ObjectiveTo investigate the positive rates of virulence genes ply, lytA and nanA in Streptococcus pneumoniae (SP) strains isolated from different sources and the pathogenesis.MethodsA total of 147 and 24 strains of SP were isolated from sputum and blood samples of hospitalized children in Tongji Hospital of Wuhan from 2015 to 2016, respectively. Such strains of SP were analyzed by automated microbial analyzer VITEK Compact-2 and confirmed by its specific gene pbp2B using regular polymerase chain reaction (PCR) method. Then PCR method was used to detect the carriers of the virulence genes ply, lytA and nanA, and calculated the fatality and hospitalization days of patients.ResultsPositive rates of virulence genes ply, lytA and nanA were 95.9%, 96.6% and 88.4% respectively for 147 strains isolated from sputum, and were 100.0%, 100.0% and 79.2% respectively for those from blood. Between the 147 children with pneumonia and 24 children with septicemia, there was no statistically significant difference in fatality [ 8.3% (2/24) vs. 0.7% (1/147), P=0.052], but there was a significant difference in length of hospital stay [(14.2±2.4) vs. (6.4±1.5) d; t=21.303, P<0.001].ConclusionsThe positive rate of SP virulence gene nanA is lower than those of ply and lytA. The positive rates of SP virulence genes ply, lytA and nanA are similar from different sources. Significant difference may be found for hospitalization days among different types of SP infections.
Hypervirulent Klebsiella pneumoniae has the characteristics of high virulence and high viscosity, which can cause pneumonia, bacteremia, liver abscess, meningitis and other diseases, and in severe cases, it can be life-threatening. At present, studies on the pathogenic mechanism of hypervirulent Klebsiella pneumoniae showed that siderophore virulence genes play an important role in it. The siderophores closely related to hypervirulent Klebsiella pneumoniae virulence mainly include aerobactin, enterobactin, yersiniabactin and salmochelin. Siderophore-related virulence genes mainly include aer, iucB, iroNB and kfuBC. This article focuses on a brief review of the role of siderophore virulence genes in the pathogenic mechanism of hypervirulent Klebsiella pneumoniae, and aims to guide infection control.
As an essential trace element for most organisms, iron is an important cofactor for various enzymes that performs key reactions. Siderophore has been considered as an important virulence factor. The cAMP receptor protein is an integral regulator, directly or indirectly involved in the regulation of siderophores-related genes in some prokaryotes and eukaryotes. This paper briefly introduces the cAMP receptor protein, and reviews the regulation of cAMP receptor protein on siderophores-related virulence genes of Klebsiella pneumoniae, Yersinia pestis, Vibrio vulnificus and Cryptococcus neoformans, in order to lay a theoretical foundation for clarifying the regulation mechanism of cAMP receptor protein on siderophores and provide a reference for pathogenic bacteria virulence control and clinical prevention.
ObjectiveTo study the distributions of virulence genes of Klebsiella pneumoniae (KP) and the distribution of hypervirulent KP (HvKP), and assess the performance of a single gene to predict HvKP.MethodsPolymerase chain reaction (PCR) method was used to analyze 12 virulence-related genes (entB, irp2, iroN, iucA, mrkD, fimH, c-rmpA, p-rmpA2, p-rmpA, wzy-K1, allS and peg-344) and drug-resistance gene blaKPC among 376 clinical KP strains collected from January 2016 to December 2018. Sequence types (ST) of KP were determined after sequencing and comparison, following the detection of 7 house-keeping genes (gapA, infB, mdh, pgi, phoE, rpoB and tonB) by PCR method. Statistical analyses were made for the distributions of virulence genes of KP and the distribution of HvKP with GraphPad Prism 8 software.ResultsAmong the 376 KP strains, the positive rates of entB, irp2, iroN, iucA, mrkD, fimH, c-rmpA, p-rmpA2, p-rmpA, wzy-K1, allS and peg-344 were 100.0%, 76.9%, 22.1%, 28.2%, 97.6%, 97.1%, 1.6%, 24.5%, 21.0%, 7.4%, 4.8% and 31.6%, respectively. The positive rates of the aforementioned virulence genes in the blaKPC-positive group (n=167) were 100.0%, 94.0%, 7.2%, 16.8%, 97.0%, 96.4%, 0.0%, 15.0%, 6.6%, 0.0%, 0.0% and 21.0%, respectively, and those in the blaKPC-negative group (n=209) were 100.0%, 63.2%, 34.0%, 37.3%, 98.1%, 97.6%, 2.9%, 32.1%, 32.5%, 13.4%, 8.6% and 40.2%, respectively; there was no statistically significant difference in entB, mrkD or fimH between the two groups (P>0.05), the positive rate of irp2 was higher in the blaKPC-positive group than that in the blaKPC-negative group (P<0.05), and the positive rates of the rest virulence-related genes were lower in the blaKPC-positive group than those in the blaKPC-negative group (P<0.05). The rate of HvKP in the blaKPC-negative group was higher than that in the blaKPC-positive group (38.3% vs. 18.0%, P<0.05). As a marker of HvKP, iucA showed high sensitivity and specificity (90.9% and 97.7%), followed by p-rmpA2 (83.6% and 100.0%) and iroN (73.6% and 99.2%). ST11 accounted for 87.4% in the blaKPC-positive group, while ST23, ST20, ST54 and ST29 were the four primary types in the blaKPC-negative group, accounting for 23.4% totally.ConclusionsDifferent virulence genes mean different distributions in KP. blaKPC-negative KP is more virulent than blaKPC-positive KP. iucA and p-rmpA2 could serve as good predicators of HvKP. Armed with extreme virulence and drug-resistance, blaKPC-positive HvKP is of great clinical concern.