Chimeric Antigen Receptor T Cell Therapies: A Review of Cellular Kinetic-Pharmacodynamic Modeling Approaches

Chimeric antigen receptor T cell (CAR-T cell) therapies have shown significant efficacy in CD19+ leukemias and lymphomas. There remain many challenges and questions for improving next-generation CAR-T cell therapies, and mathematical modeling of CAR-T cells may play a role in supporting further development. In this review, we introduce a mathematical modeling taxonomy for a set of relatively simple cellular kinetic-pharmacodynamic models that describe the in vivo dynamics of CAR-T cell and their interactions with cancer cells. We then discuss potential extensions of this model to include target binding, tumor distribution, cytokine-release syndrome, immunophenotype differentiation, and genotypic heterogeneity.

Abstract 509: Conversion of cellular kinetic data for chimeric antigen receptor T-cell therapy (CAR-T) into interpretable units

Objectives: Cellular kinetic (CK) measurement of CAR-T cell expansion in-vivo by quantitative polymerase chain reaction (qPCR) has been measured in units of transgene copy number/μg of DNA. We propose a formula to convert the qPCR, and flow cytometry (FC) measurements to interpretable numbers of CAR T-cells/μL blood. Further, after the conversion CK parameters were correlated with efficacy/safety endpoints.

Methods: CK data measured using both qPCR and FC assays were utilized from the ELIANA trial in pediatric and young adult patients with relapsed and refractory acute lymphoblastic leukemia (pALL). qPCR measures the presence of CAR transgene in cells with units of copies of CAR-DNA/μg of genomic DNA, while FC quantifies surface expression of CAR T-cells as the % of either T-cells or white blood cells (WBCs) that express CAR. Neither measurement accounts for the typical significant increase in WBCs following CAR-T infusion. We propose equations for converting FC (Eq1) or qPCR (Eq2) into concentration of CAR-cells/μL of blood, using WBC counts from the complete blood count. For qPCR, the equation relies on 3 additional parameters M·F/N: amount of DNA/WBC (M), average number of copies of CAR-DNA/CTL019 cell (N), and fraction of cells with CAR-DNA that express CAR receptor (F). To estimate M·F/N, we performed regression of the cells/μL estimate from FC vs qPCR. We fit the CK model [1] to obtain the model parameters. Finally, CK parameters with safety/efficacy were correlated to compare the converted estimates to the native CK units. • (CD3+CAR+cells)/μl blood= WBC/μl blood × (CD3+CAR+cells)/WBC (1) • (CAR+cells)/μl blood=WBC/μl blood × CAR DNA copies/μg DNA × M μg DNA/WBC × 1 CAR cell/N CAR DNA copies×F (2)

Results: There was high correlation between FC and qPCR estimates of CAR-T in the blood of pALL patients (r2=0.775). The M·F/N value derived based on FC and qPCR results was estimated as 2.68e-6μg DNA/CAR copies. Assuming M=6.6e-6μg DNA/WBC [2] and F=1, this predicts that N=2.46 CAR copies/CAR-T cell. There was also high correlation between the copies/μg and cells/μL estimates using qPCR (r2=0.752). The relationship between CK parameters and safety/efficacy endpoints was not improved when cells/μL was used. This can be attributed to high correlation between these metrics. Using the CK model, 11x greater fold expansion was predicted using the cells/μL estimate compared to copies/μg. This is because cells/μL estimate accounts the expansion of both CAR-T and WBC numbers following lymphodepletion.

Conclusions: The conversion of CK into cells/μL allows for a physiological interpretation of CK data with a high correlation between the cells/μL and copies/μg indicating either metric can be used to predict safety/efficacy.

References: 1 Stein M et al. CPT: Pharmacometrics & Systems Pharmacology(2019) 2 Gillooly JF et al. Cold Spring Harbor Perspectives in Biology vol.7,7 a019091(2015)

Citation Format: Anwesha Chaudhury, Andrew Stein, Stephan Grupp, John Levine, Michael Pulsipher, G Doug Myers, Edward Waldron, Xu Zhu, Fraser McBlane, Rakesh Awasthi, Edmund K. Waller. Conversion of cellular kinetic data for chimeric antigen receptor T-cell therapy (CAR-T) into interpretable units [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 509.

Correlative Biomarker Analysis of Intrinsic Subtypes and Efficacy Across the MONALEESA Phase III Studies

PURPOSE

The prognostic and predictive value of intrinsic subtypes in hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer treated with endocrine therapy and ribociclib (RIB) is currently unknown. We evaluated the association of intrinsic subtypes with progression-free survival (PFS) in the MONALEESA trials.

