No significant effect of 3d modelling on surgical planning in spinal deformities / Nenhum efeito significativo da modelagem 3d no planejamento cirúrgico em deformidades da coluna vertebral

ABSTRACT Objective: To evaluate the effect of 3d printed models on surgical pre-operative planning of complex spinal deformities. Methods: In our study, five orthopedic surgeons made surgical planning of 5 patients with severe spinal deformity in three conditions: X-ray with computer tomography (X-ray-CT), 3D-computed tomography (3dCT), and 3d printed spine models. Operation plans were examined according to the level and number of instrumentations, osteotomy level, and time required for decision-making. Results: X-ray-CT, 3dCT, and 3d modeling methods were compared, and no statistically significant difference was observed in the number of screws and osteotomy score to be used in operation. The time required for decision ranking is 3d Model, 3d CT, and Xray-CT. Conclusions: 3d printed models do not influence the operative plan significantly; however, it reduces surgical planning time at pre-op duration, and those models gave some opportunities to practice with implants on a patient's 3d spine model. Level of Evidence III; Diagnostic Studies - Investigating a Diagnostic Test .

RESUMO Objetivo: Avaliar o efeito de modelos 3D impressos no planejamento pré-operatório cirúrgico de deformidades complexas da coluna vertebral. Métodos: Em nosso estudo, 5 cirurgiões ortopédicos fizeram o planejamento cirúrgico de 5 pacientes com deformidade espinhal grave em três condições: raio-X com tomografia computadorizada (raio X-CT), tomografia computadorizada com reconstrução 3D (3dCT) e modelo de coluna vertebral impressa (modelo 3d). Os planos de operação foram examinados de acordo com o nível e número de instrumentos, nível de osteotomia e tempo necessário para a tomada de decisão. Resultados: Foram comparados os métodos de modelagem de raio X-CT, 3dCT e modelo 3d e nenhuma diferença estatisticamente significativa foi observada no número de parafusos e escore de osteotomia a serem utilizados na operação. O ranking do tempo necessário para a tomada de decisão foi de modelo 3d, 3d CT e raio X-CT. Conclusões: Os modelos impressos em 3d não influenciam significativamente o plano operatório, porém reduzem o tempo de planejamento cirúrgico no pré-operatório e esses modelos deram algumas oportunidades de praticar com implantes no modelo de coluna 3d do paciente. Nível de evidência III; Estudos de Diagnóstico - Investigando um Teste de Diagnóstico .

Antibody production against COVID-19 in hemodialysis patients / Producción de anticuerpos contra COVID-19 en pacientes en hemodiálisis

Abstract Introduction: Dialysis patients may have a very high prevalence and death rate for COVID-19. The aim of this study is to show the level of antibody against SARS-CoV-2 in hemodialysis and staff working in the same dialysis center. Methods: Anti-SARS-CoV-2 IgG antibodies were studied in 156 hemodialysis patients and 27 staff. After a 5-minute resting period, blood pressure was measured and then subsequent to an approximately 12-hour fasting period, blood sample were drawn for biochemistry parameters and anti-SARS-CoV-2 IgG antibodies. Results: Three of hemodialysis patients were diagnosed with COVID-19 in March and their PCR tests were positive. The symptoms of these patients were extreme fatigue and muscle weakness. Anti-SARS-CoV-2 IgG antibodies tests were performed on all patients and staff in July. In total, 13/156 (8.3%) patients were diagnosed as COVID-19 based on anti-SARS-CoV-2 antibodies. The other 10 patients were asymptomatic. The staff and 143 hemodialysis patients had IgG (-). Hemodialysis patients who had anti-SARS-CoV-2 IgG (+) antibodies had decreased level of haemoglobin and high levels of C-reactive protein and alkaline phosphatase. Conclusions: Antibody tests are particularly important for detecting people with COVID-19 who have few or no symptoms. It has also been seen that the spread of infection in the dialysis center can be prevented by very strict precautions.

