to ciprofloxacin, clindamycin, metronidazole, piperacillin,

Vol. 37, No. 8ANTiMICROBLAL AGENTS AND CHEMOTHERAPY, Aug. 1993, p. 1649-16540066-4804/93/081649-06$02.00/0Copyright © 1993, American Society for Microbiology

Susceptibilities of 428 Gram-Positive and -Negative AnaerobicBacteria to Bay y3118 Compared with Their Susceptibilitiesto Ciprofloxacin, Clindamycin, Metronidazole, Piperacillin,

Piperacillin-Tazobactam, and CefoxitinG. A. PANKUCH,1 M. R. JACOBS,2 AND P. C. APPELBAUM'*

Departments ofPathology (Clinical Microbiology), Hershey Medical Center, Hershey,Pennsylvania 17033,1 and Case Western Reserve University, Cleveland, Ohio 441062

Received 8 March 1993/Accepted 26 May 1993

The susceptibilities of 428 gram-negative and gram-positive anaerobes (including selected cefoxitin-resistantstrains) to Bay y3118 (a new fluoroquinolone), ciprofloxacin, clindamycin, metronidazole, cefoxitin, piperacil-lin, and piperacillin-tazobactam were tested. Organisms comprised 115 BacteroidesfragUis group, 116 non-B.fragilis Bacteroides, PrevoteUa, and Porphyromonas spp., 40 fusobacteria, 58 peptostreptococci, 48 gram-positive non-spore-forming rods, and 51 clostridia. P-Lactamase production was demonstrated in 87% of thegram-negative rods but in none of the gram-positive organisms. Overall, Bay y3118 was the most active agent,with all organisms inhibited at an MIC of <2.0 ,g/ml (MICs for 50%o [MIC5J1 and 90%o [MIC90] of strainstested, 0.125 and 0.5 p,g/ml, respectively). By contrast, ciprofloxacin was much less active, with only 42% ofstrains susceptible at a breakpoint of 2.0 ,Lg/ml (MIC50, 4.0 ,ug/ml; MIC,0, 16.0 ,ug/ml). Metronidazole wasactive against all gram-negative rods, but 7% of peptostreptococci, 83% of gram-positive non-spore-formingrods, and 4% of non-Clostridium perfringens, non-Clostridium diJfficile clostridia were resistant to this agent(MICs, >16.0 ig/ml). Clindamycin was active against 94% of Bacteroides, PrevoteUa, and Porphyromonasspp., 91% of peptostreptococci, and 100%6 of gram-positive non-spore-forming rods, but was active againstonly 701% of fusobacteria and 53% of clostridia. Cefoxitin was active against .90%o of all groups except the B.fragilis group and non-Propionibacterium acnes gram-positive non-spore-forming rods (both 85%) and C.diffile (20%k). Significant enhancement of piperacillin by tazobactam was seen in all 13-lactamase-positivestrains (991% susceptible; MICo,, 8.0 ,Lg/ml), and all 13-lactamase-negative strains were susceptible topiperacillin (MIC90, 8.0 ,ug/ml). Clinical studies are required to delineate the role ofBay y3118 in the treatmentof anaerobic infections.

Anaerobes are well-established human pathogens, espe-cially when host defenses are lowered by processes such astrauma, malignancy, surgery, and malnutrition (1, 27). Al-though gram-negative rods (in particular, the Bacteroidesfragilis group) represent the most important group of patho-genic anaerobes in humans, infections with other anaerobicgram-negative rods as well as with anaerobic gram-positivecocci and rods (spore formers as well as non-spore formers)are increasingly encountered (5, 27). The susceptibility pat-terns of clinically significant anaerobes are changing. 3-Lac-tamase production and resistance to 3-lactams are usuallyencountered in the B. fragilis group. However, both of thelatter phenomena have been increasingly found in non-B.fragilis group Bacteroides, Prevotella, Porphyromonas, andFusobacterium species (2-7, 9, 19). Although imipenemresistance in the B. fragilis group is exceedingly rare in theUnited States and Europe (5, 19), approximately 6% of B.fragilis and Bacteroides thetaiotaomicron strains in Japanare currently resistant to this antimicrobial agent; 29% ofthese strains produce imipenemase (9a). Not all anaerobesare susceptible to clindamycin, and metronidazole resistancehas been encountered in anaerobic gram-positive cocci (7,12). 1B-Lactamase production has also been described insome non-Clostridium perfringens Clostridium species (8,22).The development of agents such as fluoroquinolones, new

* Corresponding author.

j-lactam-1-lactamase inhibitor combinations, new broad-spectrum ,B-lactams, and other compounds mandates sus-ceptibility testing surveys by standardized methods for clin-ical strains isolated within a few years of the survey (5, 19).The currently marketed fluoroquinolones such as ciproflox-acin and ofloxacin are not active against most groups ofanaerobic bacteria (16, 17). Bay y3118 {8-chloro-1-cyclopro-pyl-7-[(S,S)-2,8-diazabicyclo[4.3.0.1-non-8-yl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolone-carboxylic acid hydrochloride} isa new fluoroquinolone with potent antibacterial activityagainst both aerobic and anaerobic bacteria (10, 13, 20, 23,28). In the survey described here, we used standard methodsto compare the activity of Bay y3118 with those of clindamy-cin, ciprofloxacin, metronidazole, piperacillin, piperacillin-tazobactam, and cefoxitin against 115 B. fragilis group, 116non-B. fragilis group Bacteroides, Prevotella, and Porphy-romonas species, 40 fusobacteria, 58 anaerobic cocci, 48anaerobic gram-positive non-spore-forming rods, and 51clostridia.

MATERIALS AND METHODSBacteria. Organisms were obtained from Hershey Medical

Center, University Hospitals of Cleveland, and the centerslisted in the Acknowledgments Ijn addition, 3 imipenem-resistant B. fragilis strains (2 irtipenemase producers) werekindly provided by K. Ueno (Gifu University School ofMedicine, Gifu, Japan), and 11 cefoxitin-resistant membersof the B. fragilis group were obtained from D. Shungu

1649

ANTIMICROB. AGENTS CHEMOTHER.

(Merck & Co., Rahway, N.J.). Strains other than the latterwere all recent clinical strains that were isolated between1988 and 1992 and that were obtained from normally sterilesites, blood cultures, and material from patients with orofa-cial, pulmonary, intra-abdominal, upper genital tract, andother infections. Most strains were obtained prior to theinstitution of antimicrobial therapy. Gram-negative rodswere selected such that f-lactamase-positive strains pre-dominated. Strains were stored in double-strength skim milk(Difco Laboratories, Detroit, Mich.) at -70°C. Prior totesting, the organisms were checked for purity as describedpreviously (5). Identification was by standard methods (1,18, 27).

13-Lactamase and susceptibility testing. f-Lactamase test-ing was done by the nitrocefin disk method (Cefinase disks;BBL Microbiology Systems, Cockeysville, Md.) as de-scribed previously (4). Testing of susceptibility to Bay y3118and ciprofloxacin (Miles, Inc., West Haven, Conn.), clin-damycin (The Upjohn Company, Kalamazoo, Mich.), met-ronidazole (Searle, Inc., Skokie, Ill.), piperacillin and piper-acillin-tazobactam (Lederle Laboratories, Pearl River,N.Y.), and cefoxitin (Merck Laboratories, West Point, Pa.)was performed by the agar dilution method recommended bythe National Committee for Clinical Laboratory Standards(21) with Wilkins-Chalgren agar supplemented with 5%sterile defibrinated sheep blood for fastidious organisms.Plates were incubated in an anaerobe chamber (Coy Labo-ratory Products, Ann Arbor, Mich.) in an atmosphere of 80%N2-10% C02-10% H2. Standard anaerobic quality controlswere included in each run (21). Tazobactam was added topiperacillin at a fixed concentration of 4.0 ,ug/ml (7). Defini-tion of enhancement of piperacillin by tazobactam was asdescribed previously (2). When available, National Commit-tee for Clinical Laboratory Standards breakpoints (21) wereused. The following susceptibility breakpoints were used:2.0 ,ug/ml for Bay y3118 and ciprofloxacin, 4.0 ,g/ml forclindamycin, 16.0 ,ug/ml for metronidazole, 32.0 p,g/ml forcefoxitin, and 64.0 ,g/ml for piperacillin and piperacillin-tazobactam. The breakpoint chosen for Bay y3118 wasempiric, because no standardized breakpoint is currentlyavailable for this compound.

