Robert G. Masterton

Guidelines for the management of hospital-acquired pneumonia in the UK: Report of the Working Party on Hospital-Acquired Pneumonia of the British Society for Antimicrobial Chemotherapy

Abstract These evidence-based guidelines have been produced after a systematic literature review of a range of issues involving prevention, diagnosis and treatment of hospital-acquired pneumonia (HAP). Prevention is structured into sections addressing general issues, equipment, patient procedures and the environment, whereas in treatment, the structure addresses the use of antimicrobials in prevention and treatment, adjunctive therapies and the application of clinical protocols. The sections dealing with diagnosis are presented against the clinical, radiological and microbiological diagnosis of HAP. Recommendations are also made upon the role of invasive sampling and quantitative microbiology of respiratory secretions in directing antibiotic therapy in HAP/ventilator-associated pneumonia.

Guidelines for UK practice for the diagnosis and management of methicillin-resistant Staphylococcus aureus (MRSA) infections presenting in the community

These guidelines have been developed by a Working Party convened on behalf of the British Society for Antimicrobial Chemotherapy. Their aim is to provide general practitioners and other community- and hospital-based healthcare professionals with pragmatic advice about when to suspect MRSA infection in the community, when and what cultures should be performed and what should be the management options, including the need for hospitalization.

Determining the value of antimicrobial surveillance programs.

Antimicrobial surveillance programs provide important information on the development of bacterial resistance mechanisms in different geographical regions. Data concerning these mechanisms and patterns of antimicrobial resistance allows the implementation of changes in antimicrobial prescribing practices and infection control interventions. The three most widely known global surveillance programs currently in active operation are: The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC), The SENTRY Antimicrobial Surveillance Program, and The Alexander Project. This presentation reviews these surveillance programs, using a set of key criteria in order to assess the significance of each program in monitoring the spread of antimicrobial resistance. The content of the MYSTIC Program monitors the in vitro performance of meropenem in hospital units in which this drug is actively prescribed. This distinguishes the MYSTIC Program from the other two major surveillance programs as it seeks to correlate antimicrobial resistance data, collected from high carbapenem usage institutions, with antimicrobial prescribing patterns over time. The MYSTIC Program and other assessed networks appear to be both valuable and complementary in their design and function.

Nasal Swab Screening for Methicillin-Resistant Staphylococcus aureus—How Well Does It Perform? A Cross-Sectional Study

OBJECTIVE To determine the proportion of methicillin-resistant Staphylococcus aureus (MRSA) detections identified by nasal swabbing using agar culture in comparison with multiple body site testing using agar and nutrient broth culture. DESIGN Cross-sectional study. PATIENTS Adult patients admitted to 36 general specialty wards of 2 large hospitals in Scotland. METHODS Patients were screened for MRSA via multiple body site swabs (nasal, throat, axillary, perineal, and wound/invasive device sites) cultured individually on chromogenic agar and pooled in nutrient broth. Combined results from all sites and cultures provided a gold-standard estimate of true MRSA prevalence. RESULTS This study found that nasal screening performed better than throat, axillary, or perineal screening but at best identified only 66% of true MRSA carriers against the gold standard at an overall prevalence of 2.9%. Axillary screening performed least well. Combining nasal and perineal swabs gave the best 2-site combination (82%). When combined with realistic screening compliance rates of 80%-90%, nasal swabbing alone probably detects just over half of true colonization in practice. Swabbing of clinically relevant sites (wounds, indwelling devices, etc) is important for a small but high-prevalence group. CONCLUSIONS Nasal swabbing is the standard method in many locations for MRSA screening. Its diagnostic efficiency in practice appears to be limited, however, and the resource implications of multiple body site screening have to be balanced against a potential clinical benefit whose magnitude and nature remains unclear.

Universal screening for meticillin-resistant Staphylococcus aureus: interim results from the NHS Scotland pathfinder project

Following recommendations from a Health Technology Assessment (HTA), a prospective cohort study of meticillin-resistant Staphylococcus aureus (MRSA) screening of all admissions (N=29 690) to six acute hospitals in three regions in Scotland indicated that 7.5% of patients were colonised on admission to hospital. Factors associated with colonisation included re-admission, specialty of admission (highest in nephrology, care of the elderly, dermatology and vascular surgery), increasing age, and the source of admission (care home or other hospital). Three percent of all those who were identified as colonised developed hospital-associated MRSA infection, compared with only 0.1% of those not colonised. Specialties with a high rate of colonisation on admission also had higher rates of MRSA infection. Very few patients refused screening (11 patients, 0.03%) or had treatment deferred (14 patients, 0.05%). Several organisational issues were identified, including difficulties in achieving complete uptake of screening (88%) or decolonisation (41%); the latter was largely due to short duration of stay and turnaround time for test results. Patient movement resulted in a decision to decolonise all positive patients rather than just those in high risk specialties as proposed by the HTA. Issues also included a lack of isolation facilities to manage patients with MRSA. The study raises significant concerns about the contribution of decolonisation to reducing risks in hospital due to short duration of stay, and reinforces the central role of infection control precautions. Further study is required before the HTA model can be re-run and conclusions redrawn on the cost and clinical effectiveness of universal MRSA screening.

