Fresh Bacterial Isolates Research Articles

PERFORMANCE OF THE VITEK MS MATRIX-ASSISTED LASER DESORPTION IONIZATION-TIME OF FLIGHT MASS SPECTROMETRY SYSTEM FOR RAPID IDENTIFICATION OF CLINICAL MICROBIOLOGY ISOLATES

Background: Rapid and precise microbial identification is essential for timely patient management and control of infection. Conventional microbiological procedures are time-consuming, laborious, and require expertise. Recent coalition of MALDI-TOF in the microbiology workflow has yielded excellent results so far. Here we have assessed this quick proteomic based technique for clinical bacterial isolates identification. Material and Methods: All fresh bacterial isolates were selected for VITEK MS (bioMérieux, France) analysis, the bacteria were identified by using MALDI-TOF System (IVD 3.2) software. For same isolates, API (bioMérieux, France) was set as per kit instructions and conventional/biochemical tests were performed according to ASM Guidelines. Results: Among 200 isolates 99% were accurately identified by the VITEK MS system to the species level, one of two isolates was mis-identified (Shigella as E. coli) while the other was identified later by re-spotting. On testing these samples in parallel by APIs, 91.50% were correctly identified, while 8.50% (17 samples) showed discrepant results. These were re-analyzed by VITEK-2 (bioMérieux, France) semi-automated system which showed the same results as those of VITEK MS. Our findings revealed diagnostic accuracy of VITEK MS in comparison with APIs in terms of time, cost and patient management. Conclusion: For bacterial identification MALDI-TOF MS is an expeditious, authentic and comparatively inexpensive system. Our results emphasize that it is speedy technique which can replace the traditional identification methods for most of bacterial strains on their routine isolation. This ingenious approach complies with advanced patient management and therapeutic intervention. Key Words: MALDI-TOF MS, bacterial identification, VITEK-2, Analytical profile index (API), Clinical microbial isolates

Production of indolic compounds by rumen bacteria isolated from grazing ruminants

To screen rumen bacterial cultures and fresh ruminal isolates for indole and skatole production. Culture collection strains and fresh bacterial isolates from rumen contents of sheep and dairy cows were screened for the production of indolic compounds. Clostridium aminophilum FT, Peptostreptococcus ssp. S1, Fusobacterium necrophorum D4 produced indole and Clostridium sticklandii SR produced indoleacetic acid. Fresh isolates from sheep (TrE9262 and TrE7262) and dairy cows (152R-1a, 152R-1b, 152R-3 and 152R-4) produced indole, indolepropionic acid, tryptophol and skatole from the fermentation of tryptophan and indoleacetic acid. Glucose altered the indolic compounds produced in some, but not all, isolates. TrE7262 and 152R-4 were identified as Clostridium sporogenes and 152R-1b as a new Cl. aminophilum strain. Isolates TrE9262, 152R-1a and 152R-3 were not closely related to any described species but belong to Megasphaera, Prevotella and Actinomyces genera, respectively. Rumen bacteria that produced a range of indolic compounds were identified. Some isolates are distinct from the previously described bacteria and may represent novel species. These observations will contribute to understanding skatole and indole formation in the rumen and will lead to methods that control the formation of indolic compounds in pasture-grazed ruminants.

Comparison of in vitro Susceptibilities of Ocular Bacterial Isolates to Gatifloxacin and Other Topical Antibiotics

Purpose: To compare the in vitro activity of gatifloxacin with that of other topical antibiotics against fresh bacterial isolates from various types of human ocular infections. Methods: A total of 498 strains of ocular bacterial isolates were tested for their susceptibility to gatifloxacin, ofloxacin, ciprofloxacin, norfloxacin, gentamicin, tobramycin, neomycin, chloramphenicol, erythromycin, tetracycline and amikacin. Results: Ninety-nine percent of gram-positive and 92% of gram-negative bacterial strains were found to be susceptible in vitro to gatifloxacin, whereas lower percentages of gram-positive and gram-negative bacteria were found to be susceptible to other antibiotics. Conclusions: In vitro, gatifloxacin exhibits good activity against various bacterial species isolated from different ocular sites. This requires corroboration in the clinical setting.

Multicenter in vitro comparative study of fluoroquinolones against 25,129 Gram-positive and Gram-negative clinical isolates

In vitro activities of fleroxacin, ciprofloxacin, ofloxacin, and lomefloxacin were evaluated against 25,129 fresh bacterial isolates from 51 US hospital or medical center laboratories, beginning in October of 1990. Susceptibility rates were ⩾85% against most species of Gram-negative bacteria. Notable exceptions were Pseudomonas, Acinetobacter, Xanthomonas, and Providencia. The study drugs displayed similar activity against most Gram-negative species. At least 90% of oxacillin-susceptible staphylococci were susceptible but, of oxacillin-resistant strains, only approximately 60% of Staphylococcus epidermidis and 25% of Staphylococcus aureus were susceptible to the quinolones tested. Staphylococcus saprophyticus strains were less susceptible to fleroxacin (42%) than to the other compounds (79%–97%). Ofloxacin and ciprofloxacin were more active against streptococci, and none of the compounds demonstrated appreciable activity against enterococci. Thus, the spectra of activity of fluoroquinolones illustrate that they remain effective agents for the treatment of many types of infections caused by Gram-negative pathogens.

