An in vitro study of adherence of coagulase-negative staphylococci to bone chip columns.

Coagulase-negative staphylococci (CNS) have become a dominant cause of bone infections and their adherence to the infected bones is a prerequisite for the initiation of these infections. In the present study we investigated and compared the adherence of CNS bacteria to human, chicken and rabbit bones. The study was performed using columns made of bone powder from the three different sources, and measurement of the extent of adhesion to bones of CNS bacteria as an in vitro model which is based on particles of matrix that are closely related to the natural matrix. The adhesion to rabbit bone was relatively high, while adhesion to both human and chicken bone columns was lower and almost identical. Pretreatment of the CNS bacteria with sodium periodate, beta-galactosidase or proteinase K significantly inhibited by 50-60% the adhesion to human bones. Pretreatment of CNS bacteria with subinhibitory concentrations of vancomycin or tunicamycin increased their adherence to human bones several-fold. When the bones were pretreated with vancomycin a considerable increase in the adhesion rate of the bacteria to human and chicken bones was seen. A smaller increase in adherence was observed after pretreatment of human bones with the antibiotic tunicamycin. Salicylic acid or benzalkonium chloride (BZC) also resulted in an increase in adhesion to these pretreated bones. From the results obtained it seems that pretreatment of the CNS bacteria with certain reagents exposes adhesins on the surface of the CNS bacteria. On the other hand, pretreatment of the bones with other reagents may enable a better exposure of receptors located on the bone cells and, as a consequence, may improve the adhesion of the CNS bacteria to the treated bones.

Serious consequences to the use of cephalosporins as the first line of antimicrobial therapy administered in hemodialysis units.

BACKGROUND: The dramatic spread of vancomycin-resistant enterococci (VRE) among hemodialysis (HD) patients led to the replacement of vancomycin with cephalosporins as part of the primary empiric therapy for bacterial infections in HD units. The aim of the study was to examine the effects of this new regimen on the colonization rate of resistant bacteria among HD patients. METHODS: Rectal swabs were taken from 105 HD patients and 91 control hospitalized patients. Groups were matched for age, sex, nursing home residency and background diseases. Enterococci were tested for vancomycin resistance, Staphylococcus aureus isolates were tested for methicillin resistance (MRSA), and Enterobacteriaceae were tested for extended-spectrum beta-lactamase (ESBL) activity. RESULTS: In the HD group 1 VRE, 1 MRSA and 9 ESBL-producing organisms were isolated compared to 1 MRSA and 1 ESBL organism in the control group (p = 0.018 for ESBL). In the year prior to the study, the use of cephalosporins had been enhanced in the HD group compared to the control group (p < 0.001), and in the HD ESBL-positive patients compared to the HD ESBL-negative ones (p = 0.007). The overall use of antibiotics in the control group was the same as in the HD group. In a subanalysis of the HD group alone, the ESBL carriers were older, sicker, used more antibiotics, were hospitalized frequently and had a higher mortality rate, compared to noncarriers. CONCLUSIONS: The use of cephalosporins as first-line therapy in HD patients in central Israel reduced the prevalence of VRE colonization but may have contributed to the emergence of ESBL-producing organisms through induction of selection pressure. This may lead to serious complications in the management of these patients.

Salmonellosis: an epidemiologic study.

BACKGROUND: Salmonella species commonly produce acute gastroenteritis. The clinical course may be affected by factors such as age, immunosuppression, and underlying disorders. OBJECTIVES: To investigate clinical and laboratory differences in the infected population and the risk of complications according to the different age groups. METHODS: The records of 295 patients with positive cultures for Salmonella were divided into six age groups and reviewed retrospectively for the years 1994-1997. Demographic, clinical and laboratory data, extraintestinal manifestations, underlying disorders, organism source, and susceptibilty to antibiotics were analyzed. RESULTS: We found that 88.5% were only stool positive, 9.2% had positive blood cultures, and 2.4% were positive in both blood and stool; 3.6% were found to have underlying disorders. Anemia, disturbed liver function tests and hypoalbuminemia were the most common pathologic laboratory findings. Salmonella serogroups B and D were isolated most frequently. The rate of positive blood cultures increased significantly during the years, as did resistance to ampicillin and trimethoprimsulfamethoxazole. Salmonella infection has two peaks of incidence: at ages 1-5 and 15-65 years. Bacteremia was prominent in the extreme ages. CONCLUSIONS: Salmonella infection has a different clinical presentation in different age groups. The significant increase in the rate of bacteremia in the extreme age groups necessitates a different attitude and management for these heterogeneous patient populations.

