The Microbiology Laboratory
Keith Struthers in Clinical Microbiology, 2017
By their very nature, anaerobes do not survive in the presence of oxygen, as they are unable to ‘detoxify’ O2- radicals. If several millilitres of pus is present, this should be collected. While modern transport swabs do keep a wide range of labile organisms viable, pus is the better sample. If further testing is required, for example for mycobacteria, pus is a superior specimen to process for this purpose. In most laboratories a metronidazole antibiotic disc is placed at the junction of the primary and second streak on the anaerobic blood agar plate (Figure 5.25a). Plates are incubated in an anaerobic cabinet, and examined at 48 hours. A zone of inhibition around the metronidazole disc identifies anaerobes (Figure 5.25b). Further identification is done by the testing systems described below.
Unexplained Fever In Infectious Diseases: Section 2: Commonly Encountered Aerobic, Facultative Anaerobic, And Strict Anaerobic Bacteria, Spirochetes, And Parasites
Benedict Isaac, Serge Kernbaum, Michael Burke in Unexplained Fever, 2019
Anaerobic infections may generate problems of unexplained fever and are responsible for 8 to 10% of general hospital bacteremias and 85% of suppurative brain infections.47 They are often polymicrobial in nature: the anaerobes may be associated with aerobes, especially E. coli, or with Actinomyces. Anaerobes can be allocated to one of two classes, according to their origin: (1) exogenous species — generally found in soil, but also residing in man (skin, buccal cavity, gastrointestinal tract, female genital tract). They are spore-bearing rods, virulent, extremely toxic, their principal representative being Clostridium; (2) endogenous species — nonsporing, a normal part of the body flora, and found particularly in the intestines and pelvis. Their main representative is Bacteroides fragilis. Most exogenous anaerobes cause nonfebrile diseases; a small proportion cause febrile infections: bacteremia, pulmonary, biliary, intra-abdominal and post-abortion genital infections. Clostridium bacteremia may develop in the setting of a septic surgical operation, a puerperal or post-abortum infection, an underlying neoplastic disease, or decubitus ulcers, and may have a fulminant evolution. The clinical features are high fever with chills, abdominal pain, intravascular hemolysis with oliguria or anuria, jaundice and shock. Aggressive treatment with high doses of intravenous aqueous penicillin or, in penicillin-allergic patients, clindamycin, a cephalosporin or chloramfenicol, may sometimes be life-saving.
Factors Controlling the Microflora of the Healthy Mouth
Michael J. Hill, Philip D. Marsh in Human Microbial Ecology, 2020
For cultivation, the dispersed samples are usually serially diluted in transport fluid, and aliquots are spread on various nonselective and selective agar media for incubation under different atmospheric conditions, depending on the microorganisms being cultivated.52,53 Since the majority of species are facultative or obligate anaerobes and several require carbon dioxide for growth, a gas mixture of H2/N2/CO2 is often used for incubation in an anaerobic jar or cabinet (Figure 12). A catalyst removes residual oxygen by combining it with hydrogen to form water. Some obligate anaerobes die very rapidly if exposed to oxygen. Therefore, oxygen-free conditions are essential not only for incubation, but also during the various technical procedures. Rubber-stoppered tubes may be kept anaerobic by flushing them with such a gas mixture whenever they are opened.54 If such tubes containing melted agar are rolled horizontally while cooling, they will be coated with agar on which colonies can grow (roll tubes). Alternatively, all procedures may be carried out in an anaerobic chamber (Figure 12). The recoveries of periodontal bacteria with various anaerobic techniques and culture media have recently been reviewed.55,56
Botulism Outbreak in a Regional Community Hospital: Lessons Learned in Transfer and Transport Considerations
Published in Prehospital Emergency Care, 2019
William Krebs, Terri Higgins, Martha Buckley, James J. Augustine, Bradley D. Raetzke, Howard A. Werman
Botulism is a potentially lethal condition caused by a neurotoxin released by Clostridium botulinum. This organism is a spore-forming obligate anaerobe and is ubiquitous, being isolated from variety of fruits and vegetables, soil, and marine environments. The organism produces a neurotoxin, which attacks the pre-synaptic nerve endings in affected muscles. Exposure to clostridal spores or direct exposure to toxin, via ingestion, contact with an infected wound, absorption by the lungs or parenteral injection can lead to botulism. The toxin causes various degrees of paralysis typically starting with the bulbar nerves but ultimately causing prolonged respiratory failure in its victims (1). For a comprehensive review on botulism, the reader is referred to the Centers for Disease Control (CDC) website at http://emergency.cdc.gov/agent/botulism/factsheet.asp.
Bacterial effluxome as a barrier against antimicrobial agents: structural biology aspects and drug targeting
Published in Tissue Barriers, 2022
Pownraj Brindangnanam, Ajit Ramesh Sawant, K. Prashanth, Mohane Selvaraj Coumar
In the beginning, single cells were the only living being on earth. By the process of natural selection, from a single cell to anaerobes, anaerobes to aerobes, aerobes to multicellular organisms emerged slowly.27–30 Between anaerobes to aerobes era, various races, for instance, aerotolerant, facultative, obligate bacteria, and so on have emerged.30,31 In the race for “survival of the fittest” or in the “war of defence”, microbes start competing with each other including multicellular organisms (animals including humans). Microbes use various armaments in their defense for survival. To propagate within the host, microbes first use only a few knacks like colonization, adherence and drug-metabolizing enzymes. Later on, they use other tricks such as lenience, frameshift mutations, rapid reproduction to attain the power of “resistance”, leading to better survival.
Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review
Published in Gut Microbes, 2020
Among the above stressors, oxidative stress is of critical importance as it greatly influences viability and product quality.3 The oxygen sensitivity of probiotic LAB is a major factor limiting their viability, although LAB are regarded aerotolerant anaerobes. Anaerobic bacteria lack the capability to synthesize an active electron transport chain,4 which affects their survival in aerobic environments. High oxygen levels will lead the formation of reactive oxygen species (ROS), including the superoxide anion (O2–), hydrogen peroxide (H2O2), and the highly reactive hydroxyl radical (HO·). When accumulated, ROS cause oxidative stress, which results in damage to proteins, DNA, and lipids, and even cell death.5 Therefore, preventing oxidative stress in LAB cells by using O2-tolerant LAB strains and applying adequate production and storage techniques are important to ensure high bacterial viability during storage and in the gastrointestinal tract.2,6
Related Knowledge Centers
- Anaerobic Respiration
- Bacteria
- Cellular Respiration
- Clostridium Butyricum
- Fermentation
- Obligate Anaerobe
- Oxygen
- Aerobic Organism
- Aerotolerant Anaerobe
- Facultative Anaerobic Organism