Antibiotics: therapeutic importance and perspectives for the discovery and development of new agents. There is a continuous need for antibiotics, mainly with new mechanisms of action, since infectious diseases represent the second major cause of death in the world and bacteria resistance levels are high. This review describes the contribution of microbial natural products for the development of the major antibiotic classes, the mechanisms of action of current antibiotics, some modern approaches involving genetic tools for the discovery and development of new antibiotics from microbial products and antibiotics in clinical trials. Keywords: microbial natural products; drug discovery; antibiotics. Figura 1.

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NCBI Bookshelf. Asif Noor ; Shailesh Khetarpal. Authors Asif Noor 1 ; Shailesh Khetarpal. Anaerobic bacteria differ from aerobic bacteria in their oxygen requirement. Oxygen is toxic to anaerobes which can be explained by the absence of enzymes in the anaerobes of catalase, superoxide dismutase, and peroxidase enzymes.

Anaerobes are fastidious organisms and are difficult to grow if proper collection and culture methods are not used. The diagnosis requires clinical suspicion and proper microbiological identification.

Obligate aerobes which required oxygen as a terminal electron acceptor and do not have any other source of energy, such as fermentation. The obligate anaerobes can further be subdivided into 2 types based on a percentage of oxygen that can prove toxic.

Significant members of this family are Clostridium difficile which causes C. Clostridium perfringens which causes gas gangrene or soft tissue infections. Propionibacterium : This species is part of the normal flora of skin and mucosa.

The most significant member of this family is Propionibacterium acne which plays a role in the pathogenesis of acne vulgaris. Bifidobacterium : This is normal flora of intestinal tracts. Lactobacillus: These organisms are also normally found in the GI tract and can be recovered from numerous food products.

Peptococcus and Peptostreptococcus : These anaerobes are part of the mouth, GI tract, upper respiratory tract, and urogenital tract, as well as the skin.

They can be pathogenic and cause numerous infections such as chronic otitis media, chronic sinusitis, aspiration pneumonia, pelvic inflammatory disease including tube-ovarian abscesses. These organisms are most commonly the cause of intra-abdominal infections particularly abscesses.

Majority of these abscesses are mixed infections. They can also cause extra-abdominal infections such as aspiration pneumonia, brain abscesses, among others. In children, they are frequently associated with head and neck infections such as peritonsillar abscesses, retropharyngeal abscesses as well as perineal or perianal infections such as a pilonidal abscess.

Veillonella: Occasionally associated with abdominal abscesses and aspiration pneumonia in children. The colonization with anaerobes varies with age, organ site, and environmental factors. The site and the extent of infection are based on the virulence factors of the organism and host immunity.

Serious infections are seen in the immunocompromised host. The approach to anaerobic infections includes the identification of predisposing factors.

The clinicians should obtain an anaerobic culture when suspicion of anaerobic infection is present. Head and neck infection: Anaerobes are commonly implicated in dental infections such as dental abscesses, gingivitis, and periodontitis.

Exam findings of dental caries or poor dentition are usually present. Anaerobes are also implicated along with other aerobes in suppurative infections of retropharyngeal abscess, peritonsillar abscess, cervical lymphadenitis, deep neck abscesses, and parotitis.

Lemierre syndrome is caused by jugular vein septic thrombophlebitis and metastatic emboli to the lungs and liver. The 3 anaerobes commonly isolated are Fusobacterium , Prevotella , and Bacteroides.

The same organisms are also seen in epidural infections. Over days to weeks, it results in the formation of abdominal abscesses. Abdominal abscesses are almost always mixed infections containing both aerobes and anaerobes.

The most common anaerobe implicated in abdominal infections is Bacteroides fragilis followed by Lactobacillus and Clostridium species. Anaerobes are also a common cause of liver abscesses. The common anaerobes associated are Bacteroides and Fusobacterium species. Pelvic inflammatory disease: Anaerobes are all are involved in pelvic inflammatory diseases PID. In a sexually active female with signs and symptoms compatible with pelvic inflammatory disease, empiric antimicrobial therapy against anaerobes and anaerobes is indicated.

Timely identification is important to start empiric therapy. Gas gangrene is caused by Clostridium perfringens or Clostridium septicum. It is a medical emergency which requires surgical debridement in addition to antibiotic therapy with penicillin containing antibiotic in combination with clindamycin.