RESULTS

P-Lactamase production was demonstrated in 97% of B.fragilis group strains, 90% of non-B. fragilis group Bacte-roides, Prevotella, and Porphyromonas species, and 52% offusobacteria. By contrast, none of the gram-positive strainswas shown to produce 1-lactamase. The susceptibilities ofall organisms to the various antimicrobial agents tested arepresented in Table 1. Because the majority of gram-negativerods produced j3-lactamase, results for enzyme-positive and-negative strains are presented together. With the exceptionof the fusobacteria (see below), the results for enzyme-negative strains did not differ significantly from those ob-tained when ,-lactamase-producing strains were analyzedseparately.As can be seen from Table 1, Bay y3118 was extremely

active against all anaerobe groups at MICs of .2.0 ,ug/ml(100% susceptible at this provisional breakpoint), with anoverall MIC for 50% of isolates tested (MIC50) of 0.125 p,g/mland an MIC90 of 0.5 p,g/ml. For only five strains MICs were2.0 ,ug/ml; these strains comprised four strains of Fusobac-terium varium and one strain of Clostridium clostridioforme.Members of the B. fragilis groups were more susceptiblethan members of the other groups; the MIC50 of Bay y3118

was 0.125 ,ig/ml, and the MIC90 was 0.25 ,ug/ml. By contrast,only 42% of strains were susceptible to ciprofloxacin; theMIC50 was 4.0 ,g/ml, and the MIC. was 16.0 ,ug/ml. OnlyPorphyromonas asaccharolytica, Propionibactenum acnes,and C. perfringens strains were consistently susceptible tociprofloxacin, with >90% of strains inhibited at MICs of'1.0 ,ug/ml. Although metronidazole was active against allgram-negative rods, 7% of peptostreptococci, 83% of gram-positive non-spore-forming rods, and 4% of non-C. perfrin-gens, non-Clostridium difficile clostridia were resistant tothis agent. Clindamycin was active against 92% of B. fragilisgroup strains and 96% of non-B. fragilis group Bacteroides,Prevotella, and Porphyromonas species, 91% of peptostrep-tococci, 100% of gram-positive non-spore-forming rods, and92% of C. perfringens. By contrast, only 70% of fusobacteria(10% of F. varium), 53% of C. difficile, and 33% of miscel-laneous clostridia were susceptible to this compound. Ce-foxitin was active against 90% of strains overall, but only20% of the C. difficile strains were susceptible. Significantenhancement of piperacillin by tazobactam was seen in all,-lactamase-positive strains (99% susceptible to the combi-nation; MICg, 8.0 ,ug/ml), and all P-lactamase-negativestrains were susceptible to piperacillin (MICg, 8.0 jig/ml).,3-Lactamase-producing strains were all resistant to tazobac-tam alone (MIC, 216.0 ,ug/ml), whereas 55% of ,-lactamase-negative, gram-negative and -positive strains were moresusceptible to this compound (MICs, <16.0 ,g/ml).MICs of the non-1-lactams for the 35 ,B-lactamase-nega-

tive, gram-negative rods did not differ from those seen forP-lactamase-positive strains. However, piperacillin MICsfor enzyme-negative strains were lower than those seen forenzyme-positive strains (MIC90s, 4.0 versus >64.0 ,ug/ml).With the exception of C. difficile and some strains oflactobacilli, cefoxitin MICs were also lower for 3-lactamase-negative strains (MIC90s, 4.0 versus 32.0 ,ug/ml). Whenresults for P-lactamase-positive Fusobacterium nucleatumand Fusobacterium necrophorum strains were analyzed sep-arately, enhancement of piperacillin by tazobactam similarto that seen in other 3-lactamase-positive, gram-negativeanaerobic rods was observed (MIC90s, 64.0 ,ug/ml withoutinhibitor and 8.0 ,ug/ml with inhibitor).

DISCUSSION

The existing fluoroquinolones, although exhibiting broad-spectrum activity against aerobes, yield relatively high MICsfor anaerobes (16, 17). Goldstein and Citron (16, 17) havefound the MIC90s of ciprofloxacin and ofloxacin to be .8.0,ug/ml for most anaerobic species, including the B. fragilisgroup; only the Bacteroides ureolyticus group, C. perfrin-gens, and Propionibacterium species were susceptible(MIC.s, .1.0 jig/ml). In the current study, only P. asac-charolytica, P. acnes, and C. perffingens strains were sus-ceptible to ciprofloxacin (MICs, .1.0 ,ug/ml). Bay y3118, anew fluoroquinolone, has been found to exhibit potentactivity against a broad spectrum of aerobic organisms,including methicillin-resistant Staphylococcus aureus, strep-tococci (including Enterococcus faecalis and Streptococcuspneumoniae), members of the family Enterobacteriaceae,and Pseudomonas aeruginosa (10, 20, 23, 28). In one pre-liminary study, Endermann and Bremm (13) have alsoshown that Bay y3118 has potent activity against anaerobesin vitro, with all 32 strains tested (including 19 B. fragilisgroup, 8 Clostridium species, and 5 peptostreptococci) beinginhibited by Bay y3118 at <0.5 ,g/ml. Endermann andBremm (13) also reported the excellent activity of Bay y3118

