Delhi Strain Research Articles

Nosocomial infections as one of the most important problems of healthcare system.

Healthcare-associated infections (HAI) are commonly defined as adverse events resulting from the provision of healthcare. The reduction of risk arising from the spread of pathogenic microorganisms in the hospital environment is a considerable challenge in the context of the proper functioning of the medical services sector. The financial costs of hospitals resulting from HAI are a serious problem for the Polish healthcare system. The spread of strains with a high level of drug resistance in individual hospitals is associated with the local epidemiological situation. In 2015-2017, there was a high increase in the number of infections caused by New Delhi strains. The highest increase due to this strain occurred in Mazowieckie and Podlasie provinces. The dynamics of infection caused by New Delhi strains throughout Poland in 2015-2016 indicated an increase of 278.7%. In 2017, the phenomenon of antibiotic abuse in all regions of Poland was 24% higher than the EU average. One of the reasons is the insufficient number of diagnostic tests ordered by both general practitioners and doctors representing hospital care. In 2016-2017, the average number of microbiological tests in diagnosing hospital infections performed annually within the entire territory of Poland was 50% lower than in European Union countries and the number recommended by WHO. Increased, and at the same time inappropriate antibiotic therapy led to a build-upof drug resistance among bacterial species of significant clinical importance. The current epidemiological situation imposes the necessity for constant HAI control and broadly understood rationalization of the guidelines of hospital antibiotic policy.

Molecular analysis of mitochondrial cytochrome oxidase I gene of Aedes aegypti L. mosquitoes

Abstract Aedes aegypti is the most important arboviral vector worldwide. Recent studies reported that genetic variations and gene flow among same mosquito species is responsible for different disease transmission rate. Hence, to understand the relationship between genetic diversity and disease transmission potential, study on genetic variations among mosquito populations is essential. The aim of present study was to investigate the genetic variations of Ae. aegypti targeting COI gene from nine villages of Jalna District, Maharashtra and three laboratory strains originated from Aurangabad, Delhi and transgenic OX513A strain imported from OXITEC, UK. OX513A strain consists of a self-limiting dominant lethal gene construct intended for its use in suppression of Ae. aegypti population by sustained male adult releases in the environment. Mosquito eggs from field and laboratory strains were reared to adults and identified on the basis of morphological characteristics followed by COI gene sequence. Result of MSA and haplotype analysis revealed low genetic variations among field samples and Aurangabad strain, belonged to two haplotypes (H1 and H2) except Ramkheda village represented by separate haplotype H3. Other laboratory DEL strain and transgenic OX513A have great genetic variability to all isolates and have a separate haplotypes H4 and H5. Similar results were observed in phylogenetic analysis. Our observation of phylogenies revealed close relationship among the DEL and transgenic strain OX513A with few Indian and worldwide isolates. The information on genetic variability of mosquito population could help to understand and design the strategies for risk mitigation and effective implementation of new vector control tools like genetically modified mosquitoes.

Molecular and phylogenetic analysis of Chikungunya virus in Central India during 2016 and 2017 outbreaks reveal high similarity with recent New Delhi and Bangladesh strains

Central India witnessed Chikungunya virus (CHIKV) outbreaks in 2016 and 2017. The present report is a hospital based cross-sectional study on the serological and molecular epidemiology of the outbreak. Mutational and phylogenetic analysis was conducted to ascertain the genetic relatedness of the central Indian strains with other Indian and global strains. Chikungunya infection was confirmed in the clinically suspected patients by the detection of anti-CHIKV IgM antibody by ELISA and viral RNA by RT-PCR. A representative set of the RT-PCR positive samples were sequenced for E1 gene and analyzed to identify the emerging mutations and establish their phylogenetic relationship, particularly with other contemporary strains. Phylogenetic analysis revealed the present strains to be of East Central South African (ECSA) genotype. Emergence of a variant strain was observed in the year 2016, which became the predominant strain in this region in 2017. The strains showed significant identity with recent New Delhi strains of 2015 and 2016 and Bangladesh strains of 2017. The epidemic mutation A226V which emerged in 2006 outbreaks of India and Indian Ocean Islands was found to be absent in the current strains. Among the important mutations viz. K211E, M269 V, D284E, I317V & V322A observed in the recent strains. I317V is a novel mutation which has emerged very recently as it was found only in central Indian (2016, 2017), New Delhi strains (2015, 2016) and Bangladesh strains (2017). This study has identified a unique mutation E1:I317V in the Central Indian strains, which is present only in recent New Delhi and Bangladesh strains till date. This study highlights the need for continuous molecular surveillance of circulating CHIKV strains in order to facilitate the prompt identification of novel strains of this virus and enable the elucidation of their clinical correlates.

