A screening strategy for phenotypic detection of carbapenemase in the clinical laboratory.

Nosocomial infections caused by carbapenemase-producing Enterobacteriaceae have emerged as an important challenge worldwide and represent a great limitation for antimicrobial therapy. Detection of carbapenemase in Enterobacteriaceae species also remains challenging. Although the modified Hodge test is recommended, it lacks specificity and is unable to distinguish between carbapenemase types. Here, we demonstrated a screening strategy for the phenotypic detection of carbapenemases among Enterobacteriaceae isolates in the clinical laboratory by using ethylenediaminetetraacetic acid and phenylboronic acid. This strategy displayed an overall 100% sensitivity and 98.6% specificity for carbapenemase detection in Enterobacteriaceae, which was superior to that of the modified Hodge test (98.0% sensitivity and 84.3% specificity), and it also discriminated the carbapenemase phenotypes of KPC-2, VIM-1, and OXA-48.

Improving the efficiency of the modified Hodge test in KPC-producing Klebsiella pneumoniae isolates by incorporating an EDTA disk.

Carbapenemase-producing Klebsiella pneumoniae have emerged as an important pathogens in nosocomial infections with high mortality rate. Although the modified Hodge test (MHT) is recommended for phenotypic detection of carbapenemase-producing Enterobacteriaceae, high false-positive rates were reported for MHT results. The MHT has acceptable sensitivity (98.0 %), but it lacks specificity (73.6 %). In this study, we incorporated an EDTA disk test into the MHT (MHT-EDTA) to improve the efficiency in phenotypic detection of K. pneumoniae carbapenemase (KPC) of K. pneumoniae isolates. EDTA was used to lyse the cells of 123 carbapenem non-susceptible K. pneumoniae isolates to release the ß-lactamases. The MHT-EDTA achieved 100 % sensitivity and specificity for KPC detection among K. pneumoniae isolates as compared to growth patterns of the indicator organism E. coli (ATCC 25922). This method could be carried out as part of routine work to provide useful information for the clinical management of K. pneumoniae infection.

Surgical site infection in elderly oral cancer patients: is the evaluation of comorbid conditions helpful in the identification of high-risk ones?

PURPOSE: This study was performed to gain some knowledge on the possible relation between surgical site infection (SSI) and geriatric patients who undergo surgical treatment of oral squamous cell carcinoma and to identify the risk factors in this specific population. PATIENTS AND METHODS: A retrospective study from 2004 through 2010 at the Department of Oral and Maxillofacial Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine was conducted. The primary outcome variable was the presence of SSIs. Twenty-seven variables of the patients concerning general characteristics, comorbidities, disease information, and treatment options were investigated. A multivariate analysis using logistic regression was implemented to find SSI risk factors. RESULTS: The data of 376 patients (183 men, 48.7%; 193 women, 51.3%) older than 65 years with the diagnosis of oral squamous cell carcinoma were included in the present analysis. In multivariate logistic regression analysis, 6 parameters were identified for a significant and independent association with the development of SSI: body mass index (P = .0086); diabetes (P < .0001); American Society of Anesthesiologists score (P = .0127); Adult Comorbidity Evaluation-27 score (P = .0392); operation time (P = .0003); and reconstruction with pectoralis major myocutaneous flaps or free flaps (P < .0001). CONCLUSIONS: Special attention to SSIs should be given to elderly patients with oral squamous cell carcinoma. The authors advocate a preoperative evaluation of comorbidities and the selection of high-risk elderly patients for a more effective prevention of SSIs.

Antimicrobial Resistance and Molecular Characteristics of Nasal Staphylococcus aureus Isolates From Newly Admitted Inpatients.

Staphylococcus aureus, or methicillin-resistant S. aureus (MRSA), is a significant pathogen in both nosocomial and community infections. Community-associated MRSA (CA-MRSA) strains tend to be multi-drug resistant and to invade hospital settings. This study aimed to assess the antimicrobial resistance and molecular characteristicsof nasal S. aureus among newlyadmitted inpatients.In the present study, 66 S. aureus isolates, including 10 healthcare-associated MRSA (HA-MRSA), 8 CA-MRSA, and 48 methicillin-sensitive S. aureus (MSSA) strains, were found in the nasal cavities of 62 patients by screening 292 newlyadmitted patients. Antimicrobial resistance and molecular characteristics of these isolates, including spa-type, sequence type (ST) and SCCmec type, were investigated. All isolates were sensitive to linezolid, teicoplanin, and quinupristin/dalfopristin, but high levels of resistance to penicillin and erythromycin were detected. According to D-test and erm gene detection results, the cMLS(B) and iMLS(B) phenotypes were detected in 24 and 16 isolates, respectively. All 10 HA-MRSA strains displayed the cMLS(B) phenotypemediated by ermA or ermA/ermC, while the cMLS(B) CA-MRSA and MSSA strains carried the ermB gene. Molecular characterization revealedall 10 HA-MRSA strains were derived from the ST239-SCCmec III clone, and four out of eight CA-MRSA strains were t437-ST59-SCCmec V. The results suggest that patients play an indispensable role in transmitting epidemic CA-MRSA and HA-MRSA strains.

Clonal dissemination of multilocus sequence type 11 Klebsiella pneumoniae carbapenemase - producing K. pneumoniae in a Chinese teaching hospital.

Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae has disseminated rapidly in China. We aimed to analyze the molecular epidemiology of four KPC-producing K. pneumoniae strains isolated from a suspected clonal outbreak during a 3-month period and to track the dissemination of KPC-producing K. pneumonia retrospectively. We created antimicrobial susceptibility profiles using an automated broth microdilution system and broth microdilution methods. We screened carbapenemase and KPC phenotypes using the modified Hodge test and meropenem-boronic acid (BA) disk test, respectively. We identified ß-lactamase genes with PCR and sequencing. We investigated clonal relatedness for epidemiological comparison using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). All isolates expressed multidrug resistance and yielded positive results for the modified Hodge and meropenem-BA disk tests. The isolates all carried blaKPC -2 , and coproduced CTX-M-type extended-spectrum ß-lactamase. PFGE and MLST showed that the isolates were clonally related. The PFGE patterns of these isolates had ≥90% similarity. We found a single clone, sequence type (ST) 11, and its typical dissemination mode resembled clonal spread. The dissemination of KPC-producing K. pneumoniae is clonally related and there is probable local transmission of a successful ST11 clone.