Susceptible German Cockroaches Research Articles

Differential microbial responses to antibiotic treatments by insecticide-resistant and susceptible cockroach strains (Blattella germanica L.)

The German cockroach (Blattella germanica L.) is a major urban pest worldwide and is known for its ability to resist insecticides. Past research has shown that gut bacteria in other insects can metabolize xenobiotics, allowing the host to develop resistance. The research presented here determined differences in gut microbial composition between insecticide-resistant and susceptible German cockroaches and compared microbiome changes with antibiotic treatment. Cockroaches received either control diet or diet plus kanamycin (KAN) to quantify shifts in microbial composition. Additionally, both resistant and susceptible strains were challenged with diets containing the insecticides abamectin and fipronil in the presence and absence of antibiotic. In both strains, KAN treatment reduced feeding, leading to higher doses of abamectin and fipronil being tolerated. However, LC50 resistance ratios between resistant and susceptible strains decreased by half with KAN treatment, suggesting gut bacteria mediate resistance. Next, whole guts were isolated, bacterial DNA extracted, and 16S MiSeq was performed. Unlike most bacterial taxa, Stenotrophomonas increased in abundance in only the kanamycin-treated resistant strain and was the most indicative genus in classifying between control and kanamycin-treated cockroach guts. These findings provide unique insights into how the gut microbiome responds to stress and disturbance, and important new insights into microbiome-mediated insecticide resistance.

Cytochrome P450 MA expression in insecticide-resistant German cockroaches (Dictyoptera: Blattellidae).

Cytochrome P450 monooxygenases are detoxification enzymes commonly involved in insecticide resistance by insects. Recently, an overexpressed form of this enzyme, P450 MA, was purified from an insecticide-resistant strain of German cockroach, Blattella germanica (L.), and polyclonal antisera (anti-P450 MA) was produced. To test hypotheses that the overexpressed condition of P450 MA has evolved in > 1 geographic location and that P450 MA might be involved in insecticide resistance to specific insecticides, investigations were conducted using 4 insecticide-resistant and 1 susceptible German cockroach strains. In western blots that used anti-P450 MA antiserum as a probe, substantial differences in expression of P450 MA were observed. Strains showing the highest P450 MA expression had both the highest tolerance to the organophosphate insecticide chlorpyrifos and cytochrome P450-mediated demethylation activity. Results support the hypothesis that cytochrome P450 MA is potentially overexpressed in insecticide-resistant populations on a global scale.

Sequences of cDNAs encoding calmodulin, and partial structures of calmodulin kinase, and a calcium channel of kdr-resistant and -susceptible German cockroaches, Blattella germanica

Complementary DNA sequences of genes encoding calmodulin, partial structures of calmodulin-dependent protein kinase II (CaM-kinase II) and an L-type-like calcium channel al subunit (IVS5-IVS6-EF hand region) were identified and compared between susceptible and kdr strains of German cockroach, Blattella germanica. For this purpose, polymerase chain reactions (PCR) were used to obtain their sequences using cDNA from poly(A)+RNA isolated from their heads and thoraces. No mutation differences were found in all three sequences of calcium-regulating proteins between susceptible and strain. Northern blot analysis, however, showed reduced expressions of CaM-kinase II mRNA in two kdr strains. Western blot analysis with an antibody preparation against CaM-kinase II on protein levels confirmed the above strain difference in the titer of this enzyme. In contrast, the levels of calmodulin as well as that of an L-type-like calcium channel gene expression were not different between susceptible and kdr strains.

Water relations of insecticide resistant and susceptible German cockroaches (dictyoptera: Blattellidae)

1. 1. Percentage total body water content (%TBW), cuticular permeability (CP), and rate of water loss were determined for insecticide resistant and susceptible strains of the German cockroach, Blatlella germanica (L.). 2. 2. Initial body mass ranged from means of95.52–122.72mg, for female insecticide susceptible (ACY strain) and resistant (Maple) strains, respectively. Initial body mass of males ranged from means of 58.36 mg for a resistant strain (109) to 65.18 mg for a susceptible strain (Black). There were no differences in initial mass of nymphs among strains. 3. 3. Mean % total body water (%TBW) ranged from 68.21 to 71.95 for adult males, 66.78–71.89 for adult females and 70.56–71.61 for nymphs. ACY strain adults had greater %TBW than the other strains. There were no differences in %TBW of nymphs among strains. 4. 4. Mean cuticular permeabiity was not affected by initial mass for any stage or strain and ranged from 11.34 to 32.69 μg/cm 2/hr/mmHg for nymphal and male susceptible strain (Black) B. germanica, respectively. 5. 5. Cumulative mass and %TBW lost increased linearly with desiccation time. 6. 6. Water relations of B. germanica are not related to levels of insecticide resistance.