The Use of Liquids Ionic Fluids as Pharmaceutically Active Substances Helpful in Combating Nosocomial Infections Induced by Klebsiella Pneumoniae New Delhi Strain, Acinetobacter Baumannii and Enterococcus Species.

This review deals with various microbiological activities of ionic liquids, which constitute the first anti-infective defense against multi-drug-resistant bacteria—with a particular emphasis placed on medicine and pharmacology. The quoted data on the biological activity of ionic liquids including their antimicrobial properties (depending on the type of a cation or an anion) and are discussed in view of possible applications in nosocomial infections. Dedicated attention is given to finding infections with the Klebsiella pneumoniae New Delhi strain, Acinetobacter baumannii, and Enterococcus species, which are responsible for the induction of antibiotic resistance in intensive care units. Diagnosis and treatment using current antibiotics is a significant problem in hospital care, and the relevant burden on the health systems of the European Union member states induces the search for new, effective methods of treatment. Ionic liquids, due to their antibacterial effect, can be considered topical and general medications and may provide the basis for treatment to eliminate the antibiotic resistance phenomenon in the future. At present, the number of infections with resistant pathogens in hospitals and outpatient clinics in the European Union is growing. In 2015–2017, a significant incidence of respiratory and bloodstream infections with bacteria resistant to antibiotics from the 3rd generation group of cephalosporins, glycopeptides, and carbapenems were observed. The paper presents examples of synthesized bifunctional salts with at least one pharmaceutically active ion in obtaining a controlled release, controlled delivery, and biological impact on the pathogenic bacteria, viruses and fungi. The ionic liquids obtained in the presented way may find applications in the treatment of wounds and infections.

Self-Limiting OX513A Aedes aegypti Demonstrate Full Susceptibility to Currently Used Insecticidal Chemistries as Compared to Indian Wild-Type Aedes aegypti

OX513A Aedes aegypti is a genetically engineered strain carrying a self-limiting gene. Studies in several countries have shown the effectiveness of the strain at reducing pest Aedes aegypti populations. As a component of biosafety assessments relevant to Indian environments, OX513A and two Indian wild-type Ae. aegypti strains (from Aurangabad and Delhi) were tested for susceptibility to a range of commonly used insecticides in India, such as dichlorodiphenyltrichloroethane (DDT), malathion, deltamethrin, and permethrin using World Health Organization (WHO) testing kits and following WHO standard test procedures. Knockdown times (KDT) for all compounds were determined separately for male and female adults of the three mosquito strains. Results indicated that adults of OX513A, Aurangabad, and Delhi strains were resistant to DDT, yielding mortality rates of 90.9, 87.4, and 44.4% and 70.1, 3.0, and 6.0% for male and female adults, respectively. In contrast, adults of all three strains were found to be susceptible to malathion, deltamethrin, and permethrin, exhibiting mortalities between 98 and 100%. The magnitudes of susceptibility, based on the KDT50 values, were greater in the OX513A strain, as compared to wild-type strains of Ae. aegypti for all insecticides tested. The results confirm that, aside from historical resistance to DDT, OX513A has retained full sensitivity to these commonly used compounds and exhibits responses akin to those of susceptible Indian wild-type strains.

Characterization of Vibrio cholerae O1 strains that trace the origin of Haitian-like genetic traits