Resumen Introducción: Los pacientes que se realizan diálisis tienen una prevalencia y una tasa de mortalidad muy alta en lo que respecta a la COVID-19. El objetivo de este estudio fue mostrar la concentración de anticuerpos contra el SARS-CoV-2 en los pacientes de hemodiálisis de un centro y en el personal que trabaja en ese lugar. Material y métodos: Se investigaron los anticuerpos IgG contra el SARS-CoV-2 en 156 pacientes que reciben hemodiálisis y en 27 trabajadores. Se midió la tensión arterial luego de 5 minutos de reposo y, luego de un ayuno de aproximadamente 12 horas, se extrajeron muestras de sangre para determinar variables bioquímicas y la concentración de anticuerpos IgG contra el SARS-CoV-2. Resultados: En marzo, a través de pruebas PCR, se les diagnosticó COVID-19 a tres pacientes en hemodiálisis. Los síntomas de estos pacientes fueron fatiga extrema y debilidad muscular. En julio se realizaron pruebas de anticuerpos IgG contra el SARS-CoV-2 a todos los pacientes y al personal. En total, de los 156 pacientes, 13 (8,3 %) fueron diagnosticados con COVID-19 según los anticuerpos contra el SARS-CoV-2. Los otros 10 resultaron asintomáticos. El personal y 143 pacientes en hemodiálisis tuvieron resultados negativos para IgG. Los pacientes en HD con resultados positivos para IgG contra el SARS-CoV-2 presentaron niveles disminuidos de hemoglobina y niveles altos de proteína C reactiva y fosfatasa alcalina. Conclusiones: Las pruebas de anticuerpos son particularmente importantes para detectar personas con COVID-19 que tengan pocos síntomas o ninguno. También se ha visto que es posible prevenir la propagación de la infección en el centro de diálisis mediante precauciones muy estrictas.

The effect of silane and universal adhesives on the micro-shear bond strength of current resin-matrix ceramics

PURPOSE@#The aim of this in vitro study was to evaluate the effect of silane and universal adhesive applications on the micro-shear bond strength (µSBS) of different resin-matrix ceramics (RMCs). @*MATERIALS AND METHODS@#A total of 120 slides (14 × 12 × 1 mm) were produced from 5 different RMC materials (GC Cerasmart [GC]; Brilliant Crios [BC]; Grandio blocs [GB]; Katana Avencia [KA]; and KZR-CAD HR 2 [KZR]) and sandblasted using 50 µm Al2O3 particles. Each RMC material was divided into six groups according to the surface conditioning (SC) method as follows: control (G1), silane primer (G2), silane-free universal adhesive (G3), silane-containing universal adhesive (G4), silane primer and silane-free universal adhesive (G5), and silane primer and silane-containing universal adhesive (G6). Three cylindric specimens made from resin cement (Bifix QM) were polymerized over the treated surface of each slide (n = 12). After thermal cycling (10000 cycles, 5 – 55℃), µSBS test was performed and failure types were evaluated using a stereomicroscope. Data were analyzed using 2-way ANOVA and Tukey tests (α = .05). @*RESULTS@#µSBS values of specimens were significantly affected by the RMC type and SC protocols (P < .001) except the interaction (P = .119). Except for G2, all SC protocols showed a significant increase in µSBS values (P < .05). For all RMCs, the highest µSBS values were obtained in G4 and G6 groups. @*CONCLUSION@#Only silane application did not affect the µSBS values regardless of the RMC type. Moreover, the application of a separate silane in addition to the universal adhesives did not improve the µSBS values. Silane-containing universal adhesive was found to be the best conditioning method for RMCs.

Epidemiological findings on Hepatitis C infection in a tertiary level hospital in mid-northern Anatolia in Turkey: A four-year analysis

@# The hepatitis C virus (HCV) is a blood-borne pathogen that causes acute or chronic infection of the liver, sometimes leading to serious liver damage and fatality. The objective of this study was to evaluate HCV prevalence in patients attending the Regional Training and Research Hospital for Medical Examination and Surgery in Samsun Province of Turkey between 2014 and 2017. Blood specimens taken from 152 596 patients were screened for HCV infection by using the anti-HCV assay. Seropositive samples were subjected to polymerase chain reaction (PCR) testing in order to determine whether the HCV infection was active. Genotyping was then performed. Overall, HCV seropositivity and active HCV infection were 2.76% and 2.05%, respectively. Foreign nationals accounted for 5.61% of the seropositive samples and 1.37% of active HCV infective samples. We further report that 2017 was the year with the highest seroprevalence which was 3.64%. HCV genotype 1 was the most common genotype detected in residents of Samsun Province at 89.86%, followed by Genotype 3 at 4.54%. This study provides important information on the levels of HCV infection in the Samsun region of Turkey. The data indicate that there was a rising trend of HCV infection between 2014 and 2017.

