Capsular type distribution and susceptibility to antibiotics of Streptococcus pneumoniae clinical strains isolated from Uruguayan children with systemic infections. Pneumococcus Study Group

Evolution of the β-lactam-resistant Streptococcus pneumoniae PMEN3 clone over a 30 year period in Barcelona, Spain

Objectives

To analyse the epidemiology and genetic evolution of PMEN3 (Spain9V-156), a penicillin-non-susceptible clone of Streptococcus pneumoniae, causing invasive pneumococcal disease (IPD) in Barcelona during 1987-2016.

Methods

WGS was performed on 46 representative isolates and the data were used to design additional molecular typing methods including partial MLST, PCR-RFLP and detection of surface-exposed proteins and prophages, to assign the remaining isolates to lineages. The isolates were also subjected to antimicrobial susceptibility testing.

Results

Two hundred and twenty-seven adult cases of IPD caused by PMEN3 were identified. PMEN3 caused mainly pneumonia (84%) and the 30 day mortality rate was 23.1%. Evidence of recombination events was found, mostly in three regions, namely the capsular operon (associated with capsular switching) and adjacent regions containing pbp2x and pbp1a, the murM gene and the pbp2b-ddl region. Some of these genetic changes generated successful new variant serotype lineages, including one of serotype 11A that is not included in the current PCV13 vaccine. Other genetic changes led to increased MICs of β-lactams. Notably, most isolates also harboured prophages coding for PblB-like proteins. Despite these adaptations, the ability of this clone to cause IPD remained unchanged over time, highlighting the importance of its core genetic background.

Conclusions

Our study demonstrated successful adaptation of PMEN3 to persist over time despite the introduction of broader antibiotics and conjugate vaccines. In addition to enhancing understanding of the molecular evolution of PMEN3, these findings highlight the need for the development of non-serotype-based vaccines to fight pneumococcal infection.

Effect of pneumococcal conjugate vaccination in Uruguay, a middle-income country

Background

In 2008, a 7-valent pneumococcal conjugate vaccine (PCV7) was introduced into the routine childhood immunization program in Uruguay, with a 2+1 schedule. In 2010, PCV13 replaced PCV7, and the same 2+1 schedule was used. The effect of these pneumococcal vaccines on the incidence of invasive pneumococcal infections (IPD) and on serotype distribution was analyzed retrospectively, based on passive national laboratory surveillance.

Methods

Data from 1,887 IPD isolates from 5 years before and 5 years after PCV7 introduction (7 before and 3 after PCV13 introduction) was examined to assess the incidence rate per 100,000 age-specific population of all IPD, PCV7-serotypes, and PCV13-serotypes associated IPD among children <2 years and 2 to 4 years old, and patients ≥5 years old. Trends of frequency for each serotype were also analyzed.

Results

Comparison of pre-vaccination (2003–2007) and post-vaccination (2008–2012) periods showed a significant decrease in IPD incidence among children <2 years old (IR 68.7 to IR 29.6, p<0.001) and children 2 to 4 years (p<0.04). IPD caused by serotypes in PCV7 was reduced by 95.6% and IPD caused by 6 serotypes added in PCV13 was reduced by 83.9% in children <5 years old. Indirect effects of both conjugate vaccines were observed among patients ≥5 years old one year after the introduction of each vaccine, in 2010 for PCV7 and in 2012 for PCV13. Nevertheless, for reasons that still need to be explained, perhaps due to ascertainment bias, total IPD in this group increased after 2007. In 2012, the relative frequency of vaccine serotypes among vaccinated and unvaccinated population declined, except for serotype 3. Non vaccine serotypes with increasing frequency were identified, in rank order: 12F, 8, 24F, 22F, 24A, 15C, 9N, 10A and 33.

Conclusion

Consecutive immunization with PCV7 and PCV13 has significantly reduced IPD in children <5 years of age in Uruguay.

Streptococcus pneumoniae serotype 19A in Latin America and the Caribbean: a systematic review and meta-analysis, 1990-2010

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) are in the process of implementation in Latin America. Experience in developed countries has shown that they reduce the incidence of invasive and non-invasive disease. However, there is evidence that the introduction of PCVs in universal mass vaccination programs, combined with inappropriate and extensive use of antibiotics, could be associated to changes in non-PCV serotypes, including serotype 19A. We conducted a systematic review to determine the distribution of serotype 19A, burden of pneumococcal disease and antibiotic resistance in the region.

METHODS

We performed a systematic review of serotype 19A data from observational and randomized clinical studies in the region, conducted between 1990 and 2010, for children under 6 years. Pooled prevalence estimates from surveillance activities with confidence intervals were calculated.

