Clyde Thornsberry

Surveillance for Antimicrobial Susceptibility among Clinical Isolates of Pseudomonas aeruginosa and Acinetobacter baumannii from Hospitalized Patients in the United States, 1998 to 2001

ABSTRACT Pseudomonas aeruginosa and Acinetobacter baumannii are the most prevalent nonfermentative bacterial species isolated from clinical specimens of hospitalized patients. A surveillance study of 65 laboratories in the United States from 1998 to 2001 found >90% of isolates of P. aeruginosa from hospitalized patients to be susceptible to amikacin and piperacillin-tazobactam; 80 to 90% of isolates to be susceptible to cefepime, ceftazidime, imipenem, and meropenem; and 70 to 80% of isolates to be susceptible to ciprofloxacin, gentamicin, levofloxacin, and ticarcillin-clavulanate. From 1998 to 2001, decreases in antimicrobial susceptibility (percents) among non-intensive-care-unit (non-ICU) inpatients and ICU patients, respectively, were greatest for ciprofloxacin (6.1 and 6.5), levofloxacin (6.6 and 3.5), and ceftazidime (4.8 and 3.3). Combined 1998 to 2001 results for A. baumannii isolated from non-ICU inpatients and ICU patients, respectively, demonstrated that >90% of isolates tested were susceptible to imipenem (96.5 and 96.6%) and meropenem (91.6 and 91.7%); fewer isolates from both non-ICU inpatients and ICU patients were susceptible to amikacin and ticarcillin-clavulanate (70 to 80% susceptible); and <60% of isolates were susceptible to ceftazidime, ciprofloxacin, gentamicin, or levofloxacin. From 1998 to 2001, rates of multidrug resistance (resistance to at least three of the drugs ceftazidime, ciprofloxacin, gentamicin, and imipenem) showed small increases among P. aeruginosa strains isolated from non-ICU inpatients (5.5 to 7.0%) and ICU patients (7.4 to 9.1%). From 1998 to 2001, rates of multidrug resistance among A. baumannii strains isolated from non-ICU inpatients (27.6 to 32.5%) and ICU patients (11.6 to 24.2%) were higher and more variable than those observed for P. aeruginosa. Isolates concurrently susceptible, intermediate, or resistant to both imipenem and meropenem accounted for 89.8 and 91.2% of P. aeruginosa and A. baumannii isolates, respectively, studied from 1998 to 2001. In conclusion, for aminoglycosides and most β-lactams susceptibility rates for P. aeruginosa and A. baumannii were constant or decreased only marginally (≤3%) from 1998 to 2001. Greater decreases in susceptibility rates were, however, observed for fluoroquinolones and ceftazidime among P. aeruginosa isolates.

The emergence of methicillin-resistant Staphylococcus aureus infections in United States hospitals. Possible role of the house staff-patient transfer circuit.

Infections with methicillin-resistant strains of Staphylococcus aureus appear to be occurring with increasing frequency in some U.S. hospitals about a decade after a similar increase in Britain and other countries. In the United States, clustered methicillin-resistant S. aureus infections reported in scientific journals and in three hospital surveys have been almost entirely in large, tertiary referral hospitals affiliated with medical schools. Among 63 hospitals regularly reporting infections from 1974 to 1981 in the National Nosocomial Infections Study, the increase in methicillin-resistant S. aureus infections was entirely due to substantial increases in only four hospitals, all of which were large, tertiary referral centers affiliated with medical schools. The predominance of methicillin-resistant S. aureus infections in these large hospitals may be due to the large numbers of patients at high risk of infection and to the interhospital spread of the organism by the transfer of infected patients and house staff from similar hospitals or from nursing homes.Abstract Infections with methicillin-resistant strains ofStaphylococcus aureusappear to be occurring with increasing frequency in some U.S. hospitals about a decade after a similar increase in Brit...

Trends in Antimicrobial Resistance among Urinary Tract Infection Isolates of Escherichia coli from Female Outpatients in the United States

