Clinical Microbiology Articles

Preventing healthcare-associated infection through education: have surgeons been overlooked?

Seamus M. McHugh et al. — Thu, 10 Nov 2011 04:19:29 PST

BACKGROUND/AIMS: Some 20-30% of HCAI are considered to be preventable through an extensive infection prevention and control programme. Through an extensive literature review we aim to critically appraise studies which have utilised education initiatives to decrease HCAI.

METHODS: An extensive review of the literature was carried out in both online medical journals and through the Royal College of Surgeons in Ireland library.

FINDINGS: Many studies over the last 10 years have demonstrated success in educating nursing staff, critical care healthcare workers as well as medical students and junior doctors in the infection prevention and control of infection. Comparatively few have focussed on surgical trainees. A blended learning approach, with particular focus on the small group format is important. Interventions involving web-based learning in combination with established education formats are proving successful in changing behaviour.

CONCLUSIONS: The development of an educational strategy for surgical trainees focussing on infection prevention and control is overdue. Such a programme would have far reaching benefits for individual patients, contribute to significant economic savings within health services and enhance the quality and safety of patient care.

Impact of admission screening for methicillin-resistant Staphylococcus aureus on the length of stay in an emergency department.

P Gilligan et al. — Wed, 02 Nov 2011 09:36:02 PDT

Preventing and controlling methicillin-resistant Staphylococcus aureus (MRSA) includes early detection and isolation. In the emergency department (ED), such measures have to be balanced with the requirement to treat patients urgently and transfer quickly to an acute hospital bed. We assessed, in a busy and overcrowded ED, the contribution made to a patient's stay by previous MRSA risk group identification and by selective rescreening of those patients who were previously documented in the research hospital as being MRSA positive. Patients with a previous diagnosis of MRSA colonisation were flagged automatically as 'risk group' (RG) on their arrival in the ED and were compared with 'non-risk group' (NRG), i.e. not previously demonstrated in the research hospital to be infected or colonised with MRSA. Over an 18 month period, there were 16 456 admissions via the ED, of which 985 (6%) were RG patients. The expected median times to be admitted following a request for a ward bed for NRG and RG patients were 10.4 and 12.9h, respectively. Female sex, age >65 years, and RG status all independently predicted a statistically significantly longer stay in the ED following a request for a hospital bed. We consider that national and local policies for MRSA need to balance the welfare of patients in the ED with the need to comply with best practice, when there are inadequate ED and inpatient isolation facilities. Patients with MRSA requiring emergency admission must have a bed available for them.

DNA Microarray Genotyping and Virulence and Antimicrobial Resistance Gene Profiling of Methicillin-Resistant Staphylococcus aureus Bloodstream Isolates from Renal Patients.

Sinead McNicholas et al. — Fri, 14 Oct 2011 07:03:13 PDT

Thirty-six methicillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates from renal patients were genetically characterized by DNA microarray analysis and spa typing. The isolates were highly clonal, belonging mainly to ST22-MRSA-IV. The immune evasion and enterotoxin gene clusters were found in 29/36 (80%) and 33/36 (92%) of isolates, respectively.

Spread of community-acquired meticillin-resistant Staphylococcus aureus skin and soft-tissue infection within a family: implications for antibiotic therapy and prevention.

N H. Amir et al. — Thu, 29 Sep 2011 06:48:54 PDT

Outbreaks or clusters of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) within families have been reported. We describe a family cluster of CA-MRSA skin and soft-tissue infection where CA-MRSA was suspected because of recurrent infections which failed to respond to flucloxacillin. While the prevalence of CA-MRSA is low worldwide, CA-MRSA should be considered in certain circumstances depending on clinical presentation and risk assessment. Surveillance cultures of family contacts of patients with MRSA should be considered to help establish the prevalence of CA-MRSA and to inform the optimal choice of empiric antibiotic treatment.

Do guidelines for the prevention and control of methicillin-resistant Staphylococcus aureus make a difference?

Hilary Humphreys — Wed, 28 Sep 2011 10:22:14 PDT

Many countries have national guidelines for the prevention and control of methicillin-resistant Staphylococcus aureus (MRSA) that are similar in approach. The evidence base for many recommendations is variable, and often, in the drafting of such guidelines, the evidence is either not analysed or not specifically reviewed. Guidelines usually recommend screening and early detection, hand hygiene, patient isolation or cohorting, and decolonization. Although many components of a prevention and control programme appear to be self-evident, e.g. patient isolation, the scientific base underpinning these is poor, and scientifically rigorous studies are required. Nonetheless, where measures, based on what evidence there is and on common sense, are implemented, and where the necessary resources are provided, MRSA can be controlled. In The Netherlands and in other low-prevalence countries, these measures have largely kept healthcare facilities MRSA-free. In MRSA-endemic countries, such as Spain and Ireland, national guidelines are often not fully implemented, owing to apparently inadequate resources or a lack of will. However, recent studies from France and Australia demonstrate what is possible in high-prevalence countries when best practice is effectively implemented, with potentially major benefits for patients, the respective health services, and society.

