Epidemiological typing of MRSA isolates from blood cultures taken in Irish hospitals participating in the European Antimicrobial Resistance Surveillance System (1999-2003).

Between 1999 and 2003, meticillin-resistant Staphylococcus aureus (MRSA) isolates recovered from blood cultures in Irish hospitals that participate in the European Antimicrobial Resistance Surveillance System were investigated by epidemiological typing using antibiogram-resistogram (AR) typing, biotyping, and DNA macrorestriction digestion using SmaI followed by pulsed-field gel electrophoresis (PFGE). PFGE patterns were assigned five-digit pulsed-field type (PFT) numbers, and PFTs of apparently related patterns were abbreviated to two-digit PFT groups (PFGs). AR and PFGE typing results were combined to produce AR-PFG types. Representative isolates of each AR-PFG type recovered in 2002 were typed by multilocus sequence typing and staphylococcal cassette chromosome (SCC) mec analysis. Isolates from 1999 and 2000 were also typed by phage typing. The extent to which epidemiological types of MRSA from blood cultures could be extrapolated to the total MRSA population was investigated by comparing results obtained with isolates from the total MRSA population versus those obtained with blood cultures during three study periods. Over the 5 years from 1999 to 2003, 1,580 blood culture isolates from 1,495 patients were analysed. Typeability and discriminatory indices were as follows: AR typing, 1 and 0.97; phage typing, 0.29 and 0.89; PFGE, 0.99 and 0.95; AR-PFG typing, 1 and 0.95. The most frequently occurring AR-PFG types were 06-01, 07-02, 13-00, and 14-00 and were exhibited by 57, 7, 14, and 12% of isolates, respectively. During the study period, the distribution of AR-PFG type changed markedly, with the prevalence of one type (AR-PFG 06-01) increasing by 880%, from 22% (39/181) in 1999 to 80% (343/430) in 2003. Investigation of whether epidemiological types among blood culture isolates of MRSA were representative of the total MRSA population showed that there was no significant difference in most instances. MLST and SCCmec typing showed that AR-PFG types 06-01, 07-02, 13-00, and 14-00 were ST22-MRSA-IV, ST36-MRSA-II, ST8-MRSA-IID, and ST8-MRSA-IIE, respectively.

Effective control of dental chair unit waterline biofilm and marked reduction of bacterial contamination of output water using two peroxide-based disinfectants.

Bacterial biofilm in dental unit waterlines (DUWs) is a widespread problem, and poses a potentially significant risk of infection to dental staff and patients, particularly those who are medically compromised or immunocompromised. The purpose of the present study was to investigate the level of bacterial contamination of dental chair unit output water in the Dublin Dental Hospital, and to investigate the efficacy of two hydrogen peroxide-based disinfectants in reducing bacterial loads to < or =200 cfu/mL as recommended by the American Dental Association. The chemical quality of dental chair unit input and output water was well within the limits recommended for potable water. Water supplied to the units yielded an average aerobic heterotrophic bacterial cell density of 184 cfu/mL. However, the corresponding density in output water was considerably higher; the average cell density in water from the three-in-one air/water syringes and cup fillers in 12 chairs was 8200 and 4300 cfu/mL, respectively. Dental unit water obtained from 18 separate reservoir-supplied units in general practices in the Dublin area yielded an average of 66000 cfu/mL. The bacterial species found were predominantly environmental organisms, which were also present at low levels in the input water. Some of the species identified (e.g., Burkholderia cepacia and Pseudomonas fluorescens) are known opportunistic pathogens. The capacity of two disinfectants, Sterilex Ultra and Sanosil, to reduce bacterial contamination to safe levels was compared. In a controlled study, once weekly overnight (15 h) disinfection using either agent reduced the bacterial density to below the American Dental Association recommended level of 200 cfu/mL. However, once disinfection ceased the bacterial loads increased to unacceptably high levels within three weeks. Electron microscopic analysis showed that both disinfectants markedly reduced biofilm in the DUWs, but the biofilm rapidly became extensive again when once weekly disinfection ceased. While both disinfectants were equally effective in lowering the bacterial counts to acceptable levels, Sterilex Ultra was associated with clogging of DUWs in some dental chair units after repeated usage, suggesting that Sanosil is a more suitable agent for routine use.

Strain variation in the MRSA population over a 10-year period in one Dublin hospital.