Vibrio cholerae O1 is the etiological agent of the severe diarrheal disease cholera. The bacterium has recently been causing outbreaks in Haiti with catastrophic effects. Numerous mutations have been reported in V. cholerae O1 strains associated with the Haitian outbreak. These mutations encompass among other the genes encoding virulence factors such as the pilin subunit of the toxin-co-regulated pilus (tcpA), cholera toxin B subunit (ctxB), repeat in toxins (rtxA), and other genes such as the quinolone resistance-determining region (QRDR) of gyrase A (gyrA), rstB of RS element along with the alteration in the number of repeat sequences at the promoter region of ctxAB. Given the numerous genetic changes in those Haitian isolates, we decided to investigate the possible origins of those variations in the Indian subcontinent. Thus, we determined the genetic traits among V. cholerae O1 strains in Delhi, India. A total of 175 strains isolated from cholera patients during 2004 to 2012 were analysed in the present study. Our results showed that all the tested strains carried Haitian type tcpA (tcpACIRS) and variant gyrA indicating their first appearance before 2004 in Delhi. The Haitian variant rtxA and ctxB7 were first detected in Delhi during 2004 and 2006, respectively. Interestingly, not a single strain with the combination of El Tor rtxA and ctxB7 was detected in this study. The Delhi strains carried four heptad repeats (TTTTGAT) in the CT promoter region whereas Haitian strains carried 5 such repeats. Delhi strains did not have any deletion mutations in the rstB like Haitian strains. Overall, our study demonstrates the sequential accumulation of Haitian-like genetic traits among V. cholerae O1 strains in Delhi at different time points prior to the Haitian cholera outbreak.

Laboratory and Molecular Characterization of Dengue Viruses in a 2014 Outbreak in Guangfo Region, Southern China.

Non-specific symptoms and low viremia levels make early diagnosis of dengue virus (DENV) infection challenging. This study aimed to i) identify laboratory markers that can be used to predict a DENV-positive diagnosis and ii) perform a molecular characterization of DENVs from the 2014 Guangdong epidemic. This retrospective study analyzed 1,044 patients from the Guangdong epidemic who were clinically suspected cases of dengue. Viral RNA was detected by real-time RT-PCR, and viral-specific NS1 antigen was detected using enzyme-linked immuno sorbent assay. A molecular phylogenetic analysis was performed for the with the DENV C-prM gene junction. Patients with dengue infection had leukopenia (2.8 × 109/L), thrombocytopenia (109.0 × 109/L), elevated aspartate aminotransferase (56.0 IU/L) and alanine aminotransferase (43.5 IU/L), and prolonged activated partial thromboplastin time (APTT, 33.5 s) (all P ＜ 0.001) compared to patients without dengue. The positive predictive value of leukopenia and thrombocytopenia for DENV infection were 96.9% and 93.0%, respectively. Leukopenia, thrombocytopenia, elevated aminotransferases, and prolonged APTT were useful predictive markers for an early diagnosis of DENV infection. Phylogenetic analysis indicated that the DENVs from the 2014 epidemic were closely related to a 2010 New Delhi strain and a 2013 Guangzhou strain. The 2014 epidemic consisted of co-circulating DENV-1 genotypes I and V from multiple origins. Efficient dengue surveillance can facilitate rapid response to future outbreaks.

Ecological variation and resistance levels to propoxur and chlorpyrifos in Anopheles stephensi (Diptera: Culicidae), a malaria mosquito from India

A total of 39 strains ofAnopheles stephensi, an important urban malaria vector, were collected from various parts of India and maintained in the insectary for this study. Based on the egg-float ridge number, 19 strains were classified into ecological variants and 32 strains were exposed to chlorpyrifos and propoxur to investigate their resistance status. Filter paper containing freshly laid eggs was taken, the ridge numbers on the floats were counted under the microscope, and strains were classified into ecological variants. Of the 19 strains, 18 were of ‘type form’, with ridge numbers ranging from 15 to 21. The Papareddipalya (PRP) strain belonged to the ‘intermediate form’, with 14 to 17 ridge numbers. Larval bioassays were carried out according to the procedure of the WHO. For chlorpyrifos, the lowest LC50value was 0.00107 mg/l (Padmanabhanagar strain) and the highest value was 0.0403 mg/l (GOA-A strain). Furthermore, the lowest LC90value was 0.00368 mg/l (Delhi strain) and the highest was 0.1746 mg/l (GOA-A strain). For propoxur, the lowest LC50value was 0.00029 mg/l (Goraguntepalya strain) and the highest value was 0.0037 mg/l (JP Nagar strain). Moreover, the lowest LC90value was 0.00094 mg/l (Goraguntepalya strain) and the highest value was 0.0115 mg/l (JP Nagar strain). The tolerance values ranged from 1.26 to 37.68 for chlorpyrifos and from 1.34 to 12.77 for propoxur. All the type forms were from urban and semi-urban locations, and the intermediate strain was from a semi-urban location. The bioassay results indicated that the strains ofAn. stephensiwere more susceptible to propoxur than to chlorpyrifos.

