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PubMed1997

A review of the in vitro activity of meropenem and comparative antimicrobial agents tested against 30,254 aerobic and anaerobic pathogens isolated world wide.

The in vitro activity of meropenem (formerly SM-7738), a new carbapenem, was compared with that of imipenem and five other broad-spectrum antimicrobials (ceftazidime, cefotaxime, piperacillin, piperacillin/tazobactam, and ciprofloxacin) against 30,254 clinically significant pathogens isolated in nine countries worldwide. Overall, the carbapenems, meropenem and imipenem, were the most active drugs. Meropenem was four- to 64-fold more active than imipenem against Gram-negative bacteria, including the Enterobacteriaceae, Pseudomonas aeruginosa, Burkholderia cepacia, Haemophilus influenzae, and Neisseria meningitidis. Meropenem was also quite active against ceftazidime-resistant strains of Enterobacteriaceae, inhibiting 87.5 to 100% at < or = 4 micrograms/ml. In contrast, imipenem was four- to eight-fold more active than meropenem against Gram-positive species, including methicillin-susceptible strains of Staphylococcus aureus and Staphylococcus epidermidis, Streptococcus pneumoniae, and Enterococcus faecalis. Among the anaerobes, strains resistant to meropenem or imipenem were encountered very rarely. These extensive data provide additional in vitro support for the clinical use of meropenem as a broad spectrum antimicrobial agent active against key pathogenic species of bacteria.

Anti-Bacterial Agents↗

PubMed2005

Meropenem versus imipenem-cilastatin for the treatment of hospitalized patients with complicated skin and skin structure infections: results of a multicenter, randomized, double-blind comparative study.

BACKGROUND: Meropenem, a broad-spectrum carbapenem with potent in vitro activity, is postulated to be an effective monotherapy for the treatment of complicated skin and skin structure infections (cSSSI). METHODS: This multicenter, international, double-blind, randomized, prospective study of hospitalized patients with cSSSI evaluated the efficacy, safety, and tolerability of meropenem (500 mg IV q8h) versus imipenem-cilastatin (500 mg IV q8h). The primary efficacy endpoint was clinical outcome at follow-up in the clinically evaluable (CE) and modified intent-to-treat populations (MITT; patients who met eligibility criteria and received at least one dose of study drug). The study aimed to demonstrate non-inferiority (delta of 10%, 95% confidence intervals) in clinical response in the CE population. Clinical responses for all pathogens at follow-up were assessed in the fully evaluable population (CE population with baseline pathogen and follow-up cultures). RESULTS: In total, 1,076 patients were enrolled. Of these, 692 patients comprised the MITT population (334 and 358 patients randomized to meropenem and imipenem-cilastatin, respectively) and 548 the CE population (261 and 287 patients randomized to meropenem and imipenem-cilastatin, respectively). Cure rates were 86.2% (meropenem) and 82.9% (imipenemcilastatin; 95% CI, -2.8, 9.3) in the CE population and 73.1% (meropenem) and 74.9% (imipenem-cilastatin; 95% CI, -8.4, 4.7) in the MITT population. The frequencies of adverse events and drug-related adverse events were similar between treatment groups. CONCLUSION: In one of the largest studies conducted to date of hospitalized patients with cSSSI, meropenem, 500 mg IV q8h had comparable safety and efficacy to imipenem-cilastatin, 500 mg IV q8h.

Adolescent↗

PubMed1997

Stability of meropenem in intravenous solutions.

The stability of meropenem in various i.v. fluids stored in various containers for i.v. use was studied. Solutions of meropenem were prepared in a variety of i.v. diluents in polyvinyl chloride (PVC) bags, glass vials, and commercial easy-to-prepare infusion systems. Solutions for storage in PVC bags were prepared with meropenem concentrations of 1 and 20 mg/mL; in glass vials, 2.5 and 50 mg/mL; and in commercial easy-to-prepare infusion systems, 2.5 and 20 mg/mL (Baxter Minibag Plus system) and 1, 5, and 20 mg/mL (ADD-Vantage system, Abbott). The solutions were stored for up to 48 hours at 4-5 or 21-26 degrees C. Meropenem concentrations were determined by high-performance liquid chromatography. The stability of meropenem was influenced by the drug concentration; the drug was stable for a longer time in the 1-mg/mL solution than in the 20- and 50-mg/mL solutions. Stability was also influenced by storage temperature; the drug was stable for a longer time in solutions stored at 4-5 degrees C than in solutions stored at 21-26 degrees C. Meropenem was stable for the longest time in sterile water for injection and in 0.9% sodium chloride injection. The stability of meropenem in solutions in PVC bags, glass vials, Baxter Minibag Plus containers, and ADD-Vantage bags was influenced by the i.v. fluid used to reconstitute the drug, the concentration of the final solution, and the storage temperature.