Between 1989 and 1998, the number of patients carrying methicillin-resistant Staphylococcus aureus in one Dublin hospital increased fourfold, and the antibiogram-resistogram (AR) type distribution changed. In 1989, the predominant AR types were AR01 and AR02; in 1993, AR14 predominated; and in 1994, AR14 and AR13 were predominant. By 1998, the prevalence of AR13 and AR14 had declined and AR06 and AR07 were observed more frequently. In 1989, 65% of isolates were nontypeable using the International Basic Set of Typing Phages. This percentage increased to 78% in 1998. Total cellular DNA macrorestriction analysis reflected the changing AR type distribution. No vancomycin-intermediate isolates were recovered, but possible heteroresistance was observed in 2.7% of isolates. High-level mupirocin resistance occurred in 4% of isolates, and 32% exhibited low-level resistance.

Candida dubliniensis candidaemia in an HIV-positive patient in Ireland.

Candida dubliniensis was first identified in Dublin in 1995 in oral isolates recovered from human immunodeficiency virus (HIV)-infected individuals. Although C. dubliniensis has been primarily recovered from the oral cavities of HIV-infected individuals, the number of reports describing its isolation from HIV-negative individuals, including cases of candidaemia, is growing. To date there has only been one report of C. dubliniensis candidaemia in an HIV-infected patient, in this case from the USA. In the present study, 2 Candida isolates recovered from blood samples were presumptively identified as C. dubliniensis on the basis of their dark green coloration on CHROMagar Candida medium and lack of growth at 45 degrees C. This identification was confirmed by carbohydrate assimilation profile analysis and by polymerase chain reaction (PCR) analysis with C. dubliniensis-specific PCR primers. Both isolates were susceptible to fluconazole. The isolates were found retrospectively to be from a single HIV-infected patient who was receiving broad-spectrum antibacterials at the time of isolation of C. dubliniensis from blood. This study represents the first documented case of C. dubliniensis bloodstream infection in Ireland and is only the second case of C. dubliniensis bloodstream infection identified in an HIV-infected individual anywhere in the world.

Rate of carriage of Serratia marcescens in patients with and without evidence of infection.

The epidemiology of Serratia marcescens is poorly understood. We designed a study to investigate carriage sites of the organism, and possible modes of transmission of infection. Using Sorbitol-MacConkey agar with colistin 200 IU/ml and MacConkey agar with a 10 microg colistin disc we performed cultures from various sites in patients already infected with S. marcescens. Over the same period of time we also investigated all patients in the intensive care unit (ICU) for colonization with the agent. Environmental screening was performed in the ICU only. Of 37 infected patients, 65% demonstrated carriage at a second site and 43% at multiple sites. Throat carriage was found in 59%, faecal carriage in 42%, nasal carriage in 31% and urinary carriage in 22%. Carriage over several weeks was found in 22%. Of 40 ICU patients, 10% demonstrated nasal and/or throat carriage. Environmental screening yielded 4 isolates. All ICU patient strains and a strain from the ICU bedpan macerator were O14:K14 with similar random amplified polymorphic DNA types. These results show that patients with S. marcescens infection are likely to carry the organism at multiple sites and that carriage may be prolonged. A significant level of carriage was also found in non-infected patients in a unit where the organism was prevalent.

The prevalence of methicillin-resistant staphylococcus aureus among the residents of six nursing homes for the elderly.

Admissions to Irish hospitals from nursing homes are recognized as a high-risk category for methicillin-resistant Staphylococcus aureus (MRSA) colonization. This study was conducted between August 1994 and May 1995 to determine the prevalence of MRSA within six Eastern Health Board elderly care nursing homes. A point prevalence survey was conducted in each home on two separate occasions at an interval of five to six months. An MRSA prevalence rate of 8.6% (65 of 754 residents) was recorded for the first survey, and an increased prevalence rate 10.1% (75 of 743 residents) for the second. The prevalence rates within individual homes varied from 1-27%. The body site most commonly colonized was the nares (83%), as anticipated. The main unexpected finding was a low wound colonization rate of 12%, which increased to only 20%, among MRSA positive residents. The dynamic state of MRSA colonization within nursing homes was documented among the 587 residents screened in both surveys. The MRSA positive status of 19 residents remained unchanged, but 32 who were initially positive became negative, while 34 residents acquired the organism. Twenty-six of the 56 (46%) residents identified as MRSA positive in the second survey had acquired the organism within the nursing home over the preceding five to six months. These findings suggest that 'infection control' interventions could have a significant impact on MRSA prevalence within nursing homes.

