Identification of an IV-dextrose solution as the source of an outbreak of Klebsiella pneumoniae sepsis in a newborn nursery.
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Biomedical subjects
Publications and source records attributed to M V Jesudason.
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The samples of plankton, soil sediment and water from a pond, a lake and a moat respectively in and around Vellore were studied for environmental vibrios. Vibrios were isolated from all these specimens after enrichment in alkaline peptone water and subculture on selective media. Non O1, non O139 Vibrio cholerae, Aeromonas spp. and Plesiomonas spp. were isolated. There were no isolates of V. cholerae serogroup O1 and O139. Representative strains of non O1 and non O139 V. cholerae from environmental sources were tested for toxin production in Chinese hamster ovary (CHO) and Vero cell monolayer in microtitre plates. Thirty-three (91.7%) of the 36 strains tested demonstrated cytopathic effect (CPE) in both cell lines indicating their toxigenicity. PCR done on representative strains of non O1 and non O139 V. cholerae showed that none of the strains were positive for ctx A, tcp A-E and tcp C genes. These results indicate that these non agglutinating environmental vibrios produced cytotoxins other than the cholera toxin.
The prevalence of Vibrio cholerae in drinking water, lakes and sewage outfalls during July and August 1996 in Vellore, India was determined. Drinking water samples were collected on single occasions from 12 sites in different geographic areas of the town where cholera had been reported. Samples of water, plankton and sediment were collected from fixed sites at three lakes on three occasions separated by at least 3 days during the course of the study. Samples from open sewers were taken from two representative sites in four areas of the town. Bacteria isolated from samples were identified by standard biochemical tests and isolated strains of V. cholerae tested for their ability to agglutinate O1 and O139 antisera. Water samples from lakes were also tested for the presence of V. cholerae O1 and O139 by fluorescent antibody staining. Non-O1, non-O139 strains of V. cholerae were detected in 41% of drinking water samples and 100% of water, sediment and plankton samples from the test lakes. Eighty-seven per cent of open sewers sampled contained viable non-O1, non-O139 V. cholerae. Fluorescent antibody staining gave positive results for V. cholerae O1 and O139 for all water samples from the three lake sites. Strains of Aeromonas spp. were isolated from 58% of drinking water samples and from 66% of sediment, 77% of plankton and 55% of water samples from lakes. All open sewers sampled contained Aeromonas spp. PCR amplification employing specific primers demonstrated that none of the non-agglutinating V. cholerae isolates contained the ctx operon. The non-O1, non-O139 V. cholerae isolates showed different patterns of antibiotic resistance to ampicillin, ciprofloxacin, chloramphenicol, tetracycline and trimethoprim.
A representative sample of 21 Salmonella typhi strains isolated from cultures of blood from patients at the Christian Medical College and Hospital, Vellore, India, were tested for their susceptibilities to various antimicrobial agents. Eleven of the S. typhi strains possessed resistance to chloramphenicol (256 mg/liter), trimethoprim (64 mg/liter), and amoxicillin (>128 mg/liter), while four of the isolates were resistant to each of these agents except for amoxicillin. Six of the isolates were completely sensitive to all of the antimicrobial agents tested. All the S. typhi isolates were susceptible to cephalosporin agents, gentamicin, amoxicillin plus clavulanic acid, and imipenem. The antibiotic resistance determinants in each S. typhi isolate were encoded by one of four plasmid types. Plasmid-mediated antibiotic resistance genes were identified with specific probes in hybridization experiments; the genes responsible for chloramphenicol, trimethoprim, and ampicillin resistance were chloramphenicol acetyltransferase type I, dihydrofolate reductase type VII, and TEM-1 beta-lactamase, respectively. Pulsed-field gel electrophoresis analysis of XbaI-generated genomic restriction fragments identified a single distinct profile (18 DNA fragments) for all of the resistant isolates. In comparison, six profiles, different from each other and from the resistance profile, were recognized among the sensitive isolates. It appears that a single strain containing a plasmid conferring multidrug-resistance has emerged within the S. typhi bacterial population in Vellore and has been able to adapt to and survive the challenge of antibiotics as they are introduced into clinical medicine.