For suspected cases, expert review is provided by the California Department of Health www. In an adolescent with a sore throat, neck pain, and tachycardia out of proportion to fever, Lemierre syndrome should be considered. A neck Doppler ultrasound should be done to look for thrombophlebitis of internal jugular veins and chest x-ray to look for septic emboli.

Abscesses limited to CNS, head and neck region. The abdominal region can be diagnosed with appropriate anaerobic culture. Tissue or fluid aspirate is preferred over a swab. After collection, the sample should be sent in an anaerobic transport medium, and it should be inoculated in an oxygen-free environment. Also, surgical debridement of necrotic tissue in clostridium necrotizing fasciitis is crucial in treatment.

Following are the choices:. Its activity against Gram positives is good although less reliable. Clindamycin is active against many anaerobes. Clindamycin whether administered IV or orally penetrate well into the tissue including abscesses, bones, joints.

Second-generation cephalosporin: Regarding cephalosporins, the second generation cephalosporins of cefoxitin, cefotetan, and cefmetazole are more active against Bacteroides fragilis. However, given increasing resistance, they are not recommended as empiric treatment. It is commonly used in surgical prophylaxis. Quinolones : Have good oral absorption and tissue penetration. Quinolones with activity against anaerobes include levofloxacin and moxifloxacin. Anaerobic infections are common in both outpatients and inpatients.

Because these infections can affect various organs and present in diverse ways, they are best managed by an interprofessional team. The pharmacist should review the choice of medication, drug interactions, and patient compliance and report concerns to the team. Nurses should assist with coordination of care, facilitate communication between the interprofessional team members, and assist with patient and family education.

Specialty trained nurses including medical-surgical and infection control should be involved, as needed. To access free multiple choice questions on this topic, click here. This book is distributed under the terms of the Creative Commons Attribution 4.

Turn recording back on. National Center for Biotechnology Information , U. StatPearls [Internet]. Search term. Affiliations 1 Winthrop University Hospital. Host's inability to clear secretions, for example, children with cerebral palsy are predisposed to aspiration pneumonia. Evaluation Identification of Serious Anaerobic Infections Timely identification is important to start empiric therapy.

Aerobic abscesses from Escherichia coli , Pseudomonas such as brain abscess, head and neck abscesses, lung infections, and intra-abdominal infections. Pearls and Other Issues Consider anaerobic infection if the site of suspected infection is adjacent to a normal indigenous anaerobic flora, such as the mouth, bowel, or female genital tract.

Identifying a predisposition such as obstruction, perforation, injury, the inability of the host to clear secretions, decreased blood flow to the tissue such as tissue necrosis. Tissue or purulent material is preferred over sending swabs.

Metronidazole has broad-spectrum anaerobic activity with the least resistance. Other anaerobic antibiotics include clindamycin, penicillin beta-lactamase inhibitor combination, second-generation cephalosporins, carbapenems, and quinolones. Enhancing Healthcare Team Outcomes Anaerobic infections are common in both outpatients and inpatients. In any child with clean penetrating, wound tetanus vaccination should ensue, and in cases of the contaminated wound, consideration should be made on the use of tetanus vaccine and tetanus immunoglobulins based on last tetanus vaccine.

For abdominal surgeries requiring entrance of hollow viscus, an antibiotic with anaerobic activity such as cefoxitin should be considered. Questions To access free multiple choice questions on this topic, click here. References 1. Metronidazole resistance and nim genes in anaerobes: A review. Human and Animal Bites. Pediatr Rev. Epidemiological studies on Clostridium perfringens food poisoning in retail foods. J Maxillofac Oral Surg.

Am Surg. Messbarger N, Neemann K. J Pediatric Infect Dis Soc. Ann Lab Med. J Arthroplasty. Rozhl Chir. J Am Podiatr Med Assoc.

Clostridium difficile: epidemiology, pathogenesis, management, and prevention of a recalcitrant healthcare-associated pathogen. Necrotizing fasciitis: literature review of contemporary strategies for diagnosing and management with three case reports: torso, abdominal wall, upper and lower limbs.



NCBI Bookshelf. Asif Noor ; Shailesh Khetarpal. Authors Asif Noor 1 ; Shailesh Khetarpal. Anaerobic bacteria differ from aerobic bacteria in their oxygen requirement.


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