Genetic relatedness of Streptococcus pneumoniae isolates from paired blood and respiratory specimens.

To assess the relatedness of Streptococcus pneumoniae isolates recovered concurrently from blood and respiratory tract specimens from patients with pneumonia, we analyzed 24 paired isolates by pulsed-field gel electrophoresis (PFGE), serotyping, and antimicrobial susceptibility testing. PFGE, serotype, and/or susceptibility patterns were identical for 22 of 24 pairs. Susceptibility results for blood isolates should guide therapy.

National survey on the susceptibility of Bacteroides fragilis group: report and analysis of trends in the United States from 1997 to 2004.

The susceptibility trends for the species of the Bacteroides fragilis group against various antibiotics from 1997 to 2004 were determined by using data for 5,225 isolates referred by 10 medical centers. The antibiotic test panel included ertapenem, imipenem, meropenem, ampicillin-sulbactam, piperacillin-tazobactam, cefoxitin, clindamycin, moxifloxacin, tigecycline, chloramphenicol, and metronidazole. From 1997 to 2004 there were decreases in the geometric mean (GM) MICs of imipenem, meropenem, piperacillin-tazobactam, and cefoxitin for many of the species within the group. B. distasonis showed the highest rates of resistance to most of the beta-lactams. B. fragilis, B. ovatus, and B. thetaiotaomicron showed significantly higher GM MICs and rates of resistance to clindamycin over time. The rate of resistance to moxifloxacin of B. vulgatus was very high (MIC range for the 8-year study period, 38% to 66%). B. fragilis, B. ovatus, and B. distasonis and other Bacteroides spp. exhibited significant increases in the rates of resistance to moxifloxacin over the 8 years. Resistance rates and GM MICs for tigecycline were low and stable during the 5-year period over which this agent was studied. All isolates were susceptible to chloramphenicol (MICs < 16 microg/ml). In 2002, one isolate resistant to metronidazole (MIC = 64 microg/ml) was noted. These data indicate changes in susceptibility over time; surprisingly, some antimicrobial agents are more active now than they were 5 years ago.

National survey on the susceptibility of Bacteroides Fragilis Group: report and analysis of trends for 1997-2000.

The results of a multicenter US survey using the National Committee for Clinical Laboratory Standards currently recommended methodology for measuring in vitro susceptibility of 2673 isolates of Bacteroides fragilis group species were compared from 1997 to 2000. The test panel consisted of 14 antibiotics: 3 carbapenems, 3 beta-lactam-beta-lactamase inhibitors, 3 cephamycins, 2 fluoroquinolones, clindamycin, chloramphenicol, and metronidazole. Declines in the geometric mean minimum inhibitory concentrations were seen with imipenem, meropenem, ampicillin-sulbactam, and the cephamycins. Increased geometric means were observed with the fluoroquinolones and were usually accompanied by an increase in resistance rates. Bacteroides distasonis shows the highest resistance rates among beta-lactam antibiotics, whereas Bacteroides vulgatus shows the highest resistance levels among fluoroquinolones. B. fragilis shows the lowest resistance rates for all antibiotics. All strains were susceptible to chloramphenicol and metronidazole concentrations <8 microgram/mL. The data underscore the need for species identification and continued surveillance to monitor resistance patterns.

Recurrent Staphylococcus aureus bacteremia: pulsed-field gel electrophoresis findings in 29 patients.

To identify risk factors for relapse among 309 prospectively identified cases of Staphylococcus aureus bacteremia, patients with recurrent S. aureus bacteremia were identified, and pulsed-field gel electrophoresis (PFGE) was performed on isolates from both episodes. PFGE banding patterns from both isolates were identical in 23 patients, consistent with relapsed infection. Patients with PFGE-confirmed relapse were more likely by both univariate and multivariate analyses to have an indwelling foreign body (odds ratio [OR]=18.2, 95% confidence interval [CI]=7. 6-43.6; P<.001), to have received vancomycin therapy (OR=4.1, 95% CI=1.5-11.6; P=.008), or be hemodialysis-dependent (OR=4.1, 95% CI=1. 8-9.3; P=.002) than patients who did not develop recurrent bacteremia. These results suggest that recurrent episodes of S. aureus bacteremia are primarily relapses and are associated with an indwelling foreign body, receiving vancomycin therapy, and hemodialysis dependence.