RESULTS

We included 100 studies in 22 countries and extracted data from 63. These data reported 19733 serotyped invasive pneumococcal isolates, 3.8% of which were serotype 19A. Serotype 19A isolates were responsible for 2.4% acute otitis media episodes, and accounted for 4.1% and 4.4% of 4,380 nasopharyngeal isolates from healthy children and in hospital-based/sick children, respectively. This serotype was stable over the twenty years of surveillance in the region. A total of 53.7% Spn19A isolates from meningitis cases and only 14% from non meningitis were resistant to penicillin.

CONCLUSIONS

Before widespread PCV implementation in this region, serotype 19A was responsible for a relatively small number of pneumococcal disease cases. With increased use of PCVs and a greater number of serotypes included, monitoring S. pneumoniae serotype distribution will be essential for understanding the epidemiology of pneumococcal disease.

Features of bacterial growth and polysaccharide production of Streptococcus pneumoniae serotype 14

The effect of several cultivation conditions on the kinetics of bacterial growth and polysaccharide production of Streptococcus pneumoniae serotype 14 was studied. The presence in the supernatant of serotype-specific CPS (capsular polysaccharide) during growth was followed by size-exclusion HPLC and, in parallel, confirmed by using a specific latex reagent. The agitation level did not affect the production behaviour, whereas pH maintenance above 6 strongly enhanced both growth and CPS production throughout the cultivation period in flasks. Production of high-molecular-mass polysaccharide was found to be maximal between 5 and 6 h of cultivation, at the end of the exponential phase. By laser light scattering, 90% of this purified CPS product showed a M(w) (molecular mass) range from 350 to 1500 kDa, with an average M(w) of 921 kDa. Extending the culture to 24 h gave rise to a clear shift of the M(w) distribution of the polysaccharide to values lower than 100 kDa. These findings may have strong implications for the large-scale manufacture of the polysaccharide and the associated conjugate vaccine.

Ampicillin and penicillin concentration in serum and pleural fluid of hospitalized children with community-acquired pneumonia

BACKGROUND

Optimal therapeutic efficacy of beta-lactam antibiotics for treatment of pneumococcal pneumonia is thought to be associated with the serum concentration greater than the minimum inhibitory concentration for 40-50% of the interdose interval at site of infection.

OBJECTIVE

Establish whether intravenous administration of ampicillin 400 mg/kg/day or penicillin 200,000 IU/kg/day in 6 divided doses reaches serum and or pleural concentrations above 4 microg/ml for at least 40% of the interdose interval.

MATERIALS AND METHODS

Hospitalized healthy children 1 month-14 years old with community-acquired bacterial pneumonia and empyema were eligible. Blood samples were obtained 30 min (C1) and 3 h (C2) after an antibiotic dose. Pleural fluid samples were obtained 1 and 4 h after the same dose in which blood samples were obtained. The concentrations were measured by high performance liquid chromatography.

RESULTS

The study included 17 patients treated with ampicillin and 13 treated with penicillin. For ampicillin, mean serum concentrations were C1 37.3 +/- 19 microg/ml and C2 11 +/- 10.2 microg/ml and mean pleural fluid concentrations were C1 25.8 +/- 9.9 microg/ml and C2 16.2 +/- 7.9 microg/ml. For penicillin, mean serum concentrations were C1 21.8 +/- 16.4 microg/ml and C2 23.9 +/- 3.4 microg/ml. Mean pleural fluid concentrations were C1 10.9 +/- 2.2 microg/ml and C2 7.7 +/- 3.4 microg/ml. In 8 of 30 patients, serum C2 was <4 microg/ml; in all of them serum concentrations were >4 microg/ml for >40% of the interdose interval.

CONCLUSIONS

This study of the pharmacokinetics of beta-lactam antibiotics in children with bacterial pneumonia may help in the development of therapeutic guidelines for the treatment of pneumococcal pneumonia.

Preparative purification of soybean agglutinin by affinity chromatography and its immobilization for polysaccharide isolation

Optimized procedures for the affinity purification of soybean agglutinin (SBA) from soybean flour, and its further immobilization, were developed. Lectin purification on galactosyl-Sepharose yielded 44.5+/-3.5 mg of pure SBA/50 g of flour. To prepare SBA adsorbents, the lectin was immobilized onto 1-cyano-4-(dimethylamino)pyridinium tetrafluoroborate (CDAP) activated Sepharose with high yields (77%). Feasibility of the use of this improved SBA adsorbent for affinity purification of Streptococcus pneumoniae capsular polysaccharides from strain 14 (CPS-14) at laboratory scale was demonstrated. Using SBA-Sepharose adsorbent (7.0 mg lectin per ml), amounts of 6.3 mg of pure CPS-14 per cycle were produced, the adsorbent being reused up to four times without loss of capacity.

Antimicrobial susceptibilities and serotype distribution of Streptococcus pneumoniae isolates from a Low socioeconomic area in Lima, Peru

Streptococcus pneumoniae isolates were obtained from nasopharyngeal swabs taken from children living in a low socioeconomic area of Lima, Peru, to determine the rates of antimicrobial resistance and serotype distribution. A total of 146 nasopharyngeal isolates were collected from children from 3 to 38 months of age. Twenty-one clinical laboratory isolates from both sterile and nonsterile sites were obtained from a local hospital. Isolates with reduced susceptibilities to penicillin represented 15.1 and 42.9% of the nasopharyngeal and clinical isolates, respectively. For neither group of isolates did penicillin MICs exceed 1.5 micro g/ml, indicating only intermediate resistance. Thirty-two different serotypes were identified from the 146 nasopharyngeal isolates. The serotypes of the clinical isolates were represented among those 32 types. Isolates with reduced susceptibility to multiple antimicrobial agents were present in both settings. These findings indicate some of the highest rates of antimicrobial resistance in the region as well as a slightly different serotype distribution pattern from those of other South American countries. The 7-valent conjugate pneumococcal vaccines would only have a limited effect, providing coverage for about half of all isolates. Increasing rates of resistance in Peru necessitate an awareness of antimicrobial treatment practices and vaccination strategies.

Dissemination of Streptococcus pneumoniae clone Colombia(5)-19 in Latin America

Streptococcus pneumoniae serotype 5 is the third most common capsular type causing invasive diseases in children younger than 5 years in Latin America. Preliminary data on Colombian serotype 5 isolates indicated a common clonal origin associated with resistance to tetracycline (TET) and chloramphenicol (CHL). We studied 172 S. pneumoniae serotype 5 invasive isolates from Argentina, Brazil, Colombia, Guatemala, Mexico, and Uruguay and confirmed the presence of the Colombia(5)-19 clone throughout Latin America. Fifteen subtypes of a pulsed-field gel electrophoresis pattern and 4 electrophoretic types (ET) were obtained. Most of the isolates from different geographical regions belonged to pattern A (34.3%), subtype A5 (41.9%), and ET1 (91.1%). The A pattern (n = 59) was resistant to TET and had variable resistance to CHL; it was present in Brazil (10.2%), Colombia (78%), Guatemala (8.5%), and Mexico (3.4%). Subtype A5 with variable susceptibility to TET and sensitive to CHL was found in Argentina (29.2%), Mexico (8.3%), and Uruguay (62.5%). Subtypes A1-A4, A7-A8, and A9-A11 (closely related to A) also shared ET1, while subtype A6 was assigned to ET1, ET2, and ET3. Eleven subtypes (n = 21) were found to be specific for one country each. In summary, the S. pneumoniae serotype 5 isolates from Latin American are genetically closely related but show different patterns of antibiotic resistance, probably as a result of horizontal transfer.

Antibiotic resistance in Streptococcus pneumoniae in six Latin American countries: 1993-1999 surveillance

The impact of invasive pneumococcal invasive disease is increased by the emergence of antibiotic resistance. We report regional and temporal variations in antibiotic resistance for 4,105 invasive Streptococcus pneumoniae isolates collected from Latin American children <5 years, between 1993 and 1999. Reduced susceptibility to penicillin was detected in 1,182 isolates (28.8%); 36% of these were resistant (> or = 2 microg/ml), including 12.6% with MIC > or = 4 microg/ml, occurring primarily in serotypes 14 and 23F. Reduced susceptibility to third-generation cephalosporins was detected in 12.1% of the collection. Mexico had the highest proportion of reduced susceptibility to penicillin (51.6%) and to third-generation cephalosporins (22%), whereas Brazil had the lowest at 20.9% and 0.7%, respectively. Isolates cultured from patients with pneumonia were more likely to have reduced susceptibility to third-generation cephalosporins than isolates from patients with meningitis (p < 0.0001). Susceptibility to trimethoprim-sulfamethoxazole, chloramphenicol, erythromycin, and vancomycin was tested by disk diffusion for 2.899 isolates. Reduced susceptibility was observed for 45.6%, 11.5%, 6.9%, and 0%, respectively. Thirty-one percent of the strains were resistant to > or = 2 drugs. High levels of antibiotic resistance in Latin America emphasize the need for the development of and adherence to rational antibiotic use guidelines. On-going surveillance will monitor the impact of these programs.

