, 75th and 90th percentiles of CRP, WBC, ESR and PCT in the total group of 132 patients were calculated. By using these cut-off limits, the likelihood ratios of a positive test result were calculated for the possible combinations of CRP, WBC, ESR and PCT, and the likelihood ratio was 1.50 or more for six combinations.

RESULTS

The highest likelihood ratio (1.74) was achieved with the combination CRP > 90th (80 mg/L) or WBC > 75th (17.0 x 10(9)/L) or PCT > 75th (0.84 microg/L) or ESR > 90th (63 mm/h) percentile. For this combination, the sensitivity was 61% and the specificity 65%. When the 90th percentile cut-off limit was applied also for WBC (>22 x 10(9)/L) and PCT (>1.8 microg/L), the specificity increased to 76%, but the sensitivity decreased to 37%. When the presence of an alveolar infiltration was included in the combination, the likelihood ratio was 1.89; the specificity was as high as 82% and the sensitivity as low as 34%.

CONCLUSIONS

CRP, PCT, WBC and ESR have only limited value in differentiating pneumococcal or other bacterial pneumonia from viral pneumonia. If there was a high value in at least one of the markers (CRP > 80 mg/L, PCT > 1.8 microg/L, WBC > 22 x 10(9)/L or ESR > 60 mm/h), viral infections were rare. There was no combination of these markers which was sufficiently sensitive and specific to be used in clinical pediatric practice.

Aetiology of acute pharyngitis: the role of atypical bacteria

In order to establish the role of atypical bacteria and compare characteristics of different infectious agents in acute pharyngitis, 127 patients with acute pharyngitis (66 males; median age, 5.33 years; range, 6 months to 14 years) and 130 healthy subjects of similar sex and age were studied. Serology with paired samples and PCR on nasopharyngeal aspirates and throat cultures were used to identify bacteria and viruses. Viruses were identified in 43 patients (33.8%) and five controls (3.8%; P < 0.0001), potential bacterial pathogens in 34 patients (26.8%) and 26 controls (20%; P = 0.256) and mixed viral/bacterial pathogens in 26 patients (20.5%) and none of the controls (P < 0.0001). The main aetiological agents were adenovirus, respiratory syncytial virus (RSV), Mycoplasma pneumoniae, Streptococcus pyogenes and Chlamydia pneumoniae. M. pneumoniae was the agent found most frequently as a single pathogen. A history of recurrent pharyngitis, having older siblings and a negative outcome were significantly more common among patients with acute M. pneumoniae infection than among those with infections due to other pathogens or healthy controls. This study demonstrates that: (i) adenovirus and RSV have a prominent role in acute pharyngitis; (ii) S. pyogenes is found frequently, but it is not possible to distinguish simple carriers from patients with a true infection; (iii) M. pneumoniae appears to be able to cause acute pharyngitis per se; and (iv) C. pneumoniae seems to be mainly a co-pathogen. To avoid the risk of an incorrect therapeutic approach, simple laboratory investigations that allow rapid identification of M. pneumoniae infections are urgently needed.

Community-acquired pneumonia in children: issues in optimizing antibacterial treatment

The treatment of community-acquired pneumonia (CAP) in children is empirical, being based on the knowledge of the etiology of CAP at different ages. As a result of currently available methods in everyday clinical practice, a microbe-specific diagnosis is not realistic in the majority of patients. Even the differentiation between viral, 'atypical' bacterial (Mycoplasma pneumoniae or Chlamydia pneumoniae) and 'typical' bacterial (Streptococcus pneumoniae) CAP is often not possible. Moreover, up to one-third of CAP cases seem to be mixed viral-bacterial or dual bacterial infections. Recent serologic studies have confirmed that S. pneumoniae is an important causative agent of CAP at all ages. M. pneumoniae is common from the age of 5 years onwards, and C. pneumoniae is common from the age of 10 years onwards. In addition to age, the etiology and treatment of CAP are dependent on the severity of the disease. Pneumococcal infections are predominant in children treated in hospital, and mycoplasmal infections are predominant in children treated at home.In ambulatory patients with CAP, amoxicillin (or penicillin V [phenoxymethylpenicillin]) is the drug of choice from the age of 4 months to 4 years, and at all ages if S. pneumoniae is the presumptive causative organism. Macrolides, preferably clarithromycin or azithromycin, are the first-line drugs from the age of 5 years onwards. In hospitalized patients who need parenteral therapy for CAP, cefuroxime (or penicillin G [benzylpenicillin]) is the drug of choice. Macrolides should be administered concomitantly if M. pneumoniae or C. pneumoniae infection is suspected. Radiologic findings and C-reactive protein (CRP) levels offer limited help for the selection of antibacterials; alveolar infiltrations and high CRP levels indicate pneumococcal pneumonia, but the lack of these findings does not rule out bacterial CAP. Most guidelines recommend antibacterials for 7-10 days (except azithromycin, which has a recommended treatment duration of 5 days). If no improvement takes place within 2 days, therapy must be reviewed.

Optimizing antibacterial therapy for community-acquired respiratory tract infections in children in an era of bacterial resistance

The spread of antibacterial resistance in bacteria that commonly cause childhood community-acquired respiratory tract infections (RTIs), such as acute otitis media, community-acquired pneumonia, and acute pharyngitis, is a major healthcare problem. One of the foremost concerns is the rapid increase in penicillin, macrolide, and multidrug resistance in Streptococcus pneumoniae. There is also a rising prevalence of macrolide resistance in Streptococcus pyogenes in pockets of the United States, and beta-lactamase production in Haemophilus influenzae is widespread. Although data are limited, some evidence suggests that resistance to antibacterials can impair bacteriologic and clinical outcomes in childhood RTIs. Optimizing antibacterial use is important both in the care of individual patients and within strategies to address the wider problem of antibacterial resistance. This involves encouraging judicious antibacterial use (i.e., reducing overuse for viral infection and prophylaxis), and preventing misuse through the wrong choice, dosage, and duration of therapy. Given that initial therapy is usually empiric, antibacterials used to treat community-acquired RTIs in children should ideally have the following properties: an optimal targeted spectrum of activity; high clinical and bacteriologic efficacy against respiratory pathogens, including resistant strains; simple, short-course therapy; and good tolerability and palatability. New antibacterials will continue to have a role in the treatment of RTIs in children, especially where resistance compromises existing therapies.

