Erratum to: Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

[This corrects the article DOI: 10.1186/s13017-016-0089-y.].

Clinical efficacy of tigecycline used as monotherapy or in combination regimens for complicated infections with documented involvement of multiresistant bacteria

INTRODUCTION

Tigecycline is an established treatment option for infections with multiresistant bacteria (MRB). It retains activity against many strains with limited susceptibility to other antibiotics. Efficacy and safety of tigecycline as monotherapy or in combination regimens were investigated in a prospective noninterventional study involving 1,025 severely ill patients in clinical routine at 137 German hospitals.

MATERIALS AND METHODS

Data on the full population have been published; our present analysis focuses on infections caused by MRB. The study population included patients with complicated infections, high disease severity (APACHE II > 15: 65 %) and high MRB prevalence. Most patients had comorbidities, including cardiovascular disease, renal insufficiency, and/or diabetes mellitus. Treatment success was defined as cure/improvement without requirement of further antibiotic therapy.

RESULTS

Pathogens isolated from 215 evaluable patients with documented MRB infections included 132 methicillin-resistant Staphylococcus aureus (MRSA), 42 vancomycin-resistant Enterococci (VRE) and 67 Gram-negative extended beta-lactamase (ESBL) producers. Of the MRB subpopulation, 140 patients received tigecycline monotherapy, 75 were treated with combination regimens. High overall clinical success rates were recorded for MRB infections treated with tigecycline alone (94 %) or in combinations (88 %); in detail intraabdominal infections (monotherapy: 90 %; combinations: 93 %), skin/soft tissue infections (93; 100 %), community-acquired pneumonia (100; 100 %), hospital-acquired pneumonia (94,7; 72,7 %), diabetic foot infections (89; 33 %), blood stream infections (100; 100 %) and multiple-site infections (92; 71 %).

CONCLUSIONS

Tigecycline achieved high clinical success rates in patients with documented infections involving MRB strains despite high disease severity. These results add to the evidence indicating that tigecycline is a valuable therapeutic option for complicated infections in severely ill patients with a high likelihood of multidrug-resistant pathogen involvement.

[Is monotherapy with β-lactam antibiotics still up to date? New aspects for treatment of severe infections]

Mortality of sepsis is still high. Crucial for therapeutic response are the early start of treatment as well as the choice of antibiotics or antibiotic combinations. β-lactam antibiotics with bactericidal mode of action are often recommended in guidelines. But this antibiotic class can trigger the immune system to a maximum by releasing cell wall components or exotoxins. This may lead to a worsening of the patient's clinical situation. In contrast, antibiotics with bacteriostatic action often inhibit bacterial protein synthesis with decrease of production of virulence factors and minimize release of cell wall components. The purpose of this review is to summarise the significance of some bacteriostatic antibiotics and to discuss whether a combination of bactericidal and bacteriostatic agents may improve the course of the illness.

Urinary tract infection in men

OBJECTIVE

To explore the prevalence and microbiology of urinary tract infection (UTI) in symptomatic men in a primary care setting and to determine the appropriateness of patient management of these conditions by the general practitioners.

METHODS

A cross-sectional survey was carried out matching documentation of symptoms and management with urine culture and results of susceptibility tests. All patients presenting with symptoms typical for a UTI in 36 teaching general practices in the area of Göttingen, Germany, were eligible for enrolment in the study. 15% (n = 90) of all patients were adult men. General practitioners (GPs) were instructed to manage patients as usual. Patient characteristics, dipstick tests and treatment were matched with results of urine cultures and susceptibility testing.

RESULTS

Men presenting with symptoms indicative of UTI were predominantly elderly (median age 61 years) and 41% had additional risk factors. Antibiotics were prescribed for 36%, but these were not well-targeted. Urine culture revealed UTI in 60%, of which half had low colony counts (23% of all patients) or multiple bacterial growth (7%); 40% had sterile urine. Dipstick tests proved unhelpful: leukocytes and nitrite had sensitivities of 54% and 38%, specificities of 55% and 84%, positive predictive values of 65% and 78% and negative predictive values of 44% and 46%, respectively. Resistance levels were 53% for amoxicillin and cefaclor, 28% for cefixim, 22% for ciprofloxacin, 34% for both trimethoprim as individual substance and the combination with sulfamethoxazole (cotrimoxazole) and 25% for nitrofurantoin.

