Susceptibility of the organism

Once the organism has been identified and sensitivities are known, drug selection should be adjusted to reflect the susceptibilities of the organism. Streptococcal, staphylococcal, and enterococcal species sensitive to P-lactam antibiotics should be treated with continuous IP dosing to increase efficacy and minimize resistance.49 Peritonitis caused by S. aureus or P. aeruginosa are often associated with catheter-related... 

The treatment of choice until susceptibility of the organism is known as the combination of vancomycin plus ceftriaxone. Penicillin may be used for drug-susceptible isolates with minimum inhibitory concentrations of 0.06 mcg/mL or less, but for intermediate isolates ceftriaxone is used, and for highly drug-resistant isolates a combination of ceftriaxone and vancomycin should be used. A high percent of S. pneumoniae is either intermediately or highly resistant to penicillin. 

There are thus three types of biomarkers biomarkers of exposure of the organism to the toxic substance, biomarkers of response of the organism to that exposure, and biomarkers of susceptibility of the organism to the chemical. 

This type of correlative approach is widespread, as only a few marine studies involving inducible defenses (and none with mobile invertebrates) have directly demonstrated that the induction results in a decrease in the susceptibility of the organism to predation.71,72 Statistically significant differences in shell thickness or concentrations of defensive chemicals may or may not meaningfully affect predator preferences in ecologically relevant field situations. For chemical defenses, compound dose-response relationships may be nonlinear, and threshold levels of defense could be sufficient to deter predators so that further induction has little additional benefit. Thus, future studies should focus on directly demonstrating whether an induced response reduces predation on prey organisms. 

Toxic effect Any change in an organism that results in impairment of functional capacity of the organism (as determined by anatomical, physiological, biochemical, or behavioral parameters) causes decrements in the organism s ability to maintain its normal function or enhances the susceptibility of the organism to the deleterious effects of other environmental influences. 

Penicillin is used to treat infections caused by Grampositive cocci, Gram-negative aerobic cocci, and anaerobic bacteria. The penicillins may be bactericidal or bacteriostatic in action, dependent upon the concentration of drug attained at the sire of infection and susceptibility of the organism. 

After identification and qnantification are complete, the next step is to determine the susceptibility of the organism. There are several methods by which bacterial snsceptibihty testing may be performed. Knowledge of bacterial susceptibihty and achievable mine concentration of the antibiotics puts the clinician in a better position to select an appropriate agent for treatment. 

The effect of antibiotics on the Salmonella reservoir varies with the antibiotic susceptibility of the organisms. In previous studies the Salmonella reservoir decreased when animals were infected with an antibiotic-sensitive organism 1) but increased when infected with an antibiotic-resistant organism ( ). Neu and coworkers (9-10) have confirmed that antibiotic resistance is increasing in Salmonella isolated from humans (Table II). Resistance of typhlmurlum to Ampicillin increased from 23.4% in 1969 to 36.9% in 1974, resistance to Streptomycin increased from 27.3% to 45.6% and resistance to Tetracycline increased from 12.5% to 44.8%. 

Change the susceptibility of the organism to the deleterious effects of other environmental influences. ... 

There is a growing concern over the use of herbal remedies containing PAs since pyrrolizidine-induced liver damage can be cumulative. The toxicity of PAs depends on the exposure time, dosage amount, and susceptibility of the organism. In humans, the dosage appears to fall within the range of 0.1-10 mg/kg per day [38]. Low levels... 

Studies on Blastomyces dermatitidis isolated from both improved and unimproved cases receiving hamycin therapy revealed that the variation in clinical response was not due to differences in susceptibility of the organism. ... 

COD provides i measure of the oxygen equivalent to that portion of the organic mtitter in i sample that is susceptible to oxidation by a strong chemical oxidant. A higher level of COD can be degraded (neutralized) chemically. The le el of COD. however, automatically reduces with the level of BOD and no further treatment is normally necessary. 

Propagated outbreaks of infection relate to the direct transmission of an infective agent from a diseased individual to a healthy, susceptible one. Mechanisms of such transmission were described in Chapter 4 and include inhalation of infective aerosols (measles, mumps, diphtheria), direct physical contact (syphilis, herpes virus) and, where sanitation standards are poor, through the introduction of infected faecal material into drinking water (cholera, typhoid). The ease oftransmission, and hence the rate of onset of an epidemic (Fig. 16.3) relates not only to the susceptibility status, and general state of health of the individuals but also to the virulence properties of the organism, the route oftransmission, the duration of the infective period associated with the disease. 

For enterococci, it is imperative to determine species and antibiotic susceptibilities. If the organism is susceptible to penicillin and vancomycin, treatment may consist of high-dose penicillin G, ampicillin, or vancomycin plus gentamicin (see Table 71-6). Treatment length is usually 4 to 6 weeks, with the aminoglycoside used over the entire course. As resistance develops to penicillin, ampicillin and vancomycin remain treatment options. Once the isolate becomes resistant to ampicillin, vancomycin is considered the treatment of choice. 

If possible, follow-up on susceptibilities of the infecting organism (urine culture)... 

The oxidation of organic compounds by water-soluble inorganic oxidants is often made difficult not only by the insolubility of the organic substrate in water, but also by the susceptibility of many of the miscible non-aqueous solvents to oxidation. Solubilization of the ionic oxidant into solvents such as benzene, chloroform, dichloromethane or 1,2-dichlorobenzene, by phase-transfer catalysts obviates these problems, although it has been suggested that dichloromethane should not be used, as it is also susceptible to oxidation [1]. 

It is well known, for example, that about 5 per cent of the people who become infected with typhoid germs become typhoid carriers and continue indefinitely to harbor an active colony (harmless to them) of typhoid bacilli in their intestinal tracts. There is abundant evidence of graded susceptibility there are many mild cases, and the incubation time in different individuals may be from 3 to 30 days, indicating variable resistance. The fact that about 70 per cent of the carriers are women suggests that the constitutional characteristics which make it possible for individuals to endure the presence of the organisms are in some way sex-linked in their inheritance. The evidence with respect to typhoid carriers, diphtheria carriers, scarlet-fever carriers, poliomyelitis-virus carriers, etc., makes it seem probable that "carriers" enter into the dissemination of many other milder infections, and... 

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