Julio Casal

Importance of Local Variations in Antibiotic Consumption and Geographical Differences of Erythromycin and Penicillin Resistance in Streptococcus pneumoniae

ABSTRACT A geographical analysis of how commonly prescribed oral antibiotics are quantitatively and qualitatively responsible for the different local rates of erythromycin and penicillin resistance in Streptococcus pneumoniae in Spain is presented. From 1998 to 1999 a multicenter surveillance study yielded 1,684 consecutive S. pneumoniae isolates from community-acquired respiratory infections. Data on antibiotic sales in the retail market for the same period were gathered, and the corresponding defined doses per 1,000 inhabitants per day were calculated. Macrolides and β-lactams were considered separately. Macrolides were subdivided into thrice-, twice-, and once-a-day macrolides, and β-lactams were split into aminopenicillins and cephalosporins. Univariate Spearman nonparametric coefficients (R) were calculated, and variables proving to be significantly associated (P < 0.1) were entered into several multiple lineal regression models. Ample variation in both resistance rates and antibiotic consumption was seen. Multivariate analyses showed that integrated consumption of both macrolides and β-lactams accounted well for erythromycin (R2 = 0.722; P = 0.002) and penicillin (R2 = 0.706; P = 0.002) resistance. Macrolides were more important drivers for local differences in both erythromycin and penicillin resistance than β-lactams were. Consumption of once-a-day macrolides was key for local erythromycin resistance variations. Cephalosporins were slightly more important penicillin resistance drivers than aminopenicillins were.

Identification of pneumococcal serotypes from culture-negative clinical specimens by novel real-time PCR

Pneumococcal parapneumonic empyema is an increasingly common complication in children. Conventional microbiological cultures indicate bacterial causes in as few as 8% of cases; therefore, there is a vital need for new molecular methods of detection and diagnosis. The development and clinical evaluation of real-time PCR-based assays to detect the pneumococcal capsular wzg gene of all serotypes tested are reported here, and 24 of them have been identified in clinical specimens. Using real-time PCR assays with highly specific TaqMan MGB probes that target DNA sequences within the capsular polysaccharide gene cluster, it was possible to differentiate serotypes 1, 3, 5, 4, 6A, 6B, 7F/A, 8, 9V/A/N/L, 14, 15B/C, 18C/B, 19A, 19F/B/C, 23F and 23A. These assays showed high sensitivity (five to ten pneumococcal DNA equivalents) and they were validated with 175 clinical isolates of known serotypes. The clinical value of this approach was demonstrated by analysis of 88 culture-negative pleural fluids from children diagnosed with parapneumonic empyema in three Spanish hospitals. Pneumococcal DNA was detected in 87.5% of pleural fluids, and serotypes 1, 7F and 3 were responsible for 34.3%, 16.4% and 11.9%, respectively, of cases of parapneumonic empyema in children. Such molecular methods are critical for the diagnosis of invasive pneumococcal disease and continued epidemiological surveillance in order to monitor serotype vaccine effectiveness.

Streptococcus pneumoniae in children in Spain: 1990–1999

This study analyses the serogroups/types (SGTs) and resistance to penicillin and erythromycin of 3921 strains isolated from 1990 to 1999 in children aged 0–14 y in Spanish hospitals of all the autonomous communities. Based on the age of the children, strains have been divided into five groups: 0–6 mo, <6–1 y, <1–2y, <2–5 y and 5 y. While only eight SGTs were responsible for 80% of the infections in children from 6 mo to 2 y of age, this number increased to 11 and 16 for the groups 2–5 y and <5–14 y, respectively. SGTs 6, 14 and 19 were prevalent in blood and otic exudates. SGTs 1, 4, 5, 12 and 18 were more frequent in invasive disease but serotype 3 was clearly associated with otitis. Serotypes 1 and 5 were quite significant in children of over 2 y of age, and this should be taken into account in future vaccine formulations.

Effectiveness of Pneumococcal Vaccination for Elderly People in Catalonia, Spain: A Case-Control Study

BACKGROUND Observational studies offer an approach to evaluating the effectiveness of vaccination programs. We evaluated the effectiveness of a 23-valent pneumococcal vaccination program for elderly people in Catalonia, Spain, in a matched-set case-control study. METHODS We identified 149 cases of invasive pneumococcal disease among patients aged > or =65 years who were hospitalized in 12 large hospitals in Catalonia during the period of 1 January 2001 through 31 March 2002. We selected 2 hospital control patients and 1 outpatient control subject for each case patient, matching on the basis of age and underlying medical conditions. We obtained their pneumococcal vaccination histories and used conditional logistic regression to determine effectiveness of vaccination. RESULTS Among all 149 cases of invasive pneumococcal disease, 131 (87.9%) were caused by vaccine or vaccine-related serotypes. In the adjusted analysis, overall effectiveness of vaccination against infections due to all serotypes was 70% (95% confidence interval [CI], 48%-82%). Among immunocompetent subjects with or without high-risk conditions, effectiveness of vaccination was 76% (95% CI, 51%-88%), but among immunocompromised subjects it was 50% (95% CI, -44% to 82%). Among subjects with infections due to vaccine or vaccine-related serotypes, effectiveness of vaccination was 72% (95% CI, 50%-85%) overall and 78% (95% CI, 50%-90%) in those who were immunocompetent, but it was only 46% (95% CI, -54% to 81%) in those who were immunocompromised. Overall effectiveness of vaccination was 65% (95% CI, 35%-81%) during the noninfluenza period. CONCLUSIONS Pneumococcal vaccination was effective in preventing invasive pneumococcal disease among all elderly persons in Catalonia. Effectiveness was greater in immunocompetent persons, most of whom had underlying high-risk conditions. The number of subjects was too small to determine whether vaccination was effective in those who were immunocompromised.

Pharmacoepidemiological Analysis of Provincial Differences between Consumption of Macrolides and Rates of Erythromycin Resistance among Streptococcus pyogenes Isolates in Spain

ABSTRACT The M phenotype is by far the most common mechanism of erythromycin resistance among Streptococcus pyogenes isolates in Spain. A geographic analysis of the relationship between within-country differences in the prevalence of M-type resistance to erythromycin in S. pyogenes and the level of consumption of 14- and 15-membered macrolides within different provinces was carried out. From 1998 to 1999, a nationwide multicenter surveillance study yielded 2,039 consecutive pharyngeal isolates of S. pyogenes. Data on antibiotic consumption for the same period were gathered from IMS Health, and the corresponding daily defined doses per 1,000 inhabitants per day were calculated according to the Anatomic Therapeutic Classification index. Macrolide use was subdivided into dosages given three times a day (TID), twice a day (BID), or once a day (OD). Spearman nonparametric correlation coefficients (R) were calculated, and variables proving to be significantly associated (P < 0.1) were introduced into a linear regression model. The total consumption of macrolides presented a significant correlation with the prevalence of resistance (R = 0.527; P = 0.032). Neither TID nor BID macrolide consumption showed significant correlations. Only OD consumption had a significance below 0.1. These data are consistent with the hypothesis that only the total consumption of macrolides influences the local rates of M-type erythromycin resistance in S. pyogenes, and subgroups of macrolides seem to have an additive rather than a selective effect by contributing to increasing the final amount of macrolides used. Local variations in total consumption were associated only with BID consumption (R = 0.849; P = 0.004). The simple linear regression with total macrolide consumption showed a considerable determination coefficient (R2 = 0.678; P = 0.006). The model explains up to 68% of the measured variation and is clearly better as a predictor of the prevalence of resistance than the mere mean is. By solving the regression equation, the resultant value of 2.2 defined doses per 1,000 inhabitants per day fits with the existence of a critical threshold of selective pressure.

Optochin-resistant variants of Streptococcus pneumoniae

Ten Streptococcus pneumoniae clinical isolates, possessing physiologically typical pneumococcal characteristics, showed optochin-susceptible and optochin-resistant colonies around the optochin disk, when tested for optochin susceptibility. Equivocal optochin disk test results should be confirmed by bile solubility, agglutination tests, or both.

