Isolation of Multi-Drug Resistant Potential Pathogenic Bacteria From Blow Fly Collected From Different Areas of Dhaka City

The research work was conducted for isolation and identification of potential pathogenic bacteria from blow fly (Calliphora spp.) and to investigate their antibiotic susceptibility. For this purpose, 20 blow flies were collected from 4 selected areas (Curzon Hall, Dhaka Medical College Hospital, Fruit Store and Fish Market) of Dhaka city. A total of 40 samples (20 from external surface and 20 from alimentary gut homogenates) were prepared from the blow flies. Among the total 20 flies, 3(15%) were collected from Curzon Hall and 5(12.5%) isolates were obtained from them; 6(30%) flies were collected from DMCH which had 11(27.5%) isolates; 5(25%) flies were collected from fruit stores and 10(25%) isolates were collected from there; 6(30%) flies were collected from fish market and 14(35%) isolates were collected from there. The isolated bacteria were presumptively identified as Escherichia coli, 12 (30%); Salmonella spp., 8 (20%); Shigella spp., 4(10%); Enterobacter spp., 3 (7.5%); Klebsiella spp., 2 (5%); Bacillus spp., 7 (17.5%) and Staphylococcus spp., 4 (10%) in number which were based on morphology as observed under microscope as well as cultural and biochemical properties. All of these isolates were resistant to various antibiotics. Bacterial susceptibility showed that E. coli isolates were highly resistant (66.6%) to Penicillin, Salmonella spp. mostly resistant (62.5%) to Penicillin and Tetracycline. Klebsiella spp. Isolates were 100% resistant to Penicillin and 100% sensitive to Ciprofloxacin, Imipenem and Tetracycline. In case of Shigella spp. and Enterobacter spp., 75% and 100% isolates were resistant to Penicillin respectively. Among the Staphylococcus spp. isolates, 75% were resistant to Ampicillin and Penicillin. In case of Bacillus spp. isolates, 57.2% were resistant to Penicillin and 100% sensitive to Imipenem. Antibiotic resistance of these species affect our human health also. This study demonstrated the potential of blow flies as a vector of various pathogenic microorganisms and a mode of transmission of antibiotic resistance. Bangladesh J. Zool. 49 (2): 205-214, 2021

Conditional knockdown of transformer in sheep blow fly suggests a role in repression of dosage compensation and potential for population suppression

The transformer (tra) gene is essential for female development in many insect species, including the Australian sheep blow fly, Lucilia cuprina. Sex-specific tra RNA splicing is controlled by Sex lethal (Sxl) in Drosophila melanogaster but is auto-regulated in L. cuprina. Sxl also represses X chromosome dosage compensation in female D. melanogaster. We have developed conditional Lctra RNAi knockdown strains using the tet-off system. Four strains did not produce females on diet without tetracycline and could potentially be used for genetic control of L. cuprina. In one strain, which showed both maternal and zygotic tTA expression, most XX transformed males died at the pupal stage. RNAseq and qRT-PCR analyses of mid-stage pupae showed increased expression of X-linked genes in XX individuals. These results suggest that Lctra promotes somatic sexual differentiation and inhibits X chromosome dosage compensation in female L. cuprina. However, XX flies homozygous for a loss-of-function Lctra knockin mutation were fully transformed and showed high pupal eclosion. Two of five X-linked genes examined showed a significant increase in mRNA levels in XX males. The stronger phenotype in the RNAi knockdown strain could indicate that maternal Lctra expression may be essential for initiation of dosage compensation suppression in female embryos.

Life cycle and development rate of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae) during monsoon season in South India: applications in estimation of postmortem interval

Hemipyrellia ligurriens, considered as one of the forensically important blow fly species, has a wide distribution in many countries including India. To conduct forensic entomological investigations involving deaths of livestock, human beings and wild animals, standard life cycle data should be prepared for the local blow fly species under various weather conditions. Reliable forensic entomological data specific to geographic locations in India are not available presently to assist the post mortem interval assessment. In this study, life cycle and the rate of development of H.ligurriens was determined during monsoon season in Kerala, South India. Survival rate observed from egg to adult emergence was 44.68 %. Total duration of development of the species from oviposition till adult emergence was 462.57 h. Growth curves based on the age, specific length parameter and time taken for development of each larval stage was constructed. This development model would be helpful for the medical, veterinary and law enforcement officials in forensic estimation of post mortem interval by analyzing the length parameters of larvae collected from decomposed dead bodies of humans, cadavers of wild animals and livestock.

