Effect of temperature and search area on the functional response of Anisops sardea (Hemiptera: Notonectidae) against Anopheles stephensi in laboratory bioassay.

Present study was carried out to establish the influence of abiotic factors on foraging activities of a predatory hemipteran insect Anisops sardea against Anopheles stephensi larvae. The functional response of A. sardea was evaluated in variable density of prey items with variation in search area (100, 250, 500 and 1000ml water volume) and temperatures (20, 25 and 30°C). The results of laboratory bioassay revealed that prey consumption rate of predator species was positively related with increasing temperature and inversely related with increasing search area. Polynomial logistic regression equations and associated parameters showed that A. sardea exhibited a type II functional response in variable search area and type-III response at variable temperatures. Related response specific attack rates and handling times were also evaluated in presence of specific abiotic factors.

Functional response analysis of Anisops sardea (Hemiptera: Notonectidae) against Culex quinquefasciatus in laboratory condition.

BACKGROUND & OBJECTIVES: Culex quinquefasciatus is the principal vector of lymphatic filariasis (LF). Application of alternative vector control methodologies are aimed at reduction of mosquito breeding sites and biting activity through the use of biological control methods. In the present study, functional response of aquatic Hemipteran backswimmer, Anisops sardea was assessed against Cx. quinquefasciatus larvae in laboratory bioassay. METHODS: The functional respons of A. sardea was assessed against III(rd) instar larvae of Cx. quinquefasciatus. Respective handling times and coefficient of attack rates were determined by a non linear polynomeal regression equation. RESULTS: The results of rates of predation in variable prey densities exhibited a 'linear rise to plateau curve', associated with 'Type -II' functional response. The logistic regression estimated a significant negative linear parameter (P(1) <0) which also supported the same observation. Associated 'attack rates' and 'handling times' were also calculated using the Holling Disc Equation. INTERPRETATION & CONCLUSIONS: The results of present experiments indicate that A. sardea can be used as a biocontrol agent against the larval forms of Cx. quinquefasciatus in temporarily available breeding places of mosquito with relatively clear water. However, a detailed field study has to be done to confirm these findings.

Potential antibacterial activity of berberine against multi drug resistant enterovirulent Escherichia coli isolated from yaks (Poephagus grunniens) with haemorrhagic diarrhoea.

OBJECTIVE: To evaluate the antimicrobial efficacy of berberine, a plant alkaloid. METHODS: Five multi-drug resistant (MDR) STEC/EPEC and five MDR ETEC isolates from yaks with haemorrhagic diarrhoea were selected for the study. Antibacterial activity of berberine was evaluated by broth dilution and disc diffusion methods. The binding kinetics of berberine to DNA and protein was also enumerated. RESULTS: For both categories of enterovirulent Escherichia coli (E. coli) isolates, berberine displayed the antibacterial effect in a dose dependent manner. The MIC(50) of berberine chloride for STEC/EPEC isolates varied from 2.07 µM to 3.6 µM with a mean of (2.95 ± 0.33) µM where as for ETEC strains it varied from 1.75 to 1.96 µM with a mean of (1.87 ± 0.03) µM. Berberine bind more tightly with double helix DNA with Bmax and Kd of (24.68±2.62) and (357.8±57.8), respectively. Berberine reacted with protein in comparatively loose manner with Bmax and Kd of (18.9±3.83) and (286.2±113.6), respectively. CONCLUSIONS: The results indicate clearly that berberine may serve as a good antibacterial against multi drug resistant E. coli.

Virulence repertoire of Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic Escherichia coli (ETEC) from diarrhoeic lambs of Arunachal Pradesh, India.

A total of 107 faecal samples were collected from diarrhoeic lambs of high altitude terrains (2,000 to 5,000 m above the mean sea level) of Tawang and West Kameng districts of Arunachal Pradesh, India. Total 234 Escherichia coli were isolated and further subjected to PCR for the study of virulence repertoire characteristics of Shiga toxin-producing E. coli (STEC) and enterotoxigenic E. coli (ETEC). Out of the 234 isolated E. coli, 32% were found positive for STEC, and 9% were carrying virulence gene for ETEC. The isolated STEC serogroups were O159, O127, O120, O113, O60, O30, O25, O8 and O2. Of all the 74 STEC strains, PCR showed that 18% isolates carried stx ( 1 ), 26% possessed stx ( 2 ) and 47% produced positive amplicon for both. Other virulent attributes like intimin (eaeA), enterohaemolysin (ehxA) and STEC auto-agglutinating adhesin (saa) were present in 18%, 43% and 44% of the isolates, respectively. The isolated ETEC serogroups were O172, O170, O159, O146, O127, O120, O113, O86, O75, O60, O30, O25, O8, O2, OR and OUT. Of the 22 ETEC-positive isolates, 23%, 18% and 4.5% possessed the gene only for LT, STa and STb, respectively, whereas 54% carried genes for both LT and STb. Some serogroups of E. coli like O159, O127, O120, O113, O60, O30, O25, O8 and O2 possessed genes for both Shiga toxin and enterotoxin. This study is the first report of ETEC isolation from diarrhoeic lambs in India. The moderately high proportion of STEC and ETEC in the diarrhoeic lambs implicated that these animals are important reservoir of STEC and ETEC. This is really a grave concern for the 'brokpas' and nomads (shepherds) who share a close relationship with this animals for their livelihood. This study also indicates that ETEC may be a major cause for frequent diarrhoeal episodes in lambs of this region.