CONCLUSION

Men with symptoms indicative of a UTI should not be treated empirically. A urine culture and antibiogram should be obtained before a treatment decision is made. A low-count UTI was common and should not be considered normal.

[Puerperal sepsis caused by streptococcus group A with a severe form of progression like "toxic shock-like syndrome"]

HISTORY AND CLINICAL FINDINGS

A previously healthy 32-year-old woman was admitted with shock symptoms 5 days after an uneventful home delivery. She developed a fever up to 39.5 degrees C during the days after delivery with sore throat, diarrhoea and muscle aches in all limbs. On physical examination there were swellings of the arms and lower legs as well as macular and vesicular erythrodermia, especially of the trunk.

INVESTIGATIONS

Abnormal laboratory findings were thrombocytopenia (20,000/microliters), increased serum concentrations of fibrin breakdown products (102 mg/dl) and of C-reactive protein (> 200 mg/dl), increased creatine kinase (5700 U/l), transaminases (GOT 220 U/l, GPT 52 U/l), creatinine (2.0 mg/dl) and urea (114 mg/dl). Streptococcus pyogenes was grown on blood culture and from vaginal smear. Sonography, echocardiography and radiological examinations failed to demonstrate a septic focus.

TREATMENT AND COURSE

Mechanical ventilation was required for 7 days because of respiratory failure and shock symptoms (toxic shock-like syndrome, TSLS). Penicillin G and tobramycin were given after the bacteriological diagnosis. Severe consumption coagulopathy was successfully treated with antithrombin III and platelet concentrates. After extubation she was found to have a flaccid tetraparesis, especially of the right and of the legs, due to soft-tissue necrosis and damage to peripheral nerves. An embolic occlusion of the right brachial artery 4 weeks after onset of the disease required upper-arm amputation.

CONCLUSION

One of the decisive factors for the prognosis of TSLS is early antibiotic treatment. The prodromal symptoms in this case underline the necessity of early recognition and treatment to prevent a full-blown picture of the syndrome.

Corynebacterium lipophiloflavum sp. nov. isolated from a patient with bacterial vaginosis

A unique coryneform bacterium was isolated from a patient with bacterial vaginosis. Chemotaxonomical investigations demonstrated that the unknown bacterium belonged to the genus Corynebacterium. The yellow-pigmented, slightly lipophilic, oxidative, urea-hydrolyzing bacterium could be phenotypically readily differentiated from the other members of the genus Corynebacterium. Comparative 16S rRNA gene analysis revealed that the bacterium represented a new subline within the genus Corynebacterium for which the name Corynebacterium lipophiloflavum sp. nov. is proposed. The type strain is CCUG 37336 (DSM 44291).

[Cat scratch disease. Bartonella henselae antibodies and DNA detection in regional lymphadenopathy]

HISTORY AND CLINICAL FINDINGS

Two hard, pressure-sensitive nodules developed in the lower jaw of a 22-year-old woman. After a dental cause had been excluded, she was treated for suspected tonsillitis with Ceftibuten. Erythrocyte sedimentation rate was increased to 18 mm in the first hour. There were no other significant biochemical findings and fine-needle biopsy of one of the nodules showed nonspecific inflammatory reaction.

INVESTIGATIONS

Sonography revealed two lymph nodes, 7 and 22 mm in diameter. Suspected cat scratch disease was confirmed by immunofluorescence with Bartonella (Rochalimaea) henselae and quintana antigens.

TREATMENT AND COURSE

After a course of Clarithromycin (250 mg twice daily) for 6 weeks the lymph nodes had shrunk and the overlying skin was thin and discoloured brown. One node was incised and drained and the material examined. Microbiology was negative, but DNA sequencing confirmed Bartonella henselae. As a consequence, Rifampicin was given for 2 months (600 mg daily). Wound healing was very slow and the scar had regressed little after 9 months.