Nucleotide polymorphism and modulation of carboxyl esterase activity inSpodoptera litura(F.) (Noctuidae: Lepidoptera)

Tobacco caterpillar, Spodoptera litura (F.) is one of the lepidopteran pests which has developed resistance to organophosphate and synthetic pyrethroid insecticides. Development of resistance is mainly underlined by elevated level of carboxylesterase (CarE). In this study, S. litura strains obtained from cauliflower growing region were examined for enzyme, CarE level. Elevated level of CarE was observed in Sonepat strain (28.09 ± 0.09 μmol/min) followed by Delhi (26.72 ± 0.04 μmol/min) and Varanasi strain (10.00 ± 0.44 μmol/min). The gene encoding CarE enzyme was partially characterized (497bp). Sequence data revealed polymorphism at nucleotide level and gene was identical in all the three strains and similar to that of other species such as S. exigua as well as S. littoralis. Polymorphism at the nucleotide level could be attributed to differential activity of CarE.

Clinical, serological, microbiological, and outcome study of 200 cases of short duration fever without prior exposure to antibiotic

Background : Short duration fever is a very common presenting symptom of infections which are mostly self-limiting and do not require any antibiotics. Most of these patients presenting to primary care centers are exhibited antibiotics irrationally without any investigation results. Antibiotics are not a panacea for all fevers. This title was chosen to discourage the usual practice of indiscriminate use of antibiotics in short duration self-limiting fevers, increasing emergence of antibiotic resistance bacteria. This study was conceived and designed after The Lancet in 2010 reported the emergence of resistant New Delhi strain of metallo-beta-lactamase 1 Gram-negative Enterobacteriaceae from India, Pakistan, and the UK due to irrational use of antibiotics. Moreover, there are very scanty literature reports on Short duration Fevers. This study is likely to advocate rational scientific approach to the management of short duration fever. Objectives: This study was conducted to (a) arrive at a definite diagnosis and formulate various etiologies of short duration fever in this tertiary care hospital, (b) rational use of specific antibodies when indicated, and (c) study the outcome of therapy. Materials and Methods: This was an observational cross-sectional study comprising 200 fresh consecutive inpatients of fever of <2 weeks duration who has not been exposed to any antibiotic prior to hospitalization between July 2012 and September 2014. They were subjected to clinical, microbiological, and serological studies and other specific studies when indicated. Results: Common etiology for fever was found to be nonspecific viral fever (45%), which did not need antibiotics, then dengue fever (26.5%), enteric fever (7%), and malaria with Plasmodium vivax (4%) predominance. Conclusion: Clinicians needs to restrict to indiscriminate use of antibiotics in any febrile patients to prevent the emergence of antibiotic resistance. More number of similar studies need to be carried out globally to create awareness among clinician regarding the cautious and rational use of antibiotic therapy in short febrile patients.

Overexpression of Cytochrome P450 CYP6B7 Mediated Pyrethroid Resistance in Indian Strains of the Cotton Bollworm, Helicoverpa Armigera (Hübner)

Abstract The role of cytochrome P450 monooxygenase in pyrethroid resistance was studied in different strains of the cotton bollworm, Helicoverpa armigera, from India. Filed collected strains of Nagpur and Delhi were compared to the laboratory reared population. The results showed a high resistance to deltamethrin, α-cypermethrin, and β-cyfluthrin. The results also showed that this resistance could be reduced by using piperonyl butoxide (PBO). The Nagpur and Delhi strains were found to have a 2.40 and 1.79 fold higher monooxygenase activity compared to a susceptible strain. A strong, positive correlation between monooxygenase activity and pyrethroid resistance was observed (r = 0.86 - 0.98). The relative expression of the housekeeping gene, EF-1α, and three P450 genes, was studied in the 5th instar larval midgut of the three strains. Out of the three P450 genes examined, expression of CYP6B7 mRNA was not detected in the midgut of the susceptible strain though it was highly expressed in the resistant strains. The midgut of the Nagpur strain had a 2.60 fold overexpression of CYP6B7 mRNA compared to the moderately resistant, Delhi strain. The mRNA of CYP4G8 and CYP6B2 were not overexpressed in either the Nagpur or Delhi strain. The results indicated that the elevated cytochrome P450 monooxygenase activity is associated with pyrethroid resistance in Indian strains of H. armigera, and CYP6B7 could be the P450 form responsible for pyrethroid resistance.

