Cephamycin Resistance in Clinical Isolates and Laboratory-derived Strains of Escherichia coli, Nova Scotia, Canada

AmpC β-lactamase, altered porins, or both are usually responsible for cefoxitin resistance in Escherichia coli. We examined the relative importance of each. We studied 18 strains of clinical isolates with reduced cefoxitin susceptibility and 10 initially-susceptible strains passaged through cefoxitin-gradient plates. Of 18 wild-resistant strains, 9 had identical promoter mutations (including creation of a consensus 17-bp spacer) and related pulsed-field gel electrophoresis patterns; the other 9 strains were unrelated. Nine strains had attenuator mutations; two strains did not express OmpC or OmpF. After serial passage, 8 of 10 strains developed cefoxitin resistance, none developed promoter or attenuator mutations, 6 lost both the OmpC and OmpF porin proteins, and 1 showed decreased production of both. One strain had neither porin alteration or increased AmpC production. Porin mutants may occur more commonly and be less fit and less inclined to spread or cause disease than strains with increased β-lactamase expression

Clinical effectiveness of rapid tests for methicillin resistant Staphylococcus aureus (MRSA) in hospitalized patients: a systematic review

<p>Abstract</p> <p>Background</p> <p>Methicillin resistant <it>Staphylococcus aureus </it>(MRSA) are often resistant to multiple classes of antibiotics. The research objectives of this systematic review were to evaluate the clinical effectiveness of polymerase chain reaction (PCR) versus chromogenic agar for MRSA screening, and PCR versus no screening for several clinical outcomes, including MRSA colonization and infection rates.</p> <p>Methods</p> <p>An electronic literature search was conducted on studies evaluating polymerase chain reaction techniques and methicillin (also spelled meticillin) resistant <it>Staphylococcus aureus </it>that were published from 1993 onwards using Medline, Medline In-Process & Other Non-Indexed Citations, BIOSIS Previews, and EMBASE. Due to the presence of heterogeneity in the selected studies, the clinical findings of individual studies were described.</p> <p>Results</p> <p>Nine studies that compared screening for MRSA using PCR versus screening using chromogenic agar in a hospital setting, and two studies that compared screening using PCR with no or targeted screening were identified. Some studies found lower MRSA colonization and acquisition, infection, and transmission rates in screening with PCR versus screening with chromogenic agar, and the turnaround time for screening test results was lower for PCR. One study reported a lower number of unnecessary isolation days with screening using PCR versus screening with chromogenic agar, but the proportion of patients isolated was similar between both groups. The turnaround time for test results and number of isolation days were lower for PCR versus chromogenic agar for MRSA screening.</p> <p>Conclusions</p> <p>The use of PCR for MRSA screening demonstrated a lower turnaround time and number of isolation days compared with chromogenic agar. Given the mixed quality and number of studies (11 studies), gaps remain in the published literature and the evidence remains insufficient. In addition to screening, factors such as the number of contacts between healthcare workers and patients, number of patients attended by one healthcare worker per day, probability of colonization among healthcare workers, and MRSA status of hospital shared equipment and hospital environment must be considered to control the transmission of MRSA in a hospital setting.</p

Risk of coinfection with Chlamydia trachomatis and Neisseria gonorrhoeae in Nova Scotia

BACKGROUND: The frequency of Chlamydia trachomatis and Neisseria gonorrhoeae coinfection can vary depending on their individual incidence and prevalence rates

An Evaluation of Extended Incubation Time with Blind Subculture of Blood Cultures in Patients with Suspect Endocarditis

BACKGROUND: In a small proportion of patients, bacterial endocarditis is due to organisms that grow slowly and may not be recovered in conventional blood cultures incubated for five days. This has led to recommendations for prolonged incubation and routine subculture of negative cultures

Extended-Spectrum Beta-Lactamases

The definition of extended-spectrum beta-lactamases (ESBLs) has expanded rapidly, in terms of both the number and the variety of enzymes. Bacteria bearing plasmidic ESBLs are spreading widely throughout the world. In Canada, the problem has grown less rapidly than in other parts of the world; however, ESBLs still present a significant impediment to the treatment of serious infections with extendedspectrum cephalosporins and penicillins. Although SHV-derived enzymes were the primary concern in the late 1980s and early 1990s, these enzymes have been rapidly overtaken by the CTX-M family of ESBLs. There is no reason to believe that the problem of ESBLs will not expand rapidly in the face of intense antimicrobial pressure and lapses in infection control practices. Control should focus on early detection, accurate characterization, effective treatment and measures to prevent further spread

Doctor, there's a tadpole in my feces!

A 36-year-old male resident of a coastal Nova Scotia community presented to his family physician after he noted moving objects in his feces (Figure 1). Although concerned and revolted, he was asymptomatic. He was worried that the organisms were an intestinal parasite he had passed in his stool. The organisms were approximately 2.5 cm long and resembled tadpoles. The fecal sample was sent to the Parasitology Section at the Queen Elizabeth II Health Sciences Centre in Halifax, Nova Scotia, for identification

Predominance of herpes simplex virus type 1 from patients with genital herpes in Nova Scotia

The epidemiology of genital herpes is changing with evidence to suggest an increasing incidence of herpes simplex virus type 1 (HSV-1) infections. The results of 6529 HSV genital cultures taken between April 1998 and December 2001 were reviewed. overall, HSV-1 was recovered more often than HSV-2; 1213 versus 1045. This trend was particularly striking in young women 30 years of age or less, in whom 70.8% of isolates were HSV-1. In men of the same age range, 45% of isolates were HSV-1. The proportion of women with HSV-1 declined from 73.7% in those younger than 31 years of age to 4.5% in those older than 60 years of age