Conference Summaries: ICAAC 2001, IDSA 2001, and ASTMH: Part II
Conference Summaries: ICAAC 2001, IDSA 2001, and ASTMH: Part II
Conference Coverage
Editor’s Note: The following summaries represent a selection of papers from those presented at the meetings listed below. It is important to recognize that many of these summaries are extracted only from the published abstract, and it is possible that some of the material presented at the conferences may have differed. The abstracts can be found online at the URLs given. The 41st Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), Chicago, Ill, Dec. 16-19, 2001; www.icaac.org. The 39th Annual Meeting of the Infectious Diseases Society of America, San Francisco, Calif, Oct. 25-28, 2001; www.idsociety.org. The 50th Annual Meeting of the American Society of Tropical Medicine and Hygiene, Atlanta, Ga, Nov. 11-15, 2001; www.astmh.org. — Stan Deresinski, MD, FACP
STREPTOCOCCUS PYOGENES
Pediatric Onset Neuropsychiatric Disorder (PANDAS), consisting of obsessive compulsive, tic, or anxiety disorders, was associated with evidence of S pyogenes infection and appeared to respond to antibiotic therapy. (ICAAC #1537.)
In a study in Pittsburgh, 48% of Group A Streptococcus pharyngeal isolates in 2001 were resistant to erythromycin; none were resistant to clindamycin, consistent with efflux mediated resistance. (ICAAC #LB-4.) A marked increase in macrolide resistance among S pyogenes strains in Ontario, Canada, was temporarily associated with a similar contemporaneous increase in macrolide prescriptions. (ICAAC #321.)
A Belgian study found significant correlations for S pyogenes isolates with: 1) overall consumption of all macrolide antibiotics and erythromycin resistance; 2) consumption of azithromycin and erythromycin resistance; and 3) consumption of azithromycin and the presence of ermB. It was concluded that the data suggest that long- acting macrolides (presumably meaning azithromycin) exert a stronger selective pressure than others. (ICAAC #1314.)
BRONCHITIS
Acute Bronchitis. Two hundred twenty adults with acute bronchitis were given dextromethorphan and an albuterol inhaler and were also randomized to receive either azithromycin or vitamin C (each given as 500 mg on day one followed by 250 mg daily for 4 additional days). Confirming previous results, antibiotic therapy was not associated with a clinically important difference in outcomes. (ICAAC #905.)
Acute Exacerbation of Chronic Bronchitis. Examination of 527 sputum specimens from 257 patients with acute exacerbation of chronic obstructive pulmonary disease found an "atypical" bacterial pathogen in only 2 specimens—both with C pneumoniae. (ICAAC #906.)
Telithromycin given for 5 days was as effective as comparator agents (amoxicillin/clavulanate and cefuroxime axetil) given for 10 days in the treatment of acute exacerbation of chronic bronchitis in randomized trials. (ICAAC #909.)
COMMUNITY ACQUIRED PNEUMONIA
Diagnosis. In nursing home patients being evaluated for possible pneumonia, an oxygen saturation < 94% (breathing ambient air) by pulse oximetry had a sensitivity of 80%, specificity of 91%, and positive predictive value of 95% for the diagnosis. In a follow-on study, using a decrease from their previous baseline of > 4% saturation as a threshold marker, these values were, respectively, 73%, 100%, and 100%. (IDSA #31.)
Severity Scoring. An analysis of the Pneumonia Severity Index (PSI) as a discriminator of the need for hospitalization in patients with community acquired pneumonia found that only 19 of 78 hospitalizations deemed inappropriate by PSI were, in fact, inappropriate when additional clinical criteria, such as the presence of nausea and vomiting, precluding the use of oral medications were considered. (IDSA #3.)
Antibiotic Therapy. In a retrospective cohort analysis, pre-admission antibiotic therapy did not affect length of stay, time to clinical stability, resource use, or mortality in patients with community acquired pneumonia. (ICAAC #872.)
