Opportunistic endophytism of Trichoderma species in rice Pusa Basmati-1 (PB1)

Microbes that colonize internal tissues of plants are called endophytes, andare known for their functional role against biotic/abiotic stress and growth promotion activity in plants. The ascomyceteous fungus Trichoderma spp. (Teleomorph: Hypocrea) are well known antagonists cum biocontrol agents. In this study, a total of five Trichoderma isolates from two different species viz., T. asperellum (TaR1, TaR2 and TaR3) and T. asperelloides (TaR4 and TaR5) collected from different agro-climatic zones in Rajasthan, India were evaluated for their endophytism in rice variety Pusa Basmati-1 (PB-1) through soil and seed treatment. An attempt was made to re-isolate the fungus from rice roots (seed and soil treated) and further subjected to microscopic and molecular analysis. Re-isolation results revealed that culture growth of Trichoderma spp. isolated was similar to that of the inoculated ones. The microscopic analysis (light and scanning electron microscopy) results also confirmed that the re-isolated endophytic fungus were identical to the inoculated ones. These results were further confirmed by polymerase chain reaction (PCR) amplification of the rDNA region (18SrRNA, ITS1, 5.8SrRNA, ITS2 and 28SrRNA) and translation elongation factor 1 (Tef1) with the re-isolated Trichoderma asperellum and T. asperelloides isolates. In this study, it has been confirmed that Trichoderma asperellum and T. asperelloides turns endophytic in rice after introduction through seed and soil treatment.

Pathogenicity, antibiotic susceptibility and genetic similarity of environmental and clinical isolates of Vibrio cholerae.

Isolates of Vibrio cholerae were obtained from clinical and environmental samples and the pathogenicity of these isolates was confirmed by hemolytic assay. The clinical isolates were more pathogenic than environmental isolates. Antibiotic susceptibility of V. cholerae to a set of antibiotics showed a marked variation. The environmental isolates exhibited more resistance to the antibiotics than clinical isolates. The plasmid curing technique was used to check the encoding of antibiotic resistance gene in genome. In both isolates, the resistance to vancomycin and co-trimaxazole was not mediated by plasmid and it may probably be encoded in genome. RAPD method was adopted to find out the variation in the genome of the clinical isolates and environmental isolates of V. cholerae. The genomic similarity pattern revealed that the environmental Ogawa isolates were closely related to clinical Ogawa isolates. This study confirmed the existence of the complex nature of V. cholerae in its pathogenicity, response to a set of antibiotics and genetic similarity.

Antimicrobial activity of Coleus aromaticus (benth) against microbes of reproductive tract infections among women

Coleus aromaticus (Benth) is a commonly available medicinal herb in India. The antimicrobial activity of this herb is tested as a cure for reproductive tract infections (RTI) among women. Fresh leaf has been used as a disc in different diameters to test the antimicrobial activity; against RTI causing microbes. Candida krusei showed the highest zone of inhibition of growth; followed by Candida albicans; Proteus mirablis; Escherichia coli; Staphylococcus aureus ; Enterococcus faecalis ; Klebsiella pneumoniae and the least inhibition was observed for Neisseria gonohorreae. Coleus aromaticus exhibits an effective antifungal and marked antibacterial activity. Using the leaf as a disc seems to be a novel and easy method that can be used initially to access the antimicrobial activity of a herb; before proceeding for further studies. This herb seems to be an ideal choice to treat RTI infections among women

Bacteremia due to beta haemolytic streptococci.

The Beta haemloytic streptococci (BHS) are well recognised human pathogens causing a variety of infections, including septicemia. It is important to ensure their isolation from clinical specimens by using optimum media. Moreover, since the different groups have different pathogenic potential, it is equally important to routinely serogroup them; this is emphasized here. Since, BHS are uniformly will greatly decrease morbidity and mortality due to BHS infection.

The spectrum of antimicrobial resistance among methicillin resistant Staphylococcus aureus (MRSA) in a tertiary care centre in India.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen globally, including India. Staph. aureus strains isolated from pus or blood of patients during January 1993 to November 1994 were tested for antimicrobial susceptibility using Kirby-Bauer disc diffusion technique. Among 1382 isolates of Staph. aureus, 332 (24%) were MRSA. Among the latter, 97 per cent were resistant to trimethoprim-sulphamethoxazole; 85.5 per cent to gentamicin and 45 per cent to amikacin. While over 90 per cent were resistant to norfloxacin and ciprofloxacin, only 53 per cent were resistant to ofloxacin. Fifty seven per cent were susceptible to rifampicin and 87 per cent to netilmicin. All tested strains were susceptible to vancomycin. Therefore, when antimicrobials other than vancomycin are considered for therapy, their choice requires the results of in vitro susceptibility testing of every isolate of MRSA.

Long-term preservation of streptococci.

Strains of 12 T types of group A streptococci preserved by sand desiccation and stored at 4 degrees to 10 degrees C were regularly sub-cultured to check their viability. For this, streptococci coated onto sand particles mixed with sterile sheep blood were inoculated into Todd-Hewitt broth with added blood and incubated for 24 to 48 h. Checking for viability every six months showed that group A streptococci could be preserved by this method for 21 yr. Our study shows that sand desiccation is a convenient and cheap method for the long-term preservation of streptococci in laboratories where other methods of preservation are not feasible on a regular basis.

Biting behaviour of Armigeres subalbatus (Coquillett) with reference to host selection and landing.

Armigeres subalbatus (Coquillett), a vicious crepuscular biter, has been selected to study the biting behaviour with reference to factors affecting landing and host selection in the laboratory. The mosquito showed a higher attractancy to relatively warmer skin of human hands. There was also a significant attraction towards the artificially warmed hands than the normal ones, and the mosquitoes avoided the artificially cooled hands. Therefore, host temperature is a factor which influences the attraction and subsequent landings of A. subalbatus. When the mosquitoes were offered animal hosts, the order of host preference by these mosquitoes was hen > rabbit > guinea pig, both in single and two-host combinations thus, showing their preference to avian host.

Circadian rhythm in the biting behaviour of a mosquito Armigeres subalbatus (Coquillett).

The crepuscular biting rhythm of A. subalbatus has been found to be a genuine circadian rhythm. When the entrained biting rhythm is allowed to freerun in constant darkness (DD) and continuous illumination (LL), it persists in DD (tau = 24.36 hr) and also in LL of ca. 0.1 1x (tau-23.82 hr) thus deviating from the strict 24 hr periodicity of the geophysical day. The biting rhythm becomes arrhythmic in LL of 1.0, 10, 0.4, 4, 40 lx even the first cycle damping away.

False resistance of salmonellae to trimethoprim-sulphamethoxazole in disc diffusion method.

Apparent resistance to trimethoprim-sulphamethoxazole (TMP-SMZ) in disc diffusion method was found in 14 strains of Salmonella typhi and 2 strains of S. paratyphi A grown on Mueller Hinton agar (MHA) of one manufacturer. On MHA from another manufacturer and on diagnostic sensitivity test agar (DSTA), these 16 strains were sensitive to TMP-SMZ. The minimum inhibitory concentration of trimethoprim (TMP) assayed by agar dilution method, on DSTA medium for these 16 strains was in the range of 0.01 to 0.04 micrograms/ml. Thus, the apparent resistance was a spurious result due to the unsatisfactory quality of the batch of MHA of the first manufacturer. Presumably the medium contained thymine or its derivatives which act as antagonists to TMP and sulphonamide drugs.