Clementina Canessa

Community-Acquired Bacteremic Pneumococcal Pneumonia in Children: Diagnosis and Serotyping by Real-Time Polymerase Chain Reaction Using Blood Samples

BACKGROUND The aim of this study was to use real-time polymerase chain reaction (RT-PCR) on blood samples to diagnose and serotype pneumococcal infection in a large cohort of Italian children hospitalized for community-acquired pneumonia. METHODS We conducted an observational study from April 2007 through June 2009 of children aged 0-16 years with a diagnosis of community-acquired pneumonia admitted to 83 pediatric hospitals in Italy. RESULTS Seven hundred fifty-three children were studied. RT-PCR found pneumococcal infection in 80 (10.6%) of 753 patients. In 292 patients, culture and RT-PCR were simultaneously performed. Streptococcus pneumoniae was identified in 47 of 292 patients; 45 (15.4%) tested positive by RT-PCR and 11 (3.8%) tested positive by culture. RT-PCR was significantly more sensitive than culture in revealing bacteremic pneumonia (odds ratio, 30.6; 95% confidence interval, 5.8-97.5; P<.001). Complicated pneumonia was found in 162 (21.5%) of 753 children; 152 (93.8%) of these 162 had parapneumonic effusion, and 51 (33.6%) had empyema. Children with complicated pneumonia were significantly older. Pneumococcal bacteremia was found by RT-PCR to occur significantly more frequently in children with complications (38 [23.5%] of 162) than in children with uncomplicated pneumonia (44 [7.4%] of 591; odds ratio, 3.8; 95% confidence interval, 2.30-6.30; P<.001). RT-PCR allowed serotyping from blood in 92.5% of patients. More than two-thirds of the pneumonia cases were due to nonpneumococcal conjugate vaccine 7 serotypes. Serotype 1 was the most frequent serotype (26 [32.5%] of 80) and was significantly associated with complications (50.0% in patients with complicated pneumonia vs 18.2% in patients with uncomplicated pneumonia; odds ratio, 4.5, 95% confidence interval, 1.48-14.03; P=.005) and older age. Serotype 19A was second in frequency (15.0%) and was significantly associated with younger age. CONCLUSIONS RT-PCR allows diagnosis and serotyping of pneumococcal bacteremic community-acquired pneumonia in children and is an important tool for evaluating serotype distribution in culture-negative samples.

Realtime PCR Is More Sensitive than Multiplex PCR for Diagnosis and Serotyping in Children with Culture Negative Pneumococcal Invasive Disease

Background Pneumococcal serotyping is usually performed by Quellung reaction, considered the gold standard test. However the method cannot be used on culture-negative samples. Molecular methods can be a useful alternative. The aim of the study was to evaluate the use of Multiplex-sequential-PCR (MS-PCR) or Realtime-PCR on blood samples for diagnosis and serotyping of invasive pneumococcal disease (IPD) in a pediatric clinical setting. Methodology/Principal Findings Sensitivity and specificity of MS-PCR and Realtime-PCR have been evaluated both on 46 well characterized pneumococcal isolates and on 67 clinical samples from children with culture-negative IPD. No difference in sensitivity and specificity between MS-PCR and Realtime PCR was found when the methods were used on isolates: both methods could type 100% isolates and the results were always consistent with culture-based methods. On the contrary, when used on clinical samples 43/67 (64.2%) were typeable by MS-PCR and 61/67 (91.0%) by Realtime-PCR (p = 0.0004,K Cohen 0.3, McNemars p<0.001). Non-typeability by MS-PCR was associated in 18/20 cases (90.0%) with low bacterial load. The difference between the two methods was present both when they were used on normally sterile fluids (respectively 31/33 (93.9%) typeable samples for Realtime-PCR and 24/33 (72.7%) for MS-PCR, p = 0.047, 95%CL 0.03–0.98; K Cohen 0.3; McNemars p = 0.0016) and when they were used on nasopharyngeal swabs (respectively 30/34 (88.2%) typeable samples for Realtime-PCR and 19/34 (55.9%) for MS-PCR, p = 0.007, 95%CL 0.04–0.66); the presence of multiple pneumococcal serotypes in nasopharyngeal swabs was found more frequently by Realtime PCR (19/30; 63.3%) than by Multiplex-sequential PCR (3/19; 15.8%; p = 0.003;95%CL 1.87–39.97). Conclusions/Significance In conclusion, both MS-PCR and Realtime PCR can be used for pneumococcal serotyping of most serotypes/serogroups directly on clinical samples from culture-negative patients but Realtime-PCR appears more sensitive.

Pneumococcal DNA is not detectable in the blood of healthy carrier children by real-time PCR targeting the lytA gene

The diagnosis of invasive pneumococcal disease (IPD) is currently based on culture methods, which lack sensitivity, especially after antibiotic therapy. Molecular methods have improved sensitivity and do not require viable bacteria; however, their use is complicated by reports of low specificity with some assays. The present study investigated the specificity of a real-time PCR targeting lytA for the detection of IPD. A group of 147 healthy children, aged 6 months to 16 years (mean 6.4 years, median 4.9 years, interquartile range 6.4 years), who were in hospital for routine examinations, were tested for pneumococcal carrier status and for the presence of detectable pneumococcal DNA in their blood by real-time PCR targeting the pneumococcal lytA gene. In addition, 35 culture-positive biological samples were analysed. Urine was examined for the presence of pneumococcal DNA and C-polysaccharide antigen. Carriage was detected in 77 of the 147 subjects (52.4 %); however, regardless of carrier status, none of the subjects had a positive result from blood. Analysis of the culture-positive biological samples yielded positive results in 100 % (15/15) of cerebrospinal fluid samples and 95 % (19/20) of blood samples. All urine samples from healthy carriers were negative for DNA, whilst antigenuria was detected in 44/77 carriers (57.1 %). In conclusion, real-time PCR is both sensitive and specific and can be a useful tool in the routine diagnosis of IPD. Its sensitivity, which surpasses that of other methods for this purpose, does not come at the cost of reduced specificity.

Comparison of the effect of antibiotic treatment on the possibility of diagnosing invasive pneumococcal disease by culture or molecular methods: A prospective, observational study of children and adolescents with proven pneumococcal infection

BACKGROUND Detection of Streptococcus pneumoniae in culture specimens in invasive pneumococcal disease (IPD) may be hampered by antibiotic treatment administered before hospital admission. Realtime polymerase chain reaction (RT-PCR) assays do not require viable bacteria and are therefore less influenced by antimicrobial therapy. It is not known how long results of culture or molecular tests remain positive after antibiotic therapy is begun. OBJECTIVE The goal of the current study was to assess, in a pediatric population with a diagnosis of IPD confirmed by laboratory tests (culture and/or RT-PCR assay), the relationship between use of antibiotic therapy before hospital admission and the result of diagnostic methods (culture or molecular techniques) after admission. METHODS This prospective, observational study was conducted from April 2006 through March 2009. All children and adolescents aged 0 to 16 years, admitted to the hospital with a diagnosis of IPD confirmed by culture and/or molecular methods, were included in the study. Previous antibiotic treatment (drug, duration of therapy) was recorded. Primers and probes designed from the pneumococcal autolysin gene (lytA) were used in an RT-PCR assay for detection of S pneumoniae. Antibiotic tolerability, permanent sequelae (after a 6-month follow-up), and deaths were recorded. RESULTS Eighty-three patients (50 males, 33 females; 80 white, 3 Asian; mean age, 4.6 years; median age, 4.0 years; age range, 10 days-16 years) were included in the study. Fifty-four patients presented with pneumonia, 26 with meningitis/sepsis (meningitis, 19; sepsis, 7), and 3 with arthritis. Results of RT-PCR assays were positive in all 83 patients (100.0%), and 28 of the 83 patients (33.7%) also had culture-positive findings. Forty-two of the 83 patients (50.6%) had received antibiotic treatment before hospital admission, and 41 (49.4%) had not received antibiotics. Results of cultures were positive in 9 of the 42 patients with IPD (21.4%) who had received antibiotic treatment and in 19 of the 41 patients with IPD (46.3%) who had not received antibiotics (odds ratio, 3.2; 95% CI, 1.1-9.3; P = 0.03). Molecular methods appeared more sensitive than culture in any type of disease studied but particularly in patients with pneumonia, in whom the difference was statistically significant (P = 0.043). The mean length of antibiotic therapy was 1.4 days (median, 1 day; SD, 0.53 day; range, 1-2 days) for culture-confirmed cases and 4.5 days (median, 4 days; SD, 3.08 days; range, 1-15 days) for cases confirmed by RT-PCR assay (P = 0.002). No adverse reactions to the antibiotics used during home or hospital treatment were found. Two patients with meningitis suffered permanent, severe neurologic sequelae, and 1 girl died of sepsis 3 days after hospital admission. No permanent sequelae were recorded in patients with pneumonia or arthritis. CONCLUSION In these children and adolescents with IPD, the molecular methods used appeared to be more sensitive than culture in any IPD patient, with a higher statistical significance in patients previously treated with antibiotics and in patients with pneumonia.

