Diagnosis of bacterial meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae using a multiplex real-time PCR technique.

Bacterial meningitis is one of the diseases that, despite the introduction of several vaccines, remains a serious public health concern. Streptococcus pneumoniae (Spn), Neisseria meningitidis (Nm), and Haemophilus influenzae (Hi) are responsible for most cases diagnosed in children, adolescents, and adult population. Rapid, sensitive, and specific laboratory assays are critical for effective diagnosis and treatment, particularly in countries like Mexico in which culture positivity rates are very low due to the use of antibiotics prior to sample collection and to delay in transporting samples to the laboratory. The aim of this study was to evaluate the use of real-time polymerase chain reaction (RT-PCR) of cerebrospinal fluid (CSF) as a rapid diagnostic test for bacterial meningitis and compare these results with bacterial culture in three general hospitals in Mexico. During a 5-year period (2014-2018), a total of 512 CSF samples obtained from patients in whom infectious meningitis was suspected as initial clinical diagnosis were tested with RT-PCR with species-specific targets for the three pathogens. For Spn, 5.07% samples were RT-PCR positive; 0.39% for Nm and none for Hi. Only five RT-PCR Spn positive samples had a positive culture. Sensitivity and specificity estimates for RT-PCR are 100% and 95.46%, respectively. DNA amplification methods can provide better sensitive diagnostic tests than the reference standard, which is culture, particularly when antimicrobial treatment is initiated before clinical samples can be obtained.

The Evolution of Antimicrobial Resistance in Mexico During the Last Decade: Results from the INVIFAR Group.

Background: Surveillance of antimicrobial resistance (AMR) requires an international approach with national and local strategies. Our aim was to summarize a retrospective 10-year report of antibiotic resistance of gram-positive and gram-negative bacteria in Mexico. Methods: A total of 46 centers from 22 states of Mexico participated. Databases of AMR from January 2009 to December 2018 were included for most species. The 10-year period was divided into five 2-year periods. Results: For Staphylococcus aureus, a decrease in resistance in all specimens was observed for erythromycin and oxacillin (p < 0.0001 for each). For Enterobacter spp., resistance to meropenem increased for urine specimens (p = 0.0042). For Klebsiella spp., increased drug resistance in specimens collected from blood was observed for trimethoprim/sulfamethoxazole, gentamicin, tobramycin (p < 0.0001 for each), meropenem (p = 0.0014), and aztreonam (p = 0.0030). For Acinetobacter baumannii complex, high drug resistance was detected for almost all antibiotics, including carbapenems, except for tobramycin, which showed decreased resistance for urine, respiratory, and blood isolates (p < 0.0001 for each), and for amikacin, which showed a decrease in resistance in urine specimens (p = 0.0002). An increase in resistance to cefepime was found for urine, respiratory, and blood specimens (p < 0.0001 for each). For Pseudomonas aeruginosa, aztreonam resistance increased for isolates recovered from blood (p = 0.0001). Conclusion: This laboratory-based surveillance of antibiotic resistance shows that resistance is increasing for some antibiotics in different bacterial species in Mexico and highlights the need for continuous monitoring of antibiotic resistance.

Clinical and microbiological characteristics of community-acquired pneumonia associated with Streptococcus pneumoniae in adult patients in Mexico / Características clínicas y microbiológicas de la neumonía adquirida en la comunidad asociada con Streptococcus pneumoniae en pacientes adultos en México

The aim of this study was to assess the risk factors and clinical and microbiological characteristics of community-acquired pneumonia (CAP) in adult patients in Mexico. Streptococcus pneumoniae classified as the causative agent of CAP in adult patients and patients with invasive S. pneumoniae isolates presented to three tertiary teaching hospitals during the 15-year study period were selected. Serotyping and susceptibility testing were performed for all included isolates. Clinical and demographic data were recorded. A total of 96 patients infected with S. pneumoniae (71 with CAP, 25 with invasive disease) were included. The CAP group involved more males (74.6%) than the invasive disease group (p = 0.03). Head trauma was more common in the CAP group (21.1%) than in the invasive disease group (4.0%; p = 0.03). The most prevalent serotype was 19A, followed by serotypes 3 and 23F. After the introduction of the heptavalent conjugated pneumococcal vaccine (PCV7), the prevalence of included serotypes declined significantly; no such change was found after the introduction of the PCV13 vaccine, including in the prevalence of serotype 19A. Susceptibility to all antimicrobials tested except vancomycin declined over the study period. In conclusion, head trauma was the most common comorbidity in the CAP group. The most prevalent serotype was 19A. Decreased susceptibility to most antimicrobials tested was observed.