Risk factors for colonization with methicillin-resistant Staphylococcus aureus among nursing home residents.

Risk factors predictive of methicillin-resistant Staphylococcus aureus (MRSA) colonization in 786 of 910 nursing home residents were evaluated. A customized questionnaire was completed by theresidents, who were screened for MRSA. The risk factors significantly associated with MRSA colonization were male sex, age >80 years, residence in the nursing home for

VRE in the Republic of Ireland: clinical significance, characteristics and molecular similarity of isolates.

There have been increasing reports worldwide of vancomycin resistant enterococci (VRE) since they were first noted over ten years ago. This study sought to investigate the clinical significance of VRE in Ireland and to compare the phenotypic, genotypic and molecular characteristics of isolates recovered from patients in different institutions. The relative contribution of inter-hospital transmission of strains to the dissemination of VRE in Ireland was assessed. Hospital surveillance for VRE is not well established in Ireland. The organism has been detected in seven hospitals. Detection has been predominantly in oncology inpatients in large tertiary referral hospitals in the Dublin metropolitan area in whom strains generally represent asymptomatic gastrointestinal tract colonization. The predominant species is E. faecium with the Van A resistance phenotype. Twenty-seven (87) of 31 isolates from one unit were shown to be of the same or closely related strain as were 10 (63%) of 16 from another unit, indicating significant nosocomial transmission within institutions. There was no evidence for inter-hospital transmission of VRE. VRE is established in Ireland and nosocomial transmission readily occurs. Regular surveillance for VRE is indicated in high-risk populations in large institutions, specific risk factors for the acquisition of VRE need to be defined and optimal control and preventative strategies need to he instituted to detect and preempt the spread of this organism.

An outbreak of multiply resistant Serratia marcescens: the importance of persistent carriage.

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.

Comparison between McCoy cell line and HeLa cell line for detecting Helicobacter pylori cytotoxicity: clinical and pathological relevance.

BACKGROUND: Cell culture assay is an accurate test for detecting Helicobacter pylori cytotoxicity. AIMS: To evaluate McCoy cells for detecting Helicobacter pylori cytotoxicity by comparing with HeLa cells, and determine the association of cytotoxic strains with endoscopic and histological findings. METHODS: Helicobacter pylori isolates from 68 dyspeptic patients and 11 asymptomatic volunteers were tested. 180 microl (1.8 x 10(4) cells) of grown McCoy or HeLa cell suspension was seeded into each well of a 96-well microtitre tray and the medium was replaced once after 24 hours. Sonicate (20 microl) of each isolate was then added to the wells, in duplicate. After 24 and 48 hours incubation, intracellular vacuolation was assessed by inverted light microscopy. RESULTS: Using McCoy cells 57% of isolates showed cytotoxicity (23% weak and 34% strong), while using HeLa cells 30% of isolates showed strong cytotoxicity. All isolates toxic in HeLa cells were also toxic in McCoy cells. The prevalence of cytotoxic strains was not significantly different between the endoscopic findings; 50% in normal endoscopy, 60% in non-ulcer dyspepsia and 59% in peptic ulcer disease. However, cytotoxic strains were more common in subjects with severe histological gastritis than in those with normal mucosa or mild gastritis (66% vs 30%, p<0.01). Similarly, the prevalence of cytotoxic strains was also higher in subjects with active gastritis than in those without (64% vs 23%, p<0.01). CONCLUSIONS: McCoy cells are more sensitive than HeLa cells for detecting Helicobacter pylori cytotoxicity in vitro. There is an association between cytotoxic strains and the severity and activity of histological gastritis.

An outbreak of an unusual strain of Serratia marcescens in two Dublin hospitals.