1650 PANKUCH ET AL.

ANAEROBE SUSCEPTIBILITY TO Bay y3118 1651

TABLE 1. Antimicrobial susceptibilities of anaerobic strains

Organism and MIC.5 MIC90 % Suscep-antimicrobial agent (,g/ml) (Pg/ml) tibility°

TABLE 1-Continued

Organism and MIC50 MICgo % Suscep-antimicrobial agent (Ag/ml) (pg/ml) tibilitya

Bacteroides fragilis (43/43b)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

0.125 0.1254.0 16.02.0 4.00.25 2.016.0 >64.08.0 >64.00.5 2.0

Bacteroides ureolyticus (9/9)100 Bay y31182 Ciprofloxacin

100 Metronidazole91 Clindamycin84 Cefoxitin72 Piperacillin93 Piperacillin-tazobactam

Bacteroides thetaiotaomicron(31/31)

Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

0.1254.02.00.5

16.016.04.0

0.2516.04.02.0

32.064.016.0

10013

1001009490100

Bacteroides capillosus (10/10)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Bacteroides ovatus (11/11)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacilinPiperacillin-tazobactam

Bacteroides distasonis (10/8)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacilin-tazobactam

Bacteroides vulgatus (11/9)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

0.25 0.2516.0 >16.01.0 2.01.0 >16.0

16.0 64.064.0 >64.04.0 8.0

0.125 0.254.0 16.01.0 2.00.25 2.0

16.0 64.08.0 >64.02.0 8.0

0.125 0.258.0 >16.02.0 4.00.5 >16.016.0 32.08.0 64.00.5 8.0

Porphyromonas asaccharo-lytica (10/8)

100 Bay y31180 Ciprofloxacin

100 Metronidazole73 Clindamycin73 Cefoxitin55 Piperacilin100 Piperacilin-tazobactam

Prevotella bivia (35/34)100 Bay y311810 Ciprofloxacin


10018

1008210091100

Prevotella disiens (11/9)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Bacteroides uniformis (9/9)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

0.258.02.01.0

16162.0

0.516.04.04.0

>64.0>64.0

4.0

Prevotella oris (Prevotellabuccae) (10/5)


100 Metronidazole89 Clindamycin78 Cefoxitin67 Piperacilin100 Piperacillin-tazobactam

Bacteroides fragilis group(115/111)


0.125 0.254.0 16.02.0 4.00.25 4.016.0 64.016.0 >64.01.0 8.0

Prevotella melaninogenica(12/12)



Continued

0.1254.04.00.258.04.00.125

0.516.04.02.0

32.016.00.25

100251001009292100

Continued on followingpage

0.1254.04.00.258.04.00.5

0.258.04.02.0

16.08.04.0

100331008910089100

0.1254.02.00.1254.08.00.125

0.516.04.01.0

16.016.00.5

1004010010010090100

0.1251.00.50.1250.250.250.125

0.516.04.00.1252.04.00.125

0.1252.02.00.1252.04.00.125

0.1251.02.00.1250.250.250.125

0.5>16.0

4.00.1258.0

32.00.125

0.1254.04.00.258.0

16.00.25

10090100100100100100

1000

10094100100100

10073100100100100100

0.1254.01.00.1252.02.00.125

0.2516.04.08.0

32.064.08.0

10040100809090100

VOL. 37, 1993


TABLE 1-Continued

Organism and MIC50 MIC90 % Suscep-antimicrobial agent (pg/ml) (p1g/mi) tibilitya

TABLE 1-Continued

Organism and MIC50 MIC90 % Suscep-antimicrobial agent (pg/ml) (pg/ml) tibilitya

Prevotella intermedia(12/12)


Miscellaneous strainsc (7/5)Bay y3118CiprofloxacinMetronidazoleChindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Non-Bacteroides fragilisBacteroides, Prevotella,and Porphyromonas spp.(116/104)


Fusobacterium nucleatum (11/6)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Fusobacterium necrophorum(12/2)