Sulbactam in combination with mezlocillin, piperacillin or cefotaxime: clinical and bacteriological findings in the treatment of serious bacterial infections

An open, multicentre study was performed in hospital in-patients at a total of 12 German hospitals to investigate the efficacy and tolerability of sulbactam combined with mezlocillin, piperacillin or cefotaxime in severe bacterial infections. A total of 155 patients were recruited into the study, of whom 48 were suffering from respiratory tract infections, 66 from intra-abdominal infections, 34 from skin/soft tissue infections including postoperative wound infections, and five from complicated urinary tract infections. Fifty-five patients intravenously received 4 g mezlocillin and 1 g sulbactam three times daily, 52 received 4 g piperacillin and 1 g sulbactam three times daily, and 48 received 2 g cefotaxime and 1 g sulbactam three times daily. The antibiotic and sulbactam combination was administered in all cases by rapid intravenous infusion of both components together, over 20 min. The mean duration of treatment was 20 days. The criteria used to define the outcome of treatment as successful were clinical cure (complete disappearance of the signs and symptoms of infection seen before the start of treatment) or improvement (appreciable diminution or partial resolution of the initial signs and symptoms, no further antibiotic therapy required) and the elimination of the organisms isolated before the start of the study. Of the 153 clinically evaluable patient, 141 (92%) were classed as responders (a cure was obtained in 98 cases and improvement in 43 cases). No response to the study medication was seen in 12 patients (7.8%). The response rates of the combined antibiotic-sulbactam preparations were 91% for mezlocillin/sulbactam, 92% for piperacillin/sulbactam, and 93% for cefotaxime/sulbactam. These response rates are almost identical. A total of 106 patients (68.4%) were bacteriologically evaluable; a total of 192 bacterial organisms were identified in these patients before the start of treatment. Mixed infection was present in 55 patients. The causative organism initially isolated was eliminated in 96 patients (90%), accounting for 180 of 192 strains (94%). Persistence of the causative organism (12 strains) was seen in eight patients (7.6%). Superinfection (four strains) was seen in two patients (1.9%). The study medication was well tolerated; adverse drug effects were seen in only five patients (3.3%). Treatment was discontinued in one patient because of the adverse effect (exanthema). The combination of the beta-lactamase inhibitor sulbactam and a ureidopenicillin or cefotaxime was highly effiacious in patients with severe bacterial infections investigated in this study. The availability of sulbactam as a single-agent preparation opens up new avenues for flexible and cost-effective antibiotic therapy and is a valuable contribution to the control of bacterial resistance.

[Gardnerella vaginalis: transport, microscopy, testing resistance]

G. vaginalis is an important pathogen in the aetiology of bacterial vaginosis. Therefore, we investigated the influence of transport systems in isolation, a scoring system for Gram stains, and susceptibility to antimicrobial agents. The comparison between a simple (Transwab) and a sophisticated (Port-A-Cul) system showed no differences with regard to for instance Enterococcus faecalis or Escherichia coli; however, isolation of G. vaginalis, a fastidious microorganism, was significantly higher (alpha < 0.0001) in Port-A-Cul. There was a strong correlation (97.5%) using the scoring system indicating bacterial vaginosis and isolation of G. vaginalis. The minimal inhibitory concentrations (MIC) of metronidazole for 60 strains of G. vaginalis were higher than 32 mg/l, some strains showing heteroresistance. This phenomenon may be an explanation for treatment failures. Clindamycin and erythromycin were much more active, with MIC's between 0.016 and 0.19 mg/l, in-vitro development of resistance being slower for clindamycin than for erythromycin.

CONCLUSIONS

(I) for isolation of G. vaginalis, a sophisticated transport system is mandatory; (II) a scoring system for Gram staining is helpful in diagnosis of bacterial vaginosis; (III) in patients with metronidazole treatment failures, clindamycin should be used.

