Is methicillin-resistant Staphylococcus aureus more virulent than methicillin-susceptible S. aureus? A comparative cohort study of British patients with nosocomial infection and bacteremia.

Staphylococcus aureus is the most common cause of hospital-acquired bacteremia. From 1995 through 2000, data on age, sex, patient specialty at time of first bacteremia, primary and secondary sites of infection, delay in initiating antimicrobial therapy, and patient outcome were prospectively recorded for 815 patients with nosocomial S. aureus bacteremia. The proportion of patients whose death was attributable to methicillin-resistant S. aureus (MRSA) was significantly higher than that for methicillin-susceptible S. aureus (MSSA) (11.8% vs. 5.1%; odds ratio [OR], 2.49; 95% confidence interval [CI], 1.46-4.24; P<.001). After adjustment for host variables, the OR decreased to 1.72 (95% CI, 0.92-3.20; P=.09). There was no significant difference between rates of disseminated infection (7.1% vs. 6.2% for MRSA-infected patients and MSSA-infected patients, respectively; P=.63), though the rate of death due to disseminated infection was significantly higher than death due to uncomplicated infection (37% vs. 10% for MRSA-infected patients [P<.001] and 37% vs. 3% for MSSA-infected patients [P<.001]). There was a strong statistical trend toward death due to nosocomial MRSA infection and bacteremia, compared with MSSA.

Stool culture: are you getting value for money?

AIMS: To assess the best medium for primary isolation of enteric pathogens; to determine the need for a second primary culture medium; and to gather information on stool culture media used in 20 other randomly selected laboratories. METHODS: Specimens were cultured on desoxycholate citrate agar (DCA), Hektoen enteric agar (Hektoen), and xylose lysine deoxycholate agar (XLD). Non-lactose fermenters were screened with Rapidec Z (bio-Mérieux) and identified with API 10S (bio-Mérieux) where appropriate. Shigellas were identified with API 20E (bio-Mérieux) and serology, and salmonellas biochemically and by serology. A telephone survey was carried out to enquire into different culture practices and whether they had been evaluated for cost effectiveness. RESULTS: The isolation rate of enteric pathogens on primary stool culture media was 97% on DCA, 88% on XLD, and 76% on Hektoen. Seventeen of 18 shigellas grew on DCA, 13 of 18 on XLD, and 14 of 18 on Hektoen. DCA missed one Salmonella, XLD three, and Hektoen 13. XLD and Hektoen both missed Yersinia enterocolitica. The telephone survey revealed a diverse range of both primary and subculture plates. There was little evidence of evaluation of stool media, but firm personal convictions concerning the advantages and disadvantages of each type of medium at each stage of culture. CONCLUSIONS: DCA performed best and was the most cost effective of the three media. Neither XLD nor Hektoen were satisfactory as primary culture media because they grew fewer pathogens than DCA.

Enteric media: pre-poured or in-house?

AIMS: (1) To evaluate the performance of in-house and pre-poured commercially available enteric agar by challenge with a large number of positive clinical specimens. (2) To set the standard (critical independent evaluation) which new products should reach. (3) To publish this information, so that others can make informed decisions about enteric media. METHODS: Thirteen media of anonymous source were challenged with "known" positive stool samples. RESULTS: In-house desoxycholate citrate agar performed best for overall pathogen isolation rates, for shigella isolation rates, and for most pathogens available on primary culture. CONCLUSIONS: Desoxycholate citrate agar made by our own laboratory yielded the most pathogens and proved the most effective.

The therapeutic use of metronidazole in anaerobic infection: six years' experience in a London hospital.