Infective endocarditis due to Staphylococcus aureus: 59 prospectively identified cases with follow-up.

Fifty-nine consecutive patients with definite Staphylococcus aureus infective endocarditis (IE) by the Duke criteria were prospectively identified at our hospital over a 3-year period. Twenty-seven (45.8%) of the 59 patients had hospital-acquired S. aureus bacteremia. The presumed source of infection was an intravascular device in 50.8% of patients. Transthoracic echocardiography (TTE) revealed evidence of IE in 20 patients (33.9%), whereas transesophageal echocardiography (TEE) revealed evidence of IE in 48 patients (81.4%). The outcome for patients was strongly associated with echocardiographic findings: 13 (68.4%) of 19 patients with vegetations visualized by TTE had an embolic event or died of their infection vs. five (16.7%) of 30 patients whose vegetations were visualized only by TEE (P < .01). Most patients with S. aureus IE developed their infection as a consequence of a nosocomial or intravascular device-related infection. TEE established the diagnosis of S. aureus IE in many instances when TTE was nondiagnostic. Visualization of vegetations by TTE may provide prognostic information for patients with S. aureus IE.

Mycoplasma hominis pneumonia complicating bilateral lung transplantation: case report and review of the literature.

Mycoplasma hominis is a commensal of humans. The organism has been predominantly associated with infections of the genitourinary tract. Extragenital infections have been described in neonates, in women during the postpartum period, and in immunocompromised patients. Pneumonia caused by M. hominis is very rare. This report describes the development of M. hominis pneumonia in a lung transplantation recipient and underscores the difficulty in establishing the correct diagnosis and the need for early and aggressive treatment with appropriate antimicrobial agents to insure a good outcome.

Analysis of trends in antimicrobial resistance patterns among clinical isolates of Bacteroides fragilis group species from 1990 to 1994.

Antimicrobial resistance, including plasmid-mediated resistance, among Bacteroides fragilis group species is well documented. A 5-year (1990-1994) prospective, eight-center survey of 3,177 clinical isolates of Bacteroides species was undertaken to review trends in resistance, using the breakpoints for full and intermediate susceptibility established by the National Committee for Clinical Laboratory Standards. No documented resistance to either metronidazole or chloramphenicol was found in this survey. Among B. fragilis isolates virtually no resistance was seen to imipenem, meropenem, ampicillin/sulbactam, piperacillin/tazobactam, or ticarcillin/clavulanate. Significant increases in resistance among B. fragilis isolates to cefotetan, ceftizoxime, and clindamycin (p < .01) were noted. Resistance to cefoxitin remained unchanged. Among the non-fragilis species of the B. fragilis group, there was virtually no resistance to imipenem, meropenem, chloramphenicol, or metronidazole. The three beta-lactamase inhibitors had increasing levels of resistance, although 95%-98% of strains were susceptible (p < .05). There was a significant decline in cefoxitin, cefmetazole, and clindamycin activity over time against these strains (p <.01). There was a significant (P < .001) increase in geometric mean minimum inhibitory concentration for most drugs and species tested from 1990 to 1994. Clusters in the eight institutions could not account for this rise in resistance. This survey demonstrates that rates of resistance of B. fragilis and non-fragilis species of B. fragilis group are increasing.

Assessment of similarity among coagulase-negative staphylococci from sequential blood cultures of neonates and children by pulsed-field gel electrophoresis.

One of the criteria used to determine the clinical importance of coagulase-negative staphylococci (CoNS) is isolation of the bacteria from sequential blood cultures. Pulsed-field gel electrophoresis was used to characterize sequential blood isolates of CoNS collected within a 7-day period from neonates and children with bacteremia. Of 18 episodes among neonates, 6 (33%) involved unrelated strains of CoNS. All unrelated strains were from neonates who received antimicrobial therapy after the first culture and who had a second culture > or = 36 h later. Among older children, 5 (19%) of the 27 episodes of presumed central venous (CV) catheter-related sepsis involved unrelated isolates. All of the unrelated isolates were from patients who had blood samples obtained through CV catheters only. Thus, even repeated isolation of CoNS from blood cultures may represent contamination if samples are drawn through CV catheters only or if second samples are obtained > 1 day after appropriate antimicrobial therapy.