METHODS

A retrospective and exploratory PAM50-based analysis of tumor samples from the phase III MONALEESA-2, MONALEESA-3, and MONALEESA-7 trials was undertaken. The prognostic relationship of PAM50-based subtypes with PFS and risk of disease progression by subtype and treatment were evaluated using a multivariable Cox proportional hazards model, adjusting for age, prior chemotherapy, performance status, visceral disease, bone-only metastases, histological grade, number of metastatic sites, prior endocrine therapy, and de novo metastatic disease.

RESULTS

Overall, 1,160 tumors from the RIB (n = 672) and placebo (n = 488) cohorts were robustly profiled. Subtype distribution was luminal A (LumA), 46.7%; luminal B (LumB), 24.0%; normal-like, 14.0%; HER2-enriched (HER2E), 12.7%; and basal-like, 2.6% and was generally consistent across treatment arms and trials. The associations between subtypes and PFS were statistically significant in both arms (P < .001). The risks of disease progression for LumB, HER2E, and basal-like subtypes were 1.44, 2.31, and 3.96 times higher compared with those for LumA, respectively. All subtypes except basal-like demonstrated significant PFS benefit with RIB. HER2E (hazard ratio [HR], 0.39; P < .0001), LumB (HR, 0.52; P < .0001), LumA (HR, 0.63; P = .0007), and normal-like (HR, 0.47; P = .0005) subtypes derived benefit from RIB. Patients with basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .77).

CONCLUSION

In this retrospective exploratory analysis of hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer, each intrinsic subtype exhibited a consistent PFS benefit with RIB, except for basal-like.

Abstract GS1-04: Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA Phase III studies

Background: The prognostic and predictive value of the 4 main intrinsic subtypes of breast cancer (ie, luminal A [LumA], luminal B [LumB], human epidermal growth factor receptor 2 enriched [HER2E], and basal-like) in hormone receptor-positive, HER2− advanced breast cancer (ABC) treated with endocrine therapy (ET) and ribociclib (RIB) is currently unknown. The MONALEESA-2, -3, and -7 trials all showed a significant benefit in progression-free survival (PFS) with RIB over placebo (PBO; Hortobagyi et al. Ann Oncol. 2018; Slamon et al. J Clin Oncol. 2018; Tripathy et al. Lancet Oncol. 2018). Here, we correlate ABC intrinsic subtypes with the PFS benefit of RIB in the MONALEESA trials. Methods: Patient samples from the MONALEESA-2, -3, and -7 trials underwent PAM50-based subtyping (blinded from clinical data), and the correlation between intrinsic subtype and PFS was analyzed. Gene expression profiling of formalin-fixed, paraffin-embedded tumor samples was performed using a customized NanoString nCounter GX 800-gene panel. The prognostic and/or predictive relationship of PAM50-based subtypes with PFS and the risk of tumor progression by subtype were evaluated using univariate and multivariable Cox proportional hazards models. Multivariable models were adjusted for known clinical prognostic factors, including age, prior chemotherapy, prior ET, ECOG performance status, visceral disease (presence of liver/lung metastases), bone-only metastases, histological grade, number of metastatic sites, and de novo metastatic disease. Results: A total of 1160 tumor samples from both the RIB (n = 672) and PBO (n = 488) treatment arms of the MONALEESA trials were profiled. Subtype distribution was generally consistent across treatment arms (Table). The associations between intrinsic subtypes and PFS were statistically significant in both treatment arms (P &lt; .0001). Compared with patients with LumA subtype, which is the subtype that is the most prevalent and has the best prognostic outcome, patients with LumB, HER2E, and basal-like subtypes had a 1.41, 2.30, and 3.97 times higher risk of tumor progression, respectively, after adjusting for other clinical-pathologic variables and treatment arm. In terms of treatment benefit, all subtypes except for basal-like showed a significant PFS benefit with RIB treatment (Table). Patients with HER2E (hazard ratio [HR], 0.389; P &lt; .0001), LumB (HR, 0.521; P = .0001), LumA (HR, 0.633; P = .0007), and normal-like (HR, 0.467; P = .0005) subtypes all derived benefit from RIB treatment, with HER2E demonstrating the greatest benefit. Patients with the basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .767), although these results should be interpreted with caution due to the small sample size (RIB: 2%; PBO: 3%). Conclusions: This is the largest analysis evaluating the correlation of intrinsic ABC subtype with efficacy outcomes in patients treated with CDK4/6 inhibitors. Patients with HER2E, LumA, LumB, and normal-like subtypes all exhibited a consistent PFS benefit with RIB treatment, while patients with basal-like ABC (RIB: 2%; PBO: 3%) did not. The HER2E subtype (RIB: 14%; PBO: 11%) exhibited the greatest relative reduction in risk of progression or death (61%) with RIB plus ET.

Table.SubtypeTreatment ArmDistribution, n (%)Median PFS, months, (95% CI)HRP ValueLuminal ARIB320 (48)29.60 (23.03-NA)0.63.0007PBO222 (45)19.48 (15.61-24.80)Luminal BRIB154 (23)22.21 (18.79-NA)0.52&lt; .0001PBO124 (25)12.85 (10.98414.82)HER2-enrichedRIB95 (14)16.39 (12.71-24.6)0.39&lt; .0001PBO52 (11)5.52 (3.12-9.17)BasalRIB16 (2)3.71 (1.91-13)1.15.77PBO14 (3)3.58 (1.87-NA)NormalRIB87 (13)22.34 (16.56-NA)0.47.0005PBO76 (16)11.10 (7.39-16.56)NA, not achieved.

Citation Format: Aleix Prat, Anwesha Chaudhury, Nadia Solovieff, Laia Paré, Debora Martinez, Nuria Chic, Olga Martínez, Fara Brasó-Maristany, Karen Rodriguez-Lorenc, Tetiana Taran, Naveen Babbar, Faye Su. Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA Phase III studies [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS1-04.

Single-cell modeling of routine clinical blood tests reveals transient dynamics of human response to blood loss

Low blood count is a fundamental disease state and is often an early sign of illnesses including infection, cancer, and malnutrition, but our understanding of the homeostatic response to blood loss is limited, in part by coarse interpretation of blood measurements. Many common clinical blood tests actually include thousands of single-cell measurements. We present an approach for modeling the unsteady-state population dynamics of the human response to controlled blood loss using these clinical measurements of single-red blood cell (RBC) volume and hemoglobin. We find that the response entails (1) increased production of new RBCs earlier than is currently detectable clinically and (2) a previously unrecognized decreased RBC turnover. Both component responses offset the loss of blood. The model provides a personalized dimensionless ratio that quantifies the balance between increased production and delayed clearance for each individual and may enable earlier detection of both blood loss and the response it elicits.

Oxygen-dependent flow of sickle trait blood as an in vitro therapeutic benchmark for sickle cell disease treatments

Although homozygous sickle cell disease is often clinically severe, the corresponding heterozygous state, sickle cell trait, is almost completely benign despite the fact that there is only a modest difference in sickle hemoglobin levels between the two conditions. In both conditions, hypoxia can lead to polymerization of sickle hemoglobin, changes in red cell mechanical properties, and impaired blood flow. Here, we test the hypothesis that differences in the oxygen-dependent rheological properties in the two conditions might help explain the difference in clinical phenotypes. We use a microfluidic platform that permits quantification of blood rheology under defined oxygen conditions in physiologically sized microchannels and under physiologic shear rates. We find that, even with its lower sickle hemoglobin concentration, sickle trait blood apparent viscosity increases with decreasing oxygen tension and may stop flowing under completely anoxic conditions, though far less readily than the homozygous condition. Sickle cell trait blood flow becomes impaired at significantly lower oxygen tension than sickle cell disease. We also demonstrate how sickle cell trait can serve as a benchmark for sickle cell disease therapies. We characterize the rheological effects of exchange transfusion therapy by mixing sickle blood with nonsickle blood and quantifying the transfusion targets for sickle hemoglobin composition below which the rheological response resembles sickle trait. These studies quantify the differences in blood flow phenotypes of sickle cell disease and sickle cell trait, and they provide a potentially powerful new benchmark for evaluating putative therapies in vitro.

Molecular characterization of Orientia tsutsugamushi serotypes causing scrub typhus outbreak in southern region of Andhra Pradesh, India

Background & objectives:

Scrub typhus is a vector-borne zoonotic infection caused by Orientia tsutsugamushi. Local epidemiology of the circulating serotypes of scrub typhus is not available from most parts of India. We conducted this study for the diagnosis of scrub typhus using IgM ELISA and to detect O. tsutsugamushi serotypes circulating in southern Andhra Pradesh, India.

