Biomedical subjects

K Nessa

Publications and source records attributed to K Nessa.

9 recordsLinked to original sources

PubMed2001

Treatment failure with the use of ciprofloxacin for gonorrhea correlates with the prevalence of fluoroquinolone-resistant Neisseria gonorrhoeae strains in Bangladesh.

Although ciprofloxacin is one of the recommended drugs of choice for the treatment of gonorrhea, in vitro resistance to this drug has been observed in surveillance studies and case reports from many parts of the world, including Bangladesh. However, to our knowledge, there have been no prospective studies of the correlation between in vitro response to the drug and treatment outcome. Therefore, a prospective study of 217 female sex workers in Dhaka, Bangladesh, was conducted to examine the correlation between the in vitro response of Neisseria gonorrhoeae and the outcome of ciprofloxacin treatment. Overall, 37.8% of the gonococcal isolates recovered from female sex workers were resistant to ciprofloxacin, and there was a good correlation between in vitro resistance and treatment failure. These findings suggest that in vitro resistance to ciprofloxacin is predictive of clinical treatment failure in patients with gonorrhea.

Adult↗

PubMed2000

Etiology of sexually transmitted infections among street-based female sex workers in Dhaka, Bangladesh.

An etiological study of sexually transmitted infections (STIs) was conducted among female sex workers (FSWs) in Dhaka, Bangladesh. Endocervical swab and blood samples from 269 street-based FSWs were examined for Neisseria gonorrhoeae, Chlamydia trachomatis, and Trichomonas vaginalis as well as for antibodies to Treponema pallidum and herpes simplex virus 2 (HSV-2). Sociodemographic data and data regarding behavior were also collected. A total of 226 of the 269 FSWs (84%) were positive for the STI pathogens studied. Among the 269 FSWs, 35.5% were positive for N. gonorrhoeae, 25% were positive for C. trachomatis, 45.5% were positive for T. vaginalis, 32.6% were seropositive for T. pallidum, 62.5% were seropositive for HSV-2, and 51% had infections with two or more pathogens.

Animals↗

PubMed1999

Production of nitric oxide by rat alveolar macrophages stimulated by Cryptococcus neoformans or Aspergillus fumigatus.

Cryptococcus neoformans and Aspergillus fumigatus are airborne fungi and the alveolar macrophages (AM) constitute a first line of host defence against both pathogens. We investigated the ability of rat AM to produce nitric oxide (NO) when challenged in vitro with C. neoformans, A. fumigatus conidia or inert silica particles alone and together with interferon gamma (IFN-Gamma). The role of NO in the killing of C. neoformans as well as the relationship between phagocytosis of the yeast or A. fumigatus conidia and NO production by AM were studied. Both fungi, but not the inert particles induced a small but significant increase in NO production by AM. A synergistically enhanced NO production by AM was observed when each fungus, but not silica particles, were incubated together with IFN-Gamma. AM treated with IFN-Gamma and challenged with C. neoformans showed higher killing activity than untreated AM, a finding that correlated with increased NO production by AM. Both effects were reduced by an inhibitor of NO synthesis. Increased NO production by IFN-Gamma activated AM was found together with an increased accumulated attachment of A. fumigatus conidia and serum opsonized, but not unopsonized C. neoformans. The IFN-Gamma dependent increase in accumulated attachment of the fungi might be responsible for the synergistic effect of the fungi and IFN-Gamma on the NO production. Our data suggest that activated rat AM might efficiently use the antimicrobial nitric oxide system in the defence against these pathogens in the normal host.

Animals↗

PubMed1997

In vitro interaction of alveolar macrophages and Aspergillus fumigatus.

In vitro interaction of alveolar macrophages (AM) from rats with conidia from Aspergillus fumigatus and Aspergillus candidus as well as inert control particles (amorphous silica) of similar diameter (about 3 microns), was studied. Experimental observations showed that both kinds of conidia were phagocytized significantly faster by AM than were the control particles due to a faster rate of attachment, but even more so due to a faster rate of ingestion. Quantitative nitroblue tetrazolium reduction by AM reflecting their oxidative metabolism and oxygen radical release was increased in response to both kinds of conidia by a factor of 2-3 during the process of phagocytosis, as well as 24 hr after the onset of phagocytosis, compared to corresponding conditions with inert particles and to resting macrophages. The mean pH in phagolysosomes with each of the conidia tended to be higher after 3 hr but was significantly lower after 24 hr than in the phagolysosomes with the control particles. After 3 hr there was a considerable percentage (around 8%) of phagolysosomes with pH > or = 6.5 and after 24 hr there was still a small percentage (0.7%) of such phagolysosomes for each of the conidia. Such a fraction was not observed for the control particles. Electron microscopic studies showed passages between phagolysosomes and AM surface with both kinds of conidia. The occurrence of such unsealed phagolysosomes might explain the percentage of phagolysosomes with high pH. Hence, Aspergillus conidia in unsealed macrophage vacuoles mediate an increased oxygen radical release from the macrophages, a process which in the long run might cause lung damage.

Animals↗

PubMed1997

Reaction of human alveolar macrophages to exposure to Aspergillus fumigatus and inert particles.

