Horacio Lopardo

Six-Month Multicenter Study on Invasive Infections Due to Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis in Argentina

ABSTRACT During a 6-month period, 95 invasive infections due to Streptococcus pyogenes and group C or group G Streptococcus dysgalactiae subsp. equisimilis were recorded from 40 centers of 16 cities in Argentina. We describe here epidemiologic data available for 55 and 19 patients, respectively, associated with invasive infections due to S. pyogenes and S. dysgalactiae subsp. equisimilis. The associated isolates and 58 additional pharyngeal isolates were genotyped and subjected to serologic and/or antibiotic susceptibility testing. Group A streptococcal emm type distribution and strain association with toxic shock appeared to differ somewhat from results found within the United States; however, serologic characterization and sof sequence typing suggested that emm types found in both countries are reflective of shared clonal types.

Macrolide resistance in Streptococcus pneumoniae isolated from Argentinian pediatric patients suffering from acute otitis media

Macrolide-resistant Streptococcus pneumoniae emerged in Argentina in 1995, representing 26% of invasive infection isolates in children under 5 years old. The objectives of this study were to describe the prevalence of ermB and mefA genes in macrolide-resistant S. pneumoniae isolates from acute otitis media (AOM) and to determine their genetic relatedness. Between May 2009 and August 2010, 126 S. pneumoniae isolates from 324 otherwise healthy children with a first episode of AOM were included. Twenty six of these isolates (20.6%) were resistant to erythromycin. Most frequent serotypes were: 14 (46.2%), 6A (23.1%), 19F (7.7%) and 9V (7.7%). Twenty (76.9%) carried the mefA gene, 5 (19.2%) have the ermB gene, and 1 (3.9%) both ermB + mefA. Ten clonal types were identified, mostly related to Sweden(15A)-25/ST782 (SLV63), CloneB(6A)/ST473 and England(14)-9/ ST9. This is the first study assessing the mechanisms of macrolide resistance in pneumococci isolates from pediatric AOM in Argentina and their genetic relatedness.

Capacidad de los laboratorios nacionales de referencia en Latinoamérica para detectar mecanismos de resistencia emergentes

OBJETIVO: Evaluar la capacidad de 17 laboratorios nacionales de referencia que participan en el Programa Latinoamericano de Control de Calidad en Bacteriologia y Resistencia a los Antimicrobianos (LA-EQAS) para detectar mecanismos de resistencia emergentes, a saber: resistencia de enterobacterias a carbapenemes por presencia de Klebsiella pneumoniae carbapenemasa (KPC); resistencia de enterobacterias a carbapenemes por presencia de metalobetalactamasas (MBL) tipo IMP, y resistencia intermedia a vancomicina de aislamientos de Staphylococcus aureus (VISA). METODOS: Se enviaron los siguientes tres aislamientos a los 17 laboratorios participantes del LA-EQAS: Klebsiella pneumoniae OPS-161 productor de KPC, Enterobacter cloacae OPS-166 productor de IMP y S. aureus OPS-165 con resistencia intermedia a vancomicina. Se evaluo la interpretacion de las pruebas de sensibilidad y deteccion del mecanismo de resistencia y el tamano de los halos de inhibicion (metodo de difusion por discos) o valor de la concentracion inhibitoria minima (CIM). RESULTADOS: La concordancia en la deteccion de los mecanismos de resistencia fue de 76,4%, 73,3% y 66,7% con respecto a la cepas K. pneumoniae OPS-161, E. cloacae OPS-166 y S. aureus OPS-165, respectivamente. La concordancia entre las zonas de inhibicion obtenidas por los laboratorios participantes y los rangos establecidos por el laboratorio coordinador fue aceptable en los tres aislamientos, ya que alcanzo 90,8%, 92,8% y 88,9%, respectivamente, para cada cepa. CONCLUSIONES: La concordancia global en la deteccion de los mecanismos de resistencia KPC, MBL y VISA fue de 72,1%. Consideramos que los laboratorios nacionales de referencia de America Latina son capaces de reconocer estos mecanismos de resistencia emergentes y se espera que en el futuro la concordancia alcance su nivel maximo.