Fusobacterium mortiferum (7/6)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Fusobacterinum varium (10/7)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

0.125 0.54.0 >16.01.0 4.00.125 2.01.0 16.04.0 16.00.125 0.5

0.125 0.1251.0 16.02.0 4.00.125 0.50.25 8.02.0 32.00.125 0.5

0.125 0.54.0 32.02.0 4.00.125 1.02.0 16.04.0 32.00.125 0.5

0.06 0.252.0 >16.00.5 2.00.125 8.00.125 32.00.125 16.0

<0.125 8.0

0.03 0.251.0 4.00.125 2.00.125 1.00.125 2.00.125 0.5

<0.125 0.125

0.064.01.01.08.04.00.5

0.258.04.02.0

16.08.01.0

0.5 2.08.0 16.00.5 4.0

>16.0 >16.08.0 32.04.0 8.04.0 8.0

1003310010010092100

10057100100100100100

10034100969897

All fusobacteria (40/21)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Peptostreptococcid (58/0)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Propionibacterium acnes(15/0)


100 Other gram-positive anaero-bic non-spore-formingrodse (33/0)

100 Bay y311855 Ciprofloxacin100 Metronidazole82 Clindamycin91 Cefoxitin100 Piperacillin100 Piperacillin-tazobactam

1007510010092100100

Clostridium perfringens (12/0)Bay y3118CiprofloxacinMetronidazoleClindamycinCefoxitinPiperacillinPiperacillin-tazobactam

Clostridium difficile (15/0)100 Bay y311814 Ciprofloxacin


Other clostridiaf (24/0)100 Bay y311810 Ciprofloxacin

100 Metronidazole10 Clindamycin

100 Cefoxitin100 Piperacillin100 Piperacillin-tazobactam

Continued

0.06 1.04.0 16.00.5 4.00.5 >16.02.0 32.00.5 8.00.125 4.0

0.06 0.251.0 4.02.0 4.00.25 2.00.25 2.00.125 1.00.125 1.0

0.125 0.1251.0 1.0

>16.0 >16.00.125 0.1250.125 0.250.25 1.00.125 0.5

0.125 0.52.0 16.0

>16.0 >16.00.125 1.04.0 >64.01.0 8.00.5 8.0

0.125 0.1250.5 0.52.0 4.01.0 4.01.0 1.00.125 0.1250.125 0.125

0.5 0.58.0 16.02.0 8.04.0 >16.0

>64.0 >64.08.0 16.08.0 16.0

100451007095100100

100819391100100100

100100

0100100100100

100612410085

100100

10010010092100100100

10013

1005320100100

0.25 0.5 1000.5 8.0 792.0 16.0 96

16.0 >16.0 331.0 8.0 922.0 16.0 1001.0 16.0 100

Continued on followingpage

1652 PANKUCH ET AL.

ANAEROBE SUSCEPTIBILITY TO Bay y3118 1653

TABLE 1-Continued

Organism and MIC50 MIC9( % Suscep-antimicrobial agent (pg/ml) (ig/ml) tibility"

All strains (428/236)Bay y3118 0.125 0.5 100Ciprofloxacin 4.0 16.0 42Metronidazole 2.0 16.0 89Clindamycin 0.25 8.0 87Cefoxitin 2.0 32.0 90Piperacillin 2.0 64.0 93Piperacillin-tazobactam 0.25 8.0 99

a See Materials and Methods for breakpoints.b Number of strains tested/number of strains ,B-lactamase positive.c Three Prevotella loescheii, two Prevotella corpora, one Prevotella oralis,

and one Porphyromonas gingivalis.d Fifteen P. anaerobius, 14 P. tetradius, 13 P. magnus, 11 P. asaccharo-

lyticus, 2 P. micros, 1 P. prevotii, 1 P. productus, and 1 P. hydrogenalis.' Eight Eubactenum lentum, one Eubacteriwn aerofaciens, four Lactoba-

cillus casei, three Lactobacillus acidophilus, one Lactobacillus plantarum,three LactobaciUlus spp., one Bifidobacterium breve, four Bifidobacteriumspp., three Actinomyces odontolyticus, two Actinomyces naeslundii, oneActinomyces israelii, one Actinomyces viscosus, and one Actinomyces mey-eni.fTen C. tertium, five C innocuum, three C. clostridioforme, two C.

ramosum, one C sporogenes, one C. butyricum, one C. paraputificum, andone C. cadaveris.