Distribution of invasive meningococcal B disease in Italian pediatric population: Implications for vaccination timing

Neisseria meningitidis group B (MenB) is a leading cause of meningitis and sepsis. A new vaccine has been recently licensed. The aim of the present study was to evaluate the epidemiology of MenB disease in pediatric age and define the optimal age for vaccination. All patients aged 0-18 years admitted with a diagnosis of meningitis or sepsis to the 83 participating Italian pediatric hospitals were included in the study. Blood and/or cerebrospinal fluid (CSF) samples were tested by Realtime-PCR and/or culture. One hundred and thirty-six cases (mean age 5.0 years, median 2.7) of MenB disease were found. Among these, 96/136 (70.6%) were between 0 and 5 years, 61/136 (44.9%) were between 0 and 2 years. Among the latter, 39/61 (63.9%) occurred during the first year of life with highest incidence between 4 and 8 months. A case-fatality rate of 13.2% was found, with 27.8% cases below 12 months. Sepsis lethality was 24.4%. RT-PCR was significantly more sensitive than culture: 82 patients were tested at the same time by both methods, either in blood or in CSF; MenB was found by RT-PCR in blood or CSF in 81/82 cases (98.8%), culture identified 27/82 (32.9%) infections (Cohens Kappa 0.3; McNemars: p<10⁻⁵). The study shows that the highest incidence of disease occurs in the first year of age, with a peak between 4 and 8 months of life; 30% of deaths occur before 12 months. The results suggest that the greatest prevention could be obtained starting MenB vaccination in the first months of life; a catch-up strategy up to the fifth year of life could be considered. Our results also confirm that Realtime PCR is significantly more sensitive than culture. In those countries where only isolate positive infections are counted as cases, the incidence of MenB infection results highly underestimated.

The inclusion of ADA-SCID in expanded newborn screening by tandem mass spectrometry.

Severe combined immunodeficiency due to adenosine-deaminase defect (ADA-SCID) is usually deadly in childhood because of severe recurrent infections. When clinical diagnosis is done, permanent damages due to infections or metabolite accumulation are often present. Gene therapy, bone marrow transplantation or enzyme replacement therapy may be effective if started early. The aim of this study was to set-up a robust method suitable for screening with a minimized preparation process and with inexpensive running costs, for diagnosing ADA-SCID by tandem mass spectrometry. ADA-SCID satisfies all the criteria for inclusion in a newborn screening program. We describe a protocol revised to incorporate adenosine and 2-deoxyadenosine testing into an expanded newborn screening program. We assessed the effectiveness of this approach testing dried blood spots from 4 genetically confirmed early-onset and 5 delayed-onset ADA-SCID patients. Reference values were established on 50,000 healthy newborns (deoxyadenosine <0.09μmol/L, adenosine <1.61μmol/L). We also developed a second tier test to distinguish true positives from false positives and improve the positive predictive value of an initial abnormal result. In the first 18 months, the pilot project has identified a newborn with a genetically confirmed defect in adenosine deaminase (ADA) gene. The results show that the method having great simplicity, low cost and low process preparations can be fully applicable to a mass screening program.

Potential serotype coverage of three pneumococcal conjugate vaccines against invasive pneumococcal infection in Italian children

BACKGROUND AND AIM OF THE WORK Since the introduction of the 7-valent vaccine, invasive pneumococcal disease have greatly decreased; however, changes in the distribution of pneumococcal serotypes have recently highlighted the need for vaccines with wider coverage. The aim of the work was to assess the potential serotype coverage of three pneumococcal conjugate vaccines (7-, 10- and 13-valent) against bacteremic pneumococcal pneumonia and meningitis/sepsis in Italian children. PATIENTS AND METHODS We determined pneumococcal serotypes in immunocompetent patients who had been admitted to hospital with suspicion of invasive bacterial disease and had confirmed bacteremic pneumococcal pneumonia or meningitis/sepsis determined by molecular detection of Streptococcus pneumoniae in a normally sterile site. Positive samples were serotyped using Realtime-PCR. RESULTS Between April 2008 and March 2011, a total of 144 patients (age median 4.1 years; Interquartile range 1.8-5.6) with pneumococcal meningitis/sepsis (n=43) or pneumonia (n=101) from 83 participating centers located in 19 of 20 Italian regions were serotyped. The 10 most prevalent serotypes were 1 (29.9%), 3 (16.0%), 19A (13.2%), 7F (8.3%), 5 (4.2%), 14 (4.2%), 6A (3.5%), 6B (3.5%), 18C (3.5%), 19F (3.5%). Overall, serotype coverage for PCV-7, -10 and -13 were respectively 19.4%, 61.8% and 94.4% with no statistical difference between pneumonia and meningitis/sepsis. Potential coverage was similar for children 0-2 or 2-5 years of age. Cultures resulted positive in 35/99 (35.4%) samples simultaneously obtained for both culture and RT-PCR. CONCLUSION These findings indicate that increasing the potential serotype coverage by introducing PCV13 in the vaccination schedule for infancy could provide substantial added benefit for protection from pneumococcal pneumonia or meningitis/sepsis in Italy in children below 2 years as well in older children. The importance of molecular methods for diagnosis and serotyping of invasive pneumococcal disease was confirmed.