Chromatography, High Pressure Liquid↗

PubMed2004

Stability of meropenem in polyvinyl chloride bags and an elastomeric infusion device.

PURPOSE: The stability of meropenem in i.v. solutions stored in polyvinyl chloride (PVC) bags and an elastomeric infusion device at concentrations commonly used in home care was studied. METHODS: Vials of meropenem were reconstituted with sterile water for injection and mixed with 0.9% sodium chloride injection (NS) to yield concentrations of 4, 10, and 20 mg/mL. Six replicate solutions were prepared in PVC containers and six in the Homepump ECLIPSE elastomeric infusion device. All solutions were stored at an average temperature of 5 degrees C and sampled immediately after preparation and at intervals up to 120 hours (five days); the 4-mg/mL solution was also sampled at 144 and 168 hours (seven days). Samples were assayed for meropenem concentration by stability-indicating high-performance liquid chromatography. RESULTS: All solutions of meropenem retained over 90% of the initial drug concentration at five days. The 4-mg/mL solutions retained over 93% of the initial concentration at seven days. The rate of meropenem decay did not differ significantly between PVC and elastomeric infusion containers for the 4- and 20-mg/mL solutions; however, there was a difference for the 10-mg/mL solutions. CONCLUSION: Meropenem 4 mg/mL in NS was stable for at least seven days in PVC bags and elastomeric infusion containers when stored at 5 degrees C, and meropenem 10 and 20 mg/mL in NS was stable for at least five days in both containers at 5 degrees C.

Chromatography, High Pressure Liquid↗

PubMed1993

Antibacterial activity of meropenem and selected comparative agents against anaerobic bacteria at seven North American centers.

The antibacterial activity of meropenem and comparative agents against approximately 1,000 anaerobes was determined using the disk dilution methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The organisms represented 27 species of six genera and included the most common pathogens. Meropenem and imipenem were the most active drugs and were comparable in overall activity, generally exhibiting an MIC90 of < or = 1 micrograms/mL. In contrast, the MICs of cefoxitin, clindamycin, and metronidazole were 32, 16, and 2 micrograms/mL, respectively. Meropenem was two- to fourfold more active than imipenem against selected Bacteroides species, Clostridium species, and Fusobacterium species. At a concentration of 1 microgram/mL, meropenem was more active than imipenem against cefoxitin-resistant Bacteroides fragilis or Bacteroides thetaiotaomicron. At a concentration of < or = 0.5 micrograms/mL, meropenem was more active than imipenem against clindamycin-resistant Bacteroides distasonis. At a concentration of 2 micrograms/mL, meropenem was more active than imipenem against cefoxitin-resistant or clindamycin-resistant Clostridium difficile. Thus, meropenem's high potency and broad-spectrum activity against common, rare, and drug-resistant anaerobes confirms its utility in the treatment of mixed anaerobic and aerobic infections.

Anti-Bacterial Agents↗

PubMed1995

A multicenter comparative study of meropenem and imipenem/cilastatin in the treatment of complicated urinary tract infections in hospitalized patients.

The safety and efficacy of meropenem and imipenem/cilastatin were compared in the treatment of hospitalized patients with complicated urinary tract infections (UTIs) in a prospective, multicenter, open, parallel-group trial. Patients were randomized to receive 500-mg intravenous doses of either meropenem every 8 hours (n = 116) or imipenem/cilastatin every 6 hours (n = 119). Data from 95 patients given meropenem and 82 patients given imipenem/cilastatin were included in the evaluation of efficacy. Meropenem produced satisfactory clinical and bacteriologic responses in 99% and 90% of cases, respectively. These results were similar to those obtained with imipenem/cilastatin, which produced clinical improvement in 99% of cases and bacteriologic improvement in 81%. Two patients given meropenem and five patients given imipenem/cilastatin developed superinfections. The rate of relapse was similar in the two groups. Patients who received meropenem had fewer drug-related adverse reactions than did recipients of imipenem/cilastatin (8% vs. 19%). The results of this study demonstrate that meropenem is a safe and effective alternative to imipenem/cilastatin in the treatment of hospitalized patients with complicated UTIs.

