Exportation of MDR TB to Europe from Setting with Actively Transmitted Persistent Strains in Peru.

We performed a cross-border molecular epidemiology analysis of multidrug-resistant tuberculosis in Peru, Spain, and Italy. This analysis revealed frequent transmission in Peru and exportation of a strain that recreated similar levels of transmission in Europe during 2007-2017. Transnational efforts are needed to control transmission of multidrug-resistant tuberculosis globally.

Algorithm for the diagnosis of smear-negative pulmonary tuberculosis in high-incidence resource-constrained settings.

OBJECTIVES: Diagnosis of smear-negative pulmonary tuberculosis (SNPT) remains a challenge, particularly in resource-constrained settings. We evaluated a diagnostic algorithm that combines affordable laboratory tools and a clinical prediction rule (CPR). METHODS: We derived, based on published evidence, a diagnostic algorithm for SNPT. Sputum concentration constitutes its first step. In suspects with negative results, SNPT probability is classified with a CPR as low (excluded), high (confirmed) or intermediate. For intermediate patients, sputum Middlebrook 7H9 liquid culture is performed, and they are assessed after 2 weeks. If clinically deteriorated, with still negative liquid culture, bronchoscopy is offered. Otherwise, results of Middlebrook 7H9 culture are awaited. We prospectively evaluated this algorithm against a reference standard of solid and liquid cultures in two reference hospitals in Lima, Peru. RESULTS: 670 SNPT suspects were included from September 2005 to March 2008. The prevalence of SNPT was 27% according to the reference standard. The algorithm's overall accuracy was 0.94 (95% CI 0.91-0.95), its sensitivity was 0.88 (95% CI 0.82-0.92) and its specificity, 0.96 (95% CI 0.94-0.98). Sputum concentration, the CPR, Middlebrook 7H9 sputum culture and bronchoscopic samples defined a diagnosis of SNPT according to the algorithm in 57 (37%), 25 (16%), 63 (41%) and 8(5%) of patients, respectively. 65% of patients were diagnosed within 3 weeks. CONCLUSIONS: The algorithm was accurate for SNPT diagnosis. Sputum concentration, CPR and selective Middlebrook 7H9 culture are essential components.

Screening of inmates transferred to Spain reveals a Peruvian prison as a reservoir of persistent Mycobacterium tuberculosis MDR strains and mixed infections.

It is relevant to evaluate MDR-tuberculosis in prisons and its impact on the global epidemiology of this disease. However, systematic molecular epidemiology programs in prisons are lacking. A health-screening program performed on arrival for inmates transferred from Peruvian prisons to Spain led to the diagnosis of five MDR-TB cases from one of the biggest prisons in Latin America. They grouped into two MIRU-VNTR-clusters (Callao-1 and Callao-2), suggesting a reservoir of two prevalent MDR strains. A high-rate of overexposure was deduced because one of the five cases was coinfected by a pansusceptible strain. Callao-1 strain was also identified in 2018 in a community case in Spain who had been in the same Peruvian prison in 2002-5. A strain-specific-PCR tailored from WGS data was implemented in Peru, allowing the confirmation that these strains were currently responsible for the majority of the MDR cases in that prison, including a new mixed infection.

Novel hypertonic saline-sodium hydroxide (HS-SH) method for decontamination and concentration of sputum samples for Mycobacterium tuberculosis microscopy and culture.

This study evaluated a new decontamination and concentration (DC) method for sputum microscopy and culture. Sputum samples from patients with suspected pulmonary tuberculosis (TB) (n=106) were tested using the proposed hypertonic saline-sodium hydroxide (HS-SH) DC method, the recommended N-acetyl-L-cysteine-sodium citrate-sodium hydroxide (NALC-NaOH) DC method and unconcentrated direct smear (Ziehl-Neelsen) techniques for the presence of mycobacteria using Löwenstein-Jensen culture and light microscopy. Of 94 valid specimens, 21 (22.3%) were positive in culture and were further characterized as Mycobacterium tuberculosis. The sensitivity for acid-fast bacilli (AFB) smears was increased from 28.6% using the direct method to 71.4% (HS-SH) and 66.7% (NALC-NaOH) using DC methods. Both concentration techniques were highly comparable for culture (kappa=0.794) and smear (kappa=0.631) for AFB. Thus the proposed HS-SH DC method improved the sensitivity of AFB microscopy compared with a routine unconcentrated direct smear; its performance was comparable to that of the NALC-NaOH DC method for AFB smears and culture, but it was methodologically simpler and less expensive, making it a promising candidate for evaluation by national TB control programmes in developing countries.