ABSTRACT The Infectious Diseases Society of America advocates trimethoprim-sulfamethoxazole (SXT) as initial therapy for females with acute uncomplicated bacterial cystitis in settings where the prevalence of SXT resistance does not exceed 10 to 20%. To determine trends in the activities of SXT, ampicillin, ciprofloxacin, and nitrofurantoin among urine isolates of Escherichia coli from female outpatients, susceptibility testing data from The Surveillance Network (TSN) Database-USA (n = 286,187) from 1995 to 2001 were analyzed. Resistance rates among E. coli isolates to ampicillin (range, 36.0 to 37.4% per year), SXT (range, 14.8 to 17.0%), ciprofloxacin (range, 0.7 to 2.5%), and nitrofurantoin (range, 0.4 to 0.8%) varied only slightly over this 7-year period. Ciprofloxacin was the only agent studied that demonstrated a consistent stepwise increase in resistance from 1995 (0.7%) to 2001 (2.5%). In 2001, SXT resistance among E. coli isolates was >10% in all nine U.S. Bureau of the Census regions. At institutions testing ≥100 urinary isolates of E. coli (n = 126) in 2001, ampicillin (range, 27.3 to 98.8%) and SXT (range, 7.5 to 47.1%) resistance rates varied widely while ciprofloxacin (range, 0 to 12.9%) and nitrofurantoin (range, 0 to 2.8%) resistance rates were more consistent. In 2001, the most frequent coresistant phenotypes were resistance to ampicillin and SXT (12.0% of all isolates; 82.3% of coresistant isolates) and resistance to ampicillin, ciprofloxacin, and SXT (1.4% of all isolates; 9.9% of coresistant isolates). Coresistance less frequently included resistance to nitrofurantoin (3.5% of coresistant isolates) than resistance to ciprofloxacin (15.8%), SXT (95.7%), and ampicillin (98.1%). In conclusion, among urinary isolates of E. coli from female outpatients in the United States, national resistance rates to SXT were relatively consistent (14.8 to 17.0%) from 1995 to 2001 but demonstrated considerable regional and institutional variation in 2001. Therapies other than SXT may need to be considered in some locations.

Surveillance of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States in 1996-1997 respiratory season

A U.S. surveillance study of antimicrobial resistance in respiratory tract pathogens in the respiratory season (1996-1997) is reported that included 11,368 isolates from 434 institutions in 45 states and the District of Columbia. beta-lactamase was produced by 33.4% of Haemophilus influenzae and 92.7% of Moraxella catarrhalis. Of the 9,190 Streptococcus pneumoniae isolates tested, 33.5% were not susceptible to penicillin (MIC > or = 0.12 microgram/mL), with 13.6% having high-level resistance (MICs > 1 microgram/mL). For H. influenzae, the most active antimicrobials (based on percent of strains susceptible) were levofloxacin (100%) and ceftriaxone (99.9%); the least active were ampicillin (67.2%) and clarithromycin (58.1%). For M. catarrhalis, the most active drugs were amoxicillin-clavulanate, ceftriaxone, and levofloxacin (100%); the least active was ampicillin. The order of the activity of the drugs against S. pneumoniae were levofloxacin (97.3%) > ceftriaxone (87.1%) > amoxicillin-clavulanate (81.7%) = clarithromycin (80.9%) > cefuroxime (74.5%) > penicillin (66.5%). The activity of the beta-lactams and clarithromycin against isolates of S. pneumoniae was closely associated with the resistance to penicillin. Levofloxacin was more active against S. pneumoniae overall, because it exhibited no cross-resistance. These data indicate that the incidence of beta-lactamase production in H. influenzae (33.4%) and M. catarrhalis (92.7%) is similar to other recent studies, and that the incidence of penicillin-intermediate and -resistant S. pneumoniae is increasing, particularly the high-level penicillin-resistant (MICs > 1 microgram/mL) strains, which were often multi-resistant.

Multidrug-Resistant Urinary Tract Isolates of Escherichia coli: Prevalence and Patient Demographics in the United States in 2000

ABSTRACT Concurrent resistance to antimicrobials of different structural classes has arisen in a multitude of bacterial species and may complicate the therapeutic management of infections, including those of the urinary tract. To assess the current breadth of multidrug resistance among urinary isolates of Escherichia coli, the most prevalent pathogen contributing to these infections, all pertinent results in The Surveillance Network Database—USA from 1 January to 30 September 2000 were analyzed. Results were available for 38,835 urinary isolates of E. coli that had been tested against ampicillin, cephalothin, ciprofloxacin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Of these isolates, 7.1% (2,763 of 38,835) were resistant to three or more agents and considered multidrug resistant. Among the multidrug-resistant isolates, 97.8% were resistant to ampicillin, 92.8% were resistant to trimethoprim-sulfamethoxazole, 86.6% were resistant to cephalothin, 38.8% were resistant to ciprofloxacin, and 7.7% were resistant to nitrofurantoin. The predominant phenotype among multidrug-resistant isolates (57.9%; 1,600 of 2,793) included resistance to ampicillin, cephalothin, and trimethoprim-sulfamethoxazole. This was the most common phenotype regardless of patient age, gender, or inpatient-outpatient status and in eight of the nine U.S. Bureau of the Census regions. Rates of multidrug resistance were demonstrated to be higher among males (10.4%) than females (6.6%), among patients >65 years of age (8.7%) than patients ≤17 (6.8%) and 18 to 65 (6.1%) years of age, and among inpatients (7.6%) than outpatients (6.9%). Regionally, the rates ranged from 4.3% in the West North Central region to 9.2% in the West South Central region. Given the current prevalence of multidrug resistance among urinary tract isolates ofE. coli in the United States (7.1%), continued local, regional, and national surveillance is warranted.

