Department of Microbiology, Prathima Institute of Medical Sciences, Karimnagar, India
Receaved date: Apr 04, 2016; Accepted date: Apr 05, 2016; Published date: Apr 11, 2016
Citation: Kandi V (2016) Clinical Significance of Bacillus Species Other than Bacillus anthracis. J Med Microb Diagn 5:e130. doi: 10.4172/2161-0703.1000e130
Copyright: © 2016 Kandi V, This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Visit for more related articles at Journal of Medical Microbiology & Diagnosis
Gram positive aerobic or facultatively anaerobic spore forming gram positive bacilli were first identified by Christian Gottfried Ehrenberg in 1885 and were later classified by Ferdinand Cohn in to a separate genus Bacillus . Aerobic spore forming gram positive bacteria are commonly referred to as ASB’s and includes members of Bacillus spp which are basically saprophytes living as thermophiles, psychrophiles, acidophiles, alkaliphiles and halophilies exhibiting survival in versatile environmental conditions (B acidophilus , B thermophilus , B halodurans, B alcalophilus and B coagulans ). There are around 260 species of the genus Bacillus, prevalent worldwide showing both molecular and physiological diversity. Among this group of bacteria, there are certain members responsible for accidental and opportunistic human infections [2,3]. Few among the Bacillus spp, infect animals that include B anthracis and B larvae, B lentimorbus, B popilliae, B sphaericus and B thuringiensis infect invertebrates (insects). Human infections with Bacillus anthracis , although is not rare, the cause of concern now is the increasing reports of human infections with other Bacillus spp like the B cereus , B subtilis and B licheniformis , B alvei , B brevis , B circulans , B coagulans , B macerans, B pumilus , B sphaericus and B thuringiensis . Bacillus spp are widely recognized for their utility as biological controls in clinical microbiology laboratories where the spores of Bacillus stearothermophilus are used to determine the efficacy of sterilization by autoclave and hot air oven. It should also be noted that there are a few antibiotics which are extracted from Bacillus spp (Bacitracin, polymixin and gramicidin were extracted from B subtilis, B polymyxa and B brevis respectively). Bacillus spp are also used to extract enzymes which can tolerate high temperatures (B thirungenesis ) required for performing molecular procedures like the polymerase chain reaction (PCR). B amyloliquefaciens is another member which is used to produce natural antibiotic substance, a ribonuclease. In fact Bacillus spp have been in high demand for their medicinal, agricultural, pharmaceutical and industrial applications .
Human infections by Bacillus spp are infrequently reported in literature barring anthrax. The major drawback for the inadequate reporting of Bacillus spp infections by clinical microbiology laboratories is the fact that most of these bacteria are saprophytic and their isolation in human clinical specimens is ignored as laboratory contaminants as shown in Figure 1. Bacteraemia, endocarditis, wound infections, infections of the eyes and ears, respiratory tract infections, infections of the urinary and gastrointestinal tract, food poisoning and meningitis are a few clinical conditions wherein Bacillus spp have been isolated [5-7]. Since not all human infections are caused among the immunocompetent individuals, Bacillus spp other than B anthracis could well be recognized as opportunistic pathogens in immunocompromized and debilitated individuals . Among the many predisposing factors responsible for human infections with Bacillus spp other than B anthracis , chronic alcoholism, presence of intravascular devices, intravenous drug abuse and trauma have been noted as significant .
Laboratory identification of Bacillus spp includes certain biochemical and physiological properties such as ability to grow anaerobically, growth at temperatures above 50°C, growth in 7% sodium chloride, motility, catalase production, presence of parasporal bodies and lipid globules in protoplasm, citrate utilization, nitrate reduction, ability to hydrolyze casein and starch, fermentation of glucose and propionate utilization. Barring Bacillus anthracis and Bacillus cereus (Proteinaceous lethal toxin causes necrosis of skin and mucus cells and also accumulation of fluid in the intestines), the virulence determinants of other Bacillus spp involved in human infections have not been yet identified . Recent research has attempted to identify the mechanisms by which Bacillus cereus evades immune response and cause human infection .
Human infections with Bacillus cereus have been frequently reported in literature and most infections were among debilitated patients including the hospitalized patients undergoing dialysis, Paediatric age patients and individuals suffering from haematological malignancies [11-20]. Infection of B pumilus in an otherwise immunocompetent child should be considered as a cause for serious concern . Identification of gram positive aerobic spore forming bacilli to the species level, assessing the pathogenic potential of such bacteria and interpreting the antimicrobial susceptibility testing results against commonly used antibiotics is the need of the hour.
In conclusion it must be understood that although Bacillus species other than B anthracis have been rarely associated with human infections, and that many clinical microbiology laboratories ignore these bacteria as laboratory contaminants, careful clinical and laboratory consideration is required to evaluate the actual role of these bacteria in causing human infections to effectively manage the patients.
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals