The need for rapid methods to accurately detect methicillin-resistant Staphylococcus aureus (MRSA) is widely acknowledged, and a number of molecular assays are commercially available. This study evaluated the Xpert MRSA assay, which is run on the GeneXpert real-time PCR platform (Cepheid) for use in a clinical laboratory. The following parameters were investigated: (i) the limits of detection (LoDs) for four MRSA strains; (ii) the ability to detect isolates of MRSA from a collection representative of MRSA in Ireland since 1974 (n ‫؍‬ 114) and the ability to detect control strains with staphylococcal cassette chromosome mec types IVa (IV.1.1.1), IVb (IV.2.1.1), IVc (IV.3.1.1), IVd (IV.4.1.1), V (V.1.1.1), V T , and VI; and (iii) performance in a clinical trial with swabs from nose, throat, and groin/perineum sites from 204 patients, where results were compared with those obtained by direct and enrichment cultures. The average LoD of the four test strains was 610 CFU/ml (equivalent to 58 CFU/swab). All 114 MRSA isolates and 7 control strains tested were detected. Sensitivity, specificity, and positive and negative predictive values for clinical specimens from all sites investigated were 90%, 97%, 86%, and 98%, respectively, but throat specimens yielded poor sensitivity (75%). Sensitivity, specificity, and positive and negative predictive values for nasal specimens were 95%, 98%, 90%, and 99%, respectively. Overall, the assay was rapid and easy to perform, but performance might be enhanced by the inclusion of an equivocal interpretive category based on analysis of all available amplification data.

Methicillin-susceptible Staphylococcus aureus (MSSA) can arise from methicillin-resistant S. aureus (MRSA) following partial or complete excision of staphylococcal cassette chromosome mec (SCCmec). This study investigated whether multiresistant MSSA isolates from Irish hospitals, where MRSA has been endemic for decades, harbor SCCmec DNA. Twenty-five multiresistant MSSA isolates recovered between 2002 and 2006 were tested for SCCmec DNA by PCR and were genotyped by multilocus sequence typing and spa typing. All isolates lacked mecA. Three isolates (12%) harbored SCCmec DNA; two of these (genotype ST8/t190) harbored a 26-kb SCCmec IID (II.3.1.2) remnant that lacked part of mecI and all of mecR1, mecA, and IS431; the third isolate (ST8/t3209) harbored the SCCmec region from dcs to orfX. All three isolates were detected as MRSA using the BD GeneOhm and Cepheid's Xpert MRSA real-time PCR assays. Six isolates (ST8/t190, n ‫؍‬ 4; ST5/t088, n ‫؍‬ 2), including both isolates with the SCCmec IID remnant, harbored ccrAB4 with 100% identity to ccrAB4 from the Staphylococcus epidermidis composite island SCC-CI. This ccrAB4 gene was also identified in 23 MRSA isolates representative of ST8/t190-MRSA with variant SCCmec II subtypes IIA to IIE, which predominated previously in Irish hospitals. ccrAB4 was located 5,549 bp upstream of the left SCCmec junction in both the MRSA and MSSA isolates with SCCmec elements and remnants and 5,549 bp upstream of orfX in the four MSSA isolates with ccrAB4 only on an SCC-CI homologous region. This is the first description of a large SCCmec remnant with ccr and partial mec genes in MSSA and of the S. epidermidis SCC-CI and ccrAB4 genes in S. aureus.

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The FcyR receptors for IgG, FcyRI, FcyRII and FcyRIII were measured on neutrophils and monocytes from 36 patients suspected of systemic infection. These results were compared with 30 blood donor controls to assess the level of expression as an early indicator of bacterial infection. FcyRI expression on neutrophils was found to be significantly increased from patients with systemic or localised infections, when compared to the non-infected patient group, i.e., patients with no cultural evidence of bacterial infections, (p = 0.02, p = 0.04) or normal controls (p C 0.0001, p = 0.0005). FcyRI expression on monocytes was also significantly increased in both of the infected groups compared to normal controls (p < 0.0001, p = 0.001); however, no significant difference could be seen when compared with the non-infected patients. Fc yRIII was found to be significantly increased on a subset of monocytes in patients with systemic or localised infections compared to the non-infected group (p = 0.009, p = 0.006) and compared to the normal controls (p = 0.009, p = 0.003). Infections caused by gramnegative bacilli induced a higher FcyR response than infection with either streptococci or staphylococci. These data suggest that the measurement of FcyRI on neutrophils and FcyRIII on monocytes may be a useful rapid indicator of bacterial infection.

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Summary:An outbreak of multi-resistant Serratia marcescens involving 24 patients occurred in a bone marrow transplant and oncology unit, from September 1998 to June 1999, of whom 14 developed serious infection. This is the first such outbreak described in a BMT unit. All isolates demonstrated the same antimicrobial susceptibility pattern and were the same unusual serotype O21:K14. The antimicrobial susceptibility profile showed reduced susceptibility to ciprofloxacin, gentamicin and piperacillin-tazobactam. As the latter two antimicrobials are part of our empiric therapy for febrile neutropenia, they were substituted with meropenem and amikacin during the outbreak. Investigation revealed breaches in infection control practices. Subsequently, the outbreak was contained following implementation of strict infection control measures. A prominent feature of the outbreak was prolonged carriage in some patients. These patients may have acted as reservoirs for cross-infection. This report also indicates that patients who become colonised with Serratia marcescens may subsequently develop invasive infection during neutropenic periods. Bone Marrow Transplantation (2000) sistence of Serratia marcescens in the environment and prolonged patient carriage, factors which undoubtedly contributed to the length of the outbreak. Furthermore, patients who were carriers frequently developed invasive infection during periods of neutropenia. Materials and methods Patient dataFrom September 1998 to June 1999, we observed an outbreak of Serratia marcescens involving 24 patients, in a 31-bed haematology-oncology unit, which incorporates the National Bone Marrow Transplant unit. The unit has four six-bedded wards, three single rooms and four HEPAfiltered BMT rooms. Fifteen patients were haematology patients, six of whom were receiving cytotoxic chemotherapy, eight were post BMT and one patient, the index case, was on cytotoxic chemotherapy during his first two episodes of sepsis and in the early post-BMT phase for his third. Nine patients were oncology patients, all of whom were receiving cytotoxic chemotherapy for their underlying disease. An infected case was defined as a patient with symptoms and/or signs of infection and Serratia marcescens was cultured from an infected site. A colonised case was defined as a patient in whom Serratia marcescens was cultured in the absence of symptoms and/or signs of infection. The number of new cases per month is shown in Figure

The minimum inhibitory concentrations (MICs) of cefaclor, co-amoxiclav, clarithromycin and ciprofloxacin for 59 strains of vaginal lactobacilli were determined by both the reference agar dilution and E test methods. With the exception of clarithromycin, there was poor correlation between the results obtained by the two techniques. This was most apparent for the beta-lactams studied, the MICs of cefaclor as determined by the E test being particularly difficult to define. The stability of antimicrobial gradients in the E test may cause problems when testing slow-growing bacteria and/or organisms which grow only under anaerobic conditions. Accordingly, only those MICs determined by the agar dilution method are reported. The percentages of susceptible isolates were as follows: clarithromycin, 100; co-amoxiclav, 100; cefaclor, 20; and ciprofloxacin, 4. The administration of antimicrobials, such as ciprofloxacin and cefaclor, which have poor activities in vitro against lactobacilli, may therefore be advantageous to the host because it allows the protective effects of the normal vaginal flora to be preserved.

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