In a developing country like ours where typhoid fever is endemic and there are very few microbiology laboratories to provide diagnosis by culture, a search for non culture techniques for rapid and reliable diagnosis continues. The Widal test has a low sensitivity. We have attempted to adapt the well established enzyme linked immunosorbent assay (ELISA) technique to provide a serological test of better sensitivity and specificity. The ELISA described here to detect anti-LPS antibodies was found to have a sensitivity of 89.4 per cent and a specificity of 94.9 per cent. The sensitivity for the antiflagellin ELISA was 68.1 per cent and specificity was 97.4 per cent. The likelihood ratio was 17.5 for anti-LPS ELISA and 26.2 for the anti-flagellin ELISA. Considering the positivity of either one ELISA as diagnostic, the sensitivity was 93.6 per cent and specificity was 94.9 per cent.
Until 1987 all isolates of V. cholerae 01 at a tertiary care hospital in south India were susceptible to drugs commonly used to treat gastroenteritis including cholera. Since July 1987 strains resistant to co-trimoxazole have been encountered and since October 1995 strains resistant to nalidixic acid are being isolated. In this study the latter strains were examined by determining minimum inhibitory concentration levels of nalidixic acid as well as norfloxacin, the fluoroquinolone extensively used to treat diarrhoea. No cross resistance to norfloxacin was found in any of the nalidixic acid resistant V. cholerae 01 strains.
Isolates of Staphylococcus aureus and coagulase negative staphylococci (CONS) from blood culture of bacteraemic patients were studied for methicillin resistance is 1993 and 1996. An increase in methicillin resistance among these isolates was observed in 1996. In 1993, 32.6 per cent isolates of S. aureus were methicillin resistant, this increased to 45.7 per cent in 1996. Methicillin resistance in CONS were 1.6 and 14.6 per cent respectively in 1993 and 1996. This increase in methicillin resistance may pose therapeutic problems and requires more effective drugs based on susceptibility testing of such isolates.
A commercial E test was compared with the standard agar dilution method for the determination of minimum inhibitory concentration (MIC) of penicillin, erythromycin, chloramphenicol and cefotaxime for 36 strains of Streptococcus pneumoniae from patients with invasive diseases. Additional strains were tested for MIC values for penicillin (6), erythromycin (14) and cefotaxime (13) for a better statistical evaluation. Besides, 5 reference standards with predetermined MIC values obtained from WHO pneumococcal reference center at Copenhagen, Denmark were tested for penicillin and erythromycin, for quality assessment using both agar dilution as well as E test methods. An overall agreement within +/- 2 dilutions was noted for 97 per cent of the strains tested for all the antimicrobials. A high degree of correlation was noted for erythromycin (r = 1), penicillin (r = 0.99), chloramphenicol (r = 0.95) and cefotaxime (r = 0.9). In MIC determination of a single antimicrobial for diagnostic purpose, E test was found to be more cost effective than conventional agar dilution method. E test was simple to perform, easy to interpret and a valid method for MIC determination of antimicrobials for S. pneumoniae in our center.
A multidrug resistant (MDR) variety of Salmonella typhi emerged as the cause of epidemic typhoid fever in some Asian countries including India, during the late 1980s. We faced the epidemic from April 1990 to the first quarter of 1993. However, during this period we continued to isolate chloramphenicol sensitive (CS) S. typhi also. The relative prevalences showed that the frequency of CS variety was unaffected by the epidemic of MDR variety. This is an unusual epidemiological pattern, which indicates that there may have been factors which favoured the epidemic of the MDR variety but not the CS one.
