Clostridium difficile strains from community-associated infections.

Clostridium difficile isolates from presumed community-associated infections (n = 92) were characterized by toxinotyping, pulsed-field gel electrophoresis, tcdC and cdtB PCR, and antimicrobial susceptibility. Nine toxinotypes (TOX) and 31 PFGE patterns were identified. TOX 0 (48, 52%), TOX III (18, 20%), and TOX V (9, 10%) were the most common; three isolates were nontoxigenic.

Clostridium difficile in retail meat products, USA, 2007.

To determine the presence of Clostridium difficile, we sampled cooked and uncooked meat products sold in Tucson, Arizona. Forty-two percent contained toxigenic C. difficile strains (either ribotype 078/toxinotype V [73%] or 027/toxinotype III [NAP1 or NAP1-related; 27%]). These findings indicate that food products may play a role in interspecies C. difficile transmission.

Toxinotype V Clostridium difficile in humans and food animals.

Clostridium difficile is a recognized pathogen in neonatal pigs and may contribute to enteritis in calves. Toxinotype V strains have been rare causes of human C. difficile-associated disease (CDAD). We examined toxinotype V in human disease, the genetic relationship of animal and human toxinotype V strains, and in vitro toxin production of these strains. From 2001 through 2006, 8 (1.3%) of 620 patient isolates were identified as toxinotype V; before 2001, 7 (<0.02%) of approximately 6,000 isolates were identified as toxinotype V. Six (46.2%) of 13 case-patients for whom information was available had community-associated CDAD. Molecular characterization showed a high degree of similarity between human and animal toxinotype V isolates; all contained a 39-bp tcdC deletion and most produced binary toxin. Further study is needed to understand the epidemiology of CDAD caused by toxinotype V C. difficile, including the potential of foodborne transmission to humans.

Clostridium difficile-associated diarrhea: an emerging threat to pregnant women.

OBJECTIVE: To estimate if Clostridium difficile-associated disease (CDAD) is increasing in peripartum women. STUDY DESIGN: Peripartum CDAD was assessed through 1) passive surveillance collecting clinical and pathology data on severe cases and 2) survey among infectious disease consultants (ICDs) in the Emerging Infections Network. RESULTS: Ten severe cases were collected; most had associated antibiotic use. Seven women were either admitted to the ICU or underwent colectomy. Three infants were stillborn, and 3 women died. The epidemic Clostridium difficile strain was found in 2 cases. Among 798 ICDs, 419 (52%) participated in the survey. Thirty-seven respondents (9%) recalled 55 cases, mostly in the postpartum period with 21 complications, mainly due to relapse. CONCLUSION: Severe CDAD may be increasing in peripartum women. Clinicians should have a low threshold for testing, be aware of the potential for severe outcomes, and take steps to reduce both the risk of disease and resultant complications.

Severe community-acquired pneumonia due to Staphylococcus aureus, 2003-04 influenza season.

During the 2003-04 influenza season, 17 cases of Staphylococcus aureus community-acquired pneumonia (CAP) were reported from 9 states; 15 (88%) were associated with methicillin-resistant S. aureus (MRSA). The median age of patients was 21 years; 5 (29%) had underlying diseases, and 4 (24%) had risk factors for MRSA. Twelve (71%) had laboratory evidence of influenza virus infection. All but 1 patient, who died on arrival, were hospitalized. Death occurred in 5 (4 with MRSA). S. aureus isolates were available from 13 (76%) patients (11 MRSA). Toxin genes were detected in all isolates; 11 (85%) had only genes for Panton-Valentine leukocidin. All isolates had community-associated pulsed-field gel electrophoresis patterns; all MRSA isolates had the staphylococcal cassette chromosome mec type IVa. In communities with a high prevalence of MRSA, empiric therapy of severe CAP during periods of high influenza activity should include consideration for MRSA.

An epidemic, toxin gene-variant strain of Clostridium difficile.

BACKGROUND: Recent reports suggest that the rate and severity of Clostridium difficile-associated disease in the United States are increasing and that the increase may be associated with the emergence of a new strain of C. difficile with increased virulence, resistance, or both. METHODS: A total of 187 C. difficile isolates were collected from eight health care facilities in six states (Georgia, Illinois, Maine, New Jersey, Oregon, and Pennsylvania) in which outbreaks of C. difficile-associated disease had occurred between 2000 and 2003. The isolates were characterized by restriction-endonuclease analysis (REA), pulsed-field gel electrophoresis (PFGE), and toxinotyping, and the results were compared with those from a database of more than 6000 isolates obtained before 2001. The polymerase chain reaction was used to detect the recently described binary toxin CDT and a deletion in the pathogenicity locus gene, tcdC, that might result in increased production of toxins A and B. RESULTS: Isolates that belonged to one REA group (BI) and had the same PFGE type (NAP1) were identified in specimens collected from patients at all eight facilities and accounted for at least half of the isolates from five facilities. REA group BI, which was first identified in 1984, was uncommon among isolates from the historic database (14 cases). Both historic and current (obtained since 2001) BI/NAP1 isolates were of toxinotype III, were positive for the binary toxin CDT, and contained an 18-bp tcdC deletion. Resistance to gatifloxacin and moxifloxacin was more common in current BI/NAP1 isolates than in non-BI/NAP1 isolates (100 percent vs. 42 percent, P<0.001), whereas the rate of resistance to clindamycin was the same in the two groups (79 percent). All of the current but none of the historic BI/NAP1 isolates were resistant to gatifloxacin and moxifloxacin (P<0.001). CONCLUSIONS: A previously uncommon strain of C. difficile with variations in toxin genes has become more resistant to fluoroquinolones and has emerged as a cause of geographically dispersed outbreaks of C. difficile-associated disease.