A meta-analysis of 11 randomized trials published from 1966 through November 2000, involving 3348 patients in which a newer respiratory fluoroquinolone was compared to other commonly used oral antibiotics in the treatment of community acquired pneumonia found, among the evaluable patients, the summary odds ratio favoring fluoroquinolone therapy was 1.43 (95% CI, 1.13-1.80; P = 0.003). However, an analysis of the intention to treat populations (reported in 7 studies) found an odds ratio of only 1.20 (95% CI, 0.99-1.46; P = 0.06). (ICAAC #1853.)
Patients with community acquired pneumonia were randomized to receive either moxifloxacin or comparator therapy with amoxicillin 1 g t.i.d., clarithromycin, or both. The therapies were equally effective, but moxifloxacin was better tolerated. (ICAAC #863.)
Pooled data from randomized trials found that moxifloxacin therapy was effective in 22 of 23 patients infected with M pneumoniae, 13 of 14 with C pneumoniae, and 2 of 2 with L pneumophila. (ICAAC #865.)
Fifteen patients with Legionella pneumonia were treated with oral trovafloxacin, and 13 were given oral gemifloxacin with an overall clinical success rate of 93%. (ICAAC #877.)
A retrospective analysis found that fluoroquinolones (mostly levofloxacin) were as effective as erythromycin in the treatment of 53 patients with Legionella pneumonia, but the time to defervescence and length of hospital stay were shorter in fluoroquinolone recipients. (ICAAC #878.)
In vitro studies found that the rate of resistance mutation in a strain of M pneumoniae was 10-8 to 10-9 for levofloxacin and moxifloxacin and 10-6 to 10-7 for sparfloxacin. While levofloxacin and moxifloxacin appeared to primarily target DNA gyrase, sparfloxacin targets topoisomerase IV in this organism. (ICAAC #144.)
Cefpodoxime and cefditoren were equally effective in a randomized trial in the outpatient treatment of community acquired pneumonia. (ICAAC #852.)
Pooled analysis of 1373 patients with community acquired pneumonia treated with telithromycin in clinical trials found a clinical cure rate of 92.4%. (IDSA #129.) Telithromycin was effective in 100% of 57 patients with pneumococcal pneumonia, including 9 from whom pretreatment isolates were resistant to penicillin and/or erythromycin. (ICAAC #857.) Telithromycin was effective in the treatment of community acquired pneumonia due to C pneumoniae (clinical cure in 32 of 34), M pneumoniae (30 of 31), and L pneumophila (12 of 12). (ICAAC #859.)
Analysis of pooled data from 2 randomized trials found that IV moxifloxacin with switch to p.o. was as safe and effective as comparator agents in the treatment of patients with severe community acquired pneumonia. (IDSA #124.) Six hundred twenty-eight hospitalized patients with community acquired pneumonia were randomized to receive IV/PO moxifloxacin or IV/PO amoxicillin/clavulanate + clarithromycin. Moxifloxacin was superior to the comparator therapy with clinical cure rates of, respectively, 93% and 85% (95% CI for the difference, 2.9-13.2%). (ICAAC #864.)
Ertapenem and ceftriaxone (each 1 g IV q.24h.) were equally effective and safe in the treatment of "serious" community acquired pneumonia in two large multicenter randomized trials. (ICAAC #855, IDSA #456.) Analysis of pooled data from 3 randomized clinical trials found that meropenem was as safe and effective as comparator agents in the treatment of hospitalized patients with community acquired pneumonia. (IDSA #125.)
One hundred seventeen nonimmunocompromised patients with community acquired pneumonia admitted to the ICU were randomized (2:1) to receive levofloxacin 500 mg p.o. b.i.d. or IV ceftriaxone + IV or PO clarithromycin with later switch to oral antibiotics. The success rates were 90% in the p.o. levofloxacin recipients and 89% in the IV ceftriaxone recipients. (ICAAC #870.)
Treatment Failure. Sixty-four of 688 (9.3%) of cases of Gram-negative pneumonia were community acquired; 56% were due to Pseudomonas, 29% to Klebsiella, 8% to Haemophilus, and 6% to others. The 64 were elderly, had high severity scores, many had underlying lung disease, and 42% were admitted from a nursing home; mortality was 22%. Antibiotic resistant organisms caused almost two thirds of infections and initial empiric antibiotic therapy in these was inadequate in 63%, while this was true in only 17% of the remaining cases. (IDSA #485.)
Inadequate antibiotic therapy accounted for only 10 of 68 (15%) treatment failures in patients with community acquired pneumonia given empiric treatment in conformity with IDSA or ATS guidelines. The etiologies of pneumonia in these 10 included MRSA, Pseudomonas and anaerobes in one each, and either a fungus or M tuberculosis in the remainder. Among the 58 patients adequate antibiotic therapy, the most common reasons for clinical failure were sepsis, nonresolving pneumonia, and nosocomial infection. (IDSA #2.)
STREPTOCOCCUS PNEUMONIAE
Epidemiology. A CDC analysis led to estimates of 7200 to 1140 annual deaths in the United States from culture positive invasive pneumococcal disease. (IDSA #875.)
The prevalence of nasopharyngeal colonization with S pneumoniae in infants increased from 7% at age 2 months to 34% at 6 months in infants who did not receive the 7-valent pneumococcal conjugate vaccine; the comparable prevalences for vaccinated infants increased from 8.6% to 27.1%. The majority of isolates from both control and vaccinated children were vaccine-type. (ICAAC #80.)
A logistic regression analysis identified cigarette smoking as the only significant predictor of community acquired pneumonia due to S pneumoniae. (IDSA #878.)
Nasopharyngeal carriage of S pneumoniae was examined in children with nonresponsive acute otitis media treated with gatifloxacin. Although carriage was reduced during therapy, it resumed within days after the end of therapy and exceeded pretreatment levels by 2 to 3 weeks. Recolonization was mostly with new serotypes with decreased penicillin resistance. (ICAAC #1825.)
Vaccination. The state of Alaska recommends pneumococcal vaccination for high-risk persons aged 32 years and all adults older than 55 years of age every 6 years. A retrospective analysis of 180 persons with 3 or more pneumococcal vaccinations, 1 (0.6%) reported a reaction (after third dose) compared with 5 (2.8%) in the comparison group (3 after first dose and 2 after the second dose). Thus revaccination on at least 2 occasions appears safe. (ICAAC #95.)
Concomitant administration of the 7-valent pneumococcal conjugate vaccine did not interfere with the antibody response to Hib-OMP vaccine. (ICAAC #81.) The 7-valent pneumococcal congugate vaccine maintained its immunogenicity when given concomitantly with a 5- component DtaP-IPV-Hib vaccine. (ICAAC #85.)
Diagnosis. The Murex Wellcogen rapid latex agglutination test, when performed on urine samples, was negative in 8 of 8 consecutive patients with culture demonstrated pneumococcal pneumonia. (IDSA #195.)
Antibiotic Resistance. Thirty-five percent of S pneumoniae isolates from 97 US community hospitals were nonsusceptible to penicillin and 32% were resistant to erythromycin. (ICAAC #79.) Penicillin nonsusceptibility in S pneumoniae appears to be decreasing in frequency in Canada. (ICAAC #2102.)
Analysis of 15,481 invasive S pneumoniae isolates in the United States found that the prevalence of macrolide resistance increased from 10.6% in 1995 to 20.4% in 1999. The median MIC of M phenotype isolates, which had increased in prevalence from 7.4% to 16.5%, escalated from 4 to 8 mcg/mL. MLSB phenotype prevalence remained stable at 3-4%. Overall macrolide use increased 13%, but the use of "long-acting macrolide" (presumably meaning azithromycin) had increased 210%. (IDSA #513.) In Canada, the proportion of macrolide resistant S pneumoniae strains with mefA and ermB are approximately equal. (ICAAC #1317.)
Among 86 patients with macrolide-resistant pneumococcal bacteremia, 19 (22%) were receiving a macrolide at the time of their positive blood culture, while none (0%) of 141 matched controls with macrolide susceptible pneumococcal bacteremia were taking a macrolide at that time. Breakthrough bacteremia was seen with strains containing either mef or erm resistance genes. (ICAAC #1850.)
Carriage of an erythromycin-tetracycline resistance conjugative transposon was associated with reduced fitness in some, but not all strains of S pneumoniae. (ICAAC #654.)
Of 2421 isolates of S pneumoniae from across Canada, 6.1% were resistant to ciprofloxacin, 2.1% to levofloxacin, 1.8% to gatifloxacin, and 1% to moxifloxacin. (ICAAC #730.) Ten of 70 (14%) of Hong Kong S pneumoniae year 2000 isolates submitted to the PROTEKT study were fluoroquinolone resistant; all were susceptible to telithromycin, quinupristin/dalfopristin, and linezolid. Nine of the 10 were members of the 23F Spanish clone. (ICAAC #703.)
All 7 patients with pulmonary infection due to levofloxacin-resistant S pneumoniae had significant underlying pulmonary disease, and all had received prior antibiotic therapy (including levofloxacin in 5) for prior pulmonary infection. (ICAAC #902.)
Five hundred twenty-eight levofloxacin-susceptible strains of S pneumoniae from the TRUST4 study in 2000 were examined for fluoroquinolone resistance mutations. None were observed among the 270 isolates whose levofloxacin MIC was 0.5 mcg/mL, while 15 (6%) of those with an MIC of 1 mcg/mL had a ParC alteration and 3 (1.2%) had a ParE change. Ten of 14 (71%) of isolates with a levofloxacin MIC of 2 mcg/mL had a ParC alteration; no ParE changes were detected. None of the 5268 strains had a gyrA alteration. Thus, 3.7% of levofloxacin susceptible pneumococci have a single mutation in the gene encoding topoisomerase IV. (ICAAC #702.)
The mutant prevention concentration (MPC) is defined as the lowest concentration of an antibiotic that prevents the emergence of resistant mutants from an initial inoculum of 1010 bacterial cells. Thus, theoretically, the lower the MPC (relative to clinically achievable serum and tissue concentrations), the less likely the antibiotic is to select out resistant mutants. The MPC90s of 160 isolates of S pneumoniae for gemifloxacin, moxifloxacin, gatifloxacin, and levofloxacin were, respectively, 0.5, 1.0, 2.0, and 8.0 mcg/mL. (ICAAC #732.)
Rabbits with experimental pneumonia caused by strains of S pneumoniae with varying levofloxacin MICS were treated with levofloxacin in a dose designed to mimic a 500 mg b.i.d. dose in humans. In vivo mutations appeared when the AUC/MIC was below 26. A bacteriostatic effect was observed when the AUC/MIC was at least 34 and a 2-log10 CFU reduction was observed with an AUC/MIC of at least 43. Levofloxacin at this high dose was effective when the MIC was < 1.5 mcg/mL, was ineffective when the MIC was > 2.0 mcg/mL, and was associated with emergence of resistance when the MIC was > 1.75 mcg/mL. (ICAAC #2090.)
Pharmacodynamic analysis using an in vitro system found that gatifloxacin suppressed selection of resistant mutants of S pneumoniae with an MIC of 0.25 mcg/mL at inocula of both 106 and 108 at an AUC/MIC of > 50, a clinically achievable ratio. For a second pneumococcal isolate with an MIC of 1 mcg/mL, however, AUC/MIC ratios of 200 and 500 were required. (ICAAC #445.)
Treatment. Retrospective analysis of 65 patients with community acquired pneumonia due to penicillin nonsusceptible S pneumoniae found that the cure rate was 80% in those treated with levofloxacin, 50% in those treated with a cephalosporin, 38% in those given a cephalosporin plus a macrolide, 36% in those treated with penicillin, and 13% of those given a macrolide alone. (ICAAC #2062.)
Four of 4 pediatric patients with nonmeningeal invasive pneumococcal infection with bacteremia due to a cefotaxime-resistant strain with an MIC = 1 mcg/mL were successfully treated with cefotaxime. Six adult patients with pneumonia caused by similar strains were also treated with cefotaxime; 2 died of infection—one after a single dose and one on day 8 of therapy. (ICAAC #901.)
The mortality rate among 13 patients with invasive nonmeningeal pneumococcal infection "resistant" to ceftriaxone (MIC = 2 mcg/mL) who were treated with that antibiotic was 15%. (ICAAC #903.)
HAEMOPHILUS INFLUENZAE
The prevalence of H influenzae isolates with reduced susceptibility to ciprofloxacin (MIC > 0.12 mcg/mL) increased from < 0.1% of isolates in previous years to 0.1-15% in 2000. Single mutations in gyrA or parC increased the ciprofloxacin MIC to 0.12-4 mcg/mL, while the presence of mutations in both was associated with MICS > 16 mcg/mL. (ICAAC #LB-3.)
PERTUSSIS
Thirty-two percent of adults with a cough lasting more than 7 days (mean duration, 20 days) had evidence of pertussis. (ICAAC #1542.) The diagnosis of pertussis is, however, often problematic. In one large experience, outbreaks of cough illness were associated with apparently falsely positive PCR tests for B pertussis, resulting in resource misallocation. (IDSA #104.)
Revaccination, using the acellular pertussis vaccine, may prove to be a valuable tool in reducing the incidence of pertussis in adults. In a large national randomized trial, administration of acellular pertussis vaccine to adults and adolescents was associated with a protective efficacy of 77% (95% CI, 9-98%; P = 0.07). (ICAAC #1291.)
DIPTHERIA
An invasive clone of nontoxigenic C diphtheriae caused bacteremia in a number of the Vancouver, Canada, downtown homeless population. (ICAAC #2282.)
An outbreak of diphtheria occurred in a group of military trainees in Latvia despite a high level of prior vaccination. (ICAAC #2283.)
SKIN AND SKIN STRUCTURE INFECTIONS
Necrotizing Fasciitis. Two patients with necrotizing fasciitis after intramuscular administration of medication were described. The authors suggest that MRI be performed to evaluate patients with pain out of proportion to clinical findings at an IM injections site. (IDSA #178.)
A cluster of cases of necrotizing fasciitis due to C sordelli occurred among black tar heroin users in Ventura County, California. (IDSA #110.) A patient with rheumatoid arthritis receiving etanercept developed necrotizing fasciitis due to S pneumoniae. (IDSA #137.)
Treatment. Ertapenem 1 g q.24h. and piperacillin/tazobactam 3.375 q q.6h. were equally effective in the treatment of complicated skin and skin structure infections in a randomized trial. (ICAAC #1483, IDSA #111.)
STAPHYLOCOCCUS
Colonization. There was a high degree of concordance in S aureus nasal carriage among household partners in an elderly population. (ICAAC #1216.) Persistent carriage was not a risk factor for mortality. (ICAAC #1217.)
Prospective screening found that 107 of 208 (51%) ICU and liver transplant patients were never colonized with S aureus, 21% were nasal carriers alone, 3% were rectal carriers only, and 24% had both nasal and rectal carriage. S aureus infection occurred in 3.7% of the noncarriers, 18.2% of those with only nasal carriage, none of the 7 with only rectal carriage, and in 40% of those with both nasal and rectal carriage. Rectal carriage (with or without nasal carriage), APACHE II score, and length-of-hospital stay were independent predictors of S aureus infection. (ICAAC #2054.)
MRSA. Three dogs and a horse, the owners of each of which had had recent contact with health care facilities, had MRSA infections with strains indistinguishable from the major clones affecting humans in Ontario, Canada. (ICAAC #307.)
An outbreak of community acquired MRSA in Alaska natives was associated with prior receipt of antibiotic therapy and with sauna use. (IDSA #16.) Sixteen of 1761 (0.9%) residents of 12 Alaska native villages had nasal colonization with MRSA, with clustering in 4 of the villages and with 94% of carriers residing in villages were steam bathing is common. MRSA carriage was associated with an increased risk of infectious skin diseases. (ICAAC #310.)
Two genotypes accounted for 78% of 97 MRSA isolates recovered from outpatients attending a Wound Clinic in San Francisco, suggesting epidemiological association between many cases. (ICAAC #306.)
S aureus, E coli, and coagulase-negative staphylococci together accounted for 55% of 28,468 SENTRY Program bacterial blood stream isolates obtained during the 4 years ending December 31, 2000. The proportion due to S aureus increased from 22.9% to 27.9% and the proportion that were oxacillin-resistant increased from 21.8% to 33.2%. (ICAAC #78.) Thirty-nine percent of S aureus blood stream isolates from 97 US community hospitals were methicillin resistant. (ICAAC #79.)
A retrospective analysis found no difference in mortality in patients with MSSA or MRSA bacteremia and, among the 104 patients with MRSA, initial treatment with ineffective antibiotics did not significantly adversely affect outcome. (ICAAC #UL04.) In contrast, a prospective cohort study found that compared to MSSA, MRSA surgical site infection was associated with greater mortality, hospital charges, and number of hospital days after infection. (ICAAC #2056.) A retrospective cohort analysis found that MRSA bacteremia was associated with a significantly greater length of stay and costs when compared to MSSA bacteremia. (ICAAC #1221.)
A health care worker found to be colonized with MRSA during a hospital outbreak of infection with this organism and for whom repeated efforts of decolonization failed, was subsequently successfully colonized with MSSA. Replacement of the MRSA was associated with no further relapse of MRSA-related hospitalization. (ICAAC #2057.)
The most important risk factor for the development of MRSA bacteremia in a trauma center was having received > 48 hours of antibiotic therapy with activity against MSSA within the previous 30 days. (ICAAC #1220.) Prior levofloxacin use was among the factors associated with MRSA infection at one hospital. In vitro studies found that fluoroquinolone exposure increased the proportion of colonies of MRSA that grew on agar containing 128 mcg/mL oxacillin; levofloxacin and ciprofloxacin were more potent in this regard than were gatifloxacin and moxifloxacin. (ICAAC #1224.)
Moxifloxacin and doxycycline were synergistic in vitro against 3 strains of MRSA. (IDSA #578.) Linezolid therapy failed to clear bacteremia in 2 patients with endocarditis due to MRSA. (IDSA #533.)
Glycopeptide Resistance. A case-control study involving 15 cases of infection with VISA or "SARV" (S aureus with reduced susceptibility to vancomycin) reported to the CDC found that they were associated with high mortality and that the major risk factor for such infections was prolonged vancomycin use. (ICAAC #1230.)
Of 79 MRSA bloodstream isolates from 65 patients at one northeastern US hospital, 24 (30%) exhibited heterogeneously increased resistance to vancomycin. The presence of such strains did not appear to affect patient outcomes. (ICAAC #319.)
A survey of 242 strains of S aureus (36% MRSA) isolated at 105 French hospitals in 1 month found that 7 strains were heterogeneously resistant to teicoplanin but susceptible to vancomycin. Four of 12 MRSA clones prevalent in French hospitals had intermediate susceptibility to glycopeptides (GISA strains) and these were isolated in 7 hospitals from geographically distinct areas. (ICAAC #315.) A separate survey of 63 French hospitals identified GISA in 27 (29%). (ICAAC #317.) Sixty-eight of 400 (17%) strains of S aureus at 1 Spanish hospital grew in the presence of 4 mcg/mL of vancomycin and 2 (0.5% of the total strains) of these were heterogeneous GISA strains. (ICAAC #2059.)
In vitro studies found that linezolid is bacteriostatic against VISA. Against gentamicin susceptible strains, lenzolid antagonized the aminoglycoside’s bactericidal activity. The combination of linezolid and vancomycin was indifferent against VISA. (ICAAC #1418.)
Triclosan has reduced activity against some GISA strains. (ICAAC #2268.)
BLOODSTREAM INFECTION AND ENDOCARDITIS
Predictors of complications in 724 with S aureus bacteremia adults present at initial evaluation were the presence of clinically evident emboli, hematuria, anemia, a diastolic or new murmur, abnormal skin exam, prolonged symptom duration, the presence of an orthopedic prosthesis, and admission to a surgical service. Hospital-or health care-associated bacteremia was less likely to be complicated than was community acquired bacteremia. Additional risk factors, when variables present at days 2-4 were included in the model, were blood culture positivity at days 2-4, failure to remove an infected source, increasing number of positive blood cultures, and persistent fever at 72 hours. (ICAAC #1218.)