El objetivo de este estudio fue evaluar los factores de riesgo y las características clínicas y microbiológicas de la neumonía adquirida en la comunidad (NAC) en pacientes adultos en México. Se seleccionaron pacientes adultos con NAC con Streptococcus pneumoniae como agente causal y pacientes con aislamientos invasivos de S. pneumoniae que concurrieron a tres hospitales de enseñanza de tercer nivel durante el período de estudio de 15 anos (2000-2015). Se realizaron pruebas de serotipificación y sensibilidad con todos los aislados incluidos. Se colectaron los datos clínicos y demográficos. Se incluyeron en total 96 pacientes infectados con S. pneumoniae (71 con NAC y 25 con enfermedad invasiva). El grupo con NAC incluía más varones (74,6%) que el grupo de enfermedad invasiva (p = 0,03). El traumatismo craneoencefálico fue más frecuente en el grupo NAC (21,1%) queen el grupo con enfermedad invasiva (4,0%; p = 0,03). El serotipo más frecuente fue 19A, seguido de los serotipos 3 y 23F. Después de la introducción de la vacuna antineumocócica conjugada heptavalente (PCV7), la prevalencia de los serotipos incluidos en aquella disminuyó significativamente; no sucedió lo mismo después de la introducción de la PCV13, incluso en relación con la prevalencia del serotipo 19A. La sensibilidad a todos los antimicrobianos evaluados, excepto la vancomicina, disminuyó durante el período de estudio. En conclusión, el traumatismo craneoencefálico fue la comorbilidad más frecuente en el grupo con NAC. El serotipo más frecuente fue el 19A, y se observó disminución de la sensibilidad a la mayoría de los antimicrobianos probados a lo largo del período considerado.

Clinical and microbiological characteristics of community-acquired pneumonia associated with Streptococcus pneumoniae in adult patients in Mexico.

The aim of this study was to assess the risk factors and clinical and microbiological characteristics of community-acquired pneumonia (CAP) in adult patients in Mexico. Streptococcus pneumoniae classified as the causative agent of CAP in adult patients and patients with invasive S. pneumoniae isolates presented to three tertiary teaching hospitals during the 15-year study period were selected. Serotyping and susceptibility testing were performed for all included isolates. Clinical and demographic data were recorded. A total of 96 patients infected with S. pneumoniae (71 with CAP, 25 with invasive disease) were included. The CAP group involved more males (74.6%) than the invasive disease group (p=0.03). Head trauma was more common in the CAP group (21.1%) than in the invasive disease group (4.0%; p=0.03). The most prevalent serotype was 19A, followed by serotypes 3 and 23F. After the introduction of the heptavalent conjugated pneumococcal vaccine (PCV7), the prevalence of included serotypes declined significantly; no such change was found after the introduction of the PCV13 vaccine, including in the prevalence of serotype 19A. Susceptibility to all antimicrobials tested except vancomycin declined over the study period. In conclusion, head trauma was the most common comorbidity in the CAP group. The most prevalent serotype was 19A. Decreased susceptibility to most antimicrobials tested was observed.

Streptococcus pneumoniae Serotype 3 in Mexico (1994 to 2017): Decrease of the Unusual Clonal Complex 4909 Lineage following PCV13 Introduction.

Streptococcus pneumoniae expressing serotype 3 has a high virulence and a high case fatality ratio. Most studies of serotype 3 pneumococci have focused on a single lineage, the widespread sequence type 180 (ST180). To evaluate the serotype 3 lineages causing infections in Mexico, we characterized 196 isolates recovered from 1994 to 2017. The isolates were mostly susceptible to all antimicrobials tested. A single meningitis isolate was resistant to penicillin, and the resistance to erythromycin was 5.2%. The isolates represented the widely disseminated clonal complex 180 (CC180; n = 140), the unusual CC4909 (n = 42), CC260 (n = 11), and a few singletons (n = 3). CC260 was less frequent among pneumococcal invasive disease isolates than CC180 and CC4909 (P = 0.015). There was a decrease of CC4909 (P < 0.001) following PCV13 introduction (2012 to 2017). The CC4909 isolates were represented mostly by ST1119 (n = 40), seemingly having a restricted geographic origin, with isolates in the PubMLST database having been recovered only in Mexico, the United States, and Germany. A genomic analysis of publicly available genomes showed that ST1119 isolates have less than 32% similarity with ST180 isolates, indicating that these lineages are more separated than revealed by traditional multilocus sequence typing. Considering the suggestions of a lower efficacy of the 13-valent pneumococcal conjugate vaccine against serotype 3, the different dynamics of the two major serotype 3 lineages in Mexico following the introduction of PCV13 should be closely monitored.