When are the hands of healthcare workers positive for methicillin-resistant Staphylococcus aureus?

Eilish Creamer et al. — Mon, 07 Mar 2011 04:47:20 PST

Hand hygiene is a key component in reducing infection. There are few reports on the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) on healthcare workers' (HCWs') hands. The aim of this study was to establish whether HCWs' fingertips were contaminated with MRSA in a clinical hospital setting. The study was conducted in an acute tertiary referral hospital on four MRSA wards that were part of a larger research study on MRSA epidemiology and four other wards not included in the study. The fingertips from all categories of 523 HCWs were sampled on 822 occasions by the imprinting of fingertips on MRSA chromogenic agar plates. The type of hand hygiene agent used, if any, and the immediate prior activity of the HCW were recorded. Overall, 38/822 (5%) fingertips from 523 HCWs were MRSA-positive; 12/194 (6%) after clinical contact, 10/138 (10%) after contact with the patient's environment and 15/346 (4%) after no specific contact. MRSA was recovered on 2/61 (3%) occasions after use of alcohol hand rub, 2/35 (6%) after 4% chlorhexidine detergent, 7/210 (3%) hand washing with soap and water, and 27/493 (5%) when no hand hygiene had been performed. MRSA was recovered from HCWs on seven of the eight wards. MRSA was more frequently present on fingertips on the four non-study wards vs the four MRSA study wards [18/250 (7%), 3/201 (1%), respectively; P<=0.004]. The isolation of MRSA from HCWs' fingertips, including after hand hygiene, indicates that more educational programmes are necessary to improve the quality of hand hygiene to prevent transmission of MRSA.

Comparison of the antimicrobial activity of Ulmo honey from Chile and Manuka honey against methicillin-resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa.

Orla Sherlock et al. — Tue, 22 Feb 2011 06:42:54 PST

BACKGROUND: Honey has previously been shown to have wound healing and antimicrobial properties, but this is dependent on the type of honey, geographical location and flower from which the final product is derived. We tested the antimicrobial activity of a Chilean honey made by Apis mellifera (honeybee) originating from the Ulmo tree (Eucryphia cordifolia), against selected strains of bacteria. METHODS: Ulmo 90 honey was compared with manuka UMF 25+ (Comvita) honey and a laboratory synthesised (artificial) honey. An agar well diffusion assay and a 96 well minimum inhibitory concentration (MIC) spectrophotometric-based assay were used to assess antimicrobial activity against five strains of methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Pseudomonas aeruginosa. RESULTS: Initial screening with the agar diffusion assay demonstrated that Ulmo 90 honey had greater antibacterial activity against all MRSA isolates tested than manuka honey and similar activity against E. coli and P. aeruginosa. The MIC assay, showed that a lower MIC was observed with Ulmo 90 honey (3.1% - 6.3% v/v) than with manuka honey (12.5% v/v) for all five MRSA isolates. For the E. coli and Pseudomonas strains equivalent MICs were observed (12.5% v/v). The MIC for artificial honey was 50% v/v. The minimum bactericidal concentration for all isolates tested for Ulmo 90 honey was identical to the MIC. Unlike manuka honey, Ulmo 90 honey activity is largely due to hydrogen peroxide production. CONCLUSIONS: Due to its high antimicrobial activity, Ulmo 90 may warrant further investigation as a possible alternative therapy for wound healing.

Differences in expression of virulence genes amongst invasive and colonizing isolates of meticillin-resistant Staphylococcus aureus.

Amalina Abu Othman et al. — Fri, 11 Feb 2011 06:38:44 PST

The prevalence of meticillin-resistant Staphylococcus aureus (MRSA) is an important global concern in healthcare due to potentially life-threatening infections and difficulties in treatment. The organism can colonize the mucosa, e.g. anterior nares or result in invasive infections, e.g. bloodstream infections, through the coordinated expression of extracellular and cell-bound virulence factors (Goerke et al., 2000; Novick et al., 1993). The transcription profiles of virulence genes vary in-vivo depending on the dynamic interaction between the host environment and the pathogen. Since the dynamic environment may be differentially altered in MRSA carriage compared to infection, the expression of S. aureus virulence genes may also vary. We previously found no significant correlation between the presence of 17 virulence genes and invasiveness of MRSA isolates (O'Donnell et al., 2008) and this non-association of specific genes or combinations of genes with invasive isolates is in agreement with other larger studies (Lindsay et al., 2006). The lack of a definitive correlation between invasive S. aureus strains and the carriage of virulence genes, suggests that the expression, rather than carriage of virulence determinants in-vivo, may mediate pathogenicity.