Population-based survey of antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae from meningitis patients in Salvador, Brazil

Penicillin-nonsusceptible strains were isolated from 15% of 303 individuals with pneumococcal meningitis identified during a 4-year surveillance study in Salvador, Brazil. The estimated rate of coverage of the seven-valent conjugate vaccine was 74% among patients <5 years of age and 94% among those infected with nonsusceptible isolates, indicating that the use of conjugate vaccines may be an approach to the control of emerging penicillin resistance in Brazil.

Evolution of Streptococcus pneumoniae serotypes and penicillin susceptibility in Latin America, Sireva-Vigía Group, 1993 to 1999. PAHO Sireva-Vigía Study Group. Pan American Health Organization

BACKGROUND

Since 1993 the Pan American Health Organization has coordinated a surveillance network with the National Reference Laboratories of Argentina, Brazil, Chile, Colombia, Mexico and Uruguay aimed at monitoring capsular types and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive disease in children <6 years of age.

METHODS

The surveillance system included children 6 years of age and younger with invasive disease caused by S. pneumoniae. The identification, capsular typing and susceptibility to penicillin of the isolates were conducted using a common protocol, based on standard methodologies.

RESULTS

By June, 1999, 4,105 invasive pneumococcal isolates had been collected mainly from pneumonia (44.1%) and meningitis (41.1%) cases. Thirteen capsular types accounting for 86.1% of the isolates (14, 6A/6B, 5, 1, 23F, 19F, 18C, 19A, 9V, 7F, 3, 9N and 4) remained the most common types during the surveillance period. Diminished susceptibility to penicillin was detected in 28.6% of the isolates, 17.3% with intermediate and 11.3% with high level resistance. Resistance varied among countries and increased during this period in Argentina, Colombia and Uruguay. Serotypes 14 and 23F accounted for 66.6% of the resistance.

CONCLUSION

These surveillance data clearly demonstrate the potential impact of the introduction of a conjugate vaccine on pneumococcal disease and the need for more judicious use of antibiotics to slow or reverse the development of antimicrobial resistance.

Standard case management of pneumonia in hospitalized children in Uruguay, 1997 to 1998

OBJECTIVE

To report the results of the use of antimicrobial guidelines for the management of children with community-acquired bacterial pneumonia.

METHODS

Admittance and discharge criteria and algorithms for diagnosis and treatment were established. The decision to treat with antibiotics was based on radiologic findings in pneumonia with pulmonary consolidation and left to the attending physician's criteria in the remaining cases. The use of antibiotics was limited to penicillin and derivatives (ampicillin, amoxicillin) and macrolides.

RESULTS

Of the 1163 children treated as bacterial pneumonia, hospitalized in public and private health facilities in Montevideo from September, 1997, through September, 1998, standard case management was applied in 1082 (93%). Age distribution was: <1 month, 1%; between 1 and 11 months, 29%; between 1 and 5 years, 50%; >5 years, 20%. Chest radiography showed evidence of pulmonary consolidation in 843 children (73%). Bacteria were detected in blood culture and/or pleural fluid of 57 children (5%). In 51 the identified microorganism was Streptococcus pneumoniae, susceptible to penicillin in 30, intermediate in 6 and resistant in 5 (maximum MIC, 4 microg/ml); in 10 cases etiologic diagnosis was made by antigen detection. Empyema was present in 62 children (5.3%); 38 (3.27%) required treatment in an intensive care unit; and 5 (0.4%) died.

CONCLUSIONS

Compliance with standard case management was highly satisfactory. Outcome of children treated with penicillin and derivatives was good, including children with empyema and pneumatocele and two patients with penicillin-resistant S. pneumoniae. At the present time S. pneumoniae resistant to penicillin is not an important problem in children with pneumonia in Uruguay. Surveillance of identified microorganisms and their antimicrobial susceptibility must continue.

Production of capsular polysaccharide of Streptococcus pneumoniae type 14 and its purification by affinity chromatography

We describe a rapid and efficient method for producing the capsular polysaccharide of Streptococcus pneumoniae by fermentation on tryptic soy broth and purification of this compound by using immobilized soybean lectin as an affinity adsorbent. In principle, the same strategy can be used to produce purified capsular polysaccharides from other streptococcal serotypes by selecting the appropriate lectin adsorbents.

Frequency of penicillin-resistant pneumococci in children is correlated to community utilization of antibiotics

OBJECTIVE

To study the impact of the utilization of antibiotics in children at the population level on the frequency of penicillin-nonsusceptible pneumococci (PNSP).

DESIGN

Children ages 0 to 6 years with a nasopharyngeal culture of PNSP were registered on place of residency in the 20 municipalities of the former Malmöhus County (since 1998 a part of Skåne County). Where possible the total number of nasopharyngeal cultures with growth of pneumococci was registered as well. All antibiotic prescriptions for 0- to 6-year-old children were analyzed in the 20 municipalities.