Antimicrobial susceptibility testing of Acinetobacter spp. by NCCLS broth microdilution and disk diffusion methods.

Although both broth microdilution (BMD) and disk diffusion (DD) are listed by NCCLS as acceptable methods for testing Acinetobacter spp. for antimicrobial susceptibility, few studies have compared the results generated by the two methods. We tested 196 isolates of Acinetobacter spp. from nine U.S. hospitals and from the Centers for Disease Control culture collection by using BMD and DD and clinically appropriate antimicrobial agents. Categorical results for amikacin, ciprofloxacin, gatifloxacin, gentamicin, imipenem, levofloxacin, meropenem, tobramycin, and trimethoprim-sulfamethoxazole were comparable for the two methods: there was only one very major (VM) error, with tobramycin, and only one major (M) error, with meropenem, when DD results were compared with BMD results. However, VM errors were frequent with the beta-lactams and beta-lactam-beta-lactam inhibitor combinations, while M errors were often observed with tetracyclines. For BMD, tests frequently exhibited subtle growth patterns that were difficult to interpret, especially for beta-lactams. If subtle growth (i.e., granular, small button, or "starry" growth) was considered positive, error rates between BMD and DD were unacceptably high for ampicillin-sulbactam (VM error, 9.8%; minor [m] error, 16.1%), piperacillin (VM error, 5.7%; m error, 13.5%), piperacillin-tazobactam (VM error, 9.3%; m error, 12.9%), ceftazidime (VM error, 6.2%; m error, 11.4%), cefepime (VM error, 6.2%; m error, 13.0%), cefotaxime (m error, 21.2%), ceftriaxone (m error, 23.3%), tetracycline (M error, 11.4%; m error, 32.1%), and doxycycline (M error, 2.6%). When subtle growth patterns were ignored, the agreement still did not achieve acceptable levels. To determine if the problems with BMD testing occurred in other laboratories, we sent frozen BMD panels containing beta-lactam drugs and nine isolates to six labs with experience in performing BMD and DD. Among these laboratories, cefepime MICs ranged from < or =8 to > or =32 microg/ml for four of the nine strains, confirming the problem in interpreting BMD results. Discrepancies between the categorical interpretations of BMD and DD tests were noted primarily with cefepime and piperacillin, for which the BMD results were typically more resistant. Clinical laboratories should be aware of these discrepancies. At present, there are no data to indicate which method provides more clinically relevant information.

Genetic analysis of a high-level vancomycin-resistant isolate of Staphylococcus aureus.

Vancomycin is usually reserved for treatment of serious infections, including those caused by multidrug-resistant Staphylococcus aureus. A clinical isolate of S. aureus with high-level resistance to vancomycin (minimal inhibitory concentration = 1024 microg/ml) was isolated in June 2002. This isolate harbored a 57.9-kilobase multiresistance conjugative plasmid within which Tn1546 (vanA) was integrated. Additional elements on the plasmid encoded resistance to trimethoprim (dfrA), beta-lactams (blaZ), aminoglycosides (aacA-aphD), and disinfectants (qacC). Genetic analyses suggest that the long-anticipated transfer of vancomycin resistance to a methicillin-resistant S. aureus occurred in vivo by interspecies transfer of Tn1546 from a co-isolate of Enterococcus faecalis.

Pulsed-field gel electrophoresis typing of oxacillin-resistant Staphylococcus aureus isolates from the United States: establishing a national database.

Oxacillin-resistant Staphylococcus aureus (ORSA) is a virulent pathogen responsible for both health care-associated and community onset disease. We used SmaI-digested genomic DNA separated by pulsed-field gel electrophoresis (PFGE) to characterize 957 S. aureus isolates and establish a database of PFGE patterns. In addition to PFGE patterns of U.S. strains, the database contains patterns of representative epidemic-type strains from the United Kingdom, Canada, and Australia; previously described ORSA clonal-type isolates; 13 vancomycin-intermediate S. aureus (VISA) isolates, and two high-level vancomycin-resistant, vanA-positive strains (VRSA). Among the isolates from the United States, we identified eight lineages, designated as pulsed-field types (PFTs) USA100 through USA800, seven of which included both ORSA and oxacillin-susceptible S. aureus isolates. With the exception of the PFT pairs USA100 and USA800, and USA300 and USA500, each of the PFTs had a unique multilocus sequence type and spa type motif. The USA100 PFT, previously designated as the New York/Tokyo clone, was the most common PFT in the database, representing 44% of the ORSA isolates. USA100 isolates were typically multiresistant and included all but one of the U.S. VISA strains and both VRSA isolates. Multiresistant ORSA isolates from the USA200, -500, and -600 PFTs have PFGE patterns similar to those of previously described epidemic strains from Europe and Australia. The USA300 and -400 PFTs contained community isolates resistant only to beta-lactam drugs and erythromycin. Noticeably absent from the U.S. database were isolates with the previously described Brazilian and EMRSA15 PFGE patterns. These data suggest that there are a limited number of ORSA genotypes present in the United States.