Examination of paramolar tubercles in Turkish population using cone beam computed tomography / Estudio de los tuberculos paramolares en una población turca mediante tomografía computarizada de haz cónico

SUMMARY: Paramolar tubercle (PT) is an additional cusp occuring on buccal surface of both upper and lower permanent molars. PT is also known as parastyle when tubercle is present in upper molars, as protostylid when tubercle is present in lower molars. The aim of this study was to evaluate prevalence of PTs in Turkish population with cone beam computed tomography (CBCT). Presence of PT in molar teeth were evaluated retrospectively using CBCT images of 210 patients (102 male, 108 female) between 18-77 years old. A total of 909 teeth were analyzed. Because of various reasons some teeth were excluded and final analyze was done with 653 teeth. Prevalence of PT was found as 2.76 % (18 out of 653). Highest frequency of PT was detected 5 in #27, 4 in #17, 2 in #48 among all molar teeth respectively. In two cases; 2 PTs were on the same tooth, bilateral PT was found only in one case. PT was undetected on upper first molars. Prevalence of PTs on permanent molars is a rare phenomenon in the studied population. Use of CBCT in such anatomic variations will provide valuable and detailed information during treatment modalities. Since this pilot study represents Turkish subpopulation, comprehensive studies with increased number of cases should be undertaken to clarify the prevalence of paramolars in Turkish population. Advanced imaging techniques like CBCT will be more helpful in understanding and detecting exact morphological and anatomical variations of PTs during treatment modalities.

RESUMEN: El tubérculo paramolar (TP) es una cúspide adicional que está en la superficie vestibular de los molares permanentes superiores e inferiores. El objetivo de este estudio fue evaluar la predisposición de TP en la población turca con tomografía computarizada de haz cónico (TCHC). Presencia de TP en dientes molares se evaluaron retrospectivamente utilizando imágenes de tomografia de 210 pacientes (102 hombres, 108 mujeres) entre 18-77 años de edad. Se analizó un total de 909 dientes. Por varias razones, algunos dientes fueron excluídos y el análisis final se realizó con 653 dientes. Prevalencia de PTP se encontró en el 2,76 % (18 dientes de 653). La frecuencia más alta de TP se detectó: 5 en # 27, 4 en # 17, 2 en # 48, entre todos los dientes molares, respectivamente. En dos casos, 2 de los TP fueron observados en el mismo diente; TP bilateral sólo se encontró en un caso. El TP no fue detectado en los primeros molares superiores. La prevalencia de TP en los molares permanentes es un fenómeno poco frecuente en la población estudiada. El uso de la TCHC en tales variaciones anatómicas, proporcionará información valiosa y detallada para definir la aplicación de diferentes modalidades de tratamiento. Dado que este estudio piloto representa a una subpoblación turca, estudios exhaustivos con un mayor número de casos deben llevarse a cabo para determinar la prevalencia en la población turca total. Técnicas avanzadas de imagen como TCHC serán más útiles para detectar variaciones morfológicas y anatómicas exactas de TP durante diversas modalidades de tratamiento.

Comparison of effectiveness of intubation by way of "Gum Elastic Bougie" and "Intubating Laryngeal Mask Airway" in endotracheal intubation of patients with simulated cervical trauma / Comparação da eficácia de intubação por meio de guia introdutor Bougie de tubo endotraqueal e máscara laríngea em intubação traqueal de pacientes com trauma cervical simulado