Bacteria↗

PubMed1989

Bactericidal activity of meropenem against Pseudomonas aeruginosa.

Ten strains of Pseudomonas aeruginosa that were susceptible to imipenem (MICs 2 mg/l) were exposed to a new parenteral carbapenem, meropenem (MIC 0.25 mg/l). Kinetic turbidometry showed that, as with other beta-lactam antibiotics, there was a prelytic increase in the culture OD following exposure to meropenem. The maximal value of the prelytic increase in the OD was higher for meropenem than for imipenem at concentrations 0.5, 1, 2, 4 and 8 x MIC. This corresponded to the formation of short filaments during exposure to low concentrations of meropenem. These filaments remained viable for 1-2 h, according to the drug concentration. For this reason, the killing began later with meropenem than with imipenem. After this delay, the killing rate for meropenem was the same as with imipenem, but occurred with lower concentrations of meropenem.

Carbapenems↗

PubMed1989

Meropenem: activity against resistant gram-negative bacteria and interactions with beta-lactamases.

The activity of meropenem, a new carbapenem, was determined against 82 Gram-negative bacteria in agar dilution tests. Many of these isolates were resistant to one or more beta-lactam antibiotics and the mechanisms responsible for the resistance had been characterized. The production of beta-lactamases had little influence on susceptibility to either meropenem or imipenem except in tests with Aeromonas hydrophila and Pseudomonas (Xanthomonas) maltophilia. These species produced metalloenzymes capable of hydrolyzing the carbapenems, and strains expressing high levels of these enzymes were resistant to both meropenem and imipenem. Clinical isolates of P. aeruginosa that had developed resistance to imipenem during therapy with the drug were two- to 32-fold less susceptible to meropenem than the corresponding pretreatment isolates. Alterations in outer membrane proteins were associated with this change in susceptibility to the carbapenems. Meropenem was a less potent inducer of Class I beta-lactamases than imipenem but was still a better inducer than ceftazidime or piperacillin. Overall, meropenem showed excellent activity against bacteria producing a variety of beta-lactamases, but cross-resistance between meropenem and imipenem due to enzymatic and non-enzymatic mechanisms did occur.

Carbapenems↗

PubMed1989

Development of a meropenem susceptibility disc: drug content, preliminary interpretive and quality control criteria and potency bioassay.

Laboratory studies were conducted to develop an appropriate susceptibility disc for meropenem. Laboratory-prepared paper discs containing 5, 10, and 20 micrograms of meropenem were investigated. Agar dilution MICs and agar disc diffusion tests were performed with 367 rapidly growing clinical isolates by methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). Agar disc diffusion tests with 10 micrograms meropenem discs acceptably defined organisms as susceptible or resistant. The preliminary interpretive zone size criteria for 10 micrograms meropenem discs were: susceptible, greater than or equal to 14 mm, and resistant, less than or equal to 10 mm, by application of the NCCLS imipenem MIC interpretive susceptible and resistant breakpoints to the meropenem data. A total of 270 agar disc diffusion assays were performed with each of four ATCC reference strains, using prototype discs (Becton Dickinson (BBL] containing 10 micrograms meropenem. The preliminary quality control limits for agar disc diffusion tests with these discs are: Escherichia coli ATCC 25922, 28-32 mm; Pseudomonas aeruginosa ATCC 27853, 26-31 mm; Staphylococcus aureus ATCC 25923, 33-39 mm; and Enterococcus faecalis ATCC 29212, 19-23 mm. Further studies are necessary to re-evaluate both the preliminary interpretive and quality control criteria before definitive limits can be established. A reproducible, large plate bioassay with Enterococcus faecalis ATCC 29212 was developed to monitor meropenem disc potency.

Bacteria↗

PubMed1989

Safety evaluation of meropenem in animals: studies on the kidney.