Streptococcus pneumoniae: distribution of serotypes and antimicrobial susceptibility in patients with cancer.

OBJECTIVE: To describe the distribution of pneumococcal serotypes causing infectious diseases in patients with hematological malignancies and solid tumors and their antimicrobial susceptibility before and after introduction of pneumococcal conjugate vaccine (PCV7) in Mexico. MATERIALS AND METHODS: Consecutive pneumococcal isolates from hospitalized patients from the SIREVA-network were serotyped using the Quellung reaction and antimicrobial susceptibility was performed using the broth microdilution method. RESULTS: A total of 175 pneumococcal isolates were recovered, 105 from patients with hematological malignancies and 70 with solid tumors. Serotypes 19A (22.7%), 19F (20.4%), and 35B (17.7%) were the most frequent isolates in the first group and serotypes 3 (27.2%) and 19A (28.6%) in the second group. No decreased susceptibility to beta-lactams or TMP/SMX was observed after introduction of PCV7. CONCLUSIONS: An increase in non-vaccine types is observed without significate changes in antimicrobial susceptibility after introduction of PCV7.

Streptococcus pneumoniae: distribution of serotypes and antimicrobial susceptibility in patients with cáncer / Streptococcus pneumoniae: distribución de serotipos y susceptibilidad antimicrobiana en pacientes con cancer

Abstract: Objective: To describe the distribution of pneumococcal serotypes causing infectious diseases in patients with hematological malignancies and solid tumors and their antimicrobial susceptibility before and after introduction of pneumococcal conjugate vaccine (PCV7) in Mexico. Materials and methods: Consecutive pneumococcal isolates from hospitalized patients from the SIREVA-network were serotyped using the Quellung reaction and antimicrobial susceptibility was performed using the broth microdilution method. Results: A total of 175 pneumococcal isolates were recovered, 105 from patients with hematological malignancies and 70 with solid tumors. Serotypes 19A (22.7%), 19F (20.4%), and 35B (17.7%) were the most frequent isolates in the first group and serotypes 3 (27.2%) and 19A (28.6%) in the second group. No decreased susceptibility to beta-lactams or TMP/SMX was observed after introduction of PCV7. Conclusions: An increase in non-vaccine types is observed without significate changes in antimicrobial susceptibility after introduction of PCV7.

Resumen: Objetivo: Describir la distribución de serotipos neumocócicos en pacientes con neoplasias hematológicas y tumores sólidos, así como la susceptibilidad antimicrobiana antes y después de la introducción de la vacuna conjugada contra neumococo (PCV7) en México. Material y métodos: Se tipificaron, mediante la reacción de Quellung, los aislamientos consecutivos en hospitales de la Red SIREVA-México. Se determinó la susceptibilidad antimicrobiana mediante microdilución en placa. Resultados: Se recuperaron 175 aislamientos, de los cuales 105 provenían de pacientes con neoplasias hematológicas y 70 con tumores sólidos. Los serotipos 19A (22.7%), 19F (20.4%) y 35B (17.7%) fueron los más frecuentes en el primer grupo y los serotipos 3 (27.2%) y 19A (28.6%) en el segundo. No se observó disminución de la resistencia a betalactámicos o TMP/SMX después de la introducción de PCV7. Conclusiones: Se observa un incremento de serotipos no vacunales, sin cambios significativos en la susceptibilidad antimicrobiana antes y después de la introducción de PCV7.

Changing trends in serotypes of S. pneumoniae isolates causing invasive and non-invasive diseases in unvaccinated population in Mexico (2000-2014).