Abstract Purpose: In this study, we evaluated the effectiveness of intubations by way of "Gum Elastic Bougie" and "Intubating Laryngeal Mask Airway" in endotracheal intubation of patients with simulated cervical trauma. Method: 134 patients were included in the study. All patients were placed cervical collar for a simulated cervical trauma. Patients were allocated randomly into three groups: Group NI (n = 45) intubation with Macintosh laryngoscopy, Group GEB (n = 45) intubation with Gum Elastic Bougie, and Group ILMA (n = 44) intubation with Intubating Laryngeal Mask Airway. The number of intubation attempts, success of intubation, duration of complete visualization of the larynx, duration of intubation, user's performance score, hemodynamic changes and the observed complications were recorded. Results: Success of intubation in the first attempt was highest in Group GEB while it was lowest in Group ILMA. Regarding the intubation success, rates of successful intubation were 95.6%, 84.4% and 65.9% in Groups GEB, NI, and ILMA, respectively. Durations of visualization of larynx and intubation were shorter in Groups NI and GEB than in Group ILMA. This difference was statistically significant (p < 0.05) while there was no significant difference between Groups NI and GEB. The number of patients with "good" intubation performance was significantly higher in Group GEB while the number of patients with "poor" intubation performance was significantly higher in Group ILMA (p < 0.05). Conclusions: We conclude that GEB, which is cheap and easily accessible, should be an advantageous choice in cervical trauma patients for both the easeness of intubation and patient morbidity and mortality.

Resumo Objetivo: Neste estudo avaliamos a eficácia de intubações por meio de guia introdutor Bougie e máscara laríngea em intubação endotraqueal de pacientes com trauma cervical simulado. Método: Foram incluídos no estudo 134 pacientes. Colar cervical foi colocado em todos os pacientes para um trauma cervical simulado. Os pacientes foram alocados aleatoriamente em três grupos: Grupo NI (n = 45) foi submetido à intubação com laringoscópio Macintosh; Grupo ITE (n = 45) foi submetido à intubação com guia introdutor de tubo endotraqueal e Grupo ML (n = 44) foi submetido à intubação com máscara laríngea. Número de tentativas de intubação, sucesso de intubação, tempo de visualização completa da laringe, tempo de intubação, escore de desempenho do usuário, alterações hemodinâmicas e complicações observadas foram registrados. Resultados: O sucesso da intubação na primeira tentativa foi maior no Grupo ITE e menor no grupo ML. Ainda em relação ao sucesso da intubação, as taxas de sucesso foram 95,6%, 84,4% e 65,9% nos grupos ITE, NI e ML, respectivamente. Os tempos de visualização da laringe e de intubação foram menores nos grupos NI e ITE do que no Grupo ML. Essa diferença foi estatisticamente significativa (p < 0,05), enquanto não houve diferença significativa entre os Grupos NI e ITE. O número de pacientes com bom desempenho na intubação foi significativamente maior no grupo ITE, enquanto o número de pacientes com mau desempenho na intubação foi significativamente maior no grupo ML (p < 0,05). Conclusões: Concluímos que o ITE, que é barato e facilmente acessível, deve ser uma opção vantajosa em pacientes com trauma cervical, tanto pela facilidade de intubação quanto devido à taxa de morbidade e mortalidade dos pacientes.

Central line-associated bloodstream infections in the intensive care unit: importance of the care bundle / 대한마취과학회지

BACKGROUND: The importance and efficacy of a care bundle for preventing central line-associated bloodstream infections (CLABSIs) and infectious complications related to placing a central venous catheter (CVC) in patients in the intensive care unit (ICU). METHODS: A care bundle was implemented from July 2013 to June 2014 in a medical ICU and surgical ICU. Data were divided into three periods: the prior period (July 2012–June 2013), the intervention period (July 2013–June 2014; first and second periods), and the post-intervention period (July 2014–December 2014; third period). A care bundle consisting of optimal hand hygiene, skin antisepsis with chlorhexidine (2%) allowing the skin to dry, maximal barrier precautions for inserting a catheter (sterile gloves, gown, mask, and drapes), choice of optimal insertion site, prompt catheter removal, and daily evaluation of the need for the CVC was introduced. RESULTS: The catheterization duration was longer and femoral access was more frequently observed in patients with CLABSIs. CLABSI rates decreased with use of the care bundle. The CLABSI rate in the medical ICU was 6.20/1,000 catheter days during the prior period, 3.88/1,000 catheter days during the intervention period, and 1.05/1,000 catheter days during the third period. The CLABSI rate in the surgical ICU was 8.27/1,000, 4.60/1,000, and 3.73/1,000 catheter days during these three periods, respectively. CONCLUSIONS: The choice of an optimal catheter insertion site, use of all barrier precautions, and removal of catheters when they are no longer needed are essential to decrease the CLABSI rate.

