The guanine-plus-cytosine content ranges from 26 to 34 percent. Members of the genus Fusobacterium ( Figs.20-6 and 20-7) may be spindle shaped or may have parallel sides and rounded ends. Serologic methods have not been reliable for characterizing Gram-negative anaerobic rods. Prevotella melaninogenica endotoxin contains no heptose or 2-ketodeoxyoctanate, and it and the endotoxin of P oralis both show weak biologic activity. Poor biologic activity of endotoxin also has been demonstrated for the closely related species B thetaiotaomicron, B ovatus, B vulgatus, and B distasonis. This endotoxin exhibits little biologic activity in various test systems and little chemotactic activity what activity there is is complement-mediated by the alternative pathway. Numerous studies of the endotoxin of Gram-negative anaerobic bacilli have determined that the B fragilis endotoxin contains little or no lipid A, 2-ketodeoxyoctanate, or heptose. These genera contain numerous other species that rarely or never infect humans.Ĭolony morphology of P melaninogenica. Fusobacterium nucleatum is the Fusobacterium species most often found as a pathogen, but F necrophorum occasionally produces serious disease. Porphyromonas species seem to be much less pathogenic except in dental infections. Among the bile-sensitive Prevotella species, the ones most commonly encountered clinically are P melaninogenica, P oris, and P buccae. Within the Bacteroides group, B fragilis is the most common pathogen, followed by B thetaiotaomicron and other members of the B fragilis group. These genera are prevalent in the body as members of the normal flora ( Fig.20-1), constituting one-third of the total anaerobic isolates from clinical specimens, and may become involved in infections throughout the body ( Fig.20-2). In most clinical infections, only the genera Bacteroides, Prevotella, and Fusobacterium need be considered. range of the quinolone ciprofloxacin does not exceed 6 micrograms/ml.At present there are over two dozen genera of Gram-negative anaerobic bacilli. The minimal inhibitory concentrations (M.I.C.) of gentamicin, cephalothin, cefotaxime, ceftazidime ceftriaxone and sulfamethoxazole-trimethoprim do not exceed the range of 30 micrograms/ml. Low resistance is still seen in all above bacteria against ciprofloxacin and ofloxacin. Resistance frequencies of above 20% were found in Enterobacter and Pseudomonas for the newer antimicrobial agents such as: ceftriaxone, cefotaxime or ceftazidime. As for tobramycin, amikacin and mezlocillin, it is clear that the Gram negative bacteria have gained resistance to these drugs over recent years. In UPGNB, Klebsiella and Pseudomonas a significant increase in resistant isolates to cephalothin, gentamicin, sulfamethoxazole-trimethoprim and chloramphenicol was found. A significant rise in frequency of cephalothin and sulfamethoxazole-trimethoprim resistant E. coli was most predominant in both surveys in the internal wards while UPGNB were predominant in the geriatric-rehabilitation wards. coli, Urea positive Gram negative bacteria (UPGNB) Klebsiella, Enterobacter, Pseudomonas (in a decreasing order). The order of Gram negative frequencies was E. Gram negative rods accounted for 68% of the septicemia cases indicating a small increase since the former survey (61.2%). In addition, a comparison was made with a previous survey performed twelve years ago (1976-1978). This study reviews 2205 significant positive blood cultures from 534 patients treated at the Meir General Hospital during the period 1988-1990.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |