Adult methicillin-resistant Staphylococcus aureus bacteremia in Taiwan: clinical significance of non–multi-resistant antibiogram and Panton–Valentine leukocidin gene

Staphylococcus aureus Genomic Analysis and Outcomes in Patients with Bone and Joint Infections: A Systematic Review

Many studies have been published assessing the association between the presence of S. aureus genes and outcomes in patients with bone and joint infections (BJI), but it is not known if they have had similar findings. A systematic literature review was performed. All available data on studies in Pubmed between January 2000 to October 2022 reporting the genetic characteristics of S. aureus and the outcomes of BJIs were analyzed. BJI included prosthetic joint infection (PJI), osteomyelitis (OM), diabetic foot infection (DFI), and septic arthritis. Because of the heterogeneity of studies and outcomes, no meta-analysis was performed. With the search strategy, 34 articles were included: 15 articles on children and 19 articles on adults. In children, most BJI studied were OM (n = 13) and septic arthritis (n = 9). Panton Valentine leucocidin (PVL) genes were associated with higher biological inflammatory markers at presentation (n = 4 studies), more febrile days (n = 3), and more complicated/severe infection (n = 4). Other genes were reported anecdotally associated with poor outcomes. In adults, six studies reported outcomes in patients with PJI, 2 with DFI, 3 with OM, and 3 with various BJI. Several genes were associated with a variety of poor outcomes in adults, but studies found contradictory results. Whereas PVL genes were associated with poor outcomes in children, no specific genes were reported similarly in adults. Additional studies with homogenous BJI and larger sample sizes are needed.

Epidemiological and clinical features of Panton-Valentine Leukocidin positive Staphylococcus aureus bacteremia: A case-control study

BACKGROUND

Panton-Valentine Leukocidin (PVL) toxin in Staphylococcus aureus has been associated with both severe pneumonia and skin and soft tissue infections. However, there are only limited data on how this virulence factor may influence the clinical course or complications of bacteremic S. aureus infections.

METHODS

Between September 2016 and March 2018, S. aureus isolates from clinical cultures from hospitals in an academic medical center underwent comprehensive genomic sequencing. Four hundred sixty-nine (29%) of 1681 S. aureus sequenced isolates were identified as containing the genes that encode for PVL. Case patients with one or more positive blood cultures for PVL were randomly matched with control patients having positive blood cultures with lukF/lukS-PV negative (PVL strains from a retrospective chart review).

RESULTS

51 case and 56 control patients were analyzed. Case patients were more likely to have a history of injection drug use, while controls more likely to undergo hemodialysis. Isolates from 78.4% of case patients were methicillin resistant as compared to 28.6% from control patients. Case patients had a higher incidence of pneumonia and skin and soft tissue infection and longer duration of fever without differences in length of bacteremia. Clinical cure or expiration was comparable.

CONCLUSIONS

These results are consistent with prior observations associating the PVL toxin with both community-acquired MRSA strains as well as severe staphylococcal pneumonia. The presence of the PVL toxin does not appear to otherwise influence the natural history of bacteremic S. aureus disease other than in prolonging the duration of fever.

Increased Age-Dependent Risk of Death Associated With lukF-PV-Positive Staphylococcus aureus Bacteremia

Background.

Panton-Valentine leucocidin is a Staphylococcus aureus virulence factor encoded by lukF-PV and lukS-PV that is infrequent in S aureus bacteremia (SAB), and, therefore, little is known about risk factors and outcome of lukF-PV/lukS-PV-positive SAB.

Methods.

This report is a register-based nationwide observational cohort study. lukF-PV was detected by polymerase chain reaction. Factors associated with the presence of lukF-PV were assessed by logistic regression analysis. Adjusted 30-day hazard ratios of mortality associated with lukF-PV status were computed by Cox proportional hazards regression analysis.

Results.

Of 9490 SAB cases, 129 were lukF-PV-positive (1.4%), representing 14 different clonal complexes. lukF-PV was associated with younger age, absence of comorbidity, and methicillin-resistant S aureus. In unadjusted analysis, mortality associated with lukF-PV-positive SAB was comparable to SAB. However, lukF-PV-positive SAB nonsurvivors were significantly older and had more comorbidity. Consequently, by adjusted analysis, the risk of 30-day mortality was increased by 70% for lukF-PV-positive SAB compared with SAB (hazard ratio, 1.70; 95% confidence interval, 1.20–2.42; P = .003).

Conclusions.

lukF-PV-positive SAB is rare in Denmark but associated with a significantly increased risk of mortality. Although the risk of lukF-PV-positive SAB was highest in the younger age groups, >80% of deaths associated with lukF-PV-positive SAB occurred in individuals older than 55 years.

