Enterococcus fecal

On the basis of log bacterial survival rates, the antibacterial activity of rifaximin was greater than that of paromomycin against Enterococcus spp., anaerobic cocci, Bac-terioides spp. and Clostridium spp. isolated in fecal samples from 20 patients with subclinical hepatic encephalopathy (fig. 4) [81]. On the other hand, E. coli dead Klebsiella spp. appeared more susceptible to paromomycin while both antibiotics showed equal potency against Proteus spp. [81]. Here again it should be pointed out that stool concentrations of rifaximin are 250-500 times higher than the MIC90 values [71], which makes the in vitro differences of activity between this and other antimicrobials meaningless from a clinical standpoint. 

Antimicrobial resistance to rifamycins develops rapidly both in vitro and in vivo [65,85,86], As a consequence, all the three members of the family (i.e. rifampicin, rifabutin and rifapentine) are used clinically as components of combination therapies [65,87], Being structurally related, rifaximin could share this potential. And indeed resistance rates, recorded in fecal strains of Enterobacteriaceae, Enterococcus, Bacteroides, Clostridium and anaerobic cocci, ranged between 30 and 90% after short-term (5 days) antibiotic (800 mg daily) treatment [82], A similar pattern was observed in 10 patients with hepatic encephalopathy after treatment with rifaximin 1,200 mg/day for 5 days [80]. 

To understand the role of antibiotics, it is important to understand their effects on the fecal flora. The normal flora consists of a complex bacterial population with 400-500 distinct species of bacteria (table 2a). More than 99% of the total organisms are accounted for by non-sporeforming anaerobic rods [28] the four major species are Bacteroides, bifidobacteria, eubacteria and peptostrepto-cocci [29], Other common species are Escherichia coli, Streptococcus viridans, Streptococcus salivarius and lacto-bacilli. Mette et al. [30] clarified the prevalence of species in fecal flora by listing the four most common anaerobes Bacteroides spp., Eubacterium spp., Bifidobacterium spp. and anaerobic cocci) and three common aerobes E. coli spp., Enterococcus spp. and Lactobacillus spp.) (table 2b). 

Gut flora of rats, but not guinea pigs, are able to metabolize cascarosides to aloe-emodin. Enterococcus faecalis andE. faecium, common gut flora, lack the enzymes necessary for this conversion. Human fecal flora is able to metabolize barbaloin, but the bacteria responsible have not been identified (De Witte, 1993). 

In an in vitro model epithehal cells (T 84 cell line) were combined with myofibroblast cells (CDD-18 Co cell line) in a coculture. SCFAs as they appear in the feces of breastfed infants were used. These SCFAs stimulated mucin 2 production and improved the barrier integrity (62). The effect of SCFA on growth of pathogens like Escherichia coli (ETEC), Enterococcus faecalis. Pseudomonas aeruginosa, Salmonella typhimurium, and Staphylococcus aureus as well as of commensals has been studied in vitro at pH 7.5 (typical fecal pH in formula-fed infants) and at pH... 

Not all bacteria are pathogenic or harmful to humans. Some microorganisms are harmless or even some are very useful for human beings. An example is the lactobacilli in human stomach that helps in converting lactose and other sugars to lactic acid. However, these bacteria will cause disease if they are detected in environments that are not their normal habitat. Thus, the presence of certain bacteria out of their normal habitat is an indicator of a certain disease or contamination. For example. Enterococcus species is used as an indicator of fecal pollution in environmental waters, while the detection of species-specific Enterococcus faeciutn is used as an indicator of human fecal pollution [13]. On the other hand, the presence of some bacteria almost certainly indicate an infection for example, Mycobacterium tuberculosis causes tuberculosis, and Streptococcus and Pseudomonas cause pneumonia. 

LAB (such as Lb. plantarum and Lb. fermentum, together with members of the genera Leuconostoc and Weissella) accounted for 90-97% of the total active nucrobiota of pozol no streptococci were isolated, although members of the genus Streptococcus accounted for 25-50% of the microbiota (Ampe et al., 1999). The presence of Bifidobacterium, Enterococcus and enterobacteria suggests a fecal origin of some important pozol microorganisms (Ben Omar Ampe, 2000). 

The various types of media used for the presumptive and confirmatory tests for fecal streptococci along with the respective characteristic colors and appearances of the colonies are presented in Table 4.12. However, the two media most commonly used for presumptive fecal streptococci tests are membrane enterococcus (mE) agar and the Kenner Fecal (KF) streptococcus agar, although the mE agar is more selective than the KF streptococcus agar [152]. 

Confirmatory test Confirmation of the presence of fecal streptococci in the sample is done by subculturing in bile esculin azide agar (BEAA) or Pfizer selective enterococcus (PSE) agar. The subculture is incubated at 44°C (BEAA) or at 35°C 0.5°C (PSE agar) for 24 2 h. Brownish-black colonies with brown halos confirm the presence of fecal streptococci in the culture. 

---