Central nervous system infection caused by vancomycin-intermediate Staphylococcus aureus (SCCmec type IV, ST8)

Treatment of Intracranial Infection Caused by Methicillin-Resistant Staphylococcus epidermidis with Linezolid Following Poor Outcome of Vancomycin Therapy: A Case Report and Literature Review

The pharmacokinetic/pharmacodynamic (PK/PD) parameter for evaluating the efficacy of vancomycin is now recommended to target an AUC/MIC (area under the curve, AUC; minimum inhibitory concentration, MIC) ratio of 400 to 600, and trough concentration should not be used as a substitute. We report a case of intracranial infection caused by methicillin-resistant Staphylococcus epidermidis (MRSE), which was sensitive to vancomycin (MIC=2µg/mL) and linezolid (MIC=4µg/mL). The trough concentration of vancomycin in serum was 18.3 µg/mL, and the vancomycin concentration in CSF was 5.0 µg/mL, all within normal range. However, the AUC/MIC ratio was calculated to be 125 mg·h·L^-1, unable to reach target AUC/MIC. Vancomycin was replaced with linezolid after 36 days of treatment due to poor outcome, and the patient was eventually cured. Further, 23 cases of intracranial methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-resistant coagulase-negative Staphylococcus (MRCoNS) infections were reported, of which 1 case with MRSA had a vancomycin MIC of 1 µg/mL, while the remaining 22 cases had vancomycin MICs >1 µg/mL. The linezolid-containing regimen was used after drug susceptibility results or if the initial treatment failed, leading to recovery in 19 patients, microbial clearance in 3 patients, and treatment failure in 1 case. In conclusion, vancomycin dosing should be based on AUC-guided dosing and monitoring. When the vancomycin MIC of MRSA/MRCoNS is >1 µg/mL, the target AUC/MIC may not be achieved. In such cases, linezolid can effectively be considered as a good alternative to vancomycin.

Global prevalence and distribution of vancomycin resistant, vancomycin intermediate and heterogeneously vancomycin intermediate Staphylococcus aureus clinical isolates: a systematic review and meta-analysis

Vancomycin-resistant Staphylococcus aureus (VRSA), Vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) are subject to vancomycin treatment failure. The aim of the present study was to determine their precise prevalence and investigate prevalence variability depending on different years and locations. Several international databases including Medline (PubMed), Embase and Web of Sciences were searched (data from 1997 to 2019) to identify studies that addressed the prevalence of VRSA, VISA and hVISA among human clinical isolates around the world. Subgroup analyses and meta-regression were conducted to indicate potential source of variation. Publication bias was assessed using Egger's test. Statistical analyses were conducted using STATA software (version 14.0). Data analysis showed that VRSA, VISA and hVISA isolates were reported in 23, 50 and 82 studies, with an overall prevalence of 1.5% among 5855 S. aureus isolates, 1.7% among 22,277 strains and 4.6% among 47,721 strains, respectively. The overall prevalence of VRSA, VISA, and hVISA before 2010 was 1.2%, 1.2%, and 4%, respectively, while their prevalence after this year has reached 2.4%, 4.3%, and 5.3%. The results of this study showed that the frequency of VRSA, VISA and hVISA after 2010 represent a 2.0, 3.6 and 1.3-fold increase over prior years. In a subgroup analysis of different strain origins, the highest frequency of VRSA (3.6%) and hVISA (5.2%) was encountered in the USA while VISA (2.1%) was more prevalent in Asia. Meta-regression analysis showed significant increasing of VISA prevalence in recent years (p value ≤ 0.05). Based on the results of case reports (which were not included in the calculations mentioned above), the numbers of VRSA, VISA and hVISA isolates were 12, 24 and 14, respectively, among different continents. Since the prevalence of VRSA, VISA and hVISA has been increasing in recent years (especially in the Asian and American continents), rigorous monitoring of vancomycin treatment, it's the therapeutic response and the definition of appropriate control guidelines depending on geographical regions is highly recommended and essential to prevent the further spread of vancomycin-resistant S. aureus.

Pacemaker-associated infection caused by ST81/SCCmec IV methicillin-resistant, vancomycin-intermediate Staphylococcus aureus in Japan

A 76-year-old Japanese man was admitted to hospital for treatment of fever and skin lesion at the implantation site of his pacemaker. During his hospitalization, vancomycin-intermediate Staphylococcus aureus (MIC 4 μg/mL) with reduced susceptibility to daptomycin was isolated from venous blood. This isolate was identified as methicillin-resistant S. aureus with SCCmec IV and was genotyped as sequence type 81, coa VIIa and spa type t7044, harbouring blaZ, aac(6′)-aph(2″) and enterotoxin(-like) genes sea, seb, sek, sel, selx and selw. The patient was successfully treated with daptomycin, minocycline and sulfamethoxazole/trimethoprim. We describe the identification of sequence type 81/SCCmec IV vancomycin-intermediate S. aureus from pacemaker-associated septicaemia.

Association between cell growth and vancomycin resistance in clinical community-associated methicillin-resistant Staphylococcus aureus

Objectives

We investigated the association between the rate of cell growth and vancomycin (VAN) resistance by comparing the genomic and phenotypic characteristics of different sized colonies isolated from a single origin.

Methods

Vancomycin-intermediate Staphylococcus aureus (VISA) strain TMUS2136 was isolated from the pus of a patient with a brain abscess and a chronic subdural abscess. This strain grew slowly and formed colonies poorly on agar plates within 24 h of incubation. However, variously sized colonies were observed after 48 h of incubation. We isolated five strains from different sized colonies and compared their VAN susceptibility and genomic sequences using next-generation sequencing.

Results

The five strains showed different rates of growth and susceptibilities to VAN (range of MIC after 48 h of incubation; 3–5 mg/L), and slower growing strains tended to be more VAN resistant. Deletion of the spdC gene and SNPs in the sarA gene was confirmed in all five strains and six SNPs in other genes (including mreC, hssS, prs, SA2339, sun, and SA1132) were confirmed when comparing the five strains.

Conclusions

Deletion of the spdC gene, a novel virulence factor of S. aureus, and SNPs in the sarA gene may be associated with VAN resistance. It was hypothesized that any of the six genes in which SNPs were detected could affect cell growth rate and VAN resistance in slow-VISA strains.