The effect of meropenem on animal kidneys has been assessed in rats (5 of each sex/group), rabbits (3 of each sex/group) and monkeys (3 of each sex/group) in comparative iv studies with ceftazidime, cefotaxime, cephaloridine and imipenem (without cilastatin). Diarrhoea occurred in rabbits and monkeys dosed with imipenem or meropenem. Emesis occurred only after the administration of imipenem to monkeys. After 14 days administration to rats evidence of nephrotoxicity was seen only in males dosed with cephaloridine (850 mg/kg); no changes were seen with ceftazidime, cefotaxime or meropenem (all at 1000 mg/kg). Four days after a single dose to rabbits renal tubular necrosis was seen in all animals receiving imipenem (150 mg/kg) and cephaloridine (250 mg/kg). Minimal histopathological changes to the kidneys were seen with cefotaxime, ceftazidime and meropenem (all at 400 mg/kg). After seven days' administration to cynomolgus monkeys imipenem (180 mg/kg) caused moderate to severe tubular necrosis. No tubular damage was seen with meropenem at 180 mg/kg or with cefotaxime or ceftazidime (both at 500 mg/kg). At 500 mg/kg meropenem caused mild tubular regeneration and/or fat accumulation in 3/6 animals, with mild tubular necrosis in one of these. The data from these three species indicate that meropenem has a low nephrotoxic potential in these animal models.

Animals↗

PubMed1995

Meropenem versus imipenem/cilastatin in the treatment of intra-abdominal infections.

In order to compare the clinical and microbiological efficacy and safety of meropenem with imipenem/cilastatin, 249 patients with intra-abdominal infections participated in an open randomised comparative multicentre trial. Seventy-five men and 57 women (mean age 51 years) were enrolled in the meropenem group and 67 men and 50 women (mean age 52 years) in the imipenem/cilastatin group. The patients received either meropenem, 500 mg q 8 h, or imipenem/cilastatin, 500 mg/500 mg q 8 h by intravenous infusion for up to 17 days (mean 5 days). Ninety-seven of 99 patients (98%) receiving meropenem were clinically cured while 86 of 90 patients (96%) in the imipenem/cilastatin group were clinically cured. The microbiological response was satisfactory in 89 of 94 evaluable patients (95%) receiving meropenem and in 78 of 81 evaluable patients (96%) receiving imipenem/cilastatin. There was no significant difference in clinical and microbiological efficacy between the two treatment groups. Adverse reactions were noted in 26 patients receiving meropenem and in 36 patients receiving imipenem/cilastatin. The present study shows that meropenem is effective and well tolerated in the treatment of intra-abdominal infections.

APACHE↗

PubMed1995

A compilation of meropenem tissue distribution data.

Meropenem body fluid and tissue concentration data from both published studies and samples obtained during efficacy evaluation have been compiled and presented according to a consistent format to facilitate comparison. The concentration data have been compared with the mode MIC data available for the pathogens isolated during the clinical evaluation of meropenem. These data support the widespread and rapid penetration of meropenem into the interstitial fluid of those tissues not protected by a tight epithelial barrier. Furthermore, they suggest that the proposed dosages of meropenem 500 mg or 1 g tds would provide an adequate duration of cover at tissue sites for the treatment of a range of commonly occurring pathogens. A higher dosage of 40 mg/kg or 2 g in adults given tds would be recommended for meningitis based on the penetration of meropenem into CSF. Overall, the tissue and body fluid data presented confirm the expectation, based on the plasma concentrations and theoretical arguments, that meropenem is rapidly and readily distributed into the interstitial fluid, thereby producing concentrations in tissues likely to be clinically effective. This is consistent with the available clinical data on the therapeutic efficacy of meropenem.

Carbapenems↗

PubMed2004

In vitro and in vivo activity of meropenem and sulbactam against a multidrug-resistant Acinetobacter baumannii strain.

