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Biological Health Hazard – Anthrax-like human infection (Bacillus cereus): Florida, USA


Published Date: 2016-06-07 17:10:03
Subject: PRO/AH/EDR> Bacillus cereus, anthrax-like infection – USA (FL) human
Archive Number: 20160607.4270866

Date: June 3, 2016
Source: PLoS ONE [edited]

Anthrax toxin-expressing _Bacillus cereus_ isolated from an anthrax-like eschar
Marston CK, Ibrahim H, Lee P, et al. Anthrax toxin-expressing Bacillus cereus Isolated from an anthrax-like eschar. PLoS ONE. 2016; 11(6): e0156987. doi:10.1371/journal.pone.0156987

_Bacillus cereus_ isolates have been described harboring _Bacillus anthracis_ toxin genes, most notably _B. cereus_ G9241, and capable of causing severe and fatal pneumonias. This report describes the characterization of a _B. cereus_ isolate, BcFL2013, associated with a naturally occurring cutaneous lesion resembling an anthrax eschar. Similar to G9241, BcFL2013 is positive for the _B. anthracis_ pXO1 toxin genes, has a multi-locus sequence type of 78, and a pagA sequence type of 9. Whole genome sequencing confirms the similarity to G9241. In addition to the chromosome having an average nucleotide identity of 99.98% when compared to G9241, BcFL2013 harbors 3 plasmids with varying homology to the G9241 plasmids (pBCXO1, pBC210 and pBFH_1). This is also the 1st report to include serologic testing of patient specimens associated with this type of _B. cereus_ infection which resulted in the detection of anthrax lethal factor toxemia, a quantifiable serum antibody response to protective antigen (PA), and lethal toxin neutralization activity.

_Bacillus cereus_ infections are typically associated with foodborne illnesses, periodontal diseases, and other opportunistic diseases. However, _B. cereus_ can be associated with more severe and even fatal infections. Within the last decade, _B. cereus_ isolates associated with severe infections have been described harboring _B. anthracis_ toxin genes and/or capsule biosynthesis genes. Hoffmaster et al described the first _B. cereus_ with _B. anthracis_ toxin genes, _B. cereus_ G9241, to cause a severe pneumonia in a metal worker from Louisiana. Since that report, there have been several additional accounts of infection associated _B. cereus_ resembling G9241 isolated from severe pneumonia cases in metal workers in Texas. With the exception of the initial case from Louisiana, these infections were fatal. In addition to these isolates, Klee et al characterized 2 Bacillus isolates harboring _B. anthracis_ virulence genes, now termed _B. cereus biovar anthracis_, cultured from deceased great apes in Cote d’Ivoire and Cameroon.

In this report, we characterize a _B. cereus_ isolate, BcFL2013, cultured from a swab of a facial lesion resembling an anthrax eschar from a 70 year old Florida resident. The patient was hospitalized and received antibiotic treatment but fully recovered. The Florida Department of Health Laboratory performed the B. anthracis-specific polymerase chain reaction assay (LRN PCR) on the isolate from the skin lesion and detected one of the _B. anthracis_ plasmids, pXO1. The isolate was then forwarded to the Centers for Disease Control and Prevention (CDC) for further characterization. In addition to isolate characterization, plasma and serum samples from the patient were collected and forwarded to the CDC for serological testing.

To date, 6 _B. cereus_ isolates, associated with human infections, have been described containing _B. anthracis_ toxin genes: 4 isolates (G9241 from LA, 03BB87, 03BB102, Elc2) from metal workers in Texas and Louisiana with respiratory infections and 2 isolates (laboratory-acquired G9241 infection from Illinois and BcFL2013) resulting in cutaneous infections. In addition to these, the CDC received a _B. cereus_ isolate harboring _B. anthracis_ toxin genes (LA4726) from Louisiana in 2007 from a pneumonia patient who was also a metal worker (data not shown). Of these isolates, 4 (03BB87, LA4726, G9241, and BcFL2013) had identical subtypes (ST 78) by MLST. The 2 remaining metal worker isolates (03BB102 and Elc2) were MLST subtypes ST 11 and ST 108, respectively. All 7 metal worker isolates had sequence homology to _B. anthracis_ toxin genes (pagA, lef, and cya) on pXO1. Only 1 isolate, 03BB102, had homology to the _B. anthracis_ capsule genes (cap operon) on the pXO2 plasmid; however, it was not observed to produce a polyglutamate capsule like _B. anthracis_ [3]. Phenotypically, all of the _B. cereus_ isolates from the metal workers produced a capsule (either hyaluronic acid and/or exo-polysaccaride) although they differed in composition from the _B. anthracis_ capsule. The BcFL2013 isolate described here has one of the capsule operons associated with G9241, hasACB. This would suggest that BcFL2013 produced, at very least, a hyaluronic acid capsule, but further studies would be required to determine the exact capsule composition.

In addition to these isolates, 2 _B. cereus_ isolates have been isolated from non-human primates in Cote d’Ivoire and Cameroon (CI and CA) which harbor _B. anthracis_ virulence genes and have been described as _B. cereus biovar anthracis_ [6]. Unlike the strains from the metal workers, the _B. cereus biovar anthracis_ isolates harbor both _B. anthracis_ virulence plasmids (99-100% identity). Additionally, the CA and CI isolates have a non-functional plcR gene, a transcriptional regulator, due to an insertion at the 3′ end of the gene [6]. _B. anthracis_ also has a non-functional plcR gene resulting from of a nonsense mutation in the gene. Conversely, BcFL2013 has a predicted full length plcR protein with 100% identity to that of G9241.

Phenotypically, the CA and CI isolates differ from _B. anthracis_ as they are motile, gamma-phage resistant, and, in some cases, penicillin-resistant and, unlike most _B. cereus_, are non-hemolytic on blood agar. [6]. The CA and CI isolates differ from the other _B. cereus_ isolates in that they express both a hyaluronic acid and polyglutamate capsules. By MLST, the CA and CI isolates, along with 2 metal worker isolates (03BB102 and Elc2), are more closely related to _B. anthracis_. It is of interest that, to date, the _B. cereus biovar anthracis_ isolates have not been cultured from humans. Whether this is the result of virulence differences, decreased human exposure, or an artifact of limited diagnostic capacity in regions where these strains have been detected remains to be determined.

This is the first report of a _B. cereus_ isolate harboring _B. anthracis_ toxin genes associated with a naturally occurring cutaneous infection. However, as previously mentioned, there was a laboratory-acquired cutaneous infection associated with _B. cereus_ G9241 in 2011. Unlike the previous cases associated with these types of _B. cereus_ isolates, the Florida patient did not have any previous history of metal work. The patient had recent contact with apparently healthy horses but this is not a known risk factor for infection. Previous cases caused by these types of isolates occurred in Texas and Louisiana, neither of which was visited by this patient recently. It remains unknown how the Florida patient became infected.

In addition to being the 1st report of a naturally acquired _B. cereus_ infection resembling cutaneous anthrax, this is the 1st report of demonstrated LF toxemia and a detectable humoral response to the toxin with in vitro toxin neutralization activity from an infection caused by a _B. cereus_. However, Brezillon et al showed that the _B. cereus_ biovar anthracis isolates expressed both _B. anthracis_ toxin and capsule genes in animal models. Previous reports of serious and fatal _B. cereus_ infections did not include serologic testing of patients to determine if the toxin genes were expressed in vivo resulting in toxemia. These methods have been used successfully to detect toxin and antibody response in systemic and cutaneous anthrax cases. This case demonstrates that _B. anthracis_ toxin genes are not only present but are also expressed in vivo and, in this case, associated with the clinical presentation resembling an anthrax eschar.

communicated by:
ProMED-mail from HealthMap Alerts

[The more carefully one looks the more likely one is to find. But in routine anthrax diagnoses if the colonies look like _B. cereus_ they get tossed. To get around this traditional act, if it clinically looks like “anthrax” do a quick plasmid DNA check. And any lesions need to be treated aggressively and remove the toxin filled fluids. – Mod.MHJ

A HealthMap/ProMED-mail map can be accessed at:]

See Also


Bacillus cereus, anthrax-like infection – USA (02) (X) discussion 20110816.2475
Bacillus cereus, anthrax-like infection – USA: (TX) publication 20110815.2470
Anthrax – USA (04): (MN) alert 20110812.2441
Anthrax – USA (03): (MN) 20110811.2437
Anthrax – USA (02): (MN) 20110810.2431

Bacillus cereus skin infections, 2004 – USA (GA) 20051209.3546

Bacillus cereus endophthalmitis – Italy (02) 19980507.0892
Bacillus cereus endophthalmitis – Italy 19980507.0884

A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

Category A – Bio-weapon Agents

Category A pathogens are those organisms/biological agents that pose the highest risk to national security and public health because they can be easily disseminated or transmitted from person to person; result in high mortality rates and have the potential for major public health impact; might cause public panic and social disruption, and require special action for public health preparedness. — National Institutes of Health


Anthrax is a high-priority agent and poses a high risk to national security, it can be easily transmitted and disseminated, result in high mortality, has potential major public health impact, may cause public panic, or require special action for public health preparedness.

Bacillus anthracis (anthrax) is a non-contagious disease caused by the spore-forming bacterium Bacillus anthracis. An anthrax vaccine does exist but requires many injections for stable use. When discovered early, anthrax can be cured by administering antibiotics (such as ciprofloxacin).[11] Its first modern incidence in biological warfare were when Scandinavian “freedom fighters” supplied by the German General Staff used anthrax with unknown results against the Imperial Russian Army in Finland in 1916.[12] In 1993, the Aum Shinrikyo used anthrax in an unsuccessful attempt in Tokyo with zero fatalities.[8] Anthrax was used in a series of attacks on the offices of several United States Senators in late 2001. The anthrax was in a powder form and it was delivered by the mail.[13] Anthrax is one of the few biological agents that federal employees have been vaccinated for. The strain used in the 2001 anthrax attack was identical to the strain used by the USAMRIID.[14] -–Wikipedia

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