Acute otitis media in infants younger than three months not vaccinated against Streptococcus pneumoniae

UNLABELLED The true incidence of acute otitis media (AOM) in neonates and infants younger than three months is unknown. In this population organisms causing AOM may disseminate leading to bacteremia, sepsis, and meningitis [1]. OBJECTIVES To describe the clinical presentation, associated severe infections, bacteriologic etiology, and antibiotic resistance patterns of organisms isolated from the middle ear of infants younger than three months that were not vaccinated against Streptococcus pneumoniae. METHODS Otomicroscopy was performed in all children to confirm the suspected diagnosis of AOM. When purulent effusion retained in the middle ear was diagnosed, tympanocentesis and culture of middle-ear fluid was performed by conventional methods. Serotyping was done using the Quellung technique. RESULTS From May 2, 2009 to February 28, 2010, 52 infants met the inclusion criteria. Thirty-six were male (69.2%) and 16 were female (30.8%). From these 52 patients, 76 samples were obtained for culture. Bilateral acute suppurative otitis media was diagnosed in 24 (46.2%) infants. Of all infants, 18 (34.6%) had been treated with antibiotics before tympanocentesis. Eight patients (44.4%) had negative middle-ear fluid cultures. Sixty bacterial pathogens were isolated from the middle-ear fluid of 43 patients. Mixed infections were recorded in 14/52 patients (26.9%). Nine cultures were negative (17.3%), of which eight were from patients that had previously been treated with antibiotics. S. pneumoniae was isolated from middle-ear aspirates of 26/52 (50%) patients with acute suppurative otitis media. Twenty-two out of the 26 isolates were susceptible (84.7%) and four were intermediately susceptible to penicillin (15.3%). Streptococcus pyogenes was isolated in 3/52 (5.8%) and Haemophilus influenzae in 18/52 patients (34.6%). Five (27.8%) of these were beta-lactamase producers. Blood cultures, cerebrospinal fluid, and urine cultures were negative. Parenteral antimicrobial treatment was indicated in 29/52 (56%). CONCLUSIONS S. pneumoniae is the most frequent pathogen to cause AOM in this age group. Empirical treatment with amoxicillin or ceftriaxone should be considered depending on clinical suspicion of severe invasive infection.

Otitis media aguda: prevalencia de otopatógenos en pacientes de un hospital público

BACKGROUND AND OBJECTIVE Acute otitis media (AOM) is one of the most common diseases in childhood and is the most common cause of antibiotic prescriptions in children. The gold standard for identifying the pathogens causing AOM is tympanocentesis. This is only possible in the stage of AOM when exudate is retained in the middle ear. The aim of this study was to describe the prevalence of organisms causing AOM in eutrophic patients at a public paediatric hospital. MATERIAL AND METHODS We included all patients with AOM diagnosed by otomicroscopy with purulent exudate retained in middle ear and suppurative AOM with inadequate drainage consulting at the Otorhinolaryngology Department in a paediatric tertiary care centre from 2 May 2009 to 31 August 2010. RESULTS There were 324 patients included in the study, with 180/324 (55.6%) being male. The median age was 8 months (interquartile range: 4 to 15 months). Bilateral AOM was recorded in 109/324 (33.6%) patients (433 samples for culture were obtained by tympanocentesis in 324 patients). At diagnosis, 37% (120/324) of the children had been receiving antimicrobial treatment. Of the patients who had received antibiotics, 71/120 (59.1%) had bacterial growth in middle ear fluid (MEF) cultures, with 51/71 (71.8%) being susceptible to the antibiotic they received; 20/71 (28.2%) patients were receiving an antibiotic that did not cover the spectrum of organisms isolated. CONCLUSION The pathogens most frequently isolated are Streptococcus pneumoniae (39.5%), Haemophilus influenzae (37.4%), Moraxella catarrhalis (6.1%) and Streptococcus pyogenes (3.0%).

Molecular characterization of invasive Streptococcus dysgalactiae subsp. equisimilis. Multicenter study: Argentina 2011–2012