Predicting methicillin resistance among community-onset Staphylococcus aureus bacteremia patients with prior healthcare-associated exposure

To develop and validate prediction rules to identify the risk of methicillin-resistant Staphylococcus aureus (MRSA) infection among community patients who have healthcare-associated (HA) exposure and S. aureus bacteremia. A total of 1,166 adults with community-onset S. aureus bacteremia were retrospectively enrolled. The background prevalence of community MRSA infection was extrapolated from 392 community-associated S. aureus bacteremia (CA-SAB) patients without HA exposure. Complete and clinical risk scores were derived and tested using data from 774 healthcare-associated S. aureus bacteremia (HA-SAB) patients. The risk scores were modeled with and without incorporating previous microbiological data as a model predictor and stratified patients to low-, intermediate-, and high-risk groups for MRSA infection. The clinical risk score included five independent predictors and the complete risk score included six independent predictors. The clinical and complete risk scores stratified 32.7 % and 42.0 % of HA-SAB patients to the low-risk group for MRSA infection respectively. The prevalence of MRSA infection in score-stratified low-risk groups ranged from 16.3 % to 23.3 %, comparable to that of CA-SAB patients (13.8 %). Simple decision rules allow physicians to stratify the risk of MRSA infection when treating community patients with prior HA exposure and possible S. aureus infection.

Predictors of mortality in Staphylococcus aureus Bacteremia

Staphylococcus aureus bacteremia (SAB) is an important infection with an incidence rate ranging from 20 to 50 cases/100,000 population per year. Between 10% and 30% of these patients will die from SAB. Comparatively, this accounts for a greater number of deaths than for AIDS, tuberculosis, and viral hepatitis combined. Multiple factors influence outcomes for SAB patients. The most consistent predictor of mortality is age, with older patients being twice as likely to die. Except for the presence of comorbidities, the impacts of other host factors, including gender, ethnicity, socioeconomic status, and immune status, are unclear. Pathogen-host interactions, especially the presence of shock and the source of SAB, are strong predictors of outcomes. Although antibiotic resistance may be associated with increased mortality, questions remain as to whether this reflects pathogen-specific factors or poorer responses to antibiotic therapy, namely, vancomycin. Optimal management relies on starting appropriate antibiotics in a timely fashion, resulting in improved outcomes for certain patient subgroups. The roles of surgery and infectious disease consultations require further study. Although the rate of mortality from SAB is declining, it remains high. Future international collaborative studies are required to tease out the relative contributions of various factors to mortality, which would enable the optimization of SAB management and patient outcomes.

Spinal epidural abscess in adults caused by Staphylococcus aureus: clinical characteristics and prognostic factors

OBJECTIVE

Spinal epidural abscess (SEA) is a devastating infectious disease, which may result in neurologic sequelae. Staphylococcus (S.) aureus is a common pathogen of SEA. Here, we analyzed the clinical characteristics and laboratory data of adult patients with S. aureus SEA and compared the clinical characteristics of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) infections.

METHODS

Between 2003 and 2008, we collected data regarding 29 adult cases of S. aureus SEA and analyzed the clinical presentations, magnetic resonance (MR) imaging features, therapeutic outcome, and prognostic factors. Antibiotic susceptibility test results of 11 implicated MRSA strains were also further analyzed.

RESULTS

We identified 17 MSSA strains and 12 MRSA strains. Lumbar and lumbosacral spine segments were the most commonly involved segments. All 29 patients had back pain. Other findings included sensory abnormalities (25), motor weakness (21), fever (16), bladder dysfunction (16), and altered consciousness (3). Disease onset at admission was acute in 6 cases and chronic in 23. The stages of disease severity were early stage in 9 and late stage in 20. After therapy, 21 patients had a good prognosis and 8 had a poor prognosis. Significant prognostic factors included older age (>70years), presence of diabetes mellitus, adrenal insufficiency, and MRSA infection. The prognosis alone was clinically different between patients with MSSA and MRSA infections.

CONCLUSIONS

Patients with localized back pain, particularly those with a fever and compromised immune system, should undergo MR imaging to ensure an early diagnosis and management.

Clonal spreading of methicillin-resistant SCCmec Staphylococcus aureus with specific spa and dru types in central Taiwan

The goal of this study was to delineate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Ninety-six MRSA isolates were collected from the blood cultures of different patients during the period July to December of 2008. The spa typing, staphylococcal chromosomal cassette (SCCmec) typing, mec-associated direct repeat unit (dru) copy numbers, and toxin genes (sea, seb, sec, tst, lukS/F) of each isolate were determined. Thirty-eight, 28, 18, and 12 MRSA isolates were SCCmec type II, SCCmec type III, SCCmec type IV, and SCCmec type V, respectively. Most (31/38, 81.6%) of the SCCmec type II isolates were of spa t002 with four dru repeats. Some of them also carried the sec or tst toxin gene (67.7 and 80.6%, respectively). Of the 28 SCCmec type III MRSA isolates, 15 (53.6%) were of t037 with 14 dru repeats, and all also carried the sea gene. Of the 18 SCCmec type IV MRSA isolates, 13 (72.2%) were of t437 with nine dru repeats, and ten of them also had the seb gene. Among the SCCmec type V MRSA isolates, nine were type V(T). Five (55.6%) of them were of t437 with 11 dru repeats, and all contained the lukS/F gene. The clonal spreading of SCCmec MRSA strains with specific spa and dru types was found. Further longitudinal, multiple-site surveillance is required in order to define the MRSA evolution in Taiwan.