[Incidence and importance of Clostridium difficile in patients treated with antibacterial therapy or perioperative preventive cefoxitin administration]

Clostridium difficile and/or toxin B were isolated from the faeces of 3 (1.6%) of 184 patients within the first two days of hospitalisation in the University of Tübingen, Gynaecological Clinic. With following stool samples from a total of 117 patients the isolation rate of C. difficile was examined in relation to the treatment with antibiotics. From the first group of 61 patients, who had had gynaecological operations and were not treated with any antibiotic, the isolation rate of C. difficile rose statistically but not significantly from 0% at the time of admission up to 3.3% during hospitalisation. Amongst the second group of 17 patients, who had had gynaecological operations and were treated with various antibiotics for at least three days, the isolation rate was also found to rise insignificantly from 0 to 11.8% (p < 0.1). The third group of 33 patients, who had had gynaecological operations and perioperative prophylaxis with cefoxitin (one to three doses 2 g each), the isolation rate rose significantly from 0 to 12.1% (p < 0.05). The result of this study shows that the bacterial flora of the gut was probably altered even after a very brief application of cefoxitin. In two environmental examinations on the wards of the patients of this study, C. difficile was not isolated in any case.

Microbic superinfection in relapse of inflammatory bowel disease

To assess the association between symptomatic relapse of inflammatory bowel disease (IBD) and superinfection with enteropathogenic microorganisms, we determined prospectively the incidence of infections with enteropathogenic bacteria, protozoa, and helminths in patients with confirmed longstanding IBD. Sixty-four patients with IBD (49 with Crohn's disease [CD] and 15 with ulcerative colitis [UC]) were consecutively enrolled in the study when relapse occurred. Multiple biopsies for histological and microbiological investigations were taken from all patients who were evaluated by colonoscopy. Parallel stool specimens were investigated for the presence of enteropathogenic bacteria, protozoa, and helminths. In six patients, we detected Clostridium difficile or toxin B (five CD, one UC), in one patient Campylobacter jejuni (CD), and in another patient Salmonella typhimurium (UC). Enteropathogenic Escherichia coli were isolated from three patients. Investigation of biopsies for Mycobacteria, microscopic examination of stool samples for helminths, and immunofluorescence for chlamydia were negative in all patients. In summary, as we found enteropathogenic microorganisms so infrequently in patients with relapse of IBD, despite intensive microbiological screening by tissue sampling for detection of gut adherent bacteria, we believe that microorganisms play only a minor role in the exacerbation of IBD.

Isolation of Ewingella americana from a patient with conjunctivitis

Ewingella americana (family Enterobacteriaceae) was isolated separately from both eyes of a 30-year-old woman. Clinical signs and symptoms included adhesive eyelids, itching and edematous upper and lower lids. Therapy with amoxicillin-clavulanate resulted in the relief of symptoms. Ewingella americana can be isolated worldwide, but seems to be a rare pathogen.

[Sulbactam in combination with mezlocillin, piperacillin or cefotaxime. Clinical and bacteriological results in the treatment of severe bacterial infections]

An open multicenter study on inpatients of 12 german hospitals was performed to investigate efficacy and safety of sulbactam in combination with mezlocillin, piperacillin or cefotaxim in severe bacterial infections. In total 155 patients were enrolled. The following infections were diagnosed: 48 lower respiratory tract infections, 66 intraabdominal infections, 34 skin/soft tissue infections including post operative wound infections and 5 complicated urinary tract infections. 55 patients received 3 daily doses of 4 g mezlocillin + 1 g sulbactam, 52 patients received 3 daily doses of 4 g piperacillin + 1 g sulbactam and 48 patients received 3 daily doses of 2 g cefotaxim + 1 g sulbactam. Antibiotics and sulbactam were administered concomitantly via intravenous short infusion. Mean duration of therapy was 8 days. Endpoints for assessment of therapeutic efficacy were cure (complete resolution of pretreatment signs and symptoms of the infection) or improvement (marked reduction or partial disappearance or pretreatment signs and symptoms, no further antibiotic therapy required) as well as eradication of pretreatment pathogens. 141 (92%) of 153 evaluable patients were successfully treated (98 cures and 43 improvements), therapy failed in 12 patients (7.8%). Success rates of the 3 sulbactam combinations were almost identical: 91% for mezlocillin/sulbactam, 92% for piperacillin/sulbactam and 93% for cefotaxim/sulbactam. 106 patients (68.4%) were also bacteriologically evaluable. In these patients 192 bacterial pathogens were isolated prior to study therapy, 55 patients had mixed infections. In 96 patients (90%) pretreatment pathogens were eradicated (180 strains = 94%).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative in vitro activity of cefpodoxime against anaerobes other than Bacteroides fragilis

