under the microscope
By Rodney E . Rohde , PhD , MS , SM ( ASCP ) CM SVCM , MBCM , FACSc
Sounding the Alarm About Burkholderia spp .
Burkholderia is a genus of Proteobacteria whose pathogenic members include a diverse group of species responsible for several dangerous and often deadly infections . Unfortunately , this group of bacteria can be difficult to isolate and differentiate in the typical clinical microbiology laboratory . Examples from this genus include the Burkholderia cepacia complex ( Bcc ), which attacks humans and Burkholderia mallei , responsible for glanders , a disease that occurs mostly in horses and related animals .
Burkholderia pseudomallei , the causative agent of melioidosis and a recent multi-state investigation of non-travel associated Burkholderia pseudomallei infections in four patients : Georgia , Kansas , Minnesota , and Texas — 2021 via Centers for Disease Prevention and Control ( CDC ) Health Alert Network ( CD- CHAN-00448 , August 9 , 2021 ). Lastly , Burkholderia cepacia , an important pathogen of pulmonary infections in people with cystic fibrosis . This group is known for antibiotic resistance and a high mortality rate from their associated diseases , B . mallei and B . pseudomallei are considered to be potential biological warfare agents , targeting livestock and humans .
As many of you know , I have discussed many forms of antimicrobial resistance ( AMR ) in this column . Surfaces and biofilms intersect with AMR . Burkholderia research focused on interbacterial signaling has shown that contact-dependent growth inhibition plays a significant role in mediating cell-to-cell communication specifically in B . thailandensis . During this type of interaction , bacteria release protein toxins in the environment . Cells with a corresponding protective protein ( usually bacteria of the same strain ) are not inhibited to grow or die . Lastly , recipient cells that have the corresponding protein then undergo changes to gene expression and phenotype which advances community formation of biofilms . Unfortunately , this occurs even if the recipient cell was not of the same bacterial strain showing the critical importance this genus can have in the environment .
For this column , I will focus on B . pseudomallei and the recent outbreak in four states . In my next column ( October ), I will focus on the B . cepacia complex ( Bcc ) as it relates to outbreaks to a dangerous contaminant in water-based pharmaceutical products .
In a recent CDC Health Alert Network , four cases of melioidosis from Georgia , Kansas , Minnesota and Texas were identified and characterized . The first case ( fatal ) identified in March 2021 occurred in Kansas . The second and third cases , both identified in May 2021 in Minnesota and Texas , were hospitalized for extended periods of time before being discharged to transitional care facilities . The most recent case died in the hospital and was identified post-mortem in late July 2021 in Georgia . All cases had no history of traveling abroad from the United States . Melioidosis signs and symptoms are varied and nonspecific , and may include pneumonia , abscess formation , and blood infections .
All four melioidosis cases initially presented with symptoms ranging from cough and shortness of breath to weakness , fatigue , nausea , vomiting , intermittent fever , and rash on the trunk ,
abdomen , and face . Two cases , one fatal , had several risk factors for melioidosis , including COPD and cirrhosis . The other two cases had no known risk factors for melioidosis . Genomic analysis of the strains strongly suggests a common source ( e . g ., imported product or animal ). The source is unknown to date despite environmental sampling , serological testing , and family interviews .
Importantly , B . pseudomallei may be misidentified by some automated identification methods in laboratory settings . Recommendations from CDC include :
● Consider melioidosis diagnosis in patients with a compatible illness , even if they do not have a travel history to a disease-endemic country .
● Culture of B . pseudomallei from any clinical specimen is considered diagnostic for melioidosis . Ideal specimens for culture include blood , urine , throat swab , and , when relevant , respiratory specimens , abscesses , or wound swabs .
● When ordering specimen cultures to diagnose melioidosis , advise the laboratory that cultures may grow B . pseudomallei , and that appropriate laboratory safety precautions should be observed by the laboratory personnel .
● Laboratory testing involving automated identification algorithms ( e . g ., MALDI-TOF , 16s , VITEK-2 ) may misidentify B . pseudomallei as another bacterium . The isolate from the Texas case was initially misidentified as B . thailandensis by MALDI-TOF . Consider re-evaluating patients with isolates identified on automated systems as Burkholderia spp . ( specifically B . cepacia and B . thailandensis ), Chromobacterium violaceum , Ochrobactrum anthropi ; and , possibly , Pseudomonas spp ., Acinetobacter spp ., and Aeromonas spp .
● Treat melioidosis with IV antibiotics ( e . g ., ceftazidime or meropenem ) for at least two weeks . Depending on the response to therapy , IV treatment may be extended for up to eight weeks . Intravenous treatment is followed by oral trimethoprim-sulfamethoxazole ( TMP / SMX ) for three to six months to prevent relapse . Amoxicillin / clavulanic acid can be used in persons with a contraindication to , or who cannot tolerate , TMP / SMX . 5
● If B . pseudomallei is identified or an organism is suspicious for B . pseudomallei , contact your state or local public health department immediately . The health department can facilitate forwarding the isolate for confirmation to the closest reference laboratory and initiate a public health investigation .
Rodney E . Rohde , PhD , MS , SM ( ASCP ) CM SVCM , MBCM , FACSc , serves as chair and professor of the Clinical Laboratory Science Program at Texas State University . Follow him on Twitter @ RodneyRohde / @ TXST _ CLS , or on his website : http :// rodneyerohde . wp . txstate . edu /