Index
The problem of antimicrobial resistance to antibiotics has led to antibiotic therapy focusing on the use of antibiotics.
In a way that ensures a favorable effect for the individual patient and the minimization of the subsequent antimicrobial resistance.
Although adequate antibiotic therapy may generate resistance, inadequate treatment can also adversely affect bacterial ecology.
To achieve adequate therapy, treatment must be initiated correctly, using microbiological data faithfully and subsequent evaluations.
Until you achieve an adequate response, that may involve decreasing therapy or interrupting it.
Precise diagnosis
The infectious disease diagnosis is achieved by determining the site of infection, defining the host: Immunocompromised, diabetic, or elderly, among others, and establishing, when possible, a microbiological diagnosis.
It is essential to isolate the pathogen in severe infections, mainly in situations that may require prolonged therapy, such as endocarditis, septic arthritis, or meningitis.
Similarly, when a patient does not present favorable results to the chosen antimicrobial therapy, additional studies are required to determine the agent or exclude noninfectious diagnoses.
To optimize the diagnosis, it must be ensured that the samples for the east are obtained and processed correctly.
The microbiological diagnosis is based on bacterial or fungal cultures or serological tests; it is possible to make an accurate diagnosis because it can be inferred from the clinical presentation as cellulitis.
This is caused by streptococci or staphylococci, and an antibacterial treatment can be administered without culture.
The first step in performing antibiotic therapy is a specific diagnosis, whether a tentative clinical diagnosis or not.
Moment of the start
The time to start therapy should correspond to the urgency of the situation.
In patients with septic shock, febrile neutropenic patients, and patients with bacterial meningitis, empirical therapy is started immediately, simultaneously with the collection of diagnostic samples.
In more stable clinical conditions, antibiotic therapy should be initiated deliberately after the appropriate samples have been collected and the results obtained.
With this principle, therapies are initiated in cases of subacute bacterial endocarditis and, osteomyelitis, vertebral discitis. The administration of antibiotics is delayed until the results of the blood cultures, aspiration of the infected intervertebral disc space, or bone biopsy samples.
In these circumstances, the premature initiation of antimicrobial therapy can suppress bacterial growth and impede the opportunity to establish a successful microbiological diagnosis.
Empirical or definitive antibiotic therapy
Microbiological results may be available 24 to 72 hours after the sample is taken, so the initial therapy for the infection is usually empirical and guided by the clinical history.
A common approach is to use broad-spectrum antimicrobial agents or combinations as initial empirical therapy to cover multiple potential pathogens commonly associated with a specific clinical symptom.
When microbiology results have identified the pathogen and the antimicrobial susceptibility data are available, the spectrum of antibiotics should be reduced.
This is an essential factor in antibiotic therapy because it reduces toxicity and prevents the emergence of resistance of microbes in the body.
Bacteriostatic and bactericidal therapy
Bactericidal drugs cause death and alteration of the bacterial cell, including medicines that act mainly on the cell wall, cell membrane, or bacterial DNA.
Bacteriostatic agents inhibit bacterial replication without killing the organism.
Most bacteriostatic drugs act by inhibiting protein synthesis.
This distinction is not absolute since some bactericidal agents against certain organisms can only be bacteriostatic against others and vice versa.
In the case of severe infections such as endocarditis and meningitis, bactericidal agents are preferred for rapid healing.
Use of antimicrobial combinations
Antimicrobial therapy with a single agent is generally preferred, but there are cases in which a combination of 2 or more antimicrobial agents is recommended, as in the case of tuberculosis.
Synergistic activity
The synergy between antimicrobial agents results in the fact that the combined effect of agents is greater than the sum of their independent activities when measured separately.
The combination of certain β-lactams and aminoglycosides shows a synergistic activity against many gram-positive and gram-negative bacteria. It is used to treat serious infections, for which rapid death is essential.
In the case of certain streptococci, synergistic combinations can also be used to rapidly eliminate the infecting microorganism and shorten the course of antimicrobial therapy.
Prevent resistance
The use of a combination therapy provides a greater possibility that at least one drug is effective, thus preventing a resistant mutant population from emerging as a dominant strain and causing a therapeutic failure.