MAIN OUTCOME MEASURES

Correlation between the utilization of antibiotics and the frequency of PNSP in children at the municipality level.

RESULTS

The proportion of PNSP among all isolates of pneumococci from nasopharyngeal cultures varied between 0 and 49.5%. The antibiotic utilization in children varied among the 20 neighboring municipalities from 8.5 to 19.7 defined daily doses per 1000 children per day. The municipalities with high total utilization also had more frequent use of macrolides and broad spectrum antibiotics. The was a significant correlation between antibiotic use and the proportion of PNSP (correlation coefficient, 0.96; P = 0.002), and the correlation coefficients for trimethoprim-sulfamethoxazole, amoxicillins, macrolides and cephalosporins were significant at the 0.001 level. There was no significant correlation between the use of penicillin V and the frequency of PNSP. CONCLUSIONS. There was a significant correlation between the frequency of PNSP and the utilization of antibiotics in children at the population level.

Susceptibility of 1100 Streptococcus pneumoniae strains isolated in 1997 from seven Latin American and Caribbean countries. Laser Study Group

The antimicrobial susceptibility to beta-lactam and non-beta-lactam agents of 1100 isolates of Streptococcus pneumoniae recovered in 1997 from 16 centres in Argentina, Brazil, Chile, Mexico, Panama, Venezuela and West Indies was studied using E-test and disk diffusion methods. A total of 23.6% of isolates had raised penicillin MICs (16.7% intermediate and 6.9% resistant). The susceptibility of the other agents tested, from most active to least active, were, amoxycillin/clavulanate (99.5% susceptible); chloramphenicol (93.2%); cefotaxime (91.7%); erythromycin (87.1%); tetracycline (74.6%); trimethoprim/sulphamethoxazole (TMP-SMZ) (55.4%); and cefaclor (52.8%). The highest proportion of strains resistant to penicillin, chloramphenicol, erythromycin, tetracycline and TMP-SMZ was found in strains from Mexico while resistance to these agents was lowest in strains from the West Indies. Prevalence of penicillin resistance (including intermediate and resistant isolates) in each of the countries, from highest to lowest was, Mexico (40.8%); Chile (31.3%); Panama (23.0%); Venezuela (21.9%); Argentina (19.1%); Brazil (12.9%); and West Indies (7.1%). Based on current levels of antimicrobial resistance of S. pneumoniae in Latin American and Caribbean countries, continued surveillance efforts are necessary in order to guide clinical empiric treatment and provide for judicious use of antimicrobial agents.

Ten-year review of invasive pneumococcal diseases in children and adults from Uruguay: clinical spectrum, serotypes, and antimicrobial resistance

OBJECTIVES

Since 1987, the Reference Laboratory of the Ministry of Health of Uruguay has been monitoring infections due to Streptococcus pneumoniae in patients under 5 years of age, in those between 5 to 14 years of age, and in adults. The purpose of the present study was to retrospectively analyze a 10-year collection of invasive S. pneumoniae isolates from children 5 to 14 years of age and adults.

METHODS

The Reference Children's Hospital, Pasteur Hospital, and two private hospitals in Montevideo as well as four hospitals located in other representative areas of the country participated in the pneumococcal surveillance program. Based on the information available at the Microbiology Department of the Central Public Health Laboratory (demographic data, date and site of isolate, and clinical diagnosis), all patients with an invasive pneumococcal disease were recorded. Pneumonia was clinically and radiologically diagnosed and etiology was assessed by isolation of S. pneumoniae from blood or pleural fluid. All specimens were collected at the Emergency Service. Capsular serotyping and antimicrobial susceptibilities were determined for each isolate.

RESULTS

During the 10-year period, 228 invasive S. pneumoniae were identified and included in the study (blood, n = 129; cerebrospinal fluid [CSF], n = 73; pleural fluid, n = 20; peritoneal fluid, n = 3; synovial fluid, n = 1; pericardic fluid, n = 1; abscess, n = 1). The most frequent clinical presentations were pneumonia (n = 71) and meningitis (n = 69). Thirty-five adults had an underlying condition including, four with malignancies, four with lupus, two with human immunodeficiency virus (HIV)-infected, and two patients in hemodialysis among others. Eighteen of the 228 patients died (7.9% fatality rate), but only four of these had an underlying condition. Eleven fatal cases were attributable to meningitis (2 children, 9 and 11 years old; 9 adults, mean age, 59 y). Four patients with pneumonia and three with sepsis died, including a splenectomized woman. Nine different capsular serotypes (1, 5, 7, 9, 12, 15, 19A, 20, and 23A) were identified among the 18 fatal cases. Resistance to penicillin, generally combined with trimethoprim-sulfamethoxazole, fluctuated annually, not surpassing 10%.