Antimicrobial resistance among pediatric respiratory tract infections: clinical challenges

Considerable development of antimicrobial resistance has occurred in the major pediatric bacterial pathogens, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. However, most of the respiratory infections that children suffer are viral and self-limiting, and only a small percentage of them will develop secondary bacterial infections with the pathogens listed. The challenge for rational antibiotic use is to determine which patients can be treated conservatively and which require antimicrobial intervention to avoid prolonged discomfort or development of permanent sequelae. The basis for rational use of antibiotic in the era of resistance in these major pathogens is to avoid overuse of antimicrobial agents, tailor treatment to identified pathogens as much as possible, and base empiric treatment on the disease being treated and the susceptibility of the probable pathogens at breakpoints based on pharmacokinetic and pharmacodynamic parameters. With appropriate dosing regimens based on these parameters and despite development of resistance, amoxicillin is still one of the most active oral agents against S. pneumoniae and non-beta-lactamase producing strains of H. influenzae, whereas amoxicillin-clavulanate is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis. Parenteral ceftriaxone and oral and parenteral fluoroquinolones are active against all 3 species, but fluoroquinolones should be used with utmost caution when all other options have been considered because of concerns about toxicity and development of resistance. Introduction of a 7-valent conjugate pneumococcal vaccine in the United States in 2000 reduced the prevalence of invasive pneumococcal disease in children younger than 2 years old, but, as of 2001, had not had a major impact on decreasing antimicrobial resistance.

Serum Concentrations of Pneumococcal Anticapsular Antibodies in Children with Pneumonia Associated with Streptococcus pneumonia Infection

The levels of specific IgG antibody to pneumococcal capsular polysaccharides were investigated in 182 children, aged 2-5 years, who were hospitalized for community-acquired pneumonia, including 55 (30.2%) with evidence of acute pneumococcal infection. Results show that children with concentrations of specific IgG antibody that would protect against invasive disease do not seem to be protected against pneumonia associated with pneumococcal infection.

Aetiology and Clinical Presentation of Mild Community-Acquired Bacterial Pneumonia

A prospective study was initiated to analyse the bacterial aetiology and clinical picture of mild community-acquired pneumonia in Slovenia using the previously described Pneumonia Severity Index. Radiographically confirmed cases of pneumonia in patients treated with oral antibiotics in seven study centres were included. An aetiological diagnosis was attempted using culture of blood and sputum, urinary antigen testing for Streptococcus pneumoniae and Legionella pneumophila, and antibody testing for Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila in paired serum samples. One hundred thirteen patients were evaluable for clinical presentation and 109 for aetiological diagnosis. At least one pathogen was detected in 62.4% patients. The most common causative agents were Mycoplasma pneumoniae in 24.8%, Chlamydia pneumoniae in 21.1%, and Streptococcus pneumoniae in 13.8% of patients. Dual infection was detected in 8.3% of patients. Most patients suffered from cough, fatigue, and fever. Patients with atypical aetiology of pneumonia differed from those with typical bacterial pneumonia or pneumonia of unknown aetiology in age, presence of dyspnea, and bronchial breathing on lung auscultation. Patients with pneumococcal, chlamydial, and mycoplasmal infections differed in age, risk class, presence of dyspnea, bronchial breathing, and proteinuria. There was an overlap of other clinical symptoms, underlying conditions, and laboratory and radiographic findings among the groups of patients classified by aetiology. Since patients with mild community-acquired pneumonia exhibit similar clinical characteristics and, moreover, since a substantial proportion of cases are attributable to atypical bacteria, broad-spectrum antibiotic treatment seems to be recommended.

Theoretic coverage of heptavalent pneumococcal conjugate vaccine in the prevention of community-acquired pneumonia in children in Italy

In order to evaluate the theoretic coverage of the heptavalent conjugate vaccine against community-acquired pneumonia (CAP) during the first years of life, the anti-capsular IgG antibodies to the nine more common pneumococcal serotypes (1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F) were quantitated in 196 affected children aged 2-5 years by means of enzyme-linked immunosorbent assays of acute and convalescent serum samples. Acute Streptococcus pneumoniae infection associated with the nine tested serotypes was diagnosed in 57 children (29.1%). Serological data indicated that 16.8% of CAPs were caused by serotypes included in the heptavalent conjugate vaccine. This study confirms the significant role of S. pneumoniae in pediatric CAP, and highlights the importance of pneumococcal conjugate vaccines in preventing it during the first years of life.

Paediatric community-acquired pneumonia: current concept in pharmacological control

Community-acquired pneumonia (CAP) is one of the most frequent infections in childhood but it is not easy to establish a rational therapeutic approach for a number of reasons, including difficulties in identifying the aetiology, the fact that the most frequent bacterial pathogens become resistant to commonly used antibiotics and the lack of certain information concerning the possible preventive role of conjugate vaccines. This leads paediatricians to treat almost all cases of CAP with antibiotics, often using a combination of different antimicrobial classes. In order to avoid unnecessary antibiotic use and limit the spread of antibiotic resistance, consensus guidelines for the management of CAP in childhood should be developed and used by practitioners in their offices and hospitals.