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Double anaerobic coverage is poor practice. Credit: FutureLearn

Double Anaerobic Coverage: What does it mean: Is it necessary?

Antimicrobial stewardship is an entity that is still in its ‘infancy’ in many African clinical settings. Healthcare providers should step up and have it incorporated into our day-to-day practice to curb the ever-growing threat of antimicrobial resistance, which is a global threat that requires a global solution. Redundant anaerobic coverage takes up almost 20% of the antimicrobial stewardship interventions. We term it double anaerobic coverage, and today’s article, the first of its kind in the new, distinct article series on antimicrobial stewardship, tackles the necessity of this habit if any. Let’s get started.

Anaerobic microbes are normal flora of the oral cavity and the gastrointestinal tract. Anaerobic organisms found in the mouth are mostly gram-positive and include Peptococcus and Peptostreptococcus spp. On the other hand, most of the clinically significant anaerobic flora in the intestinal tract are gram-negative bacilli and include Bacteroides fragilis, Prevotella melaninogenica, and Fusobacterium spp.

Most oral antimicrobial agents have excellent coverage for gram-positive anaerobes in the oral cavity. It isn’t the case for the gram-negative bacteria found in the intestinal tract.

Various infectious conditions like aspiration pneumonia, intra-abdominal infections, diabetic foot ulcer infection, and pelvic inflammatory disease, require coverage of the anaerobic organisms. They are common causative agents in such conditions. Clinicians must use the antimicrobials with proven anaerobic activity to help curb such infections.

Antimicrobial agents with good to excellent anaerobic activity include;
-amoxicillin/clavulanate (Amoxiclav),
-imipenem, and

We define double anaerobic coverage as the use of any combination of the agents listed above. No clinical guidelines in any country around the globe recommend such a vice. All the available susceptibility and clinical data do not support this practice.

Double anaerobic coverage potentiates the risks for drug toxicity, and no single trial has shown that giving a patient two antimicrobial agents that have anaerobic bacteria provides better outcomes.
All the above agents have excellent activity against gram-positive anaerobic bacteria. Take a look at a few examples of conditions that could require coverage against the gram-negative anaerobes of the intestinal tract.

Related article: Understanding Clinical Research: Behind the statistics.

Amoxiclav, clindamycin, or moxifloxacin are the drugs of choice in aspiration pneumonia and pneumonitis. In aspiration pneumonia, the organisms of interest are those that reside in the oral cavity and a few from the intestinal tract. Surprisingly, much as aspiration pneumonitis occurs due to aspiration of gastric contents, in many cases, no organism is implicated.

Metronidazole is the anaerobic agent of choice when combined with antimicrobial agents that lack anaerobic activity of clinical significance.

We reserve drugs like piperacillin/tazobactam or carbapenems for severe cases of intra-abdominal infections.

Prescribing piperacillin/tazobactam with metronidazole to a patient with such an infection is wrong. It leads to the misuse of one of the two drugs due to redundancy.

Pelvic inflammatory disease is commonly due to Neisseria gonorrhoeae and Chlamydia trachomatis – other pathogens can also cause the condition. These include anaerobes;
-Gardnerella vaginalis,
-Haemophilus influenzae,
-enteric gram-negative bacilli,
-Streptococcus agalactiae,
-Mycoplasma hominis,
-Mycoplasma genitalium, and
-Ureaplasma urealyticum.
It means that treatment for a pelvic inflammatory disease should ideally target these organisms also.

No clinical data have shown that double anaerobic coverage in pelvic inflammatory disease leads to better clinical outcomes or microbiologic cure rates, and therefore, we do not recommend it.

Do not combine Ampicillin/sulbactam and metronidazole. Ampicillin/sulbactam and doxycycline is an acceptable choice. Check with your national clinical guidelines and get well acquainted with the guidelines for the management of pelvic inflammatory disease.
There are two exceptions: we can combine metronidazole with other similar antibiotics. The same can happen for clindamycin use in managing necrotizing fasciitis.

In a nutshell, prescribing multiple antimicrobial agents is proven to be unnecessary and potentiates the risks of drug toxicities in patients as well as contributing to redundancy that can initiate antimicrobial resistance. Curbing the practice of double anaerobic coverage begins with every clinician understanding the clinical practice guidelines like our Uganda Clinical Guidelines, and revising the various aspects of pharmacology through continuous medical education.

We can all be antimicrobial stewards. Enrol for an antimicrobial stewardship course for free at FutureLearn or Coursera.


Dr A. M. Ssekandi is a medical officer, researcher, content creator, author, and founder of He does private practice with a public touch. He is a certified digital marketer. He has earned certificates in Understanding Clinical Research and Writing in Sciences from the University of Cape Town and Stanford University respectively. He also has a certificate of Good Clinical Practice from

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