Four country healthcare-associated infection prevalence survey: pneumonia and lower respiratory tract infections.

Hilary Humphreys et al. — Fri, 01 Oct 2010 08:56:27 PDT

In 2006, the Hospital Infection Society was funded by the respective health services in England, Wales, Northern Ireland and the Republic of Ireland to conduct a prevalence survey of healthcare-associated infection (HCAI). Here, we report the prevalence of pneumonia and lower respiratory tract infection other than pneumonia (LRTIOP) in these four countries. The prevalence of all HCAIs was 7.59% (5743 out of 75 694). Nine hundred (15.7%) of these infections were pneumonia, and 402 (7.0%) were LRTIOP. The prevalence of both infections was higher for males than for females, and increased threefold from those aged <35 to those aged>85 years (P<0.001). At the time of the survey or in the preceding seven days, 23.7% and 18.2% of patients with pneumonia and LRTIOP, respectively, were mechanically ventilated compared to 5.2% of patients in the whole study population. Meticillin-resistant Staphylococcus aureus (MRSA) was the cause of pneumonia and LRTIOP in 7.6% and 18.1% of patients, respectively (P<0.001). More patients with LRTIOP (4.2%) had concurrent diarrhoea due to Clostridium difficile compared to patients with pneumonia (2.4%), but this did not reach statistical significance. Other HCAIs were present in 137 (15.2%) of patients with pneumonia and 66 (16.4%) of those with LRTIOP. The results suggest that reducing instrumentation, such as mechanical ventilation where possible, should help reduce infection. The higher prevalence of MRSA as a cause of LRTIOP suggests a lack of specificity in identifying the microbial cause and the association with C. difficile emphasises the need for better use of antibiotics.

The need for European professional standards and the challenges facing clinical microbiology.

Hilary Humphreys et al. — Mon, 27 Sep 2010 07:16:45 PDT

Microorganisms spread across national boundaries and the professional activities of clinical (medical) microbiologists are critical in minimising their impact. Clinical microbiologists participate in many activities, e.g. diagnosis, antibiotic therapy, and there is a need for a set of professional standards for Europe with a common curriculum, to build upon the current strengths of the specialty and to facilitate the free movement of specialists within the European Union. Such standards will also better highlight the important contribution of clinical microbiologists to healthcare. There is a move to larger centralised microbiology laboratories often located off-site from an acute hospital, driven by the concentration of resources, amalgamation of services, outsourcing of diagnostics, automation, an explosion in the range of staff competencies and accreditation. Large off-site centralised microbiology laboratories are often distant to the patient and may not facilitate the early detection of microbial spread. Ultimately, the needs of patients and the public are paramount in deciding on the future direction of clinical microbiology. Potential conflicts between integration on an acute hospital site and centralisation can be resolved by a common set of professional standards and a team-based approach that puts patients first.

MRSA Screening: Can one swab be used for both culture and rapid testing? An evaluation of chromogenic culture and subsequent Hain GenoQuick® PCR amplification/detection.

Orla Sherlock et al. — Wed, 29 Jul 2009 03:28:52 PDT

We evaluated the Hain GenoQuick® (GQM) methicillin resistant Staphylococcus aureus (MRSA) assay for the rapid detection of MRSA using one swab, i.e. the same screening specimen was used first for MRSA culture and then for rapid testing by PCR, as this would be the preferred option for routine diagnostic testing. GQM detected current prevalent Irish MRSA strains incorporating all known SSCmec types including Panton-Valentine leukocidin positive strains. All methicillin resistant coagulase negative staphylococci tested were negative but three of seven gentamicin-resistant MSSA strains tested were identified as MRSA by the GQM method. The theoretical ex-vivo limit of detection of the assay was 704 colony forming units (CFU) per GQM assay reaction (1.7x104CFU/ml) when MRSA suspensions were used for DNA extraction or 1.4x103 CFU/swab (1.4x104 CFU/ml) using MRSA absorbed onto Copan screening swabs. We demonstrated that swab processing on chromogenic agar prior to PCR resulted in some inhibition of the PCR reaction, increasing the limit of detection of the assay by a factor of 4. Based on the processing of 540 screening specimens (nasal and groin) by culture first and GQM second, the specificity and positive predictive value were both 100%, the negative predictive value was 92%, and the sensitivity was 57%. Culture followed by PCR from one specimen is not optimal for the rapid detection of MRSA. Further laboratory validation of the GQM assay is required to determine the true diagnostic sensitivity and value of this kit in routine microbiology laboratories, either with PCR before culture or using two specimens

Distribution of virulence genes among colonising and invasive isolates of methicillin-resistant Staphylococcus aureus.

Sinead O'Donnell et al. — Wed, 15 Jul 2009 03:54:11 PDT