With a median follow-up of 605 days after the occurrence of bloodstream infection (total, 149), 2 of 192 (1%) prosthetic joints in 133 patients became infected. The pathogen in both cases was S aureus, with diagnosis of joint infection 1182 and 1726 days after bloodstream infection. The overall 5-year probability of late prosthetic joint infection after all bloodstream infection was 1.85%, while that after S aureus bacteremia was 16.7%. (IDSA #236.)
In a 6-hospital study of 505 patients with S aureus bacteremia, 64 (13%) had endocarditis, including 7 patients who developed endocarditis after the onset of bacteremia. Two of 12 (7%) patients with a prosthetic cardiac valve developed endocarditis after bacteremia. Risk factors for endocarditis included the presence of valvular heart disease, injection drug use, community acquisition of infection, unknown portal of entry, and being nonwhite. Because persistently positive blood cultures despite 3 days of antibiotic therapy was also a risk factor, the investigators recommend obtaining follow-up cultures on all patients at that time, regardless of echocardiographic findings, and that those with positive results may require "more potent antibiotic therapy." (ICAAC #1341.)
Of 111 patients with nosocomial S aureus bacteremia, 56 (50%) were documented to be IV catheter-related, 38% had a source of infection other than an IV catheter, and 12% had primary bacteremia. The frequency with which endocarditis was diagnosed in these groups was, respectively, 5.4% (3/56), 10% (4/42), and 15% (2/13). Endocarditis was diagnosed during the acute episode in all 5 who had catheter-related or primary bacteremia, 2 as the result of persistent fever and 3 because of metastatic foci. Of 45 survivors with initially uncomplicated catheter-related and primary bacteremia, all treated for 10-14 days and who were followed for at least 12 months, none developed evidence of endocarditis. (ICAAC #1429.)
Two hundred twenty-two patients with IV catheter-related staphylococcal bacteremia were randomized to treatment with either quinupristin/dalfopristin, nafcillin or vancomycin. A complete clinical response was achieved in 53% of streptogramin recipients and 64% of recipients of comparator therapy (P = 0.2). Adverse events occurred more frequently in the quinupristin/dalfopristin-treated patients (13.3% vs 4.6%; P = 0.02). (IDSA #15.)
Eradication of the focus of infection in patients with S aureus bacteremia was associated with reduced mortality. (ICAAC #1484.)
A case-control study found that a delay in initiation of appropriate antibiotic therapy in trauma patients with S aureus bacteremia was associated with a longer duration of bacteremia (4 vs 3 days), leukocytosis (16 vs 6 days), and hospitalization (32 vs 20 days). (ICAAC #396.) A retrospective study found evidence of a reduced risk of complications from IV catheter-related S aureus bacteremia if the treatment duration was at least 14 days. (IDSA #81.)
Prosthetic Joint Infection. Rifampin with either ciprofloxacin or ofloxacin were synergistic in an animal model of prosthetic joint infection due to MSSA. (ICAAC #1146.) High-level resistance to rifampin is associated with reduced replicative fitness in S aureus. (ICAAC #653.)
Fifteen patients with hip arthroplasty infections due to staphylococci susceptible to rifampin underwent open debridement and were treated with rifampin plus either levofloxacin (12 patients) or clindamycin (3 patients) for 3 months. All but 2 of the infections occurred within 2 months of arthroplasty. Only 1 patient (who had a late infection) failed therapy. (ICAAC #1460.)
Pneumonia. Six hundred twenty-three patients with ventilator-associated pneumonia were randomized to receive either linezolid or vancomycin, each with optional aztreonam; cure rates in the 2 arms were similar. For patients with S aureus isolated at baseline, cure rates were 53.8% for linezolid and 43.5% for vancomycin (P = NS). (ICAAC #1469.)
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