OBJECTIVES: The potential therapeutic role of meropenem combined with sulbactam against a clinical endemic isolate of multidrug-resistant Acinetobacter baumannii, Ab-153, was investigated. METHODS: The antimicrobial susceptibility of Ab-153 to various drugs was studied by the agar dilution method and Etest strips. The antibacterial activity of meropenem and sulbactam were investigated by a time-kill study in vitro and further examined for therapeutic efficacy in vivo in a murine model. RESULTS: In the time-kill study, at a concentration of 0.5 x MIC (4 mg/L) of meropenem, 1 x MIC (8 mg/L) of sulbactam and both in combination, only the combination demonstrated bactericidal effects and there was at least a 5 log(10) reduction in bacterial colony counts after 48 h, compared with either drug alone. BALB/c mice infected with 2.1-2.6 x 10(7) cfu of Ab-153 were treated with 20 mg/kg meropenem every 8 h, 40 mg/kg sulbactam every 8 h or both in combination. The survival rate of mice in the combination group was significantly higher than that in the meropenem-treated or sulbactam-treated group (87% versus 35%, P = 0.0004; 87% versus 30%, P = 0.0002). CONCLUSIONS: Meropenem in conjunction with sulbactam can exhibit more potent antimicrobial activity against Ab-153 than meropenem or sulbactam alone.

Acinetobacter Infections↗

PubMed1992

Pharmacokinetics of meropenem (ICI 194,660) and its metabolite (ICI 213,689) in healthy subjects and in patients with renal impairment.

The pharmacokinetics of meropenem (ICI 194,660) and its open-ring metabolite (ICI 213,689) were studied in 6 healthy volunteers and 16 patients with moderate to severe renal impairment after a single intravenous dose of 500 mg given as a 30-min infusion. Concentrations of unchanged meropenem in plasma and urine were measured by both microbiological and high-pressure liquid chromatographic (HPLC) assays. A good correlation was found between the two techniques. Pharmacokinetic parameters of unchanged meropenem were determined by using the HPLC data. The terminal half-life of unchanged meropenem increased in relation to the degree of renal impairment, being 1.2 h in subjects with normal renal function and 10 h in patients with end-stage renal failure. Total body clearance and renal clearance of unchanged meropenem are linearly related to creatinine clearance. The concentrations of the metabolite in plasma, which are very low in healthy subjects, significantly increased in uremic patients. The apparent half-life of ICI 213,689 increased in uremic patients and was about 35 h in patients with severe renal insufficiency. Meropenem and its metabolite are effectively removed by hemodialysis. The dialysis clearance of the unchanged drug was 81 +/- 22 ml/min. Dosage adjustments of meropenem will be necessary in patients with severe renal impairment.

Adult↗

PubMed1992

Cross-resistance to meropenem, cephems, and quinolones in Pseudomonas aeruginosa.

Multiple-drug-resistant mutants were isolated from Pseudomonas aeruginosa PAO1 on agar plates containing ofloxacin and cefsulodin. These mutants were four to eight times more resistant to meropenem, cephems, carbenicillin, quinolones, tetracycline, and chloramphenicol than the parent strain was. In contrast, these mutants showed no significant changes in their susceptibilities to all carbapenems except meropenem. In these mutants, the amounts of an outer membrane protein with an apparent molecular weight of 49,000 (designated OprM) were increased compared with the amount in PAO1. Multiple-drug-resistant mutants of this type were also isolated from PAO1 on agar plates containing meropenem. Approximately 5% of clinical isolates showed cross-resistance to meropenem, cephems, and quinolones, concomitant with overproduction of OprM. Moreover, these two phenotypes, i.e., multiple-drug resistance and overproduction of OprM, were cotransferable by transduction. These data suggest that overproduction of OprM is associated with cross-resistance to meropenem, cephems, and quinolones in P. aeruginosa. The ofloxacin-cefsulodin-resistant mutant required higher concentrations of meropenem to induce beta-lactamase than PAO1 did, indicating the possibility that this mutation involves decreased outer membrane permeability to meropenem.

Anti-Bacterial Agents↗

PubMed1992

Diffusion of meropenem and imipenem through the outer membrane of Escherichia coli K-12 and correlation with their antibacterial activities.