Synthesis, antioxidant and anti-microbial properties of two organoselenium compounds

The aim of this study is synthesis of two different series of organoselenium compounds and available in vitro antioxidant and antimicrobial properties of these synthetic compounds. The synthetic compounds were identified by [1]HNMR [300 MHz], [13]C-NMR [75.5 MHz], FT-IR spectroscopic techniques and micro analysis. Antioxidant properties of two synthetic organoselenium compounds were determined by 1, 1- diphenyl-2-picrylhydrazyl [DPPH] radical method, reducing power assay and beta-carotene bleaching method as in vitro. Antimicrobial effects of samples were assessed by the agar dilution procedure and using gram positive and gram-negative bacteria and yeast strains. Although 1, 3-di-p-methoxybenzylpyrimidine- 2-selenone showed better antiradical activity in DPPH test and higher protective activity on beta- carotene, 1-isopropyl-3-methylbenzimidazole-2-selenone was found to be better in reducing power and antimicrobial activity

In Vitro Effects of Rabeprazole on Human Pylorus Tone

BACKGROUND/AIMS: It has been reported that proton pump inhibitors induce relaxation in different types of smooth muscles. The aim of this study is to investigate in vitro effects of proton pump inhibitors on human pylorus muscle. METHODS: Pyloric sphincters were studied in 10 patients who were operated for stomach cancer. In isolated organ bath, control and response to rabeprazole were recorded following contraction with carbachol. During the treatment experiment, while distilled water was applied during the control experiment in every 5 minutes, rabeprazole was administered in every 5 minutes at doses of 10-6, 10-5, 10-4, and 10-3 M respectively. Contraction frequencies, maximum contraction values and muscle tones were measured. RESULTS: The contraction frequencies in the control group were greater than the rabeprazole group in the second, third and fourth intervals while the maximum contraction values in the rabeprazole group were lower in the fourth interval. Even though muscles tones were not different in both groups during all intervals, it was remarkable that the muscle tone was significantly decreased in the rabeprazole group during the fourth interval compared to the first and second intervals. CONCLUSIONS: In the present study, high doses of rabeprazole reduced contraction frequencies, maximum contraction values, and muscle tone of human pylorus.

Nuss Procedure and Factor VII Deficiency: A Case Report.

A 19 year-old boy admitted with pain and discoloration on his chest wall 18 months after a Nuss procedure performed for pectus excavatum deformity. His physical examination revealed that this skin lesion was an ecchymosis. We diagnosed a very rare bleeding disorder due to Factor VII deficiency which is a recessively inherited coagulation disorder where even spontaneous bleedings may be seen. We aimed to discuss the management of the patient, if it had been diagnosed preoperatively and the preoperative preparation before the bar removal.

Restless genital syndrome in a male patient relieved by pramipaxol and gabapentin

A 45 year old male sought consultation in our neurology clinic with the complaint of persistent genital uncomfortable sensations and pain. After extensive investigations, there was no underlying urological or neurological disease demonstrable. He was diagnosed to have restless genital syndrome and was given pramipexole and gabapentin with significant improvement of his symptoms. Our patient suggests that pramipexol and gabapentin may be useful as treatment for restless genital syndrome.

Restless genital syndrome in a male patient relieved by pramipaxol and gabapentin

A 45 year old male sought consultation in our neurology clinic with the complaint of persistent genital uncomfortable sensations and pain. After extensive investigations, there was no underlying urological or neurological disease demonstrable. He was diagnosed to have restless genital syndrome and was given pramipexole and gabapentin with significant improvement of his symptoms. Our patient suggests that pramipexol and gabapentin may be useful as treatment for restless genital syndrome.

Prognostic Impact of the Metastatic Lymph Node Ratio on Survival in Rectal Cancer

PURPOSE: Lymph-node metastasis is the most important predictor of survival in stage III rectal cancer. The number of metastatic lymph nodes may vary depending on the level of specimen dissection and the total number of lymph nodes harvested. The aim of this study was to evaluate whether the lymph node ratio (LNR) is a prognostic parameter for patients with rectal cancer. METHODS: A retrospective review of a database of rectal cancer patients was performed to determine the effect of the LNR on the disease-free survival (DFS) and the overall survival. Of the total 228 patients with rectal cancer, 55 patients with stage III cancer were eligible for analysis. Survival curves were estimated using the Kaplan-Meier method. Cox regression analyses, after adjustments for potential confounders, were used to evaluate the relationship between the LNR and survival. RESULTS: According to the cutoff point 0.15 (15%), the 2-year DFS was 95.2% among patients with a LNR or = 0.15 (P = 0.02). In stratified and multivariate analyses adjusted for age, gender, histology and tumor status, a higher LNR was independently associated with worse DFS. CONCLUSION: This study showed the prognostic significance of ratio-based staging for rectal cancer and may help in developing better staging systems. LNR 0.15 (15%) was shown to be a cutoff point for determining survival and prognosis in rectal cancer cases.