Characterization, Genetic Diversity, and Evolutionary Link of Cucumber mosaic virus Strain New Delhi from India

The genome of Cucumber mosaic virus New Delhi strain (CMV-ND) from India, obtained from tomato, was completely sequenced and compared with full genome sequences of 14 known CMV strains from subgroups I and II, for their genetic diversity. Sequence analysis suggests CMV-ND shares maximum sequence identity at the nucleotide level with a CMV strain from Taiwan. Among all 15 strains of CMV, the encoded protein 2b is least conserved, whereas the coat protein (CP) is most conserved. Sequence identity values and phylogram results indicate that CMV-ND belongs to subgroup I. Based on the recombination detection program result, it appears that CMV is prone to recombination, and different RNA components of CMV-ND have evolved differently. Recombinational analysis of all 15 CMV strains detected maximum recombination breakpoints in RNA2; CP showed the least recombination sites.

Pyrethroid synergists suppress esterase-mediated resistance in Indian strains of the cotton bollworm, Helicoverpa armigera (Hübner)

The role of esterase in pyrethroid resistance was studied in the final larval instar of different strains of the cotton bollworm, Helicoverpa armigera. The resistant strains viz., Nagpur strain and the Delhi strain were found to have elevated midgut esterase activity in comparison to the susceptible strain. Nagpur strain and Delhi strain have 2.24 and 1.73-fold higher esterase activity, respectively, than that of the susceptible strain. The Native PAGE displayed important differences in the midgut esterase isozyme pattern between the susceptible and the pyrethroid-resistant strains. Out of the 10 esterase isozyme observed, susceptible strain lacked three bands, E2, E6 and E10 that were found in the resistant strains. The potency of the synergists piperonyl butoxide (PBO) and dihydrodillapiole (DDA) as esterase inhibitor were also studied both in vitro and in vivo. The in vitro results clearly show that both PBO and DDA inhibited esterase activity in the two resistant strains, while there was almost no esterase inhibition in the homogenate of the susceptible strain. The in vivo inhibition studies (topical application of PBO and DDA followed by biochemical analysis) illustrated that PBO- and DDA-esterase binding is rather slow and non permanent process. Esterase inhibition did not occur immediately after the synergist treatment but at 4 and 8 h post treatment in case of PBO and DDA, respectively. Native PAGE revealed that the in vivo esterase inhibition caused by both PBO and DDA was due to the binding of the synergist with the E6 isozyme which was not present in the susceptible strain.

Pyrethroid resistance and esterase activity in three strains of the cotton bollworm, Helicoverpa armigera (Hübner)

Microplate assay technique for estimation of esterase activity in a single insect was used in combination with dose mortality bioassays to detect pyrethroid resistance in three strains of Helicoverpa armigera and to study the frequency of pyrethroid resistant individuals within the population of the same strain at two larval stages, third and fifth instar. The third and fifth instar larvae of the field strains i.e., Nagpur strain and Delhi strain that displayed high degree of resistance towards deltamethrin, had higher esterase activity compared to a susceptible laboratory strain. The frequency distribution of individuals with elevated esterase activity above 1.00 absorbance unit was correlated with the resistance level of the strains. The frequency of resistant individuals in the third instar larvae of Nagpur strain and Delhi strain were 29% and 23%, respectively compared to 4% in the susceptible strain. The resistant individuals in the resistant strains have markedly increased in the fifth instar larvae with a frequency distribution of 63% and 90% in Delhi strain and Nagpur strain, respectively, while only 14% of individuals was found to have elevated esterase activity in the susceptible strain. The results demonstrated the role of esterase in pyrethroid resistance in H. armigera. Microplate assay proved to be a rapid and reliable biochemical technique for monitoring of pyrethroid resistance in H. armigera.

Development of Candidate Rotavirus Vaccines Derived from Neonatal Strains in India

The need for a rotavirus vaccine in India is based on the enormous burden associated with the >100,000 deaths due to rotavirus diarrhea that occur annually among Indian children. Two rotavirus strains identified during nosocomial outbreaks of rotavirus infection in New Delhi and Bangalore, India, more than a decade ago are being developed as live oral vaccines. Infected newborns had no symptoms, shed virus for up to 2 weeks after infection, mounted a robust immune response, and demonstrated protection against severe rotavirus diarrhea after reinfection. The 2 strains are naturally occurring bovine-human reassortants. The New Delhi strain, 116E, is characterized as having a P[11],G9 genotype, and the Bangalore strain, I321, is characterized as having a P[11],G10 genotype. The strains have been prepared as pilot lots for clinical trials to be conducted in New Delhi. This unique project, which is developing a new rotavirus vaccine in India with the use of Indian strains, an Indian manufacturer, and an Indian clinical development program, aims to expedite introduction of rotavirus vaccines in India.