Methods:

Samples were collected from patients clinically suspected to have scrub typhus and were subjected to IgM ELISA to measure IgM antibodies against O. tsutsugamushi. Nested polymerase chain reaction (PCR) was performed targeting strain-specific regions in ELISA-positive samples.

Results:

Of a total of 663 samples, 258 (38.91%) were found to be positive by IgM ELISA. Serotypes could be detected in 230 (34.69%) samples only. Only two serotypes, Karp and Kawasaki, were found in the serum samples, with the former being predominant. The dual infection of Karp and Kawasaki serotypes was found in seven patients. Other serotypes such as Gilliam, Kuroki and Kato were not detected in the samples.

Interpretation & conclusion:

The nested PCR products proved useful in presumptively identifying the endemic O. tsutsugamushi serotypes. The present study could be significant in understanding scrub typhus epidemiology in this region.

Effect of 4-methoxy 1-methyl 2-oxopyridine 3-carbamide on Staphylococcus aureus by inhibiting UDP-MurNAc-pentapeptide, peptidyl deformylase and uridine monophosphate kinase

AIMS

The present study aimed to investigate the anti-Staphylococcus aureus and anti-biofilm properties of 4-methoxy-1-methyl-2-oxopyridine-3-carbamide (MMOXC) on S. aureus UDP-MurNAc-pentapeptide (MurF), peptidyl deformylase (PDF) and uridine monophosphate kinase (UMPK).

METHODS AND RESULTS

The in vitro efficacy of MMOXC was evaluated using quantitative polymerase chain reaction, in vitro assays and broth microdilution methods. Further, the minimum inhibitory concentration (MIC), IC₅₀ and zone of inhibition were recorded in addition to the anti-biofilm property. MMOXC inhibited pure recombinant UMPK and PDF enzymes with a K_i of 0·37 and 0·49 μmol l^-1 . However K_i was altered for MurF with varying substrates. The MurF K_i for UMT, d-Ala-d-Ala and ATP as substrates was 0·3, 0·25 and 1·4 μmol l^-1 , respectively. Real-time PCR analysis showed a significant reduction in PDF and MurF expression which correlated with the MIC₉₀ at 100 μmol l^-1 and IC₅₀ in the range 42 ± 1·5 to 50 ± 1 μmol l^-1 against all strains tested. At 5 μmol l^-1 MMOXC was able completely to remove preformed biofilms of S. aureus and other drug resistant strains.

CONCLUSIONS

MMOXC was able to kill S. aureus and drug resistant strains tested by inhibiting MurF, UMPK and PDF enzymes and completely obliterated preformed biofilms.

SIGNIFICANCE AND IMPACT OF THE STUDY

Growth reduction and biofilm removal are prerequisites for controlling S. aureus infections. In this study MMOXC exhibited prominent anti-S. aureus and anti-biofilm properties by blocking cell wall formation, RNA biosynthesis and protein maturation.

Comparative evaluation of recombinant HSP70 (N & C-terminal) fragments in the detection of equine trypanosomosis

Trypanosomosis (Surra) is an economically important disease caused by Trypanosoma evansi which is an extracellular parasite present in the plasma, tissues and other body fluids of a wide range of hosts including domesticated animals. Currently, serological reports are based on detection of antibodies by ELISA using whole cell lysate (WCL) antigen, which has a limitation of persistence of anti-trypanosomal antibodies after successful treatment of the disease. Moreover, it has some ethical issues also like requirement of mice for in vivo maintenance of parasite for preparing the antigen. Therefore, in the present study, an attempt was made to evaluate the in vitro production of recombinant heat shock protein 70 (HSP70) for detection of antibodies in experimentally infected ponies. The amino acid sequence analysis of HSP70 revealed that N-terminal region of the protein was highly conserved while the C-terminal region was most divergent. The four different regions of HSP70 protein viz. HSP-1, HSP-2, HSP-3 and HSP-4 were cloned and expressed, among which HSP-1 (N-terminal region) & HSP-2 (C-terminal region) were truncated while HSP-3 & HSP-4 were complete C-terminal proteins. The recombinant fragments were probed with sequentially pooled experimental serum samples where antibodies were detected in these fragments from 10(th) day post infection till the termination of the experiment. Further, these recombinant fragments were also comparatively evaluated with WCL antigen in ELISA using experimental as well as field serum samples. It was observed that after successful treatment of infected ponies, there was a sharp fall in antibodies (within 90 days) when tested with recombinant HSP's fragments, while antibodies persisted even after 469 days when tested against WCL antigen. The sensitivity and specificity of all HSP70 fragments were also estimated from field serum samples with reference to WCL antigen ELISA. The HSP-1 showed minimum sensitivity (41.03%) among all the recombinant fragments. Among the C-terminal fragments, maximum sensitivity was observed with the HSP-2 (61.54%) while minimum was observed with HSP-4 (48.72%). The specificity increases for recombinant fragments from N-terminal to C-terminal region of protein and maximum specificity was observed with HSP-4 fragment (91.3%).