To assess the in vitro activity of cefpodoxime against anaerobic respiratory tract and oropharyngeal pathogens 77 strains belonging to 18 gram-negative and 7 gram-positive species were studied by means of agar dilution tests. For comparison cefuroxime, amoxicillin, amoxicillin + clavulanic acid and clindamycin were also tested. Cefpodoxime was found to be active at concentrations of less than or equal to 0.125 mg/l against Prevotella oralis, Prevotella buccalis, Prevotella bivia, Porphyromonas asaccharolytica, Bacteroides corporis, Bacteroides gracilis, Fusobacterium necrophorum, Fusobacterium naviforme and Propionibacterium acnes. Prevotella oris, Prevotella buccae, Fusobacterium nucleatum, Peptostreptococcus asaccharolyticus, and Ruminococcus bromii were inhibited at concentrations of less than or equal to 1 mg/l and Prevotella denticola, Prevotella melaninogenica, Prevotella intermedia, Porphyromonas gingivalis, Bacteroides pneumosintes, and Peptostreptococcus micros at concentrations of less than or equal to 4 mg/l. Strains of Veillonella parvula were inhibited by cefpodoxime at 0.25-8 mg/l, and single strains of Peptostreptococcus anaerobius and Peptostreptococcus magnus showed MICs of 32 and 64 mg/l, respectively. The results obtained warrant the use of cefpodoxime in therapy of anaerobic and mixed aerobic-anaerobic infections of the upper and lower respiratory tract and similar infections not involving Bacteroides fragilis.

Effect of daptomycin, metronidazole and mezlocillin combinations on mixed bacterial cultures involving facultative and anaerobic bacteria

The in vitro activities of different daptomycin concentrations in combination with metronidazole (4 mg/l) or/and mezlocillin (8 mg/l) were investigated on mixed bacterial cultures involving gram-positive facultative cocci. Bacteroides fragilis group strains and Escherichia coli. When Streptococcus faecalis alone or together with E. coli was cultured with B. thetaiotaomicron the colony counts of the latter were 4 log units higher after incubation in the presence of daptomycin and metronidazole than when it was cultured alone. After the addition of mezlocillin, this effect disappeared and all 3 strains were killed. When the same antibiotic combinations were used in the presence of beta-lactamase producing Staphylococcus aureus, the activity of mezlocillin was decreased significantly. The colony counts of the co-cultured B. thetaiotaomicron and E. coli proved to be 2 log and 6 log higher, respectively, than those observed after they were cultured alone. The antimicrobial susceptibilities of the clinical isolates tested here in mixed cultures of up to 3 strains were modified significantly by interactions between the strains and the antibiotics used.

Efficacy of sulbactam in an in vitro model of mixed aerobic/anaerobic infections

Bacterial interactions in mixed infections may interfere with antimicrobial therapy. The in-vitro efficacy of ampicillin alone, combination sulbactam/ampicillin, and metronidazole was studied. Strains of Bacteroides fragilis, Escherichia coli, and Enterococcus faecalis, alone and in association, were tested by means of a broth dilution method. Minimal bactericidal concentrations (MBC) of ampicillin for B. fragilis 74 in association with E. coli 68 were up to 16-fold higher than for B. fragilis 74 alone (256 compared to 16 mg/l), but only 2-fold higher for sulbactam (5 mg/l)/ampicillin (0.5 and 0.25 g/l). Association of B. fragilis 45 and E. faecalis 186 increased ampicillin MBC of E. faecalis 186 from 2 to 16 mg/l, but the combination sulbactam/ampicillin restored activity of ampicillin. In association with E. faecalis, metronidazole MBCs of B. fragilis increased up to 64-fold. Strains of E. faecalis and E. coli were able to destroy 10 mg/l metronidazole within 8 to 20 h. The present experiments demonstrated effectiveness of sulbactam/ampicillin to inhibit beta-lactamases of associated pathogens. Destruction of metronidazole by E. faecalis lends additional support to the use of the combination in aerobic/anaerobic infections including E. faecalis.

[Rocky Mountain spotted fever]

After returning from a holiday in the USA a 24-year-old man fell ill with diarrhoea, high fever and marked rash including the palms of the hands and soles of the feet. When a history of a tick bite in the USA was elicited, a rickettsial infection was suspected. Treatment with doxycycline, 100 mg twice daily, was instituted finally and the fever slowly resolved. The patient became completely well again within four weeks. Serological tests confirmed the diagnosis of Rocky Mountain spotted fever.

Efficacy of clavulanate-potentiated antibiotics against Bacteroides species and artificially associated cultures of aerobes and anaerobes

Clavulanic acid is known to potentiate the activity of amoxycillin and ticarcillin against beta-lactamase-producing Bacteroides species. In order to assess the usefulness of the clavulanate antibiotics in mixed infections with aerobes and anaerobes, artificially associated cultures of clinically significant Bacteroides species and facultative anaerobes (Escherichia coli, Klebsiella pneumoniae, Haemophilus influenzae, Enterococcus faecalis, Staphylococcus spp. and Streptococcus spp.) were tested. The minimal bactericidal concentrations (MBC) of amoxycillin and ticarcillin, singly and in combination with clavulanate, were determined for the individual species in the associated culture and for the associated culture as a whole. In the absence of clavulanate, association experiments showed that the MBCs of susceptible strains increased in the presence of beta-lactamase-producing species, whereas the addition of clavulanate to the test systems led to MBCs which were mostly comparable to values as determined in single strain testing.

[The role of coagulase negative staphylococci in mixed infections: association testing as an in vitro model]

Infections due to coagulase negative staphylococci (CNS) are of growing concern mainly in patients hospitalized in intensive care units (ICU). The ability of CNS to adhere and to grow on plastic devices and resistance to many antibiotics, including oxacillin, contributes to their pathogenicity. Using the computer assisted system of the Medical Microbiology Department, the incidences of different pathogens and the coincidence of CNS with other bacteria were evaluated in a surgical department. Staphylococcus aureus revealed to be the predominant pathogen; however, CNS showed an increasing incidence in wound specimens and blood cultures of patients on the ICU. Coincidence of CNS with S. aureus and the nine most frequent species of gram negative bacteria could be shown in 6%. To investigate the influence of beta-lactamases produced by CNS in mixed infections, association experiments were performed. Association means a controlled growth of two or even more bacteria in a susceptibility testing system, either a broth dilution method or an automated broth disk elution method (Cobas Bact). The association experiments showed a significant increase of amoxicillin MIC's of the pathogen associated with CNS. Addition of clavulanic acid restored activity of amoxicillin. It could be shown that in mixed infections CNS may contribute to the failure of antibiotic regimens by production of beta-lactamases.

Association experiments with aerobic and anaerobic pathogens: a model of in-vitro susceptibility testing in mixed infections. Activity of enoxacin, clindamycin, and metronidazole

In infections of polymicrobial etiology, it seems mandatory to combine an antibiotic with marginal activity against anaerobes with an anti-anaerobic drug, e.g. metronidazole or clindamycin. We investigated the effect of associations of anaerobic and facultatively anaerobic pathogens on MBCs of enoxacin, clindamycin, metronidazole, and combinations of enoxacin plus clindamycin or metronidazole. Single testing, and associations of Bacteroides fragilis with Escherichia coli or Enterococcus faecalis revealed MBCs of 64 mg/l for enoxacin. However, investigating metronidazole, MBCs for B. fragilis increased from 0.5-1 mg/l to 2-4 mg/l in association with E. coli. The combination of enoxacin with metronidazole restored MBCs of 0.5 and 1 mg/l for the B. fragilis strains. B. fragilis associated with E. faecalis showed MBCs of 2 to 64 mg/l for metronidazole, an increase of up to 64-fold. The enoxacin MBCs for E. coli in association with B. fragilis were up to eight-fold higher than for E. coli alone (2 mg/l compared to 0.25 mg/l). Association of E. coli with E. faecalis and B. fragilis showed a low to moderate increase for MBCs of E. coli when enoxacin was tested alone or in combination with metronidazole or clindamycin. In contrast, MBCs for E. faecalis did not change significantly with any of the associations or combinations tested. It is evident that in vitro antimicrobial susceptibility of associations of pathogens can be modified by interactions between strains, and/or antimicrobials.