Identification of atypical strains ofStreptococcus pneumoniae by a specific DNA probe

A specific DNA probe containing a 0.65 Kb fragment coding for the amino-terminal region of the major pneumococcal autolysin (amidase) was constructed, deleting the region involved in the specific recognition of cell wall choline residues. The high specificity of this probe was demonstrated in tests withStreptococcus pneumoniae related species includingStreptococcus oralis, which contains choline in its cell wall. The probe was used to characterize pneumococcal isolates showing atypical responses in conventional identification tests. The hybridization obtained with 27 atypical pneumococci and 11 of 17 isolates presumptively identified as viridans streptococci confirmed that the probe is suitable for diagnostic use.

Identification of the psaA gene, coding for pneumococcal surface adhesin A, in viridans group streptococci other than Streptococcus pneumoniae.

ABSTRACT The gene encoding the pneumococcal surface adhesin A (PsaA) protein has been identified in three different viridans group streptococcal species. Comparative studies of the psaA gene identified in different pneumococcal isolates by sequencing PCR products showed a high degree of conservation among these strains. PsaA is encoded by an open reading frame of 930 bp. The analysis of this fragment inStreptococcus mitis, Streptococcus oralis, andStreptococcus anginosus strains revealed a sequence identity of 95, 94, and 90%, respectively, to the corresponding open reading frame of the previously reported Streptococcus pneumoniae serotype 6B strain. Our results confirm thatpsaA is present and detectable in heterologous bacterial species. The possible implications of these results for the suitability and potential use of PsaA in the identification and diagnosis of pneumococcal diseases are discussed.

Assessment of antibody response elicited by a 7-valent pneumococcal conjugate vaccine in pediatric human immunodeficiency virus infection.

ABSTRACT We investigated antibody responses against pneumococci of serotypes 6B, 14, and 23F in 56 children and adolescents with perinatal human immunodeficiency virus (HIV) infection who were vaccinated with 7-valent pneumococcal conjugate vaccine. Overall immune responses differed greatly between serotypes. Correlation coefficients between immunoglobulin G (IgG) measured by enzyme-linked immunosorbent assay (ELISA) and functional antibodies measured by a flow cytometry opsonophagocytosis assay (OPA) varied with serotype and time points studied. After 3 months of administering a second PCV7 dose we got the highest correlation (with significant r values of 0.754, 0.414, and 0.593 for serotypes 6B, 14, and 23F, respectively) but no significant increase in IgG concentration and OPA titers compared to the first dose. We defined a responder to a serotype included in the vaccine with two criteria: frequency of at least twofold OPA and ELISA increases for each serotype and frequency of conversion from negative to positive OPA levels. Responders varied from 43.9% to 46.3%, 28.5% to 50.0%, and 38.0% to 50.0% for serotypes 6B, 14, and 23F, respectively, depending on the response criterion. The present research highlights the importance of demonstrating vaccine immunogenicity with suitable immunological endpoints in immunocompromised patients and also the need to define how much antibody is required for protection from different serotypes, since immunogenicity differed significantly between serotypes.

Analysis of the Genetic Structure of Nontypeable Pneumococcal Strains Isolated from Conjunctiva

ABSTRACT More than 50% of the nontypeable (NT) pneumococcal strains received in our laboratory for reference purposes are isolated in sporadic cases of conjunctivitis. To determine the genetic structure of the population of these NT conjunctival strains, we analyzed 75 pneumococci (40 NT and 35 typeable) isolated from conjunctivas and 30 (15 NT and 15 typeable) isolated from other sources. The NT and typeable conjunctival strains grouped in separate clusters, whereas NT and typeable pneumococci isolated from other sources were similarly distributed. NT conjunctival strains belonged to two well-differentiated clonal lineages. The first, represented by three newly described sequence types, featured fully antibiotic susceptible strains and appeared to be characteristic of conjunctival tissue; the second, represented by the previously described ST344, had a pattern of multiresistance to penicillin, tetracycline, and erythromycin and shared a genetic background with some NT strains isolated from other sources.