Fever is initially a natural reaction of the body to a pathogen, such as bacteria. Due to the higher temperature, the pathogens are combated more effectively. Often, however, an additional antibiotic is necessary. An antibiotic is a drug that can kill the bacteria. The antibiotic kills bacteria faster and more effectively than the immune system. Thus, the immune system can stop the defense reaction again and the fever drops again.
If the antibiotic does not work properly or if the causative agents are not bacteria but viruses, the immune system must continue to fight the pathogens and the fever persists.
Antibiotics develop their effects relatively quickly, even if a fever is present at the same time. However, when taking the antibiotics must be taken as closely as possible to the time intervals so that they can reach their full effect. In addition, the onset of action depends on the form in which the antibiotic is taken. Outside the hospital, antibiotics are usually prescribed in tablet form, as ointment or drops. As part of a hospital stay, the antibiotic can also be given through the vein, which has a better effect. Furthermore, the consumption of alcohol or dairy products may adversely affect the effect of the antibiotic.
First, it should be evaluated whether the antibiotic is taken correctly and often enough. In addition, care should be taken that it is not taken with dairy products or alcohol together ( see also: Amoxicillin and milk - is that possible?). If the correct intake is ensured and the fever persists after about three days, a doctor should be consulted to find out more. It also helps to document its exact symptoms and their course well, since these can give hints on why the antibiotic does not work.
In the adult, if a fever persists despite antibiotics for an unusually long period of time, this can have various causes. First, make sure the antibiotic was taken. Then it should be questioned whether the fever was triggered by a bacterial infection, or whether not yet another germ (eg virus or fungus) could be behind it. Then the antibiotic would not be effective.
Assuming a bacterial infection, another source of error may be choosing the wrong antibiotic. Different germs respond better or worse to certain antibiotics. Depending on whether the patient was recently hospitalized or has other risk factors (for example, a chronic illness), different bacteria may be the most likely triggers. Here the determination of the germ and its resistances can provide important information. Resistance can be another reason for fever despite antibiotics. Due to the massive use of antibiotics, bacteria develop a resistance to certain drugs. Especially in the hospital environment must always be thought of possible resistances.
Finally, when choosing the antibiotic, it must also be considered where the drug should act. For example, if there is an inflammation in the soft tissues, special antibiotics must be selected, which can penetrate well through this soft tissue, so that at the infection site also enough drug arrives. If this does not happen, the infection can spread further and the fever persists.
If a fever persists in the baby or toddler despite antibiotic therapy for more than three days, a pediatrician should be consulted. The pediatrician will then evaluate why the fever does not decrease. As with adults, possible sources of error may be the wrong intake, another non-bacterial germ, or the wrong antibiotic.
Especially in babies, this situation must be taken seriously, because they can quickly lose fluid through the fever and eventual refusal to drink and do not have many reserves. In addition, other symptoms such as skin rash, sore throat and especially neck stiffness must be taken into account. A neck stiffness speaks for an inflammation of the meninges. This dangerous, but rather rare, condition must be treated as quickly as possible with the right antibiotics. It is important that an antibiotic is selected, which also enters the spinal canal. In order to achieve a sufficient effect, the antibiotic must also be given through the vein.
Pneumonia can be caused by a variety of germs. Some are more common, others less common. In case of pneumonia, one would first administer an antibiotic, which fits the history of the patient and which is effective against the most common pathogens. If there are already special features known, such as hospital stays or a weakened immune system (for example due to a serious chronic illness), one would from the outset choose an antibiotic which has a broader spectrum of activity.
If the fever persists after the third day and worsens the general condition, treatment failure must be considered and switched to other antibiotics. In this case, the pathogen should then be determined in order to exclude that it is not a virus against which the antibiotic would be ineffective.
In a urinary tract infection, the antibiotic therapy is selected mainly on the severity of the course and then whether it is a complicated or uncomplicated inflammation - here, above all, a role, whether the urinary tract infection for the first time or more, in a woman or a Man occurs. If there are additional knocking pains in the flank, it is assumed that this is additionally an infection of the renal pelvis.
If the fever and the other symptoms persist despite antibiotic therapy, the choice of antibiotic should be reconsidered. The determination of the exact pathogen helps here, because not every antibiotic works equally well against every germ. In addition, one must always think of antibiotic resistance. Whether a germ is resistant to a particular antibiotic can be determined in the laboratory.
Otitis media should be treated with an antibiotic only in the case of very severe disease progression or in the presence of risk factors. A severe course is accompanied by a high fever and a greatly reduced general condition. The antibiotic of choice is amoxycillin. However, it is known that patients who have received amoxicillin the previous month do not respond well to the drug. This could then be the reason for the existing fever despite antibiotic. You should then immediately get another antibiotic.
In the case of middle ear infection, good ventilation via the Eustachian tube is also important. Here, for example, decongestant nasal sprays can be used or possibly enlarged pharyngeal tonsils, colloquially known as polyps, can be removed. If this does not happen, the inflammation can easily return and thus lead to a persistent fever.
Fever after an operation does not always have to speak for a bacterial infection. For example, postoperative blood clots (thromboembolisms) or large bruises trigger fever for a few days after surgery. The fever arises in this case even if the patient receives prophylactic antibiotics. Of course, fever after an operation can also speak for an infection. Often here are lung and urinary tract infections, as well as wound infections. Depending on which germ has triggered this inflammation, the prophylactically given antibiotic can be ineffective. In case of fever despite antibiotics after an operation, therefore, a cause research must be carried out to prevent dangerous complications.