A Comparision of Reproduction and Longevity in Pyrethroid-Resistant and Susceptible German Cockroach (Blattodea: Blattellidae) Field-Collected Strains

Life histories of five field-collected strains of the German cockroach, Blattella germanica, were studied. Three were highly resistant to pyrethrins and allethrin; two were susceptible. Life history parameters of the susceptible strains and one of the resistant strains were closely similar. Two of the three resistant strains differed from the susceptible strains and from the third resistant strain. Differences from the latter strains included a longer interval between hatch of successive egg cases, fewer viable (hatched) egg cases per female, a more uneven pattern of maturation among nymphs from individual oothecae (egg cases), fewer adult progeny per egg case, and lower total numbers of adult progeny per life span of females. No significant difference occurred between the two resistant strains in any of the foregoing characteristics.

Residual Efficacy of Chlorpyrifos and Diazinon Formulations for German Cockroaches (Orthoptera: Blattellidae) on Panels Placed in Commercial Food Preparation Areas2

Ceramic and stainless steel panels were treated with chlorpyrifos (Dursban LO or ME) or diazinon (Knox Out 2FM) and aged in a commercial kitchen. Type of surface (ceramic tile or stainless steel) did not significantly affect residual performance of formulations used for control of adult male German cockroaches, Blattella germanica (L.). Microencapsulation stabilized the residues of both chlorpyrifos and diazinon and caused 100% mortality of susceptible German cockroaches for 8 weeks and resistant cockroaches for 4 weeks. The emulsifiable formulation provided only 0–67% mortality after 1–2 weeks.

Properties and inhibition of acetylcholinesterase in resistant and susceptible German cockroaches ( Blattella germanica L.)

Acetylcholinesterase (AChE) from German cockroaches was partially characterized and examined for its possible involvement in resistance to organophosphate and carbamate insecticides in four resistant strains. Solubilized preparations from heads of susceptible cockroaches displayed optimal activity near pH 7.6, and activity increased linearly with increasing temperature up to 40°C. The kinetic parameters K m and V max, determined with acetylthiocholine iodide as substrate, were 1.03 × 10 −4 M and 537 nmol/(min mg protein), respectively, for the susceptible strain. Differential centrifugation of both solubilized and nonsolubilized head homogenates indicates that over 90% of AChE activity is membrane associated, but that homogenization in the presence of detergent increases solubility. These conclusions are supported by nondenaturing gel electrophoresis which suggests that mobility and resolution of different molecular forms was dependent on solubilization. The biomolecular rate constants, k i , in four stains of German cockroaches which display varying levels of organophosphate and carbamate resistance were similar to the susceptible strain for chlorpyrifos oxon, malaoxon, and propoxur, suggesting that insensitivity of AChE in German cockroaches is probably not a common factor conferring resistance to these compounds.

Comparative Susceptibility of North American Bluttellu (Orthoptera: Blattellidae) Species to Insecticides

Toxicities of six insecticides to susceptible and resistant German cockroach, Blattella germanica (L.), Asian cockroach, B. asahinai Mizukubo, and field cockroach, B. vaga Hebard were determined. Toxicity by chemical class was pyrethroid > carbamate = organophosphorus for each species. In surface contact and topical application ( µ g/insect) bioassays. the susceptible German cockroach strain was more tolerant than the Asian cockroach to diazinon, propoxur, fenvalerate, and cypermethrin. Both species were equally susceptible to bendiocarb residues and to chlorpyrifos that was applied topically. The Asian cockroach was more susceptible to all insecticides when LD50's were expressed as µ g/mg body weight. The susceptibility profile of the field cockroach was similar to that of the susceptible German cockroach strain except that the field cockroach was relatively tolerant of chlorpyrifos. High organophosphorus resistance (>14-fold in topical application tests) was observed in the resistant German cockroach strain; however, the degree of resistance was lower when estimated by the contact toxicity test. We conclude that insecticides that are used for control of the German cockroach will also control the Asian cockroach. Our data suggest that topical application assays are the most sensitive method for monitoring resistance in the German and Asian cockroach.

Interactions of DDT with the nervous system of the resistant and susceptible german cockroaches.

DDT is regarded as a nerve poison in insects and mammals chiefly from the symptomological, electrophysiological and biochemical points of view1,2. The actual mechanism of DDT poisoning at the target, however, is not known.