GasPak Plus versus Anaerocult A--two carbon dioxide/hydrogen systems for cultivation of anaerobes

Two disposable carbon dioxide/hydrogen gas-generating systems (GasPak Plus and Anaerocult A) were compared by assessing growth of obligate anaerobic bacteria. Eighty strains representing 28 species of anaerobic bacteria commonly occurring at various body sites were seeded onto 4 brain heart chocolate agar plates using a spiral plater; and 1 plate each was subsequently incubated in 2 Anaerocult A and 2 GasPak Plus systems. Bacterial growth was expressed as colony-forming units per ml (CFU/ml), reproducibility of the seeding procedure was checked, and the potential interference of H2S-producing bacteria with operation of the carbon dioxide/hydrogen systems was investigated. The presence of H2S only inhibited bacterial growth in the case of Peptostreptococcus asaccharolyticus - an effect observed in both systems. Reproducibility of the seeding procedure using the spiral plater was within acceptable range. Differences between the systems were not apparent when comparing total CFU/ml of a given species and the systems therefore provide equally effective environments for incubation of anaerobic bacteria. In both systems, however, growth varied from one species or strain to another. In mixed infections, detection of certain species of anaerobes may therefore be difficult using either system.

A multicenter international study on the activity of sulbactam/ampicillin, ampicillin, and cefoxitin against anaerobic bacteria and introduction of a new model of susceptibility testing in mixed infections

Susceptibility of anaerobic clinical isolates from the United States, Canada, and Germany to sulbactam/ampicillin (1 + 2) (SBT/AMP), ampicillin alone (AMP), and cefoxitin (CFX) was determined with a standard agar dilution test. The isolates included 192 strains of Bacteroides fragilis, 132 strains of other Bacteroides spp., and 19 strains of Clostridium spp. Against all species tested, SBT/AMP was more active than AMP or CFX. Results obtained by a new model of associative susceptibility testing indicated that susceptibility testing of single pathogens from polymicrobial infections is not necessarily reflective of the susceptibility of the pathogens at the site of infection. The results suggest that sulbactam is effective in associations of pathogens producing beta-lactamases of Richmond-Sykes types II-V and beta-lactamases of anaerobic bacteria.

[Susceptibility of clinically important Bacteroides species against enoxacin-metronidazole and enoxacin-clindamycin combinations]

To assess the activity of enoxacin, clindamycin and metronidazole, MICs of clinical isolates of saccharolytic intestinal Bacteroides spp. were determined, using the agar dilution method according to NCCLS guidelines. Checkerboard titrations of enoxacin-metronidazole and enoxacin-clindamycin were done on Wilkins-Chalgren agar; inoculation, incubation and reading of plates were as for determination of MICs. Metronidazole MIC 90s for Bacteroides fragilis (23 strains) and Bacteroides thetaiotaomicron (23 strains) were 0.5 mg/l, clindamycin MIC 90 for B. fragilis was 1 mg/l, and for B. thetaiotaomicron 8 mg/l, whereas enoxacin MIC 90 values were 16 mg/l and 64 mg/l, respectively. The evaluation of the inhibitory effects of the combination enoxacin-metronidazole for B. fragilis showed additional effects in eleven strains, indifference in seven strains and antagonism in one. The figures for B. thetaiotaomicron showed addition in five strains, indifference in 17 strains, antagonism in one. For B. fragilis the combination enoxacin-clindamycin showed addition in ten strains, indifference in six, and antagonism in one; for B. thetaiotaomicron synergism in one strain, addition in four strains, indifference in 17 strains. In conclusion, the absence of antagonism and the overall preponderance of additional and indifferent effects warrant the use of enoxacin in combination with metronidazole or clindamycin in clinical trials of treatment of anaerobic-aerobic mixed infections.