a 41-year - old male injection drug user was brought to the emergency department unresponsive , febrile and hypotensive .
initial investigations revealed a white blood cell count of 19.310/l ; urinalysis , chest x - ray and abdominal computed tomography were all unremarkable .
fluid resuscitation , vasopressor support and empirical antibiotic therapy with intravenous ( iv ) piperacillin / tazobactam , vancomycin and clindamycin were initiated . following resuscitation ,
the patient provided a vague history : he was well until the day of admission , at which time he developed a headache , severe fatigue and generalized malaise .
his medical history was significant for hepatitis c and previous episodes of bacteremia related to injection drug use .
blood cultures collected on admission grew b cereus ( four of four bottles ) and serratia marcescens .
blood cultures were persistently positive for b cereus until day 14 of admission . on day 29
, the patient developed a small antecubital abscess that was drained and cultured b cereus .
the patient received a total of six weeks of iv vancomycin and was discharged home .
nine days following the admission of case 1 , a 49-year - old man with a history of daily heroin and crystal methamphetamine injection drug use presented to hospital with confusion and agitation .
he was afebrile , with no obvious focus of infection on history or physical examination .
his medical history was significant for recently diagnosed hiv infection and hepatitis c. initial laboratory results showed a white blood cell count of 13.110/l .
blood cultures collected on admission grew b cereus and lactobacillus , and the patient was switched to iv vancomycin and ciprofloxacin .
three subsequent blood cultures were positive for b cereus ; blood cultures eventually cleared on day 14 of admission . iv vancomycin was continued for a total duration of eight weeks and the patient was discharged .
twenty days after case 1 was admitted to hospital , a 33-year - old man with a history of heroin and cocaine injection drug use presented to the emergency department with confusion .
his medical history included hepatitis c and previous episodes of methicillin - resistant staphylococcus aureus infective endocarditis , one of which necessitated a tricuspid valve replacement .
the patient left hospital against medical advice , but was called to return the following day when blood cultures returned positive for gram - positive bacilli , subsequently identified as b cereus .
repeat blood cultures were drawn and iv vancomycin therapy was initiated . only the initial blood culture ( one of two bottles ) grew b cereus , and all subsequent blood cultures were negative .
the patient received a total of two weeks of iv vancomycin and was discharged home .
the b cereus isolates from the present cluster of three cases were submitted to the british columbia public health microbiology and reference laboratory for pulsed - field gel electrophoresis ( pfge ) analysis to determine genetic relatedness .
pfge was performed for b cereus using smai restriction endonuclease for digestion and based on the parameters described by liu et al ( 5 ) .
additionally , the vancouver police department was able to provide five samples of confiscated heroin ( dry powder ) for microbiological analysis .
the samples of confiscated heroin were randomly chosen and were not related to the patients who presented to hospital .
of the five samples of heroin provided , three grew b cereus from microbiological culture .
coagulase - negative staphylococci ( three of five ) and escherichia vulneris ( one of five ) were also recovered in culture . given the preliminary findings from the pfge performed on the clinical isolates of b cereus , the organisms recovered from the heroin samples were not submitted for further genetic analysis . a common source for the cluster was not confirmed .
a 41-year - old male injection drug user was brought to the emergency department unresponsive , febrile and hypotensive .
initial investigations revealed a white blood cell count of 19.310/l ; urinalysis , chest x - ray and abdominal computed tomography were all unremarkable .
fluid resuscitation , vasopressor support and empirical antibiotic therapy with intravenous ( iv ) piperacillin / tazobactam , vancomycin and clindamycin were initiated . following resuscitation ,
the patient provided a vague history : he was well until the day of admission , at which time he developed a headache , severe fatigue and generalized malaise .
his medical history was significant for hepatitis c and previous episodes of bacteremia related to injection drug use .
blood cultures collected on admission grew b cereus ( four of four bottles ) and serratia marcescens .
blood cultures were persistently positive for b cereus until day 14 of admission . on day 29
, the patient developed a small antecubital abscess that was drained and cultured b cereus .
the patient received a total of six weeks of iv vancomycin and was discharged home .
nine days following the admission of case 1 , a 49-year - old man with a history of daily heroin and crystal methamphetamine injection drug use presented to hospital with confusion and agitation .
he was afebrile , with no obvious focus of infection on history or physical examination .
his medical history was significant for recently diagnosed hiv infection and hepatitis c. initial laboratory results showed a white blood cell count of 13.110/l .
blood cultures collected on admission grew b cereus and lactobacillus , and the patient was switched to iv vancomycin and ciprofloxacin .
three subsequent blood cultures were positive for b cereus ; blood cultures eventually cleared on day 14 of admission . iv vancomycin was continued for a total duration of eight weeks and the patient was discharged .
twenty days after case 1 was admitted to hospital , a 33-year - old man with a history of heroin and cocaine injection drug use presented to the emergency department with confusion .
his medical history included hepatitis c and previous episodes of methicillin - resistant staphylococcus aureus infective endocarditis , one of which necessitated a tricuspid valve replacement .