Contrasting methicillin-resistant Staphylococcus aureus colonization in Veterans Affairs and community nursing homes.

PURPOSE: To compare the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) nares colonization, the patterns of MRSA acquisition, and the risk for subsequent MRSA infection between a hospital-based, Department of Veterans Affairs (VA) nursing home care unit (NHCU) and community-based nursing homes. PATIENTS AND METHODS: In this prospective study, 148 residents of three community nursing homes and 55 residents of a VA NHCU had their anterior nares swabbed; repeat cultures were obtained from hospitalized patients and/or individuals colonized with MRSA. Subjects were followed up prospectively for 1 year to note hospitalizations and the development of MRSA infections. RESULTS: The prevalence of MRSA colonization was significantly higher in the VA NHCU than in the community nursing homes (mean +/- SD 30.3% +/- 11% versus 9.9% +/- 4%). The rate of MRSA nares colonization was similar in the two settings. Acquisition of MRSA took place in both the long-term care facilities and hospitals, with 23.8% of incident cases occurring during a hospitalization. Only 3 of the 27 individuals colonized at baseline developed an MRSA infection. A trend toward an increased rate of infection was seen in colonized individuals residing in the community nursing homes versus those in the VA NHCU (relative risk 4.67; 95% Cl 0.55 to 39.9). Forty-seven percent of the 55 subjects hospitalized were colonized at some point during the study. In contrast to residents of the VA NHCU, MRSA colonization in the community facilities was a marker for high mortality. CONCLUSIONS: Outcomes from colonization may be different in the VA NHCU population and the community nursing home population.

Genetic variability of Bacillus anthracis and related species.

We evaluated the abilities of pulsed-field gel electrophoresis (PFGE) and sequences of intergenic spacer regions (ISRs) between two highly conserved genes, 16S-23S rDNA and gyrB-gyrA ISRs, to detect variation in strains of Bacillus anthracis as well as two closely related species, B. cereus ATCC 14579 and B. mycoides ATCC 6462. For each restriction enzyme, (NotI, SfiI, and SmaI), the PFGE banding patterns for three B. anthracis strains (Ames, Vollum, and Sterne) were identical. However, closely related species could be differentiated from B. anthracis and from each other. PCR amplification of the 16S-23S rDNA ISR yielded a 143- to 144-bp fragment, showing identical sequences for B. anthracis strains, one nucleotide deletion between B. cerus and B. anthracis, and 13 nucleotide differences between B. mycoides and B. anthracis. The gyrase ISR sequences (121 bp) in B. anthracis strains were also identical, but those in B. cereus and B. mycoides differed from that in B. anthracis by 1 and 2 nucleotides, respectively, and from each other by only 1 nucleotide. Given the diverse geographic origins of these B. anthracis strains, this species is very homogenous. We conclude that methods such as PFGE and sequences of ISRs may be useful in separating B. anthracis from closely related species, but more sensitive methods are needed for strain identification of B. anthracis.

Subcultures of BACTEC-positive but gram or acridine orange stain-negative NR 6A and 7A blood culture bottles are unnecessary.

A prospective study was done to assess the comparative use of acridine orange and Gram stains for detecting false-positive BACTEC blood culture bottles, thereby eliminating unnecessary subcultures. A total of 1049 NR 6A and 7A bottles that were instrument-positive in the BACTEC 660 nonradiometric system, but were Gram stain-negative, had aerobic and anaerobic subcultures as well as an acridine orange stain performed. Only five of 1049 (0.5%) instrument-positive, Gram stain-negative bottles grew microorganisms on subculture. Of these five microorganisms, acridine orange stain detected two. All five microorganisms were assessed not to be clinically significant based on review of the patients' charts. Our data showed that the Gram stain and the acridine orange stain are comparable for detecting false-positive NR 6A and 7A bottles. We conclude that subculture of BACTEC-positive, Gram stain-negative NR 6A and 7A bottles is not necessary.

A case-control study of nosocomial ampicillin-resistant enterococcal infection and colonization at a university hospital.

OBJECTIVE: To assess risk factors for colonization and nosocomial infection with ampicillin-resistant enterococci (ARE). DESIGN: Patients with ampicillin-resistant enterococci were compared retrospectively by logistic regression analysis with controls harboring susceptible strains. ARE were characterized by whole plasmid DNA analysis and restriction enzyme analysis of plasmid (REAP) DNA with EcoRI. SETTING: The study was done at a 1,125 bed, tertiary-care teaching hospital in North Carolina with patients from whom enterococci were isolated from June 1, 1989, to March 30, 1991. PATIENTS: The final study group comprised 44 cases with nosocomially-acquired colonization or infection with ARE and 100 controls with ampicillin-susceptible strains. Clinical and epidemiological risk factors for ARE were abstracted by chart review. RESULTS: After controlling for age and site of infection, patients with ARE were more likely to have been admitted previously to our hospital and to have received third-generation cephalosporins and clindamycin. However, only advanced age and clindamycin therapy were independently associated with presence of ARE. REAP with EcoRI showed 20 groups of enterococci on 19 different wards. CONCLUSIONS: These results suggest that ARE are endemic and multifocal in origin in our hospital and that advanced age and use of clindamycin are important selective risk factors for ARE colonization and infection.

The North American component (the United States and Canada) of an International Comparative MIC trial monitoring ofloxacin resistance.

Common lots of reference MIC (minimum inhibitory concentration) method reagents were used to monitor ofloxacin, a newer fluoroquinolone, and 13 other drugs against 3200 recent clinical isolates in February-April 1992. Five medical centers in the United States and Canada contributed 640 strains per facility as follows: Escherichia coli, Staphylococcus aureus, coagulase-negative staphylococci, Klebsiella spp., and Pseudomonas aeruginosa (100 strains each); Streptococcus pneumoniae (40 strains); and Enterobacter cloacae, Serratia marcescens, Salmonella spp., Haemophilus influenzae, and Moraxella catarrhalis (20 strains each). Quality-control strains were processed concurrently, MICs recorded, and data processed at a common location. Selected ofloxacin-resistant isolates were retested at a reference laboratory to confirm resistances and determine cross-resistant patterns. Results indicate the following (a) fluoroquinolones were superior in usable spectrum of activity to other orally administered drugs (for example, cefaclor, cefixime, ampicillin, amoxicillin-clavulanate, minocycline, oxacillin, and trimethoprim-sulfamethoxazole); (b) ofloxacin and ciprofloxacin were generally equal to gentamicin and cefotaxime against commonly isolated Gram-negative pathogens; (c) fluoroquinolone resistance was rare among enteric bacilli, pneumococci (ciprofloxacin > ofloxacin), H. influenzae, and M. catarrhalis, but more common among oxacillin-resistant staphylococci and P. aeruginosa; (d) cross resistance was generally observed between ofloxacin and ciprofloxacin but was species or genus dependent; and (e) a new fluoroquinolone, levofloxacin, demonstrated promising activity against contemporary pathogens.

Controlled evaluation of BACTEC PLUS 27 and Roche Septi-Chek anaerobic blood culture bottles.

Becton Dickinson Diagnostic Instrument Systems (Sparks, Md.) recently introduced BACTEC high-volume aerobic and anaerobic bottles that accept up to 10 ml of blood for use on their nonradiometric blood culture instruments. Both bottles contain 25 ml of tryptic soy broth, 0.05% sodium polyanetholesulfonate, and mixed resins. We compared the anaerobic bottle, designated BACTEC PLUS 27 (BP27), with the Roche Septi-Chek (RSC) Columbia broth anaerobic bottle in a collaborative evaluation at three university hospitals. A total of 5,152 adequately filled blood cultures were obtained from adult patients with suspected bacteremia or fungemia. Staphylococcus aureus was recovered significantly more often (P less than 0.03) from BP27 bottles alone; there were no other significant differences in yield. When microorganisms were recovered from both anaerobic bottles, growth was detected earlier in BP27 than it was in RSC (P less than 0.001), especially for S. aureus (P less than 0.001) and Staphylococcus epidermidis (P less than 0.02). We conclude that the yield from BP27 bottles is equivalent to or better (S. aureus) than that from RSC anaerobic bottles with Columbia broth and that speed of detection is superior with BP27 bottles.

Controlled evaluation of BACTEC Plus 26 and Roche Septi-Chek aerobic blood culture bottles.

Blood culture bottles that accept up to 10 ml of blood have recently been introduced for the BACTEC nonradiometric blood culture system. The new formulation, designated BACTEC Plus, contains 25 ml of tryptic soy broth, 0.05% sodium polyanetholesulfonate, and mixed resins. In a collaborative study conducted at three university hospitals, we evaluated the BACTEC Plus 26 (BP26) aerobic bottle and the Roche Septi-Chek aerobic bottle with its agar slide paddle in 5,293 paired blood cultures. Significantly more microorganisms (P less than 0.001), especially Staphylococcus aureus (P less than 0.001), Staphylococcus epidermidis (P less than 0.01), enterococci (P less than 0.005), and members of the family Enterobacteriaceae (P less than 0.005), were detected by the BP26 bottle. When both bottles detected growth, BP26 did so earlier (P less than 0.001). In particular, S. epidermidis (P less than 0.001), streptococci (P less than 0.005), enterococci (P less than 0.05), and members of the family Enterobacteriaceae (P less than 0.001) were detected earlier by the BP26 bottle. We conclude that the BP26 bottle provides a yield and speed of detection of microorganisms superior to those of the Roche Septi-Chek aerobic blood culture bottle.

Helicobacter pylori-like microorganisms and chronic active gastritis in ferrets.

To determine the prevalence and histology of Helicobacter pylori (HP) associated gastritis in young ferrets, we examined 36 normal 2- to 4-month old ferrets. Identification of HP-like microorganisms included Warthin Starry stains of tissue sections, rapid urease test on fresh tissue, and culture. HP-like microorganisms were found in the stomachs of 35/36 ferrets. The highest density of microorganisms was seen in the antrum, where HP-like microorganisms were present in the pits and in deep glands. HP-like microorganisms were also seen in the cardia and on the foveolar epithelium of the fundus, but not in fundic glands. Chronic active gastritis was seen in all animals with HP-like microorganisms, but involved only the antrum. The distal antrum was most severely involved. One animal had no evidence of HP-like microorganisms on tissue sections or by rapid urease test. Gastric tissue sections from this animal showed only minimal infiltration of the lamina propria by polymorphonuclear leukocytes and lymphocytes. Gastritis associated with HP-like microorganisms is common in ferrets and is acquired at a young age. It is associated with chronic active antral gastritis similar to that seen in humans, suggesting that ferrets should provide a useful experimental model for HP-associated gastritis and peptic ulcer.

Rahnella aquatilis, an unusual gram-negative rod isolated from the bronchial washing of a patient with acquired immunodeficiency syndrome.

Rahnella aquatilis, a rare enteric gram-negative rod which is usually found in fresh water, was isolated from the bronchial washing of a patient with acquired immunodeficiency syndrome. Although few clinical isolates have been reported, this is the second isolation of R. aquatilis from a human in North Carolina. A case report and discussion of R. aquatilis is presented.

Pseudomonas putrefaciens bacteremia.

Pseudomonas putrefaciens is an unusual cause of human disease. Since 1978 only five cases of bacteremia due to this organism have been reported. Within 12 recent months four cases of bacteremia due to P. putrefaciens were seen - two occurred in patients with chronic infections of a lower extremity, one in a patient with neutropenia, and one in a patient with fulminant septicemia and disseminated intravascular coagulation. Two of the patients had prostheses; in neither case did prosthetic infection or prosthetic failure occur. Two syndromes of bacteremic infection with P. putrefaciens are suggested. One syndrome is associated with chronic infection of a lower extremity, is fairly well tolerated, and responds to appropriate antimicrobial agents. The other syndrome is more fulminant and may be associated with severe underlying debility, liver disease, and malignancy. It is not yet known whether this is a meaningful distinction. The significance of the recent increase is the isolation of this organism is not clear at present.