Streptococcus dysgalactiae subsp. equisimilis (SDSE) has virulence factors similar to those of Streptococcus pyogenes. Therefore, it causes pharyngitis and severe infections indistinguishable from those caused by the classic pathogen. The objectives of this study were: to know the prevalence of SDSE invasive infections in Argentina, to study the genetic diversity, to determine the presence of virulence genes, to study antibiotic susceptibility and to detect antibiotic resistance genes. Conventional methods of identification were used. Antibiotic susceptibility was determined by the disk diffusion and the agar dilution methods and the E-test. Twenty eight centers from 16 Argentinean cities participated in the study. Twenty three isolates (16 group G and 7 group C) were obtained between July 1 2011 and June 30 2012. Two adult patients died (8.7%). Most of the isolates were recovered from blood (60.9%). All isolates carried speJ and ssa genes. stG62647, stG653 and stG840 were the most frequent emm types. Nineteen different PFGE patterns were detected. All isolates were susceptible to penicillin and levofloxacin, 6 (26.1%) showed resistance or reduced susceptibility to erythromycin [1 mef(A), 3 erm(TR), 1 mef(A) + erm(TR) and 1 erm(TR) + erm(B)] and 7 (30.4%) were resistant or exhibited reduced susceptibility to tetracycline [2 tet(M), 5 tet(M) + tet(O)]. The prevalence in Argentina was of at least 23 invasive infections by SDSE. A wide genetic diversity was observed. All isolates carried speJ and ssa genes. Similarly to other studies, macrolide resistance (26.1%) was mainly associated to the MLSB phenotype.Streptococcus dysgalactiae subsp. equisimilis (SDSE) has virulence factors similar to those of Streptococcus pyogenes. Therefore, it causes pharyngitis and severe infections indistinguishable from those caused by the classic pathogen. The objectives of this study were: to know the prevalence of SDSE invasive infections in Argentina, to study the genetic diversity, to determine the presence of virulence genes, to study antibiotic susceptibility and to detect antibiotic resistance genes. Conventional methods of identification were used. Antibiotic susceptibility was determined by the disk diffusion and the agar dilution methods and the E-test. Twenty eight centers from 16 Argentinean cities participated in the study. Twenty three isolates (16 group G and 7 group C) were obtained between July 1 2011 and June 30 2012. Two adult patients died (8.7%). Most of the isolates were recovered from blood (60.9%). All isolates carried speJ and ssa genes. stG62647, stG653 and stG840 were the most frequent emm types. Nineteen different PFGE patterns were detected. All isolates were susceptible to penicillin and levofloxacin, 6 (26.1%) showed resistance or reduced susceptibility to erythromycin [1 mef(A), 3 erm(TR), 1 mef(A)+erm(TR) and 1 erm(TR)+erm(B)] and 7 (30.4%) were resistant or exhibited reduced susceptibility to tetracycline [2 tet(M), 5 tet(M)+tet(O)]. The prevalence in Argentina was of at least 23 invasive infections by SDSE. A wide genetic diversity was observed. All isolates carried speJ and ssa genes. Similarly to other studies, macrolide resistance (26.1%) was mainly associated to the MLSB phenotype.

Interference in culture among Rhizobium strains

Abstract Growth interference in culture was shown by 57 strains of Rhizobium belonging to different inoculation groups. The assays were conducted in vitro by spot tests on agar plates and using 1007 paired combinations, 240 cases of interference were observed. A frequency of interference of about 30% was found among strains of R. meliloti and R. meliloti, R. lupini, R. trifolii and R. leguminosarum. Only one case out of 168 showed interference between R. meliloti and R. japonicum.

Factores de riesgo para la adquisición y características microbiológicas de las bacteriemias por Acinetobacter baumannii multi-resistente en pediatría: Estudio de casos y controles

Tuberculosis (TB) remains a major global and national problem. In Chile the incidence rate has remained at 13 per 100,000 inhabitants for several years without tendency to the expected decline that would allow their elimination by 2020. As a low prevalence country, TB cases have been concentrated in risk groups, reaching 33% in 2013, and this proportion increases as younger people are analyzed. The main risk groups in Chile are HIV co-infection, foreigners and population of prisons. By 2013, the proportion of cases for these three groups was 8.7%, 8.4% and 3.9% respectively, and these percentages vary significantly when regional situation is analyzed. In addition, many of these patients have more than one risk factor, demons-rating the existence of clusters more vulnerable to TB.Background: Multidrug-resistant Acinetobacter baumannii (MAB) is an important nosocomial pathogen. Objectives: To analyze the risk factors for acquiring MAB, and the clinical and microbiological characteristics of MAB bacteremia (MABB) in children. Materials and Methods: Control-case study 2005-2008. Demographic and clinical data from all MABB and from non-multiresistant gram-negative bacteremias were recorded. Identification at species level, antimicrobial susceptibility tests, time-kill studies and clonally relationships were performed. Stata 8.0 was used for data analysis. Results: A total of 50 MABB and 100 controls were included. Ninety four percent of patients acquired MAB in ICU and the 88% had underlying diseases. All patients had invasive procedures previous to MABB. The median of hospitalization stay previous to MABB was different in cases than in controls (16 vs 7 days, p < 0.001). Five clones were detected among the MABB. Time-killing curves showed bactericidal activity of ampicillin/sulbactam plus gentamicin and polymixin B. Three patients with MAB died. In a multivariate analysis final predictors of MABB were: previous use of broad-spectrum antibiotics [OR: 7,0; IC 95% 1,93-25,0; p: 0,003] and mechanical ventilation [OR: 4,19; IC 95% 1,66-10,0; p: 0,002]. Conclusions: MABB were detected in patients with underlying conditions, invasive procedures and prolonged hospitalization. Predictors of MABB were mechanical previous use of broad-spectrum antibiotics and mechanical ventilation.