Assemblages of Necrophagous Blow Flies (Diptera: Calliphoridae) in Four Contrasting Ecoregions of Los Angeles County, California, United States

An ecological study to evaluate necrophagous species richness, abundance, and diversity was conducted in four contrasting ecoregions of Los Angeles County, California, United States: a highly anthropized area, two moderately populated areas, and a sparsely populated area. Our hypothesis states that there will be higher abundance of exotic species in greatly anthropized ecoregions and higher diversity of native calliphorid flies in sparsely populated sites. A total of 2,883 blow flies belonging to 12 species were captured from the four ecoregions. The exotic Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) was the most abundant species, representing 72.84% of all Calliphoridae collected. The highest abundance was in the highly anthropized ecoregion. Differences of the blow fly assemblages across environmentally and anthropically different ecoregions were found, and that the relative abundance of the exotic species increased with anthropization. Our results suggest that both anthropization and elevation alter the structure of blow fly assemblages, modifying the abundance and species richness of Calliphoridae. The results of this study support the hypothesis of biotic homogenization, since we found a higher proportional abundance of exotic species and lower diversity of native blow flies in ecoregions heavily modified by human action. Additionally, the hypothesis of intermediate disturbance was supported as the highest diversity was found in the ecoregion with moderate anthropization mixed with natural elements. This is the first study to conduct an intensive survey of the Calliphoridae assemblages in Los Angeles County, which can be potentially used as a tool in human and veterinary health and forensic sciences.

Ultra structure of second instar larva of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae), a forensically important blow fly species from India

Ultra structural characters of second instar larvae of Hemipyrellia ligurriens are elucidated through micrographs (Scanning Electron Microscope). Morphological details of maxillary palpi, antennae, oral cirri, facial mask, labial lobe, spinulations, and papillae of anal segment are described. Oral cirri are ten in number, arranged bilaterally on each side of the functional mouth opening and gently curved medially. The labial lobes are distinctively demarcated with fleshy projections antero–ventrally and have a characteristic shape. Thoracic spines have a bulbous base, slender sharp tips and are directed backwards. Prominent dorsal and ventral anal papillae with projected tips and broad conical base were present surrounded by microtrichia. The ultrastructure details of H. ligurriens would help in the rapid and accurate identification of the species in forensic investigations and to estimate time since death in medico legal cases. This is the first report on the ultra-structural features of H. ligurriens.

Impact of Comingled Heterospecific Assemblages on Developmentally Based Estimates of the Post-Mortem Interval—A Study with Lucilia sericata (Meigen), Phormia regina (Meigen) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae)

Estimates of the minimum post-mortem interval (mPMI) using the development rate of blow flies (Diptera: Calliphoridae) are common in modern forensic entomology casework. These estimates are based on single species developing in the absence of heterospecific interactions. Yet, in real-world situations, it is not uncommon to have 2 or more blow fly species developing on a body. Species interactions have the potential to change the acceptance of resources as suitable for oviposition, the timing of oviposition, growth rate, size and development time of immature stages, as well as impacting the survival of immature stages to reach adult. This study measured larval development and growth rate of the blow flies Lucilia sericata (Meigen, 1826), Phormia regina (Meigen, 1826) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) over five constant temperatures (15, 20, 25, 30, 35 °C), in the presence of conspecifics or two-species heterospecific assemblages. Temperature and species treatment interacted such that L. sericata larvae gained mass more rapidly when in the presence of P. regina at 20 and 30 °C, however only developed faster at first instar. At later stages, the presence of P. regina slowed development of L. sericata immatures. Development time of C. vicina immatures was not affected by the presence of P. regina, however larvae gained mass more slowly. Development time of P. regina immatures was faster in the presence of either L. sericata or C. vicina until third instar, at which point, the presence of L. sericata was neutral whereas C. vicina negatively impacted development time. Phormia regina larvae gained mass more rapidly in the presence of L. sericata at 20 °C but were negatively impacted at 25 °C by the presence of either L. sericata or C. vicina. The results of this study indicate that metrics such as development time or larval mass used for estimating mPMI with blow flies are impacted by the presence of comingled heterospecific blow fly assemblages. As the effects of heterospecific assemblages are not uniformly positive or negative between stages, temperatures or species combinations, more research into these effects is vital. Until then, caution should be used when estimating mPMI in cases with multiple blow fly species interacting on a body.