OBJECTIVE: Introduction of pneumococcal conjugate vaccines (PCV) targeted against a limited number of serotypes substantially decreased invasive (IPD) and non-invasive pneumococcal diseases (NIPD) but it was accompanied by non-vaccine type replacement disease. After 9 years of introduction of PCV in Mexico, we analyze the evidence of the indirect effects on IPD and NIPD serotype distribution among groups not targeted to receive the vaccine. METHODS: From January 2000 to December 2014, pneumococcal strains isolated from IPD and NIPD cases from patients ≥5 years of age from participant hospitals of the SIREVA II (Sistema Regional de Vacunas) network were serotyped. A regression analysis was performed considering year and proportion of serotypes included in the different vaccine formulations (PCV7, PCV10 and PCV13). The slope was obtained for each regression line and their correspondent p-value. The proportion of each serotype in the pre-PCV7 and post-PCV7 periods was evaluated by χ2 test. RESULTS: From a total of 1147 pneumococcal strains recovered, 570 corresponded to the pre-PCV7 and 577 to the post-PCV7 periods. The proportion of vaccine serotypes included in the three PCV formulations decreased by 2.4, 2.6 and 1.3%, respectively per year during the study period. A significant increase of serotype 19A was observed in the post-vaccine period in all age groups. CONCLUSIONS: A percentage of annual decline of serotypes causing IPD and NIPD included in PCV was detected among groups not targeted to receive the vaccine, probably due to herd effect. Considering pneumococcal serotype distribution is a dynamic process, we highlight the importance of surveillance programs.

Invasive and Complicated Pneumococcal Infection in Patients with Cancer.

BACKGROUND: In susceptible patients, Streptococcus pneumoniae can cause complicated pneumonia and invasive pneumococcal disease. The aim of this study was to assess the clinical and antimicrobial features of complicated and invasive pneumococcal disease in patients with cancer. METHODS: We conducted a retrospective study including all S. pneumoniae isolates between January 1, 2007 and December 31, 2015 in an oncology center. Capsular serotyping was done in isolates from sterile sites. RESULTS: There were 103 episodes: 69 with invasive pneumococcal disease and 34 with complicated pneumonia. Sixty-two patients were male (60%); mean age was 50 years. Eighty-four isolates were susceptible to penicillin (81.6%), 11 (10%) were intermediate, and eight (8.3%) were resistant. Serotyping was performed in 64 isolates; the main serotypes identified were 3 (n = 13) and 19A (n = 11). No patient had a record of vaccination. Mortality at seven days attributed to pneumococcal infection was different in invasive pneumococcal disease (n = 18, 28.6%) vs. pneumonia (n = 3, 8.9%; p = 0.04). Thirty-day mortality related with the infectious process was statistically different between both groups: 21 patients with invasive pneumococcal disease (30.4%) and six with pneumonia (17.6%; p = 0.04). By logistic analysis, the risk factor associated with mortality was not having received appropriate antimicrobial treatment in the first 48 hours. CONCLUSIONS: S. pneumoniae is a pathogen related with high mortality in patients with cancer. Pneumococcal immunization needs to be reinforced in this population.

Non-typeable Haemophilus influenzae biofilm production and severity in lower respiratory tract infections in a tertiary hospital in Mexico.

Non-typeable Haemophilus influenzae (NTHi) is a common opportunistic bacterial pathogen that primarily infects the respiratory mucosa. This study was conducted to assess clinical and microbiological data related to disease severity in patients with lower respiratory tract infections caused by NTHi in a tertiary care hospital in Mexico. NTHi isolates were subjected to serotyping, antimicrobial susceptibility evaluationand analyses of ß-lactamase production, genetic relatednessand biofilm formation. Clinical and demographic data were retrieved from patients' records. The mean age of the patients was 40.3 years; the majority (n=44, 72.1 %) were male. The main comorbidities were arterial hypertension (n=22, 36.1 %) and diabetes mellitus (n=17, 27.9 %). NTHi isolates (n=98) were recovered from tracheal aspirate (n=57, 58.2 %), sputum (n=26, 26.5 %)and bronchial aspirate (n=15, 15.3 %) specimens. Low resistance to cefotaxime (n=0, 0.0 %), rifampin (n=1, 1.1 %) and chloramphenicol (n=3, 3.2 %) and greater resistance to ampicillin (n=30, 32.3 %) and trimethoprim-sulfamethoxazole (n=49, 52.7 %) were detected. ß-Lactamase production was found in 17 (17.3 %) isolates. Isolates displayed high genetic diversity, and only 10 (10.2 %) were found to be biofilm producers. The antimicrobial susceptibility patterns of biofilm-producing and non-producing isolates did not differ. Biofilm production was associated with prolonged hospital stay (P=0.05). Lower respiratory NTHi isolates from Mexico showed low antimicrobial resistance and weak biofilm production. Younger age was correlated with lower Acute Physiology and Chronic Health Evaluation II score (moderate, P=0.07; severe, P=0.03).

