Microbiological quality & incidence of organisms of public health importance in food & water in Ludhiana.

Bacteriological analysis of 713 samples of various types of foods and related articles and potable water samples from different places in Ludhiana, Punjab was carried out. The highest counts ranging from 2.5 x 10(6)-7.5 x 10(8) organisms/g were observed in raw vegetables and fruits, followed by 3 x 10(6)-9.8 x 10(7)/ml, 8.3 x 10(4)-8.9 x 10(7)/g and 1 x 10(3)-6.7 x 10(7)/g in fruit juice, milk and its products, and salty/non milk snacks respectively. Fresh chapati, dal, rice, cooked vegetables and karhi etc., showed no microbial contamination. However, samples of these articles from road side cafes gave counts up to 1 x 10(7) organism/g. The most probable number of coliforms and Escherichia coli/100 ml of water ranged from < 1 to > 1100. Although 1332 isolates of 16 types of organisms of public health significance were obtained those of proven enteropathogenicity were enterotoxigenic Esch. coli (55), Esch. coli O157 (3), enteropathogenic Esch. coli (1), enterotoxigenic Klebsiella (23), Streptococcus faecalis (152), Bacillus cereus (133), Staphylococcus aureus (125), Aeromonas spp (47), Salmonella spp (10), Shigella spp (4) and Yersinia enterocolitica (2). Poor quality of potable water and widespread occurrence of enteropathogens in food consumed by the common man in Ludhiana was evident.

ELISA for detection of heat stable enterotoxin producing Escherichia coli strains.

Among 557 strains of Esch. coli isolated from patients with acute diarrhoea, 392 (70.4%) isolates demonstrated ST production by ELISA. Predominant ST producing serogroups were 020 (45), 078 (40), 0128 (21), 061 (19), 0149 (9), 04, 055, 0106 and 0114 (8 each). The inhibition ELISA range was between 10.5 and 40.5 per cent. Visual difference between a negative and a positive ELISA test was distinct. A comparison of ELISA with classical suckling mouse assay for 100 strains showed 88 and 80 positive strains respectively for ST. ELISA proved a more specific, rapid and sensitive assay which may be useful for screening large number of isolates in epidemiological studies.

Seasonal fluctuations in the occurrence of enteroinvasive Escherichia coli diarrhoea.

Enteroinvasive Esch. coli (EIEC) was implicated in 2.1 per cent (57 out of 2661) diarrhoeal patients investigated at Ludhiana (Punjab). The predominant serogroups isolated were 028, 0147, 0124 and 0112. High prevalence of EIEC infection was noticed among infants (50.6%) followed by children up to 10 yr (19.3%). The peak incidence (24.5%) occurred during the hot and dry month of May as compared to 1.7 per cent in February. The disease incidence was positively correlated with mean minimum temperature and mean maximum temperature. All strains gave Sereny's test positive and were mostly susceptible to cephalothin, gentamicin, nalidixic acid, furazolidine and neomycin.

Phospholipase A production by isolates of Salmonella species.

The incidence of intra- and extra-cellular phospholipase-A production by Salmonella isolates from human, poultry and environmental material was investigated. Nearly 17 per cent (15/90) of the strains tested produced phospholipase A. Phospholipase production was encountered in S. typhi, S. paratyphi A, S. typhimurium, S. seftenberg, S. bareilly, S. weltevredeen, S. newport, S. adelaide, S. alachua and S. gallinarum. Maximum (10/15) phospholipase producers were isolated from the human material. Phospholipase positive human isolates exhibited a high incidence of simultaneous multiple drug resistance, enterotoxigenicity and cell surface hydrophobicity.

Bioecological factors & rotavirus diarrhoea.

Rotavirus was detected (using Rotalex) in 11.72 per cent (120 of 1024) children below 3 yr age with diarrhoea. None of the 25 healthy control children excreted rotavirus in their faeces. Group specific ELISA for 89 Rotalex positive samples revealed 30 subgroup I and 43 subgroup II whereas 10 were untypable. Rotavirus infection ranged from 2.8 to 22.20 per cent in different months. There was no correlation with mean minimum and maximum temperatures. However, the incidence showed a negative correlation (r = -0.645) with relative humidity. Children between the age of 10 to 12 months had the maximum incidence of rotavirus infection. Male patients were found to be more susceptible to infection than females (3.3:1).

Mechanism of action of aflatoxin B1.

The inhibitory effects of aflatoxin B1 were found to be related to the gram character in procaryotes, used in this study. Ethylene diamine tetra chloroacetic acid (0·05 % w/v) or Tween-80 (0·05 % v/v) addition accentuated the aflatoxin B1 growth inhibition in Salmonella typhi and Escherichia coli at different pH values. The inhibition of lipase production was only 5–20 % in Pseudomonas fluorescence ca. 25–48% in Staphylococcus aureus and Bacillus cereus at different aflatoxin B1 concentrations (4–16 μg/ml).However, inhibition of α-amylase induction was complete in Bacillus megaterium whereas the inhibition was partial in Pseudomonas fluorescence (27–40%) at 32 μg aflatoxin B1 concentration. An increase in leakage of cell contents and decreased inulin uptake were observed in toxin incubated sheep red blood cell suspension (1 %) with increased aflatoxin B1 concentration.