Emerging resistance among bacterial pathogens in the intensive care unit – a European and North American Surveillance study (2000–2002)

BackgroundGlobally ICUs are encountering emergence and spread of antibiotic-resistant pathogens and for some pathogens there are few therapeutic options available.MethodsAntibiotic in vitro susceptibility data of predominant ICU pathogens during 2000–2 were analyzed using data from The Surveillance Network (TSN) Databases in Europe (France, Germany and Italy), Canada, and the United States (US).ResultsOxacillin resistance rates among Staphylococcus aureus isolates ranged from 19.7% to 59.4%. Penicillin resistance rates among Streptococcus pneumoniae varied from 2.0% in Germany to as high as 20.2% in the US; however, ceftriaxone resistance rates were comparably lower, ranging from 0% in Germany to 3.4% in Italy. Vancomycin resistance rates among Enterococcus faecalis were ≤ 4.5%; however, among Enterococcus faecium vancomycin resistance rates were more frequent ranging from 0.8% in France to 76.3% in the United States. Putative rates of extended-spectrum β-lactamase (ESBL) production among Enterobacteriaceae were low, <6% among Escherichia coli in the five countries studied. Ceftriaxone resistance rates were generally lower than or similar to piperacillin-tazobactam for most of the Enterobacteriaceae species examined. Fluoroquinolone resistance rates were generally higher for E. coli (6.5% – 13.9%), Proteus mirabilis (0–34.7%), and Morganella morganii (1.6–20.7%) than other Enterobacteriaceae spp (1.5–21.3%). P. aeruginosa demonstrated marked variation in β-lactam resistance rates among countries. Imipenem was the most active compound tested against Acinetobacter spp., based on resistance rates.ConclusionThere was a wide distribution in resistance patterns among the five countries. Compared with other countries, Italy showed the highest resistance rates to all the organisms with the exception of Enterococcus spp., which were highest in the US. This data highlights the differences in resistance encountered in intensive care units in Europe and North America and the need to determine current local resistance patterns by which to guide empiric antimicrobial therapy for intensive care infections.

Regional Trends in Antimicrobial Resistance among Clinical Isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States: Results from the TRUST Surveillance Program, 1999–2000

The ongoing TRUST (Tracking Resistance in the United States Today) study, which began monitoring antimicrobial resistance among respiratory pathogens in 1996, routinely tracks resistance at national and regional levels. The 1999-2000 TRUST study analyzed 9499 Streptococcus pneumoniae, 1934 Haemophilus influenzae, and 1108 Moraxella catarrhalis isolates that were prospectively collected from 239 laboratories across the 9 US Bureau of the Census regions. Penicillin-resistant S. pneumoniae varied significantly by region, from 8.3% to 24.8% (P<.001). In each region, penicillin resistance closely predicted resistance to other beta-lactams, macrolides, and trimethoprim-sulfamethoxazole. Levofloxacin resistance was 0.5% nationally (regional range, 0.1%-1.0%). Multidrug resistance also varied significantly (P<.001) by region. beta-Lactamase production among H. influenzae varied significantly (regional range, 24.0%-34.6%) and M. catarrhalis (86.2%-96.8%) also varied by region. Notable variation in regional antimicrobial resistance rates (S. pneumoniae) and beta-lactamase production (H. influenzae, M. catarrhalis) exists throughout the United States.

Antimicrobial susceptibility of five subgroups of Mycobacterium fortuitum and Mycobacterium chelonae.

Broth microdilution MICs were determined for 258 clinical isolates of Mycobacterium fortuitum (3 biovariants) and M. chelonae (2 subspecies) with amikacin, tobramycin, cefoxitin, doxycycline, erythromycin, and sulfamethoxazole-trimethoprim and with several new beta-lactams and aminoglycosides and ciprofloxacin. Variations in susceptibility by and within species subgroups confirm the need for susceptibility testing against clinically important strains.

Epidemiology and antibiotic susceptibility of bacteria causing skin and soft tissue infections in the USA and Europe: a guide to appropriate antimicrobial therapy

Susceptibility data for all organisms associated with a range of skin and soft tissue infections (SSTI) in hospitalised patients were studied. Data were reported by clinical laboratories in the USA, France, Germany, Italy and Spain during 2001 which participate in The Surveillance Network (TSN). Staphylococcus aureus, Enterococcus spp. and coagulase-negative staphylococci (CNS), Escherichia coli and Pseudomonas aeruginosa were the most prevalent pathogens in all countries. MRSA was detected in 44.4, 34.7, 12.4, 41.8 and 32. 4% of S. aureus in each country, respectively. The majority of MRSA were cross resistant to other compound classes tested except for vancomycin (100% susceptible) trimethoprim-sulphamethoxazole with range 1.7% (France) to 15.9% (Italy) resistant, and gentamicin with range 12.2% (France) to 87.0% (Italy) resistant. More than 99.0% of MSSA tested susceptible to ceftriaxone and >94.9% to trimethoprim-sulphamethoxazole. 87.2% (France) to 94.6% of MSSA (Germany) were ciprofloxacin susceptible; 73.2% (USA) to 86.6% (Spain) were erythromycin susceptible; 85.4% (Italy) to 99.2% (France) were gentamicin susceptible. MSSA were more frequently found and generally more antibiotic susceptible from out patients. Overall, 100% of Streptococcus agalactiae and Streptococcus pyogenes were susceptible to penicillin, ceftriaxone and cefotaxime. Macrolide resistance was common among S. agalactiae (20.7%, Germany to 10%, Italy and Spain), S. pyogenes (19.2%, France to 11.1%, USA) and viridans streptococci (25.7%, France to 14.1%, Germany). Vancomycin-resistant Enterococcus spp. were uncommon outside the USA (17.5%) and Italy (7.4%). For all countries susceptibility of E. coli was 100% to imipenem, >98.7% to amikacin, >96.0% to ceftriaxone and cefotaxime. Susceptibility of E. coli isolates to ciprofloxacin was 77.6% in Spain to 94.3% in Germany. Klebsiella spp., Proteus spp., Citrobacter spp. and Enterobacter spp. displayed varying susceptibilities between countries to drugs tested. Putative extended spectrum beta-lactamase expression in E. coli remained rare comprising 4-5% of isolates in USA, Italy and Spain and in France and Germany <2%. For P. aeruginosa piperacillin-tazobactam, amikacin, imipenem and ceftazidime were the most active compounds tested irrespective of region. Surveillance data should be considered when selecting empirical therapy for treating SSTI.

Prevalence and antimicrobial susceptibilities of bacteria isolated from blood cultures of hospitalized patients in the United States in 2002

BackgroundBloodstream infections are associated with significant patient morbidity and mortality. Antimicrobial susceptibility patterns should guide the choice of empiric antimicrobial regimens for patients with bacteremia.MethodsFrom January to December of 2002, 82,569 bacterial blood culture isolates were reported to The Surveillance Network (TSN) Database-USA by 268 laboratories. Susceptibility to relevant antibiotic compounds was analyzed using National Committee for Clinical Laboratory Standards guidelines.ResultsCoagulase-negative staphylococci (42.0%), Staphylococcus aureus (16.5%), Enterococcus faecalis (8.3%), Escherichia coli (7.2%), Klebsiella pneumoniae (3.6%), and Enterococcus faecium (3.5%) were the most frequently isolated bacteria from blood cultures, collectively accounting for >80% of isolates. In vitro susceptibility to expanded-spectrum β-lactams such as ceftriaxone were high for oxacillin-susceptible coagulase-negative staphylococci (98.7%), oxacillin-susceptible S. aureus (99.8%), E. coli (97.3%), K. pneumoniae (93.3%), and Streptococcus pneumoniae (97.2%). Susceptibilities to fluoroquinolones were variable for K. pneumoniae (90.3–91.4%), E. coli (86.0–86.7%), oxacillin-susceptible S. aureus (84.0–89.4%), oxacillin-susceptible coagulase-negative staphylococci (72.7–82.7%), E. faecalis (52.1%), and E. faecium (11.3%). Combinations of antimicrobials are often prescribed as empiric therapy for bacteremia. Susceptibilities of all blood culture isolates to one or both agents in combinations of ceftriaxone, ceftazdime, cefepime, piperacillin-tazobactam or ciprofloxacin plus gentamicin were consistent (range, 74.8–76.3%) but lower than similar β-lactam or ciprofloxacin combinations with vancomycin (range, 93.5–96.6%).ConclusionOngoing surveillance for antimicrobial susceptibility remains essential, and will enhance efforts to identify resistance and attempt to limit its spread.