against B. fragilis in a groin infection animal model, with adose of 2.0 mg/kg of body weight resulting in a 7-log-unitdecrease in the mean bacterial count. The MICs in thecurrent study were a little higher than those found in theGerman study (13); this can be explained by the lowerinoculum size (104 bacteria per ml) used by the latterworkers (13). Both studies, however, showed that Bay y3118has superior activity against B. fragilis compared with thatagainst other anaerobes, with MICs for most organismsbeing <0.125 p,g/ml; the in vitro activity of Bay y3118 wassuperior to those of ciprofloxacin, clindamycin, cefoxitin,and metronidazole (13). In the current study, for only fivestrains were Bay y3118 MICs 22.0 p,g/ml. Of these, fourwere F. vanium. Other reports have documented the relativeresistance of fusobacteria to quinolones compared with theresistances of other groups of anaerobes (6, 9, 17). Theuniform susceptibility of the three imipenem-resistant strainsfrom Japan to Bay y3118 in the current study mirrors thefindings of Ueno (29) that imipenem-resistant strains fromJapan are susceptible to Bay y3118 but are resistant to theother new quinolones tested.The results of the present study also confirm the excellent

activity of piperacillin against 3-lactamase-negative anaer-obes and of piperacillin-tazobactam against P-lactamase-positive anaerobes (2, 6, 7). Lower f-lactam MICs forP-lactamase-negative anaerobic strains and the lack of en-hancement of 1-lactams by P-lactamase inhibitors in 1-lactamase-positive F. varium strains have been describedbefore (5-7).As expected, all gram-negative strains tested were suscep-

tible to metronidazole (5, 12, 19). The resistance of anaero-bic, gram-positive non-spore-forming rods to metronidazoleis expected, and the resistance of peptostreptococci tometronidazole has been described previously (7, 11, 12, 24).However, the relatively high metronidazole MICs for non-C.perfringens Clostridium species were unexpected. Chow andcoworkers (11) have found that for 4 of 13 (31%) non-C.perfringens clostridia tested, metronidazole MICs were>25.0 ,ug/ml, compared with 100% susceptibility at MICs of<1.6 ,g/ml for C. perfringens (11). Rolfe and Finegold (24)

have reported that two of four strains of C. clostnidioformetested resistant to metronidazole (MICs, >256.0 ,ug/ml).Additionally, clinical failures with metronidazole therapyhave been reported in patients with systemic Clostridiumsordellii infections (26). More studies are necessary in orderto determine whether metronidazole resistance in non-C.perfringens clostridia is more common than previously sus-pected.Because of the relatively high number of cefoxitin-resis-

tant members of the B. fragilis group included in the currentstudy, MICs were higher than those reported by otherworkers (5, 19). Lack of cefoxitin activity against C. difficilehas been described before (24). Some members of all groupsof anaerobes, especially F. vanium and clostridia, wereresistant to clindamycin. F. varium is inherently resistant toa range of 1-lactam and non-13-lactam agents; George andcoworkers (15) have reported that none of five F. variumstrains tested susceptible to clindamycin. However, with87% of strains being susceptible in the current study, clin-damycin remains active against most clinically significantanaerobes.

It is recognized that the results of in vitro anaerobesusceptibility testing do not always correlate with in vivofindings. Reasons for the latter phenomenon may includemethodological problems in susceptibility testing (e.g., me-dium, inoculum, susceptibility breakpoint), the type andspectrum of anaerobes tested, and pharmacokinetic factors.Most clinicians feel that penicillin is the preferred drug fortherapy of fusobacterial infections (14), despite the propen-sity of fusobacteria to produce 1-lactamase (5-7). The rea-son for the latter discrepancy may be the relatively low1-lactam MICs for 3-lactamase-producing fusobacteria (5-7)compared with those for 3-lactamase-producing speciessuch as members of the B. fragilis group (19), together withthe high therapeutic doses of 3-lactam used (14). Clindamy-cin is almost always active against fusobacteria in vivo (14),despite the relatively poor in vitro results obtained in thecurrent study. It is, however, recognized that human infec-tions with F. vanium, the most clindamycin-resistant Fuso-bacterium species tested in our study, are rather rare (15).Data on the efficacy of cefoxitin in the treatment of anaero-bic infections correlate with results from unselected in vitrosurveys (unlike the current survey, in which selected 1-lac-tamase-producing and cefoxitin-resistant strains were test-ed), in which >95% of strains were susceptible at a break-point of 32.0 ,ug/ml (5, 14, 19). Although 42% of all strainswere susceptible to ciprofloxacin in the current study, clus-tering around the breakpoint occurred, such that ciproflox-acin is not recommended for use in the treatment of anaer-obic infections. Indeed, anaerobic flora in human volunteershave been found to be unchanged after oral ciprofloxacinadministration (25).

