Tracing the Spread of Methicillin-ResistantStaphylococcus aureusby Southern Blot Hybridization Using Gene-Specific Probes of mec and Tn554

Abstract

In a community hospital in Brooklyn, New York, over a 3-year period, 79 methicillin-resistant Staphylococcus aureus (MRSA) isolates from five different case clusters were subtyped by Southern blot hybridization with two previously characterized gene probes, mec and Tn554. Together, the genotyping enabled the hospital infection control team to differentiate simultaneous MRSA clusters in the surgical intensive care unit (type I:A) and the open heart unit (type II:J), document the spread of one strain (type I:A) between roommates, identify an endemic strain (type II:J) from cardiac monitors and medical personnel, and identify an unrelated outbreak strain (type II:NH) in the labor and delivery unit. On the basis of this investigation it is clear that the routine DNA fingerprinting of MRSA in health care facilities, to monitor their spread and identify cases of nosocomial infections, is an important infection control measure.

Comparison of DNA Sequencing of the Protein A Gene Polymorphic Region with Other Molecular Typing Techniques for Typing Two Epidemiologically Diverse Collections of Methicillin-Resistant Staphylococcus aureus

“…The implementation of the spaA typing method was straightforward, and the results obtained were reproducible, unambiguous, and easily interpreted. This method seems to be adequate for outbreak investigations but should be complemented with other techniques in long-term surveillance or in studies comparing distant clonal lineages.Three molecular typing techniques (5) have been largely used for the characterization of clones of methicillin-resistant Staphylococcus aureus (MRSA) and enabled the detection of widely spread MRSA lineages, such as the Iberian, Brazilian, New York/Tokyo, and pediatric MRSA clones (1,7,11,17,20,21,24). The combined methods consist of (5, 10) Southern blot analysis of chromosomal ClaI digests with a mecA DNA probe (ClaI-mecA polymorphisms) and with a Tn554 transposon probe (ClaI-Tn554 insertion patterns) and restriction fragment length polymorphism analysis of chromosomal DNA generated after cleavage with SmaI and pulsed-field gel electrophoresis (PFGE) (SmaI-PFGE).…”

Genetic Homogeneity Among Methicillin-ResistantStaphylococcus AureusStrains From Saudi Arabia

“…As a follow-up study, additional genetic typing of the strain with Mec-related or transposon-derived DNA probes should be initiated to firmly establish its novel character. 13 Screening of medical personnel for MRSA carriage should be performed to analyze the potential reservoir among hospital care workers in Saudi Arabia. Recently, a similar and valuable study into carriership of enteroroxin-producing S. aureus among restaurant personnel was performed in Kuwait, another country along the Arabian peninsula.2 This study could serve as an adequate example, both for methodology and, subsequently, risk analysis.…”

“…Molecular identification of MRSA has provided the basis for the current insights in MRSA epidemiology. [12][13][14][15] In several more local studies, nationwide spread of certain strains has been identified.19-21-28 A recent report from Jeddah, Saudi Arabia,29 documents a relatively high incidence (6.5%-8.9%) of MRSA among hospitalized patients. Although no apparent rise in infection frequency was observed during the years 1990-1992, these percentages urge additional studies to be initiated.…”

Use of a Multiplex Molecular Beacon Platform for Rapid Detection of Methicillin and Vancomycin Resistance in Staphylococcus aureus

“…For the reactions using BAC16S, SG16S, spa, and mecA as targets, each 50-l reaction contained 25 l iQ Supermix (Bio-Rad, Hercules, CA), 0.5 M of each primer (Table 1), BAC16S forward and BAC16S reverse (SG16S and BAC16S use the same primers), mecA forward and mecA reverse, spa forward and spa reverse, 0.025 M of BAC16S molecular beacon probe, 0.4 M of SG16S molecular beacon probe, 0.1 M of mecA molecular beacon probe, 0.05 M of spa molecular beacon probe, and 1 l of purified genomic DNA (used at approximately 15 to 100 ng/l); the remainder of the 50 l was nucleasefree water. Genomic DNA was purified as described previously (12). The thermocycling program used was 1 cycle of 95°C for 10 min followed by 45 cycles of 95°C for 30 s, 50°C for 30 s, and 72°C for 30 s. The entire RT-PCR takes approximately 3 h from setup to analysis.…”