Clinical evaluation of a 16S ribosomal RNA polymerase chain reaction test for the diagnosis of lymph node tuberculosis.

UNLABELLED: Reports on the sensitivity of polymerase chain reaction (PCR) for the diagnosis of lymph node tuberculosis (TB) show divergent results. We evaluated the accuracy of the Roche Amplicor Mycobacterium tuberculosis PCR test with lymph node aspirate and biopsy samples. METHODS: The study was conducted at a public reference hospital in Lima, Peru. From the period of January 2003 to January 2004, we included patients who had lymphadenopathy and in whom the attending physician suspected TB. Aspirate and biopsy samples were submitted for culturing in Lowenstein-Jensen medium, for histopathologic testing, and for PCR. The sensitivity and specificity of PCR were calculated against a reference standard based on histopathologic findings and culture. RESULTS: Our study included 154 patients. Median age was 29 years (interquartile range, 21-40 years); 97 patients (62.9%) were men. Twenty-nine patients (18.8%) had acid fast bacilli-positive histopathologic findings, and 44 (28.6%) had a positive culture result. Using the combination of histopathologic findings and culture as reference standard, 55 patients (35.7%) had a diagnosis of tuberculous lymphadenitis. The sensitivity of the PCR test was 58.2%, and the specificity was 93.9%. For biopsy tissue only, the sensitivity of PCR was 52.7%, and the specificity was 97.0%. For aspirate samples only, the sensitivity of PCR was 47.3%, and the specificity was 96.0%. CONCLUSION: The Amplicor PCR test revealed low sensitivity and high specificity for the diagnosis of lymph node TB. The sensitivity was higher in cases in which the bacillary load was high--in acid fast bacilli-positive samples and among HIV-infected patients. Considering the results of microbiological and PCR tests together, there was still a patient group in whom no final diagnosis could be established.

Extended-spectrum ß-lactamase-producing Enterobacteriaceae in cell phones of health care workers from Peruvian pediatric and neonatal intensive care units.

BACKGROUND: Health care workers (HCWs) use their mobile phones during working hours or medical care. There is evidence that the instruments are colonized with pathogenic microorganisms. Here, we describe levels of Enterobacteriaceae contamination (EC) in cell phones and the risk factors associated with EC in Peruvian intensive care units (ICUs). METHODS: This was a 5-month cohort study among 114 HCWs of 3 pediatric and 2 neonatology ICUs from 3 Peruvian hospitals. A baseline survey collected data on risk factors associated with EC. Swabs were collected from HCWs' phones every other week. RESULTS: Three-quarters of HCWs never decontaminated their phones, and 47% reported using the phones in the ICU >5 times while working. EC was frequent across samplings and sites and was substantially higher in subjects with longer follow-up. Potential risk factors identified did not have strong associations with positive samples (relative risk, 0.7-1.5), regardless of significance. Half of the phones were colonized with an Enterobacteriaceae at least once during the 4 samplings attained on average during the study period. Half of the isolates were multidrug resistant (MDR), and 33% were extended-spectrum ß-lactamase producers. CONCLUSIONS: EC on HCWs' phones was frequent and apparently randomly distributed through the hospitals without clear clustering or strongly associated risk factors for having a positive sample. Based on the level of EC, phones may be considered as potential bacterial reservoirs of MDR and ESBL bacteria.

The validity of cerebrospinal fluid parameters for the diagnosis of tuberculous meningitis.

OBJECTIVES: To assess the diagnostic validity of laboratory cerebrospinal fluid (CSF) parameters for discriminating between tuberculous meningitis (TBM) and other causes of meningeal syndrome in high tuberculosis incidence settings. METHODS: From November 2009 to November 2011, we included patients with a clinical suspicion of meningitis attending two hospitals in Lima, Peru. Using a composite reference standard, we classified them as definite TBM, probable TBM, and non-TBM cases. We assessed the validity of four CSF parameters, in isolation and in different combinations, for diagnosing TBM: adenosine deaminase activity (ADA), protein level, glucose level, and lymphocytic pleocytosis. RESULTS: One hundred and fifty-seven patients were included; 59 had a final diagnosis of TBM (18 confirmed and 41 probable). ADA was the best performing parameter. It attained a specificity of 95%, a positive likelihood ratio of 10.7, and an area under the receiver operating characteristics curve of 82.1%, but had a low sensitivity (55%). None of the combinations of CSF parameters achieved a fair performance for 'ruling out' TBM. CONCLUSIONS: Finding CSF ADA greater than 6 U/l in patients with a meningeal syndrome strongly supports a diagnosis of TBM and permits the commencement of anti-tuberculous treatment.

