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Multidrug-Resistant Staphylococci Profiled at Public Hospital, Community Sites in London

NEW YORK – A team from the UK and China has used whole-genome sequencing to characterize multidrug-resistant staphylococci isolated from commonly touched surfaces at hospitals and community sites in East and West London, uncovering new genetic features that help the microbes dodge antibiotics.

"[W]e found that there was a large diversity of antibiotic-resistant genes encoding resistance to different antibiotics," senior and corresponding author Hermine Mkrtchyan, a microbiology researcher at the University of East London, and her colleagues wrote.

In particular, the findings offered a closer look at the diverse forms of a mobile genetic element — the methicillin drug resistance gene mecA-containing "staphylococcal cassette chromosome" (SCCmec) — that are swapped by drug-resistant staphylococci.

Different SCCmec types have evolved from two different genetic lineages, including hospital-associated and community-associated clones," the authors explained "[C]urrently, these different lineages can be found both in hospital and community environments."

The researchers isolated some 600 Staphylococcus isolates from high-touch surfaces in London, including 224 isolates from East London and 376 West London isolates. After looking for known resistance markers with PCR, they used whole-genome sequencing to tease out antibiotic resistance features in 49 of the 281 multidrug-resistant bugs, focusing largely on representatives that contained mecA.

In addition to comparing multidrug-resistance representatives in different parts of the city, they delved into potential differences in staphylococci found on surfaces in hospitals with those sampled at surfaces in other public sites in two parts of the city.

"It has been documented that surfaces in hospitals and non-hospital areas can be potential reservoirs for antibiotic-resistant staphylococci, however, studies comparing general public areas and that of public areas in hospitals are fragmentary," the authors noted.

Their findings, appearing online today in Scientific Reports, revealed enhanced rates of multidrug-resistant Staphylococcus species at sampled surfaces in East London, for example.

The team reported that bugs from the S. epidermidis, S. haemolyticus, and S. hominis species were over-represented among the multidrug-resistant isolates identified on sampled surfaces in general, though 11 species with multidrug-resistant isolates were identified. Staphylococci at the London sites samples were most often able to resist antibiotics such as penicillin, fusidic acid, and erythromycin.

Given prescription rates reported for penicillin and other antibiotics at primary care sites in the past, the authors speculated that "high usage of these antibiotics might relate to why it is common to see penicillin and erythromycin resistance from staphylococci isolates from general public settings."

When it came to the kinds of antibiotic resistance genes found in the multidrug-resistant staphylococci, meanwhile, the team found that the blaZ and qacA/B resistance genes were widespread, as were known and previously unreported versions of the SCCmec mobile element types.

"A diverse range of SCCmec types were determined from general public settings and public areas of hospitals, of which many were untypeable," the authors explained, noting that such SCCmec representatives "have not been previously reported in isolates recovered from environmental surfaces in general public settings."