Cutaneous fungal infection in a renal transplantation patient due to a rare fungus belonging to order Pleosporales

Fungal infections are being increasingly reported from immuno-compromised as well as immuno-competent patients. Transplant patients are on long term immunosuppressive therapy which makes them highly vulnerable to opportunistic fungal infections .These infections can be cutaneous or systemic. Several fungi have been reported to be the culprits such as Candida spp., Aspergillus spp., C. neoformans, P. carinii, and zygomycetes group of fungi. Cutaneous infections are most commonly caused by Pityriasis (tinea) versicolor, dermatophytes, and candida sp but these days the demtiaceous fungi are becoming more frequently reported .Here we report a case of post renal transplant cutaneous infection caused by dematiaceous fungus belonging to the order Pleosporales.

Abstract P3-07-05: Frequent BRCA1 and BRCA2 mutations are found in Mexican and Mexican-American women with breast cancer

Background: The Arizona Cancer Registry has shown that in Pima County, AZ, breast cancer diagnosed in young Latinas increased 40% from 2004-2008, compared to 1999-2003, and Latinas more likely to die of their cancer. This study seeks to characterize genetic variation in women of Mexican ancestry with breast cancer using next generation sequencing, with the goal of providing prevalence information to help guide screening and cancer prevention efforts.

Methods: The ELLA Binational Breast Cancer Study enrolled women of Mexican ancestry living in either U.S. or Mexico within 24 months of breast cancer diagnosis. Mexican women from the state of Jalisco were collected through collaboration with the Universidad de Guadalajara and women of Mexican ancestry were recruited from Tucson and Phoenix, AZ. Genomic DNA from 92 ELLA study participants (49 from the U.S. and 43 from Mexico) was enriched for breast cancer influencing gene sequence using the BROCA panel with standard techniques. Samples were sequenced with next generation sequencing and variants identified.

Results: Sequencing of breast cancer risk genes in 92 Mexican and Mexican-American women with breast cancer revealed the presence of deleterious mutations in 15% of women (14/92). Five carry mutations in BRCA1, 5 in BRCA2, 2 in CHEK2, 1 in PALB2 and 1 in RAD51C. An additional 9% of participants (8/92) carry rare mutations of unknown functional consequence in the same genes. Four carry mutations in BRCA1 or BRCA2 at sites predicted to alter splice enhancers and four carry missense mutations in CHEK2 that are predicted to damage to kinase function. None of these variants appear in public databases or are characterized functionally in gene-specific databases. Dozens of women carry VUS or novel variants.

Women carrying BRCA1 mutations are significantly more likely to have had triple negative pathology. Women carrying other mutations known or thought to be deleterious are also more likely to have been younger at diagnosis, to have more aggressive breast cancer or to report a family history of breast cancer.

Table 1. Deleterious MutationsGeneEffectTotalBRCA1185delAG1BRCA12569delC2BRCA1Del Complete Gene1BRCA1Del Exons 9-121BRCA2c.658delGT1BRCA2c.3264insT2BRCA2c.5195delT1BRCA2c.6024insG1CHEK2R160G2PALB2S779 Stop1RAD51CDel Exons 4-91

Conclusion: Deleterious BRCA1 and BRCA2 gene mutations are common among women of Mexican ancestry diagnosed with breast cancer. Within this cohort, the prevalence of BRCA1/2 mutations is 11%, and 4% of women carry mutations in other genes increasing breast cancer risk. This is higher than the 10% mutation prevalence estimated for Ashkenazi Jewish women with breast cancer. An additional 9% of women carry variants likely to disrupt gene function and dozens of VUS and novel variants are found in these women. Further analysis of samples from the remaining 942 women using genetic sequencing will help further elucidate the role of genetic risk factors in women of Mexican ancestry with breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-07-05.