[Tuberculosis detection in the emergency room: utility of same day smears]. / Detección de tuberculosis en el servicio de emergencia: utilidad de la segunda baciloscopía realizada el mismo día.

Conducting a same day smears is a strategy that has recently been adopted by the World Health Organization. Our study sought to determine the additional diagnostic yield of a second sputum smear taken on the same day among patients with respiratory symptoms, attended at the emergency room from two hospitals in Lima. We included 270 patients from January to November 2011, which were asked two samples of sputum within two hours; the samples were processed by the Ziehl Neelsen method. The frequency of positive sputum smears was 18.5%. The additional diagnostic yield for the second smear was 20.9%. Considering the high prevalence of tuberculosis diagnosed by sputum smear, it is suggested that this test be included routinely in the emergency rooms of hospitals in Lima Metro area.

Caracterización fenotípica y molecular de Escherichia coli productoras de Beta-Lactamasas de espectro extendido en pacientes ambulatorios de Lima, Perú / Phenotypic and molecular characterization of extended spectrum beta-lactamase producing strains of Escherichia coli in ambulatory patients in Lima, Peru

Objetivos: Determinar las características fenotípicas y genotípicas de las β-lactamasas de espectro extendido (BLEE) en E. coli aislados de cultivos de orina de pacientes de la comunidad en un laboratorio privado de la ciudad de Lima, Perú. Material y métodos: Se evaluaron 53 aislamientos de E. coli por dos métodos fenotípicos: Jarlier y CLSI, el perfil de susceptibilidad se realizó mediante disco difusión y la caracterización genotípica mediante PCR para los genes blaCTX-M, blaTEM y blaSHV. Resultados: Los 53 aislamientos productores de BLEE representaron el 16,30% del total de aislados de E. coli, afectando principalmente a mujeres mayores de 65 años. El perfil de susceptibilidad evidenció alta resistencia a AMP,CEF,CRO(100%), LEV(87%), NOR(92%), CIP y NAL(94%), CXM y CTX(96%),SXT(70%), ATM(75%) y TOB (85%); asimismo elevada sensibilidad a NIT e IPM(100%), AMK(91%) y FOF(73,6%). El tipo de gen bla más frecuente fue blaCTX-M (55%), seguido por la coexistencia blaCTX-M+TEM (24%), blaTEM (13%) y blaSHV (6%). Conclusiones: La frecuencia de E. coli productores de BLEE fue de 16,3%; siendo el gen tipo blaCTX-M el más frecuente, información valiosa para orientar la terapia antimicrobiana empírica.

Objective: To determine the phenotypic and genotypic features of extended spectrum beta-lactamase (ESBL) producing strains of Escherichia coli isolated from urine samples of patients attending outpatient services in a private laboratory in Lima, Peru. Methods: 53 E. coli isolates were evaluated using two phenotypic methods: Jarlier and CLSI, the susceptibility profile was performed using the disk diffusion method and the genotypic features were analyzed using PCR for detecting blaCTX-M, blaTEM y blaSHV genes. Results: The 53 ESBL producing strains of E. coli accounted for 16,30% of all E. coli isolates affecting mostly women older than 65 years. High resistant profile to AMP, CEF, CRO (100%), LEV (87%), NOR (92%), CIP, NAL (94%), CXM, CTX (96%), SXT (70%), ATM (75%) and TOB (85%) was observed. High susceptibility to NIT, IPM (100%), AMK (91%) and FOF (73.6%) was observed. The most frequent bla gen was blaCTX-M (55%), followed by blaCTX-M+TEM (24%), blaTEM (13%) and blaSHV (6%). Conclusions: The rate of ESBL producing strains of E. coli was 16.3% and the blaCTX-M gen was the most common gene type. These results provide valuable information for starting empiric antibiotic therapy in this setting.