Streptococcus pneumoniae as cause of infection in infants less than 60 days of age: serotypes and antimicrobial susceptibility.

OBJECTIVE: The aim of this study was to determine the distribution of serotypes and the antimicrobial susceptibilities of Streptococcus pneumoniae clinical isolates causing invasive and non-invasive disease in children aged ≤60 days in hospitals in Mexico. METHODS: A 15-year retrospective study was conducted for the period 2000 to 2014. Pneumococcal clinical isolates were serotyped by Quellung reaction, and antimicrobial susceptibility testing was performed with the broth microdilution method. RESULTS: A total of 126 pneumococcal isolates were collected. Pneumonia was the most frequent diagnosis (40.5%), followed by meningitis (29.4%), septicemia (16.7%), and other clinical entities, including otitis media and conjunctivitis (13.5%). The most frequent serotypes before the introduction of heptavalent pneumococcal conjugate vaccine (PCV7) were 19F, 23F, 7F, and 35B. Serotypes 3, 6A, 10A, 12F, and 15A/B increased after the introduction of PCV7. Serotype 19A was isolated most frequently in the pneumonia and meningitis cases only after the introduction of PCV7, and it displayed a high resistance to penicillin. CONCLUSIONS: Although the number of infections in infants aged ≤60 days was low, such infections were not unusual events. New vaccination strategies should be evaluated to limit the risks in this age group.

Streptococcus pneumoniae Serotypes Identified in Mexican Children with Invasive Disease Before and After the Introduction of PCV7 (1993-2012).

BACKGROUND AND AIMS: Streptococcus pneumoniae is the leading cause of acute otitis media, pneumonia, meningitis, and sepsis. The heptavalent pneumococcal conjugate vaccine (PCV7) was incorporated into the national immunization program in Mexico in 2008. The aim of the study was to analyze the frequency of S. pneumoniae serotypes isolated from children ≤5 years of age with invasive diseases before and after the introduction of PCV7. METHODS: Isolates from sterile fluids, tissues and other body fluids were obtained from 1993 to 2012. Isolates collected in hospitals for the surveillance network were sent to the Instituto Nacional de Salud Publica. Serotyping was done using the Quellung reaction. The pre-vaccination period was considered from 1993-2007. RESULTS: A total of 1346 isolates were collected during 1993-2012. In the pre-vaccination era, serotypes included in PCV7 accounted for 59.7% of the strains, whereas in 2012 they represented only 21% of cases. There was a significant decrease in all PCV7-included serotypes. A gradual increase of the 19A serotype was detected during the vaccination period from 7% in 2008 to 39% of the isolates in 2012. In this year, 29% of the serotypes causing invasive disease were not included in any of the pneumococcal conjugate vaccines. CONCLUSION: The emergence of PCV7 non-included serotypes after vaccination demands increased surveillance. Currently in Mexico, the 13-valent conjugate vaccine (PCV13) offers better coverage than the 10-valent pneumococcal conjugate vaccine (PCV10).

[Prevalence of Streptococcus pneumoniae serotype 19A before and after the introduction of the heptavalent conjugate vaccine in Mexico]. / Prevalencia de Streptococcus pneumoniae serotipo 19A antes y después de la introducción de la vacuna conjugada heptavalente en México.

OBJECTIVE: To determine the prevalence of S. pneumoniae serotype 19A (Spn19A), before and after the introduction of heptavalent pneumococcal conjugate vaccine (PCV7) in Mexico. MATERIALS AND METHODS: Descriptive study carried out in Mexico with surveillance information of pneumococcal disease, generated from the Sireva network. We performed lineal regression analysis with the proportion of Spn19A by year in two study periods. Data were analyzed using SPSS v.18 software. RESULTS: A total of 1825 S. pneumoniae strains causing infection in pediatric population were recovered in the period 2000-2012, 225/12.3% were Spn19A, and of these, 75/6.3% were isolated in 2000-2008 and 150/23.6% in 2009-2012. There was an increase in antimicrobial resistance post-vaccination for all drugs except vancomycin. CONCLUSION: It was observed that the frequency of this serotype and antimicrobial resistance increased after the introduction of PCV7.