Murine typhus among Arabs and Jews in Israel 1991--2001.

The aim of this study was to explore the incidence and differences in the epidemiology of murine typhus between Jews and Arabs in Israel. Between 1991 and 2001, 406 cases of murine typhus were diagnosed; 57% of cases occurred between August and November. Differences between Arabs vs. Jews regarding mean yearly incidence (1.84 vs. 0.35/100,000 people; p = 0.003), median age (35 vs. 44 years; p < 0.001), and male:female ratio (1:1 vs. 1.3:1; p = 0.009), were found. Control measures to decrease morbidity of murine typhus should take into consideration the socio-economic and environmental factors influencing the differences observed.

Infectious aetiologies in elderly patients hospitalised with non-pneumonic lower respiratory tract infection.

OBJECTIVE: to identify the infectious aetiologies of non-pneumonic lower respiratory tract infections in hospitalised elderly patients, and to characterise the patients in terms of demographic, clinical and therapeutic variables. DESIGN: a prospective, non-interventional, purely serologically based diagnostic study. SETTING: a tertiary university hospital in southern Israel. SUBJECTS: 133 elderly patients hospitalised for non-pneumonic lower respiratory tract infections. METHODS: paired sera were obtained for each of the hospitalisations and were tested using immunofluorescence or enzyme immunoassay methods to identify 13 different pathogens. Only significant changes in antibody titers or levels between the paired sera were considered diagnostic. RESULTS: at least one infectious aetiology was identified in 77 patients (58%). At least one of seven viral aetiologies was identified in 52 patients (39%). A bacterial aetiology was identified in 27 patients (20%) including Streptococcus pneumoniae in 24 (18%). An atypical bacterium was found in 27 patients (20%) including Mycoplasma pneumoniae in 15 (11%) and Legionella spp. in nine (7%). More than one aetiology was found in 23 patients (17%). One hundred and twenty nine patients (96%) suffered from serious chronic co-morbidity. One hundred and twenty one patients received antibiotics during their hospitalisation, 106 (80%) with a beta-lactam and 42 (31%) with another antibiotic. CONCLUSIONS: non-pneumonic lower respiratory tract infection is caused in hospitalised elderly patients by a broad spectrum of aetiological agents, primarily respiratory viruses with a significant, though lesser, prevalence of classical and atypical bacteria. Despite this distribution of aetiologies, most patients are treated with beta-lactam antibiotics. The indication for antibiotic therapy in these patients and the choice of antibiotic preparation should be addressed in further studies.

Atypical pathogen infection in adults with acute exacerbation of bronchial asthma.

In a serologically based prospective study, acute infections with four atypical pathogens were determined in 100 adults hospitalized for acute exacerbation of bronchial asthma, and compared with the corresponding rate in a matched control group. Paired sera were tested using immunofluorescence or enzyme immunoassay methods to establish the serologic diagnosis. In 18 patients (18%), there was evidence of acute infection with Mycoplasma pneumoniae, compared with 3% in the control group (p = 0.0006). In 10 of these patients there was evidence of infection with at least one additional pathogen, a respiratory virus in 7. There was no significant difference between the study groups in the rates of acute infection by Chlamydia pneumoniae (8% in the hospitalized patients versus 6% in the control subjects), Legionella spp. (5 versus 3%, respectively), or Coxiella burnettii (no patients in either group). We conclude that of these four atypical pathogens, only infection with M. pneumoniae is associated with hospitalization for acute exacerbation of bronchial asthma. In most of these M. pneumoniae patients there is evidence of infection with a respiratory virus as well. The pathophysiologic and therapeutic significance of these findings should be tested in further studies specifically designed to address these questions.

Legionella species infection in adult febrile respiratory tract infections in the community.