Pneumococcal serotype distribution in adults with invasive disease and in carrier children in Italy: Should we expect herd protection of adults through infants' vaccination?

ABSTRACT The 7-valent pneumococcal conjugate vaccine (PCV7) produced a significant herd protection in unvaccinated adult population mostly because of pneumococcus carriage decrease in vaccinated children. It is not known if the 13-valent pneumococcal vaccine can give similar effect on adults. Aims of the work were to evaluate whether the 6 additional serotypes are present in nasopharynx of children and serotype distribution in invasive pneumococcal infections (IPD) in adults.  Realtime-PCR was used to evaluate pneumococcal serotypes in adults with confirmed IPD and in nasopharyngeal swabs (NP) from 629 children not vaccinated or vaccinated with PCV7 and resident in the same geographical areas. Two hundred twenty-one patients (116 males, median 67.9 years) with IPD were studied (pneumonia n = 103, meningitis n = 61 sepsis n = 50, other n = 7). Two hundred twelve were serotyped. The most frequent serotypes were 3, (31/212; 14.6%), 19A, (19/212; 9.0%), 12 (17/212; 8.0%), 7F, (14/212; 6.6%). In NP of children, the frequency of those serotypes causing over 50% of IPD in adults was very low, ranging from 0.48% for serotype 7F to 7.9% for serotype 19A. On the other side serotype 5, very frequent in NP (18.7%) caused <1% IPD. In conclusion serotypes causing IPD in adults are very rarely found in children NP. We suggest that herd protection obtainable with the additional 6 serotypes included in PCV13 may be more limited than that demonstrated with PCV7 in the past. In order to reduce the burden of disease in adults, adults should be offered a specific vaccination program with highly immunogenic PCV.

Underestimation of Invasive Meningococcal Disease in Italy

Underestimation is attributable to misdiagnosis, especially in fatal cases, and use of insufficiently sensitive laboratory methods.

Impact on disease incidence of a routine universal and catch-up vaccination strategy against Neisseria meningitidis C in Tuscany, Italy.

BACKGROUND Invasive infections due to Neisseria meningitidis are still an important public health issue worldwide. In Europe, meningococcal meningitis is differently distributed in the EU countries, but most cases of meningococcal diseases are caused by serogroups B and C. In Italy, each year about 900 cases of bacterial meningitis occur, of whom one third are caused by N. meningitidis. In March 2005, the Regional Health Authority of Tuscany approved a policy of active offer of conjugate meningococcus C (MCC) vaccination with three doses to all newborns at 3, 5 and 13 months of age (subsequently turning to a single dose at 13 months as of 2008) and a catch-up until age 6 years with a single dose. OBJECTIVE The aim of the present study was to evaluate the effectiveness of the vaccination strategy adopted by Tuscany in preventing cases of invasive meningococcal C disease. METHODS Surveillance data for the calculation of disease incidence, immunization coverage with MCC vaccine and vaccination status of meningitis cases were collected from 2005 to 2011. RESULTS Incidence rates of meningococcal meningitis and septicemia decreased in all age groups involved in the immunization campaign, as a result of the progressively increasing vaccination coverage. Since 2006, no cases of invasive meningococcal C infection in vaccinated subjects were observed in Tuscany. A herd immunity effect was measured in unvaccinated age groups. CONCLUSION MCC vaccination implementation in Tuscany was successful in the prevention of meningococcal C disease. Our results should prompt all Italian Regions to consider introducing MCC vaccination in order to protect their population.