Infecciones por bacterias poco comunes y oncogénesis bacteriana

The recovery of an unusual organism in the clinical microbiology laboratory may be an indicator of an immunological abnormality in the patient. For instance, an important relationship between Clostridium septicum and colon carcinoma as well as between leukemia or lymphoma with species frequently considered contaminants (Bacillus spp., Corynebacterium spp.) or others rarely isolated from different contexts (Capnocytophaga spp.) were described. Some bacteria are almost exclusively isolated from AIDS patients (Rhodococcus equi). Campylobacter spp., Aeromonas spp., group G and mitis group streptococci were more frequently isolated in individuals suffering from any type of cancer than in other patients. Furthermore, some other bacteria can be considered markers of an undetected cancer that can be found mostly in neutropenic patients rather than in immunologically normal individuals. Possible mechanisms of bacterial oncogenesis include a modification of the inflammatory response, antigen-derived lymphoproliferation, and induction of hormones that increase epithelial cell proliferation. Typical examples of the above are: gastric adenocarcinoma induced by Helicobacter pylori, the association between group bovis bacteremia and colon carcinoma and the mucosa-associated lymphoid tissue (MALT) related to Helicobacter species (gastric MALT) and Chlamydophila spp. (ocular MALT). Isolation of any of these pathogens should require a thorough search for possible malignant diseases.The recovery of an unusual organism in the clinical microbiology laboratory may be an indicator of an immunological abnormality in the patient. For instance, an important relationship between Clostridium septicum and colon carcinoma as well as between leukemia or lymphoma with species frequently considered contaminants (Bacillus spp., Corynebacterium spp.) or others rarely isolated from different contexts (Capnocytophaga spp.) were described. Some bacteria are almost exclusively isolated from AIDS patients (Rhodococcus equi). Campylobacter spp., Aeromonas spp., group G and mitis group streptococci were more frequently isolated in individuals suffering from any type of cancer than in other patients. Furthermore, some other bacteria can be considered markers of an undetected cancer that can be found mostly in neutropenic patients rather than in immunologically normal individuals. Possible mechanisms of bacterial oncogenesis include a modification of the inflammatory response, antigen-derived lymphoproliferation, and induction of hormones that increase epithelial cell proliferation. Typical examples of the above are: gastric adenocarcinoma induced by Helicobacter pylori, the association between group bovis bacteremia and colon carcinoma and the mucosa-associated lymphoid tissue (MALT) related to Helicobacter species (gastric MALT) and Chlamydophila spp. (ocular MALT). Isolation of any of these pathogens should require a thorough search for possible malignant diseases.

La anaerobiosis más allá de las bacterias anaerobias. Su importancia en la recuperación de microorganismos aerobios a partir de materiales purulentos

Anaerobiosis beyond anaerobic bacteria. Its role in the recovery of aerobic microorganisms from purulent samples. The main objective of incubation in anaerobiosis is the recovery of obligate anaerobic bacteria, not excluding other microorganisms. In 2003, we conducted a comparative and prospective study from consecutive clinical samples on the recovery of aerobic microorganisms from primary cultures both in anaerobiosis and aerobiosis of the same sample. The aims were to evaluate the methodology used in anaerobiosis in the recovery of aerobic microorganisms not diagnosed in primary aerobic cultures, and to establish a relationship between them and the origin of the sample. From 2003 to 2004, 2776 bacteriological samples were analyzed and 1884 aerobic microorganisms were cultured altogether. The result was that 69.4% of the samples showed growth both in aerobic and anaerobic incubation from primary cultures of the sample, whereas 30.6% only in one of the mentioned incubation atmosphere: 49.2% in aerobiosis and 50.8% in anaerobiosis. According to these results, the methodology used in anaerobiosis (anaerobic incubation, culture media, stereoscopic microscope or hand lens to examine the primary plates), allowed an extra yield of aerobic organisms, especially gram positive facultative and microaerophilic cocci, which was particularly evident in polimicrobial cultures, and especially when gram negative accompanying flora was present, independently of the type of sample.