For the past 6 years at St. Thomas' Hospital, metronidazole has been used to treat proven anaerobic infection at a wide variety of sites and of varying clinical severity. Throughout this period, intravenous, oral, and rectal preparations of the drug have been available. Initial experience was predominantly in abdominal sepsis where excellent therapeutic results were obtained and treated patients included many with mixed aerobic/anaerobic infection in whom metronidazole was used alone. Metronidazole also has been used either alone or in combination, most frequently with amoxicillin, to treat many other anaerobic infections: head and neck, pleuropulmonary, genital tract, bone and joint, skin and soft tissue, and cases of fusobacterial septicemia (necrobacillosis). Although, as in pyogenic infection of any etiology, surgical intervention often is required in anaerobic sepsis, there is little doubt of the useful therapeutic role of metronidazole in these patients. Increasing awareness of the wide clinical spectrum of human anaerobic infections has led to increasing therapeutic dependence on metronidazole with as yet little evidence of bacterial resistance.

Staphylococcal tricuspid valve endocarditis in patients with structurally normal hearts and no evidence of narcotic abuse.

We report four cases of staphylococcal tricuspid valve endocarditis in patients with structurally normal hearts and no evidence of intravenous drug abuse. The only risk factor was superficial skin sepsis in three of these patients. Medical therapy was successful in all four cases.

Hospital acquired native valve endocarditis: analysis of 22 cases presenting over 11 years.

OBJECTIVE: To analyse hospital acquired infective endocarditis cases with respect to age, sex, clinical, laboratory, and echocardiographic features, predisposition, complications, surgery, mortality, and diagnostic criteria. DESIGN: Prospective cohort study. SETTING: Teaching hospital. PATIENTS: A series of 200 patients with infective endocarditis presenting over 11 years, 168 with native valve infective endocarditis, of whom 22 acquired this infection in hospital. RESULTS: 22 (14%) of the 168 cases of native valve infection were hospital acquired. The most common pathogens were staphylococci (77%). Two thirds of patients had no cardiac predisposition; one third had end stage renal disease. The most common source of infection was vascular access sites (73%). Eleven patients died. In 11 cases, infective endocarditis was proven pathologically (six at necropsy, five during surgery) and analysis of these showed that 45% were classed as probable by the Beth Israel criteria, 73% as definite by the Duke criteria, and 91% as definite by our suggested modifications of the Duke criteria. Figures for the 11 cases not proven pathologically were 27%, 73%, and 91%, respectively. Five of the 22 cases (22%) were rejected by the Beth Israel criteria but none were rejected by the Duke criteria with or without our modifications. CONCLUSIONS: Hospital acquired infective endocarditis is difficult to diagnose. The Duke criteria have improved diagnostic sensitivity and our modifications have improved it further. Mortality is high but has been reduced by surgery. This serious infection could, in many cases, be prevented by improved care of intravascular lines and prompt removal when obviously infected.

Culture-negative endocarditis: contribution of bartonella infections.

Two cases of bartonella endocarditis are described: one in a 55 year old homeless alcoholic man, caused by Bartonella quintana; the other in a 41 year old male with a history of exposure to cat fleas, caused by B henselae. Serological testing and polymerase chain reaction of the excised valves were used to identify the organisms. False positive serology for chlamydia was detected in one case.

Covert multi-focal infective arthritis.

Six patients with pre-existing rheumatic joint disease presented with overwhelming septicaemia but without overt signs of joint inflammation. Joint aspirates demonstrated multifocal staphylococcal infective arthritis. Despite intensive care all six died from the infection or its immediate sequelae. The contrast between this clinical entity and classical infective arthritis, presenting with one or more swollen, tender joints, is discussed.

Non-typhoidal Salmonella bacteraemia without gastroenteritis: a marker of underlying immunosuppression. Review Of cases at St. Thomas' Hospital 1970-1999.