Progression to bacteremia in critical care patients colonized with methicillin-resistant Staphylococcus aureus expressing Panton-Valentine leukocidin

The role of Panton-Valentine leukocidin (PVL) in methicillin-resistant Staphylococcus aureus (MRSA) infections is unclear. PVL has been long associated with soft tissue infections and necrotizing pneumonia, but inconsistently with other site infections or mortality. The retrospective cohort study explores the association between PVL and bacteremia in colonized medical intensive care unit (ICU) patients with surveillance isolates and blood cultures. A total of 840 patients were screened by nasal swab, with 266 patients found to be colonized and 46 with bacteremia. Colonization by PVL(+) MRSA increased the odds of bacteremia (odds ratio, 2.40; confidence interval, 1.23-4.57), and invasive infection developed earlier in these patients (relative risk, 0.44; confidence interval 0.25-0.85) compared to those colonized with PVL(0) MRSA. PVL was not associated with infections at other sites, length of ICU stay, or mortality. PVL decreases the time to bacteremia in colonized patients but does not otherwise contribute to disease course or clinical outcome.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Nosocomial methicillin-resistant Staphylococcus aureus (MRSA) bacteremia in Taiwan: mortality analyses and the impact of vancomycin, MIC = 2 mg/L, by the broth microdilution method

Background

Previous studies regarding the prognosis of patients infected with MRSA isolates characterized by a high minimum inhibitory concentration (MIC) for vancomycin have generally used a commercial Etest. Little research has been conducted on determining the vancomycin susceptibility of MRSA using a reference microdilution. Additionally, there is discordance between the MIC result from an Etest and the value determined using the reference microdilution method.

Methods

Using a reference microdilution method, we determined the MIC of vancomycin for isolates from 123 consecutive patients with nosocomial MRSA bacteremia. The clinical features and outcome for these patients were recorded and the MRSA isolates were genotyped.

Results

Among the 123 non-duplicated isolates, 21.1% had a MIC = 2 mg/L, 76.4% had a MIC = 1 mg/L and 2.4% had MIC = 0.5 mg/L. Patients with MRSA bacteremia in the ICU or those who had been hospitalized for a long time were more likely to be infected with strains of high vancomycin MIC MRSA (MIC = 2 mg/L; p < 0.05). Cox regression analysis demonstrated that the high MIC group had a significantly higher 30-day mortality than the low MIC group (HR: 2.39; 95% CI: 1.20-4.79; p = 0.014). Multivariate analyses indicated that the presence of high MIC isolates, pneumonia, post-cardiothoracic surgery and a high Charlson comorbidity index were all independent predictors of a 30-day mortality. Genotyping of these high vancomycin MIC isolates demonstrated that SCCmec III, spa type037, was the predominant strain (> 80%). The rates of resistance to trimethoprim/sulfamethoxazole, gentamicin, levofloxacin, rifampin and tetracycline were also higher in the high MIC group than in the isolates belonging to low MIC group (p < 0.05).

Conclusions

In a high vancomycin MIC group in Taiwan, SCCmec III, spa type t037, was the predominant strain of MRSA identified. Patients with MRSA bacteremia in the ICU or who had prolonged hospitalization were more likely to be infected with S. aureus strains with high vancomycin MICs. The mortality rate was higher among patients infected with these strains compared to patients infected with low MIC strains.

Epidemiology and susceptibilities of methicillin-resistant Staphylococcus aureus in Taiwan: emphasis on chlorhexidine susceptibility

Chlorhexidine is an antiseptic agent used for hand hygiene worldwide. To evaluate the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to chlorhexidine, this study determined MICs of chlorhexidine and another 12 antimicrobial agents, carriage of the Panton-Valentine leukocidin, qacA/B, and smr genes, genetic relatedness by multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec element type for 206 MRSA clinical isolates from the Taiwan Surveillance of Antimicrobial Resistance program III and IV (years 2002 and 2004) from 26 hospitals. Using MLST, we respectively identified 102 (49.5%), 68 (33.0%), 13 (6.3%), 5 (2.4%), 5 (2.4%), and 13 (6.3%) isolates as ST239, ST59, ST5, ST241, ST573, and other types. The MIC(50) and MIC(90) of chlorhexidine for all 206 isolates were 2 and 8 microg/mL, respectively. Seventy-three (35.4%) isolates carried qacA/B gene, but none carried smr. For the 72 (35.0%) MRSA isolates with chlorhexidine MIC > or =4 microg/mL, 53 were ST239 (49 of them carried qacA gene), 12 were ST5 (all carried qacB gene), 5 were ST241 (4 carried qacA gene), 1 was ST338 (and carried qacA gene), and 1 was ST573 (and carried qacA gene). Compared with other sequence-type MRSA isolates, ST239 MRSA isolates were the most resistant to both chlorhexidine and other antimicrobial agents. Methicillin-resistant S. aureus strains with disinfectant resistance qacA/B genes are common in Taiwan. High frequency of qacA/B genes among specific sequence types (ST239, ST5, and ST241) resulted in low susceptibility to chlorhexidine. Periodic surveillance of antiseptic susceptibility among MRSA isolates is important for the control of nosocomial hospital-acquired infections.