Legionella spp. (Lsp) are well recognized as etiologic factors in pneumonia but less so in respiratory tract infections (RTI) in the community. The objective of the present study was to characterize febrile RTI patients with a documented Legionella etiology, in terms of specific serogroups, clinical manifestations of the disease, disease course and the effect of antibiotic therapy. Ambulatory adults with febrile RTI (n = 250) were included in a prospective study in which the etiological causes of the infection were identified using sophisticated serological techniques. Paired sera were obtained for each of the patients and were tested for 41 different serotypes of Lsp using micro-immuno-fluorescence (MIF) serology. Only a significant change in IgG and/or IgM antibody titers was considered diagnostic. In 28 patients (11.2%) there was serological evidence of acute infection with 1 of the types of Lsp. The infections were manifested clinically as upper RTI in 9 patients and as lower RTI in the other 19 patients (community-acquired pneumonia in 2 of these). L. pneumophila serogroup 1 was identified in 3 patients, L. pneumophila serogroups higher than 1 were identified in 13 patients and L. non-pneumophila serogroups in 18 patients. The clinical and laboratory findings in patients with acute Lsp infection were not significantly different from those in patients without evidence of this infectious agent. The length and course of the disease were similar in the 12 patients treated with specific antibiotics for Lsp and in those who were not. We conclude that Lsp can be identified in a significant percentage of patients with acute febrile RTI. No specific clinical or laboratory features were observed for these patients and specific antibiotic therapy does not affect the course of the disease.

Colonization rate of bacteria in the throat of healthy infants.

OBJECTIVE: the human throat is a major ecological site for various bacteria that can reach neighbouring sterile sites and cause mild infections or invasive diseases. The aim of this study was to investigate the carriage rate of several potential pathogens in the throat of healthy children under the age of 2 years. METHODS: cultures were taken from the tonsils of 1000 healthy infants aged 1-24 months attending well-baby clinics, who had not received antibiotic therapy during the preceding 14 days. RESULTS: one hundred and ninety-eight (19.8%) cultures were positive. Thirteen (1.3%) cultures were positive for beta-haemolytic Streptococcus group A, 23 (2.3%) for Streptococcus pneumoniae. In 28 (2.8%) and 24 (2.4%) cultures, respectively, Haemophilus influenzae Type b and non-typeable Haemophilus influenzae were recovered. The commonest bacterium found was Staphylococcus aureus (99 positive cultures). Eleven children carried two species of bacteria and from one 6-month-old child three species were isolated concurrently. CONCLUSIONS: it is concluded that children younger than 2 years of age can be carriers of several types of pathogenic bacteria. In contrast to many other studies, in this study beta-haemolytic Streptococcus group A was isolated from the tonsils of children younger than 1 year of age.

A comparative study of the etiology of adult upper and lower respiratory tract infections in the community.

Lower respiratory tract infection and upper respiratory tract infection (URTI) are very common, but the etiology is not diagnosed in routine practice. The objective of this study was to determine and compare the frequency distribution of the various infectious etiologies for these diseases. One hundred seventy five adults in the community with febrile LRTI and 75 with febrile URTI were included in a purely serologically based prospective study. Paired sera were obtained for each of the patients and were tested by EIA or immunofluorescence methods to identify 14 different pathogens. Only a significant change in antibody titers between the paired sera was considered diagnostic. At least one infectious etiology was identified in 167 patients (67%). In the LRTI group, infection with at least one of 7 respiratory viruses was found in 88 patients (50%). One of the atypical pathogens was found in 40 patients (23%), of these Legionella spp. in 19 (11%) and Mycoplasma pneumoniae in 18 (10%). A bacterial etiology was found in 19 patients (11%), of these Streptococcus pneumoniae in 8 (5%) and beta-hemolytic streptococci group A in 5 (3%). The frequency distribution of etiologies in the URTI group was not significantly different from the LRTI group, except for M. pneumoniae that was identified in only one patient with URTI (p = 0.015). More than one etiologic agent was found in 42 (17%) of the patients. LRTI is caused by a broad spectrum of etiologies, with respiratory viruses predominating and a moderate, but significant, prevalence of atypical pathogens. The frequency distribution of etiologies for URTI is similar to LRTI. In a significant proportion of patients with URTI and LRTI there is serologic evidence of infection with more than one pathogen. The justification and benefit of distinguishing between URTI and LRTI in routine clinical work is doubtful. When a decision is reached to treat RTI patients with an antibiotic, it is logical to use a macrolide or tetracycline.