The new treatment paradigm and the role of carbapenems.

The global increase in antibiotic resistance is promoted by the widespread use of broad-spectrum antibiotics, creating a continuous selective pressure on bacteria. This resistance is depleting the number of effective antimicrobial agents. Since there have been few new agents active against Gram-negative bacteria in particular developed over the last two decades, it is important to make the most of existing antibiotics. Therefore, rational use of antimicrobial agents is vital in establishing a successful strategy to control and prevent both the clinical impact and the development of further resistance. Careful selection of the appropriate antimicrobial agent combined with correct dosing, duration of treatment and route of administration are all important to the success of this strategy and need to be coupled with antimicrobial resistance surveillance. Progress against the treatment strategy approach for optimising clinical outcomes whilst preventing antibacterial resistance based on antibiotic de-escalation will be reviewed with particular emphasis on the role of the carbapenems. This approach attempts to balance the need to provide appropriate initial treatment whilst limiting the emergence of antibacterial resistance.

A retrospective cohort study into acquisition of MRSA and associated risk factors after implementation of universal screening in Scottish hospitals

OBJECTIVE To estimate the proportion of patients who acquire methicillin-resistant Staphylococcus aureus (MRSA) while in hospital and to identify risk factors associated with acquisition of MRSA. DESIGN Retrospective cohort study. PATIENTS Adult patients discharged from 36 general specialty wards of 2 Scottish hospitals that had implemented universal screening for MRSA on admission. METHODS Patients were screened for MRSA on discharge from hospital by using multisite body swabs that were tested by culture. Discharge screening results were linked to admission screening results. Genotyping was undertaken to identify newly acquired MRSA in MRSA-positive patients on admission. RESULTS Of the 5,155 patients screened for MRSA on discharge, 2.9% (95% confidence interval [CI], 2.43-3.34) were found to be positive. In the subcohort screened on both admission and discharge (n = 2,724), 1.3% of all patients acquired MRSA while in hospital (incidence rate, 2.1/1,000 hospital bed-days in this cohort [95% CI, 1.5-2.9]), while 1.3% remained MRSA positive throughout hospital stay. Three risk factors for acquisition of MRSA were identified: age above 64 years, self-reported renal failure, and self-reported presence of open wounds. On a population level, the prevalence of MRSA colonization did not differ between admission and discharge. CONCLUSIONS Cross-transmission of MRSA takes place in Scottish hospitals that have implemented universal screening for MRSA. This study reinforces the importance of infection prevention and control measures to prevent MRSA cross-transmission in hospitals; universal screening for MRSA on admission will in itself not be sufficient to reduce the number of MRSA colonizations and subsequent MRSA infections.

Investigation into the selection frequency of resistant mutants and the bacterial kill rate by levofloxacin and ciprofloxacin in non-mucoid Pseudomonas aeruginosa isolates from cystic fibrosis patients

The frequency by which resistant Pseudomonas aeruginosa strains could be selected was compared for two antibiotics, levofloxacin and ciprofloxacin. Seven distinct strains were cultured on plates containing 1x, 2x, 4x and 8x the minimum inhibitory concentration (MIC) of the antibiotic under investigation. Resistant mutants were more readily isolated by growth on culture plates that contained ciprofloxacin, and the resulting MIC of the resistant mutant was also more frequently increased. Time-kill studies on comparable strains where the MIC for both antibiotics had increased by at least fourfold showed no difference between the two agents.

The Treatment of Pseudomonas aeruginosa Meningitis Old Regime or Newer Drugs

Currently intravenous ceftazidime with or without an aminoglycoside or alternatively ciprofloxacin are the recommended antibiotics of choice in Pseudomonas aeruginosa meningitis. A case of atraumatic, spontaneous Ps. aeruginosa meningitis in a child with acute lymphoblastic leukaemia is described. Despite the organism demonstrating in vitro sensitivity to ceftazidime, netilmicin and ciprofloxacin, intravenous therapy with these drugs failed to sterilise the cerebrospinal fluid (CSF). Both netilmicin and ciprofloxacin failed to attain therapeutic levels in the CSF. Intrathecal aminoglycoside therapy via an intraventricular reservoir was successful in eradicating the infection. In children with meningitis due to Ps. aeruginosa where intravenous therapy is unsuccessful despite in vitro sensitivity to recommended antibiotics; intraventricular medications should be commenced as soon as possible.

Investigation of infection in the neutropenic patient with fever.

Episodes of infection occurring in neutropenic patients are often associated with high levels of morbidity and mortality and prompt, accurate diagnosis allowing the rapid instigation of appropriate treatment can lead to an improved outcome. Recent developments in laboratory technology have increased the range of investigations available to the physician. The improved sensitivity of traditional microbiological culture, methods for antigen and antibody detection and the advances in molecular biology are among the reasons for an increased ability to detect both familiar and novel pathogens. This article describes the current methods available for determining the aetiology of an infectious episode in these patients. A plan of management for investigation of febrile episodes in neutropenic patients is suggested.