Molecular Analysis of Isoniazid-Resistant Mycobacterium tuberculosis Isolates from England and Wales Reveals the Phylogenetic Significance of the ahpC −46A Polymorphism

The present study investigated the prevalence and diagnostic potential of the most commonly reported mutations associated with isoniazid resistance, katG 315Thr, katG 315Asn, inhA -15T, inhA -8A, and the oxyR-ahpC intergenic region, in a population sample of 202 isoniazid-resistant Mycobacterium tuberculosis isolates and 176 randomly selected fully sensitive isolates from England and Wales identified by using a directed oligonucleotide array and limited DNA sequencing. The strains were recovered from patients originating from 29 countries; 41 isolates were multidrug resistant. Mutations affecting katG 315, the inhA promoter, and the oxyR-ahpC intergenic region were found in 62.7, 21.9, and 30% of 169 genotypically distinct isoniazid-resistant isolates, respectively, whereas they were found in 0, 0, and 8% of susceptible strains, respectively. The frequency of mutation at each locus was unrelated to the resistance profile or previous antituberculous drug therapy. The commonest mutation in the oxyR-ahpC intergenic region, ahpC -46A, was present in 23.7% of isoniazid-resistant isolates and 7.5% of susceptible isolates. This proved to be a phylogenetic marker for a subgroup of M. tuberculosis strains originating on the Indian subcontinent, which shared IS6110-based restriction fragment length polymorphism and spoligotype features with the Delhi strain and Central Asian strain CAS1; and this marker is strongly associated with isoniazid resistance and the katG 315Thr mutation. In total, 82.8% of unrelated isoniazid-resistant isolates could be identified by analysis of just two loci: katG 315 and the inhA promoter. Analysis of the oxyR-ahpC intergenic region, although phylogenetically interesting, does not contribute significantly to further identification of isoniazid-resistant isolates.

Partial loss of cytoplasmic incompatibility with age in males ofCulex fatigans

The cytoplasms of Paris and Delhi strains of Culex fatigans have been reported to be bi-directionally incompatible. However, in the present study it is shown that with increasing age males with Paris cytoplasm show an increasing degree of partial compatibility with Delhi females. A male history of previous mating seems a contributory effect in enhancing the degree of partial compatibility. The relevance of partial compatibility to genetic control of C. fatigans is discussed.

Host-parasite relations in cotton rat filariasis

Delhi and Carworth strains of white rats were exposed quantitatively to infection with Litomosoides carinii and their susceptibility compared. Liponyssus bacoti (= Ornithonyssus bacoti) mites of known (calculated) intensities of infection were used for transmission. The relation between the calculated exposure (= transmission intensity) and the number of adult worms recovered from each rat was established. Adults of both strains of white rat were much "poorer" hosts than cotton rats. All 24 Carworth white rats (100%) and 21/24 of Delhi white rats (87-5%) of differing ages and both sexes became infected. Carworth white rats were generally more susceptible. The susceptibility of newly born Carworth white rats was greatest and was similar to that of cotton rats. Young rats of the Delhi strain were more susceptible than older rats. This strongly suggests "age resistance". The degree of resistance may, however, differ in different species and strains of white rats and in individual rats of the same strain.

Cross-Resistance Shown by Aldrin-Resistant Seed Maggot Flies, Hylemya spp., to Other Cydodiene Insecticides and Related Materials1

Laboratory tests on adult seed maggots, Hylemya spp., resistant to aldrin (✕209 at LD50) established that cross-resistance occurs with other cyclodiene insecticides and some related materials. The levels of cross-resistance were heptachlor ✕214; heptachlor epoxide ✕174; dieldrin ✕120; endrin ✕9.6; Telodrin® (1,3,4,5,6,7,8,8-octachloro-1,3,3a,4,7,7a,-hexahydro4,7-methanoisobenzofuran) ✕ 7.9; lindane ✕5.5; and endosulfan ✕1.7. The slope of the regression lines for the resistant Delhi strain was lower than that obtained with the susceptible strain. This resulted because an average 10% of the population was susceptible.