Prognostic Impact of the Metastatic Lymph Node Ratio on Survival in Rectal Cancer

PURPOSE: Lymph-node metastasis is the most important predictor of survival in stage III rectal cancer. The number of metastatic lymph nodes may vary depending on the level of specimen dissection and the total number of lymph nodes harvested. The aim of this study was to evaluate whether the lymph node ratio (LNR) is a prognostic parameter for patients with rectal cancer. METHODS: A retrospective review of a database of rectal cancer patients was performed to determine the effect of the LNR on the disease-free survival (DFS) and the overall survival. Of the total 228 patients with rectal cancer, 55 patients with stage III cancer were eligible for analysis. Survival curves were estimated using the Kaplan-Meier method. Cox regression analyses, after adjustments for potential confounders, were used to evaluate the relationship between the LNR and survival. RESULTS: According to the cutoff point 0.15 (15%), the 2-year DFS was 95.2% among patients with a LNR or = 0.15 (P = 0.02). In stratified and multivariate analyses adjusted for age, gender, histology and tumor status, a higher LNR was independently associated with worse DFS. CONCLUSION: This study showed the prognostic significance of ratio-based staging for rectal cancer and may help in developing better staging systems. LNR 0.15 (15%) was shown to be a cutoff point for determining survival and prognosis in rectal cancer cases.

Thyroid dysfunction in Turkish patients with chronic hepatitis C receiving peginterferon plus ribavirin in the period of 2005-2010

Interferon-α based therapy for chronic hepatitis C (CHC) is associated with thyroiditis and thyroid dysfunction (TD). This study investigated whether TD during pegylated interferon-a (PEG-IFN) plus ribavirin treatment favors sustained viral response (SVR), and also the association between TD and PEG-IFN formulations. This retrospective study was performed in CHC patients who had received PEG-IFN plus ribavirin and had been followed for six months after treatment. Several factors were compared between patients with and without TD. 119 patients were included in the study. De novo incidence of TD was found to be 16.8%, and 16 of the 18 patients with TD achieved SVR. Although this rate was higher than patients without TD according to univariate analysis, logistic regression analysis revealed that there was not a significant association between TD and SVR, whereas baseline thyroperoxidase antibody (anti-TPO) positivity was the only significant predictor of TD. Moreover, TD was not associated with PEG-IFN type. Both interferon-a and hepatitis C virus (HCV) contribute to TD during antiviral therapy. It seems that there is no association between thyroid toxicity and viral clearance or type of PEG-IFN; however, anti-TPO positivity before treatment is the strongest predictor for TD during antiviral therapy.

Genotyping of rifampin-resistant Mycobacterium tuberculosis isolates from western Turkey

Background: Although the rate of multiple drug resistance is high, there is no published data on the transmission rate of drug-resistant strains of Mycobacterium tuberculosis in the Aegean region of western Turkey that are based on molecular methods

Methods: IS6110 and pTBN12 restriction fragment length polymorphism [RFLP] methods were used for typing M. tuberculosis strains isolated from 26 sputum samples from 26 patients

Results: Nineteen of the rifampin-resistant isolates [73.1%] contained 6 to 11 copies of IS6110. Eighteen different IS6110 DNA fingerprint patterns were observed in the 26 rifampin-resistant isolates. Twenty-three of the 26 rifampin-resistant isolates were also resistant to isoniazid. When evaluated together, both methods yielded 21 [80.9%] different banding patterns and the level of clustering was 34.6%. The average number per pattern was 1.23 [26/21]

Conclusion: IS6110 fingerprinting suggests that the rifampin-resistant isolates obtained from the Aegean region had a relatively high clustering rate and were clonally related. These findings showed that the rifampin-resistant isolates are actively transmitted between patients. Urgent measures should be taken to prevent the spread of these resistant strains