Evaluation of the performance of two liquid-phase culture media for the diagnosis of pulmonary tuberculosis in a national hospital in Lima, Peru.

OBJECTIVE: To evaluate the diagnostic performance of two liquid-phase culture media for the diagnosis of pulmonary tuberculosis. PATIENTS AND METHODS: From May to July 2003, sputum samples for culture were obtained from patients with respiratory symptoms attending the Hospital Nacional Cayetano Heredia. These were cultured in Ogawa medium, mycobacteria growth indicator tube (MGIT), and modified Middlebrook 7H9. Results were compared against a composite reference standard. RESULTS: One hundred sputum specimens from 100 patients were included. Of these, 33 had culture-proven tuberculosis. The sensitivity of MGIT was found to be 100%. The modified Middlebrook 7H9 medium was found to have a sensitivity of 72.73%, while the sensitivity of Ogawa medium was found to be 69.70%. The mean growing time for MGIT was 12.18 days (95% confidence interval 10.24 to 14.12; p<0.01 vs. Ogawa and modified Middlebrook 7H9); for modified Middlebrook 7H9 was 16.65 days (95% confidence interval 14.85 to 18.80; p<0.01 vs. Ogawa), and for the Ogawa medium 25.74 days (95% confidence interval 22.22 to 29.6). CONCLUSIONS: The liquid culture medium MGIT was superior to the modified Middlebrook 7H9 and the Ogawa media, both in terms of sensitivity and shorter growing time of colonies of Mycobacterium tuberculosis. The modified Middlebrook 7H9 medium is significantly faster but comparable in diagnostic performance to Ogawa. Costs remain an issue for MGIT.

Development of a clinical scoring system for the diagnosis of smear-negative pulmonary tuberculosis.

This study developed a clinical score based on clinical and radiographic data for the diagnosis of smear-negative pulmonary tuberculosis (SNPT). SNPT was defined as a positive culture in Ogawa in a patient with two negative sputum smears. Data from patients admitted to the emergency ward with respiratory symptoms and negative acid-fast bacilli (AFB) smears was analyzed by means of logistic regression to develop the predictive score.Two hundred and sixty two patients were included. Twenty patients had SNPT. The variables included in the final model were hemoptysis, weight loss, age > 45 years old, productive cough, upper-lobe infiltrate, and miliary infiltrate. With those, a score was constructed. The score values ranged from -2 to 6. The area under the curve for the ROC curve was 0.83 (95% CI 0.74-0.90). A score of value 0 or less was associated with a sensitivity of 93% and a score of more than 4 points was associated with a specificity of 92% for SNPT. Fifty-two point twenty-nine percent of patients had scores of less than one or more than four, what provided strong evidence against and in favor, respectively, for the diagnosis of SNPT. The score developed is a cheap and useful clinical tool for the diagnosis of SNPT and can be used to help therapeutic decisions in patients with suspicion of having SNPT.

Staphylococcus aureus resistente a meticilina adquirido en la comunidad aislados en tres hospitales de Lima-Perú / Methicillin resistant Staphylococcus aureus isolates acquired in the community in three hospitals in Lima, Peru

Staphylococcus aureus es un importante patógeno involucrado en una serie de infecciones e intoxicaciones, presenta múltiples factores de virulencia y su impacto se incrementa por su notable resistencia a los antimicrobianos. Objetivo: Determinar la frecuencia de Staphylococcus aureus meticilino resistente adquiridos en la comunidad, en hospitales de Lima- Perú. Material y métodos: Se realizó un estudio descriptivo multicéntrico. La resistencia a meticilina se determinó por el método Oxacillin Agar Screen. El origen de la cepa fue determinado mediante los criterios de los CDC; la Leucocidina de Panton Valentine fue identificada por métodos moleculares. Resultados: Se aislaron 276 cepas de Staphylococcus aureus, 160 fueron resistentes a meticilina (58 por ciento), 9 de ellas fueron identificadas como adquiridas en la comunidad (5,6 por ciento). La PVL fue identificada en 25 cepas (9,1 por ciento), 14 fueron MSSA y 11 MRSA, de éstas últimas solo 4 fueron MRSAcom, 7 fueron MRSAhosp (p menor que 0,001). Conclusiones: El estudio revela niveles elevados de resistencia a meticilina, pero niveles bajos de MRSAcom. En nuestro medio la presencia de PVL no constituiría un marcador para la identificación de los MRSAcom.