Prevalencia de Streptococcus pneumoniae serotipo 19A antes y después de la introducción de la vacuna conjugada heptavalente en México / Prevalence of Streptococcus pneumoniae serotype 19A before and after the introduction of the heptavalent conjugate vaccine in Mexico

Objetivo. Conocer la prevalencia de S. pneumoniae serotipo 19A (Spn19A) antes y después de la introducción de la vacuna conjugada heptavalente (PCV7) en México. Material y métodos. Estudio descriptivo realizado con la información sobre vigilancia de enfermedades causadas por neumococos, generada por la red Sireva. Se realizó un análisis de regresión lineal con la proporción de cepas de Spn19A por año, en dos periodos. Los datos se analizaron con el paquete estadístico SPSS v.18. Resultados. Durante el periodo 2000-2012 se recuperaron 1 825 cepas de S. pneumoniae causantes de infección en población pediátrica, de las cuales 225/12.3% fueron Spn19A, y de éstos, 75/6.3% se aislaron en el periodo 2000-2008 y 150/23.6% en el periodo 2009-2012. La resistencia antimicrobiana post-vacunal aumentó para todos los fármacos, excepto a vancomicina. Conclusión. Se observó que la frecuencia de este serotipo y la resistencia a antimicrobianos aumentó posterior a la introducción de la PCV7.

Objective. To determine the prevalence of S. pneumoniae serotype 19A (Spn19A), before and after the introduction of heptavalent pneumococcal conjugate vaccine (PCV7) in Mexico. Materials and methods. Descriptive study carried out in Mexico with surveillance information of pneumococcal disease, generated from the Sireva network. We performed lineal regression analysis with the proportion of Spn19A by year in two study periods. Data were analyzed using SPSS v.18 software. Results. A total of 1825 S. pneumoniae strains causing infection in pediatric population were recovered in the period 2000-2012, 225/12.3% were Spn19A, and of these, 75/6.3% were isolated in 2000-2008 and 150/23.6% in 2009-2012. There was an increase in antimicrobial resistance post-vaccination for all drugs except vancomycin. Conclusion. It was observed that the frequency of this serotype and antimicrobial resistance increased after the introduction of PCV7.

Serotypes and antibiotic susceptibility of Streptococcus pneumoniae isolates causative of invasive diseases in Mexican children.

INTRODUCTION: Streptococcus pneumoniae is a worldwide leading cause of morbidity and mortality, while susceptibility towards penicillin and macrolides can be less than 50% in many regions. METHODOLOGY: A total of 150 isolates of S. pneumoniae causative of invasive diseases in children were characterized, of which 24.6% had a fatal outcome. RESULTS: The most prevalent serotypes were 19F, 6B, 23F and 14. Resistance to penicillin, erythromycin (mostly of macrolide-lincosamide-streptogramin resistance phenotype) or trimethoprim-sulfamethoxazole was found in more than 40% of the isolates, but no resistance phenotype appeared linked to lethality. Serotype 3 isolates, which were seldom resistant, had a twofold lethality rate compared to the total sample. CONCLUSION: Serotyping could provide a better outcome-predicting tool than susceptibility testing. The seven-valent vaccine does not include the most prevalent serotypes found in Mexico.

Evolution of an international external quality assurance model to support laboratory investigation of Streptococcus pneumoniae, developed for the SIREVA project in Latin America, from 1993 to 2005.

