Discussion and Conclusions
Yersinia regensburg belongs to the Enterobacteriaceae family. Yersinia
regensburg is mainly distributed in well water and also exists in insect
intestinal flora. It can infect humans and has been isolated from human
respiratory tract, wounds, blood, urine and feces. This bacterium is
described as a gram-negative enterobacteria, without endospores, and
possessing peripheral flagellar movement. [1-3] There are
biochemical similarities between Y. regensburgei and H. alvei, which can
easily be misidentified by automated systems. It has been found that Y.
regensburgei has its own unique characteristics. It cannot produce
hydroxyproline amidase, tripeptidase or proline deaminase due to its
weak catalase positive. Stoke et al. used a series of parameter tests to
distinguish between Y. regensburgei and H. alvei. These parameters
include hydroxyproline amidase, maltosidase, tripeptidase, proline
deaminase, and catalase. Reaction, Voges-Proskauer test and fermentation
test of glycerol, melibiose and inositol [4]. According to reports,
the Phoenix instrument can accurately identify Regensburg yeast through
key tests of citrate utilization and melibiose fermentation. [6] But
the detection rate of Yersinia Regensburg did not increase as expected,
partly because of different commercial systems. [5,8]
The development of sequencing omics provided a new and powerful method
for identifying bacterial species. 16S rRNA gene sequencing is also very
useful in bacterial classification. Based on whole genome sequencing
analysis, Desiree J et al. obtained more detailed structure and function
information of Y. regensburgei. [18] By combining data, the
advantages of these technologies can be used to improve the accuracy of
identification.
However, due to the high similarity, many researchers have encountered
resolution problems at the genus and/or species level in
Enterobacteriaceae through 16s rRNA sequencing. [11] MALDI-TOF MS is
based on the analysis of protein profiles and has been used in the
identification and separation of strains in clinical microbiology
laboratories. Its accuracy rate is higher than that of conventional
bacterial culture methods. [10] The technique matrix-assisted laser
desorption ionization–time-of-flight mass spectrometry is considered to
be a promising alternative to the expensive and time-consuming 16s rRNA
sequencing method, which has high resolution capability for bacterial
strains that are difficult to distinguish. We reported for the first
time a case of Yersinia regensburgh infection with no underlying disease
and an immunocompetent host, and reviewed the relevant literature. The
main details described in these reports are summarized in Table 2. This
bacteria can be cultured using standard culture methods.
[6-8,12-15], most Yersinia regensburg infections occur in patients
with comorbidities such as chronic kidney disease [13] -15],
high-dose steroids [6,15] , Liver disease [6,12] and diabetes.
[14-15] Patients without underlying diseases are rarely infected
with Yersinia regensburg. [16] Almost all cases occurred in hot and
humid areas, and our report is no exception. At the same time, cases of
Yersinia regensburgh infection were relatively rare, and fewer infected
hosts were immunocompetent. At present, only one case Y. regensburgei
infected was an immunocompetent host, and the infection after craniotomy
causes postoperative secondary osteomyelitis [20]. In general, Y.
regensburgei causes life-threatening infections in immunocompromised
individuals, especially those infected with human immunodeficiency virus
(HIV), immunosuppressive therapy, and organ transplant recipients.
[6-8] Other possible risk factors include alcohol abuse. [12] In
this case, the laboratory indicators HbA1c, RF negative, ESR, and IgG
levels proved that the patient was an immunocompetent host. Stock and
colleagues [4] proved that Y. regensburgei possesses the amp C gene
and highly inducible β-lactamase, and is inherently resistant to
azithromycin and some β-lactam antibiotics. AmpC β-lactamase gene
(blaYOC-1) and a conjugating plasmid (pYRW13-125) are present in Y.
regensburgei W13. These plasmids confer resistance to multiple
antibiotics, including tetracycline, ampicillin (chloramphenicol and
florfenicol), and streptomycin. [19] While cefoperazone/sulbactam
and levofloxacin still have ability to kill Y. regensburgei, the patient
in this study were successfully treated with these antibiotics.
However, there is not enough information to fully understand the
pathogenesis and resistance mechanisms of Yersinia regensburg. Although
Y. regensburgei can infect immunocompromised hosts, it was worth noting
that these immunocompromised hosts suffered tissue damages. When the
body’s immune system is involved in the repair of tissue damage, its
antibacterial immune response may be weakened [21]. Therefore, the
prerequisite for Y. regensburgei infection may be still immune
abnormality.
In summary, in this case, this patient had no underlying diseases and no
systemic symptoms such as fever and chills. Agricultural activities and
stab wounds may be related to Yersinia Regensburg infection. The main
cause of chronic non-healing wounds was deep wood thorns. Wound healing
is also closely related to immediate debridement, abscess drainage and
wound care. Cooperation between clinical microbiology laboratories and
surgeons is essential for early diagnosis of Yersinia regensburg,
antibiotic selection, and surgical debridement.