Background: Staphylococcus aureus is an important pathogen involved in a series of infections and toxin mediated syndromes, has many virulence factors and its impact increases its resistance to antimicrobial agents. Objectives: To determine the frequency of community acquired methicillin resistant Staphylococcus aureus among hospitals in Lima -Peru. Material and Methods: We performed a prospective multicenter study. The resistance to methicillin was determined by the Oxacillin Agar Screen method. The origin of the strain was determined using CDC criteria, the Panton Valentine Leucocidin was identified by molecular methods. Results: We isolated 276 strains of Staphylococcus aureus, 160 were resistant to methicillin (58 per cent). 9 strains were identified as community acquired MRSA (5.6 per cent). The Panton Valentine Leucocidin was identified in 25 strains (9.1 per cent), 14 were MSSA and 11 MRSA, only 4 of the latter were CA MRSA, 7 were HA MRSA (p less than 0.001). Conclusions: The study showed frequencys of methicillin resistance, but low CA MRSA. In our environment the presence of PVL would not be a marker for the identification of CA MRSA.

Evaluación del medio middlebrook 7h11 asociado a sangre humana u ovina para la detección de mycobacterium tuberculosis en muestras de esputo / Evaluation of middlebrook 7h11 associated with human or sheep blood for the detection of mycobacterium tuberculosis in sputum samples

Objetivo. Evaluar el rendimiento diagnóstico del medio Middlebrook 7H11 combinado con sangre humana u ovina en comparación con el medio sólido Ogawa para el diagnóstico de tuberculosis pulmonar. Materiales y métodos. Se evaluaron muestras de esputo provenientes de pacientes con sospecha de tuberculosis pulmonar. Las muestras fueron sembradas en agar Middlebrook 7H11 asociado a sangre humana u ovina y en medio Ogawa. Resultados. Se recolectaron un totalde 130 muestras. La positividad para M.tuberculosis en Middlebrook 7H11/sangre humana, Midlebrook 7H11/sangre ovina y Ogawa fue de 45,38 por ciento, 46,15 por ciento y 43,84 por ciento respectivamente. El tiempo de crecimiento promedio del Mycobacterium tuberculosis fue de 12,81 mas o menos 6,52, 13,07 mas o menos 6,63 y 20,14 mas o menos 6,75 días (p menor que 0,01 para la comparación de los medios basados en agar vs Ogawa). Conclusiones. La combinación de Middlebrook 7H11 con agar sangre u ovina presenta un rendimiento diagnóstico comparable y un tiempo de crecimiento menor que el medio sólido Ogawa.

Objective. To evaluate the diagnostic yield of the media Middlebrook 7H11 combined with human or ovine blood incomparison with the Ogawa solid media for the diagnosis of pulmonary tuberculosis. Material and methods. Weevaluated sputum samples of patients with clinical suspicion of pulmonary tuberculosis. The samples were seeded in Middlebrook 7H11 agar associated with human or ovine blood and in Ogawa media. Results. A total of 130 samples were collected. The positivity for M.tuberculosis in Middlebrook 7H11/human blood, Middlebrook 7H11/sheep blood and Ogawa was 45.38 per cent, 46.15 per cent and 43.84 per cent respectively. The mean times for growth for the M. tuberculosis were 12.81 more or less 6.52, 13.07 more or less 6.63 and 20.14 more or less 6.75 days (p minor that 0,01 for the comparison of agar based medium versus Ogawa). Conclusions. The combination of Middlebrook 7H11 with sheep or human blood has a comparable diagnostic yield but a shorter growth time than the Ogawa solid media.