In 1993 the Pan American Health Organization initiated a laboratory-based surveillance system, called the SIREVA project, to learn about Streptococcus pneumoniae invasive disease in Latin American children. In 1994, National Laboratories in six countries were trained to perform serotyping and antibiotic susceptibility testing using broth microdilution to determine the MIC for specified antibiotics. An international External Quality Assurance (EQA) program was developed to monitor and support ongoing laboratory performance. The EQA program was coordinated by the National Centre for Streptococcus (NCS), Edmonton, Canada, and included external proficiency testing (EPT) and a validation process requiring regular submission of a sample of isolates from each laboratory to the NCS for verification of the serotype and MIC. In 1999, the EQA program was decentralized to use three of the original laboratories as regional quality control centers to address operational concerns and to accommodate the growth of the laboratory network to more than 20 countries including the Caribbean region. The overall EPT serotyping accuracies for phase I (1993 to 1998) and phase II (1999 to 2005) were 88.0 and 93.8%, respectively; the MIC correlations within +/-1 log(2) dilution of the expected result were 83.0 and 91.0% and the interpretive category agreements were 89.1 and 95.3%. Overall, the validation process serotyping accuracies for phases I and II were 81.9 and 88.1%, respectively, 80.4 and 90.5% for MIC agreement, and 85.8 and 94.3% for category agreement. These results indicate a high level of testing accuracy in participating National Laboratories and a sustained increase in EQA participation in Latin America and the Caribbean.

[Prevalence of Streptococcus pneumoniae serotypes on nasopharyngeal colonization in children of Mexico City]. / Serotipos prevalentes de Streptococcus pneumoniae colonizadores de nasofaringe, en niños del Distrito Federal.

OBJECTIVE: To determine the frequency, serotypes and susceptibility profiles to eight antimicrobials in Streptococcus pneumoniae nasopharyngeal isolates from a representative sample of children under 5 years of age, residents of Mexico City. PATIENTS AND METHODS: A cross-sectional survey was conducted in 573 children aged 2 months to 5 years.A nasopharyngeal sample was taken. S. pneumoniae identification, capsular serotyping and antimicrobial susceptibility to eight antimicrobials were performed according to standardized methods. RESULTS: S. pneumoniae was isolated in 122/573 (21.4%) children. The most frequent capsular serotypes were 23F, 35, 19F, 11A and 15A; 46% of isolates corresponded to serotypes not included in the heptavalent vaccine. Low penicillin susceptibility was found in 12% of strains with 3% of highly resistant penicillin strains; erythromycin resistance was >30% and trimethoprim-sulfamethoxazole resistance >40%. None of the isolates was resistant to vancomycin, cefotaxime, amoxacillin-clavulanate, chloramphenicol or ampicillin. CONCLUSIONS: Several S. pneumoniae serotypes from nasopharyngeal carriers are not included in the heptavalent vaccine. Resistance to trimethoprim-sulfamethoxazole and macrolides is high. The medical community should be aware of these results.

Serotipos prevalentes de Streptococcus pneumoniae colonizadores de nasofaringe, en niños del Distrito Federal / Prevalence of Streptococcus pneumoniae serotypes on nasopharyngeal colonization in children of Mexico City

OBJETIVO: Determinar frecuencia, serotipos y susceptibilidad a ocho antimicrobianos en Streptococcus pneumoniae aislados de la nasofaringe de una muestra representativa de niños menores de cinco años de edad residentes en el Distrito Federal. MATERIAL Y MÉTODOS: Estudio transversal, hecho de febrero de 2002 a enero de 2003. Se incluyeron niños de 2 meses a 5 años. A los seleccionados se les tomó una muestra de exudado faríngeo con hisopo de alginato de calcio. Bajo técnicas ya establecidas se realizó identificación, tipificación y susceptibilidad a ocho antimicrobianos de los aislamientos de S. pneumoniae. Se utilizó estadística descriptiva, prueba de Ji cuadrada y razón de momios (IC 95 por ciento) para los factores de riesgo. RESULTADOS: Se estudiaron 573 niños. En 122/573 (21.4 por ciento) niños se aisló S. pneumoniae. Los serotipos más frecuentes fueron el 23F, 35, 19F, 11A y 15A; 46 por ciento de los serotipos encontrados no son cubiertos con la vacuna heptavalente. Se encontró 12 por ciento de susceptibilidad reducida a la penicilina, con 3 por ciento de cepas con alta resistencia; la resistencia a eritromicina fue >30 por ciento y para trimetoprim-sulfametoxazol (TMP/SMX) >40 por ciento. No hubo cepas resistentes a vancomicina, cefotaxima, amoxicilina-clavulanato, cloranfenicol o ampicilina. CONCLUSIONES: El porcentaje de serotipos de S. pneumoniae en portadores nasofaríngeos no cubiertos por la vacuna heptavalente es alto, y la resistencia a macrólidos y TMP/SMX es elevada, lo que debe alertar al grupo médico.