CONCLUSIONS

The study results indicated that 96% of the serotypes involved in severe pneumococcal diseases were included in the 23-valent vaccine and that S. pneumoniae resistance to penicillin was moderate.

Penicillin-resistant Streptococcus pneumoniae in Argentina: frequent occurrence of an internationally spread serotype 14 clone

Six Latin-American countries participated in an epidemiological surveillance study conducted by the Pan American Health Organization in order to determine the relative prevalence of capsular types and antimicrobial resistance patterns of Streptococcus pneumoniae (SPN) causing invasive infections in children <5 years of age. In Argentina, the incidence of penicillin resistance (PR) was 24.4%, and it was significantly associated with serotype 14 (p < 0.001). The chromosomal DNA of 56 of those SPN isolates, 39 PR and 17 susceptible, was digested with SmaI and resolved by PFGE. Eighty-two percent (32/39) of the PR isolates shared characteristics with the widely spread International Spanish/French clone (clone B). All members of clone B except one expressed serotype 14, with the exception of one isolate that expressed serotype 19F and probably resulted from an in vivo capsular transformation event. Only a single isolate shared features with the 23F International Spanish/USA clone (clone A). The 17 penicillin-susceptible (PS) SPN isolates presented an enormous degree of variation in the chromosomal background, expressing 12 serotypes and 13 PFGE patterns. The data suggest that over 80% of the SPN-PR isolates in Argentina were imported, and this confirms the importance of the geographic spread of SPN clones in South America.

Geographic distribution of penicillin resistance of Streptococcus pneumoniae in Brazil: genetic relatedness

From January 1993 through December 1996, 1,252 Streptococcus pneumoniae strains from different geographic regions of Brazil were studied for penicillin (Pen) susceptibility. All pneumococci were isolated from normally sterile fluids from patients, newborns to 88 years old. Pen resistance (R) had a mean rate of 15.1%, with 14.5% of strains showing intermediate level Pen-R and 0.6% showing high-level Pen-R. Similar Pen-R rates were observed in different regions of the country, in the range of 9.5% to 17.1%. A Pen-R increase was noted from 9.6% in 1993 to 20.6% in 1996. Pen-R was mostly associated to serotypes 6B, 14, 19A, and 23F (89%). Chromosomal DNA relatedness of Pen-R strains was determined by pulsed field gel electrophoresis (PFGE). High genetic diversity was identified, being represented by 27 patterns among the 92 strains. Two important features were observed: the predominance of relatively low-level Pen MIC (range 0.1-0.5 mg/L) in 86 of the 92 strains, and the presence of 60.8% as four major PFGE clusters unique to Brazil. Another feature was the geographic spread of these clusters over large distances in the country. The city of São Paulo seems to be a Pen-R focus (18.4%) in Brazil. Only two strains representing the international clone B widely spread in France, Portugal, and Spain, belonging to serotype 14, were found.

The apparent importation of penicillin-resistant capsular type 14 Spanish/French clone of Streptococcus pneumoniae into Uruguay in the early 1990s

Since 1987, Streptococcus pneumoniae (SPN) has been monitored in pediatric and adult populations. In 1994, the SIREVA/PAHO surveillance allowed the assessment of a dramatic increase of penicillin resistance, mainly associated to SPN type 14 also resistance to trimethoprim/sulfamethoxazole. To determine the genetic relatedness of the resistant isolates, analysis of SmaI digests of 61 isolates was performed by pulsed field gel electrophoresis (PFGE). Twelve different profiles were identified. The type 14 resistant SPN (n = 47) displayed a common B pattern, with 15 genetically related subtypes (1-6 bands of difference), with B1 the predominant one (51%). One of the subtypes (B12) was indistinguishable from a French isolate (M13P). This strain represented a South European clone, identified in the late 1980s, that also included serogroup 9 isolates. The type 23F isolates (n = 3) were identical with a representative strain of the well-characterized intercontinental type 23F clone. Neither the type 14 penicillin-susceptible (n = 4) nor the resistant SPN of other serotypes (n = 10) belonged to the B pattern. In summary, the results suggest that the dramatic increase of penicillin resistance in Uruguay depends on the introduction and spread of a type 14 clone, apparently imported from the south of Europe. Follow-up of this phenomenon is mandatory from the point of view of epidemiology and is also a priority for biologic research.