Development of a clinical scoring system for the diagnosis of smear-negative pulmonary tuberculosis

This study developed a clinical score based on clinical and radiographic data for the diagnosis of smear-negative pulmonary tuberculosis (SNPT). SNPT was defined as a positive culture in Ogawa in a patient with two negative sputum smears. Data from patients admitted to the emergency ward with respiratory symptoms and negative acid-fast bacilli (AFB) smears was analyzed by means of logistic regression to develop the predictive score.Two hundred and sixty two patients were included. Twenty patients had SNPT. The variables included in the final model were hemoptysis, weight loss, age > 45 years old, productive cough, upper-lobe infiltrate, and miliary infiltrate. With those, a score was constructed. The score values ranged from -2 to 6. The area under the curve for the ROC curve was 0.83 (95 percent CI 0.74-0.90). A score of value 0 or less was associated with a sensitivity of 93 percent and a score of more than 4 points was associated with a specificity of 92 percent for SNPT. Fifty-two point twenty-nine percent of patients had scores of less than one or more than four, what provided strong evidence against and in favor, respectively, for the diagnosis of SNPT. The score developed is a cheap and useful clinical tool for the diagnosis of SNPT and can be used to help therapeutic decisions in patients with suspicion of having SNPT.

Identificación rápida de mutaciones puntuales en el gen katG (Catalasa-Peroxidasa) en cepas de Mycobacterium tuberculosis resistentes a isoniacida / Rapid identification of punctual mutations in the gene katG (Catalasa-Peroxidasa) in Mycobacterium's vine-stocks resistant tuberculoses to isoniacida

Antecedentes: Emplear los métodos tradicionales para la determinación de la susceptibilidad del Mycobacterium tuberculosis a diferentes antibióticos demora en el mejor de los casos 8 semanas. Si usßramos técnicas de biología molecular la identificación de cepas de Mycobacterium tuberculosis resistentes, mediante la detección rßpida de los polimorfismos asociados en estos genes, sería en unas pocas horas. Métodos: En94 cultivos positivos de M. tuberculosis resistentes a isoniacida se hizo la extracción de ADN según lo descrito por Van Soolingen. Con el ADN se uso la reacción en cadena de la polimerasa (PCR) para la amplificación del gen katG. Para detectar la mutación Arg463Leu el fragmento amplificado fue digerido con Nci1 . La mutación del codón 315 fue detectada por digestión del producto de PCR con MspA1l. Resultados: Se encontró que sólo 9 (9.5 por ciento) de las 94 cepas resistentes tenían una mutación en el codón 463. En cambio con la endonucleasa de restricción MspA1l hemos encontrado que las 94 (100 por ciento) cepas tenían una mutación en el codón 315, siendo lamßs prevalente AGC@AAC(Ser315Thr).Conclusiones: El 100 por ciento de las 94 cepas de M. tuberculosis resistentes a isoniacida tuvieron una mutación en el codón 315 del gen katG.

Caracterización de las mutaciones en el gen rpoß asociadas a la resistencia a rifampicina en pacientes con tuberculosis pulmonar / Description of gene rpoß mutations associated with rifampicin resistance in patients with pulmonary tuberculosis

Antecedentes: la resistencia a rifampicina en M. tuberculosis involucra mutaciones en el gen rpoß que codifica a la subunidad ß de la ARN polimerasa. Objetivo: Identificar las mutaciones del gen rpoß, en cepas de M. tuberculosis asosciadas con resistencia a rifampicina aisladas de la Subregión de Salud Lima Norte, Perú. Materiales y métodos: Se cultivó en Lowestein - Jenseen 73 muestras de esputo de pacientes con tuberculosis pulmonar. A 62, con más de 10 colonias por tubo, se les comprobó susceptibilidad a isoniazida, rifampicina, estreptomicina y etambutol. Se realizó la extracción de ADN por PCR, clonación en el vector pGEM-T, transformación, selección de clonas recombinantes y secuenciamiento del ADN plasmídico para la determinación de los polimorfismos del gen rpoß. Resultados: 52 (83,9 por ciento) cepas fueron resistentes a rifampicina (Rif) y 10 (16,1 por ciento) susceptibles (Rif). Se encontró alteraciones en el gen rpoß en 51 de 52 cepas Rif. Se identificaron 20 mutaciones. Las mutaciones más frecuentes fueron encontradas en los codones Ser-531 (62,7 por ciento), His-526 (15,7 por ciento), Asp-516 (11,8 por ciento) y Gln-513 (5,9 por ciento). No se observó mutación alguna en las 10 cepas Rif. 94,2 por ciento de nuestras cepas Rif fueron también resistentes a isoniazida. Conclusiones: Se encontraron mutaciones en el gen rpoß de casi todas las cepas Rif; asimismo, casi todas las cepas Rif fueron también resistentes a isoniazida.