Kanokporn Mongkolrattanothai

A Novel Methicillin-Resistance Cassette in Community-Acquired Methicillin-Resistant Staphylococcus aureus Isolates of Diverse Genetic Backgrounds

Until recently, it has been unclear whether community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA) isolates represent the spread of hospital MRSA isolates into the community. In 2 CA-MRSA isolates, a novel genetic element, designated staphylococcal cassette chromosome mec (SCCmec) type IV, was found; it differs from SCCmec types I-III in its small size and absence of non-beta-lactam genetic-resistance determinants. To study the prevalence of type IV SCCmec, polymerase chain reaction characterization of SCCmec was performed on DNA from 12 CA-MRSA isolates. The 12 CA-MRSA isolates were from diverse genetic backgrounds, as evidenced by their stratification into 5 pulsed-field gel electrophoresis types, 4 coagulase types, and 2 ribotypes. Eleven of the 12 isolates contained the novel SCCmec type IV element. Ten were resistant only to beta-lactam antibiotics. SCCmec type IV is present on the genome of CA-MRSA isolates. Its relatively small size and presence in isolates of diverse genetic backgrounds suggest that it may spread among S. aureus isolates.

Community-Onset Methicillin-Resistant Staphylococcus aureus Associated with Antibiotic Use and the Cytotoxin Panton-Valentine Leukocidin during a Furunculosis Outbreak in Rural Alaska

BACKGROUND Community-onset methicillin-resistant Staphylococcus aureus (CO-MRSA) reports are increasing, and infections often involve soft tissue. During a CO-MRSA skin infection outbreak in Alaska, we assessed risk factors for disease and whether a virulence factor, Panton-Valentine leukocidin (PVL), could account for the high rates of MRSA skin infection in this region. METHODS We conducted S. aureus surveillance in the outbreak region and a case-control study in 1 community, comparing 34 case patients with MRSA skin infection with 94 control subjects. An assessment of traditional saunas was performed. S. aureus isolates from regional surveillance were screened for PVL genes by use of polymerase chain reaction, and isolate relatedness was determined by use of pulsed-field gel electrophoresis (PFGE). RESULTS Case patients received more antibiotic courses during the 12 months before the outbreak than did control subjects (median, 4 vs. 2 courses; P=.01) and were more likely to use MRSA-colonized saunas than were control subjects (44% vs. 13%; age-adjusted odds ratio, 4.6; 95% confidence interval, 1.7-12). The PVL genes were present in 110 (97%) of 113 MRSA isolates, compared with 0 of 81 methicillin-susceptible S. aureus isolates (P<.001). The majority of MRSA isolates were closely related by PFGE. CONCLUSION Selective antibiotic pressure for drug-resistant strains carrying PVL may have led to the emergence and spread of CO-MRSA in rural Alaska.

Novel Non-mecA-Containing Staphylococcal Chromosomal Cassette Composite Island Containing pbp4 and tagF Genes in a Commensal Staphylococcal Species: a Possible Reservoir for Antibiotic Resistance Islands in Staphylococcus aureus

ABSTRACT Among methicillin-resistant Staphylococcus aureus isolates, a staphylococcal chromosomal cassette containing the mecA gene (SCCmec) is integrated into the chromosome at a unique site. SCCmec also contains unique ccrAB recombinase genes mediating its integration and excision from the genome and is flanked by characteristic left and right direct- and inverted-repeat sequences. A few non-mecA-containing SCC elements that have the other molecular features described above have recently been described. The origin of these cassettes is not clear. We have identified two new members of the SCC family integrated within orfX in Staphylococcus epidermidis strain ATCC 12228, neither of which carries mecA. One is a 57-kb element flanked by a unique 28-bp SCC direct repeat. It was called the SCC composite island (SCC-CI) because it carries a 19-kb SCC element (SCCpbp4) nested within it. SCCpbp4 contains pbp4 and tagF genes, as well as one pair of ccrAB genes (allotype 2) flanked by classical SCC-specific terminal repeats. External to SCCpbp4, SCC-CI contains a second pair of ccrAB genes (allotype 4), three IS431 elements, and genes mediating resistance to heavy metals. Genes mediating restriction-modification that may facilitate horizontal transfer are also present within SCC-CI, both within and outside SCCpbp4. Several novel arrangements of the SCC direct and inverted repeats were identified. Several long stretches of homology with other SCCs were found within and outside SCCpbp4. In view of the fact that SCC-CI was found in a commensal species, it may represent a reservoir for sequences involved in genetic shuffling between staphylococci and may contribute to the diversity found in SCC elements.

Epidemiology of community-onset staphylococcus aureus infections in pediatric patients: An experience at a children's hospital in central Illinois

BackgroundThe nation-wide concern over methicillin-resistant Staphylococcus aureus (MRSA) has prompted many clinicians to use vancomycin when approaching patients with suspected staphylococcal infections. We sought to characterize the epidemiology of community-onset S. aureus infections in hospitalized children to assist local clinicians in providing appropriate empiric antimicrobial therapy.MethodsFrom January 2005–June 2008, children (0–18 years old) admitted to the Childrens Hospital of Illinois with community-onset S. aureus infections were identified by a computer-assisted laboratory-based surveillance and medical record review.ResultsOf 199 patients, 67 (34%) had invasive infections, and 132 (66%) had skin and soft tissue infections (SSTIs). Among patients with invasive infections, S. aureus isolates were more likely to be susceptible to methicillin (MSSA 63% vs. MRSA 37%), whereas patients with SSTIs, S. aureus isolates were more likely to be resistant to methicillin (MRSA 64% vs. MSSA 36%). Bacteremia and musculoskeletal infections were the most common invasive infections in both groups of S. aureus. Pneumonia with empyema was more likely to be caused by MRSA (P = 0.02). The majority (~90%) of MRSA isolates were non-multidrug resistant, even in the presence of healthcare-associated risk factors.ConclusionEpidemiological data at the local level is important for antimicrobial decision-making. MSSA remains an important pathogen causing invasive community-onset S. aureus infections among hospitalized children. In our hospital, nafcillin in combination with vancomycin is recommended empiric therapy in critically ill patients with suspected invasive staphylococcal infections. Because up to 25% of MSSA circulating in our area are clindamycin-resistant, clindamycin should be used cautiously as empiric monotherapy in patients with suspected invasive staphylococcal infections.

Simultaneous carriage of multiple genotypes of Staphylococcus aureus in children

The co-existence of multiple genotypes in colonization by Staphylococcus aureus has not been fully investigated. The aim of this study was to evaluate the heterogeneity of S. aureus carriage in children. We evaluated 125 nasal and perianal swab samples that were positive for S. aureus from 76 children scheduled for elective surgery. For each sample, at least four colonies with the same or different morphotypes were selected for analysis. Multiple-locus variable-number tandem-repeat fingerprinting was used to determine the genetic relatedness and to characterize the clonality of the S. aureus strains. Of the 125 swabs, 91 (73 %) contained meticillin-sensitive S. aureus (MSSA), 8 (6 %) contained meticillin-resistant S. aureus (MRSA), and 26 (21 %) contained MSSA and MRSA simultaneously. A total of 738 S. aureus strains were evaluated with a mean of 6 colonies (range 4-15) picked from each culture. Of the 125 swabs, 32 (26 %) samples contained two genetically distinct S. aureus strains and 6 (5 %) contained three different genotypes. Multiple S. aureus strains simultaneously carried by individual children were genetically unrelated to each other. We concluded that the co-existence of multiple genotypes of S. aureus was common. The significance of multiple carriage is yet to be determined, but this intraspecies interplay could be important to pathogenicity and virulence in S. aureus.

Neurobrucellosis: Unexpected Answer From Metagenomic Next-Generation Sequencing

A diagnosis of brucellosis can be difficult because routine culture and serological methods exhibit variable sensitivity and specificity. We present the use of a metagenomic next- generation sequencing assay to diagnose a case of neurobrucellosis from cerebrospinal fluid, resulting in the institution of appropriate antibiotic treatment and a favorable clinical outcome.

Blastomyces antigen detection for monitoring progression of blastomycosis in a pregnant adolescent.

Although disseminated blastomycosis is a rare complication in pregnancy, delay in diagnosis and treatment can be fatal. We investigate the use of the Blastomyces urine antigen in diagnosis following disease progression in the intrapartum, postpartum, and neonatal periods. We describe a case of disseminated blastomycosis in a pregnant adolescent and review the pertinent literature regarding treatment and monitoring blastomycosis in pregnancy and the neonatal periods. This is the first reported case in which the Blastomyces urine antigen is utilized as a method of following disease activity during pregnancy confirming absence of clinically evident disease in a neonate. Urine antigen detection for blastomycosis can be useful for following progression of disease in patients with disseminated blastomycosis in both the intrapartum and postpartum periods.

Ventriculitis and choroid plexitis caused by multidrug-resistant Nocardia pseudobrasiliensis.

We describe a case of ventriculitis and choroid plexitis caused by a multidrug-resistant Nocardia pseudobrasiliensis in an immunocompetent child. Difficulties establishing an etiologic diagnosis, inconsistencies of antibiotic susceptibility testing, and the side effects of various antimicrobials presented challenges to her treatment and eventual favorable outcome.

Acquisition of High-Level Mupirocin Resistance and Its Fitness Cost among Methicillin-Resistant Staphylococcus aureus Strains with Low-Level Mupirocin Resistance

ABSTRACT We investigated whether methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) isolates with low-level mupirocin resistance can serve as recipients of a pSK41-like plasmid conferring high-level mupirocin resistance without substantial fitness cost. Our results suggest that acquisition of the plasmid conferring high-level mupirocin resistance was not necessarily associated with fitness cost in some MRSA recipients with low-level mupirocin resistance.

Molecular surveillance of Staphylococcus aureus colonization in a neonatal intensive care unit

In a survey of staphylococcal colonization, Staphylococcus aureus was detected in 7 of 67 infants (10%). Two of the infants (3%) carried methicillin-resistant S aureus (MRSA), revealing an unsuspected transmission of MRSA within the neonatal intensive care unit. Molecular surveillance of S aureus provided useful information to improve infection control practices.