This principle is based on the use of combined pharmacotherapy to treat infections such as tuberculosis and the human immunodeficiency virus ( HIV ).
Since the duration of treatment is likely prolonged, resistance can arise with relative ease, coupled with the fact that in these cases, the therapeutic agents are limited.
Factors of the host
Although it is helpful for physicians to become familiar with some specific antimicrobial agents, a general approach is not appropriate in the selection of antimicrobials, and several factors of the host should be taken into account, such as:
Kidney and liver function
Because the kidney and liver are the main organs responsible for eliminating toxins from the body, including the residues of drugs.
It is essential to determine that they are functioning normally during the administration of antimicrobials.
In most cases, to prevent accumulation and toxicity in patients with reduced renal or hepatic function or issues of rapid hepatic metabolism.
This is due to the enzymatic induction due to the concomitant use of drugs such as rifampin or phenytoin; the concern is the dose to be administered.
Years
In patients at both ends of age groups, drugs operate differently due to differences in body size and renal function.
Pediatric doses of medication are usually governed by weight.
In the case of geriatric patients, the serum creatinine level and creatinine clearance should be estimated as age and weight.
Genetic variation
The genetic susceptibility to the adverse effects of antimicrobial agents is occasionally significant enough to justify testing for such variability before administering certain medications.
This is the case of the antiretroviral abacavir, which is part of the standard combination treatment for HIV infection, is associated with a life-threatening hypersensitivity reaction that can manifest itself with symptoms such as:
- Fever.
- Acne.
- Abdominal pain.
- Dyspnoea.
This reaction is significantly greater in patients with the human leukocyte antigen allele HLA-B * 5701.
Therefore, the current HIV treatment guidelines recommend the detection of this genetic susceptibility before prescribing this drug.
Pregnancy and lactation
Considerations for antimicrobial agents during pregnancy are related to both the mother and the fetus.
In the mother, it is related to high plasma volume and renal blood flow, especially in the third trimester, resulting in more rapid elimination and lower serum levels of antimicrobial agents.
Given this possibility, very high antimicrobial doses are generally not recommended during the third trimester of pregnancy.
In the developing fetus, many antimicrobial agents can be teratogenic or toxic to him.
Human studies on the safety of many antimicrobial agents during pregnancy and lactation are limited, and antimicrobial agents should be prescribed with great caution during these periods.
Allergy or intolerance
Information should generally be obtained in the evaluation when the medical history of the patient is made, to adverse reactions due to allergy or intolerance to antimicrobials, to define the treatment of the infection.
Oral vs. intravenous therapy
Hospitalized patients with severe infections are often treated with intravenous antimicrobial therapy, but patients with mild to moderate conditions and normal gastrointestinal function are candidates for oral treatment.
On the other hand, patients who are initially treated with parenteral therapy can safely switch to oral antibiotics when clinically stable.
But in the case of more severe infections, such as infectious endocarditis and central nervous system infections such as Meningitis, a switch to oral therapy is unreliable and is usually not recommended.
Resistant bacteria
The WHO published a list of bacteria resistant to current treatments.
Classifying them into three groups called:
- Priority pathogens.
They cause infections in the blood, lungs, brain, and urinary tract. They can be deadly: Acinetobacter baumannii (with resistance to carbapenems), Pseudomonas aeruginosa (with resistance to carbapenems), Enterobacteriaceae (with resistance to carbapenems).
- Pathogens of high and medium priority.
In these bacteria, drug resistance increases and causes common diseases such as gonorrhea or food poisoning.
Of high priority we have:
- Enterococcus faecium (with vancomycin resistance).
- Staphylococcus aureus (with methicillin resistance, has intermediate sensitivity and resistance to vancomycin).
- Helicobacter pylori (with resistance to clarithromycin).
- Campylobacter sp. (With resistance to fluoroquinolones).
- Salmonellae (with resistance to fluoroquinolones).
- Neisseria gonorrhoeae (with resistance to cephalosporin, resistant to fluoroquinolones).
Of medium priority:
- Streptococcus pneumonia (without sensitivity to penicillin).
- Haemophilus influenzae (with resistance to ampicillin ).
- Shigella spp. (With resistance to fluoroquinolones).