In summary, Bay y3118 showed excellent activity againstall groups of anaerobes tested and compared favorably to theexisting compounds used for the treatment of anaerobicinfections. In particular, excellent activity against the B.fragilis group was found, in contrast to the greater resistanceof this group to most antimicrobial agents. Clinical studiesare required to confirm these in vitro findings.

ACKNOWLEDGMENTSThis study was supported by a grant from Miles, Inc.We thank P. Schreckenberger (University of Illinois Health

Sciences Center, Chicago, Ill.), D. Citron (St. John and SantaMonica Hospitals, Santa Monica, Calif.), W. Brown (Hutzel Hos-pital, Detroit, Mich.), and J. Rosenblatt (May Clinic, Rochester,

VOL. 37, 1993


Minn.) for provision of some cultures used in the present study andD. Citron for helpful advice.

REFERENCES1. Appelbaum, P. C. 1987. Anaerobic infections: nonsporeformers,

p. 45-109. In B. B. Wentworth (coordinating ed.), Diagnosticprocedures for bacterial infections. American Public HealthAssociation, Washington, D.C.

2. Appelbaum, P. C., M. R. Jacobs, S. K. Spangler, and S.Yamabe. 1986. Comparative activity of P-lactamase inhibitorsYTR 830, clavulanate, and sulbactam combined with ,-lactamsagainst 3-lactamase-producing anaerobes. Antimicrob. AgentsChemother. 30:789-791.

3. Appelbaum, P. C., A. Philippon, M. R. Jacobs, S. K. Spangler,and L. Gutmann. 1990. Characterization of P-lactamases fromnon-Bacteroides fragilis group Bacteroides spp. belonging toseven species and their role in 1-lactam resistance. Antimicrob.Agents Chemother. 34:2169-2176.

4. Appelbaum, P. C., S. K. Spangler, and M. R. Jacobs. 1990.Evaluation of two methods for rapid testing for beta-lactamaseproduction in Bacteroides and Fusobactenum. Eur. J. Clin.Microbiol. Infect. Dis. 9:47-50.

5. Appelbaum, P. C., S. K. Spangler, and M. R. Jacobs. 1990.13-Lactamase production and susceptibilities to amoxicillin,amoxicillin-clavulanate, ticarcillin, ticarcillin-clavulanate, ce-foxitin, imipenem, and metronidazole of 320 non-Bacteroidesfragilis Bacteroides and 129 fusobacteria from 28 U.S. centers.Antimicrob. Agents Chemother. 34:1546-1550.

6. Appelbaum, P. C., S. K. Spangler, and M. R. Jacobs. 1991.Susceptibilities of 394 Bacteroidesfragilis, non-B. fragilis groupBacteroides species, and Fusobacterium species to newer anti-microbial agents. Antimicrob. Agents Chemother. 35:1214-1218.

7. Appelbaum, P. C., S. K. Spangler, and M. R. Jacobs. Suscepti-bility of 539 gram-positive and -negative anaerobes to newagents, including RP 59500, biapenem, trospectomycin andpiperacillin/tazobactam. J. Antimicrob. Chemother., in press.

8. Appelbaum, P. C., S. K. Spangler, G. A. Pankuch, A. Philippon,M. R. Jacobs, R. Shiman, E. J. C. Goldstein, and D. Citron.Submitted for publication.

9. Appelbaum, P. C., S. K. Spangler, R. Shiman, and M. R. Jacobs.1992. Susceptibilities of 540 anaerobic gram-negative bacilli toamoxicillin, amoxicillin-BRL 42715, amoxicillin-clavulanate,temafloxacin, and clindamycin. Antimicrob. Agents Chemo-ther. 36:1140-1143.

9a.Bandoh, K., K. Ueno, K. Watanabe, and N. Kato. 1993. Suscep-tibility patterns and resistance to imipenem in the Bacteroidesfragilis group species in Japan: 4-year study. Clin. Infect. Dis.16(Suppl. 4):S382-S386.