In vitro interaction of human alveolar macrophages (AM) with heat-killed conidia from Aspergillus fumigatus and inert silica particles of similar size, about 3 microns, was studied. The conidia were phagocytized significantly faster by AM than were the control particles partly due to the faster rate of attachment but especially due to the faster rate of ingestion. Quantitative nitroblue tetrazolium (NBT) reduction by AM, reflecting their release of oxygen radicals, was increased by a factor of 2 to 3 in response to the conidia during phagocytosis. The silica particles induced a moderate but significant increase in NBT reduction. Conidia, but not silica particles, showed a considerable percentage (around 8%) of phagolysosomes with neutral pH after 3 h and a smaller percentage (around 1%) after 24 h of incubation. The pH of phagolysosomes with conidia tended to be higher after 3 h, but was significantly lower after 24 h than the pH of phagolysosomes with silica particles. Despite the markedly increased oxidative metabolism there was no increase in cytokine production [interleukins (IL) 6 and 8 and tumor necrosis factor alpha (TNF-alpha)] after exposure to conidia. The silica particles induced a significant decrease in IL-6 and IL-8 production and a tendency toward decreased production of TNF-alpha. The occurrence of phagolysosomes with neutral pH suggests unsealed phagolysosomes from which not only oxygen metabolites but also enzymes might escape from the cell. Lung damage may thus be the result of repeated or long-term exposure to Aspergillus conidia.

Adolescent↗

PubMed1997

In vivo interaction between alveolar macrophages and Cryptococcus neoformans.

In vivo interactions of rabbit alveolar macrophages (AM) and Cryptococcus neoformans, a yeast pathogenic for humans, were studied. As a control, inert silica particles of a similar diameter (5-6 microns) were used. Of 16 rabbits, 6 were instilled intratracheally with fluorescein-labelled heat-killed C. neoformans, 6 with fluorescein-labelled silica particles and 4 with saline only. After 24 h, the AM were collected by lung lavage, and phagocytosis, oxidative metabolism, phagolysosomal pH and morphology were studied. The accumulated number of yeasts attached to the AM was almost the same for C. neoformans as for the silica particles. The ingested fraction of C. neoformans was even higher than that of the silica particles. Quantitative NBT reduction by the AM, reflecting their oxidative metabolism, was markedly increased by exposure to C. neoformans for 24 h. The phagolysosomal pH was on the average lower in phagolysosomes with C. neoformans than with the silica particles, although approximately 2% of the phagolysosomes with C. neoformans had neutral pH. Phagolysosomes with neutral pH was not observed for silica particles. Electron microscopy showed presence of C. neoformans in phagolysosomes of AM. The conclusion of this study is that the phagocytic activity, oxidative metabolism and phagolysosomal pH AM against C. neoformans are significant 24 h after the exposure.

Animals↗

PubMed1997

Alveolar macrophage reaction to Candida species.

Candida species are increasingly important fungal pathogens. The reaction of rat alveolar macrophages (AM) to Candida albicans was compared with that to C. glabrata and C. krusei. Phagocytosis of C. glabrata was similar to that of C. albicans, but significantly slower for C. krusei due to reduced attachment. After opsonization, attachment of C. albicans and C. krusei to AM was significantly increased and there was no significant difference between the two species. The oxidative metabolism of AM with candida species was two to three times higher than that of the resting AM both during and 24 h after the phagocytosis. All three species showed a considerable fraction (5-10%) of phagolysosomes with pH > or = 6.5 after 3 h and a smaller percentage (1%) after 24 h.

Animals↗

PubMedDate not supplied

Alveolar macrophage response to yeasts and inert particles.

Interactions between alveolar macrophages (AM) from rats and a yeast with relatively high pathogenicity (Candida albicans), a yeast with low pathogenicity (Saccharomyces cerevisiae) and an inert control particle (amorphous silica) of similar diameters, 3-4 microns, were studied. Both yeasts were phagocytized significantly faster by AM than were the control particles and C. albicans significantly faster than S. cerevisiae. Quantitative nitroblue tetrazolium reduction by AM reflecting their oxidative metabolism was markedly increased in response to both fungi during the period of phagocytosis as well as 24 h after the phagocytosis. Macrophages with silica particles also showed a moderate but significant increase in oxidative metabolism 24 h after phagocytosis. Phagolysosomal pH was significantly higher for S. cerevisiae than the control particles after 3 and 24 h. pH in phagolysosomes with C. albicans tended to be higher after 3 h but was significantly lower after 24 h than in the phagolysosomes with silica particles. Both yeasts showed a considerable number (around 10%) of phagolysosomes with high pH > or = 6.5 after 3 h and a smaller percentage after 24 h. No such fraction could be seen for the control particles. Electron microscopy showed narrow passages from AM cell surface to phagolysosomes with particles. These passages might be more frequent in AM containing the yeasts and could explain the phagolysosomes with high pH.

Animals↗

PubMedDate not supplied

Interaction between Cryptococcus neoformans and alveolar macrophages.

Phagocytosis, oxidative metabolism and phagolysosomal pH of rat alveolar macrophages (AM) were studied at different points of time after challenge with Cryptococcus neoformans. Phagocytosis was evaluated using a fluorescent quenching technique which distinguishes between attached and ingested organisms. The nitroblue tetrazolium (NBT) test was used as an indirect measurement of the oxidative metabolism of the phagocytes. The pH of the phagolysosomes was measured using a cytofluorometric technique. Both the attachment and ingestion of serum opsonized C. neoformans by AM were slow during the first hours of incubation, but were considerable after 24 h. The oxidative metabolism of Am challenged with the yeast was insignificant during the first hour, but reached high levels after 24 h. Most phagolysosomes in AM with ingested cryptococci had a pH < 5.5. Our results indicate that these AM defence mechanisms, although poor during the first hours after exposure to the yeast, are of significance after 24 h. Thus, in the immunocompetent host the AM should prevent the dissemination of C. neoformans from the lungs.

Animals↗