Predominance of the multiresistant 23F international clone of Streptococcus pneumoniae among isolates from Mexico

During a surveillance study to determine the relative prevalence of capsular types of Streptococcus pneumoniae and antimicrobial susceptibility of invasive isolates in children <5 years old in Mexico City, 220 isolates were collected. The serotype 23F was the most common found, followed by types 6A + B, 14, 19F, and 19A. Diminished susceptibility to penicillin was detected in 106 isolates (48.2%), and high penicillin resistance was found in 49 strains (22.2%), 31 belonging to type 23F. Resistance was also observed to erythromycin (13.1%), to chloramphenicol (43.1%), and to cefotaxime (10.9%). No strains were resistant to ofloxacin or vancomycin. Forty-four of the highly penicillin resistant isolates (penicillin MIC > or =2.0 microg/ml) were examined with molecular fingerprinting techniques; 29 (65.9%) of these isolates (all except two strains) were serotype 23F and shared subtype variants of PFGE type A characteristic of the internationally spread Spanish/USA clone of S. pneumoniae. These strains were also resistant to trimethoprim/sulfametoxasole (TMP/SMX), chloramphenicol, and tetracycline, and most of them were susceptible to erythromycin. Another 6 of the highly penicillin-resistant strains (serogroups 9 and 14) showed PFGE fingerprints and antimicrobial susceptibility pattern characteristic of a second internationally spread clone (French/Spanish clone) and carried resistance to penicillin and TMP/SMX. The rest of the 9 penicillin-resistant isolates were represented by 7 distinct additional PFGE types. The findings suggest that almost 80% of all highly penicillin resistant strains may have been "imported" into Mexico.

The contribution of specific pneumococcal serogroups to different disease manifestations: implications for conjugate vaccine formulation and use, part II

To assess whether certain serogroups of Streptococcus pneumoniae are preferentially associated with specific disease manifestations, we analyzed all recent pneumococcal disease studies and assessed the relative frequency of isolation of each serogroup by clinical site (as a proxy for different disease states). In all age groups, serogroups 1 and 14 were more often isolated from blood, and serogroups 6, 10, and 23 were more often isolated from cerebrospinal fluid (CSF); in young children, serogroups 3, 19, and 23 were more often isolated from middle ear fluid (MEF). Serogroups represented in conjugate vaccines were isolated slightly less frequently from CSF than from blood or MEF. Nonetheless, serogroups in the 9-valent conjugate vaccine formulation still comprised approximately 75% of pneumococcal isolates from the CSF of young children in Europe and in the United States and Canada. These analyses indicate that pneumococcal conjugate vaccines could potentially prevent a substantial proportion of episodes of bacteremic disease, pneumonia, meningitis, and otitis media, especially in young children.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.

Dissemination of a chloramphenicol- and tetracycline-resistant but penicillin-susceptible invasive clone of serotype 5 Streptococcus pneumoniae in Colombia

A national surveillance conducted in Colombia between 1994 and 1996 identified serotype 5 Streptococcus pneumoniae as the second most frequent cause of invasive disease in children younger than 5 years of age. All 43 serotype 5 isolates collected during this period were shown to be susceptible to penicillin, erythromycin, cefotaxime, and vancomycin, but most (38 of 43, or 88%) were highly resistant to chloramphenicol. In order to clarify a possible genetic relatedness among these isolates, additional microbiological and molecular characterizations were performed. Most (40 of 43, or 93%) of the isolates were found to be resistant to tetracycline. Pulsed-field gel electrophoresis (PFGE) patterns of chromosomal DNAs revealed that all the 43 isolates were closely related and that 38 of the 43 isolates were representatives of a "Colombian clone" of S. pneumoniae isolates which were recovered throughout the 3-year surveillance period from patients in 13 hospitals located in five Colombian cities. Isolates belonging to this Colombian clone were resistant to chloramphenicol and tetracycline, hybridized with the cat and tetM DNA probes in the same 340-kb SmaI fragment, and had identical PFGE patterns after both SmaI and ApaI digestions.

Risk factors and course of illness among children with invasive penicillin-resistant Streptococcus pneumoniae. The Streptococcus pneumoniae Working Group

OBJECTIVES

To assess differences in risk factors, clinical presentation, and course of illness between children infected with penicillin-sensitive and drug-resistant Streptococcus pneumoniae (DRSP).

DESIGN

A retrospective cohort study conducted in Uruguay and Argentina using information from a hospital-based surveillance system. Hospitalized children 5 years of age and younger who had S pneumoniae isolated from a normally sterile site between June 1993 and October 1996 were eligible. Hospital records were linked with surveillance data. Both stratified univariate analysis and logistic regression was completed.