the patient left hospital against medical advice , but was called to return the following day when blood cultures returned positive for gram - positive bacilli , subsequently identified as b cereus .
repeat blood cultures were drawn and iv vancomycin therapy was initiated . only the initial blood culture ( one of two bottles ) grew b cereus , and all subsequent blood cultures were negative .
the patient received a total of two weeks of iv vancomycin and was discharged home .
the b cereus isolates from the present cluster of three cases were submitted to the british columbia public health microbiology and reference laboratory for pulsed - field gel electrophoresis ( pfge ) analysis to determine genetic relatedness .
pfge was performed for b cereus using smai restriction endonuclease for digestion and based on the parameters described by liu et al ( 5 ) .
additionally , the vancouver police department was able to provide five samples of confiscated heroin ( dry powder ) for microbiological analysis .
the samples of confiscated heroin were randomly chosen and were not related to the patients who presented to hospital .
of the five samples of heroin provided , three grew b cereus from microbiological culture .
coagulase - negative staphylococci ( three of five ) and escherichia vulneris ( one of five ) were also recovered in culture . given the preliminary findings from the pfge performed on the clinical isolates of b cereus , the organisms recovered from the heroin samples were not submitted for further genetic analysis . a common source for the cluster was not confirmed .
b cereus has been reported as a cause of extraintestinal infections , including those of the musculoskeletal , ocular , respiratory , cardiovascular and central nervous systems ( 6 ) .
injection drug use is often attributed as an etiological factor , with reports of cellulitis ( 4 ) , endophthalmitis and panophthalmitis ( 3,7,8 ) , and endocarditis ( 1,6,9,10 ) .
the prognosis of bacteremia and native valve endocarditis with b cereus is typically good , with prompt antibiotic therapy of adequate duration being suitable for recovery ( 2 ) .
conversely , high morbidity and mortality have been observed with prosthetic valve endocarditis , and authors of a review on the subject recommend prompt valve replacement in conjunction with iv antibiotics ( 11 ) .
no guidelines exist for treatment of invasive b cereus infections , and reports in the literature describe clinical recovery with two to four weeks of iv antibiotics for bacteremia , and four to six weeks for endocarditis ( 2 ) . published susceptibility reports describe complete susceptibility of b cereus to vancomycin , quinolones , gentamicin , carbapenems and tigecycline ; intermediate susceptibility to clindamycin , tetracycline and erythromycin ; and high - level resistance to trimethoprim / sulfamethoxazole , penicillins and cephalosporins ( 12 ) . in the present study ,
case 1 was treated with a prolonged six - week course of iv vancomycin for b cereus bacteremia because of persistently positive blood cultures for the first 14 days .
case 2 was treated for mitral valve endocarditis with an eight - week course of iv vancomycin and his blood cultures cleared over a two - week period .
although case 3 had a prosthetic tricuspid valve , there was no evidence of endocarditis and only a single initial positive blood culture .
he received a two - week course of iv vancomycin , despite the possibility that this was a culture contaminant .
all patients in the cluster shared the risk factor of injection drug use , having recently injected heroin .
b cereus infections have been sporadically associated with injection drug use , particularly with heroin .
these rare occurrences were first reported ( 9 ) and reviewed ( 1 ) in the 1970s .
b cereus , a known contaminant related to drug use , is resistant to heat and capable of surviving in harsh environments .
a report from 1983 conducted in washington , dc , found that nearly one - half of injection paraphernalia and 32% of heroin samples were contaminated with bacillus species ( 13 ) the microbial burden was significantly higher on the injection paraphernalia than the heroin itself , and brown heroin ( mainly from mexico ) was found to have a higher burden compared with white heroin ( mainly from overseas ) .
the authors speculated that heroin users experience frequent transient episodes of bacillus species bacteremia , which are rarely of clinical significance . in the literature ,
one case exists with a largely conclusive link of a b cereus infection to contaminated heroin ( 4 ) . a patient with
cellulitis provided a heroin sample , and both his wound aspirate and heroin cultured b cereus , which was found to be indistinguishable through pfge . in our cluster
possible explanations for our cluster not having a common source include increasing microbial burden of heroin in general , supported by the burden found on the randomly acquired heroin or , particularly , contaminated injection paraphernalia among users .
b cereus infections are an underappreciated cause of bloodstream infections in injection drug users , for which the treatment requires prompt identification and antibiotic coverage .
our observation of three unrelated but temporally associated cases of b cereus infection in heroin users suggests that suspicion of b cereus infection in this patient population may become increasingly warranted .
 bacillus cereus is a bacteria commonly found in nature that is most frequently implicated as the cause of gastrointestinal illness caused by ingestion of contaminated food ; however , there are also reports of extraintestinal infections , although rare . 
 this article describes three cases in which b cereus bacteremia occurred among injection drug users living in vancouver , british columbia , within a short period of time . 
 pulsed - field gel electrophoresis was performed to determine whether these three isolates were related . 
CASE PRESENTATIONS
Case 1
Case 2
Case 3
Molecular analysis
DISCUSSION
CONCLUSION