10. Bremm, K.-D., R. Endermann, and K. D. Metzger. 1992. Pro-gram Abstr. 32nd Intersci. Conf. Antimicrob. Agents Chemo-ther., abstr. 649.

11. Chow, A. W., V. Patten, and L. B. Guze. 1975. Susceptibility ofanaerobic bacteria to metronidazole: relative resistance of non-spore-forming gram-positive bacilli. J. Infect. Dis. 131:182-185.

12. Edson, R. S., J. E. Rosenblatt, D. T. Lee, and E. A. McVey.

1982. Recent experience with antimicrobial susceptibility ofanaerobic bacteria. Increasing resistance to penicillin. MayoClin. Proc. 57:737-741.

13. Endermann, R., and K.-D. Bremm. 1992. Program Abstr. 32ndIntersci. Conf. Antimicrob. Agents Chemother., abstr. 645.

14. Finegold, S. M., and W. L. George (ed.). 1989. Anaerobicinfections in humans. Academic Press, Inc., New York.

15. George, W. L., B. D. Kirby, V. L. Sutter, D. M. Citron, andS. M. Finegold. 1981. Gram-negative anaerobic bacilli: their rolein infection and patterns of susceptibility to antimicrobialagents. II. Little-known Fusobacterium species and miscella-neous genera. Rev. Infect. Dis. 3:599-626.

16. Goldstein, E. J. C., and D. Citron. 1985. Comparative activity ofthe quinolones against anaerobic bacteria isolated at communityhospitals. Antimicrob. Agents Chemother. 27:657-659.

17. Goldstein, E. J. C., and D. Citron. 1992. Comparative activity ofciprofloxacin, ofloxacin, sparfloxacin, temafloxacin, CI-960, CI-990, and Win 57273 against anaerobic bacteria. Antimicrob.Agents Chemother. 36:1158-1162.

18. Holdeman, L. V., and W. E. C. Moore (ed.). 1977. Anaerobiclaboratory manual, 4th ed. Virginia Polytechnic Institute andState University, Blacksburg.

19. Jacobs, M. R., S. K. Spangler, and P. C. Appelbaum. 1990.3-Lactamase production, j3-lactam sensitivity and resistance to

synergy with clavulanate of 737 Bacteroides fragilis grouporganisms from thirty-three US centres. J. Antimicrob.Chemother. 26:361-370.

20. Krasemann, C. 1992. Program Abstr. 32nd Intersci. Conf.Antimicrob. Agents Chemother., abstr. 644.

21. National Committee for Clinical Laboratory Standards. 1990.Methods for antimicrobial susceptibility testing of anaerobicbacteria, 2nd ed. Approved standard. NCCLS publication no.M11-A2. National Committee for Clinical Laboratory Stan-dards, Villanova, Pa.

22. Nord, C. E. 1986. Mechanisms of P-lactam resistance in anaer-obic bacteria. Rev. Infect. Dis. 8(Suppl. 5):S543-S548.

23. Petersen, U., K.-D. Bremm, A. Krebs, K. G. Metzger, T.Philipps, and T. Schenke. 1992. Program Abstr. 32nd Intersci.Conf. Antimicrob. Agents Chemother., abstr. 642.

24. Rolfe, R. D., and S. M. Finegold. 1982. Comparative in vitroactivity of ceftriaxone against anaerobic bacteria. Antimicrob.Agents Chemother. 22:338-341.

25. Shah, P. M., R. Enzensberger, 0. Glogau, and H. Knothe. 1987.Influence of oral ciprofloxacin or ofloxacin on the fecal flora ofhealthy volunteers. Am. J. Med. 82(Suppl. 4A):333-335.

26. Spera, R. V., Jr., M. H. Kaplan, and S. L. Allen. 1992.Clostridium sordellii bacteremia: case report and review. Clin.Infect. Dis. 15:950-954.

27. Summanen, P., E. J. Baron, D. M. Citron, C. A. Strong, H. M.Wexler, and S. M. Finegold. 1993. Wadsworth anaerobic bacte-riology manual, 5th ed. Star Publishing Co., Belmont, Calif.

28. Thurberg, B. E., B. G. Painter, J. A. Herrington, J. A. Federici,J. M. Remy, and M. L. Barbiero. 1992. Program Abstr. 32ndIntersci. Conf. Antimicrob. Agents Chemother., abstr. 643.

29. Ueno, K. (Gifu University). 1992. Personal communication.

1654 PANKUCH ET AL.

to ciprofloxacin, clindamycin, metronidazole, piperacillin,

Documents