Parallel Simulation of Population Balance Model-Based Particulate Processes Using Multicore CPUs and GPUs

Computer-aided modeling and simulation are a crucial step in developing, integrating, and optimizing unit operations and subsequently the entire processes in the chemical/pharmaceutical industry. This study details two methods of reducing the computational time to solve complex process models, namely, the population balance model which given the source terms can be very computationally intensive. Population balance models are also widely used to describe the time evolutions and distributions of many particulate processes, and its efficient and quick simulation would be very beneficial. The first method illustrates utilization of MATLAB's Parallel Computing Toolbox (PCT) and the second method makes use of another toolbox, JACKET, to speed up computations on the CPU and GPU, respectively. Results indicate significant reduction in computational time for the same accuracy using multicore CPUs. Many-core platforms such as GPUs are also promising towards computational time reduction for larger problems despite the limitations of lower clock speed and device memory. This lends credence to the use of highfidelity models (in place of reduced order models) for control and optimization of particulate processes.

A combined experimental and modeling approach to study the effects of high-shear wet granulation process parameters on granule characteristics

The purpose of the current work is to study the effects of high-shear wet granulation process parameters on granule characteristics using both experimental and modeling techniques. A full factorial design of experiments was conducted on three process parameters: water amount, impeller speed and wet massing time. Statistical analysis showed that the water amount has the largest impact on the granule characteristics, and that the effect of other process variables was more pronounced at higher water amount. At high water amounts, an increase in impeller speed and/or wet massing time showed a decrease in granule porosity and compactability. A strong correlation between granule porosity and compactability was observed. A three-dimensional population balance model which considers agglomeration and consolidation was employed to model the granulation process. The model was calibrated using the particle size distribution from an experimental batch to ensure a good match between the simulated and experimental particle size distribution. The particle size distribution of three other batches were predicted, each of which was manufactured under different process parameters (water amount, impeller speed and wet massing time). The model was able to capture and predict successfully the shifts in granule particle size distribution with changes in these process parameters.

Isolation, speciation, and antibiogram of clinically relevant non-diphtherial Corynebacteria (Diphtheroids)

PURPOSE

Coryneform or the non-diphtherial Corynebacterium species largely remains a neglected group with the traditional consideration of these organisms as contaminants. This concept, however, is slowly changing in the light of recent observations. This study has been done to find out the species distribution and antibiogram of various members of the clinically relevant Coryneform group, isolated from various clinical materials.

MATERIALS AND METHODS

One hundred and fourteen non-duplicate isolates of diphtheroids from various clinical isolates were selected for the study. The isolates were identified to the species level by using a battery of tests; and antimicrobial susceptibility was tested by using a combination of Clinical and Laboratory Standards Institute (CLSI) and the British Society for Antimicrobial Chemotherapy (BSAC) guidelines, in the absence of definitive CLSI guidelines.

RESULTS

Corynebacterium amycolatum was the predominant species (35.9%) in our series followed by the CDC Group G organisms (15.7%). Each of the remaining 19 species comprised of less than 10% of the isolates. More than half the total isolates were resistant to the penicillins, erythromycin, and clindamycin; while excellent activity (all the strains being susceptible) was shown by vancomycin, linezolid, and tigecycline. Chloramphenicol and tetracycline also had good activity in inhibiting more than 80% of the isolates. Multiply drug resistance was exhibited by all the species.

CONCLUSION

This study was an attempt to establish the clinical significance of coryneform organisms. The high level of resistance shown by this group to some of the common antibacterial agents highlights the importance of processing these isolates in select conditions to guide the clinicians towards an appropriate therapy.

Isolation of Legionella pneumophila from clinical & environmental sources in a tertiary care hospital

BACKGROUND & OBJECTIVES

Legionella pneumophila and other members of this genus are important respiratory pathogens but legionellosis often remains a neglected and under reported condition. Hence, this study was done to find out the presence of this organism in patients admitted to a tertiary care hospital with community-acquired pneumonia (CAP).

METHODS

A total of 470 lower respiratory tract samples and 24 water samples from hospital outlets were examined. Culture was done on buffered charcoal yeast extract agar with supplements and identification of the isolates was done by microscopy and biochemical tests.

RESULTS

L. pneumophila could be isolated from 12 (2.55%) patients suffering from community-acquired lower respiratory tract infection, unassociated with other aetiological agents of bacterial pneumonia. Of the 24 water samples tested, 8 (33.3%) grew the same organism.

INTERPRETATION & CONCLUSION

Our study has shown that Legionella is present in the hospital environment and was the aetiological agent of lower respiratory tract infection in 2.55 per cent of patients. A larger study and reports from other parts of the country may help in determining the true significance of legionellosis in India.