RESULTS

Of the 380 children eligible for the study, 274 records (72%) were available for review. Ninety-nine children (36%) had DRSP; 46 showed intermediate susceptibility (minimum inhibitory concentration, 0.12-1.0 microg/mL) and 53 showed high-level resistance (minimum inhibitory concentration >/=2.0 microg/mL). Children with meningitis were less likely to have DRSP than those with other forms of invasive disease (relative risk = 0. 5; 95% confidence interval [CI], 0.2-0.9). Risk factors associated with DRSP were use of penicillin or ampicillin in the 3 months before illness (odds ratio = 2.9; 95% CI, 1.5-5.7) and possession of private medical coverage (odds ratio = 2.4; 95% CI, 1.2-5.0). Response to therapy, including response to penicillin or ampicillin among children with nonmeningeal invasive disease, course of illness, and clinical outcome did not differ significantly between children infected with penicillin-susceptible or penicillin-resistant isolates.

CONCLUSION

In this study, previous use of penicillin or ampicillin and private medical coverage were associated with having DRSP. Children with nonmeningeal invasive disease responded equally well to penicillin regardless of the penicillin susceptibility of their pneumococcal isolate.

Determination of trimethoprim-sulfamethoxazole resistance in Streptococcus pneumoniae by using the E test with Mueller-Hinton agar supplemented with sheep or horse blood may be unreliable. The Pneumococcal Study Group

An international, multicenter study compared trimethoprim-sulfamethoxazole MICs for 743 Streptococcus pneumoniae isolates (107 to 244 isolates per country) by E test, using Mueller-Hinton agar supplemented with 5% defibrinated horse blood or 5% defibrinated sheep blood, with MICs determined by the National Committee for Clinical Laboratory Standards broth microdilution reference method. Agreement within 1 log2 dilution and minor error rates were 69.3 and 15.5%, respectively, on sheep blood-supplemented agar and 76.9 and 13.6%, respectively, with horse blood as the supplement. Significant interlaboratory variability was observed. E test may not be a reliable method for determining the resistance of pneumococci to trimethoprim-sulfamethoxazole.

Microbiology of acute otitis media in Costa Rican children

BACKGROUND

Because of the increasing number of resistant middle ear pathogens reported from different centers worldwide, an active surveillance of the microbiology and susceptibility pattern of middle ear pathogens is required for proper antimicrobial recommendations among different regions of the world.

OBJECTIVE

To study the microbiology and susceptibility pattern of middle ear pathogens obtained from Costa Rican children with acute otitis media.

METHODS

Between 1992 and 1997 a diagnostic tympanocentesis was performed in 398 Costa Rican patients with acute otitis media. Middle ear fluid was obtained for culture and minimal inhibitory concentrations were determined by the E-test technique in those isolates obtained between October, 1995, and January, 1997.

RESULTS

The most common pathogens cultured were Streptococcus pneumoniae (30%), Haemophilus influenzae (14%), Staphylococcus aureus (4%) and Streptococcus pyogenes (4%). Moraxella catarrhalis was uncommon. Beta-lactamase production was low (3.7%) among the H. influenzae isolates but frequent among the Staphylococcus aureus (57.1%) and M. catarrhalis (100%) strains. Overall 9 of 46 S. pneumoniae isolates (19.6%) exhibited decreased susceptibility to penicillin of which 8 isolates (17.4%) showed intermediate and one strain (2.2%) high level resistance. Among the penicillin-susceptible S. pneumoniae isolates, susceptibility to the following antimicrobials was: 81%, azithromycin; 89%, clarithromycin; and 100%, ceftriaxone and trimethoprim-sulfamethoxazole (TMP-SMX). Among the penicillin-resistant S. pneumoniae isolates the percentage of susceptible strains was 89% for azithromycin, clarithromycin and ceftriaxone and 67% for TMP-SMX.

CONCLUSIONS

Based on this microbiologic information the agents considered first line drugs in the treatment of acute otitis media in Costa Rica remain amoxicillin or TMP-SMX.

Epidemiology of emerging/re-emerging antimicrobial-resistant bacterial pathogens

The rapid global expansion of bacteria resistant to antimicrobials is the most important development over the past year in emerging bacterial diseases. The critical events are the emergence of Staphylococcus aureus with decreased sensitivity to vancomycin, worldwide resistance to penicillin in Streptococcus pneumoniae, and the remorseless progression of multiply-resistant Mycobacterium tuberculosis. Most startling was the isolation from a human in Madagascar of a plague bacillus possessing a plasmid readily transferable to Escherichia coli, which confers multiple antibiotic resistance. The hospital environment continues to see the transmission of resistant organisms, notably vancomycin-resistant enterococci. Finally, as food markets become more open around the world, food-borne outbreaks of E. coli O157 and cholera demonstrate how difficult it can be to establish effective health and safety barriers.