The outer membrane permeability to meropenem and imipenem in Escherichia coli K-12 was investigated, and its porin-deficient mutants were transformed with a constructed vector carrying the carbapenem-hydrolyzing CphA metallo-beta-lactamase gene. By using the method of Zimmermann and Rosselet, meropenem was shown to penetrate through the outer membrane of E. coli K-12 five times faster than cephaloridine but twice as slowly as imipenem. Lack of one or both porins significantly reduced the penetration of both carbapenems. No evidence of specific porin pathways of the type described in Pseudomonas aeruginosa was found. Despite its slower penetration, meropenem was two to eight times more active than imipenem against both parent and porin-defective mutants, whether harbouring CphA beta-lactamase or not. Meropenem was also more active than imipenem against E. coli DC2, a strain with a breakdown in the outer membrane permeability which made periplasmic concentrations of beta-lactams similar to the external concentrations. In this strain, meropenem caused a more than 50% reduction in cell number increase at a concentration very close to the 50% inhibitory concentration for penicillin-binding protein type 2 (PBP 2), whereas imipenem, at the same concentration, did not significantly inhibit cell growth. This result was explained by the higher affinity of meropenem for PBP 3 compared with imipenem and supports the conclusion that synergistic inhibition of both PBPs was the main mechanism in the better antibacterial activity of meropenem.

Bacteria↗

PubMed1996

Reevaluation of interpretive criteria for Haemophilus influenzae by using meropenem (10-microgram), imipenem (10-microgram), and ampicillin (2- and 10-microgram) disks.

A collection of 300 Haemophilus influenzae clinical strains was used to assess in vitro susceptibility to carbapenems (meropenem, imipenem) by MIC and disk diffusion methods and to compare disk diffusion test results with two potencies of ampicillin disks (2 and 10 micrograms). The isolates included ampicillin-susceptible or- intermediate (167 strains), beta-lactamase-positive (117 strains), and beta-lactamase-negative ampicillin-resistant (BLNAR; 16 strains) organisms. Disk diffusion testing was performed with 10-micrograms meropenem disks from two manufacturers. Meropenem was highly active against H. influenzae strains (MIC50, 0.06 microgram/ml; MIC90, 0.25 microgram/ml; MIC50 and MIC90, MICs at which 50 and 90%, respectively, of strains are inhibited) and was 8- to 16-fold more potent than imipenem (MIC50, 1 microgram/ml; MIC90, 2 micrograms/ml). Five non-imipenem-susceptible strains were identified (MIC, 8 micrograms/ml), but the disk diffusion test indicated susceptibility (zone diameters, 18 to 21 mm). MIC values of meropenem, doxycycline, ceftazidime, and ceftriaxone for BLNAR strains were two- to fourfold greater than those for other strains. The performance of both meropenem disks was comparable and considered acceptable. A single susceptible interpretive zone diameter of > or = 17 mm (MIC, < = or 4 micrograms/ml) was proposed for meropenem. Testing with the 2-micrograms ampicillin disk was preferred because of an excellent correlation between MIC values and zone diameters (r = 0.94) and superior interpretive accuracy with the susceptible criteria at > or = 17 mm (MIC, < or = 1 microgram/ml) and the resistant criteria at < or = 13 mm (MIC, > or = 4 micrograms/ml). Among the BLNAR strains tested, 81.3% were miscategorized as susceptible or intermediate when the 10-micrograms ampicillin disk was used, while the 2-micrograms disk produced only minor interpretive errors (12.5%). Use of these criteria for testing H. influenzae against meropenem and ampicillin should maximize reference test and standardized disk diffusion test performance with the Haemophilus Test Medium. The imipenem disk diffusion test appears compromised and should be used with caution for detecting strains for which imipenem MICs are elevated.

Ampicillin↗

PubMed1991

Antibacterial effects of meropenem and imipenem against Haemophilus influenzae.

Phase contrast microscopy, killing curves and turbidimetric growth curves were used in a comparative study of the antibacterial effects of imipenem and meropenem on Haemophilus influenzae. The minimal inhibitory concentrations (MICs) and their ranges of meropenem and imipenem using five beta-lactamase-producing strains of H. influenzae were 0.03 (0.015-0.06) and 0.6 (0.5-1) micrograms/ml, respectively. Imipenem and meropenem induced spheroplast formation in cultures. Killing curves showed a bacteriostatic activity for meropenem and imipenem for MIC values, and a lag of 2 h in killing for MIC x 2 to MIC x 64. For these concentrations the killing rates of the two antibiotics were similar. Turbidimetric growth curves showed a higher early increase in optical density for meropenem. As far as the MIC value of meropenem was 10 times lower than the MIC value of imipenem, we may conclude that meropenem was more active than imipenem on beta-lactamase-producing strains of H. influenzae.

Colony Count, Microbial↗