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.
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 infecciónen 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.
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 años (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%) que en 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.
Up until now, the capsular polysaccharides of
Staphylococcus aureus
have been classified into 11 types, of which only 2 types 5 and 8; (encoded by the genes
cap5
and
cap8,
respectively) are present ...in 80–90% of clinically significant strains. The aim of the present study was to detect the capsular genotypes of methicillin-resistant
S. aureus
(MRSA) clinical isolates and determined their clonal distribution. A total of 262 MRSA clinical isolates from different hospitals in Mexico were analyzed by PCR to determine the genetic characteristics of their capsule expression. Pulsed-field gel electrophoresis and multilocus sequence typing were used to characterize the isolates. The analysis of the capsular genotypes among MRSA isolates showed that 245 isolates (93.5%) contained the
cap5
gene, and that the remaining 17 (6.5%) encoded the
cap8
gene. The MRSA isolates were grouped into four clonal groups. The identification of the capsular genotypes of clinical isolates of MRSA is important information because potential vaccine formulations against
S. aureus
involve capsular polysaccharides.
Antimicrobial resistance is a global concern. Analysis of sterile fluids is essential because microorganisms are defined as significant in most cases. Blood, cerebrospinal, and pleural fluids are ...frequently received in the microbiology lab because they are associated with considerable rates of morbi-mortality. Knowledge of epidemiology in these samples is needed to choose proper empirical treatments due to the importance of reducing selection pressure.
We used retrospective laboratory data of blood, CSF, and pleural fluid collected from patients in Mexico between 2019 and 2020. Each laboratory identified the strains and tested susceptibility using its routine methods. For
, a comparative analysis was performed with data from the broth microdilution method.
Forty-five centers participated in the study, with 30,746 clinical isolates from blood, 2,429 from pleural fluid, and 2,275 from CSF. For blood and CSF,
was the most frequent. For blood, among gram negatives, the most frequent was
. Among
, 9.8% of
were carbapenem-resistant
For
, similar resistance percentages were observed for levofloxacin, cefotaxime, and vancomycin. For CSF, the most frequent gram-negative was
In
, carbapenem resistance was 71.4%. The most frequent species detected for pleural fluid was
; in
, carbapenem resistance was 96.3%.
Gram-negative bacteria, with
most prevalent, are frequently recovered from CSF, blood, and pleural fluid. In
, the routine, conventional methods showed good agreement in detecting resistance percentages for erythromycin, levofloxacin, and vancomycin.
Background and Aims Streptococcus pneumoniae constitutes one of the main causes of sepsis, bacteremia and meningitis (pneumococcal invasive disease – PID), and pneumonia in infants and small ...children. Antipneumococcal vaccination in Mexico is expected to be a useful strategy to reduce morbimortality due to this cause. We undertook this study to determine the prevalence of PID and pneumonia and the PCV vaccination status of affected children as well as serotype distribution and antimicrobial susceptibility of pneumococcal strains responsible for PID in infants and small children in Mexico. Methods From March 2010–June 2011, a prospective multicenter study was carried out in four states in Mexico to determine the prevalence of bacteremia, meningitis, septic arthritis and pneumonia due to S. pneumoniae and other microorganisms in children from 28 days–59 months of age. Isolated pneumococcal strains were serotyped and their antimicrobial resistance determined. Results During the study period, 545 children were diagnosed with bacteremia, meningitis, septic arthritis or pneumonia; 46.7% of these clinical entities occurred among children <12 months of age. Community-acquired pneumonia was the most prevalent disease. It was possible to identify a causal microorganism in 55 cases, from which 80% were S. pneumoniae. Fifteen percent of patients with PID died. The most prevalent pneumococcal serotypes were 19A, 35B, 19F and 6A. 10.2% of nonmeningeal strains were resistant to meropenem and 82% were resistant to TMP/SMX. Conclusions This study shows that pneumococcus was the most common bacteria isolated in the studied population, although epidemiological and laboratory-based surveillance still needs improvement.
As part of the Sistema Regional de Vacunas (SIREVA) initiative, we conducted a surveillance study to determine the relative prevalence of capsular types of Streptococcus pneumoniae and antimicrobial ...susceptibility of invasive isolates in children less than 5 years old. We collected 220 isolates and found 33 of the 90 known types, with type 23F as the most common followed by types 6A+B, 14, 19F, and 19A. High penicillin resistance was found in 49 strains (22.2%), 31 belonging to type 23F. Twenty-nine (13.1%) were resistant to erythromycin, 95 (43.1%) were resistant to chloramphenicol, and 24 (10.9%) were resistant to cefotaxime. No strains were resistant to vancomycin.
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.
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 log₂ 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.
PDF