Immunoglobulin A antibodies to mutans streptococci in human saliva and serum comparing fresh and subcultivated strains and activity in repeated saliva samples

The aims of this study were i) to characterize and compare the sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein patterns of reference Streptococcus mutans and Streptococcus sobrinus strains, subcultivated for years, with fresh isolates of the same serotype; ii) to study possible differences between the human salivary immunoglobulin A (IgA) activity to reference strains and to fresh bacterial isolates of the saliva donors; iii) to examine for potential differences in the salivary IgA activity to the streptococcal antigens during 1 week; and iv) to map, in the same individuals, the serum IgA activity against the selected bacteria. S. mutans reference and fresh isolated strains showed a similar protein pattern with few exceptions. The immunoblot also revealed similarity in saliva IgA response, with only one subject's saliva displaying clearly one band's difference. For S. sobrinus a larger discrepancy was seen. The antibody activity during the one week interval was essentially unchanged. When incubated with serum, a different immunoblot profile was seen compared with saliva, although most bands revealed by saliva were also displayed by serum.

Multicenter in vitro comparative study of fluoroquinolones after four years of widespread clinical use

In vitro activities of ciprofloxacin, fleroxacin, lomefloxacin, ofloxacin, and seven other oral antimicrobials including amoxicillin-clavulanic acid (A/C), oxacillin, cefaclor, cefixime, cefuroxime, erythromycin, and trimethoprim-sulfamethoxazole (T/S) were evaluated against 1708 fresh bacterial isolates from four hospital laboratories ~4 years after the introduction of ciprofloxacin. T/S and ofloxacin had the lowest MIC 90s and greatest percentage of susceptible strains overall, followed by the other three quinolones. Quinolones were the most active drugs tested against Gram-negative bacteria, with little variation in the activity among the four compounds against most species. Quinolone resistance was detected to some degree in the majority of Gram-negative species tested, with Pseudomonas, Acinetobacter, Xanthomonas, and Providencia demonstrating the highest percentage of resistant strains. Ofloxacin and ciprofloxacin were relatively more active against Gram-positive bacteria than were fleroxacin and lomefloxacin, but T/S and A/C had more susceptible strains than any of the quinolones. Oxacillin-resistant staphylococci, enterococci, and streptococci exhibited the least quinolone susceptibility. This study showed that while resistance is developing among several previously susceptible bacterial species, quinolones remain important alternatives for the oral treatment of many types of infections. Actions to prevent or limit resistance will be important to maintain the viability of the quinolones as therapeutic agents in both hospital and community environments.

Comparative in vitro activity of lomefloxacin (SC 47111 or NY-198) against fresh clinical bacterial isolates

The in vitro antibacterial activity of a new difluorinated quinolone (lomefloxacin) was compared with that of ten selected antibiotics against 744 fresh bacterial isolates representing 32 species. Lomefloxacin was comparable to other quinolones tested against Enterobacteriaceae (MIC 90, ⩽0.25 μg/ml) and generally more effective than other compounds tested against Staphylococcus spp. and Pseudomonas aeruginosa with MIC 90s of ⩽2 and ⩽4 μg/ml, respectively.

Observation of fimbriae and flagella in dispersed subgingival dental plaque and fresh bacterial isolates from periodontal disease.

The interbacterial matrix of subgingival plaque obtained from 12 individuals was examined by agar‐filtration negative stain electron microscopy. Flagellated bacteria were abundant in all samples from patients having periodontal disease. In addition, the plaques of all patients having periodontal disease, with the exception of two children diagnosed as having localized severe periodontitis, had varying amounts of long thin filamentous extracellular bacterial appendages morphologically identical to bacterial fimbriae. These appendages seemed to form into bundles to which bacterial membranes, blebs, and debris appeared to attach. Further studies examined the cell surface structures of bacteria freshly isolated from several of these plaque samples. Of 113 bacterial colonies examined, 49 (43.3%) had surface fimbriae like appendages. Actinobacillus actinomycetemcomitans, Bacteroides gracilis, Actinomyces odontolyticus, Capnocytophaga species, Fusobacteria species, and Haemophilus species had fimbriae. Only 4 of 113 colonies bore flagella. It was concluded that bacterial extracellular appendages resembling fimbriae are common morphologie components of plaque interbacterial matrix and may pay play a significant role in adhesive interactions within plaque. Although flagellated bacteria were commonly seen within subgingival plaques, few fresh isolates were observed to produce these structures.

In-vitro activity of an antibacterial substance from rabbit polymorphonuclear leukocytes.

gen, the sugar residues (which confer 0 specificity and constitute the smooth, virulent side chains), and the stereochemical configuration between the cell-wall components all appear relatively unimportant for the expression of the cidal activity of the leukocytic extract. The possible presence of host antigens on fresh bacterial isolates and of serum in the in-vitro assay system, however, interfered with the cidal property. It is suggested that the cidal system of polymorphonuclear leukocytes may represent a defense mechanism in which a few related proteins could accomplish a number of tasks by interaction with a susceptible ligand on the unit bacterial cell wall. Bactericidal activity in extracts from polymorphonuclear leukocytes (PMNs) of several mam