Twelve isolates of Salmonella typhi isolated in Vellore, India had reduced susceptibility to 4-quinolones (MIC of ciprofloxacin 0.256 mg/L). One isolate was isolated in 1992 but the remaining 11 were isolated in 1994. The section of the gyrA gene from codons 24 to 185, which includes the "Quinolone Resistance Determining Region", was amplified by the polymerase chain reaction and, after separating the amplified strands, the DNA was sequenced directly. In the one isolate from 1992, no alterations were seen in this region of gyrA, compared with the ciprofloxacin-sensitive isolates and presumably decreased 4-quinolone susceptibility resulted from reduced permeability of the cell outer membrane or another mechanism. In nine isolates from 1994, a substitution of phenylalanine for serine at position 83 of GyrA correlated with the decrease in 4-quinolone susceptibility. In the remaining two isolates, the novel substitution of aspartate to tyrosine at position 87 was found; in one isolate this substitution was coupled with another substitution at position 83 but in the other it was not.
The minimum inhibitory concentration (MIC) of ciprofloxacin has been determined in 193 strains of S. typhi isolated during January and July each year from March 1991 to July 1995. While all strains remained within established range of susceptibility, a clear trend of increase of MIC values with time was observed. During the first four study periods, all strains had MIC values below 0.031 microgram/ml; during the fifth and sixth, 3 strains had a higher value namely 0.125 microgram/ml. During the last four, 14 strains showed MIC values of 0.25 microgram/ml. Thus an increase in MIC of ciprofloxacin to S. typhi has been observed over the years.
There is a need for additional data on the distribution of pneumococcal serotypes in developing countries. We report the use of a coagglutination (COA) and a latex agglutination (LA) test for serotyping Streptococcus pneumoniae which were evaluated using 114 clinical isolates in Vellore, India. In tests to serotype 30 fresh isolates of pneumococci from meningitis (8 isolates), bacteraemia/septicaemia (21 isolates) and peritonitis (1 isolate) cases, there was complete concordance among the three methods. An additional 20 isolates (11 from cerebrospinal fluid and 9 from blood cultures) were serotyped using both LA and COA, with full agreement between the results. With a further 30 isolates, there was 93% concordance for the COA types with serotypes assigned by a WHO reference laboratory. The COA and LA serotyping results were equivalent in accuracy to those obtained using quellung serotyping. Both these agglutination tests are rapid, valid, and relatively cheap, and with appropriate validation by reference laboratories they could be more widely used in developing countries to obtain local and regional data on pneumococcal serotype distribution.
Forty two pneumococcal strains obtained in Vellore, Tamil Nadu, from 42 patients with invasive diseases, namely pneumonia, meningitis, or peritonitis were typed. Over one-third of pneumococci in children and nearly half in adults were serotype followed by serogroups/types 5, 6 and 7 which were most common in children and adults taken together. These 4 serogroups/types accounted for 11 (79%) of 14 strains in children and 20 (71%) of 28 strains in adults. The remaining 11 strains belonged to 8 serogroups/types, namely 3, 4, 10, 11, 12, 13, 19 and 20.
The confirmation of the identity of Vibrio cholerae serogroup 01 and serogroup 0139 is usually done by slide agglutination tests using specific antisera. Antiserum to V. cholerae 01 is freely available but not antiserum to V. cholerae 0139, thus making specific identification of the latter more difficult. A modified CAMP (Christie Atkins and Muench - Paterson) test has been described as a possibility in the identification of V. cholerae 0139 and we have evaluated this on 197 strains of organisms including 48 V. cholerae 0139, 50 V. cholerae 01, 49 non-01, non-139 V. cholerae and 50 Aeromonas species. The test had a sensitivity of 98.9 per cent and a specificity of 92.9 per cent in the identification of these strains, when compared with faeces culture as the gold standard.
Diagnosis of melioidosis by the isolation of Burkholderia pseudomallei from one or more body fluid/tissue specimens of 6 Indian subjects, 5 of whom had not travelled outside India, is reported. The places of residence of these 6 and one patient previously reported, namely Tripura (2), Kerala (2), Orissa (1), Tamil Nadu (1) and Maharashtra (1) are therefore potentially endemic for melioidosis. B.pseudomallei closely resembles common contaminant Pseudomonas sp. and are easily mis-identified in microbiology laboratories. We surmise that melioidosis is underdiagnosed and underreported in India and we alert clinicians, microbiologists and public health professionals to the possibility of melioidosis being far more common than previously recognised.
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.
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