We describe a serious outbreak of infection caused by a strain of Serratia marcescens in two Dublin hospitals which occurred over an 11 week period and affected a total of 15 patients. A contaminated bed-pan macerator in the Intensive Care Unit of one hospital was identified as the possible source of infection and spread of the organism probably occurred via hand transmission by hospital personnel and via patient transfer to a second hospital. All isolates of S. marcescens involved in the outbreak had the same antimicrobial susceptibility pattern, with reduced susceptibility to gentamicin, cefotaxime and ciprofloxacin. Epidemiological typing revealed that the strains of S. marcescens isolated in the outbreak were of an uncommon serotype, O21:K14, and using pulsed-field gel electrophoresis, XbaI DNA macrorestriction profiles clustered at 90% similarity. The DNA patterns of the outbreak strain were also highly similar to S. marcescens isolates of the same serotype recovered from a separate Dublin hospital during the same time period as the outbreak described here. In addition, the isolates clustered at 82% similarity with strains of the same serotype from a retrospective collection of S. marcescens isolates from various hospitals in the Dublin area, indicating that these may be genetic variants of the same strain. Although the outbreak was brought under control following implementation of infection control measures, a significant number of similar O:21 isolates of S. marcescens have since been identified in four Dublin hospitals. These results suggest the unique spread of a single strain of S. marcescens in Dublin hospitals.

Metronidazole resistance reduces efficacy of triple therapy and leads to secondary clarithromycin resistance.

There has been a significant increase in the prevalence of H. pylori resistance to metronidazole in recent years, while clarithromycin resistance is still relatively rare. In this study we assessed: (1) the effect of primary H. pylori resistance to metronidazole and clarithromycin on the clinical efficacy of a one-week regimen consisting of omeprazole, metronidazole, and clarithromycin; and (2) the rate of acquisition of secondary antimicrobial resistance after treatment failure. Eighty-seven patients with duodenal ulceration or nonulcer dyspepsia were included in the study. The primary metronidazole and clarithromycin resistance rates were 35.6% and 3.4%, respectively (all three pretreatment clarithromycin resistant strains had concurrent metronidazole resistance). H. pylori was eradicated in 81.6% of patients. The eradication rate for fully sensitive isolates was 98.2% (55/56) but was significantly reduced to 57.1% (16/28) for isolates that were resistant to metronidazole alone and 0% (0/3) in cases of dual resistance (P < 0.001). Secondary resistance to clarithromycin was acquired in 58.3% of cases of treatment failure. In areas of high prevalence of primary metronidazole resistance, this is a significant cause of treatment failure with this triple therapy regimen. This leads to the selection of strains with dual resistance that are difficult to eradicate and may contribute to an increase in the prevalence of clarithromycin resistance. In such areas an alternative first-line treatment should be prescribed.

The use of RAPD-PCR as a typing method for Serratia marcescens.

Serratia marcescens has emerged in the last few years as an important nosocomial pathogen. Many methods for typing this organism have been described. In this study the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) was shown to be a convenient typing method for S. marcescens. Different combinations of primers previously used for typing other gram-negative bacilli were assessed. The combination of primer HLWL-74 and 1254 gave distinguishable patterns for different serotypes and proved to be the most satisfactory. By applying this combination to 175 isolates of S. marcescens, which could be classified into 38 groups on the basis of serotyping and phage typing, 73 different RAPD patterns with good reproducibility were obtained. This is, to our knowledge, the first application of the method to a large collection of S. marcescens representing a wide range of serotypes.

Recurrence of Helicobacter pylori infection after successful eradication: nature and possible causes.

Recurrence of Helicobacter pylori infection after successful eradication occurs and is associated with relapse of gastroduodenal diseases. The aims of this paper were to assess the incidence and identify the nature and possible causes of recurrence of the infection. A broad-based Medline search was performed to identify all related publications addressing recurrence of the infection between 1986 and 1995. The 12-month recurrence rate varied among the different studies from 0 to 41.5%. A few studies showed 18- to 24-month recurrence rates, which ranged between 0 and 21.4%. Limited data, obtained using molecular fingerprinting techniques, have shown that in most cases recurrence is due to recrudescence of the original strain; a few cases appear to be due to reinfection with a new strain. Recrudescence is most likely during the first 12 months after apparent eradication. Despite the high sensitivity and specificity of the available individual tests for detecting H. pylori infection in untreated patients, no technique alone is sensitive enough to monitor eradication when the four-week-rule definition for eradication is used. A combination of two or more techniques increases sensitivity. Sensitivity and specificity are increased when biopsies are taken from both gastric antrum and corpus. The best treatments have the lowest recurrence rates and recurrence is rare when the eradication rate is over 90%. Individual susceptibility and reexposure to H. pylori are suggested as two major causes of reinfection.