OBJECTIVES: To classify non-typhoidal salmonella bacteraemia according to clinical presentation, and to study how this correlates with the presence of underlying immunosuppression. METHODS: We analysed data collected prospectively for all 82 cases of non-typhoidal salmonella bacteraemia presenting to St. Thomas' Hospital between 1970 and 1999. RESULTS: Patients presented with one of three syndromes: diarrhoea, an extra-intestinal focus of infection, or isolated fever with no focus. Only 18% of those with diarrhoea had underlying immunosuppression, compared with 80% of those with extra-intestinal focal infections (P= 0.001) and 80% of those with no focus (P= 0.0001). There was no significant association between salmonella serotype and underlying immunosuppression. Salmonella enteritidis isolates, especially phage type 4, increased significantly during the last decade (P= 0.001). The presentation of non-typhoidal salmonella bacteraemia in the absence of diarrhoea prompted the diagnosis of HIV in two patients. CONCLUSION: Underlying immunosuppression should be excluded in patients presenting with non-typhoidal salmonella bacteraemia in the absence of gastroenteritis. This may lead to an earlier diagnosis of HIV.

Pneumococcal cellulitis: a rare manifestation of pneumococcaemia in adults.

An elderly woman with rheumatoid arthritis of 8 years duration and for which she was receiving indomethacin, developed multifocal cellulitis with subsequent necrosis. Streptococcus pneumoniae type 1 was isolated from her blood and from blister fluid. Previous reported cases are summarised.

A pseudolymphomatous skin reaction secondary to flucloxacillin.

We report the first case of a pseudolymphomatous skin reaction precipitated by flucloxacillin. Skin histology was suggestive of a cutaneous lymphoma, and DNA analysis by single stranded conformational polymorphism (SSCP) demonstrated T-cell receptor gamma gene monoclonality. Withdrawal of flucloxacillin led to immediate clinical improvement and gradual resolution of skin rash and lymph nodes.

Intraperitoneal vancomycin and ceftazidime in the treatment of CAPD peritonitis.

The use of intraperitoneal vancomycin and ceftazidime in the treatment of 64 episodes of CAPD peritonitis is reported. Serum and dialysate antibiotic concentrations were measured in 19 of these and the maximum serum vancomycin level recorded was 30 mg/l. Culture of the dialysate was sterile in 52% of the cases, staphylococci were isolated in 30% and the infection rate during 1983 was 2.22 episodes per patient-year. This antibiotic combination has proven safe and effective and easily administered by the patients.

The relevance of microbiology in the management of anorectal sepsis.

Eighty patients with anorectal sepsis were studied over three years. All abscesses were drained and pus was submitted for culture. If a fistula was found when the abscess was drained it was laid open otherwise a second examination under anaesthetic was performed within 7-10 days. In no case was sterile pus obtained. Gut aerobes, predominantly Escherichia coli, were isolated from 49 of 53 (92.5%) of patients with a fistula and 8 of 27 (29.6%) of those without. 'Gut-specific bacteroides' predominantly Bacteroides fragilis were isolated from 47 of 53 (88.7%) patients with a fistula and 5 of 27 (18.5%) of those without. Anaerobes not specific to the gut, predominantly B. asaccharolyticus, B. ureolyticus, peptococci and peptostreptococci, in the absence of those specific to the gut, were isolated from 2 of 53 patients with a fistula (3.8%) and 17 of 27 (63%) of those without. Staphylococcus aureus was isolated from only 1 of 53 (1.9%) patients with a fistula but from 8 of 27 (29.6%) of those without. It is concluded that only patients with gut-specific organisms should be submitted to a second examination under anaesthetic and that culture of pus in anorectal sepsis is an essential part of its management.

Meningitis after trans-sphenoidal excision of pituitary tumours.

Between 1974 and 1986, eleven of 114 patients undergoing trans-sphenoidal removal of pituitary tumours developed meningitis despite prophylaxis, usually with chloramphenicol. Nine patients had cerebrospinal fluid rhinorrhoea and one died. A variety of pathogens was isolated, including enterobacteria, and four of the eleven were resistant to the antibiotics given as prophylaxis. Enterobacterial meningitis was always associated with infection of the sphenoidal sinus involving the muscle graft or nasal pack (five cases), and removal of the muscle graft was necessary in three cases despite the use of appropriate antibiotics.